Effect of Top Gas Recycling Technology on the Softening, Melting and Dropping Behavior of V–Ti Bearing Burden in COREX Process

In COREX process, the top gas recycling (TGR) is an effective recovery and utilization technology for the high-quality gas by-produced from the melter gasifier, which can reduce its fuel consumption and emissions, and is of great significance to low carbon ironmaking. However, low concentration N2 is contained in the top gas, it is unfavorable to the smelting of V–Ti bearing burden because the high temperature solid solution Ti(C, N) is formed in the semi-coke bed and deteriorates the burden permeability of the melter gasifier. The effect of N2 concentration (0–10 vol%) on the softening, melting and dropping behavior of V–Ti bearing burden is investigated under simulated COREX conditions. Results show that the increasing N2 concentration will promote the formation of Ti(C, N), increase the slag viscosity and its wettability to coke, greatly increase the burden dropping temperature, which reduces the slag dropping rate from 68.2% to 18.8%. In addition, slag foaming is caused and the gas permeability of V–Ti bearing burden is deteriorated. The vanadium contents of dropping iron and residual iron are decreased from 0.051 wt% and 0.166 wt% to 0.043 wt% and 0.161 wt%, when the N2 concentration in reducing gas changes from 0 vol% to 10 vol%. If the pressure drop needs to be controlled below 20 kPa, the N2 concentration in the reducing gas should not exceed 5 vol%, that is, the top gas injection volume should be less than 60%.