Chemical EngineeringChemical engineering is the development of processes and the design and operation of plants in which materials undergo changes in physical or chemical state on a technical scale.化学工程是过程的开发和工厂的设计与操作，在工厂中材料以某种技术规模进行的物理或化学状态的变化。
Applied throughout the process industries, it is founded on the principles of chemical, physics, and mathematics.它建立在化学、物理和数学的原则上，适用于整个流程工业。
The laws of physical chemistry and physics govern the practicability and efficiency of chemical engineering operations.物理化学和物理定律支配着化工业务的实用性和效率。
Energy changes, deriving from thermodynamic considerations, are particularly important.能量的变化，从热力学考虑派生，显得尤其重要。
Mathematics is a basic tool in optimization and modeling.数学是一个优化和建模的基本工具。
Optimization means arranging materials, facilities, and energy to yield as productive and economical an operation as possible.优化意味着合理安排材料、设备和能源，尽可能生产经济多产的操作。
Modeling is the construction of theoretical mathematical prototypes of complex process systems, commonly with the aid of computers.建模是将复杂过程系统建设出其理论数学原型的过程，通常需要借助电脑完成。
Chemical engineering is as old as the process industries.化学工程和过程工业一样古老。
Its heritage dates from the fermentation and evaporation processes operated by early civilizations.其遗产起源于早期文明的发酵和蒸发过程。
Modern chemical engineering emerged with the the development of large-scale, chemical-manufacturing operations in the second half of the 19th century.在19世纪下半叶，随着大规模的化学制造业操作的发展，现代化学工程出现了。
Throughout its development as an independent discipline, chemical engineering has been directed toward solving problems of designing and operating large plants for continuous production.化学工程作为一门独立的学科，纵观其发展过程，它已经朝向解决设计问题和经营连续生产的大型工厂的问题。
Manufacture of chemicals in the mid-19th century consisted of modest craft operations.在19世纪中叶，化工生产由小型的手工操作组成。
Increase in demand, public concern at the emission of noxious effluents, and competition between rival processes provided the incentives for greater efficiency.需求的增加，公众对有害物质排放的关注，和与对手的竞争过程为创造更高效率提供了激励机制。
This led to the emergence of combines with resources for larger operations and caused the transition from a craft to a science-based industry.这导致了更大的操作与资源相结合的联合工厂的出现，引起了从手工业到一个以科学为基础的产业（科技工厂）的过渡。
The result was a demand for chemists with knowledge of manufacturing processes, known as industrial chemists or chemical technologists.其结果是应了具有制作过程知识的化学家的要求，这是为工业化学家或化工技师所知晓的The term chemical engineer was in general use by about 1900.化学工程师一词广泛应用了约1900年。
Despite its emergence in traditional chemicals manufacturing, it was through its role in the development of the petroleum industry that chemical engineering became firmly established as a unique discipline.尽管出现在传统的化学品制造中，但它的价值却是通过其在石油工业——这门由化工工程牢固建立成的独立学科来实现的。
The demand for plants capable of operating physical separation processes continuously at high levels of efficiency was a challenge that could not be met by the traditional chemist or mechanical engineer.工厂的需求是能够高效连续地进行物理分离过程的操作，这是传统的化学家或工程师无法迎接的挑战。
A landmark in the development of chemical engineering was the publication in 1901 of the first textbook on the subject, by George E. Davis, a British chemical consultant. 化学工程发展的一个里程碑是1901年，一个英国化学顾问乔治·E·戴维斯出版的关于此话题的教科书。
This concentrated on the design of plant items for specific operations.这本书集中描述了设计工厂项目的具体操作。
The notion of a processing plant encompassing a number of operations, such as mixing, evaporation, and filtration, and of these operations being essentially similar, whatever the product, led to the concept of unit operations.注意到加工厂包括的一系列操作，如混合、蒸发、过滤，无论产物是什么，这些操作都基本相同，从而导致了单元操作的概念。
This was first enunciated by the American chemical engineer Arthur D. Little in 1915 and formed the basis for a classification of chemical engineering that dominated the subject for the next 40 years.这被美国化学工程师理特于1915年首次解释，形成了化学工程分类的基础，主导了未来40年的主题。
The number of unit operations—the building blocks of a chemical plant—is not large. 单元操作的数目——一个化工厂的建设模块数并不大。
The complexity arises from the variety of conditions under which the unit operations are conducted.复杂性来自于单元操作进行的条件的多样性。
In the same way that a complex plant can be divided into basic unit operations, so chemical reactions involved in the process industries can be classified into certain groups, or unit processes(e.g., polymerizations, esterifications, and nitrations), having common characteristics.同复杂的工厂可划分为基本的单元操作一样，过程工业中涉及到的化学反应也可分成一定的单元过程（如聚合、酯化和硝化），它们具有共同的特性。
This classification into unit processes brought rationalization to the study of process engineering.单元过程的这种分类对于过程工程的研究是合理的。