Single-pass filtration

FIGURE 18.18 LPC for 0.5-pm (Planargard CS05) and 1.0-pm (Planargard CMPl) nominal rating (1-1/2" length) depth media filters in single-pass filtration test. 

FIGURE 18.20 LPC for 1.0-gm (Planargard CMPI) nominal rating depth media (1-1/ 2" length) filters in single-pass filtration experiments, (a) silica-1, (b) ceria-1, and (c) alumina-1 slurry. 

Plate pr esses. Sometimes called sheet filters, these are assemblies of plates, sheets of filter media, and sometimes screens or frames. Thev are essentially modified filter presses with practically no cakeholding capacity. A press may consist of many plates or of a single filter sheet between two plates, the plates may be rectangular or circular, and the sheets may lie in a horizontal or vertical plane. The operation is similar to that of a filter press, and the flow rates are about the same as for disk filters. The operating pressure usually does not exceed 138 kPa (20 psig). The presses are used most frequently for low-viscosity liqmds, but an ordinaiy filter press with thin frames is commonly used as a clarifier for 100-Pa s (1000-P) rayon-spinning solution. Here the filtration pressure may be 6900 kPa (1000 psig). 

Field tests, on a single filter element of commercial design, have been successfully conducted at typical operating condition. Measured Ciltratioo efficiency is con iarable with bag house filters, for filtration velocities up to 14 cm/s. The applied filtration velocities are extremely high compared with bag filters which normally operates in the area of 1.0 to 2.5 cm s. The pressure drop over the sand fitter shows that even if filtration speed is increased dramatically, it is possible to work within the same field as bag filters, i.e. from 900 to approximately 2200 Pa. 

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