Importance of bitumen viscosity in the hot-water processing of domestic tar sands

The separation efficiency of the hot water digestion-flotation technique used for bitumen recovery from various domestic tar sands was evaluated. Bitumen viscosity was found to be the most important tar sand property in determining the success of the bitumen separation. Bitumen viscosity of the tar sand was controlled by changes in digestion temperature and/or changes in diluent (kerosene) addition. Complete and uniform dilution of the bitumen phase was achieved by providing a sufficient presoaking, or penetration time, for a given tar sand type. For all the tar sand samples tested, an excellent correlation was obtained between the coefficient of separation and the bitumen viscosity. To achieve a satisfactory coefficient of separation, it was found that the bitumen viscosity must be reduced below 1.5 Pa-s (16 P) at the temperature of digestion. This was the case regardless of the tar sand type, grade, or origin.