High molecular weight guar gum assisted settling of fine solids in diluted bitumen: Effect of solvents

Abstract

As water-based extraction technologies for producing bitumen from oil sands have received increasing environmental concerns, developing non-aqueous extraction (NAE) technique is of both fundamental and practical importance. However, the relatively high concentration of fine solids trapped in the extracted bitumen presents an obstacle for pipeline transport as well as upgrading and refining downstream. This research attempts to provide a solution to fine solids removal without using synthetic additives or affecting bitumen recovery from NAE process. Herein, naturally hydrophilic additives (i.e., water and high molecular weight guar gum (HGG) produced from Cyamopsiste tragonolobuosr L. Taup.) were introduced to promote the settling of fine solids suspended in bitumen-solvent solution, and the effects of solvents (i.e., toluene, cyclohexane and their mixtures) were systematically investigated. Aggregate size distribution analyzed by the focused beam reflectance measurements confirmed that the addition of water and HGG could promote the agglomeration and settling of fine solids in all solvents studied. However, the size range and quantity of the agglomerates vary significantly with the solvent's aromatic character. Solvent mixtures demonstrate a superior performance on removing fine solids from bitumen over single solvent. Specifically, in a 3:2 toluene/cyclohexane mixture, the solid content was lowered from 0.66 wt% to 0.09 wt%.