Penetration Effect of Injected Gas at Shaft Gas Injection in Blast Furnace Analyzed by Hybrid Model of DEM-CFD

Abstract

Shaft gas injection of reducing gas in the blast furnace is one of favorable ways to greatly decrease CO2 emissions from steel works, and this approach is used for the top gas recycling and oxygen blast furnace processes. In these processes, the penetration effect of the gas injected from the auxiliary tuyeres is important for attaining effective gas reduction or making up the heat balance in the upper part, and so it is useful to analyze the dynamic behavior of the gas injected into the shaft. In the present study, the penetration effect of injected gas was three-dimensionally simulated by a hybrid model of the discrete element method (DEM) and continuum model (CFD). In particular, the CFD model was used to quantitatively analyze the dynamic gas flow and the pressure distribution in the burden layers calculated by DEM. Although the area influenced by the injected gas from the auxiliary tuyeres was restricted to a specific area due to insufficient horizontal inertial force of the gas, the penetration area gradually enlarged as the gas velocity from the auxiliary tuyeres increased. In a small blast furnace, the injected gas can easily reach the center with the higher gas velocity, and it was shown that the relative penetration depth of the injected gas depends on the inner volume of the blast furnace. However, the overall behavior of the injected gas did not show any remarkable change. In conclusion, the penetration area of shaft gas was almost proportional to the ratio of shaft gas and the upward gas from the conventional tuyeres.