Post-treatment processes

The term post-treatment refers to processes vdiich are used after the principal solid-liquid separation has been achieved. The final step in the latter operation is usually some type of cake filtration which will leave a cake that may be fully saturated with liquid or partially drained and it is extremely unlikely that the solids are in an acceptable condition for any subsequent operation such as thermal drying. Thus the post treatment processes are washing and deliquoring which are concerned req ectively with removing the soluble solids from the liquid remaining in the cake and then purging the major proportion of the liquid fi om the cake pores. 

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. 

Hence if the cake vohme is V. and m the mass of solute in the cake  

The amount dm removed in a small element of time dr is also given by wash rate 

If F is the vohmiBtiic rate of wash liquid per unit area and is the cake area then dm = c Ffdr 

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Vol. 1 Polymer Engineering Vol. 2 Filtration Post-Treatment Processes Vol. 3 Multicomponent Diffusion Vol. 4 Transport in Porous Catalysts... 

R. J. Wakeman, Filtration Post-Treatment Processes, Elsevier Publishing Co., Amsterdam, 1975. 

To ensure the successful design of a reverse osmosis process, several factors should be considered. These considerations encompass the feed solution, the membrane module, and the use of other processes in the pre- and post-treatment processes. A thorough knowledge of the feed stream and its components is essential to the prevention of membrane damage and product impurities. Once the feed stream is characterized and the process objective is defined, design can be initiated. 

POST TREATMENT, PROCESS RESIDUAL MATERIAL MANAGEMENT... 

Baking A thermal post-treatment process, does not only induce the development of final bonding, structure, and consistency in bread but produces similar characteristics during the heat curing of any green agglomerate. 

Often, sintering is used as a post-treatment process to provide strength to agglomerates (see Sections 7.3 and 8.3) or modify the porosity. Depending on how the sintering process is controlled, the agglomerate shrinks and densifies (up to almost 100 % density or 0 % porosity) or porosity is maintained and, sometimes, even increased (see Section 5.3.2). 

Sintering is also used as a post-treatment process to obtain final and permanent strength and structure of green bodies which were formed by agglomeration (see Sections 7.3 and 8.3). 

Larger feed particle size High initial strength Dry processing No or little binder Hot processing No post treatment Processing of elastic materials Automatic operation Easy clean-out Quick turn-over... 

Fig. 6.11-15 is a diagram of these routes indicating the applicable raw materials and their preparations, the web forming and bonding, the post-treatments (processing of non-wovens) and the type of products [B.107]. 

Catalysts used in industrial processes, whether made from the active substance directly or deposited on carriers, are often porous cylindrical pellets produced by medium pressure extrusion (Fig. 5-10bl-b6, Chapter 5). While almost all methods of size enlargement by agglomeration can be used to produce porous bodies from solid powders and post-treatment processes can yield strong pieces with a high accessible internal porosity [B.23, B.78, B.97] that fulfill the previously discussed requirements, pelleting offers a number of advantages. 

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