ABSTRACT
In many industrial sectors, including the chemical, food, and biological processing industries, there are many similarities in the manner in which the entering feed materials are modied or processed into nal products. These seemingly different physical, chemical, or biological processes can be broken down into a series of separate and distinct steps called unit operations. These unit operations are common to all types of diverse, process industries. For example, the unit operation distillation is used to purify or separate alcohol in the beverage industry and hydrocarbons in the petroleum industry. Drying of grain and other foods is similar to drying of lumber, ltered precipitates, and rayon yarn. The unit operation absorption occurs in the absorption of oxygen from air in a fermentation process or in a wastewater treatment plant and in absorption of hydrogen gas in a process for liquid hydrogenation of oil. Evaporation of salt solutions in the chemical industry is similar to evaporation of sugar solutions in the food industry. Settling and sedimentation of suspended solids are similar in the wastewater and the mining industries. Flow of liquid hydrocarbons in the petroleum renery and ow of milk in a dairy plant are carried out in a similar fashion. Thus, the most efcient method of organizing the subject matter of unit operations is based on two facts:
1. Although the number of individual processes is great, each one may be separated into a series of steps, called operations, each of which in turn appears in process after process; and
2. Individual operations have common techniques and are based on the same scientic principles.
