A CFD Model of COREX Gas-Based DRI Furnace for Optimum Gas Consumption

Most gas-based DRI (Direct Reduced Iron) furnaces use reformed natural gas as reductant which is richer in H₂ than CO. The present study deals with the Midrex DRI plant at JSW Steel Ltd., Vijayanagar where the reducing gas is derived from the COREX furnace top gas which is richer in CO than H₂. The thermo-kinetic behavior of the DRI furnace operated with COREX gas has been modeled. A mathematical framework was developed combining the heat and mass transfer equations with kinetic data for the gas-based reduction of pellets in a DRI furnace. Using the open-source CFD software, OpenFOAM, the equations were coupled and solved for steady state inside an axisymmetric 3D wedge. The model visualizes and quantifies the burden profiles, the gas composition, solid and gas temperatures for different operating conditions. The performance of the model was validated against plant scale-operating conditions and the process curves generated for different production rates. The obtained process curves highlighted lesser specific gas consumption at lower production rates and the importance of top gas CO₂ pct and top gas temperature as indicators of metallization inside the furnace.