Energy & Fuels, Vol.30, No.7, 5253-5258, 2016
Dewatering Bitumen Emulsions Using Interfacially Active Organic Composite Absorbent Particles
One of the major challenges in petroleum production is the formation of undesirable emulsions, which often leads to an increased cost for downstream operations. This problem is exacerbated for bitumen, which contains a greater fraction of interfacially active materials known to stabilize small emulsified water droplets that are extremely difficult to separate. To accelerate separation of emulsified water droplets from bitumen, chemical demulsifiers are extensively used to modify interfacial properties, promote droplet flocculation, and facilitate coalescence of the emulsified droplets. However, the use of chemical demulsifiers is rather system-specific as a result of the overdosing phenomenon. As an alternative to chemical demulsification, composite absorbent particles, prepared by dehydrating well-designed water-in-oil emulsion droplets, were proposed to promote dewatering of water-in-diluted bitumen emulsions. The composite particles were composed of nanosize magnetic particles dispersed in an absorbent matrix coated with an interfacially active material. The composite structure combines the absorptive capacity of sodium carboxymethyl cellulose for water with the interfacial activity of ethylcellulose while retaining the magnetic responsiveness of dispersed Fe3O4 nanoparticles. Using composite absorbent particles, nearly complete dewatering of water-in diluted bitumen emulsions was achieved by increasing the dosage of absorbent particles. The dewatering rate was improved using smaller particles of greater specific surface area or increasing mixing intensity to promote contact between absorbent particles and emulsified water droplets. Although the surface of composite absorbent particles was initially suitable for dispersing in non aqueous media, the subsequent change in wettability upon absorption of water (hydration) caused hydrated absorbent particles to aggregate, providing an opportunity for regeneration/reuse of hydrated particles by first separation particles from diluted bitumen through gravity separation or a filtration process.