The previous calculation of K1 and K2 requires a constant controlled pressure. An actual pressure filter, pilot-scale or full-scale, is usually supplied with slurry by a centrifugal b pump at a varying pressure. If the pump suction and filter discharge are both at atmospheric pressure and the pipe and valve losses are negligible, the pump discharge pressure always equals the batch filter differential pressure (AP). The filtrate volume (V), pressure (APb), and time (T) data can then be plotted on companion plots (see Figure 7.47.11).
The true mean APb and true mean flow rate can be obtained by graphic integration. The required filtration area for any total mean flow rate can then be calculated.
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