PROCESS DESIGN ASPECTS

In addition to flow, thermal, and bed arrangements, an important design consideration is the amount of catalyst required (W), and its possible distribution over two or more stages. This is a measure of the size of the reactor. The depth (L) and diameter (D) of each stage must also be determined. In addition to the usual tools provided by kinetics, and material and energy balances, we must take into account matters peculiar to individual particles, collections of particles, and fluid-particle interactions, as well as any matters peculiar to the nature of the reaction, such as reversibility. Process design aspects of catalytic reactors are described by Lywood (1996). 

In this chapter, we consider process design aspects of reactors for multiphase reactions in which each phase is a fluid. These include gas-liquid and liquid-liquid reactions, although we focus primarily on the former. We draw on the results in Section 9.2, which treats the kinetics of gas-liquid reactions based on the two-film model. More detailed descriptions are given in the books by Danckwerts (1970), by Kastanek et al. (1993), and by Froment and Bischoff (1990, Chapter 14). 

The types of reactors used for fluid-fluid reactions may be divided into two main types (1) tower or column reactors, and (2) tank reactors. We consider some general features of these in this section and in Section 24.3. In Sections 24.4 and 24.5, we treat some process design aspects more quantitatively. 

Cross-flow filtration as a processing alternative for separation and concentration of soluble or dissolved components competes with traditional equipment such as dead end cartridge filtration, pre-coat filtration and centrifugation. The specific merits and weaknesses of each of these filtration alternatives are summarized in Table 3. In addition to the ability to handle wide variations in processing conditions, other considerations may need to be addressed for economical viability of cross-flow filtration. These are briefly discussed below. A more detailed discussion on process design aspects, capital and operating cost considerations is presented in Sec. 6.7. 

Alper,E. "Process design aspects of gas absorbers". (Proceedings of NATO ASI on "Mass transfer with chemical reaction in multiphase systems,. Turkey, 1981)... 

Process Design Aspects and Comparison of Different Bioreactors... 

In short, the traditional design approach adopts a sequential design approach. In contrast, the process integration methodology for process design takes a different approach in that process design aspects in the inner part of the onion diagram are... 

Continuous Saponification Systems. A relatively recent innovation in the production of soap, these systems have led to improved manufacturing efficiency and considerably shorter processing times. There are a number of commercial systems available even though these systems are different in design aspects or specific operations, they all saponify fats and oils to finished soap using the same general process (Fig. 3). 

The major water desalination processes that ate currendy in use or in advanced research stages are described herein. Information on detailed modeling can be found in the Hterature cited. The major texts on water desalination written since the 1980s are those by Spiegler and Laird (47), Khan (48), which contains many practical design aspects, Lior (49) on the measurements and control aspects, Heitman (40) on pretreatment and chemistry aspects, and Spiegler and El-Sayed (50), an overview primer. Extensive data sources are provided in References 39 and 51. 

At the heart of a leaching plant design at any level—conceptual, pre-liminaiy, firm engineering, or whatever—is unit-operations and process design of the extraction unit or hne. The major aspects that are particular for the leaching operation are the selection of process and operating conditions and the sizing of the extrac tion equipment. 

Many of the inherently safer design aspects discussed here appear in Guidelines for Safe Automation of Chemical Processes (CCPS, 1993b). It makes excellent reading for greater depth and treatment of inherently safer/process control concepts. 

The application of the science of human factors to eliminating error in all aspects of process design, management, operation, and maintenance is the focus of this work. Human error has been a major cause of almost all of the catastrophic accidents that have occurred in the chemical process industries (CPI). If one adopts the broad view of human error as being the result of a mismatch between human capabilities and process demands, then clearly management s role is critical in the following areas ... 

While this process implies an ordered, structured process, it should be noted that the various stages overlap and it is frequently necessary to return to an earlier step in the process to modify or clarify information or decisions made in an earlier phase. The influence of the human factors aspects on design needs to be similarly integrated into the process design procedure. The particular human factors elements to be addressed at each phase are discussed below. These phases can be directly related to the human factors engineering and ergonomics (HFE/E) design approach described in Section 2.2. 

Since 1977, Reza Sadeghbeigi has been involved in various aspects of cat cracking at major and independent oil companies focusing on technical services, troubleshooting, process design, and project management—including major FCC revamps. 

There are some aspects of process design in which decisions are based primarily on past experience rather than on quantitative performance models. Problems of this type include the selection of constraction materials, the selection of appropriate models for evaluating the physical properties of homogeneous and heterogeneous mixtures of components, and the selection of safety systems. Advances in expert systems technology and information management will have a profound impact on expressing the solutions to these problems. 

Let us now give a brief synopsis of the themes advanced by each of the ten chapters. The five chapters of Volume 21 (Part 1) advance paradigms which are related to product and process design, while the five chapters of Volume 22 (Part II) focus on aspects of process operations. 

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