Solid/liquid separation system design

Crystallization Process Systems brings together essential aspects of the concepts, information and techniques for the design, operation and scale up of particulate crystallization processes as integrated crystal formation and solid-liquid separation systems. The focus of the book, however, is on crystallization only dealing with related unit operations as far as is necessary. It is therefore... 

Thus, methods are now becoming available such that process systems can be designed to manufacture crystal products of desired chemical and physical properties and characteristics under optimal conditions. In this chapter, the essential features of methods for the analysis of particulate crystal formation and subsequent solid-liquid separation operations discussed in Chapters 3 and 4 will be recapitulated. The interaction between crystallization and downstream processing will be illustrated by practical examples and problems highlighted. Procedures for industrial crystallization process analysis, synthesis and optimization will then be considered and aspects of process simulation, control and sustainable manufacture reviewed. 

Separation system design offers an example. At the first level of decision making, we could classify the species and the phases involved to decide the type of likely separation methods that might be used. King [11] lists 54 different separation methods. Some are for gas-gas separation, others for gas-liquid, still others for gas-liquid-solid, and so forth. An approach is to make high-level decisions on which type (gas-gas, gas-liquid, etc.) of separation is needed for each of the separation steps required [9]. Then, based on these decisions, lower-level decisions select exactly which method to use to separate species having the same classification. 

The treatment of wastes and water supplies primarily involves the removal of particulates and, therefore, is accomplished by solid-liquid separation processes. However, present design procedures for such treatment systems do not utilize or even recognize the importance of the physical properties of particulates in solid-liquid separation. In fact, until very recently, eflForts at measuring particle size in wastewaters and raw water supplies have been very limited. Among early eflForts, the investigations at Rutgers University (3,4,5,6) are especially notable. Very recent renewed interests in particle size determinations have used Coulter, Hiac, and Zeiss Videomat particle counters (7,8,9). 

This chapter is written with three objectives in mind. First, the importance of the size and concentration of the particles to be treated in determining the eflFectiveness of some solid-liquid separation processes is evaluated. Second, past theories are used to examine how particle sizes and concentrations are altered by these treatments. Third, interrelationships among the individual unit processes that comprise a complete treatment system are investigated to provide a base for an integral treatment plant design. These aims are undertaken using a typical water treatment system as employed in practice to remove turbidity from surface water supplies. Before addressing these objectives, it is useful to review some mathematical expressions of particle size distributions, and to identify some important properties of these functions. 

The design of an expert system for use in solid/liquid separation involves considerations such as generality and completeness of both the available data and the ultimate software, programming language features and database structures and the control mechanisms that shape and restrict the... 

Wakeman R.J. and Tarleton E.S., 1991a. Solid/liquid separation equipment simulation and design - an expert systems approach, Filtr. Sep., 28, 268-274. 

Particle characterization, i.e. the description of the primary properties of particles in a particulate system, underlies all work in particle technology. Primary particle properties such as the particle size distribution, particle shape, density, surface properties and others, together with the primary properties of the liquid (viscosity and density) and also with the concentration and the state of dispersion, govern the other, secondary properties such as the settling velocities of the particles, the permeability of a bed or the specific resistance of a filter cake. Knowledge of these properties is vital in the design and operation of equipment for solid-liquid separation. 

Expert systems in solid-liquid separation have now gone out of fashion somewhat and the pre-selection of equipment now tends to be built into much larger design software. In any case, computerized advice, although helpful to complete beginners as a first approach, is no substitute for experience and in-depth knowledge of the subject. 

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