Process design applications generally

Rotary positive-displacement compressors should be operated as base loaded units. They are especially sensitive to the repeated start-stop operation required by load-following applications. Generally, rotary positive-displacement compressors are designed to unload about every six to eight hours. This unload cycle is needed to dissipate the heat generated by the compression process. If the unload frequency is too great, these compressors have a high probability of failure. 

Membranes are semipermeable barriers that permit the separation of two compartments of different composition or even condition, with the transport of components from one compartment to another being controlled by the membrane barrier. Ideally, this barrier is designed to let pass selectively only certain target compounds, while retaining all others—hence the denotation semipermeable . Membrane separations are particularly suitable for food applications because (1) they do not require any extraction aids such as solvents, which avoids secondary contamination and, hence, the necessity for subsequent purification (2) transfer of components from one matrix to another is possible without direct contact and the risk of cross-contamination (3) membrane processes can, in general, be operated under smooth conditions and therefore maintaining in principle the properties and quality of delicate foodstuff. 

Ail answers to process design questions cannot be put into a book. Even at this late date in the development of the chemical industry, it is common to hear authorities on most kinds of equipment say that their equipment can be properly fitted to a particular task only on the basis of some direct laboratory and pilot plant work. Nevertheless, much guidance and reassurance are obtainable from general experience and specific examples of successful applications, which this book attempts to provide. Much of the information is supplied in numerous tables and figures, which often deserve careful study quite apart from the text. 

Another important area of chemical engineering applications is in the selection of solvents, co-solvents, or entrainers—generally summarized as solvents—in the early phase of a process design, development, or optimization project. For such tasks, beyond the fixed essential starting materials and products of the process, a large number of compounds has to be considered as potential... 

Particularly strong and complex interactions prevail among reaction and separation systems that are generally not at all or not fully exploited as a result of the application of the available synthesis methods for reactor networks and separation systems in isolation. The lack of generality in the synthesis methods is a tribute to the nonlinear process models required to capture the reaction and separation phenomena as well as to the vast number of feasible process design candidates. These complexities even make it difficult to synthesize the decomposed subsystems, which are typically reactor networks, separation systems, reactor-separator-recycle systems, and reactive separation systems. The development of reliable synthesis tools for these sub-systems is still an active research area. 

General References Fisher, Batch Control Systems Design, Application, and Implementation, ISA, Research Triangle Park, N.C., 1990. Rosenof and Ghosh, Batch Process Automation, Van Nostrand Reinhold, New York, 1987. 

This near constancy of the unit cost of essergy vs. steam temperature and pressure led naturally to Boteler s "Utilization Function" (27), which appears in Requirements 2 and 3 of the following paragraph. In view of these contributions by Smith and Boteler, a description of essergetic functional analysis may now be presented which is expected to be applicable to process design and synthesis in general ... 

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