Influence of coal type selection for blast furnace injection on combustibility and cost-performance ratio of blended coals

To reduce the cost of pulverized coal injection in blast furnaces and improve fuel utilization efficiency, comparative analysis was conducted on the combustion properties of typical anthracite, high-volatile bituminous coal, low-volatile bituminous coal, semi-coke and their respective blended coals. Based on industrial production data, regression relationships were established between pulverized coal utilization rate and combustion characteristic index, as well as between coal pulverization cost and grindability index. A cost-performance evaluation model was proposed that comprehensively considers effective calorific value, pulverized coal utilization rate and coal pulverization cost. The results indicate that high-volatile bituminous coal exhibits the optimal combustion performance, while anthracite shows relatively high ignition and burnout temperatures. The combustion temperature ranges of semi-coke and Xiangshan coal fall between those of high-volatile bituminous coal and anthracite, with semi-coke having slightly superior combustion properties to Xiangshan coal. Increasing the proportion of semi-coke in blended coals can effectively reduce the ignition temperature and improve combustion performance; however, due to the low effective calorific value of semi-coke, the cost-performance index of blended coals is decreased accordingly. Xiangshan coal has the highest grindability index among the tested coals and its effective calorific value is second only to that of anthracite. Although the combustion performance of blended coals is reduced under certain operating conditions after adding Xiangshan coal, the comprehensive cost-performance index is improved.