Solid-liquid separation cake formation

The solid-liquid separation of shinies containing particles below 10 pm is difficult by conventional filtration techniques. A conventional approach would be to use a slurry thickener in which the formation of a filter cake is restricted and the product is discharged continuously as concentrated slurry. Such filters use filter cloths as the filtration medium and are limited to concentrating particles above 5 xm in size. Dead end membrane microfiltration, in which the particle-containing fluid is pumped directly through a polymeric membrane, is used for the industrial clarification and sterilisation of liquids. Such process allows the removal of particles down to 0.1 xm or less, but is only suitable for feeds containing very low concentrations of particles as otherwise the membrane becomes too rapidly clogged.2,4,8... 

The solids-liquid separation of slurries containing particles below 10 xm is difficult by conventional filtration techniques. A conventional approach would be to use a slurry thickener in which the formation of a filter cake is restricted and the product is discharged continuously as a concentrated slurry. Such filters use filter cloths as the filtration medium... 

Crystal morphology (i.e., both form and shape) affects crystal appearance solid-liquid separations such as filtration and centrifugation product-handling characteristics such as dust formation, agglomeration, breakage, and washing and product properties such as bulk density, dissolution kinetics, catalytic activity, dispersability, and caking. 

Rushton, A., Hosseini, M. and Rushton, A., Shear effects in cake formation mechanisms , pp. 149-158. In Proc. Symp. on Solid-Liquid Separation Practice, Yorkshire Branch of the I. Chem. E., Leeds, 27-29 March (1979)... 

In situations where a low concentration of suspended solids needs to be separated from a liquid, then cross-flow filtration can be used. The most common design uses a porous tube. The suspension is passed through the tube at high velocity and is concentrated as the liquid flows through the porous medium. The turbulent flow prevents the formation of a filter cake, and the solids are removed as a more concentrated slurry. 

The filtration operation involves the separation, removal, and eolleetion of a discrete phase of matter existing in suspension. The undissolved solid partieles are separated from the liquid suspension by means of a porous medium (i.e., filter medium). Filtration leads to the formation of a eake containing a relatively low proportion of residual filtrate. Depending upon the meehanism for arrest and accumulation of particles, the filtration operation can generally be classified into three types cake filtration, deep-bed filtration, and membrane filtration (see Fig. 1). 

Filtration is the mechanical separation of solid and liquid phase which allows the removal of insoluble solids or suspended material from a liquid by passing it through a porous medium only permeable for the liquid phase. In small- and medium-sized plants, this is mostly achieved by means of the formation of a filter cake from the seed particles between porous filter materials within a pressure gradient. The filter cake improves the result of the filtration. Sometimes filter aids can be used to increase the effect of the filter materials. These are inert cellulose materials which improve the formation of a filter cake for the filtration process. Filtration in small- and medinm-sized plants is carried out by the use of chamber filter presses or vertical pressure plate filters, which enable a much higher throughput in comparison to sedimentation. The last step of the purification process in small- and medium-sized plants is passing the oil through a fine-pored protection filter to ensure a defined clarity of the oil. 

It is not suited to the clarification of liquids, its main purpose being the separation of quite concentrated suspensions, which permit the rapid formation of a cake of separated solids. 

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