Solvent removal from cyclohexane‐extracted oil sands gangue

Abstract

AbstractSolvent extraction of bitumen from the Alberta oil sands has the potential to overcome the shortcomings of the current aqueous extraction process by reducing fresh water demand and eliminating tailings ponds. Bitumen is recovered as a solution, leaving behind the solids (or gangue) with a residual solvent and water from the original ore. Removing the solvent from the gangue is a crucial step that involves evaporation of volatile material (cyclohexane) from a porous matrix in the presence of a less volatile immiscible phase (water). In this study, we examined the effects of relative humidity, temperature, and the addition of water during cyclohexane extraction on the extent of cyclohexane removal from the extraction gangue. The drying curves showed two constant‐rate periods, with the initial period mainly removing cyclohexane, and the second mainly removing water. The initial drying rate of gangue in an environmental chamber was 2.7 times faster than drying in a fume hood due to the stronger convective currents in the chamber produced by its fan. The initial drying rate was independent of the relative humidity, which was in the range of 30–90 %, but the residual cyclohexane content in the gangue increased at high relative humidity. The addition of water to oil sands prior to cyclohexane extraction increased the residual cyclohexane in the gangue, likely by forming a barrier to efficient evaporation.