Reactor selection engineering factors

Chemical reactors are the most important features of a chemical process. A reactor is a piece of equipment in which the feedstock is converted to the desired product. Various factors are considered in selecting chemical reactors for specific tasks. In addition to economic costs, the chemical engineer is required to choose the right reactor that will give the highest yields and purity, minimize pollution, and maximize profit. Generally, reactors are chosen that will meet the requirements imposed by the reaction mechanisms, rate expressions, and the required production capacity. Other pertinent parameters that must be determined to choose the correct type of reactor are reaction heat, reaction rate constant, heat transfer coefficient, and reactor size. Reaction conditions must also be determined including temperature of the heat transfer medium, temperature of the inlet reaction mixture, inlet composition, and instantaneous temperature of the reaction mixture. 

Chemical reaction engineering (CRE) is the branch of engineering that encompasses the selection, design, and operation of chemical reactors. Because of the diversity of chemical reactor apphcations, the wide spectnim of operating conditions, and the multitude of factors that affect reactor operations, CRE encompasses many diverse concepts, principles, and methods that cannot be covered adequately in a single volume. This chapter provides a brief overview of the phenomena encountered in the operation of chemical reactors and of the concepts and methods used to describe them. 

The operation of a chemical reactor is affected by a multitude of diverse factors. In order to select, design, and operate a chemical reactor, it is necessary to identify the phenomena involved, to understand how they affect the reactor operation, and to express these effects mathematically. This section provides a brief review of the phenomena encountered in chemical reactor operations as weU as the fundamental and engineering concepts that are used to describe them. Figure 1.4 shows schematically how various fundamental and engineering concepts are combined in formulating the reactor design equations. 

Given their complexity and practical importance, it should be no surprise that different approaches for dealing with turbulent reacting flows have developed over the last 50 years. On the one hand, the chemical-reaction-engineering (CRE) approach came from the application of chemical kinetics to the study of chemical reactor design. In this approach, the details of the fluid flow are of interest only in as much as they affect the product yield and selectivity of the reactor. In many cases, this effect is of secondary importance, and thus in the CRE approach greater attention has been paid to other factors that directly affect the chemistry. On the other hand, the fluid-mechanical (FM) approach developed as a natural extension of the statistical description of turbulent flows. In this approach, the emphasis has been primarily on how the fluid flow affects the rate of chemical reactions. In particular, this approach has been widely employed in the study of combustion (Rosner 1986 Peters 2000 Poinsot and Veynante 2001 Veynante and Vervisch 2002). 

The subjects of catalytic science include catalysis (cataljAic phenomena and principle) catalyst (composition, structure, performance and manufacturing method and principle) catalytic reaction kinetics (chemical kinetics and mechanism) as well as cataljAic reaction engineering (apparent kinetics inclucing transport process and reaction process and reactor design) etc. The main tasks of catalytic science are to elucidate the nature of catalytic active sites, the function of catalyst and reaction mechanism to explore the main factors influencing activity, selectivity and stabihty of catalyst to accumulate acknowledge for the exploitation and development of chemical catalysis and to open up its relatively new disciplines — bionic catalysis, photo catalysis, electro catalysis and photoelectric catalysis — to indicate... 

In the preceeding chapters the emphasis was on the rates of chemical processes, and particularly on the influence of various physical factors on process rates. These rates are not only important in relation to the dimensions of the equipment, but they also determine the selectivity of the chemical process. Aiming for higher selectivities is desirable for three reasons to minimize raw materials consumption, to improve product quality and to reduce chances of pollution of the environment. There are therefore important similarities between requirements for the quality of products of the chemical industry and for the quality of waste streams. In addition to the quantitative methods that were demonstrated above, a qualitative engineering approach is also valuable. This is not always reconcilable with quantitative economic calculations. It is necessary to consider the quality of chemical operations in general, and of chemical reactors in particular. This is also a part of chemical reactor developement. 

The role of the chemical reactor is crucial for the industrial conversion of raw materials into products and numerous factors must be considered when selecting an appropriate and efficient chemical reactor. Chemical Reaction Engineering and Reactor Technology defines the qualitative aspects that affect the selection of an industrial chemical reactor and couples various reactor models to case-specific kinetic expressions for chemical processes. 

Lamarsh, J. R. 1972. Introduction to Nuclear Reactor Theory. Reading, MA Addison Wesley Publishing. This publication is based on a one-year course in nuclear reactor theory at Cornell and New York universities. The book gives readers a fundamental understanding of the principles regarding the operation of a nuclear reactor. References and exercises are included at end of each chapter. Appendices cover conversion factors, selected constants, isotopes of importance in nuclear engineering, and properties of selected molecules. 

There ate a number of factors to be considered prior to selecting a reactor. In general, they can be grouped into three categories engineering, economic, and environmental. 

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