Emulsion Studies Associated with Bitumen Recovery from Canadian Oil Sands: Part I

摘要

Bitumen is produced from Athabasca oil sands at a daily rate of more 400,000 Bbl/day using open pit mining. Bitumen is recovered from the oil sand grains in a water-based process. Both water-in-oil and oil-in-water emulsions are formed during the bitumen recovery process. Of significance, is the formation of very stable water-in-bitumen/solvent emulsions. The water drops have an average diameter of about 2-5 microns. Initial studies showed that complete removal of the water-soluble surface-active species from bitumen by water extraction resulted in increased emulsion stability. Fine solids and water-insoluble surface-active asphaltenes were found to be the key stabilizing agents for water-in-bitumen/toluene emulsions. Separation of the toluene-diluted bitumen continuous phase from the emulsion by centrifuging at different g-values was conducted. Emulsion stability tests for the separated toluene-diluted bitumen and element analysis of the precipitated asphaltenes indicated that the asphaltenes in the separated organic continuous phase are different from those associated with the water droplet interface. The asphaltenes associated with the interface had a lower H/C ratio and a higher O/C ratio. Tests using a micropipette technique showed that the water/diluted bitumen interface characteristics are much influenced by the solvent to bitumen ratio. Drop shape recovery tests showed that a water drop recovers from a stretched shape to a spherical shape in about one second when the solvent/bitumen ratio is 100/1. However, its recovery time is an order of magnitude less for a solvent/bitumen ratio of 10/1. From an industrial prospective, solvent type, solvent to bitumen ratio and de- emulsifier addition were found to play major roles in water removal.