In-Process Steam Cleaning of Ceramic Membranes Used in the Treatment of Oil Sands Produced Water

Abstract

Current oil sands extraction technologies expend a significant amount of energy in the treatment and recycling of the oily process waters that are generated during the extraction process. Ceramic membranes are promising candidates for enhancing the energy efficiency of the produced water deoiling process due to their low energy requirements. However, membrane fouling by bituminous solids remains a significant barrier to the widespread acceptance of membranes in this application. As an alternative to chemical membrane cleaning, a steam regeneration technique was applied to ceramic membranes in the filtration of steam-assisted gravity drainage (SAGD) produced water. This technique involved the periodic injection of steam directly into the membrane feed channels, and was applied in conjunction with conventional permeate backflushing. Tubular multilumen ceramic membranes with titania selective layers having pore sizes of 5 or 10 nm were used. Support layers were composed of either alumina or titania. Optimal transmembrane pressure and crossflow velocity settings were found to be 50 psi and 1 m/s over the investigated ranges. Membrane permeate fluxes increased from 50 to 200 Lmh when the steam regeneration method was activated. Flux enhancement was found to depend on the initial duration of filtration without steam injection, which results in significant irreversible fouling. Steam regeneration also improved membrane separation performance, increasing total organic carbon, sulfate and chloride retention by as much as 19%, 17% and 10%, respectively. Steam regeneration is a continuous in-process method that offers the possibility of recycling the oleophilic cake released from the surface of the membrane. The cake can be sent to a flotation unit upstream of the membrane system, allowing bituminous fines to be entrained in the main oil stream. This offers many possibilities for waste minimization, particularly in remote areas where cleaning fluids that are produced when membranes are chemically cleaned would need to be transported and treated off-site.