Chemical reaction engineering case studies

A further characteristic of chemical reaction engineering is its facility in refining concepts. It is a derived characteristic, stemming from the mathematical component of the subject, but it has been typical of its development since the distinction between stability and sensitivity was first drawn (34). There have been lapses, alas, as in the case of an expository paper (52) which, to judge by the demand for offprints, proved quite useful, but which rated a very low Watkins number (53), for its title was "On the stability criteria of chemical reaction engineering" while its burden was as much the multiplicity criteria as the stability conditions. But there has been a steady incorporation of precisely defined concepts as for example in the burgeoning study of... 

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 job of designing power generation equipment usually falls to mechanical engineers, but the analysis of combustion reactions and reactors and the abatement and control of environmental pollution caused by combustion products like CO, CO2, and SO2 are problems with which chemical engineers are heavily involved. In Chapter 14, for example, we present a case study involving the generation of electricity from the combustion of coal and removal of SO2 (a pollutant) from combustion products. 

Studies under categories ii and iii provide more poignant examples of the power of Car-Parrinello methods. Because of the magnitude of the literature on applications of Car-Parrinello simulations, 1 have chosen to focus on a few case studies to iUustrate the potential of simulations under these categories for problems of interest to chemical engineers. The areas that 1 have chosen are (A) gas-phase processes (B) processes in bulk materials (C) properties of liquids, solvation, and reactions in liquids (D) heterogeneous reactions and processes on surfaces (E) phase transitions and (F) processes in biological systems. 

Figure 1.9 shows different kinds of flowsheets which mark the start and the end of the part of the overall design process which is covered by the case study. At the beginning, the chemical process is described by an abstract flowsheet which decomposes the process into basic steps without considering the equipment to be used (upper part of Fig. 1.9). The process consists of three steps reaction of caprolactam and water, separation of input substances which are fed back into the reaction, and compounding, which manipulates the polymer produced in the reaction step such that the end product meets the requirements. The lower part of Fig. 1.9 shows a process flowsheet which consists of chemical devices and therefore describes the chemical plant to be built - still at a fairly high level of abstraction. The process flowsheet serves as input for detail engineering, which is beyond the scope of the case study.

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