Theoretical analysis on the injection of H2, CO, CH4 rich gases into the blast furnace

The aim of this work is the determination of the combustion characteristics of two different fuel gases for their blast furnace utilization. The availability of gas from the coke production as well as from the basic oxygen furnace (BOF) process in an integrated metallurgical plant makes it possible to substitute reducing agents like oil. For a description of the varieties of the gases, coke oven gas (COG) and a mixture of COG and BOF gas, four independent modeling approaches were applied to cover all aspects. The different applied modeling approaches are the thermodynamic equilibrium, the plug flow reactor (PFR) model with detailed chemistry with or without, resp., consideration of the mixing time and computational fluid dynamics (CFD). This guarantees an improved understanding of the whole combustion process. The earlier ignition of the COG/BOF gas mixture in comparison to the COG can be ascribed to the higher excess air ratio, in spite of the better ignition propensity of COG. The higher net calorific value of the COG results in higher combustion temperatures, which implicates a higher thermal strain on the tuyere. In addition, greater amounts on CO and H-2 in the raceway result from the COG combustion.