Catalytic pyrolysis of oil-based drill cuttings over metal oxides: The product properties and environmental risk assessment of heavy metals in char

Abstract

Oil-based drill cuttings (OBDC), a hazardous organic waste generated from the exploration and extraction of shale gas fields, have received widespread attention for their safe disposal and utilization. In this study, OBDC pyrolysis experiments were conducted on a fixed-bed reactor. The effects of temperature (450 °C, 500 °C, 550 °C, and 600 °C) and catalysts (MgO, Fe2O3, and CaO) on product distribution, oil quality, and potential ecological risk assessment of heavy metals were investigated. Results revealed that the oil yield reached the maximum (14.94%) at 500 °C in uncatalyzed cases. The addition of catalysts could increase the total yield of oil and gas. In particular, the oil yield increased by 13.32% with CaO catalysis, while the oil recovered by MgO and Fe2O3 was almost the same as without catalyst. In addition, the higher low heating value (LHV) of oil (41.46 MJ/kg) and gas (34.07 MJ/Nm3) were found with CaO catalysis, implying that CaO has better performance on recovery of oil and gas than MgO and Fe2O3. Moreover, the oil content of char was far below 0.3%, the potential ecological risk assessment of heavy metal in char showed slight risks to the environment, suggesting that char can be treated as general solid waste.