Detailed chemical kinetics simulation of hydrogen hydrothermal combustion characteristics: Special effects of supercritical H₂O/CO₂ mixtures

Hydrothermal combustion of hydrogen is a key process in the H₂O/CO₂ mixed working medium thermal power generation polygeneration technology, a new coal utilization path. The flammability and stability of hydrogen hydrothermal combustion were evaluated using detailed chemical kinetics coupled with the chemical dynamics simulation method in this paper. The findings reveal that in supercritical water, pure hydrogen is difficult to burn; however, CO₂ can dramatically reduce the ignition delay time and lower the critical ignition temperature of hydrogen. This is because free radicals produced by CO₂ are actively involved in the chain-branching process of hydrogen oxidation, which promotes hydrogen ignition and combustion stability. Compared with gas combustion, hydrogen hydrothermal combustion has lower ignition temperature and can combust at lower parameters. Water is active in the reaction process, which produces the necessary free radicals for ignition, promotes combustion and influences the path of reaction, resulting in a relatively slow reaction rate.