Removal of residual solvent from solvent-extracted unconventional oil ores gangue by gas bubbling

Abstract

Solvent loss in the residual solids has been considered as a major challenge during the solvent extraction processes of unconventional oil ores (oil sands, asphalt rocks, etc.). Herein, we proposed a gas bubbling method to remove and recover the residual solvents from the extracted gangue for the purpose of solvent reuse and environment remediation. Results show that under the optimal conditions, more than 99.6 wt% of solvent (toluene) in the gangue could be removed and 92.3 wt% of solvent could be directly recovered with the condensation-compression combination process. The effects of water chemistry, gas types (CO2 or N2), and mineral types (calcite and quartz) on the removal efficiency have been investigated. The mechanism of solvent removal from residual solids by the gas bubbling process is deduced to contain several sub-processes, including bubble-oil droplet/solid particle colliding and coalescing; solvent droplet spreading on the bubble surface and evaporating into the bubble; droplets coalescing and solvent evaporating to the gas phase. Meanwhile, the kinetic model of the bubbling process is demonstrated, which matches the first order kinetic model. This process would provide insights for other similar situation about oil or solvent removal and recovery from solids.