1、,Unit 1 （2） Unit Operations,Corrections:P.6 line 3, “characterstics” haracteristics”P.8 line 10, “rate” “rates”,Chemical processes may consist of(由.组成) widely varying sequences of steps, the principles of which are independent of(与无关,不受的制约)the material being operated upon and of other characteristic
2、s of the particular system.化工过程包括的各种步骤的顺序变化很大，这些步骤的原理与处理的物料及特定体系的其它性质无关。,In the design of a process(在工艺设计中), each step to be used can be studied individually（个别地；逐一地） if the steps are recognized(区分，识别). 在工艺设计中，如果用到的每个步骤都可以被区分开，那么就可以对它们分别进行研究。,Some of the steps are chemical reactions, whereas（然而）othe
3、rs are physical changes.这些步骤中有些是化学反应，而另一些是物理变化。,The versatility（通用性）of chemical engineering originates（引起，产生）in training to the practice of breaking up （分解） a complex process into individual physical steps, called unit operations, and into the chemical reactions.,化学工程的通用性使人们在实际工作中可以把复杂的过程分为单个的物理步骤（称
4、为单元操作）和化学反应。,The unit-operations concept in chemical engineering is based on the philosophy（哲学）that the widely varying sequences of steps can be reduced to（简化为，还原成）simple operations or reactions, which are identical in（在方面是相等的）fundamentals（基本原理）regardless of the material being processed.,化学工程中的单元操作概
5、念是基于以下观点提出的：这些变化很大的步骤可以简化为简单的操作或反应，如果不考虑被处理的物料，它们在基本原理上也是相同的。,This principle, which became obvious（明显的、公认的 ）to the pioneers during the development of chemical industry, was first clearly presented（提出）by A.D. Little in 1915. 这些在化学工业发展中被先驱们所承认的原理，是由A.D. Little在1915年首先提出的。,“Any chemical process, on wha
6、tever scale conducted（操作，行为）, may be resolved into（被分解为）a coordinated（协调，配合）series of what may be termed unit actions, as pulverizing粉碎, mixing, heating, roasting焙烧，（bake烤, 烘）, absorbing, condensing, lixiviating浸出, precipitating沉淀, crystallizing, filtering, dissolving, electrolyzing电解and so on .,任何化
7、学过程，无论它的规模如何，都可以分解为与之等同的一系列单元操作，例如：粉碎、混合、加热、焙烧、吸收、冷凝、浸出、沉淀、结晶、过滤、溶解和电解等。,The number of these basic unit operations is not very large and relatively （相对地）few of them are involved in（包含在，与有关）any particular process. 这些基本单元操作的数量并不是很大，并且在一个特定过程中所涉及到的单元操作也不多。,The complexity （复杂性）of chemical engineering re
8、sult from（由引起，起因于）the variety变化，多样化 of conditions as to temperature, pressure, etc., under which the unit actions must be carried out in different processes and from the limitations as materials of construction建造 and design of apparatus设备imposed（产生影响，受制于）by the physical and chemical character of the
9、 reacting substance.,化学工程的复杂性起因于以下两点：（1）温度压力等条件的多样性，而不同过程中的单元操作必然是在这种差异很大的条件下实现的；（2）受到设备设计和制造材料的限制，而选用设备和材料又受制于反应物质的物理和化学性质。,The original（最初的）listing （列表） of the unit operations quoted（引用）above names twelve actions, not all of which are considered （认为， 视为） unit operations.,上面引用的最初列出的“单元操作”只能称为十二种操作，
10、但并不是所有的都被认为单元操作。,Additional ones have been designated（指出，指明）since then, at a modest（合适的，适度的）rate over the years but recently at an accelerating rate. 后来，人们又陆续提出了一些新的单元操作，而近来提出的速度又有所加快。,Fluid flow流体流动, heat transfer, distillation, humidification增湿, gas absorption, sedimentation沉积, classification, agi
11、tation搅拌, and centrifugation离心分离have long been recognized.流体流动、热传递、精馏、增湿、气体吸收、沉积、分类、搅拌和离心分离等都已被人们认可。,In recent years, increasing understanding of new techniques- and adaptation （适应,适合，改编，改写）of old but seldom used separative techniques-has led to（导致，通向）a continually increasing number of separations,
12、processing operations, or steps in a manufacture制造，生产 that could be used without significant （有效的） alteration（替换）in a variety of processes.,近年来，随着对新技术理解的增加和对很少用的过时的分离技术的改编，导致了分离、加工操作和生产中不能用其它有效操作代替的步骤增加。,This is the basis of a terminology(术语)of unit operations, which now offers(提供)us a list of techn
13、iques, all of which cannot be covered in a reasonable(有道理的，合理的) text.这是术语“单元操作”的基础，它给我们提供了一系列即使在较好的教科书中也不能全部包括的技术。,Very frequently chemical changes occur(出现，发生)in a material being distilled or heated.在物料蒸馏或加热的过程中常发生许多化学变化。,In such cases the physical operation is the primary concern关心，关注, and if a ch
14、emical change occurs simultaneously, it is commonly handled处理by a modification修正of the physical of the material.在这样的情况下，首先关注物理操作，如果同时发生化学变化，通常通过修正物料的物理性质来处理。,When chemical rates and equilibria(化学反应速度和化学平衡)are known, these may be mathematically modeled into the unit operation calculations.,如果已知化学反应速度
15、和化学平衡，就可以用数学模型对单元操作进行计算。,The typical chemical manufacturing operation involves a few chemical steps that are probably straightforward（简单的）and well understood.典型的化学生产操作包含几个化学步骤，这些化学步骤很可能是简单并且容易理解的。,Extensive广大的，广泛的equipment and operations are usually needed for refining精制，提纯 or further preparing the
16、often complex mixture for use as an end product.对作为最终产物的复杂混合物进行提纯或进一步处理，需要大量的设备和操作。,The result is that the work of the typical process engineer is much more concerned with关注，关心physical changes than with chemical reactions .,结果是，典型的工艺工程师的工作相对于化学反应更加关注物理变化。,The importance of the chemical reactions mus
17、t not be overlooked忽视because of the economic importance重要性，价值of small improvements in percentage百分数, 百分率 yield产率from chemical reactions.但是，化学反应的重要性并不能被忽视，这是因为化学反应中，即使很小的百分产率的提高，也会对经济效益产生很大的影响。,In many cases a relatively small percentage improvement in yield may economically在经济上justify（调整）considerabl
18、y more extensive processing operations过程操作and equipment.,许多情况下，一个很小的百分产率的提高，可能会引起在经济上对更大范围的过程操作和设备进行调整。,All unit operations are based upon principles of science that are translated into把译为，把转变成industrial applications in various fields of engineering.所有单元操作依据的是在工程的各个领域可能转化为工业应用的科学原理。,The flow of flui
19、ds, for instance, has been studied extensively广泛的； 详尽的in theory under the name of hydrodynamics流体动力学or fluid mechanics机械学，力学.例如，流体的流动，已经在流体动力学和流体力学两个方面进行了广泛的理论研究。,It has been important part of the work of civil engineers土木工程师under the name of hydraulics水力学and is of major importance in sanitary卫生的，排水
20、的engineering.水力学一直是土木工程师很重要的一部分工作，并且在排水工程中也非常重要。,Problems of water supply and control have been met by every civilization文明国家;有一定经济文化的地方.,每个社会都会遇到给排水问题。,Heat transfer has been the subject of many theoretical investigations by physicists and mathematicians; it has played a major part in the generatio
21、n of power from fuels, as developed by mechanical engineers.传热是物理学家和数学家进行广泛理论研究的课题，随着机械工程师的更深入开发，使得它在燃料发电厂中起着主导的作用。,Dissipation消耗，分散of heat in electrical equipment电气设备is a major limitation on the power output输出of such machinery.,电厂的输出功率主要取决于发电设备中的热消耗。,Pyrometallurgy高温冶金and the heat treatment of mate
22、rials of construction建筑and tools represent代表additional major applications. 建筑材料和工具材料的冶炼和热处理是另一具有代表性的应用。,Throughout industry, one finds examples of most of the unit operations on applications that are in the province领域of other engineering fields.纵观整个工业，人们可以找到这样的例子：大部分应用中的单元操作也应用于其它工程领域。,The chemical
23、engineer must carry out完成, 实现many unit operations on materials of widely varying physical and chemical properties under extremes极端,末端of conditions such as temperature and pressure.,化学工程师必须在温度和压力差异很大的条件下，对物理和化学性质变化很大的物料进行许多单元操作。,The unit operations used to separate mixtures into more or less pure substances are unique唯一的, 独特的to chemical engineering.,将混合物分成更多或更少纯净物质的单元操作是化学工程特有的。,The materials being processed may be naturally occurring存在mixture or they may be the products of chemical reactions, which virtually实际上；事实上never yield a pure substance. 处理的物料可能是天然的混合物，或是化学反应的产物，实际上根本不可能得到纯的物质。,
