Abstract: In the known operation wherein naphtha-diluted bitumen froth is pumped from a scroll-type centrifugal separator to a disc-type centrifugal separator, an improved pumping system is provided. The system comprises at least two centrifugal pumps in series, each operating preferably at an impellor tip speed less than 4000 feet/minute. The invention is based on the discovery that dilution with naphtha greatly increases the emulsification tendency of the froth components; therefore it is necessary to reduce shearing of this stream to keep the solids and water content of the disc product within a desirable limit. This is achieved by using staged pumping and operating the pumps at a relatively low tip speed.

Abstract: This invention is an improvement on the hot water process for recovering bitumen from tar sand. The aqueous slurry of tar sand is introduced into a first vessel, termed the sand separation cell, containing a body of hot water. The coarse sand settles out and is discharged as tailings. The top product, comprising bitumen, water and fine sand, is transferred to a second vessel, termed the froth formation cell, containing a second body of hot water. In this latter cell, the bitumen forms froth and is recovered, and the fine solids and some water are recycled to the lower end of the sand separation cell. Because the coarse sand has previously been removed in the sand separation cell, good distribution of the feed across the cross-sectional area of the froth formation cell is achieved. This leads to good recoveries and froth quality.