Separation Process Principles1

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A chemical process involves different modes of operation, conducted in either a batchwise, continuous, or semicontinuous manner. The operations may be classified as either key operations (which are unique to chemical engineering because they involve changes in chemical composition): (1) chemical reaction, (2) separation of a mixture of chemicals.
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Chapter 1 Separation Processes
The chemical mixtures are separated into their constituents, as an art, for millennia. Early civilizations developed techniques to (1) extract metals from ores, perfumes from flowers, dyes from plants, and potash from the ashes of burnt plants, (2) evaporate sea water to obtain salt, (3) refine rock asphalt, and (4) distill liquors. The human body could not function for long if it had no kidney, a membrane that selectively removes water and waste products of metabolism from blood. Separations: enrichment concentration purification refining isolation Are important to chemists and chemical engineers.
Clean fuel gas LPG Sulfur Motor gasoline Crude oil Oil refinery Diesel fuel Jet fuel Lubricants Waxes Fuel oils Coke Asphalt
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Figure 1.1 Refinery for converting crude oil into a variety of marketable products
Central South University
Separation Process Principles
J.D. Seader, Ernest J. Henley Lecturer: Tao Zhou
About the Authors
• J.D. Seader is Professor of Chem. Eng. at the Univ. of Utah. He received B.S. degrees from the Univ. of California at Berkeley and a Ph.D. from the Univ. of Wisconsin. From 1952 to 1959, Seader designed processes for Chevron Research, and from 1959 to 1965, he conducted rocket engine research for Rocketdyne. Before joining the faculty at the University of Utah, he was a professor at the university of Idaho. Combined, he has authored or coauthored 102 technical articles, six books, and 4 patents, and also coauthored the section on distillation in the 6th and 7th editions of Perry’s Chemical Engineers’ Handbook. Seader has been a trustee of CACHE for 26 years, serving as an executive officer from 1980 to 1984. For 20 years, he directed the use and distribution of Monsanto’s FLOWTRAN process simulation computer program for various universities. Seader also served a director of AIChE from 1983 to 1985. In 1983, he presented the 35th Annual Institute Lecture of AIChE, and in 1988, received the computing in Chemical Engineering Award of the CAST Division of AIChE. Ernest J. Henley Professor of Chemical Engineering at the University of Houston B.S. University of Delaware Dr. Eng. Sci. Columbia University 1953-1959 Professor at Columbia University. He also has held professorships at Stevens Institute of Technol., Univ. Of Brazil, Stanford Univ., Cambridge Univ., and City Univ. of New York. He authored or coauthored 72 technical articles, 12 books, and 9 patents. For 17 years, he was a trustee of CACHE, serving as President from 1975 to 1976 and directing the efforts that produced the 7-volume set of “Computer programs for Chem. Eng. Education” and the 5-volume set “AIChE Modular Instruction”. As active consultant, he serves on the Board of Directors of Maxxim Medical Inc., Procedyne Inc., Lasermedics Inc., and Nanodyne Inc.
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1.1 Industrial chemical processes
• The chemical industry manufactures products that differ in chemical content from process feeds, which can be 1) naturally occurring raw materials, 2) plant or animal matter, 3) chemical intermediates, 4) chemicals of commerce, or 5) wastes products. Especially common are oil refineries, which produce a variety of useful products. Typical processes are distillation to separate the crude oil into various boiling-point fractions or cuts, alkylation to combine small hydrocarbon molecules into larger molecules, catalytic reforming to change the structure of medium-size hydrocarbon molecules, fluid catalytic cracking to break apart large hydrocarbon molecules, hydrocracking to break apart even larger molecules, and other processes to convert the crude-oil residue to coke and lighter fractions.
Chemists use analytical separation methods such as chromatography, to determine compositions of complex mixtures quantitatively. preparative separation techniques to recover and purify chemicals. Chemical engineers are more concerned with the manufacture of chemicals using economical, large-scale separation methods, which may differ considerably from laboratory techniques. For example, in a laboratory, chemists separate and analyze light-hydrocarbon mixtures by gas-liquid chromatography, while in a large manufacturing plant a chemical engineer uses distillation to separate the same hydrocarbon mixtures. This book presents the principles of large-scale component separation operations, with emphasis on methods applied by chemical engineers to produce useful chemical products economically. Included are treatments of classical separation methods, such as Distillation Absorption Liquid-liquid extraction As well as newer methods: adsorption and membrane separation Separation operation for all three phases (gas, liquid, and solid) are covered. Knowing the principles of separation operations, chemical engineers can successfully develop, design, and operate industrial processes.