Solid/liquid separation systems

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... 

Solid-liquid separation systems generally consist of four stages, which are 1) pretreatment to increase particle size 2) solid concentration in thickeners 3) solid separation in filters and centrifuges and 4) posttreatment to remove solubles and reduce liquid content. Fig. 6 shows the relationship among these stages. 

Solid-liquid separation systems generally consist of four stages including pretreatment, solid concentration in thickeners, solid separation in filters or centrifuges, and post-treatment by expression and washing operations. There are different types of SLS equipment served for different functions in relation to the four stages. Product specification, characteristics of solid-liquid suspension, solid settling velocity, rate of cake... 

Tiller, F.M. Li, W. Dangers of lab-plant scaleup for solid/liquid separation systems. Chem. Eng. Commun. 2002, 189, 1655-1677. 

Many solid-liquid separation systems must recover a valuable solid product fi om a su ension which has undesirable constituents such as soluble dissolved solids in its liquid coirponent. Crystallisation and precipitation are obvious exanq>les where a solid phase has to be produced in a pure state firom a contaminant liquor. In such a Nation the cake must be washed with a clean wai fiquor to reduce the contaminants to an acceptable level. 

If one ignores impingement, it would be true to say that all mechanical solid-liquid separation systems are based on one of two principles sedimentation or filtration (see Figure 17.1). 

Keywords RE separation RE resources RE separation history Defects of conventional organic extractants Uniqueness of ionic liquids Solid-liquid separation systems Ionic liquid-based RE functional materials... 

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. 

Crystallization-based separation of multi-component mixtures has widespread application. The technique consists of sequences of heating, cooling, evaporation, dilution, diluent addition and solid-liquid separation. Berry and Ng (1996, 1997), Cisternas and Rudd (1993), Dye and Ng (1995), Ng (1991) and Oyander etal. (1997) proposed various schemes based on the phase diagram. Cisternas (1999) presented an alternate network flow model for synthesizing crystallization-based separations for multi-component systems. The construction... 

In the case of a simple eutectic system shown in Fig. 20-2, a pure solid phase is obtainecf by cooling if the composition of the feed mixture is not at the eutectic composition. If liquid composition is eutectic, then separate crystals of both species will form. In practice it is difficult to attain perfect separation of one component by crystallization of a eutectic mixture. The solid phase will always contain trace amounts of impurity because of incomplete solid-liquid separation, slight solubility of the impurity in the solid phase, or volumetric inclusions. It is difficult to generalize on which of these mechanisms is the major cause of contamination because of analytical difficulties in the ultrahigh-purity range. 

A direct liquefaction technique, the SRC process involves mixing dried and finely pulverized coal with a hydrogen donor solvent, such as tetralin, to form a coal-solvent slurry. The slurry is pumped together with hydrogen into a pressurized, vertical flow reactor. The reactor temperature is about 825°F (440°C) and pressures range from 1,450 to 2,000 psi. A residence time in the reactor of about 30 minutes is required for the carbonaceous material to dissolve into solution. From the reactor, the product passes through a vapor/liquid separation system. The slurry solids remaining in the reactor are then removed and filtered. Various filtration techniques have been developed to remove solids from recoverable oil. 

Sedimentation is also used for other purposes. For example, relative motion of particles and liquid increases the mass-transfer coefficient. This motion is particulady useful in solvent extraction in immiscible liquid—liquid systems (see Extraction, liquid-liquid). An important commercial use of sedimentation is in continuous countercurrent washing, where a series of continuous thickeners is used in a countercurrent mode in conjunction with reslurrying to remove mother liquor or to wash soluble substances from the solids. Most applications of sedimentation are, however, in straight solid—liquid separation. 

The present paper deals with fluidized bed adsorption as an integrative recovery operation. The scope of the contribution is first to describe the concept of the method and the different principles of achieving a combination of solid-liquid separation and chromatography. In the following the main system... 

As a strategy, the synthesis procedure should start with vapor recovery and gas separations, from which some components are sent to liquid separations. For the same reason, the solid-separation system should be placed in the second place. Note that the subsystems of gas and solid separations are largely uncoupled. As a result, the liquid-separation system should is handled the last. 

O Melia, C. R. (1994) From Algae to Aquifers Solid-Liquid Separation in Aquatic Systems. In Aquatic Chemistry, C. P. Huang et al., Eds., American Chemical Society, Washington, DC. 

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