Evaluation of a self-sustaining ultra-rich H2-CO2-O2 premixed flame for potential application in CaCO3 hydrogenation

Inorganic metallic carbonate (like CaCO₃, MgCO₃) hydrogenation, i.e., carbonate decomposition in a H₂ atmosphere, is emerging as a promising green route to address the high CO₂ emissions associated with traditional industrial processes, such as cement and refractory materials production. However, the substantial heat requirement in the carbonate hydrogenation process has been rarely explored. In this work, we propose introducing O₂ into the CaCO₃ hydrogenation system to enable autothermal operation. As the first step, we simplify the system by replacing CaCO₃ with CO₂, focusing on the performance of a self-sustaining ultra-rich H₂-CO₂-O₂ premixed flame. The effects of volume percentages of CO₂ and O₂ (X_CO2 and X_O2) on the flame behavior and conversion efficiency of CO₂ are investigated experimentally. It is observed that the stable cone-shaped flame height increases as the X_CO2 value increases or the X_O2 value decreases. The CO₂ conversion efficiency increases significantly as X_O2 increases or X_CO2 decreases. The volume percentage of CO in the dry exhaust gas increases when both X_CO2 and X_O2 values increase. In contrast, the volume percentage of H₂ increases when X_CO2 decreases or X_O2 increases. Overall, the results attained in this work can provide useful guidance for the application of ultra-rich H₂ flame in the carbonate hydrogenation process.