Lab-scale Process Parameter Determination of a Two-stage DRI (direct reduced iron) Process Using Reformed COG (coke oven gas)

Abstract

On the road to carbon neutrality, a great deal of attention is being paid to emerging technologies such as the DRI (direct reduced iron) process. This study proposes a two-stage DRI process using reformed COG (coke oven gas), and determined optimal process parameters. The reduction and carbonization of Carajás iron ore used in the field were examined by monitoring the weight loss of the samples, and EDS and XRD measurements with respect to the reaction temperature and operating time for different reducing environments. While the reduction of iron ore is completed in 60 min at 800oC regardless of the reducing environment, the carbonization of reduced iron is attainable only at 800oC with high hydrogen content in the reducing gas. Thus, a countercurrent scheme in the proposed DRI process is justified, in which COG containing high hydrogen content is flowed into the 2nd stage operated at 800oC and subsequently directed to the 1st stage operated at 600oC. The reduction of iron ore is initiated in the 1st stage for 60 min irrespective of the reducing environment, and the completion of the reduction and the following carbonization is fulfilled in the 2nd stage for 40 min under a high reducing environment. An equilibrium analysis supported that the cracking of CH4 in COG to graphite leads to the formation of CO from CO2 and the successive formation of Fe3C from reduced Fe. The carbonization of iron ore is possible only in the presence of CO2 . It also showed that too high or low reducing environments are not desirable to accomplish the DRI process. This study is expected to be provide an effective guideline for optimizing similar DRI processes.