Numerical simulation of combustion behaviors of hydrochar derived from low-rank coal in the raceway of blast furnace

Pulverized coal injection is an important technology to reduce the cost of hot metal and the emission of pollutants in blast furnace (BF) ironmaking process. The hydrochar as an upgrade product from low-rank coal can be injected into BF to replace pulverized coal of anthracite, thus leading to a significant cost saving. However, there has been no investigation about using the hydrochar derived from low-rank coal for the BF injection. A three-dimensional model including coal lance, blowpipe, tuyere and raceway has been established to investigate the combustion characteristic of the hydrochar. The results show that there is little difference for the flow and combustion behaviors of the hydrochar and pulverized coal. The combustion rate of the hydrochar is faster at the tuyere, and the highest temperature is closer to the outlet of the lance. The highest temperature obtained in the combustion process is higher than pulverized coal. The penetrability of the gas increases as the velocity of the gas and the carbon monoxide concentration increase when the hydrochar injected into BF, which is beneficial to BF ironmaking. In addition, the burnout is higher for the hydrochar compared with the pulverized coal. The finding in this work would be useful in revealing the combustion mechanism of the hydrochar and provide valuable information on injecting hydrochar to BF with high efficiency.