Separation solid-fluid systems

In Chapter 7, the focus is on separation processes, in which the criteria for the selection of separation processes and the choices of equipment are reviewed before systematic methods of process synthesis are covered. The latter begin with sequences of ordinary distillation columns, then general vapor-liquid separation processes, and subsequently sequences that include azeotropic distillation columns. Also covered are considerations in selecting separation systems for gas mixtures and for solid-fluid systems. 

Be able to determine feasible separation systems for gas mixtures and solid-fluid systems. 

It is fitting to end this review of efficiency definitions with a rather speculative but theoretically very basic definition. The thermodynamic efficiency may be defined as the basic energy of mixing of the solids in a fluid, in relation to the work done in a separator to unmix the suspension. The former is as yet impossible to establish because little is known quantitatively about the thermodynamics of solid-fluid systems and the thermodynamic efficiency... 

Other three phase combinations that are of some practical interest are solid/ liquid/liquid systems, solid/solid/fluid systems and liquid/liquid/gas systems, but these are considered too specific to warrant a separate treatment here. 

A cyclone separator is an economical device for removing particulate solids from a fluid system. The induced centrifugal force (see Figure 7-6) is tangentially imparted on the wall of the cyclone cylinder. This force, with the density difference between the fluid and solid, increases the relative settling velocity. 

The separation (A) of the hyperfine lines in the ESR spectra of metal-amine, and metal-ether solutions represents a direct measure of the average s-electron (spin) density of the unpaired electron at the particular metal nucleus (12,156). When this splitting is compared to that of the free (gas-phase) atom, we obtain a measure of the "percent atomic character of the paramagnetic species. The percent atomic character in all these fluid systems increases markedly with temperature, and under certain circumstances the paramagnetic species almost takes on "atomic characteristics (43, 53, 160). Figure 9 shows the experimental data for fluid solutions of K, Rb, and Cs in various amines and ethers, and also for frozen solutions (solid data points) of these metals in HMPA (17). The fluid solution spectra have coupling con-... 

Expression is the separation of a liquid from a two-phase solid-liquid system by compression, due to movanent of the retaining wall rather than the pumping of the solid-liquid system into a fixed chamber as in filtration. In filtration, the original mixture is sufficiently fluid to be pumpable in expression, the material may appear either entirely sani-solid or slurry. Based on an expression theory [6,7], the time for expression is also proportional to the square of cake thickness. 

In industry, separations effected by porous solid materials (adsorbents, membranes, ion exchange resins, special kinds of solid matrices) are seldom applied in comparison to separations carried out in systems with fluid phases. The reason may be a poorer state of the art than in fluid systems. Furthermore, the handling of flitid systems is much easier than the handling of systems with solid phases. On the other... 

Adsorption is the loading of solid surfaces with substances present in a surrounding fluid phase or, in other words, it is a surface effect between a solid and a fluid phase. Sometimes molecules of the fluid phase are not only fixed on the surface but can additionally enter the bulk of the nonporous solid phase according to a volume effect. This is called occlusion or absorption. When it is not known which of these two effects is dominant the term sorption is used. Adsorption means the loading of one or several components (adsorptives) on a solid material (adsorbent). The reverse process, e.g., the separation of adsorptives from the surface is called desorption. It is a question of mass transfer in a two-phase system solid/fluid ... 

No theory of freezing exists. That is, there is no partition function that encompasses both the solid and fluid phases. However, separate theories of solids and fluids can be developed and their solid-fluid coexistence examined. To that extent theories of melting or freezing exist. Since freezing can occur in the hard-sphere system, no critical point is expected for freezing. This transition is expected to be first order at all temperatures, as illustrated in Fig. 1. 

There are two major types of VOCs recovery refrigerated condensation (Stone 1997) and adsorption, followed by refrigeration (Hussey and Gupta 1997, Kent 1999). Although there are several types of condensation systems the most common adopted is a reverse Rankine cycle where a closed-cycle heat pump with a separate working fluid is used to condense VOCs. Adsorption is a process whereby the VOCs in the air stream are captured physically on the surface of a solid such as carbon. Steam or inert gas is... 

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