Influence of Structural Variations of Demulsifiers on their Performance

Chemical demulsification is the most widely used method for breaking water-in-diluted bitumen emulsions in oil sands processing. In this work, the properties and performance of six samples of ethylene oxide (EO)-propylene oxide (PO) block copolymer demulsifiers from two families were investigated. The demulsifiers were characterized by their relative solubility number (RSN), EO content, PO content, and molecular weight (MW). The results showed that the performance of the demulsifiers is correlated to the starting base compound, EO content, PO content, RSN, MW, degree of cross-linking, interfacial tension (IFT), yield stress of underflow, and bitumen loss. Demulsifiers with higher MW and more EO-PO branching had higher dehydration efficiencies when the EO content was varied from 0% to 40% at constant PO content. An increase in MW by cross-linking EO-PO copolymers improved the dehydration efficiency. In this work, an appropriate rheological method was developed to correlate the properties of the demulsifiers with the properties of the underflow. The yield stress of the underflow, including settled solids, water, and the rag layer, increased with increasing RSN value and dosage of demulsifier. At high dosages, the yield stress values were high because of an increased number of aggregates, which, in turn, restricted underflow. An increase in the RSN value of the demulsifiers led to more bitumen loss to the underflow, which increased the size of the aggregates present in the underflow, resulting in increased immobility and constriction and higher yield stress.