Pyrolytic gas analysis and evaluation from thermal plasma pyrolysis of simulated oil-based drill cuttings

Oil-based drill cuttings (OBDCs) are hazardous wastes generated during shale gas exploration, and the rapid, efficient and safe disposal methods for OBDCs have attracted the attention of many researchers. Plasma pyrolysis technology is widely used in solid waste treatment due to its extremely high temperature and reaction activity. A laboratory-scale thermal plasma pyrolysis system was built to investigate the plasma pyrolysis mechanism of simulated OBDCs. The thermal decomposition characteristics of OBDCs were studied by thermogravimetric-derivative thermo gravimetric-differential scanning calorimetry (TG-DTG-DSC) analysis in the range of 50-1300 degrees C. The thermal decomposition process of OBDCs was divided into the following four stages: evaporation of water and light oil, evaporation and decomposition of heavy oil, carbonate decomposition, and phase change reaction from solid to liquid. The effects of the oil ratio, water content, and water/oil (W/O) ratio of OBDCs on the composition and gas selectivity of pyrolytic gas were investigated. The results show that thermal plasma can crack the mineral oil in the OBDCs into clean gases such as H2, CO and C2H2, while water can promote the decomposition of the heavy oil molecules and enhance the H2 production. The energy consumption model calculation for the pyrolysis and melting of OBDCs shows that the highest energy utilization and the lowest molar energy consumption of H2 were achieved at a W/O ratio of 1:4. Based on the thermal plasma pyrolysis system used in this study, the commercial application prospects and economic benefits of the plasma pyrolysis of OBDCs were discussed.