INDUSTRIAL CHEMICAL REACTORS

Horak and Pasek, De.sign of Industrial Chemical Reactors from Laboratoiy Data, Heyden, 1978. 

TABLE 23-1 Residence Times and/or Space Velocities in Industrial Chemical Reactors ... 

Horak, J. and Pasek, J., Design of Industrial Chemical Reactors from Eaboratory Data, Heyden Son Ltd., 1978. 

The models presented correctly predict blend time and reaction product distribution. The reaction model correctly predicts the effects of scale, impeller speed, and feed location. This shows that such models can provide valuable tools for designing chemical reactors. Process problems may be avoided by using CFM early in the design stage. When designing an industrial chemical reactor it is recommended that the values of the model constants are determined on a laboratory scale. The reaction model constants can then be used to optimize the product conversion on the production scale varying agitator speed and feed position. 

The design of an industrial chemical reactor must satisfy the following requirements ... 

This polytetrafluoroethylene coating is being applied to a gasket that will be used in an industrial chemical reactor. Because of its strong bonds, the polymer is very resistant to chemical attack. Only a tiny fragment of the polymer molecule is shown here the actual polymer consists of thousands of —CF2CF2— units in long chains. 

The state of the art of the mathematical, numerical, statistical, optimizing, and processing methods available nowadays for solving problems in chemical kinetics allows the mechanistic approach to reach its full potential in two directions (i) to contribute to the elucidation of the mechanisms of complex reactions and to the determination of the kinetic parameters of elementary processes (ii) to permit the design of, calculations on, the optimization of and control of an industrial chemical reactor from the results of a previous mechanistic study. This calls for two requirements (i) to improve the numerical and processing methods (some directions of research have been indicated above) (ii) to improve the data bases of fundamental kinetic parameters as well as our understanding of general reaction mechanisms. 

An industrial chemical reactor is a complex device in which heat transfer, mass transfer, diffusion, and friction may occur along with chemical reaction, and it must be safe and controllable. In large vessels, questions of mixing of reactants, flow distribution, residence time distribution, and efficient utilization of the surface of porous catalysts also arise. A particular process can be dominated by one of these factors or by several of them for example, a reactor may on occasion be predominantly a heat exchanger or a mass-transfer device. A successful commercial unit is an economic balance of all these factors. 

To make the matters worse, chemical reactions steepen scalar gradients and often, larger values of k ax need to be used. Since (kmax x max x k ax) values must be stored in the computer memory for each field for each time step, application of DNS to reactive flow processes is limited to moderate Reynolds numbers and Schmidt numbers near unity. The Damkohler number (ratio of charaeteristic time scales of small-scale mixing and chemical reaction, see Chapter 2) is generally limited to values less than 30 to 50. Even if huge computational resources are available, the DNS approach is difficult to apply to the realistic geometry of industrial chemical reactors. 

Principles of chemical reactor analysis and design new tools for industrial chemical reactor operations / Uzi Mann, M.D. Morris, advisory editor—2nd ed. p. cm. 

Some real unit operations can find direct correspondence with the blocks used in flowsheeting, as flashes, distillation columns, heat exchangers, etc. However, the equivalence could be difficult for many others. This is typical the case of the industrial chemical reactors and a number of separators. In some cases, a simple model may be satisfactory for a quite complex unit from mechanical point of view. Consequently, the modelling of real units can follow one of the following possibilities ... 

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