Performance of reactors

In this section, some practices in batch and continuous reactors are presented in order to determine the performance in terms of conversion, selectivity, and yield. These examples were conducted in partnership with some Brazilian industries. 

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In this chapter, we focus on the characteristics of the ideal-flow models themselves, without regard to the type of process equipment in which they occur, whether a chemical reactor, a heat exchanger, a packed tower, or some other type. In the following five chapters, we consider the design and performance of reactors in which ideal flow occurs. In addition, in this chapter, we introduce the segregated-flow model for a reactor as one application of the flow characteristics developed. 

A rapid estimation of the performance of reactors with various values of DjuL for both first- and second-order reactions can be made using the charts given by Levenspiel [2]. 

Fig. 28. Comparison of performance of reactors for the plug flow and dispersed plug flow models. Reaction is of first order, aA- products, and constant density, occurring in a closed vessel (L14, L15).

Fixed-bed catalytic reactors and reactive distillation columns are widely used in many industrial processes. Recently, structured packing (e.g., monoliths, katapak, mella-pak etc.) has been suggested for various chemical processes [1-4,14].One of the major challenges in the design and operation of reactors with structured packing is the prevention of liquid flow maldistribution, which could cause portions of the bed to be incompletely wetted. Such maldistribution, when it occurs, causes severe under-performance of reactors or catalytic distillation columns. It also can lead to hot spot formation, reactor runaway in exothermic reactions, decreased selectivity to desired products, in addition to the general underutilization of the catalyst bed. 

Material, energy, and momentum balances are essential to fully describe the performance of reactors, and often simplifying assumptions and phenomenological assumptions are needed especially for energy and momentum terms, as indicated in greater detail in Sec. 19... 

AR292 Physics and fuel performance of reactor-based plutonium disposition, OECD Proceedings, Workshop proceedings, Paris, 28 30 September 1998. 

Different approaches have been used to model mass transfer performance of reactors. They comprise two main parts the micromodel, describing the mass transfer between two phases, and the macromodel, describing the mixing pattern within the individual phase. The micromodels assume two types of interfacial behavior stagnant films or dynamic absorption in small elements at the contact surface. 

The performance of reactor systems, sodium systems, control rod drive mechanisms and other safety related systems and auxiliary system were generally satisfactory. The primary and secondary sodium purity was maintained below the plugging temperature of 105 C. The four sodium pumps and Aeir drives are operating well and have logged 83,293 h, 70,615 h, 88,878 h 69,201 h. 

Business and process drivers are required to set targets to be met by the plant design. The business drivers identified at the start of the methodology, which are the economic reasons why it is desirable to intensify the process, should be reviewed to keep a clear idea of the overall aims of the project. Process drivers are those characteristics of, in this particular example, the chemical reaction scheme that determine the required operating conditions within, and performance of, reactor equipment to allow the process to run at its most efficient rate. A process driver example is the rate of heat release from a reaction determining the heat transfer capability required of the equipment. 

As discussed in See. 1, nonuniform flow is an inherent characteristie of gas solid fluidization systems. A typical radial solids distribution in a riser without any inserts is not uniform the solids eoneentration is low in the center and high in the wall region. In many circumstances, internals are aimed at redistributing gas and solids flow, in an effort to form a more uniform flow strueture to improve interphase eontact efficiency so as to increase the overall performance of reactors. 

The results presented above illustrate that significant improvement can be achieved in the performance of reactors with complex reactions. Furthermore, this performance could be explained by postulating that the kinetics of adsorption/desorpt-ion played an important role in the system dynamics in general and in this improvement, in particular. Nevertheless, there are other models which could also be consistent with this behaviour. 

It will be clear from the above that the space-velocity (equation (2.85)) and the space-time yield (equations (2.105) and (2.111)) are dependent upon the degree of conversion and upon the initial (batch reactor) or inlet (plug flow reactor) concentrations. In order to compare the performance of reactors involving different or values, it is therefore useful to define normalized s and... 

Develop the ability to analyze the performance of reactors in which single and multiple reactions are occurring. 

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