Solid/liquid separation operations

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. 

This chapter summarizes the solid-liquid separation operations commonly used for the pretreatment of drying operations. We focus on the practical aspects of cake filtration, centrifngal filtration, and mechanical expression. The choice of equipment depends on the objective of the separation, the properties of the slurry, and the scale of prodnction. The details of solid-liquid separation theories are omitted. The reader is referred to the references for further information. 

Treatment of a suspension with the necessary chemical will produce a ffster settling system with a more bulky and more permeable sediment, but the final liquid content of the shidge or filter cake may well be significantly hi er than if a nontreated suspension had been settled. The benefits therefore tend to be found in flie enhanced settling rate and increased permeabiUty, and sometimes the sediment is of such bulk as to prove troublesome and expensive in disposal Other solid-liquid separation operations such as dissolved air flotation and centrifiigation have different requirements that must be met by the pretreatment system. 

Flocculants are also used as retention and drainage aids in paper production. This is again a solid-liquid separation operation, albeit using very sophisticated and extremely high-speed filtration. Without the use of these reagents it would not be possible to produce paper at the rate that it is today. 

In many industrial processes, solid-liquid separation operations are combined with drying operations. Figure 50.1 illustrates a process combining drum filters, a rotary kiln, a centrifuge, a disk filter, a spray dryer, and a conveyor dryer. In this combined operation, the solid-liquid separation enhances the quality of the product and decreases the thermal energy of... 

This chapter summarizes the solid liquid separation operations commonly used for the pretreatment of drying operations. We focus on the practical aspects of cake filtration, centrifugal filtration, and mechanical... 

In the context of this paper floes are aggregates of particles in suspension. These aggregates, which may be induced by the application of specific treatments or occur natur ly, are commonly used to enhance the performance of solid liquid separation operations such as filtration and sedimentation when the size of the primary particles is so small that the operation would not be practical on them in an untreated state. This is likely to occur when the primary particle size is <10pm. In many systems of processing interest the primary particles may have a size in the sub-micron range, eg pigments. 

Crystals suspended in liquors emerging from crystallizers are normally passed to solid-liquid separation devices such as gravity settlers or thickeners that may subsequently feed filters to remove yet more liquid prior to drying. Here the transport processes of particle motion and the flow of fluids through porous media are important in determining equipment size, the operation of which may be intensified by application of a centrifugal force. 

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... 

Adsorption in expanded or fluidised beds is now widely adopted for the direct recovery of protein products from particulate feedstocks. As an integrative protein recovery operation it circumvents process bottlenecks encountered with the solid liquid separation required upstream of fixed bed adsorption, while achieving considerable concentration and primary... 

The separation of solids from liquids forms an important part of almost all front-end and back-end operations in hydrometallurgy. This is due to several reasons, including removal of the gangue or unleached fraction from the leached liquor the need for clarified liquors for ion exchange, solvent extraction, precipitation or other appropriate processing and the post-precipitation or post-crystallization recovery of valuable solids. Solid-liquid separation is influenced by many factors such as the concentration of the suspended solids the particle size distribution the composition the strength and clarity of the leach liquor and the methods of precipitation used. Some important points of the common methods of solid-liquid separation have been dealt with in Chapter 2. 

Hydrocyclones are used for solid-liquid separations as well as for solids classification, and liquid-liquid separation. It is a centrifugal device with a stationary wall, the centrifugal force being generated by the liquid motion. The operating principle is basically the same as that... 

Equipment Selection Criteria and Guidelines A number of factors should be considered to determine when to select which type ofvapor/gas/solid-liquid separator (blowdown drum or cyclone separator) to handle a multiphase stream from a relief device, and which final control or destruction equipment (emergency flare, emergency scrubber, or quench pool/catch tank) should be selected. These factors include the plot plan space available, the operating limitations of each type, and the physicochemical properties of the stream. 

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