REACTOR CONCEPT OVERVIEW

In this paper the advantages of using a fully adaptive method for the simulation are shown by the example of catalytic air purification with a fixed-bed reactor with periodic flow reversal (Matros-reactor). First, a short overview over the reactor concept, the mathematical model and its main properties is given. The last section deals with the numerical solution of the problem and with the discussion of the effects shown. 

Research activities in past decades have produced new reactor concepts. For example, hybrid (multifunctional) reactors combining reaction and heat or mass transfer are an interesting new option. Progress has also been achieved with monolithic reactors, which are already used commercially in emission control systems. An overview of these developments is given by Moulijn, Makkee, and Van Diepen (2004). Details are given by Westerterp (1992) and Cybyulski and MouUjn (1997). 

Figure 23.3 Schematic overview of reactor concepts for the OCM reaction.

The present description gives an overview of a modified option of the RBEC reactor concept named RBEC-M [XXIII-8, XXIII-9]. The RBEC-M is characterized by the following major innovations aimed at the enhancement of safety parameters and economic efficiency ... 

The ELFR is a design resulting from the update and modification of the earlier ELSY reactor concept. Fig. 6.2 provides an overview sketch of the primary system configuration of the ELFR reactor. 

Section 2 presents the assumptions and requirements upon which the INEL concept was developed. Section 3 contains an overview of the reactor concept. Section 4 lists the conclusions and recommendations. Most of the technical details and discussions are contained in the appendices. The first task was to examine plutonium destruction rates and isotopics for different neutron spectra, as discussed in Appendix A. This study lead to the adoption of a thermal reactor concept instead of reactors with fast or epithermal neutron spectra. The second task was to study the addition of seed materials for selfprotection from materials diversion. Appendix B illustrates that fission products provide the best. self-protection, and seed materials are not needed for the INEL concept. Various fuel types were investigated and are described in Appendix C. The core neutronics studies presented in Appendix D and thermal-hydraulics studies pre.sented in Appendix E were performed concurrently. An evaluation of potential offsite radiation doses... 

The first chapter provides an overview of the Super LWR and Super FR reactor studies. It includes elements of design and analysis that are further described in each chapter. The reader will also be interested in what ways the new reactor concepts have been developed and how the analyses have been improved. 

One feature that distinguishes the education of the chemical engineer from that of other engineers is an exposure to the basic concepts of chemical reaction kinetics and chemical reactor design. This textbook provides a judicious introductory level overview of these subjects. Emphasis is placed on the aspects of chemical kinetics and material and energy balances that form the foundation for the practice of reactor design. 

Introduction of a permselective membrane to a reactor zone opens up opportunities for resolving the above important reaction performance issues. An overview of this concept will be given next followed by some examples portraying the benefits of a membrane reactor. 

Turbulence is the most complicated kind of fluid motion. There have been several different attempts to understand turbulence and different approaches taken to develop predictive models for turbulent flows. In this chapter, a brief description of some of the concepts relevant to understand turbulence, and a brief overview of different modeling approaches to simulating turbulent flow processes is given. Turbulence models based on time-averaged Navier-Stokes equations, which are the most relevant for chemical reactor engineers, at least for the foreseeable future, are then discussed in detail. The scope of discussion is restricted to single-phase turbulent flows (of Newtonian fluids) without chemical reactions. Modeling of turbulent multiphase flows and turbulent reactive flows are discussed in Chapters 4 and 5 respectively. 

The present chapter is not meant to be exhaustive. Rather, an attempt has been made to introduce the reader to the major concepts and tools used by catalytic reaction engineers. In order to give the reader a feel of the applicability of these concepts and tools. Section 8.2 gives an overview of the most important industrial reactors. Section 8.3 is a review of ideal reactor types. Emphasis is placed on the way mathematical model equations are constructed for each reactor category. Basically, this boils down to the application of the conservation laws of mass, energy and possibly momentum. Section 8.4 presents an analysis of the effect of the finite rate at which reaction species and/or heat are supplied to or removed from the locus of reaction, i.e. the catalytic site. Finally, the material developed in Sections 8.3 and 8.4 is applied to the design of laboratory reactors and the analysis of rate data in Section 8.5. 

The objective of this section is to provide a brief overview of selected chemistries and processes that are based upon various tubular reactor designs to illustrate more practical aspects. As the partial oxidation process is a key manufacturing technology that utilizes various tubular reactor designs, most of the emphasis will be placed here. The extension of the same concepts to other chemistries, such as hydrogenation reactions, is based upon similar principles. 

Detailed descriptions of the chemical reactor flow patterns are given in chaps 8, 10, 7 and 11. Meanwhile, a preliminary overview of the pertinent reactor flow characteristics is given to determine which modeling concepts are available describing the behavior of the relevant flows. 

Chemical reaction engineering (CRE) is the branch of engineering that encompasses the selection, design, and operation of chemical reactors. Because of the diversity of chemical reactor apphcations, the wide spectnim of operating conditions, and the multitude of factors that affect reactor operations, CRE encompasses many diverse concepts, principles, and methods that cannot be covered adequately in a single volume. This chapter provides a brief overview of the phenomena encountered in the operation of chemical reactors and of the concepts and methods used to describe them. 

Membrane-based reactive separation (otherwise also known as membrane reactor) processes, which constitute the subject matter of this book, are a special class of the broader field of membrane-based separation processes. In this introduction we will first provide a general and recent overview on membranes and membrane-based separation processes. The goal is to familiarize those of our readers, who are novice in the membrane field, with some of the basic concepts and definitions. A more complete description on this topic, including various aspects of membrane synthesis can be obtained from a number of comprehensive books and reviews that have already been published in this area [1.1, 1.2, 1.3,... 

M.P. Rohde, D. Unruh, G. Schauh, Membrane application in Fischer—Tropsch synthesis reactors — overview of concepts, in International Conference on Gas—Fuel 05, Elsevier, Amsterdam, 2005. 

Due to the availability of the mentioned overviews it is not the goal of this chapter to consider the whole field of membrane reactors. Rather, the discussion below will be focused on presenting simplified and more detailed mathematical models capable of describing the performance of membrane reactors. Although there are several studies available for analyzing the combination of reaction and membrane separation (e.g. Salomon et al., 2000 Struis and Stucki, 2001 Wielandet al., 2002 Patil etal., 2005 Rohde etal., 2005) there is a need to analyze in more detail specific features of membrane reactors. The focus of this chapter will be the development and application of simplified and also more detailed mathematical models for packed-bed membrane reactors in which certain reactants are dosed over the reactor wall using nonselective membranes. This type of membrane reactor is sometimes also-called a distributor (Dalmon, 1997 Julbe et al, 2001). Despite this restricted focus of the work, most of the concepts considered should be applicable also in the analysis of other types of membrane reactors. 

Rohde, M.P., Unruh, D. and Schaub, G., 2005. Membrane Application in Fischer-Tropsch Synthesis Reactors - Overview of Concepts. Catalysis Today, 106(1-4) 143-148. 

Our approach in this chapter will begin with an overview in Section 21.1 of the common physical and mathematical aspects that are important to the study of criticalities, and then follow this in Sections 21.2 and 21.3 with the particular concepts, analytical approaches, tools, and data that are used in the disciplines of nuclear reactor analysis and nuclear criticality safety analysis, respectively. 

The application of permeable composite monolith membranes for the FT synthesis has been tested [122]. An overview of concepts associated with this reactor type has been presented (Figure 12.25) [123]. Novel uses of this concept have been advanced, and some experimental results have demonstrated the ability to operate at high CO conversion with metal FT catalysts by removal of the water produced during the synthesis [ 124] and the encapsulation of an FT catalyst by a zeolite membrane layer to effect upgrading reactions in the FT reactor [125]. The potential of this technique merits further studies to evaluate the ability to scale to a commercial level. 

Rohde MP, Unruh D, Schaub G. Membrane application in Fischer-Tropsch synthesis reactors—overview of concepts. Catal. Today 2005 106 143-148. 

The use of miniaturized reactors with characteristic dimensions below about 1 mm, so-called microreactors, is also a currently interesting development. An overview of the basic principles of microreactors is given by Emig and Klemm (2005). Details are found in Hessel, Hardt, and Loewe (2004). Subsequently, short summaries of these new concepts based on the cited literature are given. 

After introducing the concepts of macro- and micro-mixing, the importance of flow / mixing patterns in reactors is discussed. Next, an overview of the methods for describing complex flow patterns is given and the relation between the different methods is explained. Focusing on statistically stationary flow, each method is then presented and discussed in more detail in the remaining sections of this chapter. 

Because the flow pattern inside gasification reactors is of prime importance to understand gasifier behavior, this section is dedicated to give an engineering-oriented and pragmatic overview how to approach the complex field of CFD utilization for coal gasification. On the example of internal circulating fluidized bed (INCI) concept development, explained in detail in Chapter 9, test calculations should be accomplished to understand the basic relationships of the system. 

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