Efficacy of Sonication on Crude Oil Tank Bottoms for Oil Recovery and Waste Minimization

Crude oil tank bottoms, a mix of oil, sediment, and water from crude oil collection tanks, are a significant waste stream associated with global oil production. In benchtop testing, as an intermediate evaluative step in progressive scaling toward industrial-scale treatment to recover oil from tank bottoms and to reduce waste, sonication was applied to samples from three California oilfields using only added water and mechanical mixing. The 2.2 kg sample size, over 40 times that used in most of the testing found in literature, utilized no chemicals during treatment. The tests employed a 1:4 ratio of sludge to added water in an acrylic tank with two 500-watt drop-in plate sonicators. Trial variables included sonication frequencies of 28 or 40 kilohertz, mixing speed, treatment duration, and oil collection methods. Oil recoveries up to 98.2% with mean recoveries of 27.4% were achieved using 0.2 kilowatt-hours per kilogram sample. This study indicated sonication treatment of crude oil tank bottoms with only added water and mixing was a potentially viable approach for waste oil recovery and waste minimization and warrants further investigation at even larger scale.