Ignition and Combustion Characteristics of Heavy Oil in Supercritical Hydrothermal Conditions

At present, the characteristics of supercritical hydrothermal combustion for heavy oils remain unclear, which severely limits the application of this process. In this work, the effect of key parameters on the characteristics of supercritical hydrothermal combustion of heavy oil are studied. The heat value at a heavy oil concentration of 30 wt.% is 12.21 MJ·kg⁻¹, significantly higher than that of an alcohol–water mixture with an equivalent mass fraction. Thus, the minimum ignition temperature of heavy oil can reach the subcritical temperature of 300 °C. Appropriately increasing pressure and the oxidation coefficient can enhance burnout efficiency, but an excessively high oxidation coefficient will produce adverse effects. The optimized parameters for heavy oil supercritical hydrothermal combustion are a preheating temperature of 350 °C, a fuel concentration of 30 wt.%, an oxidation coefficient of 1.5, and a reaction pressure of 25 MPa, resulting in a burnout rate of 99.15%.