Dilution centrifuging of bitumen froth from the hot water process for tar sand

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.