Methods of Process Intensification

A second method of process intensification for recuperative reactors is to enhance performance by using a reactive coolant or heating medium, since the heat effects associated with reactions are usually much larger than those available with phase changes or simpler heating and cooling procedures. The coupling of an exothermic auxiliary heat source reaction with the desired endothermic reaction, or vice... 

Kardashev GA. Physical Methods of Process Intensification in Chemical Technologies. 

Table 1.2 Methods of Process Intensification for Improved and More Efficient Reactor...

Figure 1.8 Branching of process intensification into engineering methods and corresponding equipment [26],...

Although the scope of this chapter is limited to catalyst nanoencapsulation for the purpose of process intensification, we take a broad view of the definition of nanoencapsulation. The capsule or catalyst, or both, may be on the nanoscale. Additionally, the various methods of nanoencapsulation may be of the order of up to a few microns. 

The use of multiple otherwise incompatible catalysts allows multistep reactions to proceed in one reaction vessel, providing many potential benefits. In this chapter, literature examples of nanoencapsulation for the purpose of process intensification have been discussed comprehensively. Current efforts in the literature are mostly concentrated in the areas of LbL template-based nanoencapsulation and sol-gel immobilization. Other cascade reactions (without the use of nanoencapsulation) that allow the use of incompatible catalysts were also examined and showcased as potential targets for nanoencapsulation approaches. Finally, different methods for nanoencapsulation were investigated, thereby suggesting potential ways forward for cascade reactions that use incompatible catalysts, solvent systems, or simply incompatible reaction conditions. 

Several technological responses to these emerging trends can be gathered under the umbrella of process intensification. This term encompasses a wide range of methods and equipment for performing chemical processing steps more quickly and compactly, thereby increasing the... 

The use of electromagnetic techniques represents the final method for process intensification of heat transfer that will be dealt with here. Developments in the fuel cell sector hold out the promise of cheap electric power based on surplus hydrogen in chemical plants. The liberalization of the energy sector has also cut electricity prices and enhanced the attractiveness of using electricity in connection with chemical reactors. The precise regulation possible with electrical processes and their clean, environmentally friendly nature are further inducements for their application. 

This method has been applied within DSM for 13 of its existing processes from its three main business clusters (polymers and industrial chemicals, life science products, and performance materials). See Figure 4 for the scheme used within DSM that follows this route. The results showed possibilities for reducing the cost of the present processes to 60-90% of the current costs. (This was shown earlier, in Figure 5 of Chapter 1.) This shows that the way of performing process intensification studies described in this chapter can result in very economical results for various types of businesses (from life sciences to bulk chemicals). Two concrete examples are presented in the next section to give a feeling of process intensification. 

One of the most appealing methods for process intensification is the combination of more fimctions in a single unit. Reactive distillation— combining reaction and separation— is a prime example. However, reactive distillation can be applied only for processes in which the temperature window for reaction and separation coincides. In this respect, reactive stripping is more flexible. Another difference between the two is that reactive distillation is limited to countercurrent operation, whereas for reactive stripping both cocurrent and countercurrent operation are possible, because of the low degree of interaction between the two phases in this regime of separation (23). 

PI encompasses not only the development of novel, more compact equipment but also the development of intensified methods of processing, such as the use of alternative energy sources [4]. In addition, one of the objectives of process intensification is to move away from batch processing to small continuous reactors. The better control of the reaction conditions often allows us to improve not only the... 

There are distinct advantages of these solvent-free procedures in instances in which catalytic amounts of reagents or supported agents are used, because they enable reduction or elimination of solvents, thus preventing pollution at source . Although not delineated completely, reaction rate enhancements achieved by use of these methods may be ascribed to nonthermal effects. Rationalization of micro-wave effects and mechanistic considerations are discussed in detail elsewhere in this book [25, 244], There has been an increase in the number of publications [23c, 244, 245] and patents [246-256], and increasing interest in the pharmaceutical industry [257-259], with special emphasis on combinatorial chemistry and even polymerization reactions [260-263], and environmental chemistry [264]. The development of newer microwave systems for solid-state reaction [265], and introduction of the concepts of process intensification [266], may help realization of the full potential of microwave-enhanced chemical syntheses under solvent-free conditions. 

Most of those not active in PI will have encountered applications of process intensification in their domestic environment, rather than in their work. The microwave oven uses electric fields to intensify the energy input to foodstuffs and liquids, to cook and/or raise their temperature. We may find it difficult to find other orders of magnitude intensification processes within our living space , but an examination of consumer electronics and the power devices needed to drive such systems can reveal existing and potential applications of PI. Even the heat pump/chiller, used to maintain comfort conditions, has benefited from the rotating intensification methods invented by Professor Ramshaw. 

The process has been briefly described by Turunen (1997) as an example of process intensification activities. Most of the hydrogen peroxide production is nowadays based on the anthraquinone method. The differences between the technologies include mainly differences in solvents, catalysts and equipment types and details. The process has less than ten main unit operations including two multiphase reactors, liquid-liquid extraction, gas desorption, distillation and filtration. The process conditions do not include high temperatures or pressures. The necessary properties are not readily available from literature because of the large number of components in the process liquid. However, the measurement of the most of the properties is relatively easy because of the mild conditions. The number of components which take part in the main production reactions and separation steps is small. Therefore it was possible to develop reliable models for most of the unit operations and to base the design on these nnodels. However, the side reactions and by-products involve complicated chemistry and... 

Scientifically, the technical and patent literature (Shkatov, 1981 Shtokman, 1998 and Timonin, 2003)of the considerable quantity of the apparatuses using various methods of an intensification of processes of clearing of gases is presented. Air-conditioning of gases, regime intensification and special ways refer to the last (use of effect of condensation, application is superficial-activesubstances, etc.). 

Design criteria and performance expectations are consistent with the principles of process intensification (PI) methods. The application of this PI philosophy to numerous systems has proven its value, on both a technology and economic basis. Some insight into the virtues obtainable can be found in a description of the bottom-up approach to the formation of nanocrystals (Panagiotou and Fisher, 2008). 

In practice, the process regime will often be less transparent than suggested by Table 1.4. As an example, a process may neither be diffusion nor reaction-rate limited, rather some intermediate regime may prevail. In addition, solid heat transfer, entrance flow or axial dispersion effects, which were neglected in the present study, may be superposed. In the analysis presented here only the leading-order effects were taken into account. As a result, the dependence of the characteristic quantities listed in Table 1.5 on the channel diameter will be more complex. For a detailed study of such more complex scenarios, computational fluid dynamics, to be discussed in Section 2.3, offers powerful tools and methods. However, the present analysis serves the purpose to differentiate the potential inherent in decreasing the characteristic dimensions of process equipment and to identify some cornerstones to be considered when attempting process intensification via size reduction. 

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