Effects of direct reduced iron on blast furnace smelting indexes

To address the challenges of carbon emission reduction and iron ore resource constraints, the influence of direct reduced iron （DRI） on the key smelting indexes such as theoretical combustion temperature, bosh gas index and productivity coefficient of blast furnace was studied by establishing the energy and mass balance model of adding DRI to blast furnace. The results indicate that adding a significant amount of DRI easily leads to insufficient heat of blast furnace. Constraining the total heat loss of the blast furnace to no less than 80% of the base case, the maximum DRI addition is 2.6%. A further decrease in the metallization rate of the DRI would exacerbate the total heat expenditure of the blast furnace. Under the premise of maintaining the heat loss consistent with the base case, the suitable amount of DRI that could be added is almost the same after either increasing the blast temperature or the oxygen enrichment ratio. Although increasing the pulverized coal significantly increases the suitable DRI amount, the theoretical combustion temperature and bosh gas volume index of blast furnace are seriously deteriorated. Increasing the blast temperature or oxygen enrichment ratio on thermal compensation is basically the same and can be replaced by each other, and problems such as the decrease in theoretical combustion temperature caused by pulverized coal injection are alleviated. Under comprehensive thermal compensation measures, the maximum DRI addition reaches 12.12%, and the carbon consumption per ton of hot metal decreases by 56 kg.