The Kinetics Of The Gas-based Reduction Of Iron Oxide

Iron and steel industry is the important basis industry in our national economy, the Direct-reduced iron technology is one of the most active and concerned directions in the development of the iron and steel industry. With the progress of coal chemical technology, the shaft furnace-coal making gas technique proves to be the dominant method of Direct-reduced steelmaking. In order to take deep insight into the reaction behavior and mechanism of gas-basis Iron Ore, we study the weightless behavior of ferric oxide in the following different reaction atmosphere using the thermo-gravimetric analyzer, firstly at the temperature range of 400～750℃, hydrogen concentration of 100%,75%,50% and 25% in the reaction atmosphere has been studied; then carbon monoxide concentration of 75%,50% and 25% at the temperature range of 700～750℃; at the end, pure methane atmosphere at the temperature range of 800～950℃. We analyze the kinetic parameter on different reaction conditions, and definite the reduction process and reaction mechanism of ferric oxide on different conditions.The results show that:the reduced behavior of ferric oxide in the atmosphere of hydrogen, carbon monoxide and methane has many similarities with each other. When the temperature are lower than 570℃, the reduced sequence of ferric oxide is Fe2O3→Fe3O4→Fe; and the reduced sequence is Fe2O3→Fe3O4→FeO→Fe at the temperature higher than 570℃.The reduced reaction of ferric oxide in the atmosphere of hydrogen with its concentration of 100%,75%,50% and 25%, and at the temperature of 400～550℃, the first stage of the reduction process agrees with the Chemical reaction model and the reaction order is 2/3, the second stage agrees with the three Dimensional diffusion model and the order is 1/2. At the temperature of 600～750℃, the first stage of the reduction process agrees with the Chemical reaction model and the reaction order is 2/3, the second stage of the reduction process agrees with the Nucleation and Subsequent generation model and the order is 3/4, the third stage agrees with the three Dimensional diffusion model and the order is 1/2.The reduced reaction of ferric oxide in the atmosphere of carbon monoxide with its concentration of 75%,50% and 25%, and at the temperature of 700～850℃. The first stage of the process agrees with the Chemical reaction model, the order is 2/3 when the concentration of CO is 75%, and when the concentration is lower than 50%, the order is 3. The second stage agrees with the Nucleation and Subsequent generation model, the order is 2/3 when the concentration is 75%, and when the concentration is lower than 50%, the order is 1. The third stage agrees with the three Dimensional diffusion model and the order is 1/2. The reduced reaction of ferric oxide in methane, the first stage is controlled by the interface reaction and the order is 1/2; the late second stage is controlled by the three dimensional diffusion.The reduced reaction of ferric oxide in mixed gases (H2,CO and CH4) at the temperature of 700～850℃. The first stage of the reduction process agrees with the Chemical reaction model and the reaction order is 2/3, the second stage of the reduction process agrees with the Nucleation and Subsequent generation model and the order is 3/4; the third stage agrees with the three Dimensional diffusion model and the order is 1/2.