A Method for Improving the Quality of Bituminous Froth From Water Extraction of Oil Sands

Bituminous froths produced from the water extraction of oil sands contain significant quantities of sand and water which must be removed prior to upgrading the bitumen to synthetic crude oil. This paper presents a summary of the study of a simple twostep process for removing most of the solid and water contaminants from the bituminous froth. Low-quality froths containing 10–30 percent bitumen at temperatures of 40–70°C were improved in quality to 50–60 percent bitumen by heating the raw froth to ~ 90°C and settling the product in a gravity settler. The gravity settling vessel incorporated unique features for the introduction of the hot froth into the vessel. Two types of froth heaters were tested: a column heater containing a structured grid packing which used live steam injection, and a shell and tube heat exchanger. Heat transfer data were obtained for both types of heaters in the range of froth flow conditions available in the pilot plant. There was no apparent difference between the two heating modes in terms of the froth quality improvement, but the direct contact heater had the benefit of deaerating the froth. Evaluation of the separation efficiency showed that the gravity separation vessel design performed very well, and hence was incorporated into a commercial froth cleaning plant design. The bitumen separation efficiency was the best for froths containing about 20 percent bitumen. There was no apparent improvement in the froth quality for froths containing over 65 percent bitumen.