Effect of steam jet on oil reclamation and purification from layered oily sludge

Steam is widely used to enhance heavy oil recovery, whereas it is implemented as just an auxiliary thermal source when treating oily sludge. In this study, steam jet was for the first time introduced to simultaneously reclaim and purify oil from layered oily sludge, a hazardous waste in storage ponds of oil joint stations. The effect of steam jet on oil reclamation and purification was investigated with various operating temperatures (200-350 degrees C) and mass ratios of steam to oily sludge (2:1-8:1). Batch experiments indicated that a high steam jet performance was achieved at 300 degrees C and 6:1 of the mass ratio, with 92% of oil reclamation rate and 82% of demetallization rate from the oily sludge of upper layer within 5 min. The mild temperature of the injection area (97 degrees C) was in favor of retaining light fractions of oil. Besides, the dynamic process of this steam-based treatment was numerically simulated with COMSOL to illuminate interactions among steam, oil and condensed water. With a significant reduction of oil viscosity due to steam heating, high dynamic pressure of steam jet was found to disturb the surface of layered oily sludge, expediting oil flotation in water. Meanwhile, the intense steam jet could also sufficiently scatter the floated oil to diffuse metallic impurities from oil droplets into surrounding water. The reclaimed oil after steam injection was more upgradable for a refinery while the residual oily sludge became more treatable with traditional recycling.