Numerical simulation study on enhancing the burnout of pulverized coal and the raceway smelting state in hydrogen-rich blast furnaces

To address the issue of decreased coal burnout when hydrogen is injected into the blast furnace tuyere, this study compared the effects of different coal powder particle size distributions, preheating temperatures of the coal powder, and oxygen enrichment rates on the combustion characteristics of the coal and the raceway state. The simulation results show that when the oxygen enrichment rate increases by 6%, the gas velocity at the tuyere outlet reaches maximum (314 m/s), which is more conducive to blowing through the center of the blast furnace and increasing the output. The 10-80 μm particle size distribution of the coal led to the premature release of volatile matter from the coal powder, resulting in an accelerated oxygen consumption rate and affecting the combustion of residual carbon, causing the phenomenon of "front hot and rear cold" in the raceway, which is not conducive to the uniform distribution and efficient utilization of heat. Increasing the coal powder preheating temperature by 250 K could increase the raceway temperature by 49 K, the coal burnout by 2.9%, and the molar fraction of reducing gases by 0.012. Although the promoting effect was not as significant as the 6% increase in oxygen enrichment rate, when combined with production costs, it can be observed that under the conditions of the coal powder particle size distribution of 10-100 μm and the preheating temperature of 250 K, higher burnout (74.6%) and more uniform high-temperature distribution can be ensured. The research results provide theoretical basis and data support for efficient smelting and energy-saving and emission reduction when injecting hydrogen into blast furnaces.