Dynamic Analysis of Gas and Solid Flows in Blast Furnace with Shaft Gas Injection by Hybrid Model of DEM-CFD

In order to mitigate CO2 emissions from steel industry, decreasing coke rate by shaft gas injection such as top gas recycling is a favorable way. The conception based on oxygen blast furnace is able to bring several profits for intensifying gas reduction and decreasing coke rate by massive coal injection. In these processes, gas injection from auxiliary tuyere plays an important role to inject reducing gas or make up heat balance in the upper part. Therefore, the effect of shaft gas injection is considered to be so important factor to realize the above processes. In the present study, dynamic behaviors of gas and solid flow, and stress distribution between particles in the blast furnace with gas injection at different shaft levels were three-dimensionally examined by DEM-CFD. Since the permeability resistance of burden in blast furnace is dominant for gas flow, gas injection from auxiliary tuyere is restricted to specified areas due to the insufficient horizontal inertial gas force compared with upwards gas. Although these results are slightly influenced by the number of auxiliary tuyeres and gas velocity, the overall behaviors do not change. It was estimated that shaft gas did not diffuse uniformly. The penetration of shaft gas into center of the blast furnace is limited to peripheral zone. Thus, penetration area of shaft gas in horizontal section is almost proportional to ratio of shaft gas and gas from the conventional tuyere. Then, the change of stress distribution between particles was calculated and gas penetration effect was quantitatively clarified.