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2020-10-26 20:33
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拂拭的反义词-拐杖英文

2020年10月26日发(作者:牛永祥)


Unit 1 Chemical Industry
化学工业







Before reading the text below, try to answer following question:
1. When did the modern chemical industry start?
2. Can you give a definition for the chemical industry?
3. What are the contribution which the chemical industry has made to
meet and satisfy our needs?
4. Is the chemical industry capital- or labor-intensive? Why?
s of the Chemical Industry
Although the use of chemicals dates back to the ancient civilizations, the evolution of what we know as the modern chemical industry
started much more recently. It may be considered to have begun during the Industrial Revolution, about 1800, and developed to provide
chemicals roe use by other industries. Examples are alkali for soapmaking, bleaching powder for cotton, and silica and sodium
carbonate for glassmaking. It will be noted that these are all inorganic chemicals. The organic chemicals industry started in the 1860s
with the exploitation of William Henry Perkin’s discovery if the first synthetic dyestuff—mauve. At the start of the twentieth century the
emphasis on research on the applied aspects of chemistry in Germany had paid off handsomely, and by 1914 had resulted in the German
chemical industry having 75% of the world market in chemicals. This was based on the discovery of new dyestuffs plus the
development of both the contact process for sulphuric acid and the Haber process for ammonia. The later required a major technological
breakthrough that of being able to carry out chemical reactions under conditions of very high pressure for the first time. The experience
gained with this was to stand Germany in good stead, particularly with the rapidly increased demand for nitrogen-based compounds
(ammonium salts for fertilizers and nitric acid for explosives manufacture) with the outbreak of world warⅠin 1914. This initiated
profound changes which continued during the inter-war years (1918-1939).
1. 化学工业的起源
尽管化学品的使用可以追溯到古代文明时 代,我们所谓的现代化学工业的发展却是非常近代(才开始的)。可以认为它起
源于工业革命其间,大约 在1800年,并发展成为为其它工业部门提供化学原料的产业。比如制肥皂所用的碱,棉布生产所用
的 漂白粉,玻璃制造业所用的硅及Na
2
CO
3
. 我们会注意到所有这些都是无机物。有机化学工业的开始是在十九世纪六十年代以
William Henry Perkin 发现第一种合成染料—苯胺紫并加以开发利用为标志的。20世纪初,德国花费大量 资金用于实用化学方
面的重点研究,到1914年,德国的化学工业在世界化学产品市场上占有75%的 份额。这要归因于新染料的发现以及硫酸的接
触法生产和氨的哈伯生产工艺的发展。而后者需要较大的技 术突破使得化学反应第一次可以在非常高的压力条件下进行。这方
面所取得的成绩对德国很有帮助。特别 是由于1914年第一次世界大仗的爆发,对以氮为基础的化合物的需求飞速增长。这种
深刻的改变一直 持续到战后(1918-1939)。
date bake tofrom: 回溯到
dated: 过时的,陈旧的
stand sb. in good stead: 对。。。很有帮助
Since 1940 the chemical industry has grown at a remarkable rate, although this has slowed significantly in recent years. The lion’s
share of this growth has been in the organic chemicals sector due to the development and growth of the petrochemicals area since 1950s.
The explosives growth in petrochemicals in the 1960s and 1970s was largely due to the enormous increase in demand for synthetic
polymers such as polyethylene, polypropylene, nylon, polyesters and epoxy resins.
1940年以来,化学工业一直以引人注目的速度飞速发展。尽管这种发 展的速度近年来已大大减慢。化学工业的发展由于
1950年以来石油化学领域的研究和开发大部分在有 机化学方面取得。石油化工在60年代和70年代的迅猛发展主要是由于人们
对于合成高聚物如聚乙烯、 聚丙烯、尼龙、聚脂和环氧树脂的需求巨大增加。

The chemical industry today is a very diverse sector of manufacturing industry, within which it plays a central role. It makes
thousands of different chemicals which the general public only usually encounter as end or consumer products. These products are
purchased because they have the required properties which make them suitable for some particular application, e.g. a non-stick coating
for pans or a weedkiller. Thus chemicals are ultimately sold for the effects that they produce.
今天的化学工业已经是制造业中有着许多分支的部门,并且在制造业中 起着核心的作用。它生产了数千种不同的化学产


品,而人们通常只接触到终端产品或消费 品。这些产品被购买是因为他们具有某些性质适合(人们)的一些特别的用途,例如,
用于盆的不粘涂层 或一种杀虫剂。这些化学产品归根到底是由于它们能产生的作用而被购买的。

2. Definition of the Chemical Industry
At the turn of the century there would have been little difficulty in defining what constituted the chemical industry since only a
very limited range of products was manufactured and these were clearly chemicals, e.g., alkali, sulphuric acid. At present, however,
many intermediates to products produced, from raw materials like crude oil through (in some cases) many intermediates to products
which may be used directly as consumer goods, or readily converted into them. The difficulty cones in deciding at which point in this
sequence the particular operation ceases to be part of the chemical industry’s sphere of activities. To consider a specific example to
illustrate this dilemma, emulsion paints may contain poly (vinyl chloride) poly (vinyl acetate). Clearly, synthesis of vinyl chloride (or
acetate) and its polymerization are chemical activities. However, if formulation and mixing of the paint, including the polymer, is carried
out by a branch of the multinational chemical company which manufactured the ingredients, is this still part of the chemical industry of
does it mow belong in the decorating industry?
2. 化学工业的定义
在本世纪初,要定义什么是化学工业是不太困难的,因为那时所生产的 化学品是很有限的,而且是非常清楚的化学品,
例如,烧碱,硫酸。然而现在有数千种化学产品被生产, 从一些原料物质像用于制备许多的半成品的石油,到可以直接作为消
费品或很容易转化为消费品的商品。 困难在于如何决定在一些特殊的生产过程中哪一个环节不再属于化学工业的活动范畴。举
一个特殊的例子 来描述一下这种困境。乳剂漆含有聚氯乙烯聚醋酸乙烯。显然,氯乙烯(或醋酸乙烯)的合成以及聚合是化
学活动。然而,如果这种漆,包括高聚物,它的配制和混合是由一家制造配料的跨国化学公司完成的话,那它仍 然是属于化学
工业呢还是应当归属于装饰工业中去呢?
It is therefore apparent that, because of its diversity of operations and close links in many areas with other industries, there is no
simple definition of the chemical industry. Instead each official body which collects and publishes statistics on manufacturing industry
will have its definition as to which operations are classified as the chemical industry. It is important to bear this in mind when comparing
statistical information which is derived from several sources.
因此,很明显,由于化学工业经营的种类很多并在很多领域与其 它工业有密切的联系,所以不能对它下一个简单的定义。
相反的每一个收集和出版制造工业统计数据的官 方机构都会对如何届定哪一类操作为化学工业有自己的定义。当比较来自不同
途径的统计资料时,记住这 点是很重要的。

3. The Need for Chemical Industry
The chemical industry is concerned with converting raw materials, such as crude oil, firstly into chemical intermediates and then
into a tremendous variety of other chemicals. These are then used to produce consumer products, which make our lives more
comfortable or, in some cases such as pharmaceutical produces, help to maintain our well-being or even life itself. At each stage of these
operations value is added to the produce and provided this added exceeds the raw material plus processing costs then a profit will be
made on the operation. It is the aim of chemical industry to achieve this.
3. 对化学工业的需要
化学工业涉及到原材料的转化,如石油 首先转化为化学中间体,然后转化为数量众 多的其它化学产品。这些产品再被用
来生产消费品,这些消费品可以使我们的生活更为舒适或者作药物维 持人类的健康或生命。在生产过程的每一个阶段,都有价
值加到产品上面,只要这些附加的价值超过原材 料和加工成本之和,这个加工就产生了利润。而这正是化学工业要达到的目的。

It may seem strange in textbook this one to pose the question “do we need a chemical industry?” However trying to answer this
question will provide(ⅰ) an indication of the range of the chemical industry’s activities, (ⅱ) its influence on our lives in everyday
terms, and (ⅲ) how great is society’s need for a chemical industry. Our approach in answering the question will be to consider the
industry’s contribution to meeting and satisfying our major needs. What are these? Clearly food (and drink) and health are paramount.
Other which we shall consider in their turn are clothing and (briefly) shelter, leisure and transport.
在这样的一本教科书中提出:“我们需要化学工业吗 ?”这样一个问题是不是有点奇怪呢?然而,先回答下面几个问题将
给我们提供一些信息:(1)化学工 业的活动范围,(2)化学工业对我们日常生活的影响,(3)社会对化学工业的需求有多大。
在回答这 些问题的时候我们的思路将要考虑化学工业在满足和改善我们的主要需求方面所做的贡献。是些什么需求呢?很显


然,食物和健康是放在第一位的。其它我们要考虑的按顺序是衣物、住所、休闲和旅行。

(1) Food. The chemical industry makes a major contribution to food production in at least three ways. Firstly, by making available
large quantities of artificial fertilizers which are used to replace the elements (mainly nitrogen, phosphorus and potassium) which are
removed as nutrients by the growing crops during modern intensive farming. Secondly, by manufacturing crop protection chemicals, i.e.,
pesticides, which markedly reduce the proportion of the crops consumed by pests. Thirdly, by producing veterinary products which
protect livestock from disease or cure their infections.
(1)食物。化 学工业对粮食生产所做的巨大贡献至少有三个方面。第一,提供大量可以获得的肥料以补充由于密集耕作被
农作物生长时所带走的营养成分。(主要是氮、磷和钾)。第二,生产农作物保护产品,如杀虫剂,它可以显著 减少害虫所消耗
的粮食数量。第三,生产兽药保护家禽免遭疾病或其它感染的侵害。

(2) Health. We are all aware of the major contribution which the pharmaceutical sector of the industry has made to help keep us all
healthy, e.g. by curing bacterial infections with antibiotics, and even extending life itself, e.g. ?–blockers to lower blood pressure.
(2)健康 。我们都很了解化学工业中制药这一块在维护我们的身体健康甚至延长寿命方面所做出的巨大贡献,例如,用抗生素治疗细菌感染,用β-抗血栓降低血压。

(3) Clothing. The improvement in properties of modern synthetic fibers over the traditional clothing materials (e.g. cotton and
wool) has been quite remarkable. Thus shirts, dresses and suits made from polyesters like Terylene and polyamides like Nylon are
crease-resistant, machine-washable, and drip-dry or non-iron. They are also cheaper than natural materials.
衣物。在传统的衣服面料上,现代合成纤维性质的 改善也是非常显著的。用聚脂如涤纶或聚酰胺如尼龙所制作的T恤、
上衣、衬衫抗皱、可机洗,晒干自挺 或免烫,也比天然面料便宜。

Parallel developments in the discovery of modern synthetic dyes and the technology to “bond” them to the fiber has resulted in a
tremendous increase in the variety of colors available to the fashion designer. Indeed they now span almost every color and hue of the
visible spectrum. Indeed if a suitable shade is not available, structural modification of an existing dye to achieve this can readily be
carried out, provided there is a satisfactory market for the product.
与此同时,现代 合成染料开发和染色技术的改善使得时装设计师们有大量的色彩可以利用。的确他们几乎利用了可见光
谱 中所有的色调和色素。事实上如果某种颜色没有现成的,只要这种产品确有市场,就可以很容易地通过对现有的色 彩进行结
构调整而获得。

Other major advances in this sphere have been in color-fastness, i.e., resistance to the dye being washed out when the garment is
cleaned.
这一领域中另一些重要进展是不褪色,即在洗涤衣物时染料不会被洗掉。

(4) Shelter, leisure and transport. In terms of shelter the contribution of modern synthetic polymers has been substantial. Plastics
are tending to replace traditional building materials like wood because they are lighter, maintenance- free (i.e. they are resistant to
weathering and do not need painting). Other polymers, e.g. urea-formaldehyde and polyurethanes, are important insulating materials for
reducing heat losses and hence reducing energy usage.
(4)住所,休闲和旅游。讲 到住所方面现代合成高聚物的贡献是巨大的。塑料正在取代像木材一类的传统建筑材料,因
为它们更轻, 免维护(即它们可以抵抗风化,不需油漆)。另一些高聚物,比如,脲甲醛和聚脲,是非常重要的绝缘材料可以< br>减少热量损失因而减少能量损耗。

Plastics and polymers have made a considerable impact on leisure activities with applications ranging from all- weather artificial
surfaces for athletic tracks, football pitches and tennis courts to nylon strings for racquets and items like golf balls and footballs made
entirely from synthetic materials.
塑料和高聚物的应用对休闲活动有很重要的影响,从体育 跑道的全天候人造篷顶,足球和网球的经纬线,到球拍的尼龙
线还有高尔夫球的元件,还有制造足球的合 成材料。



Likewise the chemical industry’s contribution to transport over the years has led to major improvements. Thus development of
improved additives like anti- oxidants and viscosity index improves for engine oil has enabled routine servicing intervals to increase
from 3000 to 6000 to 12000 miles. Research and development work has also resulted in improved lubricating oils and greases, and
better brake fluids. Yet again the contribution of polymers and plastics has been very striking with the proportion of the total automobile
derived from these materials—dashboard, steering wheel, seat padding and covering etc.—now exceeding 40%.
多年来化学工业对旅 游方面所作的贡献也有很大的提高。一些添加剂如抗氧化剂的开发和发动机油粘度指数改进使汽车
日产维 修期限从3000英里延长到6000英里再到12000英里。研发工作还改进了润滑油和油脂的性能,并得到 了更好的刹车油。
塑料和高聚物对整个汽车业的贡献的比例是惊人的,源于这些材料—挡板,轮胎,坐垫 和涂层等等—超过40%。

So it is quite apparent even from a brief look at the chemical industry’s contribution to meeting our major needs that life in the
world would be very different without the products of the industry. Indeed the level of a country’s development may be judged by the
production level and sophistication of its chemical industry.
很显然简单地看一下化学工业在满足我们的主要需求方面所做 的贡献就可以知道,没有化工产品人类社会的生活将会多
么困难。事实上,一个国家的发展水平可以通过 其化学工业的生产水平和精细程度来加以判断。

4. Research and Development (R&D) in Chemical Industries
One of the main reasons for the rapid growth of the chemical industry in the developed world has been its great commitment to,
and investment in research and development (R&D). A typical figure is 5% of sales income, with this figure being almost doubled for
the most research intensive sector, pharmaceuticals. It is important to emphasize that we are quoting percentages here not of profits but
of sales income, i.e. the total money received, which has to pay for raw materials, overheads, staff salaries, etc. as well. In the past this
tremendous investment has paid off well, leading to many useful and valuable products being introduced to the market. Examples
include synthetic polymers like nylons and polyesters, and drugs and pesticides. Although the number of new products introduced to the
market has declined significantly in recent years, and in times of recession the research department is usually one of the first to suffer
cutbacks, the commitment to R&D remains at a very high level.
4. 化学工业的研究和开发。
发达国家化 学工业飞速发展的一个重要原因就是它在研究和开发方面的投入和投资。通常是销售收入的5%,而研究密集型分支如制药,投入则加倍。要强调这里我们所提出的百分数不是指利润而是指销售收入,也就是说全部回收 的钱,其中包括
要付出原材料费,企业管理费,员工工资等等。过去这笔巨大的投资支付得很好,使得许 多有用的和有价值的产品被投放市场,
包括一些合成高聚物如尼龙和聚脂,药品和杀虫剂。尽管近年来进 入市场的新产品大为减少,而且在衰退时期研究部门通常是
最先被裁减的部门,在研究和开发方面的投资 仍然保持在较高的水平。

The chemical industry is a very high technology industry which takes full advantage of the latest advances in electronics and
engineering. Computers are very widely used for all sorts of applications, from automatic control of chemical plants, to molecular
modeling of structures of new compounds, to the control of analytical instruments in the laboratory.
化学工业是高技术工业,它需要利用电子学和工程学的最新成果。计算机被广 泛应用,从化工厂的自动控制,到新化合
物结构的分子模拟,再到实验室分析仪器的控制。

Individual manufacturing plants have capacities ranging from just a few tones per year in the fine chemicals area to the real giants
in the fertilizer and petrochemical sectors which range up to 500,000 tonnes. The latter requires enormous capital investment, since a
single plant of this size can now cost $$520 million! This, coupled with the widespread use of automatic control equipment, helps to
explain why the chemical industry is capital-rather than labor-intensive.
一个制造厂的生产量很不一样,精细化工领域每年只有几吨,而巨 型企业如化肥厂和石油化工厂有可能高达500,000吨。
后者需要巨大的资金投入,因为一个这样规 模的工厂要花费2亿5千万美元,再加上自动控制设备的普遍应用,就不难解释为
什么化工厂是资金密集 型企业而不是劳动力密集型企业。

The major chemical companies are truly multinational and operate their sales and marketing activities in most of the countries of


the world, and they also have manufacturing units in a number of countries. This international outlook for operations, or globalization, is
a growing trend within the chemical industry, with companies expanding their activities either by erecting manufacturing units in other
countries or by taking over companies which are already operating there.
大部分化学公司是真正的跨国公司,他们在世界上的许多国家进行销售和开发市场,他们 在许多国家都有制造厂。这种
国际间的合作理念,或全球一体化,是化学工业中发展的趋势。大公司通过 在别的国家建造制造厂或者是收购已有的工厂进行
扩张。














Unit 2 Research and Development
研究和开发
Research and development, or R&D as it is commonly referred to, is an activity which is carried out by all sectors of
manufacturing industry but its extent varies considerably, as we will see shortly. Let us first understand, or at least get a feel for, what
the terms mean. Although the distinction between research and development is not always clear-cut, and there is often considerable
overlap, we will attempt to separate them. In simple terms research can be thought of as the activity which produces new ideas and
knowledge whereas development is putting those ideas into practice as new process and products. To illustrate this with an example,
predicting the structure of a new molecule which would have a specific biological activity and synthesizing it could be seen as
research whereas testing it and developing it to the point where it could be marketed as a new drug could be described as the
development part.
研究和开发,或 通常所称R&D是制造业各个部门都要进行的一项活动。我们马上可以看到,它的内容变化很大。我们
首 先了解或先感觉一下这个词的含义。尽管研究和开发的定义总是分得不很清楚,而且有许多重叠的部分,我们还是 要试着
把它们区分开来。简单说来,研究是产生新思想和新知识的活动,而开发则是把这些思想贯彻到实 践中得到新工艺和新产品
的行为。可以用一个例子来描述这一点,预测一个有特殊生物活性的分子结构并 合成它可以看成是研究而测试它并把它发展
到可以作为一种新药推向市场这一阶段则看作开发部分。

1. Fundamental Research and Applied Research
In industry the primary reason for carting out R&D is economic and is to strengthen and improve the company’s position and
profitability. The purpose of R&D is to generate and provide information and knowledge to reduce uncertainty, solve problems and to
provide better data on which management can base decisions. Specific projects cover a wide range of activities and time scales, from
a few months to 20 years.
1. 基础研究和应用研究
在工业上进 行研究和开发最主要的原因是经济利益方面,是为了加强公司的地位,提高公司的利润。R&D的目的是做
出并提供信息和知识以减低不确定性,解决问题,以及向管理层提供更好的数据以便他们能据此做出决定。特别 的项目涵盖很
大的活动范围和时间范围,从几个月到20年。

We can pick out a number of areas of R&D activity in the following paragraphs but if we were to start with those which were to


spring to the mind of the academic, rather than the industrial, chemist then these would be basic, fundamental (background) or
exploratory research and the synthesis of new compounds. This is also labeled “blue skies” research.
我们可以在后面的段落里举出大量的R&D活动。但 是如果我们举出的点子来源于研究院而不是工业化学家的头脑,这
就是基础的或探索性的研究

Fundamental research is typically associated with university research. It may be carried out for its own intrinsic interest and it
will add to the total knowledge base but no immediate applications of it in the “real world” well be apparent. Note that it will provide
a valuable training in defining and solving problems, i.e. research methodology for the research student who carries it out under
supervision. However, later “spin offs” from such work can lead to useful applications. Thus physicists claim that but for the study
and development of quantum theory we might not have had computers and nuclear power. However, to take a specifically chemical
example, general studies on a broad area such as hydrocarbon oxidation might provide information which would be useful in more
specific areas such as cyclohexane oxidation for the production of nylon intermediates.
基础研究通常与大学研究联系在一起,它可能是由 于对其内在的兴趣而进行研究并且这种研究能够拓宽知识范围,
但在现实世界中的直接应用可能性是很小 的。请注意,这种以内就在提出和解决问题方面提供了极有价值的训练,比如,在指
导下完成研究工作的 学生所接受的研究方法学(的训练)。而且,从这些工作中产生的“有用的副产品”随后也能带来可观的
使用价值。因此,物理学家宣称要不是量子理论的研究和发展我们可能仍然没有计算机和核能量。不管怎样,举一 个特殊的化
学方面的例子吧,在各个领域如烃的氧化方面所做的广泛的研究将为一些特殊的领域如环己烯 氧化生成尼龙中间产物提供有用
的信息。

Aspects of synthesis could involve either developing new, more specific reagents for controlling particular functional group
interconversions, i.e. developing synthetic methodology or complete synthesis of an entirely new molecule which is biologically
active. Although the former is clearly fundamental the latter encompasses both this and applied aspects. This term ‘applied’ has
traditionally been more associated with research out in industrial laboratories, since this is more focused or targeted. It is a
consequence of the work being business driven.
通过合成可以生产出一些新的、更特殊的试剂以控制特殊的官能团转换,即发展合成方法或完成一些具有 生物活性
的新分子的合成。尽管前者显然属于基础性研究而后者则包括基础研究和实用性研究两部分。所 谓“实用性”习惯上是指与在
工业实验室完成的研究联系在一起的,因为它更具目的性,它是商业行为驱 动的结果。

Note, however, that there has been a major change in recent years as academic institutions have increasingly turned to industry
for research funding, with the result that much more of their research effort is mow devoted to more applied research. Even so, in
academia the emphasis generally is very much on the research rather than the development.
然而,请注意。近 几年有很大的变化,大学研究机构正越来越多地转向工业界寻求研究经费,其结果就是他们的研究
工作越 来越多地是致力于实用研究。即使这样,学院工作的重点通常还是在于研究而不是开发。

2. Types of Industrial Research and Development
The applied or more targeted type of research and development commonly carried out in industry can be of several types and
we will briefly consider each. They are: (ⅰ)product development, (ⅱ) process development, (ⅲ) process improvement and (ⅳ)
applications development. Even under these headings there are a multitude of aspects so only a typical example can be quoted in each
case. The emphasis on each of these will vary considerably within the different sectors of the chemical industry.
2.工业研究和开发的类型
通常在生产中 完成的实用型的或有目的性的研究和开发可以分为好几类,我们对此加以简述。它们是:(1)产品开
发 ;(2)工艺开发;(3)工艺改进;(4)应用开发;每一类下还有许多分支。我们.对每一类举一个典型的例 子来加以说明。在
化学工业的不同部门内每类的工作重点有很大的不同。

(1)Product development. Product development includes not only the discovery and development of a new drug but also, for
example, providing a new longer-active anti-oxidant additive to an automobile engine oil. Development such as this have enabled
servicing intervals to increase during the last decade from 3000 to 6000 to 9000 and now to 12000 miles. Note that most purchasers of


chemicals acquire them for the effects that they produce i.e. a specific use. Teflon, or polytetrafluoroethylene (PTFE), may be purchased
because it imparts a non-stick surface to cooking pots and pans, thereby making them easier to clean.
(1)产品开发。产品开发不仅包括一种新药的发明和 生产,还包括,比如说,给一种汽车发动机提供更长时效的抗氧化添
加剂。这种开发的产品已经使(发动 机)的服务期限在最近的十年中从3000英里提高到6000、9000现在已提高到12000英里。
请注意,大部分的买家所需要的是化工产品能创造出来的效果,亦即某种特殊的用途。Tdflon,或称聚四 氟乙烯(PTFE)被购
买是因为它能使炒菜锅、盆表面不粘,易于清洗。

(2) Process development. Process development covers not only developing a manufacturing process for an entirely new product
but also a new process or route for an existing product. The push for the latter may originate for one or more of the following reasons:
availability of new technology, change in the availability andor cost of raw materials. Manufacture of vinyl chloride monomer is an
example of this. Its manufacturing route has changed several times owing to changing economics, technology and raw materials.
Another stimulus is a marked increase in demand and hence sales volume which can have a major effect on the economics of the process.
The early days of penicillin manufacture afford a good example of this.
(2) 工艺开发。工业开发不仅包括为一种全新的产品设计一套制造工艺,还包括为现有的产品设计新的工艺或方案。而 要
进行后者时可能源于下面的一个或几个原因:新技术的利用、原材料的获得或价格发生了变化。氯乙烯 单聚物的制造就是这样
的一个例子。它的制造方法随着经济、技术和原材料的变化改变了好几次。另一个 刺激因素是需求的显著增加。因而销售量对
生产流程的经济效益有很大影响。Penicillin早期 的制造就为此提供了一个很好的例子。

The ability of penicillin to prevent the onset of septicemia in battle wounds during the Second World War (1939~1945) resulted
in an enormous demand for it to be produced in quantity. Up until then it had only been produced in small amounts on the surface of the
fermentation broth in milk bottles! An enormous R&D effort jointly in the U.S. and the U.K. resulted in two major improvements to the
process. Firstly a different stain of the mould gave much better yields than the original Penicillium notatum. Secondly the major process
development was the introduction of the deep submerged fermentation process. Here the fermentation takes place throughout the broth,
provided sterile air is constantly, and vigorously, blown through it. This has enabled the process to be scaled up enormously to modern
stainless steel fermenters having a capacity in excess of 50000 liters. It is salutary to note that in the first world war (1914~1919) more
soldiers died from septicemia of their wounds than were actually killed outright on the battlefield!
Penicillin能预防战争中因伤口感染引发的败血症,因而在第二 次世界大战(1939-1945)中,penicillin的需求量非常大,
需要大量生产。而在那 时,penicillin只能用在瓶装牛奶表面发酵的方法小量的生产。英国和美国投入了巨大的人力物力联合 进
行研制和开发,对生产流程做出了两个重大的改进。首先用一个不同的菌株—黄霉菌代替普通的青霉, 它的产量要比后者高得
多。第二个重大的流程开发是引进了深层发酵过程。只要在培养液中持续通入大量 纯化空气,发酵就能在所有部位进行。这使
生产能力大大地增加,达到现代容量超过5000升的不锈钢 发酵器。而在第一次世界大战中,死于伤口感染的士兵比直接死于
战场上的人还要多。注意到这一点不能 不让我们心存感激。

Process development for a new product depends on things such as the scale on which it is to be manufactured, the by-products
formed and their removalrecovery, and required purity. Data will be acquired during this development stage using semi-technical plant
(up to 100 liters capacity) which will be invaluable in the design of the actual manufacturing plant. If the plant is to be a very large
capacity, continuously operating one, e.g. petrochemical or ammonia, then a pilot plant will first be built and operated to test out the
process and acquire more data, these semi- technical or pilot plants will be required for testing, e.g., a pesticide, or customer evaluation,
e.g., a new polymer.
对一个新产品进行开 发要考虑产品生产的规模、产生的副产品以及分离回收,产品所要求的纯度。在开发阶段利用中试
车间( 最大容量可达100升)获得的数据设计实际的制造厂是非常宝贵的,例如石油化工或氨的生产。要先建立一个中 试车间,
运转并测试流程以获得更多的数据。他们需要测试产品的性质,如杀虫剂,或进行消费评估,如 一种新的聚合物。

Note that by-products can has a major influence on the economics of a chemical process. Phenol manufacture provides a striking
example of this. The original route, the benzenesulphonic acid route, has become obsolete because demand for its by-produce sodium
sulfite (2.2 tonsl ton phenol) has dried up. Its recovery and disposal will therefore be an additional charge on the process, thus
increasing the cost of the phenol. In contrast the cumene route owes its economic advantage over all the other routes to the strong


demand for the by-product acetone (0.6 tonsl ton phenol).The sale of this therefore reduces the net cost of the phenol.
注意,副产品对于化学 过程的经济效益也有很大的影响。酚的生产就是一个有代表性的例子。早期的方法,苯磺酸方法,
由于它 的副产品亚硫酸钠需求枯竭而变的过时。亚硫酸钠需回收和废置成为生产过程附加的费用,增加了生产酚的成本。 相反,
异丙基苯方法,在经济效益方面优于所有其他方法就在于市场对于它的副产品丙酮的迫切需求。丙 酮的销售所得降低了酚的生
产成本。

A major part of the process development activity for a mew plant is to minimize, or ideally prevent by designing out, waste
production and hence possible pollution. The economic and environmental advantages of this are obvious.
对一个新产品进行工艺开发的一个重要部分是通过设计把废品减到最低,或 尽可能地防止可能的污染,这样做带来的经
济利益和对环境的益处是显而易见的。

Finally it should be noted that process development requires a big team effort between chemists, chemical engineers, and electrical
and mechanical engineers to be successful.
最后要注意,工业开发需要包括化学家、化学工程师、电子和机械工程师这样一支庞大队伍的协同合作才能取得 成功。
(3) Process improvement. Process improvement relates to processes which are already operating. It may be a problem that has
arisen and stopped production. In this situation there is a lot of pressure to find a solution as soon as possible so that production can
restart, since ‘down time’ costs money.
(3)工艺改进。工艺改进与正在进行的工艺有 关。它可能出现了某个问题使生产停止。在这种情形下,就面临着很大的
压力要尽快地解决问题以便生产 重新开始,因为故障期耗费资财。
down time: 故障期

More commonly, however, process improvement will be directed at improving the profitability of the process. This might be
achieved in a number of ways. For example, improving the yield by optimizing the process, increasing the capacity by introducing a
new catalyst, or lowering the energy requirements of the process. An example of the latter was the introduction of turbo compressors in
the production of ammonia by the Haber process. This reduced utility costs (mainly electricity) from $$6.66 to %0.56 per ton of ammonia
produced. Improving the quality of the product, by process modification, may lead to new markets for the product.
然而,更为常见的,工艺改进是为了提 高生产过程的利润。这可以通过很多途径实现。例如通过优化流程提高产量,引
进新的催化剂提高效能, 或降低生产过程所需要的能量。可说明后者的一个例子是在生产氨的过程中涡轮压缩机的引进。这使
生产 氨的成本(主要是电)从每吨6.66美元下降到0.56美元。通过工艺的改善提高产品质量也会为产品打开新 的市场。

In recent years, however, the most important process improvement activity has been to reduce the environmental impact of the
process, i.e., to prevent the process causing any pollution. Clearly there have been two interlinked driving forces for this. Firstly, the
public’s concern about the safety of chemicals and their effect on the environment, and the legislation which has followed as a result of
this. Secondly the cost to the manufacturer of having to treat waste (i.e., material which cannot be recovered and used r sold) so that it
can be safely disposed of, say by pumping into a river. This obviously represents a charge on the process which will increase the cost of
the chemical being made. The potential for improvement by reducing the amount of waste is self-evident. < br>然而,近年来,最重要的工艺改进行为主要是减少生产过程对环境的影响,亦即防止生产过程所引起的污染 。很明显,
有两个相关连的因素推动这样做。第一,公众对化学产品的安全性及其对环境所产生影响的关 注以及由此而制订出来的法律;
第二,生产者必须花钱对废物进行处理以便它能安全地清除,比如说,排 放到河水中。显然这是生产过程的又一笔费用,它将
增加所生产化学产品的成本。通过减少废物数量提高 效益其潜能是不言而喻的。

Note, however, with a plant which has already been built and is operating there are usually only very limited physical changes
which can be made to the plant to achieve the above aims. Hence the importance, already mentioned, of eliminating waste production at
the design stage of a new plant. Conserving energy and thus reducing energy cost has been another major preoccupation in recent years.
然 而,请注意,对于一个已经建好并正在运行的工厂来说,只能做一些有限的改变来达到上述目的。因此,上面所提 到
的减少废品的重要性应在新公厂的设计阶段加以考虑。近年来另一个当务之急是保护能源及降低能源消 耗。


(4) Applications development. Clearly the discovery of new applications or uses for a product can increase or prolong its
profitability. Not only does this generate more income but the resulting increased scale of production can lead to lower unit costs and
increased profit. An example is PVC whose early uses included records and plastic raincoats. Applications which came later included
plastic bags and particularly engineering uses in pipes and guttering.
(4)应用开发。显然发掘一个产品新的用处或新的用途能拓宽它的 获利渠道。这不仅能创造更多的收入,而且由于产量
的增加使单元生产成本降低,从而使利润提高。举例 来说,PVC早期是用来制造唱片和塑料雨衣的,后来的用途扩展到塑料薄
膜,特别是工程上所使用的管 子和排水槽。

Emphasis has already been placed on the fact that chemicals are usually purchased for the effect, or particular use, or application
which they have. This often means that there will be close liaison between the chemical companies’ technical sales representatives and
the customer, and the level of technical support for the customer can be a major factor in winning sales. Research and development
chemists provide the support for these applications developments. An example is CF3CH3F. This is the first of the CFC replacements
and has been developed as a extracting natural products from plant materials. In no way was this envisaged when the compound was
first being made for use as a refrigerant gas, but it clearly is an example of applications development.
我们已 经强调了化学产品是由于它们的效果,或特殊的用途、用处而得以售出这个事实。这就意味着化工产品公司的技< br>术销售代表与顾客之间应有密切的联系。对顾客的技术支持水平往往是赢得销售的一个重要的因素。进行研 究和开发的化学家
们为这些应用开发提供了帮助。CH
3
CH
3
F的 制造就是一个例子。它最开始是用来做含氟氯烃的替代物作冷冻剂的。然而近来发
现它还可以用作从植物 中萃取出来的天然物质的溶解剂。当它作为制冷剂被制造时,固然没有预计到这一点,但它显然也是应
用 开发的一个例子。

ions in R&D Activities across the Chemical Industry
Both the nature and amount of R&D carried out varies significantly across the various sectors of the chemical industry. In sectors
which involve largescale production of basic chemicals and where the chemistry, products and technology change only slowly because
the process are mature, R&D expenditure is at the lower end of the range for the chemical industry. Most of this will be devoted to
process improvement and effluent treatment. Examples include ammonia, fertilizers and chloralkali production from the inorganic side,
and basic petrochemical intermediates such a ethylene from the organic side.
3.化工行业中研究与开发活动的变化
化学工业的不同部门所进行的R&D的性质与数量都有 很大的变化。与大规模生产的基础化工产品有关的部门中,化学产
品和技术变化都很慢,因为流程已很成 熟。R&D经费支出属于化工行业中低的一端,而且大部分的费用是用于过程改进和废
水处理。无机方面 的例子有氨、肥料和氯碱的生产,有机方面的如乙烯等一些基础石油化学的中间产物。

At the other end of the scale lie pharmaceuticals and pesticides (or plant protection products). Here there are immense and
continuous efforts to synthesize new molecules which exert the desired, specific biological effect. A single company may generate
10,000 new compounds for screening each year. Little wonder that some individual pharmaceutical company’s annual R&D expenditure
is now approaching $$1000 million! Expressing this in a different way they spend in excess of 14% of sales income (note not profits) on
R&D.
不一样规模生产的是药品和除草剂。人们付出了巨大而持续的努力以合成能产生所希望的、特殊的生物作 用的新分子。
一家公司每年可能要合成10,000新化合物以供筛选。可以想象一些医药公司其每年的 R&D经费支出高达100亿美元。换句话
说,他们把超过14%的销售收入投入在R&D上。





































Unit 3 Typical Activities of Chemical Engineers
化学工程师的例行工作
The classical role of the chemical engineer is to take the discoveries made by the chemist in the laboratory and develop them into
money--making, commercial-scale chemical processes. The chemist works in test tubes and Parr bombs with very small quantities of
reactants and products (e.g., 100 ml), usually running “batch”, constant-temperature experiments. Reactants are placed in a small
container in a constant temperature bath. A catalyst is added and the reactions proceed with time. Samples are taken at appropriate
intervals to follow the consumption of the reactants and the production of products as time progresses.
化学工程师经典的角色是把化学家在实 验室里的发现拿来并发展成为能赚钱的、商业规模的化学过程。化学家用少量的
反应物在试管和派式氧弹 中反应相应得到少量的生成物,所进行的通常是间歇性的恒温下的实验,反应物放在很小的置于恒温
水槽 的容器中,加点催化剂,反应继续进行,随时间推移,反应物被消耗,并有生成物产生,产物在合适的间歇时间获 得。

By contrast, the chemical engineer typically works with much larger quantities of material and with very large (and expensive)
equipment. Reactors can hold 1,000 gallons to 10,000 gallons or more. Distillation columns can be over 100 feet high and 10 to 30 feet
in diameter. The capital investment for one process unit in a chemical plant may exceed $$100 million!
与之相比,化学工程师通常面对的是数量多得多的物质和庞大的(昂贵的)设备。反应器可以容纳100 0 到10,000加仑
甚至更多。蒸馏塔有100英尺多高,直径10到30英尺。化工厂一个单元流 程的投资可能超过1亿美元。

The chemical engineer is often involved in “scaling up” a chemist-developed small-scale reactor and separation system to a very


large commercial plant. The chemical engineer must work closely with the chemist in order to understand thoroughly the chemistry
involved in the process and to make sure that the chemist gets the reaction kinetic data and the physical property data needed to design,
operate, and optimize the process. This is why the chemical engineering curriculum contains so many chemistry courses.
在把化学家研制的小型 反应器及分离系统“放大”到很大的商业化车间时,通常需要化学工程师的参与。为了彻底了解
过程中的 化学反应,化学工程师必须与化学家密切合作以确保能得到所需要的反应的动力学性质和物理性质参数以进行设计 、
运转和优选流程。这就是为什么化工课程要包括那么多的化学类课程的原因。

The chemical engineer must also work closely with mechanical, electrical, civil, and metallurgical engineers in order to design and
operate the physical equipment in a plant--the reactors, tanks, distillation columns, heat exchangers, pumps, compressors, Control and
instrumentation devices, and so on. One big item that is always on such an equipment list is piping. One of the most impressive features
f a typical chemical plant is the tremendous number of pipes running all over the site, literally hundreds of miles in many plants. These
pipes transfer process materials (gases and liquids) into and out of the plant. They also carry utilities (steam, cooling water, air, nitrogen,
and refrigerant) to the process units.
化学工 程师还必须与机械、电子、土木建筑和冶金工程师密切协作以设计和操作工厂的机械设备—反应器、槽、蒸馏塔、
热交换器、泵、压缩机、控制器和仪器设备等等。在这张设备单上还有一大类是管子。化工厂最典型的特 征之一就是数目庞大
的管道贯穿所有生产间。可以毫不夸张地说,在许多车间都有几百英里长的管道。这 些管道输入和输出车间的反应物质进行传
递,同时还可携带有用的东西(水蒸气、冷却水、空气、氧、冷 却剂)进入操作单元。

To commercialize the laboratory chemistry, the chemical engineer is involved in development, design, construction, operation,
sales, and research. The terminology used to label these functions is by no means uniform from company to company, but a rose by any
other name is still a rose. Let us describe each of these functions briefly. It should be emphasized that the jobs we shall discuss are
“typical” and “classical”, but are by no means the only things that chemical engineers do. The chemical engineer has a broad
background in mathematics, chemistry, and physics. Therefore, he or she can, and does, fill a rich variety of jobs in industry,
government, and academia.
要把实验室研究商业化,化学工程师 要参与进行开发、设计、建筑、操作、销售和研究工作。各个公司用来表示这些工
作的名词不完全一样, 但万变不离其宗。让我们简单地把每个工作描述一下。应该强调的是,我们所讨论的工作是“典型的”
和 “经典的”,但并不意味着化学工程师只能做这些事。化学工程师在数学、化学和物理学方面都有很好的知识基础 ,因此,
他或她能够而且确实适应工业、政府部门、大专院校等非常广泛的职业要求。

1. Development
Development is the intermediate step required in passing from a laboratory-size process to a commercial-size process. The
“pilot-plant” process involved in development might involve reactors that are five gallons in capacity and distillation columns that are
three inches in diameter. Development is usually part of the commercialization of a chemical process because the scale-up problem is a
very difficult one. Jumping directly from test tubes to 10,000-gallon reactors can be a tricky and sometimes dangerous endeavor. Some
of the subtle problems involved which are not at all obvious to the uninitiated include mixing imperfections, increasing radial
temperature gradients, and decreasing ratios of heat transfer areas to heat generation rates.
1. 开发
开发工作 是从实验室规模向商业化规模转化所必需的中间阶段。开发阶段所涉及的“中试”流程所使用的反应器容量为5< br>加仑,蒸馏塔直径为3英寸。开发通常是化学流程商业化的一部分。因为“放大”规模是一个非常困难的问 题。直接从试管研
制跳到在10.000加仑反应器里生产是非常棘手的有时甚至是危险的工作。一些( 在实验室研究阶段)根本不明显的未加以考虑
的细微问题,如混合不均匀,温度梯度辐射状升高,热交换 面积逐渐降低以及热交换速度下降等(在后一阶段变得影响很大)。

The chemical engineer works with the chemist and a team of other engineers to design, construct, and operate the pilot plant. The
design aspect involves specifying equipment sizes, configuration, and materials of construction. Usually pilot plants are designed to be
quite flexible, so that a wide variety of conditions and configurations can be evaluated.
化学工程师与化学家和其他一 些工程师协作对中师车间进行设计、安装和运行,设计方面包括确定设备的尺寸、结构、
制造所用的材料 。通常中师车间的设计是有很大的变通性的,以便能对各种情况和构造进行评估。



Once the pilot plant is operational, performance and optimization data can be obtained in order to evaluate the process from an
economic point of view. The profitability is assessed at each stage of the development of the process. If it appears that not enough
money will be made to justify the capital investment, the project will be stopped.
中试车间一旦开始运转,就能获得性能 数据和选定最佳数值以便从经济学角度对流程进行评价。对生产过程的每一个阶
段可能获得的利润进行评 定。如果结果显示投入的资金不能有足够的回报,这项计划将被停止。

The pilot plant offers the opportunity to evaluate materials of construction, measurement techniques, and process control strategies.
The experimental findings in the pilot plant can be used to improve the design of the full-scale plant.
中师车间还提供了评价 设备制造材料、测量方法、流程控制技术的机会。中试车间的这些实验数据对于工业装置设计的
改善能提 供有用的帮助。

2. Design
Based on the experience and data obtained in the laboratory and the pilot plant, a team of engineers is assembled to design the
commercial plant. The chemical engineer’s job is to specify all process flow rates and conditions, equipment types and sizes, materials
of construction, process configurations, control systems, safety systems, environmental protection systems, and other relevant
specifications. It is an enormous responsibility.
2. 设计
根据在实验室和中试车间获得的经验和数据, 一组工程师集中起来设计工业化的车间。化学工程师的职责就是详细说明
所有过程中的流速和条件,设备 类型和尺寸,制造材料,流程构造,控制系统,环境保护系统以及其它相关技术参数。这是一
个责任重大 的工作。

The design stage is really where the big bucks are spent. One typical chemical process might require a capital investment of $$50 to
$$100 million. That’s a lot of bread! And the chemical engineer is the one who has to make many of the decisions. When you find
yourself in that position, you will be glad that you studied as hard as you did (we hope) so that you can bring the best possible tools and
minds to bear on the problems.
设计阶段是大把金钱花进去的时候。一个常规的化工流程可能需要五千万 到一亿美元的资金投入,有许多的事情要做。
化学工程师是做出很多决定的人之一。当你身处其位时,你 会对自己曾经努力学习而能运用自己的方法和智慧处理这些问题感
到欣慰。

The product of the design stage is a lot of paper:
(1) Flow sheets are diagrams showing all the equipment schematically, with all streams labeled and their conditions specified
(flow rate, temperature, pressure, composition, viscosity, density, etc.)
设计阶段的产物是很多图纸:
(1)工艺流程图。是显示所 有设备的图纸。要标出所有的流线和规定的条件(流速、温度、压力、构造、粘度、密度等)。

(2) P and I (Piping and Instrumentation) Drawings are drawings showing all pieces of equipment (including sizes, nozzle locations,
and materials), all piping (including sizes, materials, and valves), all instrumentation (including locations and types of sensors, control
valves, and controllers), and all safety systems (including safety valve and rupture disk locations and sizes, flare lines, and safe
operating conditions).
(2)管道及设备图。标明所有设备(包括 尺寸、喷嘴位置和材料)、所有管道(包括大小、控制阀、控制器)以及所有
安全系统(包括安全阀、安 全膜位置和大小、火舌管、安全操作规则)。

(3) Equipment specification Sheets are sheets of detailed information on all the equipment precise dimensions, performance
criteria, materials of construction, corrosion allowances, operating temperatures, and pressures, maximum and minimum flow rates, and
the like. These “spec sheets” are sent to the equipment manufacturers for price bids and then for building the equipment.
(3)仪 器设备说明书。详细说明所有设备准确的空间尺度、操作参数、构造材料、耐腐蚀性、操作温度和压力、最大和< /p>


最小流速以及诸如此类等等。这些规格说明书应交给中标的设备制造厂以进行设备生产。

3. Construction
After the equipment manufacturers (vendors) have built the individual pieces of equipment, the pieces are shipped to the plant site
(sometimes a challenging job of logistics, particularly for large vessels like distillation columns). The construction phase is the
assembling of all the components into a complete plant. It starts with digging holes in the ground and pouring concrete for foundations
for large equipment and buildings (e.g., the control room, process analytical laboratory, and maintenance shops).
3. 建造
当设备制造把设备的所有部分都做好 了以后,这些东西要运到工厂所在地(有时这是后勤部门颇具挑战性的任务,尤其
对象运输分馏塔这样大 型的船只来说)。建造阶段要把所有的部件装配成完整的工厂,首先要做的就是在地面打洞并倾入混凝
土 ,为大型设备及建筑物打下基础(比如控制室、流程分析实验室、维修车间)。

After these initial activities, the major pieces of equipment and the steel superstructure are erected. Heat exchangers, pumps,
compressors, piping, instrument sensors, and automatic control valves are installed. Control system wiring and tubing are run between
the control room and the plant. Electrical wiring, switches, and transformers are installed for motors to drive pumps and compressors. As
the process equipment is being installed, it is the chemical engineer’s job to check that it is all hooked together properly and that each
piece works correctly.
完成了第一步,就开始安装设备的主要部分以及钢铁上层建筑。要装配热交换器 、泵、压缩机、管道、测量元件、自动
控制阀。控制系统的线路和管道连接在控制室和操作间之间。电线 、开关、变换器需装备在马达上以驱动泵和压缩机。生产设
备安装完毕后,化学工程师的职责就是检查它 们是否连接完好,每部分是否正常工作。

This is usually a very exciting and rewarding time for most engineers. You are seeing your ideas being translated from paper into
reality. Steel and concrete replace sketches and diagrams. Construction is the culmination of years of work by many people. You are
finally on the launch pad, and the plant is going to fly or fizzle! The moment of truth is at hand.
对大部分工程师来说这通常是一个令人激动、享受成功的时候。你将看到自己的创意 由图纸变为现实。钢铁和混凝土代
替了示意图和表格。建筑是许多人多年辛劳的结果。你终于站到了发射 台上,工厂将要起飞还是最后失败。揭晓的那一刻即将
到来。

Once the check-out phase is complete, “startup” begins. Startup is the initial commissioning of the plant. It is a time of great
excitement and round- the-clock activity. It is one of the best learning grounds for the chemical engineer. Now you find out how good
your ideas and calculations really are. The engineers who have worked on the pilot plant and on the design are usually part of the startup
team.
测试阶段一旦完成,“运转阶段”就开始了。启动是工 厂的首项任务,是令人兴奋的时刻和日夜不停的工作。这是化学工
程师最好的学习机会之一。现在你可以 了解你的构思和计算究竟有些什么好。参与中试车间和设计工作的工程师通常也是启动
队伍中的人员。

The startup period can require a few days or a few moths, depending on the newness of the technology, the complexity of the
process, and quality of the engineering that has gone into the design. Problems are frequently encountered that require equipment
modifications. This is time consuming and expensive: just the lost production from a plant can amount to thousands of dollars per day.
Indeed, there have been some plants that have never operated, because of unexpected problems with control, corrosion, or impurities, or
because of economic problem.
启动阶段需要几天或几 个月,根据设计所涉及工艺技术的新颖、流程的复杂程度以及工程的质量而定。中间经常会遇到
要求设备 完善的问题。这是耗时耗财的阶段:仅仅每天从车间出来的废品会高达数千美金。确实,曾经有些车间因为没有预 计
到的问题如控制、腐蚀、杂质或因为经济方面的问题而从来没有运转过。

The engineers are usually on shift work during the startup period. There is a lot to learn in a short time period. Once the plant has
been successfully operated at its rated performance, it is turned over to the operating or manufacturing department for routine production


of products.
在启动阶段,工程师们通常需轮流值班。在很短的时间里有很多的东西需要学习。 一旦车间按照设定程序成功运转,它
就转变为产品的常规生产或制造部门。

4. Manufacturing
Chemical engineers occupy a central position in manufacturing. (or “operations” or “production,” as it is called in some
companies). Plant technical service group are responsible for the technical aspects of running an efficient and safe plant. They run
capacity and performance tests on the plant to determine where the bottlenecks are in the equipment, and then design modifications and
additions to remove these bottlenecks.
4. 制造
化学工程师在制造阶段占据中心的位置。车间技术服务部门负责车间有效而安全地运转的技术方面 。他们进行生产量和
性能测试以找出设备的瓶颈在哪,然后设计一些修正或附加的东西以解决这些瓶颈。

Chemical engineers study ways to reduce operating costs by saving energy, cutting raw material consumption, and reducing
production of off-specification products that require reprocessing. They study ways to improve product quality and reduce
environmental pollution of both air and water.
化学工程师研究一些方法节省能源,降低原材料消耗、减少 不合要求的需进行处理的产品的生产,以降低生产成本。他
们还研究一些提高产品质量、减少空气和水中 环境污染的措施。

In addition to serving in plant technical service, many engineers have jobs as operating supervisors. These supervisors are
responsible for all aspects of the day-to-day operation of the plant, including supervising the plant operators who run the plant round the
clock on a three-shift basis, meeting quality specifications, delivering products at agreed-upon times and in agreed-upon quantities,
developing and maintaining inventories of equipment spare parts, keeping the plant well maintained, making sure safe practices are
followed, avoiding excessive emissions into the local environment, and serving as spokespersons for the plant to the local community.
除了提供技术服务外,许多工程师还负责生产监督。这些监督保证工厂日常生产 的各个方面正常进行。包括管理换班工
作的操作工,满足质量要求,按期按量发出产品,生产并保持设备 备件的存储量,为车间设备维修,保证安全规则被遵守,避
免过多排出废物污染环境,并且做工厂对当地 社会的代言人。

5. Technical sales
Many chemical engineers find stimulating and profitable careers in technical sales. As with other sales positions, the work
involves calling on customers, making recommendations on particular products to fill customer’s needs, and being sure that orders are
handled smoothly. The sales engineer is the company’s representative and must know the company’s product line well. The sales
engineer’s ability to sell can greatly affect the progress and profitability of the company.
5. 技术销售
许多化学工程师发现在技术销售中充满了刺激性的、有利可图的机会。与其它 的销售业务一样,这项业务包括拜访客户,
推荐一些特别的商品以满足客户的需要,并确保订单能顺利完 成。销售工程师是公司的代表,必须十分清楚公司的产品生产情
况。销售工程师的销售能力极大地影响公 司的发展和利润。

The marketing of many chemicals requires a considerable amount of interaction between engineers in the company producing the
chemical and engineers in the company using the chemical. This interaction can take the form of advising on how to use a chemical or
developing a new chemical in order to solve a specific problem of a customer.
许多化工产品的市场开发需要制 造化工产品公司的工程师与使用化工产品公司的工程师密切合作。这种合作所采取的方
式可以是对如何使 用一种化学产品提出建议,或者是生产出一种新的化学产品以解决客户的某个特殊的困难。

When the sales engineer discovers problems that cannot be handled with confidence, he or she must be able to call on the expertise
of specialists. The sales engineer may sometimes have to manage a joint effort among researchers from several companies who are
working together to solve a problem.


当销售工程师碰到他自己没有把握解决的问题时, 他或她必须要请教专家。有时销售工程师还需组织来自不同公司的研
究人员共同努力来解决某个问题。

6. Research
Chemical engineers are engaged in many types of research. They work with the chemist in developing new or improved products.
They develop new and improved engineering methods (e.g., better computer programs to simulate chemical processes, better laboratory
analysis methods for characterizing chemicals, and new types of reactors ad separation systems). They work on improved sensors for
on-line physical property measurements. They study alternative process configurations and equipment.
6. 研究
化学工程师能从事多种类型的研究工作。他们与化学家联 合开发新的或革新的产品。他们探索新的和改良的工程技术(比
如更好的计算机程序以模拟化工工艺,更 好的实验室分析方法分析有代表性的化学产品,新型的反应和分离系统。)他们研究
改进的传感器以进行 物理性质的在线检测,他们还研究单个流程结构和设备。

Research engineers are likely to be found in laboratories or at desks working on problems. They usually work as members of a
team of scientists and engineers. Knowledge of the process and common types of process equipment helps the chemical engineer make
special contributions to the research effort. The chemical engineer’s daily activities may sometimes closely resemble those of the
chemist or physicist working on the same team.
研究工程师可能是在实验室或办公桌前钻研难题。他们通常是一组科学家或工程师中的一员 。了解生产流程以及通常流
程所使用的设备使化学工程师能在研究工作中做出突出的贡献。化学工程师的 日常工作有时颇似那些化学家和物理学家。





















Unit 4 Sources of chemicals
化学物质的来源
化学物质的数量多得惊人,其差异很大:所知道的化学物质的数量就达上千万种。如此的数量与理论
上可能形成的含碳化合物的数量相比,相形见绌。含碳化合物的数量之大是耦合的结果:即相对较强的碳
碳共价键的碳原子长链和异构体的形成。大部分这些化合物只是满足实验室好奇心或学术兴趣。然而,其
他剩余的达几千种,是商业和实践兴趣。因此,可以预料到这些化学物质的来源很广。虽然对无机化学品
如此,但是奇怪的是,大多数有机化学品来源于一种资源,即原油(石油)。


1. 无机化学品
Table1-1 无机化学品的主要来源
因为 “无机化学品”这个词(术语)涉及到(cover,包括、涵盖)的是除碳以外所有元素构成的化合物。 其来源的多样性并不很大(见表1-1)。一些较重要的来源是金属矿(包括重要的金属铁和铝)以及盐和海
水(用于生产氯、钠、氢氧化钠和碳酸钠)。在这些情况下,至少两种不同的元素化合以一种稳定的化合
物在一起。因此,如果要得到单个元素(也就是金属),那么提取过程除了纯物理的分离方法以外,还必
须涉及到化学处理(过程)。金属矿或无机矿很少以纯物质的形式存在,因此,处理过程的第一步通常是 :
(将无机矿中)从不要的固体如粘土或沙石中分离出来。固体筛分后经压碎和研磨,利用颗粒尺寸差异可
以完成一些物理分离。下一步骤则取决于所需矿物的本质及其特征。例如,铁矿常在磁分离器利用他们的
磁性加以分离。泡沫浮选是另一种广泛应用的分离技术。在该技术中,所需要的矿物,以细小颗粒形式存
在,借助被水溶液润湿能力的差异而与其他矿物加以分离。常加入表面活性剂(抗润湿剂),这些典型的
分子,一头为非极性部分(如长碳氢链),另一头为极性部分(如-NH2)。该极性基团与矿物相吸, 形成不
牢固的键;而碳氢基团与水相斥而阻止矿物被润湿,因而矿物能浮选。相反,其他固体物质很容易被润湿
而沉在水溶液中。搅拌溶液或液体中鼓泡以产生泡沫能大大促进表面活性剂包裹的矿物的漂浮,这些矿物
从容器中溢出到收集容器中,在收集容器,矿物得到回收。显然,该过程成功的关键在于,为所处理矿物
选择一种高选择的特定的表面活性剂。
2 有机化合物
相比于无机化学品来自于众多不同的资源(这一点我们已经明白了),商业上的一些重要的有机化合 < br>物基本上来源单一。如今,所有有机化合物的99%以上,可以通过石化工艺过程从原油(石油)和天然气
得到。这是一种有趣的情形— — 该情形一直在改变,而且将来也会变化,因为从技术上讲,相同的化学品
可以从其他原料得到。尤其是脂肪族化合物,可以通过由碳水化合物的发酵所得的乙醇加以生产,另一方
面,芳香族化合物可以从煤焦油中分离得到。煤焦油是煤炭化工过程的副产物。动植物油脂,是为数不多
的脂肪族化合物的特定的资源,这些脂肪族化合物包括长链脂肪酸(如正十八酸)和长链醇(如正十二烷
醇)。
化石燃料(即石油、天然气和煤)的形成要花上百万年,一旦用掉就不能被替换,因此,它们称之为
不可再生的资源。这与来自于植物的碳水化合物恰恰相反,碳水化合物能够较快被更新。一种较为普遍应
用的资源为蔗糖— — 一旦作物被收割和土地被清理,又可以种植和收割新的作物,通常少于一年。因 此,碳氢化合物可称为
可再生资源。据估计,植物原料(干重)的总的年产量为1*1011 吨。化石 燃料-天然气、原油和煤,主要用作为能源,而不
是作为有机化合物的资源。例如,各种石油分馏物的气 体,用于家用烹调和取暖、用作为汽车用的汽油、加热建筑物重燃油,
或用于在工业处理以产生
的蒸汽。通常,一桶原油的8%用于化学品的生产。下列数据可以说明,为什么化学工业在原油的使用方
面与燃料或能源消耗的工业展开着竞争。
显然,若我们愿意使用可代替化石燃料的其他能源,那么这些可替代能源可以利用的,同时,我们自
信地预料到在不久的将来,可以用上其他的可替代能源。因此,有必要要去保存宝贵的石油供应以用于化
学品的生产。“处理石油的最后一件事情是将之燃烧”该说法是有根据的。注意到这件事很有趣且有益的 :
早在1894 年门捷列夫(发现元素周期表之俄国科学家)就向当局报道,“石油是太宝贵的资源而不能将之
燃烧掉,应该将之以化学品资源加以保存。”
来自于碳水化合物(植物茎杆)的有机化学物质,职务的主要成分是碳水化合物,碳水化合物组成职
务的结构。它们为多糖(如纤维素和淀粉),大量的淀粉存在于食物(如谷类、大米和马铃薯)之中,纤
维素是组成细胞壁的主要物质,因而广泛存在,可以从木材、棉花等中得到。因此,来自于碳水化合物的
化学品的潜力是相当大的,而且该原料可再生。
从碳水化合物得到化学物质的主要途径是通过发酵过程。然而发酵过程不能利用多糖(如维素和淀 粉),因此,淀粉必须先收到酸性或酶水解反应生成更简单的糖类(单糖或二糖(如蔗糖),这些较为简单
的糖是发酵过程中的)合适的起始原料。
发酵过程是利用单细胞的微生物(一般有酵母菌、真菌、细菌或霉菌)生产特殊化学品。有些发酵农
家已用了上千年。最著名的例子为,谷物发酵生产含酒精的饮料。直到1950 年,该方法才成为生产脂肪
族有机化学品的最普遍的途径。因为生产的乙醇脱水生成乙烯,而乙烯是合成大量脂肪族化合物的关键中


间体。尽管用此方法生产的化学品有所减少,但是用这种方法生产汽车燃料方面存在大量 的兴趣。
反映在发酵过程的缺点可分为两方面(1)原料(2)发酵过程。因为植物茎杆是一种农业原料,其生
产和收割均为劳动力密集型的过程,所以相比之,它的原料费用高于原油的费用。同时,物料的运输更困
难,费用更高。与石化处理过程相比,发酵过程的主要缺点是:其一,时间通常要好几天,相比有些催化
石油反应只要几秒;其二,所得的产物通常是以稀的水溶液(浓度<10%)存在,因此,分离和纯化费 用
较高。因为微生物是活的体系,过程的条件几乎不容许改变。为了增加反应速度,即使相对于小的温 升,独有可能会导致微生
物的死亡和发酵过程终止。
另一方面,发酵方法的独特优点是,其选 择性高,一些结构复杂而很难以合成或者需要多步合成的化合物,通过发酵很容易制
得。著名的实例有多 种多样的抗生素的生产。如青霉素,头孢菌素和链霉素。
如果也基因工程中快速发展的过程中大量的实 际问题得到解决,那么发酵方面的兴趣存在很大的兴趣。在基因工程中。微生物
(如细菌)能定制地生产 成所需的化学品。然而,因为发酵反应速度慢和产物
分离费用高,在不久的将来要实现用发酵方法生产 大众化学品(即需求量极大的化学品如依稀,笨。)看来是不可能。
来自于动植物油和脂肪的有机化学 品,动植物油脂(常指类肪)是由甘油脂组成,甘油酯为三羟基醇,甘油(丙烷-1,2,3-
三醇,丙 三醇)。有多种不同的种植物油资源,较为普通的有,大豆,谷物,棕树核,油菜籽,橄榄油,动物脂肪和巨鲸。 这
些油类可通过溶剂萃取分离得到。有相当大的部分,烹调油脂的形式用食品工业中,用于生产黄油,人 选黄油和其他食品(如
冰激凌)。这些食品的烷基对人的健康的影响,
尤其对血液中的胆固醇 的影响,存在着争议。血液中的高胆固醇的含量会引起高血压和心脏病。目前的观点似乎赞成高含量不
饱 和的基因在降低胆固醇的水平和降低心脏病(发病率)危险是有利的。这引起如下趋势。不用烹调脂类和普通黄油 或人造黄
油(这些物质中饱和烷基含量丰富),而转向用烹调油和不饱和烷基的含量高的人造黄油。
类脂属于脂类(物质),用于生产化学物质时,以水解反应开始,虽然水解反应可以用酸或碱催化,
但碱催化效果更好,因为碱催化反应不可逆。碱性条件下的水解反应叫做皂化反应。
注意到这样事实很重要— 皂化反应,水解反应(脂肪分解)一级氢解反应不会利用单一甘油酯(或甲
基醇,实际上,所用植物油是各种甘油酯的混合物,因此(水解)产物也是混合物,需要分离。


Unit 5 Basic Chemicals
基本化学品
我们将化学工业部门分成两类,生产量较大的部门和产量较低的部门。在产量高的部门中,各种化学品的年产量 达上万吨至几
十万吨。结果这样所用的工厂专门生产某一个单个产品。这些工厂的连续方式进行操作,自 动化程度高(计算机控制)归类于
产量高的部门有硫酸,含磷化合物,含氮化合物,氯碱及其相关化合物 ,加上石油化学品和商品聚合物(如聚乙烯)(生产部
门)。除商品聚合物外,其它的均为重要的中间体 ,或基本化学品。这些基本化学品是其他许多化学品的生产原料,其他许多
基本化学品的需求量很大。
相反,产量低的部门主要从事精细化学品的生产。单个化学品的年产量只有几十吨到几千吨。然而,与高 产量的产品相比,这
些产品单位重量具有很高的价值。通常,精细化斜坡的生产与间歇方式操作在工厂中 ,而且这些工厂常进行多种产品的生产。
低产量生产部门生产农用化学品,染料,药品和特种聚合物(如 聚醚醚酮)。
基础化学品在化学工业中得不到支持,它们不那么引人注意(如药品),有时候利润不很 高。其利润来自于经济盛衰时难以预
测的周期。
这些基本化学品不被公众注意到和直接使用, 因此其重要性常得不到理解。即使在化学工业中,其重要性也得不到足够的重视。
然而,如果没有这些基 本化学品,其他工业就不复存在。
基本化学品处于原料(及那些从地下通过采矿、开采或用泵抽出来的物质)和最终产品的中间位置。 < br>基本化学品的一个显著的特征就是它们的生产规模,每一种(基本化学品)的生产规模都相当大。图2-1 表示在1993 年美国市
场上的25 中化学品。(为了使我们了解化学品的分类与生产量有关。)通 常,基本化学品生产于那些年产量上万吨的工厂。
年产量10 万吨的工厂每小时要生产1.25 吨。基本化学品的另一显著重要的特征是其价格。大多数价格相当便宜。
基本化学品工业所作的工作( 或任务)是找到经济的途径将原来转变为有用的中间体。生产厂家要对它们的产品收取较高的价
格几乎没 有余地,因此,那些最低费用生产产品的厂家可能获得的利润最高。这就意味着,厂家就必须不断准备寻求新的, 更
经济的生产和转变原料的方法。
许多基本化学品为石油精炼的产物,而部分基本化学品工业 ----硫、氮、磷和氯碱工业是把除C 和H、S 外的元素转变为化学品。


总之,这 些产品和石化工业的基本产物两者结合起来可生产无数重要的化学物质,这些重要的化学物质可作为其余化学工业 的
原料。
基本化学工业现在面临着其历史上中最大的挑战之一,该工业中的产品消费部门 ---农业以停止增长。同时大大减小了对肥料的
需求。西方的农场主生产了大多的食物,政府减小了对 农业部门的津贴,结果导致了更少的土地用于耕种和所需的肥料减少。
过量肥料的流失而引起的环境的关 注也减少了对肥料的需求。
诸如含氯化合物之类的产品,已收到了来自环境学家的压力。根据《关于消 耗臭氧层物质的蒙特利尔白皮书》,一些产品将受
到禁止。而其它的物质,可以受得住环境学家的压力。 基本化学品工业再也不会依靠在需求量方面的长期增长。
为了实现更好的规模经济和某一特殊产品更好 的市场地位,厂家相互交换工厂(车间),该工业注重不断合并联合。这使从事
某一工业的人员减少,使 该工业达到更好的供需平衡和更好的利润。基本化学品工业正逐渐转向为其他化学工业服务,而越来
越小 地为农业服务。
基本化学品受到的压力是许多大规模过程引起的(觉察得到的)较大的环境污染。尽管 许多大厂家的生产效率较高,但是该工
业要实现最好的环境标准还有很长的路要走。增加重复利用的驱动 力和理想化的无排放的工厂,是影响接下来十年该工业发展
的主要因素。
技术的进步不会停止 ,我们将日益重视无污染的工厂和过程。厂家将在效率上展开竞争。那些能以最低的成本生产最高质量产
品的厂家将繁荣昌盛。这需要厂家在技术改进方面保持投资。基本化学品的合成有用的中间体的新颖方法将不断被 人们发现。
在基本化学品工业中,仍然还有许多工作有待去做。


Unit 6 Chlor-Alkali and Related Processes
氯碱及其相关过程
纵观历史,大众化学品工业在氯碱及其相关过程之上。该部分通常包括氯气、苛性苏打(氢氧化钠)
无水碳酸钠(以各种形式存在的碳酸钠的衍生物),以及以石灰为基础的产品。
自从无水碳酸 钠和氢氧化钠的各种制备工艺发现以来,两者在作为碱为主要原料方面相互竞争。电解过程的特殊经济性意味着< br>不管对氯气和氢氧化钠这两种不同类型的产品的相对需求量如何,你只有以固定的比例同时制备氯气和氢氧 化钠。这引起了氢
氧化钠的价格的摇摆不定,从而使得纯碱作为一种碱或多或
少有利。 氯气苛性苏打和纯碱的生产都取决于廉价易得的原料供应,前者的生产需要廉价的海水和电力的供应,而纯碱 的生产需要海水、
石灰和大量的能耗。纯碱厂只有在其原料不必要长距离的运输时才能赢利。
这些原料供应利用是影响化工企业位置分布的一个重要因素。
1. 石灰为基础的产品
一种关键(重要)原料是石灰石。石灰石主要是由CaCO3 组成,高质量的石灰石可直接用于下一步 反应。石灰石通常在大型
露天石矿中开采,许多采石矿也进行原料的一些处理。
从石灰石得到两种重要的产物:生石灰(CaO)和熟石灰水,生石灰是由石灰石根据该反应是热分解
(1200-1500℃)制备得到。
CaCO3 — — > CaO+ CO2
一般的,石灰石经过粉碎加入倾斜旋转窑的较高端,在此发生热分解反应,生石灰在另一端回收。
然而,通常生石灰用于进一步反应而分离,而加入其它化合物,与生石灰在窑的较低口处生成最低产品。
例如,加入铝矿、铁矿和沙石可生成硅酸盐水泥。纯碱的生产,通常要向生石灰加入焦炭,焦炭燃烧生成 纯碱所需的CO2,熟
石灰由生石灰和水的反应制造,较生石灰更加方便。
大约40%的石灰 工业的产品用于钢铁制造业。在钢铁制造业中,纯碱用来与铁矿石中难溶解的硅酸盐反应,生成流态矿渣,矿渣漂浮于表面上,很容易从液态金属中分离,叫少量但重要的石灰工业的产品用于化学品的制造,污染控制和 水处理。从石灰
石得到的最重要的化学茶品是纯碱。
2. 纯碱
索尔维工艺,该工艺发现于1965 年由ES 优化:工艺是以当含氮的盐溶液经来自于石灰窑中焦炭燃烧产物CO2 碳酸盐反应时,
NaHCO3 沉淀析出为基础。NaHCO3 经过滤、干燥、煅烧生成CaCO3。过滤后NH4Cl溶液和熟石灰反应后( 溶液体呈碱性)。
蒸馏出NH3 在该过程中循环利用,生成物CaCl2 是废弃物或副产物。
对于某一简单的基本产物来说,索尔维法看起来十分复杂。该反应的基本原理是,以NaCl2 和CaCO3为原料生成产物CaCl2 和
Na2CO3.然而发生于原料和产物之间的反应并不明显,需要利用NH3 和Ca(OH)2作为中间化合物。
该过程的基本原理为:利用准确的控制组分(尤其是NH3 和NaCl)的浓度,NaHCO3 能够从含NaCl、CO2 和NH3 的溶液里
沉淀析出。该过程的关键是控制溶液的酸碱强度和结晶的速度,该工艺的基本路线如
下,NH3 气于氨气吸收器中吸收于事先经纯化的海水中,纯化的海水以减小Ca+、Mg+离子的量 。(Ca+、Mg+在生产过程中
易产生沉淀而阻塞管道)。含NaCl 和NH4HCO3 的溶液经吸收了CO2 的吸收塔(CO2 气体量塔
底向上流) 开始时形成(NH4)2CO3 然后再生成NH4HCO3。
在工厂的下面步骤中,Nacl 和NH4HCO3 经复分解反应生成NaHCO3(以沉淀形式形成)和NH4Cl。
过滤将固体NaHCO3 从溶液中分离。将NaHCO3 送至旋转干燥器,在该干燥器中,NaHCO3 失去水和CO2后生成疏松的晶体
块(即轻质纯碱)它的主要成分为Na2CO3 蓬松的晶体块很轻,是因为NaHCO3 失去CO2
后,留下很多空隙,而保留原来的晶体形状。通 常要得到密度更大的物质很方便,加入水(水能引起咦密度较大的形式重结晶)
进一步干燥即可实现。
值得争议的是,上述的化学知识是否为该过程的很好的描述,但这些只是肯定有助于理解过程。想要对此 过程有详细的理解,
必须要熟悉该组分体系中关于溶度积的很多知识。需要知道的重要知识是,该体
系是复杂体系,为了使该过程高效操作,需要对该过程每部分小心控制。
该过程的一个缺点是:产生的CaCl2 的量很大,其产生量比所需量大得多。因此,大部分CaCl2 只是简单的倒掉(CaCl2 毒性
不 大),如果能要该过程中的有的进料加以利用,那么该过程是有优势,例如,从该氯化物可产生HCl。
纯碱的用途,有50%的纯碱销往玻璃制造业,因为穿件是玻璃制造过程中的主要原料。因此纯碱工业的财富与 玻璃需求量息息
相关。纯碱作为一种碱在许多化学过程中与NaOH 存在直接竞争。Na2SO3 是由纯碱和SiO2 在1200-1400℃反应衍生而来的另


一类化学物质。硅酸是 具有大表面积细小颗粒的Na2SO3,可用于催化剂、色谱之中, 洗涤剂和肥皂中作为部分磷酸盐的替代
品。
3. 生成Cl2NaOH 的电解过程
简介,在化学工业法杖是的各个时期,Cl2 和NaOH 两者的需求量均很大,但是不幸的是,对于 电化学工厂的操作人员来说,
两者的需求量必总是相同。Cl2 可作为漂白粉或作为漂白粉的生产原料 ,水供应的消毒剂,以及作为塑料和溶解剂知道的原料。
苛性钠用于生产纯碱、肥皂和纺织品,以及在多 种化学过程中作为一种十分重要的原料。
所有的电解有着共同之处,盐的电解生成Cl2 和NaOH。大多数生产过程是电解(盐的)水溶液,但是有些重要的工厂,电解
熔融盐生成Cl2 和液态钠。这些电解熔融盐的过程用用于重要液态Na 的工业。虽
然石油添加剂厂家多种多样,设会 出现液态钠的其他用途,但是他的主要是用于生产四烷基铅石油添加剂。
实质上用于水溶液电解过程有 三种不同的电解槽:水银槽、隔板槽和膜电解槽。膜电解槽只是用于此案在化工厂中新的生产过
程,但是 还存在着大量的旧生产过程,尽管说阴曹涉及到对环境的影响,但是许多生产厂家上位法此案膜片电解槽代替水印 电
解槽的经济性。
所有的电解反应都是以电子作为化学反应的试剂的观点为基础。设水电解过程的基本反应可写成下式:
阳极2Cl— — 2e-→ Cl2
阴极2H2O + 2e— → H2 + 2OH—
总反应为2Na+ + 2Cl— + 2H2O→ NaOH + Cl2 + H2
该反应的自由能为正,因此,需要电驱使进行。
像其他许多化学品工艺一样,尽管该反应看起 来似乎极其简单,但是有一些方面很复杂。首先,该反应的产物必须分开,如果
H2 和Cl2 允许混合在一起,它们会剧烈反应。H2 和Cl2 反应生成HOCl 和氯化物
(两者均会浪费产物、生成副产物)。接着,HOCl 和次氯酸盐反应生成氯酸盐(ClO3
-)、质子和更多的氯化物。OH— 在阳极区反应生成能污染Cl2 的O2。所有的这些反应可降低效率和(或)引起分解困难或
污染
问题。因此,在产物销售之 前,有必要对这些反应清理。理解各种用于电解过程的关键是各种类型的过程分离反应产物的方式。
尽管 不同的制造商所用的电解槽在细节方面有着多种改变,但是用于盐水的电解过程的电解槽基本可分为以上三类。
4、Cl2 和NaOH 的用途
NaOH 的用途之多,以致很难将它们方便地进行分类。 最大的用途之一是用于造纸,造纸业中木材的处理需要强碱。有些国家
造纸业中NaOH 的消耗占其产 量的20%,另外的20%用于无机化学品(如,次氯酸钠、漂白粉和消毒剂)的生产。各种有机合
成约 消耗另外的15%,氧化铝和肥皂的生产需要少量的NaOH。
Cl2 广泛用于其它各种产品的生产。在全世界范围内大约有14 的Cl2 用于生产氯乙烯(生产PVC 的单体)。14 至12 的Cl2
用于水的纯化。尽管因为《关于消耗臭氧层物质的蒙特利议定书》多种溶剂正在被
逐步淘汰, 但是仍有高达20%的氯气用于溶剂的生产(如甲基氯仿、三氯乙烯等)。全世界范围内,大约10%的Cl2 用于无机
含氯的化合物的生产。尽管Cl2 用于漂白木材浆是来自环境压力的另一种途径,但是在一些国家Cl2 的十分重要的用途是用于
木材浆的漂白。



Unit 7 Ammonia, Nitric Acid and Urea
氯、硝酸和尿素
虽然N2 占我们呼吸的空气34 以上,但是氯气不容易用于进一步化学应用。对化学工业来说,N2 的生成有用化学品 的生物转
化反应难以实现,因为所有的工业技术人员的努力(或尝试)还没有找到该过程
的简单其他方法。在常压和室温条件下,豆类植物能从空气中吸入N2 将之转化为NH3 以及含NH 4-的产物。尽管(化学工艺
师)花了一百年的精力,要实现上述转化,化学工业仍然需要高温和上百个 大气压的
压力。直到Harber 过程的发明,所有的含N 化学品都来自于有生物活性的矿物资源。
基本上,所生产的化学品中所有的N(元素)都来自于Harber 法得来的NH3。NH3 的生产之大,(尽管因为氨分子较轻,生
产的其它产品的量更大,但其生产的NH3 的分子数要多于其他任何化合物),以及
该过程的能源是如此的密集,以致于据估计,在二十世纪八十年代NH3 的生产就消耗全世界能源供应的
3%。
1、Harber 法合成NH3
引言所有的生产NH3 的方法基本都是以Harber 法为基础,稍稍加以改变,该过程是由Harber、Nerst、
Bosh 在德国于一战前开发出来的。
N2 +3H2≒2 NH3
原则上,H2 和N2 间的反应很容易进行,该反应是放热反应,低温时平衡向右移动。所不幸的是,
自然界赋予的N2 一个很强的叁键,这使得N2 分子不易受热力学因素的影响。用科学术语来说,该分子是动力学惰性的。因此,要使该反应以一定的速度进行,需要相当苛刻的反应条件。实际上,“固定”(意
思相互矛盾,“有用的反应活性”)氦的一种主要来源是闪电过程,闪电时生产大量的热量,把N2 和O2
转化为N2O.
在化工厂中要得到可观的NH3 的转化率,我们有必要使用催化剂。Harber 发现的催化剂(这使他获
得诺贝尔奖)。是一些价廉的含铁的化合物。即使有该催化剂,这反应也需要很高压力(早期高达600 个大气压)和高温(大
约4000C)
因为四个气体分子转化为两个气体分子,所以增加压力 使平衡向右(正方向)移动。然而,尽管高温使反应速度加快,但是高
温使平衡向右移动,因此,所选的 条件必须要折中的能以合理的速率得到令人满
意的转化率。条件的准确选择将取决于其他的经济因素和催化剂的具体情况。因为资本和能耗费用越发重
要,当代的工厂已经趋向于比早期工厂在更低的压力和更高的温度(循环使用未转化的物料)下进行操作 。
氮的生物固定也使用了一种催化剂,该催化剂镶在较大的蛋白质分子中含有钼和铁,其详细结构直到
1992 年才被化学家弄清楚,该催化剂的详细作用机理尚未清楚。
原料。该过程需要以下几种原料(进料)的能源、N2 和H2。N2 很容易从空气中提取,但是H2 的来源很成问题。以前,H2 来
源于通过煤的焦化反应,煤用作蒸汽重整的原料(主要是C 的来源),在蒸汽
重整过程中,水蒸气与C 反应生成H2、CO 和CO2。如今,以天然气(主要是甲烷)代替,尽管也使用来自石油的烃类物质。
通常,制NH3 的工厂包括与NH3 生产相连接的H2 生产车间。
在重整反应之前,含硫化合物必须从烃原料中除去,因为它们既能污染重整催化剂又能污染Harber
催化剂。第一除硫步骤需要钴-铜催化剂。该催化剂能将所有的含硫化合物氢化生成H2S,H2S 能与ZnO
反应(ZnS 和H2O)加以除去。
主要的重整反应中,下列甲烷反应最为典型(甲烷的反应发生于约7500C.含镍催化剂上)
CH4 + H2O→ CO + 3H2 (合成气)
CH2 + 2H2O→ CO2 + 4H2
其他烃经历类似反应。
在次级重整器中,空气注入温度11000C 的气流,除了发生其他反应外,空气中的O2 与H2 反应生成H2O,结果剩下不会污染
的O2 的混合物,该混合物中O2 与H2 的比接近理想比3:1.然而,下一步
反应必须通过下列转化反应将更多的CO 转变为H2 和CO2 。
CO+ H2O→ CO2 + H2
为使其尽可能完全的转化,此反应应该在较低温度下以两步进行(一步是在4000C 用铁为催化剂,另
一步是在2000C 下用催化剂)。


下一步中,CO2 必须从气体混合物中除去。除去CO2 可以用该酸性气体与碱性溶液(如KOH 和(或)
单乙醇胺或二乙醇胺反应得以实现。
这一步中,任然存在CO(污染Harbor 催化剂)对H2-N2 混合物造成很大污染,需要用另一步去将CO 得量降低至PPM 级,
这一步称为甲烷化反应,涉及到CO 和H2 反应生成甲烷(即一些重整反应的逆
反应),该反应大约在325℃操作,用一种Ni 催化剂。
合成气混合物准备用于Harbor 反应
NH3 的生产各种不同氨厂的共同特征是合成经过加热,压缩,递往含成催化剂的反应器中,该基本
反应方程式很简单:
N2 + 3H2≒2NH3
该工业要实现的事:反应速度和反应产率的结合要令人满意, 不同的时期和不同的经济环境下谋求 < br>不同的折中方案,早期的制氨厂热衷于高压反应(其目的是在单程反应器中提高产率)但是当今大多数氨厂 采用在较低的压力,
很低的单程转化率,同时为节能而选择较低温度。为了确保反应器中的转化率最大,
通常在当反应达到平衡时,冷却合成气,使用热交换器或者在反应器的合适位置注入冷却氨,可实现合成
气的冷却,这样做的作用是:在反应在尽可能接近平衡使其冷冻停止,因为此反应时放热反应(同时在较
高温度下的平衡对氨的合成时不利的)所以为了得到好的收率,可以用这种方法,对热量进行很好的控制 。
哈伯法的产物由氨和合成气混合物(组成)因此,下一步需要将两者进行分离以能循环利用合成气,
这可以压缩氨气得以实现(氨气的挥发度较其他组成小得多,大约在— 40℃沸腾)
氨的用 途氨的主要用途不是用于进一步应用的含氨化合物的生产,而是用于生产肥料(如尿素,硝酸铵和磷酸铵)。肥料 消耗
了所生产氨的80%。例如:在1991 年美国消费的由氨得来的产物如下:其中大
部分用作肥料(数量以百万吨计)尿素(4.2 百万吨)硫酸铵(二百二十万吨),硝酸铵(二百六十万吨),
磷酸氢二铵(一千三百五十万吨)。
氨的化学应用各式各样,尽管在制备纯碱的索维尔工艺中氨气得到回收而没出现于最终产品中,但是
该过程需要使用氨气,很多过程直接吸收氨气,这些过程包括氰化物和芳香族含氮化合物(如吡啶)的生
产。许多聚合物(如尼龙和丙烯酸类聚合物)中的氮可以追溯到氨,通常通过睛或氰(HCN)大多数的 其
他过称(工艺)以氨制的硝酸或硝酸盐作氮源,硝酸铵,用作含氮的肥料,它的另一种主要用途用作大众
化炸药。
2 硝酸
硝酸的生产化学工业制造其他原料时,所用的大部分氮元素不是以氨的形式直接利用,而是先将氨
转化为硝酸,硝酸的生产大约消耗所生产的氨的20%
氨生成硝酸的转化反应是一个三步过程:
1 4NH3 + 5O2→ 4NO + 6H2O
2 2NO +O2→ 2NO2
3 3NO2+H2O→ 2HNO3+NO
第一个反应用铂(实际上是铂铑金属网)催化,该催化反应可以再实验室上用一根铂丝和浓氨水溶液
观察到。初看起来,生成硝酸的总反应似乎很简单,所不幸的事,实际过程比化学家和工程师所想的要糟
的多,因此,存在许多复杂的因素。
工业上,第一反应于含铂铑金属网的反应器中,在900 度左右进行,温度由该反应产生的热量得以维
持,在该温度下,一些重要的副反应也进行得很快,其一,氨和空气混合物能被氧化生成氨气和水(如果
反应器器壁的温度高,那么该反应趋向于在壁上进行,因此有必要特意将之冷却),其二,催化剂可促进
第一反应的产物NO 的分解,生成氨气和氧气,因此重要的是尽可能快地将产物移出反应器,尽管这一做
法与下列事实相矛盾:为使原料和催化剂得以反应,有必要保持原料与催化剂接触时间足够长。其三:反
应产物NO 与氨反应生成氨气和水,因此重要的事,不让过多的暗器流过催化剂床层,否则,原料不可回
收而浪费。利用精心设计的反应器,控制温度和通过反应器的流速可以实现这些矛盾要素的控制。通常该
反应的实际接触时间约3×10-4 秒
第二步和第三步反应复杂性较小,但是,两者的反应速度很慢,尚未发现高效的催化剂,一般的,令
氨气和NO 的混合物流经一系列的冷凝压缩器,在这些压缩器中发生部分氧化反应,低温对该反应有利。
当混合气体流经大型泡罩吸收塔时,NO2 从该混合气体得以吸收,塔底为55%— 60%硝酸 < /p>


因为硝酸在68%时与水形成共沸物,所以不能用蒸馏法加工以浓缩,硝酸厂通常利用含9 8%的硫酸塔
在其塔顶去生成90%硝酸,如有必要,利用硝酸镁对之进一步脱水可得到接近100%的硝酸
硝酸的用途在所生产硝酸大约有65%与氨反应制造硝酸铵,80%的硝酸铵用于肥料,其余的用作炸
药。硝酸的另一个主要作用是用于有机硝化反应,几乎所有的炸药最终都是来自硝酸(大部分为硝酸酯, 如硝化甘油或为硝化芳
香族化合物如三硝基甲苯)在合成重要的硝基或氨基芳香族中间体时(如苯胺)时 ,
第一步为利用和硝酸的硝化反应。苯胺的合成,第一步为芳香族化合物的硝化,然而将硝基还原为胺基。
许多重要的染料和药物最终都是通过该反应得到,尽它们的需求量很小,聚氨酯塑料的制备时以芳香族异
氰酸酯为基础,而芳香族异氰酸酯最终来自于硝化甲苯和苯,该用途大约要消耗5%— 10%的硝酸产量
3 尿素
尿素的生产,另一种重要的直接由氨大量生产的产物为尿素,大约有20%的氨用于尿素的生产,尿素
是通过CO2 和NH3 的高压反应合成(一般为200— 400 个atm 和180℃— 210℃)该反应可分为两步:
1 CO2+2NH3-NH2CO-2NH+4
2 NH2CO-2NH+4-NH2CONH2+H2O
该高压反应可实现将60%的CO2 转化为氨基甲酸酯,生成的混合物输入低压分解器使之转化为尿素,
未反应的物料被输回该工艺中高压步骤的开始阶段,这样做可以大大提高车间的总效率,第二阶段所得的
溶液可直接用作液态含氮肥料或经浓缩生产纯度为99%固体尿素
尿素的用途尿素的含氮量高使之成为另一种有利氮肥,尿素占氮肥市场的绝大部分,其他的用途也 很重要,但是只占所生产品尿素的10%左右。尿素的最大的另一用途是用于树脂(甲醛二聚氰酰胺和尿素
甲醛)例如这些树脂用作胶合板粘结剂和弗莱卡的表面。




Unit 10 What Is Chemical Engineering?
什么是化学工程学
In a wider sense, engineering may be defined as a scientific presentation of the techniques and facilities used in a particular
industry. For example, mechanical engineering refers to the techniques and facilities employed to make machines. It is predominantly
based on mechanical forces which are used to change the appearance andor physical properties of the materials being worked, while
their chemical properties are left unchanged. Chemical engineering encompasses the chemical processing of raw materials, based on
chemical and physico- chemical phenomena of high complexity.
广义来讲,工程 学可以定义为对某种工业所用技术和设备的科学表达。例如,机械工程学涉及的是制造机器的工业所用
技 术和设备。它优先讨论的是机械力,这种作用力可以改变所加工对象的外表或物理性质而不改变其化学性质。化学 工程学包
括原材料的化学过程,以更为复杂的化学和物理化学现象为基础。

Thus, chemical engineering is that branch of engineering which is concerned with the study of the design,
manufacture, and operation of plant and machinery in industrial chemical processes.
因此,化学工程学是工程学的一个分支,它涉及工业化化学过程中工厂和机器的 设计、制造、和操作的研究。

Chemical engineering is above all based on the chemical sciences, such as physical chemistry, chemical thermodynamics, and
chemical kinetics. In doing so, however, it does not simply copy their findings, but adapts them to bulk chemical processing. The
principal objectives that set chemical engineering apart from chemistry as a pure science, is “to find the most economical route of
operation and to design commercial equipment and accessories that suit it best of all”. Therefore, chemical engineering is inconceivable
without close ties with economics, physics, mathematics, cybernetics, applied mechanics, and other technical sciences.
前述化学工程学都是以化学科学为基础的,如 物理化学,化学热力学和化学动力学。然而这样做的时候,它并不是仅仅
简单地照搬结论,而是要把这些 知识运用于大批量生产的化学加工过程。把化学工程学与纯化学区分开来的首要目的是“找到
最经济的生 产路线并设计商业化的设备和辅助设备尽可能地适应它。”因此如果没有与经济学,物理学,数学,控制论,应用
机械以及其它技术的联系就不能想象化学工程会是什么样的。



In its early days, chemical engineering was largely a descriptive science. Many of the early textbooks and manuals on chemical
engineering were encyclopedias of the commercial production processes known at the time. Progress in science and industry has bought
with it an impressive increase in the number of chemical manufactures. Today, petroleum for example serves as the source material for
the production of about 80 thousand chemicals. The expansion of the chemical process industries on the one hand and advances in the
chemical and technical sciences on the other have made it possible to lay theoretical foundations for chemical processing.
早期的化学工程学以 描述性为主。许多早期的有关化学工程的教科书和手册都是那个时候已知的商品生产过程的百科全
书。科 学和工业的发展使化学品的制造数量迅速增加。举例来说,今天石油已经成为八万多种化学产品生产的原材料。一 方面
是化学加工工业扩张的要求,另一方面是化学和技术水平的发展为化学工艺建立理论基础提供了可能 。

As the chemical process industries forged ahead, new data, new relationships and new generalizations were added to the
subject- matter of chemical engineering. Many branches in their own right have separated from the main stream of chemical engineering,
such as process and plant design, automation, chemical process simulation and modeling, etc.
随着化学加工工业 的发展,新的数据,新的关系和新的综论不断添加到化学工程学的目录中。然后又从主干上分出许多
的分 支,如工艺和工厂设计,自动化,化工工艺模拟和模型,等等。

1. A Brief Historical Outline
Historically, chemical engineering is inseparable from the chemical process industries. In its early days chemical engineering
which came into being with the advent of early chemical trades was a purely descriptive division of applied chemistry.
1. 简要的历史轮廓
从历史上来说,化学工程学与化学加工工业密不可分。在早期,化学工程学随着早期化 学产品交易的发展而出现,是应用化学
的纯描述性的分支。

The manufacture of basic chemical products on Europe appears to have begun in the 15th century when small, specialized
businesses were first set up to turn out acids, alkalis, salts, pharmaceutical preparations, and some organic compounds.
在欧洲,基础化学产品的制造出现在15世纪。一些小的、专门的企业开始创立 ,生产酸、碱、盐、药物中间体和一些有机
化合物。

For all the rhetoric of nineteenth-century academic chemists in Britain urging the priority of the study of pure chemistry over
applied, their students who became works chemists were little more than qualitative and quantitative analysts. Before the 1880s this was
equally true of German chemical firms, who remained content to retain academic consultants who pursued research within the university
and who would occasionally provide the material for manufacturing innovation. By the 1880s, however, industrialists were beginning to
recognize that the scaling up of consultants’ laboratory preparations, and syntheses was a distinctly different activity from laboratory
investigation. They began to refer to this scaling problem and its solution as “chemical engineering”—possibly because the mechanical
engineers who had already been introduced into works to who seemed best able to understand the process involved. The academic
dichotomy of head and hand died slowly.
由于十九世纪英国的学院化学家强调纯化学 的研究高于应用化学,他们的要成为工业化学家的学生也只是定性和定量分析
者。在19世纪80年代以 前,德国的化学公司也是这样。他们愿意聘请那些在大学里进行研究的人作顾问,这些人偶尔为制造
的革 新提供一些意见。然而到了80年代,工业家们开始认识到要把顾问们在实验室的准备和合成工作进行放大是一个 与实验
室研究截然不同的活动。他们开始把这个放大的问题以及解决的方法交给“化学工程师”—这可能 是受到已经进入工厂的机械
工程师的表现的启发。由于机械工程师熟悉所涉及的加工工艺,是维修日益复 杂化的工业生产中的蒸气机和高压泵的最合适的
人选。学院研究中头和手两分的现象逐渐消亡。
Unit operation. In Britain when in 1881 there was an attempt to name the new Society of Chemical industry as the “Society of
Chemical engineers”, the suggestion was turned down. On the other hand, as a result of growing pressure from the industrial sector the
curricula of technical institutions began to reflect, at last, the need for chemical engineers rather than competent analysts. No longer was
mere description of existing industrial processes to suffice. Instead the expectation was that the processes generic to various specific
industries would be analyzed, thus making room for the introduction of thermodynamic perspectives, as well as those being opened up


buy the new physical chemistry of kinetics, solutions and phases.
单元操作。1881年英国曾经 准备把化学工业的一个新的协会命名为“化学工程师协会”,这个建议遭到了拒绝。另一方面,
由于受到 来自工业界日益加重的压力,大学的课程开始体现出除了培养分析工作者还要培养化学工程师的要求。现在仅仅对 现
有工业过程进行描述已经不够了,需要对各种特殊工业进行工艺属性的分析。这就为引入热力学及动力 学、溶液和相等物理化
学新思想提供了空间。

A key figure in this transformation was the chemical consultant, George Davis (1850-1907), the first secretary of the Society of
Chemical Industry. In 1887 Davis, then a lecture at the Manchester Technical School, gave a series of lectures on chemical engineering,
which he defined as the study of “the application of machinery and plant to the utilization of chemical action on the large scale”. The
course, which revolved around the type of plant involved in large-scale industrial operations such as drying, crashing, distillation,
fermentation, evaporation and crystallization, slowly became recognized as a model for courses elsewhere, not only in Britain, but
overseas. The first fully fledged course in chemical engineering in Britain was not introduced until 1909;though in America, Lewis
Norton (1855-1893) of MIT pioneered a Davis-type course as early as 1888.
在这个转变期,一位关键的人物是化学顾问George Da vis,化学工业协会的首任秘书。1887年Davis那时是Manchester专
科学校的一名 讲师,做了一系列有关化学工程学的讲座。他把化学工程学定义为对“大规模化学生产中所应用的机器和工厂”< br>的研究。这们课程包括了大规模工业化操作的工厂的各种类型,如干燥、破碎、蒸馏、发酵、蒸发和结晶。 后来逐渐在别的地
方而不仅仅在英国,而是国外,成为许多课程的雏形。英国直到1909年化学工程学 才成为一门较为完善的课程,而在美国,
MIT的Lewis Norton早在1888年就已率先开出了Davis型课程。

In 1915, Arthur D. Little, in a report on MIT’s programme, referred to it as the study of “unit operations” and this neatly
encapsulated the distinctive feature of chemical engineering in the twentieth century. The reasons for the success of the Davis movement
are clear: it avoided revealing the secrets of specific chemical processes protected by patents or by an owner’s reticence—factors that
had always seriously inhibited manufacturers from supporting academic programmes of training in the past. Davis overcame this
difficulty by converting chemical industries “into separate phenomena which could be studied independently” and, indeed, experimented
with in pilot plants within a university or technical college workshop.
1915年,Arthur D. little 在一份MIT的计划书中,提出了“单元操作”这个 概念,这几乎为二十世纪化学工程学的突出特
点做了定性。Davis这一倡议的成功原因是很明显的: 它避免了泄露特殊化学过程中受专利权或某个拥有者的保留权所保护的
秘密。过去这种泄露已经严重限制 了制造者对学院研究机构训练计划的支持。Davis把化学工业分解为“能独立进行研究的单
个的工序 ”从而克服了这个困难。并且在大学或专科学校的工厂里用中试车间进行了试验。

In effect he applied the ethics of industrial consultancy by which experience was transmitted “from plant to plant and from process
to process in such a way which did not compromise the private or specific knowledge which contributed to a given plant’s profitability”.
The concept of unit operations held that any chemical manufacturing process could be resolved into a coordinated series of operations
such as pulverizing, drying, roasting, electrolyzing, and so on. Thus, for example, the academic study of the specific aspects of
turpentine manufacture could be replaced by the generic study of distillation, a process common to many other industries. A quantitative
form of the unit operations concept emerged around 1920s, just in time for the nation’s first gasoline crisis. The ability of chemical
engineers to quantitatively characterize unit operations such as distillation allowed for the rational design of the first modern oil
refineries. The first boom of employment of chemical engineers in the oil industry was on.
他采用了工业顾问公司的理念,经验传递从一个车间到另 一个车间,从一个过程到另一个过程。这种方式不包含限于某个
给定工厂的利润的私人的或特殊的知识。 单元操作的概念使每一个化学制造过程都能分解为一系列的操作步骤,如研末、干燥、
烤干、电解等等。 例如,学校对松节油制造的特殊性质的研究可以用蒸馏属性研究来代替。这是一个对许多其它工业制造也很
普通的工艺过程。单元操作概念的定量形式大概出现在1920年,刚好是在第一次全球石油危机出现的时候。 化学工程师能赋
予单元操作定量特性的能力使得他们合理地设计了第一座现代炼油厂。石油工业第一次大 量聘请化学工程师的繁荣时代开始
了。

During this period of intensive development of unit operations, other classical tools of chemical engineering analysis were
introduced or were extensively developed. These included studies of the material and energy balance of processes and fundamental


thermodynamic studies of multicomponent systems.
在单元操作密集繁殖的时代,化学工程学另一些经典的分析手段也开始被引入或广泛 发展。这包括过程中材料和能量平衡
的研究以及多组分体系中基础热力学的研究。

Chemical engineers played a key role in helping the United States and its allies win World War Ⅱ. They developed routes to
synthetic rubber to replace the sources of natural rubber that were lost to the Japanese early in the war. They provided the uranium-235
needed to build the atomic bomb, scaling up the manufacturing process in one step from the laboratory to the largest industrial plant that
had ever been built. And they were instrumental in perfecting the manufacture of penicillin, which saved the lives of potentially
hundreds of thousands of wounded soldiers.
化学工程师在帮助美国及其盟国赢得第二次世界大战的胜利中起 了关键的作用。他们发展了合成橡胶的方法以代替在战争
初期因日本的封锁而失去来源的天然橡胶。他们 提供了制造原子弹所需要的铀-235,把制造过程从实验室研究一步放大到当时
最大规模的工业化工厂 ,而他们在完善penicillin的生产工艺中也是功不可没,它挽救了几十万受伤士兵的生命。

The Engineering Science Movement. Dissatisfied with empirical descriptions of process equipment performance, chemical
engineers began to reexamine unit operations from a more fundamental point of view. The phenomena that take place in unit operations
were resolved into sets of molecular events. Quantitative mechanistic models for these events were developed and used to analyze
existing equipment. Mathematical models of processes and reactors were developed and applied to capital-intensive U.S. industries such
as commodity petrochemicals.
工程学运动。由于 不满意对工艺设备运行的经验描述,化学工程师开始从更基础的角度再审视单元操作。发生在单元操作
中 的现象可以分解到分子运动水平。这些运动的定量机械模型被建立并用于分析已有的仪器设备。过程和放应器的数 学模型也
被建立并被应用于资金密集型的美国工业如石油化学工业。

Parallel to the growth of the engineering science movement was the evolution of the core chemical engineering curriculum in its
present form. Perhaps more than any other development, the core curriculum is responsible for the confidence with which chemical
engineers integrate knowledge from many disciplines in the solution of complex problems.
与工程学同时发展的是现在的化学工程课程设置的变化。也许与 其它发展相比较,核心课程为化学工程师运用综合技能解
决复杂问题更加提供了信心。

The core curriculum provides a background in some of the basic sciences, including mathematics, physics, and chemistry. This
background is needed to undertake a rigorous study of the topics central to chemical engineering, including:
核心 课程固定了一些基础科学为背景,包括数学,物理,和化学。这些背景对于从事以化学工程为中心的课题的艰苦研 究
是必须的,包括:

·Multicomponent thermodynamics and kinetics,
·Transport phenomena,
·Unit operations,
·Reaction engineering,
·Process design and control, and
·Plant design and systems engineering.
·多组分体系热力学及动力学
·传输现象
·单元操作
·反应工程
·过程设计和控制
·工厂设计和系统工程

This training has enabled chemical engineers to become leading contributors to a number of interdisciplinary areas, including


catalysis, colloid science and technology, combustion, electro- chemical engineering, and polymer science and technology.
这种训练使化学工程师们成为了在许多学科领域做出了突出贡献的人,包括在 催化学、胶体科学和技术、燃烧、电化学工
程、以及聚合物科学和技术方面。

2. Basic Trends In Chemical Engineering
Over the next few years, a confluence of intellectual advances, technologic challenges, and economic driving forces will shape a
new model of what chemical engineering is and what chemical engineering do.
2. 化学工程学的基本发展趋势
未来几年里,科 学的进步,技术的竞争以及经济的驱动力将为化学工程是什么以及化学工程能做什么打造一个新的模型。

The focus of chemical engineering has always been industrial processes that change the physical state or chemical composition of
materials. Chemical engineers engage in the synthesis, design, testing scale-up, operation, control and optimization of these processes.
The traditional level of size and complexity at which they have worked on these problems might be termed the mesoscale. Examples of
this scale include reactors and equipment for single processes (unit operations) and combinations of unit operations in manufacturing
plants. Future research at the mesoscale will be increasingly supplemented by dimensions—the microscale and the dimensions of
extremely complex systems—the macroscale.
化学工程学的焦点一直是改变物 体的物理状态或化学性质的工业过程。化学工程师致力于这些过程的合成、设计、测试
放大、操作、控制 和优选。他们从事于解决的这些问题,传统的规模水平和复杂程度可称之为中等的,这种规模的例子包括有
单个过程(单元操作)所使用的反应器和设备以及制造厂里单元操作的组合,未来的研究将在规模上逐渐进行补 充。除了中等
规模,还有微型的以及更为复杂的系统----巨型的规模。

Chemical engineers of the future will be integrating a wider range of scales than any other branch of engineering. For example,
some may work to relate the macroscale of the environment to the mesoscale of combustion systems and the microscale of molecular
reactions and transport. Other may work to relate the macroscale performance of a composite aircraft to the mesoscale chemical reactor
in which the wing was formed, the design of the reactor perhaps having been influenced by studies of the microscale dynamics of
complex liquids.
未来 的化学工程师将比任何其他分支的工程师在更为宽广的规模范围紧密协作。例如,有些人可能从事于了解大范围的
环境与中等规模的燃烧系统以及微型的分子水平的反应和传递之间的关系。另一些人则从事了解合成的飞 机的的性能与机翼所
用化学反应器及反应器的设计和对此有影响的复杂流体动力学的研究工作。

Thus, future chemical and engineers will conceive and rigorously solve problems on a continuum of scales ranging from
microscale. They will bring new tools and insights to research and practice from other disciplines: molecular biology, chemistry,
solid-state physics, materials science, and electrical engineering. And they will make increasing use of computers, artificial intelligence,
and expert system in problem solving, in product and process design, and in manufacturing.
因此,未来的化学工程师们要准备好解决从微型的到巨 型的规模范围内出现的问题。他们要用来自其它学科的新的工具
和理念来研究和实践:分子生物学,化学 ,固体物理学,材料学和电子工程学。他们还将越来越多地使用计算机、人工智能以
及专家系统来解决问 题,进行产品和过程设计,生产制造。

Two important development will be part of this unfolding picture of the discipline.
Chemical engineers will become more heavily involved in product design as a complement to process design. As the properties of
a product in performance become increasingly linked to the way in which it is processed, the traditional distinction between product and
process design will become blurred. There will be a special design challenge in established and emerging industries that produce
proprietary, differentiated products tailored to exacting performance specifications. These products are characterized by the need for
rapid innovatory ad they are quickly superseded in the marketplace by newer products.
在这个学科中还有两个重要的发展是我们前面没有提到的:
化学工程师将越来越多地涉及到对 过程设计进行补充的产品设计中。因为产品所表现出来的性能将逐渐与它被加工的途
径挂钩。传统概念上 产品设计与过程设计之间的区别将变得模糊,不再那么明显。在已有的和新兴的工业中将出现一个特殊的


设计竞争,那就是生产有专利权的、有特点的产品以适应严格的性能指标。这些产品的特征是服从 快速革新的需要,因而他们
将在市场上很快地被更新的产品所取代。

Chemical engineers will be frequent participants in multidisciplinary research efforts. Chemical engineering has a long history of
fruitful interdisciplinary research with the chemical sciences, particularly industry. The position of chemical engineering as the
engineering discipline with the strongest tie to the molecular sciences is an asset, since such sciences as chemistry, molecular biology,
biomedicine, and solid-state physics are providing the seeds for tomorrow’s technologies. Chemical engineering has a bright future as
the “interfacial discipline”, that will bridge science and engineering in the multidisciplinary environments where these new technologies
will be brought into being.
化学工程师将经常性地介入到多学科领域的研究工程 。化学工程师参与跨学科研究与化学科学、特种工业进行合作具有
悠久的历史。随着工程学与分子科学最 紧密地联系在一起,化学工程学的地位也越来越崇高。因为如化学、分子生物学、生物
医学以及固体物理 这样的科学都是为明天的科学技术提供种子,作为“界面科学”,化学工程学具有光明的未来,它将在多学
科领域中搭建科学和工程学之间的桥梁,而在这里将出现新的工业技术。






















Unit 11 Chemical and Process Thermodynamics
化工热力学
在投入大量的时间和精力去研究一个学科时,有理由去问一下以下两个问题:该学科是什
么?(研究)它有何用途?关于热力学,虽然第二个问题更容易回答,但回答第一个问题有必
要对该学科较深入的理解。(尽管)许多专家或学者赞同热力学的简单而准确的定义的观点(看
法)值得怀疑,但是还是有必要确定它的定义。然而,在讨论热力学的应用之后,就可以很容
易完成其定义
1.热力学的应用
热力学有两个主要的应用,两者对化学工程师都很重要。
(1)与过程相联系的热效应和功效应的计算,以及从过程得到的最大功或驱动过程所需
的最小功的计算。
(2)描述处于平衡的系统的各变量之间的关系的确定。


第一种应用由热力学这个名词可联想到,热力学表示运动中的热。直接利用第一和第二定
律可完成许多(热效应和功效应的)计算。例如:计算压缩气体的功,对一个完整过程或某一
过程单元的进行能量衡算,确定分离乙醇和水混合物所需的最小功,或者(evaluate)评估一
个氨合成工厂的效率。
热力学在特殊体系中的应用,引出了一些有用的函数的定义以及这些函数和其它变量(如
压强、温度、体积和摩尔分数)关系网络的确定。实际上,在运用第一、第二定律时,除非用
于评价必要的热力学函数变化已经存在,否则热力学的第一种应用不可能实现。通过已经建立
的关系网络,从实验确定的数据可以计算函数变化。除此之外,
某一体系中变量的关系网络,可让那些未知的或者那些难以从变量(这些变量容易得到或较易
测量)中实验确定的变量得以计算。例如,一种液体的汽化热,可以通过测量几个温度的蒸汽
压和几个温度下液相和汽相的密度得以计算;某一化学反应中任一温度下的可得的最大转化
率,可以通过参与该反应的各物质的热量法测量加以计算。
2. 热力学的本质
热力学定律有这经验的基础或实验基础,但是在描述其应用时,依赖实验测量显得很明显
化学工程与工艺专业英语第十一单元化工热力学
2
(stand out 突出)。因此,热力学广义上可以定义为:拓展我们实验所得的体系知识的一种手
段(方法),或定义为:观察和关联一个体系的行为的基本框架。为了理解热力学,拥有实验
的观点有必要,因为,如果我们不能对研究的体系或现象做出物理上正确的评价,那么热力学
的方法就无意义。我们应该要经常问问如下问题:怎样测量这一特殊的变量?怎样计算以及从
哪一类的数据计算一个特殊的函数。
由于热力学的实验基础,热力学处理的是宏观函数或大量的物质的函数,这与微观的函
数恰恰相反,微观函数涉及到的是组成物质的原子或分子。宏观函数要么可以直接测量,要么
可以从直接测量的函数计算得到,而不需要借助于某一具体的理论。相反,尽管(while)微观
函数最终是从实验测量得以确定,但是它们的真实性取决于用于它们计算时的特殊理论的有效
性。因此,热力学的权威性在于:它的结果与物质的理论无关,倍受尊敬,为大家大胆地接受。
除了与热力学结论一致的必然性以外,热力学有着广泛的应用性。因此,热力学形成了许
多学科中的工程师和科学家的教育中不可分割的部分。尽管如此,因为每门科学都只局限于
(focus on)关于热力学方面的较少应用,所以其全貌常被低估。实际上,在明显的(可观察
到)可再现的平衡态中存在的任何体系,都服从与热力学方法。除了流体、化学反应系统和处
于相平衡(化学工程师对这些十分感兴趣)之外,热力学也成功适用于有表面效应的系统、受
压力的固体以及处于重力场、离心力场、磁场和电场的物质。
通过热力学,可以被确定用于定义和确定平衡的位能,并将之定量化。位能也可以确定一
个体系移动的方向以及体系达到的终态,但是不能提供有关到达终态所需要的时间的信息。因
此,时间不是热力学的变量,速度的研究已超出了热力学的范畴,或者除了体系接近平衡的极
限以外,速率的研究属于热力学的范畴。在这儿,速率的表达式应该在热力学上是连续的。
热力学定律建立于实验和观测基础之上的,这些实验和观测既不是最重要的,又不复杂。
同时,这些定律的本身是用相当普通语言加以描述的。然而,从这一明显的平淡的开始,发展
成为一个很大的结构,这种结构对人类思想归纳力做出了贡献。这在想象力丰富、严肃认真的
学生中成功地激发了敬畏(inspire awe),这使得Lewis 和Randall 将热力学视为科学的权威。
因为除了技术上的成功和结构的严密性,这个比喻选择很恰当,我们可观察到美妙之处(和宏
观体)。因此,毫无疑问,热力学的研究在学术上有价值的,智力上可以得到激发,同时,对
一些人来说,是一种很好的经历。
3. 热力学定律
第一定律. 热力学第一定律是能量守恒的简单的一种描述。如图3-1 所示,稳态时离开一
个过程的所有能量的总和必须与所进入该过程的能量总和相等。工程师在设计和操作各种过程
时绝对遵循质量和能量守恒定律。所不幸的是,就其本身而言,当试图评估过程的效率时,第


化学工程与工艺专业英语第十一单元化工热力学
3
一定律引起混淆不清。人们将能量守恒视为一种重要的努力成果,但是事实上,使能量守恒不
需要花任何努力— — 能量本身就是守恒的。
因为第一定律没有区分各种各样能量的形式,所以从第一定律所得到的结论是有限的。由
往复泵引入的轴功会以热量流向冷凝器的形式离开蒸馏塔,与在再沸器引入的热一样容易。在
试图确定过程的效率时,一些工程师总掉入将各种形式的能量一起处理的陷阱。这种做法明显
是不合理,因为各种能量形式有着不同的费用。
第二定律第二定律应用于热转变为功的循环,有多种不同的描述。至于这一点,一种更
加普通的描述是需要的:从一种形式的能量到另一种形式的能量的转换,总是导致质量上总量
的损失。另一种描述为:所有系统都有接近平衡(无序)的趋势。这些表达方式指出了在表达
第二定律时的困难之处。如果不定义另一个专门描述质量或无序的词语,第二定律的表达就不
能令人满意。
这个专用名词为熵。这个状态函数对流体、物质或系统中的无序程度进行了定量化。绝对
零熵值定义绝对零度时纯净的、晶体固体的状态。每一个分子都由其他的以相当有序结构的相
同的分子所包围。运动、随意、污染、不确定性,这一切都增加了混乱度,因此对熵做出了贡
献。相反,不论是透明宝石,还是纯净化学产品,还是清洁的生活空间,还是新鲜的空气和水,
(都是属于有序状态),有序是有价值的。有序需要付出很高的代价,只有通过做功才得以实
现。我们很多工作都花费在家里、车间和环境中创造或恢复有序状态。环境中较高的熵值是较
高的生产费用的具体化表现。
每一种生产过程的目的都是,利用将混合物分离为纯净物、减小我们知识的不确定性、或
是从原料创造(works of art)艺术品以减小熵值。总之,从将原料转变为产品的过程中,熵值
不断减小。然而,(inasmuch as)因为随着系统接近平衡,熵的增加是自发的趋势,所以减少
熵值是艰难的工作(struggle)。
生产过程所需熵减的驱动力同时伴随着宇宙其余部分熵的剧增。一般说来,这种熵的增加
在同一工厂内不断持续下去,因此这种造成了产品熵的减小。反过来(whereas 而,却,其实,
反过来),熵减存在于原料向产品的转化过程。燃料、电、空气以及水向燃烧产品、废水和无
用的热量的形式的转化可表示熵值的大大增加。
正象图3-1 中中间部分描述为第一定律一样,图中的底线部分描述了第二定律。离开一个
过程的所有的物流的熵值的总和,总是超过进入该过程的物流的熵值的总和。如果熵达到平衡,
象质量和能量达到平衡一样,那么该过程是可逆的,即该过程也会反向移动。可逆过程只是在
理论上是可能的,需要动力学平衡维持连续存在,因此可逆过程是不可产生的。而且,如果不
化学工程与工艺专业英语第十一单元化工热力学
4
平衡(过程)倒过来,即如果有净熵的减少,那么所有的箭头也要反向,该过程被迫反向进行。
实质上,是熵增驱使该过程:是同一种驱动力使水向下流,热流从热物质流向冷物质,使玻璃
打碎,金属腐蚀。简而言之,所有事物都同它们周围的环境接近平衡。
第一定律,需要能量守恒,所有形式能量变化有着相同的重要性。尽管所有过程都受第一
定律权威性的影响,但是该定律不能区分能量的质量,也不能解释为什么观察不到自发发生的
过程自发地使自身可逆。功可以全部转化为热而反向转换从来不会定量发生,这种反复验证过
的观测达成了这样的共识— — 热是一种低质量的能量。第二定律,深深扎根于热发动机效率的
研究,能分辨能量的质量。通过这一定律,揭示了以前未认可的函数— — 熵的存在,可以看出,
该函数确定了自发变化的方向。第二定律并没有(in no way)减小第一定律的权威性;相反,
第二定律拓展和加强了热力学的权限。
第三定律热力学第三定律规定了熵的绝对零值,描述如下:对于那些处在绝对零度的完
美晶体的变化来说,总的熵的变化为零。该定律使用绝对值来描述熵。










Unit 12 what do we mean by transport phenomena ?
Transport phenomena is the collective name given to the systematic and integrated study of three classical areas of engineering
science : (i) energy or heat transport ,(ii) mass transport or diffusion ,and (iii) momentum transport or fluid dynamics . 传递现象是工程
科学三个典型领域系统性和综合性研究的总称:能 量或热量传递,质量传递或扩散,以及动量传递或流体力学。 Of course , heat
and mass transport occur frequently in fluids , and for this reason some engineering educators prefer to includes these processes in their
treatment of fluid mechanics . 当然,热量和质量传递在流体中经 常发生,正因如此一些工程教育家喜欢把这些过程包含在流体
力学的范畴内。Since transport phenomena also includes heat conduction and diffusion in solids , however , the subject is actually of
wider scope than fluid mechanics. 由于传递现象也包括固体中的热传导和扩散,因此,传递现象实际上比流体力学的领域更广。
It is also distinguished from fluid mechanics in that the study of transport phenomena make use of the similarities between the equations
used to describe the processes of heat,mass,and momentum transport. 传递现象的研究充分利用描述传热,传质,动量传递过程的
方程间的相似性,这 也区别于流体力学。These analogies,as they are usually called, can often be related to similarities in the physical
mechanisms whereby the transport takes place. 这些类推(通常被这么叫)常常可以与传递现象发生的物理机制间的相似性关联起
来。As a consequence,an understanding of one transport process can readily lead to an understanding of other processes. 因此,一个传
递过程的理解能够容易促使其他过程的理解。Moreover,if the differential equations and boundary conditions are the same,a
solution need be obtained for only one of the processes since by changing the nomenclature that solution can be used to obtain the
solution for any other transport process. 而且,如果微分方程和边界条件是一样的,只需获得一个传递过程的解决方案即可,因
为通过改变名称就 可以用来获得其他任何传递过程的解决方案。

It must be emphasized , however, that while there are similarities between the transport processes, there are also important
differences , especially between the transport of momentum (a vector ) and that of heat or mass (scalars ). 必须强调 ,虽然有相似之处,
也有传递过程之间的差异,尤其重要的是运输动量(矢量)和热或质量(标量). Nevertheless , a systematic study of the similarities
between the transport processes makes it easier to identify and understand the differences between them. 然而,系统地研究了相似性传
递过程之间的相似性,使它更容易识别和理解它们之间的差别。
1.How We Approach the Subject 怎么研究传递过程?

In order to demonstrate the analogies between the transport processes , we will study each of the process in parallel-instead of
studying momentum transport first , then energy transport , and finally mass transport. 为了找 出传递过程间的相似性,我们将同时研
究每一种传递过程——取代先研究动量传递,再传热,最后传质的 方法。 Besides promoting understanding , there is another
pedagogical reason for not using the serial approach that is used in other textbooks : of the three processes, the concepts and equations
involved in the study of momentum transport are the most difficult for the beginner to understand and to use . 除了促进理解之外,对
于不使用在其他教科书里用 到的顺序法还有另一个教学的原因:在三个过程中,包含在动量传递研究中的概念和方程对初学者
来说是 最难以理解并使用。Because it is impossible to cover heat and mass transport thoroughly without prior knowledge of
momentum transport ,one is forced under the serial approach to take up the most difficult subject (momentum transport) first . 因为在
不具有有关动量传递的知识前提下一个人不可能完全理解传热和传质,在顺序法的情况下他就被迫先研究 最难的课程即动量传
递。On the other hand ,if the subjects are studied in parallel , momentum transport becomes more understandable by reference to the
familiar subject of heat transport. 另一方面,如果课程同 时被研究,通过参照有关传热的熟悉课程动量传递就变得更好理解。
Furthermore ,the parallel treatment makes it possible to study the simpler the physical processes that are occurring rather than the
mathematical procedures and representations. 而且,平行研究法可以先研究较为简单的概念,再深入到较难和较抽象的概 念。我
们可以先强调所发生的物理过程而不是数学性步骤和描述。 For example ,we will study one-dimensional transport phenomena


first because equations instead of partial requiring vector notation and we can often use ordinary differential equations instead of partial
differential equations ,which are harder to solve . 例如,我们将先研究一维传递现象,因为它在不要求矢量标注下就可以被 解决,
并且我们常常可以使用普通的微分方程代替难以解决的偏微分方程。 This procedure is also justified by the fact that many of the
practical problems of transport phenomena can be solved by one-dimensional models. 加上传递现象的许多实际问题可以通过一维
模型解决的这样一个事实,这种处理做法也是合理的。
Should Engineers Study Transport Phenomena? 为什么工程师要研究传递现象?

Since the discipline of transport phenomena deals with certain laws of nature , some people classify it as a branch of engineering .
因为传递现象这个学科牵扯到自然界定则,一些人就把它划分为工程的一个分支。 For this reason the engineer , who is concerned
with the economical design and operation of plants and equipment , quite properly should ask how transport phenomena will be of value
in practice . 正因如此,对于那些关心工厂和设备设计和操作经济性的工程师而言,十分应该探知在实 际中传递现象如何起到价
值作用。There are two general types of answers to those questions . 对于那些问题有两种通用型答案。The first requires one to
recognize that heat ,mass ,and momentum transport occur in many kinds of engineering , e.g., heat exchangers ,compressors ,nuclear
and chemical reactors, humidifiers, air coolers ,driers , fractionaters , and absorbers. 第一种要求大家认识到传热,传质和动量传递发
生在许多工程设备中, 如热交换器,压缩机,核化反应器,增湿器,空气冷却器,干燥器,分离器和吸收器。These transport processes
are also involved in the human body as well as in the complex processes whereby pollutants react and diffuse in the atmosphere. 这些
传递过程也发生在人体内以及大气中污染物反应和扩散的一些复杂过程中。It is important that engineers have an understanding of
the physical laws governing these transport processes if they are to understand what is taking place in engineering equipment and to
make wise decisions with regard to its economical operation . 如果工程师要知道工程设备中正在发生什么并要做出能达到经济性
操作的决策 ,对主导这些传递过程的物理定律有一个认识很重要。

The second answer is that engineers need to be able to use their understanding of natural laws to design process equipment in
which these processes are occurring . 第二种答案是工程师需要能够运用自然定律的知识设计包含这些过程的工艺设备。To do so
they must be able to predict rates of heat ,mass , or momentum transport . 要做到这点,他们必须能够预测传热,传质,或动量传递
速率。For example, consider a simple heat exchanger , i.e., a pipe used to heat a fluid by maintaining its wall at a higher temperature
than that of the fluid flowing through it . 例如,考虑一个简单的热交换器,也就是一根管道——通过维持壁 温高于流经管道的流
体温度来加热流体。The rate at which heat passes from the wall of the pipe to the fluid depends upon a parameter , etc. 热量从管壁传
递到流体的速率取 决于传热系数,传热系数反过来取决于管的大小,流体流速,流体性质等。Traditionally heat-transfer
coefficients are obtained after expensive and time-consuming laboratory or pilot- plant measurements and are correlated through the use
of dimensionless empirical equations. 传统上传 热系数是在耗费和耗时的实验室或模范工厂的测量之后获得并且通过使用一维经
验方程关联起来。Emp irical equations are equations that fit the data over a certain range; they are not based upon theory and cannot be
used accurately outside the range for which the data have heen taken . 经验方 程是适合一定数据范围的方程,它们不是建立在理论
基础上而且在应用数据的范围外不能被精确使用。

The less expensive and usually more reliable approach used in transport phenomena is to predict the heat-transfer coefficient
from equations based on the laws of nature . 使用在传递现象中比较 不耗费和通常较为可靠的方法是从以自然定律为基础的方程
中预测传热系数。The predicted result would be obtained by a research engineer by solving some equations (often on a computer ). 预
测的结果将由一个研究工程师通过解一些方程获得(常常在电脑上)A design engineer would then use the equation for the
heat-transfer coefficient obtained by the research engineer . 设计工程师再使用由研究工程师获得的关于传热系数的方程。

Keep in mind that the job of designing the heat exchanger would be essentially the same no matter how the heat-transfer
coefficients were originally obtained. 要记住无论传热系数是怎么得来的设计热交换器的工作将基本上是一样的。For this
reason ,some courses in transport phenomena emphasize only the determination of the heat- transfer coefficient and leave the actual
design procedure to a course in unit operations . 正因如此,传递现象的一些课程只强调传热系数的决定而把真正的设计步骤留给单元操作中的一个课程。It is of cource a “practical “ matter to be able to obtain the parameters , i.e., the heat-transfer coefficients that
are used in design , and for that reason a transport phenomena course can be considered an engineering course as well as one in science .
当然,能获得参数也就是设计中使用的传热系数 是事实,并正因此,一个传递现象课程可被视为一个工程课程或一个科学课程。



In fact , there are some cases in which the design engineer might use the methods and equations of transport phenomena directly
in the design of equipment . 实际上,在设备设计中有一些情况下设计工程师可能直接使用传递现象的方法和方程。An example
would be a tubular reactor ,which might be illustrated as a pipe ,e.g., the heat exchanger described earlier, with a homogeneous chemical
reaction occurring in the fluid within . 一种情况就 是设计可以被称为管道的管式反应器,如,前面所提过的热交换器,在它里面
的液相中发生着一个均相化 学反应。The fluid enters with a certain concentration of reactant and leaves the tube with a decreased
concentration of reactant and an increased concentration of product . 流体以一定浓度的反应物流进并以浓度降低的反应物和浓度
增加的产物流出反应管。

If the reaction is exothermic , the reactor wall will usually be maintained at a low temperature in order to remove the heat
generated by the chemical reaction . 如果反应是放热的, 为了移除化学反应生成的热量反应器壁通常维持在一个低的温度。
Therefore the temperature will decrease with radial position , i.e.,with the distance from the centerline of the pipe . 因此沿径向方向也
就是说随离管道中心线距离的增大,温度降低。 Then , since the reaction rate increases with temperature , it will be higher at the
center ,where the temperature is high , than at the wall , where the temperature is low . 再者,因为反应速率随温度升高而增大,在温
度高的中心 处的反应速率高于温度低的管壁处的反应速率。Accordingly ,the products of the reaction will tend to accumulate at the
centerline while the reactants accumulate near the wall of the reactor . 结果,反应产物将倾向于在中心线处积累而反应物在靠近管
壁处积累。 Hence , concentration as well as temperature will vary both with radial position and with length . 因此,沿径向和横向浓
度和温度都将改变。To design the reactor we would need to know ,at any given length , the mean concentration of product . 为了设计
反应器我们需要知道在任意给定的管长下产物的平均浓度。Since this mean concentration is obtained from the point values
averaged over the cross section , we actually need to obtain the concentration at every point in the reactor , i.e., at every radial position
and at every length . 由于这个平均浓度是将整个反应器内每个点的浓度平均 起来得到的,实际上我们需要得到反应器内每个点
的浓度,也就是说,在每个径向和横向位置。But to calculate the concentration at every point we need to know the reaction rate at
every point , and to calculate the rate at every point we need to know both the temperature and the concentration at every point ! 但是
为了计算每个点的浓度我们需要知道每个点处的反应速率,而 为了计算每个点处的速率我们需要知道温度和浓度!
Furthermore, to calculate the temperature we also need to know the rate and the velocity of the fluid at every point . 而且,为了计算
温度我们也要知道每个点处的反应速率和速度。We will not go into the equations involved ,but obviously we have a complicated set
of partial differential equations that must be solved by sophisticated procedures, usually on a computer. 我们将不得到所包含的方程,但显然有一组必须由精细繁琐的步骤解决的复杂偏微分方程(通常在电脑上)。It should be apparent that we could not handle such
a problem by the empirical design procedures used in unit operations courses for a heat exchanger . 我们不 能通过用于单元操作课程
中关于热交换器的经验设计步骤来解决这样一个问题,应该是明显的。Inst ead the theory and mathematical procedures of transport
phenomena are essential ,unless one wishes to go go the expense and take the time to build pilot plants of increasing size and measure
the conersion in each . 然而传递现象的理论和数学步骤是必不可少的,除 非一个人愿意花金钱和时间去建立规模不断扩大的模
范工厂并测出每一个工厂的产率。 Even then the final scale-up is precarious and uncertain.即便最后的扩大规模是靠不住和不确
定的。

Of course ,not all problems today can be solved by the methods of transport phenomena. 当然,并非今天所有的问题都能通过
传递现象的方法解决。However, with the development of the computer ,more and more problems are being solved by these methods .
然而,随着电脑科技的发展,越来越多的问题通过这些方法正被解决。If engineering students are to have an education that is not
become obsolete , they must be prepared, through an understanding of the methods of transport phenomena , to make use of the
computations that will be made in the future . 如果工程学学生要得到一个不过时的教育,他们必须通过理解传递现象的方法准备
好去充分利用将在未来 形成的计算机计算。Because of its great potential as well as its current usefulness , a course in transport
phenomena may ultimately prove to be the most practical and useful course on a student’s undergraduate career. 由于其极大的潜能及
当前的实用性,在一个大学生的在 校学习生涯中,传递现象这门课程或许最终证明是最实用和有用的课程。

Unit 13 Unit Operations in Chemical Engineering
化学工程中的单元操作
化学工程由不同顺序的步骤组成,这些步骤的原理与被操作的物


料以及该特殊体系的其他特征无关。在设计一个过程中,如果(研究)
步骤得到认可,那么所用每一步骤可以分别进行研究。有些步骤为化
学反应,而其他步骤为物理变化。化学工程的可变通性(versatility)
源于将一复杂过程的分解为单个的物理步骤(叫做单元操作)和化学
反应的实践。化学工程中单元操作的概念基于这种哲学观点:各种不
同顺序的步骤可以减少为简单的操作或反应。不管所处理的物料如何,
这些简单的操作或反应基本原理(fundamentals)是相同的。这一原理,
在美国化学工业发展期间先驱者来说是明显的,首先由 于
1915 年明确提出:
任何化学过程,不管所进行的规模如何,均可分解为(be resolved
into)一系列的相同的单元操作,如:粉碎、混合、加热、烘烤、吸
收、压缩、沉淀、结晶、过滤、溶解、电解等等。这些基本单元操作
(的数目)为数不多,任何特殊的过程中包含其中的几种。化学工程
的复杂性来自于条件(温度、压力等等)的多样性,在这些条件下,
单元操作以不同的过程进行,同时其复杂性来自于限制条件,如由反
应物质的物化特征所规定的结构材料和设备的设计。
最初列出的单元操作,引用的是上述的十二种操作,不是所有的
操作都可视为单元操作。从那时起,确定了其他单元操作,过去确定
的速度适中,但是近来速度加快。流体流动、传热、蒸馏、润湿、气
体吸收、沉降、分粒、搅拌以及离心得到了认可。近年来,对新技术
的不断理解以及古老但很少使用的分离技术的采用,引起了分离、处
理操作或生产过程步骤上的数量不断增加,在多种操作中,这些操作
步骤在使用时不要大的改变。这就是“单元操作”这个术语的基础,此基础为我们提供了一系列的技术。
1.单元操作的分类
(1)流体流动流体流动所涉及到的是确定任何流体的从一位
置到另一位置的流动或输送的原理。
(2)传热该单元操作涉及到(deal with)原理为:支配热量
和能量从一位置到另一位置的积累和传递。
(3)蒸发这是传热中的一种特例,涉及到的是在溶液中挥发
性溶剂从不挥发性的溶质(如盐或其他任何物质)的挥发。
(4)干燥在该操作中,挥发性的液体(通常是水)从固体物
质中除去。
(5)蒸馏蒸馏是这样一个操作:因为液体混合物的蒸汽压强
的差别,利用沸腾可将其中的各组分加以分离。
(6)吸收在该操作中,一种气流经过一种液体处理后,其中
一种组分得以除去。
(7) 膜分离该操作涉及到液体或气体中的一种溶质通过半
透膜向另一种流中的扩散。
(8)液-液萃取在该操作中,(液体)溶液中的一种溶质通过
与该溶液相对不互溶的另一种液体溶剂相接触而加以分离。
(9)液-固浸取在该操作所涉及的是,用一种液体处理一种
细小可分固体,该液体能溶解这种固体,从而除去该固体中所含的溶
质。
(10) 结晶结晶涉及到的是,通过沉降方法将溶液中的溶质
(如一种盐)从该溶液中加以分离。
(11)机械物理分离这些分离方法包括,利用物理方法分离固
体、液体、或气体。这些物理方法,如过滤、沉降、粒分,通常归为


分离单元操作。
许多单元操作有着相同的基本原理、基本原则或机理。例如,扩
散机理或质量传递发生于干燥、吸收、蒸馏和结晶中,传热存在于干燥、蒸馏、蒸发等等。
2. 基本概念
因为单元操作是工程学的一个分支,所以它们同时建立在科学研
究和实验的基础之上。在设计那些能够制造、能组合、能操作、能维
修的设备时,必须要将理论和实践结合起来。下面四个概念是基本的
(basic),形成了所有操作的计算的基础。
物料衡算
如果物质既没有被创造又没有被消灭,除了在操作中物质停留和
积累以外,那么进入某一操作的所有物料的总质量与离开该操作的所
有物料的总质量相等。应用该原理,可以计算出化学反应的收率或工
程操作的得率。
在连续操作中,操作中通常没有物料的积累,物料平衡简单地由
所有的进入的物料和所有的离开的物料组成,这种方式与会计所用方
法相同。结果必须要达到平衡。
只要(as long as)该反应是化学反应,而且不消灭或创造原子,
那么将原子作为物料平衡的基础是正确的,而且常常非常方便。可以
整个工厂或某一单元的任何一部分进行物料衡算,这取决于所研究的
问题。
能量恒算
相似地,要确定操作一操作所需的能量或维持所需的操作条件时,
可以对任何工厂或单元操作进行能量衡算。该原理与物料衡算同样重
要,使用方式相同。重要的是记住,尽管能量可能会转换为另一种等
量形式,但是要把各种形式的所有的能量包括在内。
理想接触(平衡级模型)
无论(whenever)所处理的物料在具体条件(如温度、压强、化
学组成或电势条件)下接触时间长短如何,这些物料都有接近一定的
平衡条件的趋势,该平衡由具体的条件确定。在多数情况下,达到平
衡条件的速率如此之快或所需时间足够长,以致每一次接触都达到了
平衡条件。这样的接触可视为一种平衡或一种平衡接触。理想接触数
目的计算是理解这些单元操作时所需的重要的步骤,这些单元操作涉
及到物料从一相到另一相的传递,如浸取、萃取、吸收和溶解。
操作速率(传递速率模型)
在大多数操作中,要么是因为时间不够,要么是因为不需要平衡,
因此达不到平衡,只要一达到平衡,就不会发生进一步变化,该过程
就会停止,但是工程师们必须要使该过程继续进行。由于这种原因,
速率操作,例如能量传递速率、质量传递速率以及化学反应速率,是
极其重要而有趣的。在所有的情况中,速率和方向决定于位能的差异
或驱动力。速率通常可表示为,与除以阻力的压降成正比。这种原理
在电能中应用,与用于稳定或直流电流的欧姆定律相似。
用这种简单的概念解决传热或传质中的速率问题时,主要的困难
是对阻力的估计,阻力一般是通过不同条件下许多传递速率的确定式
(determination)的经验关联式加以计算。
速率直接地决定于压降,间接地决定于阻力的这种基本概念,可
以运用到任一速率操作,尽管对于特殊情况的速率可以不同的方式用特殊的系数来表达。













Unit 14 Distillation

第十四单元 蒸馏




利用生成两个或更多的共存区域(它们在温度、压强,组成和或相态有差别),分离操作 实现了它们的分离目标。混合
物中欲分离的各种分子以独特的方式在由这些共存区域提供的环 境中反应。结果,随着体系向平衡移动,每个区域各种分子
有着不同的浓度,这样便可将物种 进行分离。

叫做蒸馏的分离操作,利用的是共存区中温度和压强基本相同的气相和液相。各种装置(如 乱堆填料或归整填料和塔
板)用来引起两相亲密接触。塔板一个接一个堆积,被包围在一个圆 柱型的壳中形成塔,通常,圆柱壳中的压板和支板间有
填料。

1. 连续蒸馏

进料(原料),即要被分离为多种成分的物料,在沿着塔壳上的一个位置或多位置引入
introduce

。由于气相与液相间
重力的差异,液体从蒸馏塔 往下流动,像瀑布一样从一塔板

流向另一塔板,而气体向上流动,结果在每一塔板上与液体相接
触。

到达塔底的液体,在已经加热过的再沸器中部分汽化以提供蒸汽,这些蒸汽被送回蒸馏塔 中。塔底液体的剩余部分以
塔底产物加以回收。到达塔顶的气体在塔顶冷凝器中,经冷却、压 缩成为液体。部分液体以回流的形式重新返回蒸馏塔中,
以提供液体溢流。塔顶气流剩余部分 以蒸馏物或塔顶产物的形式加以回收。

蒸馏塔中这种整体的流动方式,使得蒸流和液体流在蒸馏塔中所有塔板上对流接触。在给 定的塔板上,气相和液相达
到一定程度的热、压强以及组成平衡,其平衡的程度取决于接触塔 板的效率。

较轻组分(沸点低的组分)倾向于在气相中浓缩,而较重组分(沸点高的组分)倾向于在 液相中浓缩。这样造成的结
果是,随着气相从蒸馏塔自下向上流动时,形成了轻组分更加富集 的气相,同时随着液相(从蒸馏塔自上)向下流动时,形
成重组分更加富集的液相。在蒸馏出 物和塔底产物间所实现的总分离主要决定于组分间的相对挥发度、接触塔板的数目以及
液相流 速与气相流速间的比率。


如果进料(原料)在蒸馏塔的壳上的一个位置引入,那么该蒸馏塔分成上下两部分:上半 部分常称为蒸馏段

rectifying
section

,而下半部分常称为提馏段

stripping section

。这种说 法在多口进料的蒸馏塔和某些塔中相当不确切,这些塔中除了
两种最终产物以外,一种产物即 侧线馏分

sidestream

沿着蒸馏塔的长度方向上某些位置加以回收。

平衡级概念 在实际的蒸馏塔中,能量与质量 传递过程太复杂而不能以任何直接的形式容易地建立模型中。这种困难可以用
平衡级模型
equilibrium-stage model

加以回避,在平衡 级模型中,离开平衡级的气相和液相彼此间达到完全平衡,在一定
压力下热力学关系式也可用 于确定平 衡气流

stream

的温度和关联其浓度。由平衡级(而不是实际的塔板 )组成的假设 的
蒸馏塔用于完成实际蒸馏塔的分离。利用塔板效率

tray efficiency

可将理论平衡级的数目 可以转化为大量的实际塔板,塔
板效率描述的是:实际接触塔板的性能重复平衡级性能的程度。

利用平衡级概念可将蒸馏塔的设计分成三个主要的步骤:(1)整理预计平衡相组成所需的 热力学数据和方法。(2)计
算要实现某一具体分离所需要平衡级数目,或者在给定平衡级数目 下,计算欲实现的分离。(3)平衡级的数目转化为等数
目的实际接触塔板或填料高度,以及确 定蒸馏塔的直径。

所有的分离操作都需要以热或功的形式进行能量输入。在常见的蒸馏操作中,分离物质所 需的能量,在塔底的再沸器
中以热量的形式输入,在蒸馏塔的底部处的温度最高。同样,热量 从塔顶处的冷凝器中移走,此处的温度最低。这通常(引
起)需要大量的能量输入,(引起) 总热力学效率低。随着近来能量费用的剧增,正在开发出一些复杂的蒸馏操作,这些复
杂的蒸 馏操作能 提供较高的热力学效率和能量输入要求

requirement

较低。

相关的分离操作 刚刚所介绍的简单的和复杂的整流操作有两个共同点:(1)两者都提 供精馏段和提留段,以致能实
现挥发度较接近的两组分的分离;(2)分离操作仅受能量的输入 和输出的影响,而不受任何质量分离剂(如在液-液萃取剂
中)分离到的加入的影响。有时, 在图 3-2 的所示的分离操作的类型中,选择一个的单级或多级气-液分离操作,对某一具
体的 分离任务来说可能较蒸馏更合适。
2. 间歇蒸馏

间歇蒸馏,是将一具体量的液体分离成产物的过程,广泛应用于实验室中和适用于多种混 合物分离的小的生产单元。
当进料中有 N 种组成时,一个间歇蒸馏塔可以满足要求,而(若 用连续蒸馏,则)需要 N-1 种简单的连续蒸馏塔(才能
满足要求)。

图 3-2 与蒸馏相关的分离操作

间歇蒸馏器的特征是许多装置较大。要分离的物料中固体含量可能很高,或者物料含有能 塞住或污染连 续装置的焦油
或树脂。利用间歇单元可保持

keep

分离的固体 ,使之在过程结 束时得以方便分离。

简单的间歇蒸馏 间歇蒸馏器最简单的形式包括一个热的容器(锅或沸腾器),一个冷凝 器和一个或多个接受槽。不需
要塔板或填料。原料加入到容器内,使之沸腾。蒸汽经冷凝,在 接收器收集。不需要回流。有时,控制蒸发的速度以防进
料暴沸,以及避免使冷凝器的负荷太 重,但其他控制可以忽略不计。该过程常常称为 Rayleigh 蒸馏。

该简单间歇蒸 馏只提供一块分离理论塔板。其应用常常局限于产品需要另外分离的初步工作中,此时易挥发组分在进一步处理< br>之前,绝大部分易挥发组分必须通过间歇蒸馏加以除去, 或者是用于

similar

不重要的分离中。


含有精馏的间歇蒸馏 为了得到较窄组成范围的产品,常利用含有精馏的间歇蒸馏器, 该间歇蒸馏器由一个釜(或再沸
器)、一个精馏塔和一个冷凝器(用部分冷凝气体(馏出物) 作为回流液)以及一个或多个接收器组成。为了使回流液在或接
近蒸馏塔温度返回,以使之为 回流液量真正显示和改善蒸馏塔的操作,要控制馏出液的温度。该蒸馏塔也可以在高压或真空 下
操作,此时,必须要用适当的装置以得到所需的压力。除了蒸馏釜的设计之外,间歇蒸馏各 部分设备的设计方法,遵循的原
则都与设计连续装置的原则相同,但是如果要处理多种混合物, 那么应该检查该设备以适合每一种混合物。因为蒸馏塔中的
组成随着蒸馏的进行而改变,因此, 要在一种混合物的多种位置检验该设计。蒸馏釜的设计是以间歇操作的规模和所需的蒸
发速率 为基础的。
在操作时,一批量的液体加入蒸馏釜中,该体系达到总回流下的稳定状态。根据已确定的 回流方法

policy

,一部分塔
顶冷凝液不断得到回收。当操 作条件改变时,通过改变接收器可 得到多种馏分。整个蒸馏塔是富含组分部分。随着时间的进
行,蒸馏的物料的组成中较易挥发 的组分浓 度越来越小,当所收集的馏出液达到所需的平均组成时,馏分

cut

的蒸 馏会停
止。

间歇蒸馏的过程可以用几种方式加以控制:

(< br>1
)(保持)回流比不变,改变塔顶组成。
将回流(比)确定在一定值,在运转时回流( 比)

保持在该值不变。因为
蒸馏釜中液体的组成不断改变,馏出液的瞬时组成也改变。蒸馏一直进 行到蒸馏液的平均组成达到所需的值为止。在二元组
分情况下,塔顶产物转移到另一个接收器 中,同时直到剩余的釜液满足所需的要求时,回收中间馏分。中间馏分常常加入到
下一批物料 中。对于多组分混合物来说,在产物馏分间要取出两种或更多的中间馏分。


2< br>)(保持)塔顶组成不变,而改变回流比。
在双组合体系中,如果要保持塔顶组成不变,

那么返回蒸馏塔的回流量,
再运转过程中必须是不断增加。随着时间进行,蒸馏釜中较轻组分 不断减少。最后,达到这种情况:回流比达到非常高的值。
然后,改变接收器,减小回流比, 像以前一样取出中间馏分。该技术也能扩展到用于多组分的混合物。


3
)其它的控制方法。
一种循环方法可用来设置蒸馏塔的操作方式。该装置在达到平衡

以前都以全回流进行操作。在
短时间里,馏出物以放水的形式

total draw-off

取出,之后, 蒸馏塔又重新回到全回流操作。在蒸馏过程中不断重复这种循
环。另一种可能是:为了在最短 时间内实现所需的分离而优化回流比。复杂的操作可能包括侧线馏分的回收、提供中间冷凝
器、 加料至塔板,以周期性加料至蒸馏釜中。

Unit 15 Solvent Extrction,Leaching and Adsorption

第十五单元 溶剂萃取、浸取和吸附




1.溶剂萃取(液-液萃取)

用一种溶剂处理液体混合物,在该溶剂之中,一种或多种所需的组分能优先溶解,这种液 体混合物组分间的分离叫做
液-液萃取。其他的叫法有(或者称作)液体萃取或溶剂萃取。

液-液萃取设备的普遍的分类及其它们的主要特征和工业应用如表 3-1 所示:





非搅拌塔




混合澄清器






脉冲塔



回旋搅拌塔





往复板式萃取器






离心萃取器






在该操作中,如果液体混合物原料与溶剂不完全互溶,那么必须满足它们至少是部分互溶。 本质上,涉及到三步:

(1) 将原料混合物与溶质充分接触,

(2) 两相间的分离,以及

(3) 从每一相中除去溶剂和回收溶剂。



对不稳定的物料接触时间短
所需的空间小
能处理易乳化的物料
能处理液体密度差别较小的系统


产量高
等板高度低
应用广以及灵活性大
构造简单
能处理含悬浮固体的液体
能处理有乳化趋势的混合物



制药
核工业
石油化工

容量(生产量)适当
等板高度适度
可实现多极操作
建设费用不高
操作和维护费用低

制药
石油化工
冶金
化学

等板高度低
内无移动部分
可实现多极操作

石油化工
冶金
制药
肥料

高塔板效率
可处理溶剂比例宽
容量(生产量)大
灵活性好
放大可靠
可处理高粘度液体



核工业
冶金
表 3-1 液-液萃取器的特点及其工业应用
萃取器的类型

投资费用低
操作和维护费低
构造简单
可处理腐竹性物质品



石油化工
化学
肥料
冶金
一般的特点

石油化工
化学
应用领域


该技术的一些重要应用包括:从含煤油的燃料油中分离芳香族化合物以提高燃烧质量;从 烯烃和环烷烃中分离芳香族
化合物以改善润滑油的温度-粘度特征。例如:萃取分离可用在石 油化工业中,从催化生成的重整产品得到相对较纯的化
合物,如:苯、甲苯和二苯;可用于无 水醋酸的生产;可用于从煤焦碳液体萃取苯酚;可用于青毒素的纯化。萃取的重要
特征是溶质 的选择性本质,因为萃取中组分的分离是基于溶解度的差异,而不是基于蒸馏中的挥发性的差 异。

在单级间歇操作中,溶剂和溶液经混合,然后分成余两相:萃取相

extract< br>)
(在加入的 溶剂中含有所需的溶质)和萃
余相

raffinat e

(与溶剂的溶解度差的溶液)。借此,简单的混 合和分离发生于同一容器中。这种平衡可以方便地三角形上
(等边或是直角三角形)表示。各 组分间的平衡可以用活度系数的关系式(如准化学活度系数或非随机两液体模型)表示。
在理 论上,这些关系式只包括那些从二元混合物测量所得到的参数,但实际上,这样所得的准确性 较差,因此,一些多组
分平衡测量也用于获得参数。获得这些等式的参数很复杂,需要使用电 脑。

我们应该要知道,成功的萃取过程不应该只用萃取单元的性能加以评价,而是应该用整个 工厂所实现的回收效果的评
估加以评价。当估计的投资费用以及冶金处理所用的有机溶剂费用 较高时,必须要同时考虑工厂中用于分离的混合和分离
两部分。

用于萃取和浸取的设备,必须要能使两相充分接触以使两相间的溶质充分传递,同时能够 使两相完全分离。用连续的对流级
可以实现以最小量的溶剂达到最高的分离程度。在这种操作 中,进料进入第一级,而最终的萃取相在第一级离开,新鲜溶剂
进入最后一级,而最终萃取相 在最后一级离开。

2.浸取

浸取是利用一种溶剂从另一种固体中提取可溶性的成分。该操作或是用于产生有用物质的 浓溶液,或是为了从已被污
染了的可溶性的物质中除去一种不溶性的固体,如颜料。提取中所 用的方法 ,是由所含的可溶性组分的比例及其在固体中的
分布、固体的本质和微粒的尺度所决定。如果溶质在固体 中均匀分布,那么近表面的物质先溶解,形成了固体残渣的多孔性结
构。 在溶剂到达离表面更远的溶质之前,它必须要渗透过外层表面,因此该过程逐渐变得困难,提 取速度会下降。如果溶质
在固体中所占的分量很高,那么多孔性结构会立即破坏,以形成不溶 性残渣的细小沉淀物,溶剂到达溶质不会受到阻碍。一
般地,该过程可分三步进行讨论:第一 步,当溶质溶解在溶剂中时溶质相的变化;第二步,溶质通过固体孔中的溶剂扩散到
(固体) 颗粒的外边;第三步,溶质从与颗粒接触的溶剂中转移到溶液的体相

bulk phase

中。尽管 第一步过程发生如此
快以致可忽略其对速率的影响,但是这三步均会影响限制提取速率。

有时,可溶性物质分布在一种物质中独立的小洞穴中,溶剂不渗透到洞穴中,如金分散于 岩石中。此时,要粉碎该物
质,使可溶性的物质能够接触到溶剂。如果该固体为多孔性结构, 那么提取速率相对较慢,因为细胞壁会产生附加阻力。从
甜菜中提取糖时,细胞壁在阻碍那些 我们不要的、分子量较大的的组分的提取起着重要作用,因此,应该把甜菜制成长条带
状,以 使相对少的细胞受到损坏。在从种子中提取油时,溶质本身为液体,因此可以向溶剂扩散。

3.吸附

尽管吸附用于一种物化过程已有相当长的时间,但是发展成为现在的一种重要的分离过程 只是近三十年的事。在吸附
过程中,分子在两相重新分布,在这两相中,一相为固体而另一相 为一种流体(流体或气体)。



不象吸收,溶质分子从气体的体相中扩散至液相的主体,而在吸附中,分子从流体的体相 扩散至固体吸附剂的表面,
形成一种不同的吸附相。

一般地,气体吸附剂可以用于除去气体混合物中的痕量组分。常见的例子有:干燥气体以 防腐蚀、凝结,或防止一些
不需要的副反应。因为项目多样性,如电子设备、陶瓷素烧胚和小 袋吸附剂会包在包装袋中以保持其相对湿度较低。在使
用挥发性的溶剂过程中,有必要防止随 通风空气 带走溶剂而造成的偶然

incidental

损失。经过过吸附剂填料床 的空气会
影响吸附剂 的回收。

从液相中除去痕量的组分吸附同样有效,可以回收这种痕量的组分或是简单除去有毒物质 的工业废水。

吸附的任何一种潜在的应用,必须要考虑到其它的分离操作,尤其是蒸馏、吸收和液体的 萃取。每一种分离操作(过
程)都是利用了欲分离组分的性质的某种差异。蒸馏中这种差异是 挥发度;在吸收中为溶解度;在萃取中为分配系数。吸
附分离则取决于一种组分较另一种组分 更容易被吸附。合适操作的选择也取决于回收分离过的组分的难易程度。

利用蒸馏分离正烷烃和异烷烃,因组分间相对挥发度较低,所以需要级数很多。然而,使 用一种选择性的吸附剂可能是经
济的,该吸附剂是基于平均分子直径的微小的差异的来分离组 分的。正戊烷和异戊烷的平均分子直径分别为 0.489 nm 和
0.558nm。当孔径为 0.5nm 的吸附 剂与该气体混合物接触

be exposed to

时,较小的分子扩散至吸附剂的表面而滞留(在
其表面),而较大的分子排除在外。在该过程的另一步 骤中,减小总压或升温可使滞留的分子得以 吸附。

所有的吸附过程都有一(大)特点:对要处理的被吸附物质而言,吸附剂的(吸附)能力 是有限的。经常,吸附剂必
须能从该过程中加以回收和再生,即(吸附剂)恢复到原来的条件。 由于该原因,在早期的工业应用过程中,吸附装置与蒸
馏塔相比较,更难与连续操作结合的一 起。而且,很难批量生产具有同一吸附性质的吸附剂。商业吸附器的设计及其操作必
须要有足 够的弹性以解决这些变量。

这些因素和在吸附的早期应用中相当慢的热产

thermal regeneration
),
导致了吸附器不能 成为工厂设计师中的普遍选
择。既然可以利用范围更大的吸附剂,对一具体的应用都有特制的 吸附剂,这一局面已经得到改变,尤其是随着更快的热
量再生的其它方法成为可能。

当流体相中扩散的分子受来自邻近表面的力作用而滞留一段时间,吸附就发生了。该表面 表示在固体结构中显著的不
连续性,固体表面的原子有(多余)残余的分子力,这种分子力不 象在结构体相的分子力一样能被其周围的原子消除掉。
这些残余的作用力或范德华力对于所有 表面都是常见的,一些固体可以用作吸附剂的唯一原因是:它们能够以多孔形式进
行生产,形 成大的内表面。相比之下,即使当固体加以细分,外表面对整个吸附做出的贡献不大。商业吸

附剂总表面的平均值为 400.000m
2
kg。


Unit 16 Evaporation, Crystallization and Drying

第十六单元 蒸发、结晶和干燥




1.蒸发

蒸发器是利用加热来浓缩溶液,或是利用热把溶解的固体从饱和溶液沉淀析出以对之回 收。蒸发器
是有着特殊规定的再沸器,以用于分离气液两相,或当固体物质沉淀或结晶析出时, 用于除去该固体物质。
在一些应用中,尤其当提供足够的干舷时,简单的釜式再沸器就足够了。 管式的蒸发器或是水平的或是垂
直的,或长或短;液体可位于管内或管外,循环可以是自然循 环或是以泵或推进器驱动的强制性循环。

自然循环型的蒸发器是最常见的。强制循环型循环器非常适合于处理粘性或腐蚀性的物 料,但是购
置和维修的费用高。在长管式垂直设计中,由于蒸发,液体处于在环流或膜流中, 相应地,该蒸发器称之
为升膜式蒸发器。在降膜式蒸发器,液体分布于蒸发器的顶部,然后以 流体的形式向下流。静压头可忽略,
压降只不过

little more than

是汽流的摩擦力,传热效 果较好。由于接触时间短以及两相分离完全,降
膜式蒸发适合于热敏性物料。

长管式蒸发器(或是自然循环或是强制循环)用得最广泛。管的直径范围从 19~63 mm, 长度 12~
30 ft。排管式蒸发器管长 3~5 ft,它的中央降压管的面积与该管的横截面积相等。 有时,排管式蒸发器
中的循环以推进器来驱动。在某些类型的蒸发器中,固体直到它们达到所 需的尺度时才开始循环。

在蒸发器的设计和操作时,热经济是一个主要考虑因素。因为离开的蒸汽的潜热没有被利 用而是
丢弃

discard

,所以单效蒸发器浪费能量。然而,利用多效蒸发 器可以回收和再次利 用大部分潜热。

已经开发了各种各式的蒸发器以用于特殊工业中的特殊应用。蒸发器的设计可分成如下基 本类型:

直接加热蒸发器 该类型的蒸发器包括盐池和浸泡燃烧装置。浸泡燃烧蒸发器可应用 于那些由燃烧
产物引起的溶液污染可接受的场所。

长管蒸发器 在该类型蒸发器中,液体以薄膜的形式在长的垂直的热的蒸发管中流动, 既可用降膜
式蒸发器又可用升膜式蒸发器,处理能力大,适合于低粘度的溶液。强制循环蒸发器 在强制循环蒸发器
中,液体由泵输送到蒸发管中,适用于那些会污 染传热表面的物料,以及适用于蒸发器发生结晶的场所。

搅拌式薄膜蒸发器 在这种蒸发器 的设计中,利用机械方法(手段)将一薄层溶液撒到加热表面上。刮薄
式蒸发器用于高粘度的物料和固体 产物。

短管式蒸发器

蒸发器的选择
也称排管式蒸发器,用于制糖工业中。



对于某一特殊应用,最适合的蒸发器类型的选择取决于下列因素:(1)所需的处理量

(2)进料的粘度以及蒸发过程中粘度的增加

(3)所需的产物的本质:固体、淤泥或浓溶液

(4)产物的热敏性

(5)物料是否会产生污染

(6)溶液是否会起泡

(7)是否可用直接加热

辅助设备 对于真空条件下操作的蒸发器,需要冷凝器和真空泵;对于水溶液,则需利 用蒸汽喷
射器和喷射式冷凝器。喷射式冷凝器是直接冷凝器,在该冷凝器中,蒸汽是利用冷却 水喷射直接而冷却。



2.结晶

结晶用于固体的产生、纯化及其回收。结晶的产物有着好看的外表,流动性能好,易处理, 易包装。
该操作的应用范围广:从特种化学品(如药物)的小规模生产,到产品以吨数生产(如 糖、常见盐类和
肥料)生产(都可以使用该操作)。

结晶的设备可用于所得到液体过程和现象的方法加以分类,也可用用于悬浮增长晶体的方 法加以分类。可以通过冷却或蒸发得到过饱和现象

supersaturation
)< br>。有四类基本的结晶器: 槽式结晶器、
刮膜式结晶器、晶浆循环结晶器、以及母液循环式结晶器。














3.干燥


液体循环结晶器


岩浆循环结晶器

生产均匀的晶体(其尺寸小于
岩浆)、生产量大

大颗粒晶体的生产、生产量大

石膏、无机盐、硝酸钠和硝酸钾、硝酸银


刮膜式结晶器

槽式结晶器

有机化合物、用于有污染问题
的场所,粘性的物料

铵和其它无机盐、氯化钠和氯化钾

表 3-2 总结了这些主要类型的结晶器的典型应用 (译成为主动句较好)
结晶器的类型

间歇操作、规模生产小

氯苯、有机酸、烷烃、石蜡油、环烷烃、
尿素

应 用

脂肪酸、植物油、糖

典型的用途


干燥是用蒸发方法除去水和其它的挥发性液体。大部分在其生产时需要干燥。选择干燥设 备的最
主要的考虑因素是进料的本质及其浓度。干燥是能源密集型的过程,利用热干燥来除去 液体的费用较利
用机械技术的费用要高得多。

除了几种特殊的应用之外,热的空气在工业干燥器中用作加热和传质介质。空气可直接用 所用燃
料(石油、天然气和煤)的燃烧产物加热,或者间接加热,通常通过蒸汽加热的翅片管 管道加热。

用于化学过程工业中的干燥器基本类型有:

板式干燥器 间歇板式干燥器用于干燥少量的固体,所适用的物料范围广。欲干燥的 物料位于固体
底板上,在固体底板上吹入热空气,欲干燥的物料位于穿了孔的底板上,热空气 流经该底板。间歇干燥
器劳动力要求高,但在干燥条件和产物存货可以得到很好的控制。板式 干燥器适合于干燥有价值的产物
(品)。

带式干燥器(连续循环带式干燥器) 该类型的干燥器,固体产物在一个很长的穿孔 的传送带上,
热空气强制地流过该传送带。传送带被罩在一长的矩形箱内,该箱分成几个区域, 以致能控制干燥气体的
流型和温度。固体干燥器和干燥空气的相对运动可以是并流的,或者更 多的是对流。

该类型的干燥器只适合于那些形成带式结晶的床层的物料,可实现较高的干燥速率,质量 控制容
易,热效率高,以蒸汽加热,干燥每 1 kg 蒸发水需要用蒸汽低于 1.5 kg。该类型的干燥 器的缺点为,
由于机械传送带、维护费用高,所以首次(最初的)费用高。

旋转式干燥器 在旋转式干燥器中,固体物质沿着一旋转的倾斜的圆柱的内部进行输 送,通过直接
与流经圆柱的热空气而加热、干燥。有时,圆柱间接加热。

旋转干燥器适合于干燥自由流动的粒状的物质,适合用于产量高的连续操作;热效率高, 投资费用
和劳力费用相对较低。该类型干燥器的一些缺点为:停留时间不统一,产生灰尘,噪 声程度较大。

流化床干燥器 在该类型的干燥器中,干燥气以足够的速率通过固体床层,以使床层 保持在流化状
态,该流化状态可提高很大传热和干燥速率。流化床干燥器适合于粒状大小范围 为 1~3mm的粒状和
晶体状物质。该干燥器可设计为连续操作和间歇操作。流化床干燥器的 主要优点:热传递快且均匀、干
燥时间短、干燥条件能很好控制、占地面积的要求低。与其它 类型的干燥器相比,需要的动力高。

气流干燥器 也称 flash 干燥器 它们的操作原理与喷雾式干燥器相似。欲干燥的产品由 一个合适的进料
器分散于向上流动的加热气的蒸汽中。该设备起着气流传送设备和干燥器的作 用。接触 时间短,(该因素)
限制了要干燥的物料颗粒的大小。气流干燥器适合于那些颗粒太小而不能在流化床干 燥器中干燥的物料。
该类型的干燥剂的热效率一般较低。
喷雾式干燥器 喷雾式干燥器一般适合用于液体和稀的淤泥进料,但是可通过设计以 处理任何能用
泵输送的物料。放置于垂直的圆柱形容器的要干燥的物料,在一喷嘴中或在一圆 盘状的原 子化器中原子化。


热的空气在容器中向上流(在有些设计中向下流)、输送以及干燥 液滴。液体从液滴的表面上快速汽化,
同时形成有空隙的多孔的颗粒。干燥过的颗粒在旋风 (cyclone)分离器中或在袋状过滤器中加以除去。

喷雾式干燥器的主要优点是:接触时间短,这使它适合于干燥热敏性物质;能很好地控制 产物颗粒
尺度、体相密度。因为进料中固体浓度低,所以加热的要求高。
旋转鼓式干燥器 鼓式干燥器适合用于液体和稀淤泥进料。当欲干燥的物料会的加热 表面形成一薄
膜,不是热敏性物料时,鼓式干燥器可以替代喷雾式干燥器(另一种选择)。
Unit 17 Chemical Reaction Engineering

第十七单元 化学反应工程




每一种工业化的化工过程的目的都是通过一系列的处理步骤从各种原料经济性地生成所 需的产
品。图 3-5 表示一种典型的过程。为了使原料处于能发生化学反应的形式,原料要经 过< br>(
undergo)
许多物理处理步骤,然后,通过反应器。为了得到最终的所需的产品 ,反应的 产物必须经过进一步的物
理处理,如分离、纯化等。

用于物理处理步骤的设备的设计在单元操作中研究,这里我们关心的是过程的化学处理步 骤。经
济上,化学处理步骤是不重要的装置,如一简单的混合槽。然而,化学处理步骤通常是 整个过程的核心,
在经济方面可使过程发生或停止的因素。

反应器的设计不是例行 公事

routine

,对于某一过程可以提出许多其它的设计。为了寻 求最佳的
设计,必须减少的费用不仅仅是反应器费用。一种设计可以是反应器费用低,但离开 该装置的物料可以
是该情况:物料的处理费用比其它设计费用高得多。所以全过程的经济性必 须要考虑。

反应器的设计要运用各种领域(热力学、化学动力学、流体力学、传质、传热以及经济学) 的信息、< br>知识和经验。化学反应工程是这些所有的因素的综合

synthesis
)< br>,其目的是精确地 设计化学反应器。

化学反应器的设计可能是化学工程师的独特(unique)的一种活动,这可能较其它方面更 能证明化
学工程作为工程学科的独特的分支的存在。

在化学反应器设计时,必须要回答两个问题:

(1) 我们期望发生什么变化?

(2) 变化发生有多快?。

第一个问题关于热力学,而第二个问题是关于各种速率过程— — 化学动力学、传热,等等。 把这
些过程综合起来以及要确定这些过程是如何关联的,是相当难的问题(事情)。因此我们 必须从简 单的情


况开始,利用考虑其它的因素来增长(帮助)我们的分析,直到我们能处理更 困难的问题。

1、热力学

热力学给出了设计所需的两条重要的信息:反应释放(或吸收)的热量以及反应的最大的可能程度。
化学反应总是伴随着热量的释放或吸收,对于一合适的设计,热量的大小必须要知道,如 反应:

正,吸热反应

aA rR+sS

负,放热反应

在反应前后,对体系在同一温度、压力下进行测量,当 a 摩尔的 A 消失生成 r 摩尔的 R 和 s
摩尔的 S 时,在 T 温度下的反应热为环境传给该反应体系的热量。若知道反应热或是通 热化学数据
对反应热进行估计,那么可以计算反应过程的热效应。

热力学中,也可以从反应物料的标准自由能来计算平衡常数 K。如果知道了平衡常数,那 么可以
估计反应物的最大的可得的收率。



2、化学动力学

在合适的条件下,进料可以转变为新的不同的物质,这些物质可构成不同的化学种类。如 果该过
程只是通过组成的原子的重排和重新分配的发生来形成新的分子,那么我们说发生了化 学反应。化学是
与这些反应的研究有关,研究反应的形式和机理,研究所涉及到的物理和能量 变化以及产品的生成速率。

最后提起的感兴趣的领域是化学动力学,化学动力学是我们首先所关注的。化学动力学研 究的是
影响反应速率的因素,测定反应速率以及对得到的数值的提出解释。对于化学工程师来 说,如果他要满
意地设计影响工业规模的反应的设备,那么他必须知道一个反应的动力学。当 然,如果该反应如此快以
致该体系基本上处于平衡,那么可大大简化设备的设计。不需要动力 学信息,热力学信息就足够了。

3、均相反应和多相反应

均相反应是这样的反应:在该反应中,反应物、产物和所用的催化剂形成一个连续相:气 相或液相。< br>均相的气相反应器总是连续操作,而均匀的液相反应器可以间歇操作或连续操作。管式反应器通常用于均< br>相的气相反应,例如,在石油组分热裂解以生成乙烯过程中,以及二氯 甲烷热分解生成氯乙烯中。管式和
搅拌釜式反应器均可用于均相的液相反应。

在多相反应中,存在两相或多相,反应器的设计的主要问题是提高相间的质量传递。可能 的相的组
△Hr


合有:
(1)液-液两相 不互溶的液相;反应有用混合酸对甲苯或苯的硝化反应、乳状液的 聚合反应。
(2)液-固两相 一种或多种液相对一种固体相接触,该固体或是反应物或是催化剂。

(3)液-固-气三相 此时,固体通常为催化剂,如在氨的氢解反应中,用固在活性 炭上的浆状
铂(Pt)作为催化剂。

(4) 气-固两相 在这种情况下,固体可以参与反应或用作催化剂,例如:吹气炉中铁 矿的还原反
应以及固体燃料的燃烧,在这些例子中固体为反应物。

(5)气-液相 在这种情况下,液体参与反应或用作催化剂。

4、反应器的几何构型(类型)

用于那些已经成熟的过程的反应器的设计通常较为复杂,这些设计经过长时间的开发(或 发展)
以满足该过程的要求,而且该反应器的设计独特。然而,可方便地将反应器的设计分成 以下几类。

搅拌釜式反应器 搅拌釜式反应器由带有机械搅拌器和冷却外套或线圈的釜组成,可 以是间歇反应
器或连续反应器。几个反应器可以串联使用。

可以认为搅拌釜式反应器是基本的化学反应器,其模型建立常见的大规模实验室烧瓶的基 础之上。
反应釜的尺寸从几升到几千升不等。它们用于均相和多相的液-液和液-气反应;以 及用于那些涉及到
有细小的悬浮固体的反应,悬浮固体由搅拌得以保持。因为搅拌的程度由设 计师(者)的控制,所以搅
拌釜式反应特别适合于那些需要良好的传质或传热的反应。
当反应器以连续操作时,反应器中的组成不变,与产品流中的组成相同。因此,除了快速反应外,
这 将限制一步反应所能得到的转化率。

搅拌的动力要求取决于所需的搅拌程度,其范围为:从适中混合的 0.2 KWms 到剧烈混合时的 2
KW ms。

管式反应器

如果需要传热速率高,那么可用直径小的管子以增加表面积与体积的比率。几根管子可并 联排列,
以相似排列连接于多种或固定每于一外壳和管式加热器上以形成管板。对于高温反应, 这些管子可排列在
一炉子之中。

填料床反应器 有两种类型的填料床反应器:一类以固体是反应物,另一类以固体是 催化剂。在萃
取湿法冶金工业中,可找到第一类反应器许多例子。

管式反应器通常用于气相反应,但也适用于一些液相反应。


化学过程工业的设计者,通常关注的是第二类反应器:催化反应器。工业上的填料床催化 反应器
尺寸范围:小到直径为厘米长小试管,大到直径很大的填料床。填料床反应器用于气体 和气-液两相反
应。在直径很大的填料床上传热速率慢,需要很大的传热速率的场所,应该考 虑流化床反应器。
流化床反应器 流化床的基本特征为,固体物质通过反应流体的向上流动而维护悬浮 状态,这有助
于提高传质和传热速率、混合均匀。该固体物质可以是催化剂;流化燃烧过程中 的一种反应物或是为了
提高传热而加入的惰性粉末。与固定床相比,尽管流化床的主要优点 (势)在于传热速率较高,但是在
那些必须要输送大量的固体时,流化床作为反应过程一部分 很有用,如用于催化剂从一个容器转移到另
一个容器而再生的场所。

流化床只用于尺度相对较小(30um)的颗粒和气体。

近年来,在流化床反应器方面作了大量的研究和开发工作,但是直径很大的反应器的设计 和放大
仍然是不稳定的过程,设计的方法主要是经验(方法)。

间歇或连续操作(处理)

在间歇操作中,所有的试剂在开始时同时加入;反应进行时,组成随着时间的改变,当达 到所需
的转化率时,停止反应,取出产物。间歇过程适合于小量(规模)的生产,以及适合于 在同一设备生产
不同的产品或不同种级别产品的过程,如,生产颜料、染料和聚合物。

在连续的过程中,反应物连续不断地加入到反应器中以及产物连续不断地取出。反应器在 稳态条件
下进行操作,通常连续生产较间歇生产的生产费用要低,但是缺少间歇生产的弹性。 大规模的生产
常常选择连续反应器。那些不适合间歇操作和连续操作的定义的操作常叫做半连 续或半间歇操作。
在半间歇反应器中,随着反应的进行,可以加入某些反应物或取出某些反应 产物。半连续的过程是
那些为了某一目的而定期中断的过程,如为了催化剂的再生。
Unit 20 Material Science and Chemical Engineering
材料科学和化学工程
A few years ago, who would have dreamed that an aircraft could circumnavigate the earth without landing or
refueling? Yet in 1986 the novel aircraft Voyager did just that. The secret of Voyager’s long flight lies in advanced
materials that did not exist a few years ago. Much of the airframe was constructed from strong, lightweight
polymer-fiber composite sections assembled with durable, high-strength adhesive; the engine was lubricated with a
synthetic multicomponent liquid designed to maintain lubricity for a long time under continuous operation. These
special materials typify the advances being made by scientists and engineers to meet the demands of modern
society.
几年以前,谁 会想到一架飞机可以绕地球航行而中途不需要着陆或添加燃料?而在1986年新型的飞
机航海者就做到 了这一点。航海者具备长途飞行能力的秘密就在于几年前还没有出现的先进的材料。其机
身大部分是由强 度大、质量轻的聚合纤维用耐久的、高强度的粘合剂组装而成的。而发动机润滑油是合成
的多组分液体, 可维持很长时间连续运转的润滑性。这些特殊材料具有科学家和工程师们为满足现代社会
的需求所发明的 先进技术。

The future of industries such as transportation, communications, electronics, and energy conversion hinges


on new and improved materials and the processing technologies required to produce them. Recent years have seen
rapid advances in our understanding of how to combine substances into materials with special, high-performance
properties and how to best use these materials in sophisticated designs.
如运输、通讯、电子、能量转换这些工业的未来多依赖新的、先进的材料以及生产中所需要的加工技
术。 近年来,在我们了解了如何把一些特殊的具有高性能的物质融入原材料并且怎样最好地在复杂设计中
使用 这些材料后,这方面已有了很大的发展。

The revolution in materials science and engineering presents both opportunities and challenges to chemical
engineers. With their basic background in chemistry, physics, and mathematics and their understanding of transport
phenomena, thermodynamics, reaction engineering, and process design, chemical engineers can bring innovative
solutions to the problems of modern materials technologies. But it is imperative that they depart from the
traditional “think big” philosophy of the profession; to participate effectively in modern materials science and
engineering they must learn to “think small” the crucial phenomena in making modern advanced materials occur at
the molecular and microscale levels, and chemical engineers must understand and learn to control such phenomena
if they are to engineer the new products and processes for making them. This crucial challenge is illustrated in the
selected materials areas described in the following sections.
材料科学和工程的革 命为化学工程师带来了机会,也带来了挑战。化学工程师凭借他们在化学、物理
和数学方面的知识基础以 及他们对传输现象、动力学、反应工程和过程设计的了解,能够创造性地解决现
代材料技术中的问题。但 是他们一定要摈弃掉传统职业理念中“考虑大的”这个习惯,要有效地投入现代
材料科学和工程中必须要 学会“从小处思考”。在制造现代先进材料时的关键现象是发生在分子级和微观的
水平。如果化学工程师 要为这些新材料设计新产品和工艺就必须了解并且学会控制这些现象。在下面选择
介绍的几种材料领域里 我们将叙述这种困难的挑战。

1. Polymers
The modern era of polymer science belongs to the chemical engineer. Over the years, polymer chemists have
invented a wealth of novel macromolecules and polymers. Yet understanding how these molecules can be
synthesized and processed to exhibit their maximum theoretical properties is still a frontier for research. Only
recently has modern instrumentation been developed to help us understand the fundamental interactions of
macromolecules with themselves, with particulate solids, with organic and inorganic fibers, and with other surfaces.
Chemical engineers are using these tools to probe the microscale dynamics of macromolecules. Using the insight
gained from these techniques, they are manipulating macromolecular interactions both to develop improved
processes and to create new materials.
1.聚合物
现代聚合物科学的时代属于化学工程师。这些年来,聚 合物化学家创造了大量的高分子和聚合物。然而
了解这些高分子是怎样被合成并加工以最大限度地具备理 论性质仍然是研究的前沿领域。一直到最近才开
发了现代仪器帮助我们了解高分子之间、高分子与固体粒 子、有机和无机纤维与其它界面之间的相互作用。
化学工程师正使用这些工具探索高分子的微型动力学现 象,他们利用从这些技术中获得的知识,正在处理
高分子间的反应以开发先进的工艺并制造新的材料。

The power of chemical processing for controlling materials structure on the microscale is illustrated by the
current generation of high-strength polymer fibers, some of which have strength-to weigh ratios an order of
magnitude greater than steel. This spontaneous orientation is the result of both the processing conditions chosen
and the highly rigid linear molecular structure of the aramid polymer. During spinning, the oriented regions in the
liquid phases align with the fiber axis to give the resulting fiber high strength and rigidity. The concept of spinning


fibers from anisotropic phases has been extended to both solutions and melts of newer polymers, such as
polybenzothiazole, as well as traditional polymers such as polyethylene. Ultrahigh-strength fibers of polyethylene
have been prepared by gel spinning. The same concept, controlling the molecular orientation of polymers to
produce high strength, is also being achieved through other processes, such as fiber- stretching carried out under
precise conditions.
通过化学加工控制材料微型结构的能力可用现代高强度聚合纤维进行描述。一些聚合纤维的强度-质量比
比钢铁高一个数量级。它的自由取向是由所选择的加工条件以及芳香族聚酰胺的高度刚性的线性分子结构
所决定的。在纺丝时,液相中的定向部分是围绕纤维轴方向排列而使得纤维具有高强度和高硬度,各向异
性的纺丝纤维的概念则在新聚合物如聚苯并噻唑、聚乙烯的溶解和熔融方面都有了延伸。超高强度的聚乙
烯纤维是通过冻胶纺丝的方法制备的。同样的,控制聚合物的分子取向以生产高强度产品也可以通过其它
的工艺途径,如在极其精确的条件下进行纤维拉伸而完成。

In addition to processes that result in materials with specific high-performance properties, chemical engineers
continue to design new processes for the low-cost manufacture of polymers.
除了这些可以得到具有特别高性能的材料的加工过程,化学工程师们还设计一些新 的工艺过程以生产低
成本的聚合物。
2. Polymer Composites
Polymer composites consist of high-modulus fibers embedded in and bonded to a continuous polymer matrix.
These gibers may be shut, long, or continuous. They may be randomly oriented so that they impart greater strength
or stiffness in all directions to the composite (isotropic composites), or they may be oriented in a specific direction
so that the high- performance characteristics of the composite are exhibited preferentially along one axis of the
material (anisotropic composites). These latter fiber composites are based on the principle of one-dimensional
microstructural reinforcement by disconnected, tension-bearing “cables” or “rods”.
2.聚合复合材料
复合材料包括在一个聚合物母 体上嵌入或粘合上高强度或高模数纤维。这些纤维可能是短的、长的或连
续的。它们可能是随意取向的而 使复合材料在所有方向上都具有较大的强度或硬度,也可能沿某个特殊方
向取向而使复合材料的高性能优 先沿着某个轴线表现出来。后者是根据一向微结构加固的原理,通过不连
贯的、拉伸支撑电缆线或电缆条 达到目的。

To achieve a material with improved properties (e.g., strength, stiffness, or toughness) in more than one
dimension, composite laminates can be formed by bonding individual sheets of anisotropic composite in
alternating orientations. Alternatively, two- dimensional reinforcement can be achieved in a single sheet by using
fabrics of high- performance fibers that have been woven with enough bonding in the crossovers that the
reinforcing structure acts as a connected net or trusswork. One can imagine that an interdisciplinary collaboration
between chemical engineers and textile engineers might lead to ways of selecting the warp, woof, and weave in
fabrics of high-strength fibers to end up with trussworks for composites with highly tailored dimensional
distributions of properties.
要得到在多个方向上具有优良性能的材料,可以通过改变角度粘结各向异性的 复合片得到合成板。另一
方面,两向强化的材料可以通过把高性能的纤维编织成一个平面,面上有足够的 粘结力而使加固结构表现
得就像联结起来的网或桁架。你可以想象,化学工程师和纺织工程师之间的学术 合作将有利于选择经线、
纬线和高强度纤维的编织方法,以得到高选择性能分布的桁架型的复合材料。

First-generation polymer composites (e.g., fiberglass) used thermosetting epoxy polymers reinforced with
randomly oriented short glass fibers. The filled epoxy resin could be cured into a permanent shape in a mold to


give lightweight, moderately strong shapes.
第一代聚合合成材料(如玻璃纤维)使用热固性环氧树脂聚合物。它是用任意取向的短 玻璃纤维进行强
化的。环氧树脂填充在一个模型中被塑化成永久的形状而得到轻质的、强度适当的模制塑 胶。

The current generation of composites is being made by hand laying woven glass fabric onto a mold or perform,
impregnating it with resin, and curing to shape. Use of these composites was pioneered for certain types of military
aircraft because the lighter airframes provided greater cruising range. Today, major components for aircraft and
spacecraft are manufactured in this manner as are an increasing number of automobile components. The current
generation of composites are being used in automotive and truck parts such as body panels, hoods, trunk lids, ducts,
drive shafts, and fuel tanks. In such applications, they exhibit a better strength-to-weight ratio than metals, as well
as improved corrosion resistance. For example, a polymer composite automobile hood is slightly lighter than one
of aluminum and more than twice as light as one of steel. The level of energy required to manufacture this hood is
slightly lower than that required for steel and about 20 percent of that for aluminum; molding and tooling costs are
lower and permit more rapid model changeover to accommodate new designs.
现代复合材料是用手工把编织好的玻璃纤 维放到模具或预型件中,然后用树脂灌注,固化成型后制得的。
这些复合材料最先是使用在某些型号的军 用飞机上。因为比较轻的机身使飞行巡航范围增大。今天,飞机
和航空飞船的大部分部件都是这样制造的 ,而且汽车也正在加入到这个行列。现代复合材料正被应用于小
汽车和载重卡车的车身面板、车棚、后行 李箱盖、管道、驱动轴和燃料罐。在这些应用中,复合材料表现
出比金属更好的强度-质量比和更优良的 抗腐蚀性。例如,一种聚合复合材料制成的汽车车棚比用铝质的轻
一点,比钢铁的轻两倍,但这种方法所 需能量比钢铁的低一点,比铝的低20%。模塑和刀具加工的成本也
比较低,使模型的改变可以更快而适 应新设计的要求。

The mechanical strength exhibited by these composites is essentially that of the reinforcing glass fibers,
although this is often compromised by structural defects. Engineering studies are yielding important information
about how the properties of these structures are influenced by the nature of the glass-resin interface and by
structural voids and similar defects and how microdefects can propagate into structural failure. These composites
and the information gained from studying them have set the stage for the next generation of polymer composites,
based on high-strength fibers such as the aramids.
这些复合 材料表现出来的机械强度主要是由强化玻璃纤维决定的,尽管结构缺陷会使强度减弱。工程学
研究正提供 重要的信息说明材料结构是如何受到玻璃树脂的界面性质、构造空隙和类似缺陷的影响以及这
些微缺陷是 如何扩散产生构造裂缝的。这些复合材料以及从对它们的研究中获得的信息使人类进入到生产
第二代聚合 复合材料的阶段,即以高强度纤维如芳香族聚酰胺为基础的复合材料。

3. Advanced Ceramics
For most people, the word “ceramics” conjures up the notion of things like china, pottery, tiles, and bricks.
Advanced ceramics differ from these conventional ceramics by their composition, processing, and microstructure.
For example:
3.现代陶瓷
对大 多数人来说,“陶瓷”这个词会让人联想到瓷器、陶器、砖、瓦这些东西。现代陶瓷以它们的组
成、加工 过程和微细结构区别于这些传统的陶瓷。例如:

·Conventional ceramics are made from natural raw materials such as clay or silica; advanced ceramics require
extremely pure man-made starting materials such as silicon carbide, silicon nitride, zirconium oxide, or aluminum
oxide and may also incorporate sophisticated additives to produce specific microstructures.


·传统的陶 瓷是用天然的原料如粘土或硅石制成的。现代陶瓷则要求非常纯的人造原料如碳化硅、氮化
硅、氧化锆或 氧化铝,可能还要渗入一些复杂的添加剂来产生特殊的微结构。

·Conventional ceramics initially take shape on a potter’s wheel or by slip casting and are fired (sintered) in
kilns; advanced ceramics are formed and sintered in more complex processes such as hot isostatic pressing.
·传统陶瓷是先在陶工轮上或粉浆浇注成型 ,然后在窑里烧结定型。现代陶瓷是用更为复杂的工艺过程
如高温静压成型法来定型的。

·The microstructure of conventional ceramics contains flaws readily visible under optical microscopes; the
microstructure of advanced ceramics is far more uniform and typically is examined for defects under electron
microscopes capable of magnifications of 50,000 times or more.
·传统陶瓷的微结构容易形成在光学显微镜下就可以看 见的裂痕。而现代陶瓷的微结构则要均匀得多,
一般要在5万倍或更大倍数的电子显微镜下才能检查出瑕 疵来。

Advanced ceramics have a wide range of application. In many cases, they do not constitute a final product in
themselves, but are assembled into components critical to the successful performance of some other complex
system. Commercial applications of advanced ceramics can be seen in cutting tools, engine nozzles, components of
turbines and turbochargers, tiles for space vehicles, cylinders to store atomic and chemical waste, gas and oil
drilling valves, motor plates and shields, and electrodes for corrosive liquids.
现代陶瓷的应用范围更为广 泛。在很多情况下,现代陶瓷并未直接成为最终产品,而是组合在一些复杂
的系统中成为优良性能的关键 部分。现代陶瓷的商业应用可以在切削工具、发动机喷嘴、涡轮和涡轮增压
器的元件、太空舱的瓦面、储 藏原子和化学废物的圆柱体、气体和石油钻探阀、电动极板和防护罩以及腐
蚀性液体中的电极等等方面看 见。

4. Ceramic Composites
Like polymer composites, ceramic composites consist of high- strength of high-modulus fibers embedded in a
continuous matrix. Fibers may be in the form of “whiskers” of substances such as silicon carbide or aluminum
oxide that are grown as single crystals and that therefore have fewer defects than the same substances in a bulk
ceramic. Fibers in a ceramic composite serve to block crack propagation; a growing crack may be deflected to a
fiber or might pull the fiber from the matrix. Both processes absorb energy, slowing the propagation of the crack.
The strength, stiffness, and toughness of a ceramic composite is principally a function of the reinforcing fibers, but
the matrix makes its own contribution to these properties. The ability of the composite material to conduct heat and
current is strongly influenced by the inductivity of the matrix. The interaction between the fiber and the matrix is
also important to the mechanical properties of the composite material and is mediated by the chemical
compatibility between fiber and matrix at the fiber surface. A prerequisite for adhesion between these two materials
is that the matrix, in its fluid form, be capable of wetting the fibers. Chemical bonding between the two
components can then take place.

4.陶瓷合成材料
像聚合复合材料 一样,陶瓷复合材料也包括在连续的基质上嵌入高强度或高模数的纤维。纤维可以是
碳化硅或氧化铝以“ 晶须”的形式出现,然后生长为单个晶体。这与同样的物质直接嵌入在大块陶瓷上相
比较所产生裂纹较少 。陶瓷复合体上的纤维可以阻碍裂纹的扩散。正在生长的裂纹会向纤维处偏移或使纤
维脱离基质。这两个 过程都要吸收能量,从而减慢了裂纹的扩散。陶瓷复合材料的强度、硬度和韧性主要
取决于强化纤维,但 是基质也会对这些性质产生影响。复合材料的导热和导电性能受基质传导系数的影响


很大 。纤维和基质之间的相互作用对复合材料机械性能的影响也很大,并可通过纤维表面纤维和基质间的
化学 兼容性进行调整,这两种物质粘合在一起的前提就是基质以流体形态存在时能润湿纤维。两种组分间
形成 了化学键。

As with advanced ceramics, chemical reactions play a crucial role in the fabrication of ceramic composites.
Both defect-free ceramic fibers and optimal chemical bonds between fiber and matrix are required for these
composites to exhibit the desired mechanical properties in use. Engineering these chemical reactions in reliable
manufacturing processes requires the expertise of chemical engineers.
与现代陶瓷的产生一样,化学反应在陶瓷复合材料的加工制造中也充当了关键的角色。这些复合材料
要求 无瑕疵的陶瓷纤维、纤维和母体间有最适当的作用力,这才能在使用中展现所预想的机械性能。在实
际的 制造过程中设计这样的化学反应要求化学工程师具备专业的知识。

5. Composite Liquids
A final important class of composite materials is the composite liquids. Composite liquids are highly
structured fluids based either on particles or droplets in suspension, surfactants, liquid crystalline phases, or other
macromolecules. A number of composite liquids are essential to the needs of modern industry and society because
they exhibit properties important to special end uses. Examples include lubricants, hydraulic traction fluids, cutting
fluids, and oil-drilling muds. Paints, coatings, and adhesives may also be composite liquids. Indeed, composite
liquids are valuable in any case where a well-designed liquid state is absolutely essential for proper delivery and
action.
5.复合液体
最后一类重要的复合材 料是复合液体。复合液体是高结构液体,以悬浮液、表面活性剂、液晶相或其
它大分子与固体微粒或液滴 组成。许多复合液体对现代工业和社会都是必不可少的,因为它们表现出来的
性质对一些特殊用途是非常 重要的。这些用途包括润滑剂、水力牵引液体以及油田钻井泥浆,油漆、涂料
和粘合剂也可能是合成液体 。确实,在任何情况下,如果好的液体状态对某种传递和反应是重要的,那么
合成液体就是有价值的。

Chemical engineers have long been involved with materials science and engineering. This involvement will
increase as new materials are developed whose properties depend strongly on their microstructure and processing
history. Chemical engineers will probe the nature of microstructure—how it is formed in materials and what
factors are involved in controlling it. They will provide a new fusion between the traditionally separate areas of
materials synthesis and materials processing. And they will bring new approaches to the problems of fabricating
and repairing complex materials systems.
化学工程师长期涉足材料科学和工程学研究工作。随着新材料的开发,其性质越来越 依赖微结构和加
工过程,研究程度也将深入。化学工程师将探索微结构的本质—它是如何在材料中形成的 , 哪些因素可以
用来控制它。他们将采用新的方式把传统的分离开来的材料合成和材料加工融合起来。 他们还将用新方法
解决构造的问题,修复复杂的材料系统。


Unit 21 Chemical Industry and Environment
化学工业与环境
How can we reduce the amount of waste that is produced? And how we close the loop by redirecting spent
materials and products into programs of recycling? All of these questions must be answered through careful
research in the coming years as we strive to keep civilization in balance with nature.


我们怎样才能减少产生废物的数量?我们怎样才能使废弃物质和商品 纳入循环使用的程序?所有这
些问题必须要在未来的几年里通过仔细的研究得到解决,这样我们才能保持 文明与自然的平衡。

1. Atmospheric Chemistry
Coal-burning power plants, as well as some natural processes, deliver sulfur compounds to the stratosphere,
where oxidation produces sulfuric acid particles that reflect away some of the incoming visible solar radiation. In
the troposphere, nitrogen oxides produced by the combustion of fossil fuels combine with many organic molecules
under the influence of sunlight to produce urban smog. The volatile hydrocarbon isoprene, well known as a
building block of synthetic rubber, is also produced naturally in forests. And the chlorofluorocarbons, better known
as CFCs, are inert in automobile air conditioners and home refrigerators but come apart under ultraviolet
bombardment in the mid-stratosphere with devastating effect on the earth’s stratospheric ozone layer. The globally
averaged atmospheric concentration of stratospheric ozone itself is only 3 parts in 10 million, but it has played a
crucial protective role in the development of all biological life through its absorption of potentially harmful
shout-wavelength solar ultraviolet radiation.
1.大气化学
燃煤发电厂像一些自 然过程一样,也会释放硫化合物到大气层中,在那里氧化作用产生硫酸颗粒能反
射入射进来的可见太阳辐 射。在对流层,化石燃料燃烧所产生的氮氧化物在阳光的影响下与许多有机物分
子结合产生都市烟雾。挥 发的碳氢化合物异戊二烯,也就是众所周知的合成橡胶的结构单元,可以在森林
中天然产生含氯氟烃。我 们所熟悉的CFCs,在汽车空调和家用冰箱里是惰性的,但在中平流层内在紫外线
的照射下回发生分解 从而对地球大气臭氧层造成破坏,全球大气层中臭氧的平均浓度只有3ppm,但它对所
有生命体的生长 发育都起了关键的保护作用,因为是它吸收了太阳光线中有害的短波紫外辐射。

During the past 20 years, public attention has been focused on ways that mankind has caused changes in the
atmosphere: acid rain, stratospheric zone depletion, greenhouse warming, and the increased oxidizing capacity of
the atmosphere. We have known for generations that human activity has affected the nearby surroundings, but only
gradually have we noticed such effects as acid rain on a regional then on an intercontinental scale. With the
problem of ozone depletion and concerns about global warming, we have now truly entered an era of global
change, but the underlying scientific facts have not yet been fully established.
在过去的二十年中,公众的注意力集中在人类对大气层的改变:酸雨、平流 层臭氧空洞、温室现象,
以及大气的氧化能力增强,前几代人已经知道,人类的活动会对邻近的环境造成 影响,但意识到像酸雨这
样的效应将由局部扩展到洲际范围则是慢慢发现的。随着臭氧空洞问题的出现, 考虑到对全球的威胁,我
们已真正进入到全球话改变的时代,但是基本的科学论据还没有完全建立。

2. Life Cycle Analysis
Every stage of a product’s life cycle has an environmental impact, starting with extraction of raw materials,
continuing through processing, manufacturing, and transportation, and concluding with consumption and disposal
or recovery. Technology and chemical science are challenged at every stage. Redesigning products and processes
to minimize environmental impact requires a new philosophy of production and a different level of understanding
of chemical transformations. Environmentally friendly products require novel materials that are reusable,
recyclable, or biodegradable; properties of the materials are determined by the chemical composition and structure.
To minimize waste and polluting by- products, new kinds of chemical process schemes will have to be developed.
Improved chemical separation techniques are needed to enhance efficiency and to remove residual pollutants,
which in turn will require new chemical treatment methods in order to render them harmless. Pollutants such as
radioactive elements and toxic heavy metals that cannot be readily converted into harmless materials will need to


be immobilized in inert materials so that they can be safely stored. Finally, the leftover pollution of an earlier, less
environmentally aware era demands improved chemical and biological remediation techniques.
2.生命周期分析
产品生命循环周期的每一个阶段都会对环境造成 影响。从原材料的提取,到加工、制造和运输的过程,
最后到被消耗和丢弃或回收,每一个阶段都对工艺 学和化学提出了挑战。重新设计产品和过程以减少对环
境的影响需要新的生产原理和在不同的水平层面上 理解化学变化,对环境友善的产品要求有新的原料,它
们应是可再使用的,可循环的,或者可生物降解的 。物质的性质是由其化学组成和结构决定的,要减少废
品和有污染的副产品,就要开发新的化学工艺线路 ,已开发的化学分离技术需要有效地提高以分离出剩余
的污染物,这反过来又要求新的化学处理方法使它 们变得无害。而诸如放射性元素和那些不容易转化为无
害物质的重金属污染物则需要把它们固定为惰性物 质以便能安全地储放。还有最后一点,早期的污染残留
物,对环境污染程度尚未很意识到的一些物质要求 进一步用化学和生物的修复技术进行处理。

Knowledge of chemical transformations can also help in the discovery of previously unknown environmental
problems. The threat to the ozone layer posed by CFCs was correctly anticipated through fundamental studies of
atmospheric chemistry, eventually leading to international agreements for phasing out the production of these
otherwise useful chemicals in favor of equally functional but environmentally more compatible alternatives. On
the other hand, the appearance of the ozone hole over the Antarctic came as a surprise to scientists and only
subsequently was traced to previously unknown chlorine reactions occurring at the surface of nitric acid crystals in
the frigid Antarctic stratosphere. Thus it is critically important to improve our understanding of the chemical
processes in nature, whether they occur in fresh water, saltwater, soil, subterranean environments, or the
atmosphere.
了解化学反应的机理可以帮助我们发现以前不知道的环境问题,CFCs对臭氧层造成的威胁能够正确< br>地预防要得益于大气化学的基础研究。由此导致了国际上一致同意逐步取消这些产品的生产。而代之以作< br>用相同但对环境更为友善的其它产品。另一方面,南极上空臭氧空洞的出现使科学家们大为震惊,随后才< br>发现了以前所不了解的南极寒冷的平流层内硝酸晶体表面所发生的氯原子的反应。这对我们进一步了解自< br>然界中所发生的化学反应过程是非常重要的。不管这些反应是发生在淡水中,海水中,土壤里,地下环境< br>或是大气中。

3. Manufacturing with Minimal Environmental Impact
Discharge of waste chemicals to the air, water, or ground not only has a direct environmental impact, but also
constitutes a potential waste of natural resources. Early efforts to lessen the environmental impact of chemical
processes tended to focus on the removal of harmful materials from a plant’s waste stream before it was discharged
into the environment. But this approach addresses only half of the problem; for an ideal chemical process, no
harmful by- products would be formed in the first place. Any discharges would be at least as clean as the air and
water that were originally taken into the plant, and such a process would be “environmentally benign”.
3.对环境影响最小的生产
把废物 排放到空气、水或土壤中不仅对环境造成了直接的影响,还是对自然资源的一个潜在的浪费。
早期减少化 学过程对环境影响的工作主要集中在工厂废气排放如环境之前有害物质的分离,但这种思路只
考虑了问题 的一半。因为一个理想的化学过程,也就是没有有害的副产品产生的过程应在一开始就建立好,
任何排放 物至少应像进入到工厂内的空气和水一样干净。这样的过程才可以称是“与环境友善的”。

Increasing concern over adverse health effects has put a high priority on eliminating or reducing the amounts
of potentially hazardous chemicals used in industrial processes. The best course of action is to find replacement
chemicals that work as well but are less hazardous. If a substitute cannot be found for a hazardous chemical, then a


promising alternative strategy is to develop a process for generating it on-site and only in the amount needed at the
time.
对健康有害影响的关注逐渐升级,人们首先考虑到如何消除或减少工业过程中所用 有害化学物质的数
量。最好的方法是寻找替代的化学产品,它们能起到一样的作用但毒害性较小。如果不 能寻找到一种有毒
化学物质的替代品,那么比较好的战略思想是开发一种就地生产的工艺,而且只生产当 时所需要的那么多
的数量。

Innovative new chemistry has begun delivering environmentally sound processes, that use energy and raw
materials more efficiently. Recent advances in catalysis, for example, permit chemical reactions to e run at lower
temperatures and pressures. This change, in turn, reduces the energy demands of the processes and simplifies the
selection of construction materials for the processing facility. Novel catalysts are also being uses to avoid the
production of unwanted by-products.
革新的化学方法已开始设计对环境合理的工艺过程,以便更为有效的使用能量和原材料。例如,催化剂方面的近期进展使化学反应可以在较低的温度和压力下进行。反过来,这种改变又减少了这些过程的能量需求,简化了制造加工设备对构成材料的选择,新的催化剂还用于避免生产不希望的副产品。

4. Control of Power Plant Emissions
Coal-, oil-, and natural-gas-fired power generation facilities contribute to the emissions of carbon monoxide,
hydrocarbons, nitrogen oxides, and a variety of other undesired by-products such as dust and traces of mercury. A
rapidly increasing array of technologies are now available to reduce the emissions of unwanted species to meet
national or local standards. Chemists and chemical engineers have made major contributions to the state of the art,
and catalytic science is playing a critical role in defining the leading edge.
4. 发电厂排放物的控制
通过燃煤、燃油和燃烧天然气产生能量的设备都会 排放出一氧化碳、碳氢化合物、氮氧化物以及
许多其它不受欢迎的副产物如灰尘和痕量的汞。现在可以采 用一系列不断发展的技术来减少不希望有
的物质的排放以适应国家和地区标准的要求。化学家和化学工程 师对工业水平的进步做出了巨大的贡
献。而催化科学为开辟这些前沿领域正在扮演重要的角色。

The simultaneous control of more than one pollutant is the aim of some recently developed catalyst or
sorbent technologies. For example, catalytic methods allow carbon monoxide to be oxidized at the same time that
nitrogen oxides are being chemically reduced in gas turbine exhaust. Other research efforts are aimed at pilot-plant
evaluation of the simultaneous removal of sulfur and nitrogen oxides from flue gas by the action of a single
sorbent and without the generation of massive volumes of waste products.
同时控制多种污染物是近年来开发先进的催化剂或吸附剂技术的目的。例如,催化 方法可以使汽车尾
气中CO氧化的同时,还原氮的氧化物。另一些研究工作则定位于在中试阶段通过一种 吸附剂的作用同时
去除烟道气中的硫和氮氧化物,而不会产生大量的废物。

5. Environmentally Friendly Products
Increased understanding of the fate of products in the environment had led scientists to design “greener”
products. A significant early example comes from the detergent industry in the 1940s and 1950s, new products
were introduced that were based on synthetic surfactants called branched alkylbenzene sulfonates. These
detergents had higher cleaning efficiency, but it was subsequently discovered that their presence in waste water
caused foaming in streams and rivers. The problem was traced to the branched alkylbenzene sulfonates; unlike the
soaps used previously, these were not sufficiently biodegraded by the microbes in conventional sewage treatment


plants. An extensive research effort to understand the appropriate biochemical processes permitted chemists to
design and synthesize another new class of surfactants, linear alkylbenzene sulfonateas,. The similarity in
molecular structure between these new compounds and the natural fatty acids of traditional soaps allowed the
microorganisms to degrade the new formulations, and the similarity to the branched alkybenzene sulfonates
afforded outstanding detergent performance.
5. 对环境友善的产品
对产品在环境中的变化越来越了解使得科学家们开始设计“绿色”产 品。一个重要的例子来自1940-1950s
的洗涤剂工业。当时以支链烷基苯磺酸盐为表面活性剂的 新产品被引入。这些洗涤剂洗涤效率更高。但其
后发现这些物质残留在废水中在河面上形成泡沫。问题追 溯到这些支链的烷基苯磺酸盐:它不像以前人们
所使用的肥皂。它不能被传统污水处理厂的细菌所有效地 生物降解。经过深入的研究工作了解了生物化学
过程使化学家们设计和合成了另一类新型的表面活性剂, 为直链烷基苯磺酸盐。这些新的化合物与传统肥
皂中的脂肪酸有相似的分子结构,因而微生物可以降解这 些组分,而它与支链烷基苯磺酸盐的相似性又使
其具有卓越的洗涤性能。

Novel biochemistry is also helping farmers reduce the use of insecticides. Cotton plants, for example, are
being genetically modified to make them resistant to the cotton bollworm. A single gene from a naturally occurring
bacterium, when transferred into cotton plants, prompts the plant to produce a protein that is ordinarily produced
by the bacterium. When the bollworm begins to eat the plant, the protein kills the ins4ct by interrupting its
digestive processes.
新的生物化学也正在帮助农民减少使用杀虫剂. 例如,棉作物可以通过改变基因而具备对棉螟蛉的抵抗
力.天然存在的细菌中一个基因当被转移到棉作物 中时,能够祖师作物产生一种原来有细菌产生的蛋白质.当
螟蛉虫开始吃作物时,这种蛋白质通过切断螟 蛉的消化过程从而杀死害虫.

6. Recycling
Increasing problems associated with waste disposal have combined with the recognition that some raw
material exist in limited supply to dramatically increase interest in recycling. Recycling of metals and most paper
is technically straightforward, and these materials are now commonly recycled in many areas around the world.
Recycling of plastics presents greater technical challenges. Even after they are separated from other types of waste,
different plastic materials must be separated from each other. Even then, the different chemical properties of the
various types of plastic will require the development of a variety of recycling processes.
6. 处理
越来越多的环境问题与废物的排放 有关,而一些原材料又存在供给有限的问题.这二者的联系引起了人
们对处理这一课题越来越大的兴趣. 金属和大多数纸张的处理从技术上来说是简单的,这些物质在世界很多
地方都已普遍进行了处理.塑料的 处理则面临着较大的技术方面的挑战.即使把它们与其它类型的废品分离
开来以后,不同种类的塑料还需 要再彼此分离。即使如此,不同类型的塑料具有不同的化学性质,因而也
需要开发不同的处理工艺.

Some plastics can be recycled by simply melting and molding them or by dissolving them in an appropriate
solvent and then reformulating them into a new plastic material. Other materials require more complex treatment,
such as breaking down large polymer molecules into smaller subunits that can subsequently be used as building
blocks for new polymers. Indeed, a major program to recycle plastic soft drink bottles by this route is now in use.
一些塑料可以通过简单地熔化注塑或用合适的 溶剂进行分解再重新塑造成新塑料的方法进行处理。比
如,把大的聚合物分子裂解成较小的亚单元,再以 此作为新聚合物的结构单元。确实,用这种方法处理软塑
料瓶的计划正在进行中。



A great deal of research by chemists and chemical engineers will be needed to successfully develop the
needed recycling technologies. In some cases, it will be necessary to develop entirely new polymers with
molecular structures that are more amenable to the recycling process.
化学家和化学工程师们所做的大量的研究工作需要被 成功地开发为所需要的处理技术。有时,也需要
开发一些全新的聚合材料.它们具有更容易进行处理的分 子结构.

7. Separation and Conversion for Waste Reduction
New processes are needed to separate waste components requiring special disposal from those that can be
recycled or disposed of by normal means. Development of these processes will require extensive research to obtain
a fundamental understanding of the chemical phenomena involved.
7. 通过分离和转换减少废物量
把一些需要进行特殊处理的成分从那些可用常规方法处理或处置的废物中分离出来需要新的工艺过
程。而开发这些过程则需要深入研究以从根本上了解所涉及的化学现象.

Metal- bearing spent acid waste. Several industrial processes produce acidic waste solutions in large
quantities. Could this waste be separated into clean water, reusable acid, and a sludge from which the metals could
be recovered? Such processes would preserve the environment, and their costs could be competitive with disposal
costs and penalties.
含金属离子的酸性废水.一些工业过程产生了大 量的酸性废水.这些废水可以分离成干净的水、可再利
用的酸、以及可从中提取出可回收金属的淤渣吗? 这样的处理过程既可以保护环境,所需费用又与处置废
水所需成本及罚款相差无几。

Industrial waste treatment. The hazardous organic components in industrial wastewater could be destroyed
with thermocatalytic or photocatalytic processes. A promising line of research employs “supercritical” water at
high temperatures and pressures. Under these conditions, water exhibits very different chemical and physical
properties. It dissolves reactions of many materials that are nearly inert under normal conditions.
工业废水处理。工业废水中的有害有机物能被热 催化或光催化的过程破坏。一项前景很好的研究工作
是利用高温高压下的超临界水。在这种条件下,水表 现出截然不同的物理和化学性质,它可以溶解并有助
于那些在常态下的水中几乎是惰性的物质发生反应。

High-level nuclear waste. Substantial savings would be achieved if the volume and complexity of nuclear
waste requiring storage could be significantly reduced; this reduction would require economic separation of the
radioactive components from the large volumes of other materials that accompany the nuclear waste. The
hazardous chemical waste mighty then be disposed of separately. The dispose of nuclear waste will require major
research and development efforts over many years.
高辐射的核废料。如 果需要储藏的核废料其数量和组成能够显著地减少,就可以节省一大笔的费用。
这种减少需要用经济的方 法把放射性成分与大量其它与核废料共存的物质分离开来,这样有害的化学废料
就可以分别地进行处置, 核废料的处置仍将需要今后许多年进行大量的研究和开发工作。

Membrane technology. Separations involving semi permeable membranes offer considerable promise. These
membranes, usually sheets of polymers, are impervious to some kinds of chemicals but not to others. Such
membranes are used to purify water, leaving behind dissolved salts and providing clean drinking water. Membrane
separations are also applicable to gases and are being used for the recovery of minor components in natural gas, to


enhance the heating value of natural gas by removal of carbon dioxide, and for the recovery of nitrogen from air.
Research challenges include the development of membranes that are chemically and physically more resilient, that
are less expensive to manufacture, and that provide better separation efficiencies to reduce processing costs.
膜技术。应用半渗透性薄膜进行分离大有希望获得成功。这些膜通常是片状聚合物。能够 让一些化学
物质通过而不让另一些物质通过。这些膜常用来纯化水,阻挡住一些溶解的盐类提供干净的饮 用水。膜分
离技术也用来提纯制造厂出来的废水。膜分离还可以用在气体方面,用来回收天然气中的微量 组分。通过
清除CO提高天然气的热值,以及从空气中得到氮气。研究中的难点包括开发化学和物理学方 面更有弹性
的膜。这样可以使制造费用不那么贵,并且可以提供更好的分离效率以降低分离成本。

Biotechnology. Scientists have turned to nature for help in destroying toxic substances. Some
microorganisms in soil, water, and sediments can adapt their diets to a wide variety of organic chemicals; they
have been used for decades in conventional waste treatment systems. Researchers are now attempting t coax even
higher levels of performance from these gifted microbes by carefully determining the optimal physical, chemical,
and nutritional conditions for their existence. Their efforts may lead to the design and operation of a new
generation of biological waste treatment facilities. A major advance in recent years is the immobilization of such
microorganisms in bioreactors, anchoring them in a reactor while they degrade waste materials. Immobilization
permits high flow rates that would flush out conventional reactors, and the use of new, highly porous support
materials allows a significant increase in the number of microorganisms for each reactor.
生物 技术。科学家们已经向自然界寻求帮助战胜有毒物质。土壤、水和沉积物中的一些微生物能以许
多有机化 学物质为食。数十年来它们一直被用于传统的水处理系统。研究者们正通过仔细测量微生物生存
的最佳物 理、化学和营养条件致力于处理强度更高的对象。他们的工作可能导致设计和生产新一代生物废
水处理设 备。近年来的一个很大的进展是生物反应器内微生物的固定。即把微生物固定在反应器内降解废
物。这种 固定可以允许有更高的流速。传统反应器内流速过高会冲走微生物。新的多孔载体的使用也使每
个反应器 中微生物的数量明显提高。
























Excel in Your Engineering

When I reflect on my 20-plus years of experience as a chemical engineer, I realize how wonderful my
profession is. As engineers, we provide the essential link between technology and humanity. Our job is to make the
world better for its human inhabitants while protecting the environment. And we fulfill our mission amongst the
demands and guidelines of the business world.
But sometimes we get so bogged down in the everyday aspects of our jobs that we lose sight of the big
picture. We forget to appreciate engineering—though it is challenging, creative, interesting, significant, and even
fun.
For example, there’s nothing like getting engrossed in a tough technical problem and coming up with a neat
solution. Do you find yourself hurrying to the office because you look forward to working? Do you ever wake up
in the middle of the night thinking about a problem and lie there working out the details of a brilliant solution? Do
you get up to write notes so you won’t forget your breakthrough in the morning?
Engineering can be that wonderful. And being involved in your work doesn’t mean you’re a nut or a
workaholic. We should like what we do: Enjoying something and doing it well is a “chicken-and-egg” situation.
We tend to like activities we perform well, and to be good at things we enjoy. So here’s some advice for both
enjoying and improving your engineering work.
1. Enhance technical skills
Engineering provides many opportunities to develop existing skills and to learn new ones. In fact, we have to
keep learning or we atrophy--that’s the nature of any profession. The ability to grow is one reward of a good job.
As your interests and involvements change, and as technology changes, you need to keep learning.
2. Hone interpersonal skills
Not all the development opportunities relate to technical matters. Successful engineering practice is strongly
dependent on interpersonal and communications skills. It’s important to learn about people, motivation,
organizational behavior, written and oral communication and visual aids. With these skills as with any others,
practice makes perfect (or at least very proficient).
In addition, remember that we are also “business people” and, as such, should keep up on trends in the
business world, particularly in our industry. These communications skills can help develop relations both within
and outside the company.
Activities outside of the workplace can be good opportunities for enhancing nontechnical skills. They can
help you improve interpersonal, leadership and communication capabilities.
For example, it’s easy to get into leadership positions in volunteer organizations. All you have to do is attend
some meetings and show that you’re willing to help out, and soon you’ll move right into whatever you want to do.
3. Do the whole job
You’re probably familiar with the concept of “completed staff work” (CSW). According to this concept, a
subordinate presents his or her boss with solutions, or at least options, rather than problems. The reasoning is that
the person closes to the problem is better prepared than anyone—even the boss—to make a decision and to
implement it. Decision are best made at the lowest practical level.
Before passing your work on to the boss, try to make the work as complete as you can. That means not only
writing the report, but also the cover letter and any transmittal notes it will need to flow smoothly through channels.


Think through any political ramifications and make appropriate contacts to preclude problems. Anticipate
questions and prepare for them. If your boss looks good, you look good.
By maximizing the quality and quantity of your work, you maximize your value to your employer. Learn to
do many things well. Be the engineer who can write a project proposal, plan and perform experiments, design
equipment, analyze data, develop a mathematical model, write and present results, and bring in the next job. If you
do it yourself—or lead others in doing it—or you will be indispensable.
the big picture
Many engineers with little experience view their job too narrowly. They’re content to just do what they’re
asked. They may be creative in carrying out designated tasks, and they may see some minor extensions of it, but
they don’t explore widely enough.
But the “big picture” is not just the concern of higher-level people. Everything that happens in the company
affects all of its employees. In turn, each employee can contribute to the well being of the company.
You can get involved in long-range planning, business development, and diversification into new products or
services. The people who are already involved in these matters will welcome your help. Although you might start
out with a small role, you will soon be contributing more and more. Such efforts often begin by demanding a little
more of your personal time, but are later sanctioned by your supervisors as you prove your capability.
a leader
There’s always a need for leadership of technical activities, and many engineers are suited to this. Leaders
aren’t born; leadership skills are developed.
Leadership is different from management. For example, consider a large group of people in a jungle; their
task is to cut a path through the underbrush. Managers recruit the workers, teach them how to use a machete,
provide them with appropriate clothing, arrange their transportation to the job site and ensure that they are fed.
But the leader is the one at the front of the group, showing them where to cut the path. Pr perhaps the leader
tells the group that this is the wrong jungle and they need to go elsewhere.
Managers take charge f administrative, executive and business matters. They supervise employees’ work to
make sure that operations are flowing smoothly. Leaders, on the other hand, are those who break ground, bring in
new technologies, and point the way toward innovation.
You don’t have to have any assigned management responsibility to be a leader. People respond to
leaders—with or without prestigious titles.
As a matter of fact, you may be able to develop true leadership skills better if you don’t have administrative
responsibilities. When you don’t have jurisdictional authority over people, you find other ways to influence them.
Instead of ordering people to do things, you make them want to do them—and that is the best way.
6. Be a mentor
As we gain experience, we can help younger engineers develop their potential. People pick up a lot of their
attitudes toward work, approaches to problems, and working methods from their senior colleagues. If you are a
senior engineer, your impact on new employees is particularly strong and important.
New engineer should be able to take a sufficiently broad view of their jobs and not limits themselves. It is
rewarding to accomplish work through others, to see them develop into stronger engineers and move into positions
of more responsibility.
Sometimes part of your success as an engineer may be hiring or training someone who goes on to do things
you can do yourself. You can help a promising engineer with capabilities beyond your own. And if you have a
hand in developing someone who goes on to a really high position in your company, be proud of your
accomplishment.
7. Beware of diversions


A multifaceted profession, engineering involves other disciplines. But think about your chosen path before
becoming involved in a peripheral area.
For example, many engineers become enamored with computers. Today is personal computers can certainly
enhance out productivity. Remember, however, that a computer is a tool just like a telephone or a calculator. Do
not let yourself value the means over the end. If you are working on computer tasks that support personnel can do
more efficiently, you are probably not employing your time well.
Some engineers are so fascinated to computers that they have in reality shifted from being engineers to being
computer scientists. There’s certainly merit in doing what you enjoy, but issue a caution. Remember that you had
good reasons for going into engineering in the first place, and if you drift into another area, you may later find it
difficult to return to your engineering duties.
Management is another popular diversion. For some engineers, going into management is a positive move.
Management is challenging and rewarding, and many engineers are well suited to it. In addition, having an
engineer-turned-manager is helpful to the other engineers. Moving in and out of management position, especially
in the lower levels of management, can actually be good for an engineer’s career.
However, the longer you stay in management, the more you run the risk of no longer being able to return to
engineering. Most engineers who move into lower-level management positions are wise to regard them as a
temporary diversion from their true profession.
8. Keep fit
Good health is essential to doing a good job. When you’re fit, you have more energy and feel better generally.
Thus you can put more onto your work, a well as into there aspects of your life. Because most engineers have
predominantly sedentary jobs, it is important to eat carefully and get enough exercise.
9. Enjoy your profession
As professional engineers, we need to keep developing and broadening our skills. We need to expand the
scope of our work and reach the full potential we have, to the benefit of both ourselves and our employer. For most
engineers, the best job security is being able to do high-quality engineering work, which is always in great demand.
Finally, we should relish the varied challenges and excitement that constitute engineering at its best.




Curriculum of chemical engineering

As chemical engineering knowledge developed, it was inserted into university courses and curricula. Before
World WarⅠ, chemical engineering programs were distinguishable from chemistry programs in that they
contained courses in engineering drawing, engineering thermodynamics, mechanics, and hydraulics taken from
engineering departments. Shortly after World WarⅠthe first text in unit operations was published. Courses in this
area became the core of chemical engineering teaching.
By the mid-1930s, chemical engineering programs included courses in (1) stoichiometry (using material and
energy conservation ideas to analyze chemical process steps), (2) chemical processes or “unit operations”, (3)
chemical engineering laboratories “in which equipment was operated and tested”, and (4) chemical plant design (in
which cost factors were combined with technical elements to arrive at preliminary plant designs). The student was
still asked to take the core chemistry courses, including general, analytical, organic, and physical chemistry.
However, in addition, he or she took courses in mechanical drawing, engineering mechanics, electric circuits,
metallurgy, and thermo- dynamics with other engineers.


Since World War Ⅱ chemical engineering has develop rapidly. As new disciplines have proven useful, they
have been added to the curriculum. Chemical engineering thermodynamics became generally formulated and
taught by about 1945. By 1950, courses in applied chemical kinetics and chemical reactor design appeared.
Process control appeared as an undergraduate course in about 1955, and digital computer use began to develop
about 1960.
The idea that the various unit operations depended on common mechanisms of heat, mass, and momentum
transfer developed about 1960. Consequently, courses in transport phenomena assumed an important position as an
underlying, unifying basis for chemical engineering education. New general disciplines that have emerged in the
last two decades include environmental and safety engineering, biotechnology, and electronics manufacturing
processing. There has been an enormous amount of development in all fields, much of it arising out of more
powerful computing and applied mathematics capabilities.

1. Science and Mathematics Courses
Chemistry
Chemical engineers continue to need background in organic, inorganic and physical chemistry, but also
should introduced to the principles of instrumental analysis and biochemistry.
· Valuable conceptual material should be strongly emphasized in organic chemistry including that associated
with biochemical process.
· Much of thermodynamic is more efficiently taught in chemical engineering, and physical chemistry should
include the foundations of thermodynamic.
Physics.
Biology.
· Biology has emerged from the classification stage, and modern molecular biology holds great promise for
application. Future graduates will become involved with applying this knowledge at some time in their careers.
· A special course is required on the functions and characteristics of living cells with some emphasis on
genetic engineering as practiced with microorganisms.
Materials Science.
· Course work should include the effects of microstructure on physical, chemical, optical, magnetic and
electronic properties of solids.
· Fields of study should encompass ceramics, polymers, semiconductors, metals, and composites.
Mathematics.
Computer Instruction.
· Although students should develop reasonable proficiency in programming, the main thrust should be that
use of standard software including the merging of various programs to accomplish a given task. Major emphasis
should be on how to analyze and solve problems with existing software including that for simulation to evaluate
and check such software with thoroughness and precision.
· Students should learn how to critically evaluate programs written by others.
· All courses involving calculations should make extensive use of the computer and the latest software. Such
activity should be more frequent as students progress in the curriculum. Adequate computer hardware and software
must be freely available to the student through superior centralized facilities andor individual PC’s. Development
of professionally written software for chemical engineering should be encouraged.

2. Chemical engineering courses
Thermodynamics.


· The important concepts of the courses should be emphasized; software should e developed to implement
the concepts in treating a wide variety of complex, yet interesting, problems in a reasonable time. The value of
analysis of units and dimensions in checking problems should continue to be emphasized.
· Examples in thermodynamics should involve problems from a variety of industries so that the subject
comes alive and its power in decision making is clearly emphasized.
Kinetics, Catalysis, and Reactor Design and Analysis.
· This course also needs a broad variety of real problems, not only design but also diagnostic and economic
problems. Real problems involve real compounds and the chemistry related to them.
· Existing software for algebraic and differential equation solving make simulation and design calculation on
many reactor systems quite straightforward.
· Shortcut estimating methods should be emphasized in addition to computer calculations.
· The increased production of specialties make batch ad semibatch reactor more important, and scale-up of
laboratory studies is an important technique in the fast-moving specialties business.

3. Unit Operations
The unit operations were conceived as an organized means for discussing the many kind of
equipment-oriented physical processes required in the process industries. This approach continues to be valid.
Over the years some portions have bee given separate status such as transport phenomena and separations while
some equipment and related principles have not been included in the required courses, as is the case with polymer
processing, an area in which all chemical engineers should have some knowledge.
·Transport phenomena principles can be made more compelling by using problems form a wide range of
industries that can be analyzed and solved using the principles taught.
·Some efficiency may be gained by teaching several principles and procedures for developing specifications
and selection the large number of equipment items normally purchased off-the- shelf or as standard design.
·A great deal of time can be saved in addressing designed equipped such as fractionators and absorbers be
emphasizing rigorous computer calculations and the simplest shortcut procedures. Most intermediate calculation
procedures and graphical methods should be eliminated unless they have real conceptual value.
Process Control.
·This course should emphasize control strategy and precise measurement in addition to theory.
·Some hands-on experience using current practices of computer control with industrial-type consoles should
be encouraged.
·Computer simulation of processes for demonstration of control principles and techniques can be most
valuable, but contact with actual control devices should not be ignored.
Chemical engineering laboratories.
·Creative problem solving should be emphasized.
·Reports should be written as briefly as possible; they should contain an executive summary with clearly
drawn conclusions and brief observations and explanations with graphical rather than tabular representation of data.
A great deal of such graphing can be done in the laboratory on computers with modern graphics capabilities.
Detailed calculations should be included in an appendix.
·Some part of the laboratory should be structured to relate to product development,
DesignEconomics
·In the design course in engineering, students learn the techniques of complex problem solving and decision
making within a framework of economic analysis. The very nature of processes requires a system approach’ the
ability to analyze a total system is one of the special attributes of chemical engineers that will continue to prove


most sought after in a complex technological world.
·Because of the greater diversity of interests and job opportunities, some consideration should be given to
providing a variety of short design problem of greatest personal interest.
·The design approach can be most valuable in diagnosing plant problems, and some practice in this
interesting area should be provided.
·Rigorous economic analysis and predictive efforts should be required in all decision processes.
·Safety and environmental considerations should also be emphasized.
·Modern simulation tools should be made available to the students.
Other Engineering Courses.
The electrical engineering courses should emphasize application of microprocessors, lasers, sensing devices,
and control systems as well as the traditional areas of circuits and motors. The course should provide insight into
the principles on which each subject is based.
Remaining courses in engineering mechanics and engineering drawing should be considered for their
relevance to current and future chemical engineering practice.

4. Other courses
Economics and Business courses.
It is difficult to find a single course in economics or business departments that covers the various needs
of engineers. The qualitative ability of engineers makes it possible to teach following topics in a
single-semester course—in many cases in the Chemical Engineering Department: business economics,
project economic analysis, economic theory, marketing and market studies, and national and global
economics.
Humanities and Social Science Courses.
It is important to understand the origins of one’s own culture as well as that of others.
Communication Course.
Since improved communication skills require continuous attention, the following requirements may be
useful:
·Oral presentations in at least one course each year.
·Several literature surveys in the junior and senior years.
·Introduce computer-based communication systems.
Area of Specialization.
The elective areas should be generous in hours to maximize freedom of choice. Each department will
have to consider its own and its total university resources and strenghs as well as the quality and preparation
of its students. The suggested areas are:
·Life sciences and applications
·Materials sciences and applications
·Catalysis and electrochemical science and applications
·Separations technology
·Computer applications technology
·Techniques of product development and marketing
·Polymer technology
Each of these areas should be strongly career-oriented. The interest in a given area will depend on
opportunities perceived by the students.


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