Categories of separation processes

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... 

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,... 

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. 

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... 

Analysis of separation processes can be placed into two fundamental categories equilibrium-based and rate-based processes. These separation categories are designated using thermodynamic equilibrium relationships between phases and the rate of transfer of a species from one phase into another, respectively. The choice of which analysis to apply is governed by which is the limiting step. If mass transfer is rapid, such that equilibrium is quickly approached, then the separation is equilibrium limited. On the other hand, if mass transfer is slow, such that equilibrium is not quickly approached, the separation is mass transfer limited. In some separations, the choice of analysis depends upon the type of process equipment used. 

Process synthesis heuristics fall into several categories. Many of these were proposed origiually for multicomponent distillation but have since been applied 10 other types of separation. Some heuristics have bean verified through calculation and experimentation while others are described best as common senes, in any case, they serve as effective guidelines in the selection and sequencing of separation processes. 

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. 

Prediction of reverse osmosis performance is usefiil to the design of RO processes. Simulation of RO processes can be separated iato two categories. The first is the predictioa of membrane module performance. The second is the simulation of a network of RO processes, ie, flow sheet simulations, which can be used to determine the optimum placement of RO modules to obtain the overaH process objective. 

This section describes the major industrial processes within the petroleum refining industry, ineluding the materials and equipment used, and the processes employed. The section is necessary for an understanding of the interrelationships between the industrial processes, the types of air emissions, and control and pollution prevention approaehes. Deseriptions of eommonly used production processes, assoeiated raw materials, by-produets produeed are first deseribed. Petroleum refining is the physieal, thermal, and chemical separation of erude oil into its major distillation fraetions, which are then further proeessed through a series of separation and eonversion steps into finished petroleum produets. The primary products of the industry fall into three major categories ... 

For convenience, the processes identified in Figure 2.1 can be separated into two distinct categories toxicokinetics and toxicodynamics. Toxicokinetics covers uptake, distribution, metabolism, and excretion processes that determine how much of the toxic form of the chemical (parent compound or active metabolite) will reach the site of action. Toxicodynamics is concerned with the interaction with the sites of action, leading to the expression of toxic effects. The interplay of the processes of toxicokinetics and toxicodynamics determines toxicity. The more the toxic form of the chemical that reaches the site of action, and the greater the sensitivity of the site of action to the chemical, the more toxic it will be. In the following text, toxicokinetics and toxicodynamics will be dealt with separately. 

An earlier section which dealt with mineral separation included flotation among the category of concentration separation processes. The introduction of flotation was one of the major milestones in the history of mineral processing. There exist variations (natural or artificially created) in the surface properties of mineral particles, and the technique of flotation is based on the utilization of these differences. The actual specific gravity of the mineral particle plays little or no part in the separation. 

Commercial-scale application of solvents coming under the category of neutral reagents is largely found as applied to the nuclear industry materials, as in example, for the separation and refining of uranium, plutonium, thorium, zirconium, and niobium. A process flowsheet for extracting niobium and tantalum from various resources is shown in Figure 5.23. It will... 

Process Category Fiber Separation Method Fiber Quality Examples % of Total 1998 U.S. Wood Pulp Production... 

---