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Abstract

A method and apparatuses for expressing the liquid phase from a wet mixture such as a clay-like mixture includes a primary roll (12, 104) with a plurality of smaller pressure rolls (13, 112-118) biased against its surface at circumferentially spaced intervals and at increasing pressures. The primary roll and at least the upstream one (112) of the pressure rolls have a thick outer covering of a substantially deformable elastomeric material. A pair of opposed filter belts (22, 23 or 142, 144) are trained about the primary roll and means are provided to feed the wet mixture between the belts to carry the mixture successively through the nips between the primary roll and the pressure rolls. The mixture is initially subjected in the first nip to a relatively gradual rate of increase in pressure and in subsequent nips is subjected to progressively steeper rates of increase in pressure adapted to the different flow behavior of the mixture caused by the increasing solids content of the mixture. In one embodiment all of the pressure rolls (112-118) are covered with equally thick elastomeric layers of equal hardness, and the first roll (112) is biased with a predetermined relatively low pressure to initially subject the wet mixture to said relatively gradual increase in pressure. In an alternative embodiment intended for wetter mixtures, the rolls (112'-118') are covered with equally thick layers which increase in hardness in the direction of travel of the belts. Specially fabricated belts and edge seals are disclosed.

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First Claim