Liquid-solid separation utilizing pressure rolls covered with elastomeric layers

An improved apparatus for expressing the liquid phase from a wet mixture including at least one endless filter belt adapted to receive the wet mixture, a plurality of pressure rolls, opposed roll means for forming together with the pressure rolls a series of nips that are spaced apart in the direction of travel of the belt, means for circulating the belt through said nips, and means for biasing said roll means and the pressure rolls against each other so that the liquid phase is expressed from the mixture as the mixture is carried on the belt successively through said nips, wherein the improvement comprises:

• at least two of the pressure rolls being covered with elastomeric layers of substantial deformability, including the upstream one of the plurality of pressure rolls that initially acts on the wet mixture, first means for applying a biasing pressure against the upstream pressure roll at a predetermined level that is preselected to subject the mixture to a relatively gradual rate of increase in pressure as the wet mixture is carried into the first nip, and second means for applying a biasing pressure on the other of said at least two pressure rolls at a relatively higher pressure to subject the mixture to a comparatively steeper rate of increase in pressure to thereby express further liquid phase from mixture already partially deliquified in said first nip.

Apparatus for expressing residual liquid from moist solids comprising a frame, a primary roll journalled for rotation on said frame, at least two press rolls mounted for rotation parallel to said primary roll and spaced successively thereabout, means for urging each of said press rolls independently against said primary roll to define successive compression zones, drive means for effecting rotation of said rolls, a first endless flexible fabric filter medium belt maintained under tension and trained about said primary roll between it and said press rolls to pass through said compression zones;

• the surfaces of said primary roll and at least one of said press rolls being deformable and of substantially equal deformability and the surface of one other of said press rolls is of deformability that is significantly different from that of said surface of said primary roll.