Effects of Clay Wettability and Process Variables on Separation of Diluted Bitumen Emulsion

Initial processing of bitumen froth obtained using a water-based extraction process from Athabasca oil sands yields stable water-in-bitumen emulsions. When the bitumen is diluted with naphtha to reduce its viscosity and density, almost complete separation can be obtained with a demulsifier in the absence of clay solids. However, a rag layer persists between the oil and free water layers when clay solids are present. Effects of the naphtha/bitumen (N/B) ratio, demulsifier selection, and silicate dosage on the rag layer formation and product quality have been studied. Emulsions with a N/B ratio of 0.7 are more stable than those with a N/B ratio of 4.0. This can be partially attributed to the difference in viscosity and density affecting the sedimentation velocity. The residual water and solid contents in the oil layer decrease with the addition of silicate. This behavior is attributed to the effect of silicate on clay wettability. Clay solids have toluene-soluble organic contents, which vary as follows: in the oil layer > in the rag layer > in the bottom layer. This result indicates that the solids are the most water-wet in the bottom (water) layer and the most oil-wet in the oil layer. In the same layer, samples with a N/B ratio of 0.7 have a higher toluene-soluble organic content in solids than those with a N/B ratio of 4.0. At 80 degrees C with a N/B ratio of 4.0, emulsion adding 200 ppm of demulsifier PR6 and 4 x 10(-4) M sodium in-silicate had 0.3-1.5% water and 0.9% solids in the oil layer, with the water content decreasing with an increasing height above the rag layer.