Petroleum refineries accumulate a considerable quantity of oil sludge from refining processes. The effective disposal of crude oil sludge generated from petroleum industry during crude oil transportation, storage and refinery process is a worldwide problem: Common sources of these sludges are storage tank bottoms, oil-water separators, flotation and biological wastewater treatment units, cleaning of processing equipment, and soil- from occasional minor spills on refinery grounds [1]. Generally the oil sludge is a complex water-in-oil emulsion and consist 30-50 % of oil, 30-50 % of water and 10-12 % of solids by mass [2]. Oil sludge contains mainly heavy organic compounds and a large amount of combustible matters with high heating values [3]. This waste is hazardous in nature and their disposal or effective resource recovery is an important global issue [4].
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