A review on resource utilization of oil sludge based on pyrolysis and gasification

Oil sludge is a hazardous solid waste produced from crude oil extraction, transportation, and refining. The yield of oil sludge is huge and the harmful substances in oil sludge such as heavy metals, germs, benzene series, etc. cause harm to environment and humans. Reduction, harmlessness, and recycling are requirements for oil sludge treatment. Compared with other treatment methods, pyrolysis/gasification of oil sludge can produce pyrolysis oil, gas, and syngas. In this review, oil sludge physicochemical characteristics were introduced. The principle, kinetic characteristics, influencing factors, pyrolysis/gasification reactors, and product characteristics of oil sludge pyrolysis/gasification were discussed. To enhance the thermal conversion efficiency, catalytic pyrolysis and co-gasification were suggested. In addition, the high value utilization ways such as the production of supercapacitors and adsorption materials using char were exhibited. The pyrolysis of oil sludge has been developed from basic research to pilot scale and then to industrial application. In industrial applications, the oil recovery rate exceeds 80%. Syngas accounts for 30-40 wt% of gasification products. The gasification of oil sludge is currently in the laboratory or pilot scale stage, and there is still a long way to go before industrial application. The oil sludge integrated thermal treatment process and the oil sludge comprehensive thermal treatment process using gasification and combustion were illustrated from the perspective of energy recovery. In the process of pyrolysis/gasification, there are some problems such as serious coking, low thermal conversion efficiency, high energy consumption, and poor product performance. Finally, the development prospects of oil sludge pyrolysis/gasification were prospected.