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Unformatted text preview: Chapter 4 : Synthesis of Reactor Flow Sheets and Selection of Reactor Process Conditions Department of Chemical and Biological Engineering The University of British Columbia 1 Introduction Chemical reactors are at the heart of any chemical process. Chemical reactors come in all shapes and sizes Left: Outdoor multistory reactors in commodity chemical process. Middle: In brewery, the fermentors are human size. Right: Mammalian cells are tiny chemical reactors a few μ m in diameter. Reactors provide the conditions that allow chemical reactions to occur, so raw material are converted into products. 2 Introduction (2) In fact, one might say that the ability to deal with reacting systems is one of the distinct skills that di erentiates chemical engineers from other kinds of engineers. The challenge in engineering chemical reactions are many: raw materials and reaction pathways must be selected reactor shape, size, and operating conditions must be chosen reactor ow sheet must be designed chemistry, equipment, and ow sheet must be combined in a way that is safe, economical, and environmentally sound. 3 Industrially Important Chemical Reactions It is impossible to list all the myriad chemical reactions to convert the raw materials we have to products we want. We list some of the categories that are important industrially. Most of these chemical reactions are also important in the natural worlds for the functioning of everything from single-cell organisms to ecosystems. Oxidation Probably the rst chemical reaction to be exploited by humans. Complete oxidation of C- and H-containing materials provides heat for cooking and warmth. Oxidizing agents range from H 2 , H 2 O 2 to KNO 3 . Partial oxidation allows introduction of oxygen groups into hydrocarbons derived from fossil fuels and is an important step in production of many industrial chemicals, including alcohols and organic acids. 4 Industrially Important Chemical Reactions (2) Hydrogenation and Dehydrogenation Of utmost importance in organic and inorganic chemistry. Crude oil is hydrogenated to remove S and N, thus avoiding release of acid gases upon burning of gasoline or other fuels. Hydrogenation of nitrogen produces ammonia used in agriculture. Either H 2 or stronger reducing agents, like NaBH 4 , are commonly used reactant in hydrogenation processes. Dehydrogenation of fats to oils changes the material from solid to liquid, as C-C single bonds are converted to double bonds. Polymerization One or two types of small molecules with reactive ends are linked together to form chains that can reach MW → 10 6 . Rubber, cellulose, starch, proteins, and DNA are all natural polymers. Nylon, polyester, Te on, polycarbonate, and other synthetic polymers are ubiquitous in modern life....
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- Winter '08
- Reaction, Chemical reaction, material balance equations