Vacuum assisted slaker classifier

A slaker apparatus employed in the Kraft or pulp process having a slaking unit and a classifier compartment for producing a caustic solution having a pH over 12.5, the slaker unit comprising a tank and impeller type mixer having means for introducing lime, water and green liquor, the reaction of these constituents establishing a caustic solution of NaOH to a desired liquid level in said tank, the classifier compartment being connected to the slaker by submerged slurry passage ports to achieve a common liquid level with the caustic solution in said tank and having an inclined deck or ramp which extends from a bottom location in said compartment to a beach region above the liquid level in said compartment, a grit conveyor means extending along said ramp to convey settled particulate solids associated with caustic solution having a pH over 12.5 up said ramp to said beach region, a screen provided in the surface of said beach region of said ramp, wash means positioned above said screen to direct a spray of wash liquid upon the particulate solids as they are conveyed across said screen, said spray of wash liquid directed upon said particulate solids to displace caustic solution associated therewith, a vacuum means below said screen for drawing wash liquid through said settled particulate solids and said screen, and conduit means at the upper end of said beach region for receiving washed particulate solids associated with residual liquid having a pH less than 12.5 for disposal.