Self-reforming of coke oven gas in gas-based shaft furnace: thermodynamic analysis and reforming mechanism

The self-reforming of coke oven gas (COG) in a gas-based shaft furnace was investigated, employing metallized iron as a catalyst. Thermodynamic analyses, supported by FactSage 8.3 calculations and regression modeling, were used to investigate the effects of temperature (700-1100 °C), CO₂ (3%-10%), and H₂O (1%-9%) concentrations on CH₄ conversion efficiency. Results indicate that CH₄ conversion exceeds 90% at temperatures above 1000 °C, with CO₂ and H₂O concentrations at 9% and 5%, respectively. During the reforming process, introducing CO₂ provides additional oxygen, facilitating the oxidation of CH₄, while H₂O enhances H₂ production through the steam reforming pathway. Experimental findings reveal a CH₄ conversion of 85.83% with a H₂/CO ratio of 5.44 at 1050 °C. In addition, an optimal H₂O concentration of 6% yields the highest CH₄ conversion of 84.24%, while CO₂ exhibits minimal effects on promoting the reforming process. Increasing the metallization rate of pellets from 43% to 92% significantly enhances CH₄ reforming. This is mainly due to the fact that metallized iron is vital in promoting CH₄ dissociation and improving syngas yield by providing active sites for the redox cycle of CO₂ and H₂O.