Effect of Caustic Type on Bitumen Extraction from Canadian Oil Sands

Abstract

The role of different types of caustics in bitumen extraction from Canadian oil sands is investigated by analyzing their effect on subprocesses involved in bitumen extraction. Both sodium hydroxide and ammonium hydroxide were shown to improve bitumen liberation, which is favorable for bitumen recovery, but increased induction time of bitumen–bubble attachment, which is harmful for bitumen recovery. Although a similar performance was observed at pH of ∼8.5, at pH 11.3, the use of ammonium hydroxide led to a shorter induction time of bitumen–bubble attachment and, hence, better bitumen recovery than the use of sodium hydroxide to achieve the same slurry pH. The better performance of ammonium hydroxide is attributed to a more hydrophobic surface and a less negative zeta potential of bitumen in the process water because of the release of less amount of natural surfactants in ammonium hydroxide solutions than in sodium hydroxide solutions of the same solution pH. Overall, ammonium hydroxide was found to be a suitable replacement for sodium hydroxide. Although this study was mainly concerned with mining–extraction operations, the major findings derived from this study could be applied readily to in situ thermal bitumen production operations, because ammonia can be delivered with steam to oil sands formations.