In order to explore the influence of unburned pulverized coal in ironmaking on the viscosity of blast furnace slag, the impact of temperature, volume fraction of solid particles and the rotating speed on the viscosity of CaO-MgO-Al 2 O 3 -SiO 2 heterogeneous slag were studied by experiment. The calculation model of relative viscosity of heterogeneous slag containing unburned pulverized coal is corrected. The results showed that the viscosity of heterogeneous slag increased with the increase of the volume fraction of the solid particles, and decreased with the increase of the rotating speed. For the heterogeneous slag with the same composition, the relative viscosity is not affected by the temperature and decreases with the increase in the rotating speed. The impact of unburned pulverized coal solid particles on the viscosity of the slag was much larger than the predicted value of the Einstein-Roscoe equation.
In order to improve the high temperature melting characteristics of bituminous coal with low ash melting point, three kinds of anthracites were used to improve the ash melting characteristics of blended coal to meet the requirement of blast furnace injection. The complete melting temperature of pulverized coal ash had been calculated by using FactSage thermodynamic calculation software. The results showed that after adding different proportions of anthracite with high ash melting point, the deformation temperature, softening temperature, hemispherical temperature, and flow temperature of the blended coal increased. After adding different proportions of Yang Quan anthracite, compared to Bu Lian Ta bituminous coal, the ash melting point of blended coal increased by 98, 136, 149, and 170 K, respectively. The relationship between the ash melting point of pulverized coal and the calculated value of ash complete melting temperature was obtained as: T ST = 0.7098T C + 257.98.
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.
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