Ash melting behavior and mechanism of high-calcium bituminous coal in the process of blast furnace pulverized coal injection

Abstract High-calcium bituminous coal has the advantages on combustibility, but its ash melting point is low, and it is easy to slag in blast furnace injection process. In order to explore the ash melting slag formation mechanism of high-calcium bituminous coal, the mineral evolution of ash in the combustion process of high-calcium bituminous coal and the influence of ash components on the liquid formation in the melting process were studied. The results showed that the melting behavior of ash gradually occurs with the change in the morphology, and the main mineral transformation is carried out around different deposition forms of Ca and Si. The liquid phase formation of ash at high temperature is the essential reason of its melting behavior. The higher the content of CaO, the higher the starting temperature of the liquid phase formation. The higher the content of SiO2, the lower the starting temperature of the liquid phase formation, and the more the liquid phases generated at a given temperature. Increasing the content of Al2O3 can expand the temperature range of reducing the formation of ash liquid phase to 1,473–1,673 K. When the temperature is above 1,573 K, Fe2O3 can promote ash liquid phase formation.