Abstract: In the extraction of bitumen oils from oil sands, the raw material is first slurried with a stream of hot water under conditions promoting the release of the bitumen oils without disintegration of clay in the raw material; the water to raw material is at least 1:1 by weight. The slurry is separated into an oil-rich component, a solids component, and a middlings component containing essentially water and fines with only minor proportions of oil and solids. The middlings component, after removal of the contained fines and the solids is recycled as a part of the slurrying water.

Abstract: A rotary digester comprises a shell having means at one end for entry of material to be digested and, at the opposite end, a liquids outlet surrounded by a solids outlets. The solids outlet has a screw which assists in preventing egress of unwanted liquid with the solids.