Materials and energy recovery from oily sludges removed from crude oil storage tanks (tank bottoms): A review of technologies

Sludge and solids accumulating in crude oil storage tanks (referred as tank bottoms) reduces tank volume and requires periodic removal and disposal. Effective management of tank bottoms require considerations to reduce the toxicity of wastes and reduce potential environment impacts. This review compares alternative technologies for economical and environmentally beneficial management of oily sludges for recovery of hydrocarbons and energy with and without oil recovery. Management options with oil recovery include solvent extraction, centrifugation, surfactant oil recovery, and pyrolysis. Management options without oil recovery include incineration and anaerobic co-digestion. The selection of the appropriate technology depends on the characteristics of oily sludge, treatment capacity, as well as operation and maintenance costs. An efficient treatment can involve integration of different technologies for recovery of different oil fractions and to reduce energy demand. Technologies that utilize renewable energy (e.g., solar pyrolysis) can offset the high energy demand of pyrolysis process while recovering marketable products.