Belt Press Filter is a ccontinuous compression equipment usually operated at a lower pressure than batch equipment. However, the cake received some shearing action as it passes through the pressure zone and the allows shear thinning cakes to be dewatered.
In a belt press filter, the cake is trapped between two cloths and must be firm enough that it does not extrude from the edges. The belt filter can be used with flocculated slurry. Slurry conditioning is the addition of chemicals to promote flocculation of particles to form a thickened sludge and to promote dewatering. Flocculation is improved with optimum polymer dosage, polymer dilution and mixing.
A belt filter consists of three zones. The slurry is fed onto a single cloth belt where dewatering occurs by gravity. The cake then enters the linear compression zone where a second cloth belt comes onto the top of the cake.
These two belt then pass over rollers which form a gradually tapering section. The buildup in pressure is relatively low during this stage. The two belt then pass around a series of offset rollers. The diameter of these rollers may gradually decrease so that pressure builds up.
The cloths move at the same overall speed but some shearing occurs because the cloth on the outside must travel further than that on the inside. The cake in the rollers compression zone follows a serpentine path around rollers, this section is called S belt press.