## Filter Presses And Other Batch Pressure Filters

With a set of operating data on a continuous rotary filter, environmental engineers can calculate the specific resistance a using Equation 7.47(6), in which AP is the differential pressure on a continuous filter.

Based on time in minutes, the following equation applies:

where:

Equation 7.47(7) gives the continuous dry solids rate (assuming complete retention of solids by the filter cloth).

For nearly incompressible filter cakes, the following equation calculates the approximate required area of a batch filter to replace a continuous filter for the same slurry at the same average rate. The filtrate liquid per unit area per batch is as follows:

/2APbTft anW

= KaAP^TJ1

For constant-pressure, batch filtration, Vfb is related to Tfb. If the following conditions exist,

Tcb = total batch cycle time, min

= filter cake form time + discharge time then the average batch filtrate rate is as follows:

then the average batch filtrate rate is as follows:

The following equation calculates the relative rates on batch and continuous filters for the same slurry at the same temperature:

Zc average rate, continuous filter

APC/2(Bn)C

For quick-cleaning batch filters Tdb ^ Tfb, then Tcb — Tf and Equation 7.47(13) simplifies to the following equations:

APc APb

APc APb

0 0