Filtration test data, example

CP cell data are easily obtained and may be of value in a qualitative sense as an indication of the sensitivity of resistivity to pressure, but apparently are not of acceptable engineering accuracy for the design of filtration equipment. The deduction of resistivities from filtration tests is illustrated in Example 11.1. 

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. ... 

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. 

Determine the time necessary for the filtration of 50 m of the same slurry as in example 9.1 in a plate-and-frame filter press with 25 frames of dimensions 1 x 1 x 0.035 m. Use the test data for cake resistance and medium resistance (the same cloth is used) obtained in example 9.1. The pump characteristic is shown in Figure 9.12. 

An example of a solid-liquid phase separation - often referred to as a mechanical separation - is filtration. Filters are also used in gas-sohd separation. Filtration may be used to recover liquid or sohd or both. Also, it can be used in waste-treatment processes. Walas [6] describes many solid-hquid separators, but we will only consider the rotary-drum filter. Reliable sizing of rotary-drum filters requires bench and pilot-scale testing with the slurry. Nevertheless, a model of the filtering process will show some of the physical factors that influence filtration and will give a preliminary estimate of the filter size in those cases where data are available. 

The model was tested for many cases of electrically enhanced and non-enhanced filtration. The location of each particle in each dendrite was recorded. The resulting data can only be usefully discussed if presented in graphical form. Plots of two views of each simulation were generated. Because each simulation must be considered as a single event of a random process, it was necessary to generate many plots for the same simulation conditions. The dendrite patterns included in this report were chosen as typical examples of various sets of simulation conditions. 

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