Method of smoldering combustion for refinery oil sludge treatment.

Refinery oil sludge is a type of hazardous waste generated during petroleum refining. Smoldering combustion has been studied in waste treatment but has not been applied to refinery oil sludge treatment. This work verified the feasibility of smoldering combustion for refinery oil sludge treatment through bench-scale experiments. Experimental result showed that the solid residue that remained from smoldering combustion of oil sludge was odorless, granular, and brick-red. The mass and volume of the residue were much smaller than those of the original oil sludge. The typical substances in the oil sludge (i.e., petroleum hydrocarbons [C10-C40]) were not found in the residue, thereby indicating the good performance of smoldering combustion in treating oil sludge. Water and oil were recovered by condensing the off-gas. The composition of the recovered oil was similar to coking diesel. The calorific value of the recovered oil was higher than that of kerosene, thereby demonstrating the possibility of reutilization. The components of noncondensable off-gas contained a small amount of SO2 and NOx and a large amount of H2, CO, and H2S, which need to be further purified. Three factors influencing the smoldering performance of oil sludge, including moisture content, filler to oil sludge ratio, and airflow rate, were explored.