Filtration data filter cake solids fraction

Example 4.1 For the constant pressure filtration data shown in Table 4.1 calculate the specific cake resistance, filter medium resistance, cake solids volume fraction and other characterising parameters. The test has been performed in accordance with the procedure described in Section 4.1.1. Table 4.1 Experimental data for the constant pressure filtration analysed in Example 4.1. ... 

While valuable information on settling, filtration and cake post-treatments such as washing and gas deliquoring can be obtained from individual tests, in order to subsequently simulate filter performance it is usually necessary to evaluate so-called scale-up coefficients from sequences of tests. These empirical coefficients principally relate to cake formation (compressibility) and compression dehquoring (consolidation), as it is currently impossible to predict either from a knowledge of fundamental solid and liquid properties. Many filter cakes are compressible to some extent, and increases in filtering pressure lead to less porous and more resistant cakes. For these systems data are needed which relate the specific resistance, oc, a measure of cake structure such as solids volume fraction, and where appropriate the modified consolidation coefficient, Q, to variations in the plied pressure difference Ap. It is conventional practice to assume that Q and Q are solely functions of Ap. 

J. The data in Table 30.7 were taken in a constant-pressure filtration of a slurry of CaC03 in H O. The filter was a 6-in. filter press with an area of 1.0 ft. The mass fraction of solids in the feed to the press was 0.139. Calculate the values of a. and cake thickness for each of the experiments. The temperature is 70°F,... 

The principal objective of an expression test is to determine the compression deliquoring characteristics of a cake. However, the nature of the test allows both filtration and compression characteristics to be determined when the starting mixture is a suspension (i.e. where the solids are not networked or they are interacting to a significant extent). Cake formation rate, specific resistance and solids volume fraction data can be determined for the filtration phase while analysis of a subsequent consolidation phase allows the calculation of parameters such as consolidation coefficient, consolidation index and ultimate solids concentration in the cake. Repeated use of the expression test over a range of constant pressures allows the evaluation of scale-up coefficients for filter sizing and simulation as described in Section 4.7. 

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