Objective The characteristics of molten slag produced by hot plasma melting of oil-based drill cuttings were investigated.

Methods The orthogonal experiment was designed with treatment power, treatment distance and treatment time as factors. XRD, XRF, SEM, heavy metal leaching and other means were used to identify the changes of oil-based drilling cuttings before and after melting and the effect of harmless treatment of oil-based drilling cuttings.

Results (1) The input power has a significant effect on the thermal plasma melting behavior of oil-based drilling cuttings. When the power is greater than 13 kW, oil-based drilling cuttings turn into spherical glass slag. When the power is 22 kW, the surface smoothness of the slag decreases. (2) The orthogonal test finds that the input power has the greatest influence on the mass fraction of the slag glassy phase, and the thermal plasma treatment distance has the greatest effect on the acid dissolution rate of the slag. When the melting temperature is above 1 300 ℃, the glassy phase mass fraction of the slag can reach more than 90%. (3) Thermal plasma can completely remove the organic matter in the oil-based drill cuttings. The contents of Cd, Ni, Zn and Pb in the slag are reduced to less than 0.200 mg/L, 1.000 mg/L, 0.027 mg/L and 0.100 mg/L, meeting the requirements of relevant policies and regulations about resource utilization.

Conclusions Thermal plasma can be used to melt oil-based drill cuttings into glassy slag and seal heavy metals in the glass plase to reduce the leaching rate of heavy metals to meet the needs of harmless. The research results can provide a certain reference for the industrial application of thermal plasma melting technology of oil-based drilling cuttings.