Filtration data test procedures

Testing procedures were established for each vendor selected for on-site demonstration of filtration equipment. These procedures were based on the need for testing data to properly complete the final equipment specifications and purchase justification. 

Various small scale test units and procedures are available to determine slurry characteristics and suitability for a particular application. Buchner funnel, and vacuum leaf test units can be purchased or rented fi om vendors to perform in-house tests, or one can have tests conducted at the vendor s facility. Pilot testing on the actual equipment would be the optimum with a rental unit in the plant. In either case, slurry integrity must be maintained to ensure accurate filtration data. 

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. ... 

Vacuum and pressure laboratory filtration assemblies are shown in Figure 11.7. Mild agitation with air sometimes may be preferable to the mechanical stirrer shown, but it is important that any agglomerates of particles be kept merely in suspension and not broken up. The test record sheet of Figure 11.8 shows the kind of data that normally are of interest. Besides measurements of filtrate and cake amounts as functions of time and pressure, it is desirable to test washing rates and efficiencies and rates of moisture removal with air blowing. Typical data of these kinds are shown in Figure 11.3. Detailed laboratory procedures are explained by Bosley (1977) and Dahlstrom and Silverblatt (1977). Test and scale-up procedures for all kinds of SLS equipment are treated in the book edited by Purchas (1977). 

Foaming Special procedures are used in many industries to measure this property. A convenient method is to shake a measured quantity of liquid under arbitrarily established conditions and measure the height of foam and also the length of time the foam persists. The test is applied to the original liquid and to the carbon-treated filtrates. As it may be difficult to determine the relation of height and persistency of foam to concentration, the data are best plotted as in Figure 14 2. 

The Data Analysis module of FDS facilitates the interactive analysis of constant pressure and constant flow filtration, jar sedimentation and piston press (expression) tests the procedures are computer software implementations of the analysis techniques described in Chapter 4. Data obtained at the laboratory, pilot and even full scale can be analysed in a consistent manner... 

Vertical line cursors are used to identify a linear or transition region on the Characteristic Plot and these are initially positioned by FDS. However, the user has facility to interact with the software and move the cursors as appropriate in order to overcome their potential misplacement due to data scatter. In this way the analysis can be amended as many times as required and optimised. During the analysis of a jar sedimentation test a third, horizontal line cursor is used to specify the final height of sediment, which is particularly useful when a test is not continued to equilibrium. In the case of a piston press analysis, and in accordance with the recommend procedure described in Section 5.5, additional representations of test data are shown for the filtration and consolidation phases to check the choice of transition between the two. For example, in Figure 5.12 the correct transition has been identified on the Characteristic Plot such that the resultant tjIVj vs. Vf plot is linear throughout and the consolidation ratio U vs. (consolidation time, exhibits an initial linear portion. In Figure 5.13 the transition point has been deliberately chosen too far to the left on the Characteristic Plot such that the vs. plot exhibits an incorrect S shape. 

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