Numerical investigations on hydrothermal flame characteristics of water-cooled hydrothermal burner

Supercritical hydrothermal combustion, as a quick homogeneous oxidizing process, offers a promising treatment option for industrial wastewater. This paper established a computational fluid dynamics model of a water-cooled hydrothermal combustion burner to investigate the thermal flame characteristics. The effects of the fuel mass flow rate, fuel concentration, initial reactor temperature, reaction pressure, and oxidant temperature on the thermal combustion ignition were revealed. The results indicate that the fuel concentration (from 10 wt% to 60 wt%) and initial reactor temperature (from 623 to 773 K) had less effect on the ignition temperature. In contrast, the ignition temperature increases by 398 K with increasing fuel mass flow rate (from 24 kg h^-1 to 1080 kg h^-1). As the oxygen temperature increases (from 273 to 673 K), the ignition temperature gradually decreases to 573 K and then increases. An increase in reaction pressure can facilitate a decrease in ignition temperature to a certain extent, and the optimal reaction pressure is 25 MPa. This study provides a vital reference for a hydrothermal burner's scale-up design and ignition operation.