Effect of MgO Injection on Smelting in a Blast Furnace

The effects of the simultaneous injection of MgO and magnesite powder on the combustion of coals, properties of the primary slag, and softening-melting properties of the burden were investigated. There were four aspects to the results that we obtained. First, MgO showed catalytic activity for dehydrogenation and carboxyl group removal from coal; as a result, with increasing MgO, the combustion ratio and pyrolysis ratio of the coal investigated improved. Notably, when the content of MgO increased from 0% to 3.21%, the combustion ratio increased from 67.75% to 75.73%. Secondly, the MgO distribution in the slag sample was close to that in the standard slag after melting for 10 min. After 50 min, the difference in MgO content between the slag and standard slag samples was less than 1%. Thirdly, with an increase in the content of MgO, the short-slag feature of the slag was obvious, the viscosity fluctuated wildly, and the melting temperature increased significantly. It is proposed that the properties of the primary slag could be improved by decreasing the MgO content. Finally, with the increase in the MgO added to the burden, the softening-melting properties of the burden degraded. When the MgO content was 0.86%, ΔPmax was only 2.04 kpa, and S 59 kPa·°C. However, when the MgO content was 2.61%, ΔPmax was 20.00 kPa, and S 1349 kPa·°C. Therefore, the technology of MgO injection into tuyeres with pulverized coal was beneficial for blast furnace operation