Numerical simulation research on the co-combustion of biochar and pulverized coal in the raceway of blast furnace

This study explored the potential of using biochar as a supplementary fuel to replace pulverized coal in blast furnaces. A three-dimensional CFD simulation model with a binary particle approach was used to analyze the cofiring of biochar and coal, focusing on gas flow, temperature, concentration, and burnout distribution. The results showed that biochar, with a higher volatile content than coal, has a faster devolatilization rate and a significant gas expansion effect, which leads to the formation of a low-density gas phase dilution zone at the nozzle entrance, reducing local airflow speed. The addition of biochar to coal can effectively increase the volume proportion of the high-temperature region in the raceway, enhance the preheating and complete combustion of pulverized coal particles, and improve burnout efficiency. Furthermore, the simulation value was higher than the theoretical value, quantitatively verifying the synergistic enhancement effect between the two fuels during combustion. The synergistic enhancement effect was evident when the biochar proportion in the mixture was 77 %. These results support the application of biochar in the steel industry and promote sustainable ironmaking methods.