Categories of Separations

The basic combinations of chemical potential profiles and flow structures are limited in number. The following major categories can be distinguished. 

the overall chemical potential profile p (representing the sum of external field effects and internal molecular interactions) 

Second, the system may or may not employ flow to structure the separation 

Finally, in category F systems, the flow may be aligned in the direction of the ijl gradient (e.g., ultrafiltration) or perpendicular to the x gradient (e.g., chromatography) 

The combination of the fundamental arrangements of chemical potential profiles and flow structure outlined above yields nine possible categories of separations. These are shown in Table 7.1. 

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Gas phase applications of activated carbon fall into the main categories of separation, gas storage, and catalysis. These applications account for about 20% of the total use of activated carbon, with the majority using either granular or pellet type. Table 3 shows the major gas phase applications, again along with 1987 consumption levels. 

We found earlier that a theoretical consideration of displacement and transport exerts a unifying influence on separation science, bringing diverse methods under a common descriptive umbrella. The theory leads in a natural way to the formation of categories of separations which can be considered the beginning of a fundamental classificatory system. Here we generalize the results of transport theory to develop a fundamental basis for classification. While the resulting scheme will not be a complete polythetic classification, it will be based upon some of the most fundamental features of the separation process. These basic features, incorporated in the classification, should correlate well with other properties of separations in the same way that the number of outer-shell electrons is directly related to the diverse properties of the elements of the periodic table. This transport-oriented... 

This category of separations is done on glass fibre asbestos or quartz papers, on thin layers or in columns [80-84]. In any case the support and equipment used must withstand high temperature. All materials must be purified before electrophoresis in order to remove impurities and to ensure better wettability by the melted salt ... 

This category of separations is commonly carried in gel columns that are located between two electrode vessels. The elution chamber is positioned at the lower end of the column. The apparatuses are provided with either a cooling jacket or the column... 

For a given sample little information is required to allow the selection of the most appropriate stationary phase. Selection may easily be made using the mode selection chart in Table 10.1. It can be seen that the mode appropriate to any particular application depends partly upon the molecular weight of the sample and partly its physicochemical character. Essentially there are four main categories of separation, which are briefly outlined below. 

For B, let S be the category of separated maps of noetherian schemes F the subcategory of flat maps, with =, the usual Dq. -valued inverse-image pseudofunctor E C F the subcategory of etale maps, with the same... 

In the latter category of separation aiding the reaction, a reversible reaction is driven to completion, circumventing the thermodynamic equilibrium constraint, by the removal of one of the products by separation from the reaction mixture. Consider the reversible reaction ... 

The LIB separator is a thin microporous membrane made of polyolefin. It is placed between the anode and cathode to prevent contact between them while enabling Li ions to pass through. There are three basic categories of separator based on their production methods, and each displays different morphologies and characteristics which are suitable for different battery applications. Scanning electron micrographs of typical separators produced by each of the three methods are shown in Figure 1.12. 

The following types are to be distinguished within this general category of separators (dust collectors) (see VDI3676)-... 

These three basic categories of separation processes rely on three different types of separation phenomena. These different types of separation phenomena achieve different extents of separation when coupled with particular configurations of bulk flow vs. force pattern. The description of each process/technique generally includes... 

This illustrative framework is preceded by a few chapters that provide the basic tools for achieving this goal. In earlier literature, a broad category of separation techniques is identified as a mechanical separation process. These techniques are invariably restricted to the separation of particles in a fluid or drops in another fluid subjected generally to an external force. In this book, particle separations have been studied along with chemical separations when a particular external force is considered. Therefore the structure of this book is somewhat different. The following section provides a brief introduction to each chapter in the book. 

In mis framework of mree broad categories of separation processes, former separation development/classi-flcation comes about due to me nature of me interaction between me basic separation phenomena in each category and the directions of bulk flow vis-k-vis me direction of force(s) responsible for me basic separation mechanism. Considerable additional separation development is achieved by reflux, recycle, creation of an additional property gradient in an external force field, mode of feed introduction, etc. These aspects have been addressed in me following sections reflux (Sections 2.3.2, 8.1.1, 8.1.4, 10.1.4.2, 10.2.2.1) recycle (Sections 2.2.2, 2.4.1, 7.2.1.1,... 

We will now illustrate these four categories of separation systems in countercurrent flow. An example from system type (1) will be considered first to illustrate some basic separation results achieved in such a countercurrent flow configuration. Then we will consider examples from each of the system types (2), (3) and (4) sequentially. 

Chapter 7 foUows this latter approach of treating individual separation processes under each of the three broad categories of separation processes when the bulk flow of feed-containing phase is perpendicular to the direction of the force. Chapter 8 foUows the same approach when the buik flows of two phases/regions in the separator are perpendicular to the direction(s) of the force(s). Chapter 9 briefly elaborates on cascades, which were already introduced in the countercurrent multistaged flow systems of Chapter 8. Chapter 10 introduces the energy required for a number of separation processes. Chapter 11 illustrates a few common separation sequences in a number of common industries involved in bioseparations, water treatment, chemical and petrochemical separations and hydro-metaUurgy. Conversion factors between various systems of units are provided in an Appendix. 

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