Research On Dynamics Of Direct Reduction For Iron Ore By Coke Oven Gas

The gas base direct reduction iron technolog is the main force of the world direct reduction technology.The purpose of the experiment is the influence of the coke oven gas with different oxidiability on reduction and the reduction rate of iron and pellets. And on this base research of mechanism has been carried out. The reseach has provided base information and theoretical basis for the actual production.In the experiment iron and pellets is reduced by different oxidiability of oven gas with 3-sectional shaft furnaces and then weight lost is measured by weighing equipment, which is counted by the computer to get reduction process curve. Reduction rule of the iron and pellets is studied by reduction mass loss way with CO+H₂+H₂O+CH₄ gas mixtures.The result shows: the rate of reduction and Reduction Index (RI) of pellet had a little improvement with the increase of hydrogen gas .For example, the Reduction Index(RI) of pellet reaches 90.79% and metallized rate is 86.17% when the hydrogen gas content is 68%. While the oxidation of reduction gas is 0.087, the Reduction Index(RI) of pellet reaches the maximum of 91% and metallized rate reached the maximum of 86.5%; When the oxidation of reduction gas is lower than 0.087,the Reduction Index(RI) and metallized rate is creasing with the oxidation increasing, while the oxidation of reduction gas is higher than 0.087,the rule is opposite. Also, reduction and reduction rate is all augmenting in the condition of the same reduction gas. When the reduction reaction is to certain extent, reduction rate is hard to be increased though the reduction time is extended. optimum reduction condition is that the hydrogen gas content is 68.3%,the oxidation of reduction gas is 0.087 and the temperature is at 900℃.The result shows that external diffusion resistance is growing with the temperature higher from 750℃to 800℃, 850℃and 900℃,and the interface-chemical reaction resistance is growing with the temperature varying from 900℃to 850℃, 750℃and 800℃in the condition of the same reduction gas. External diffusion resistance quickly enlarges to be the main force with the temperature of 900℃. So external diffusion resistance played a crucial role in the process of high temperature reduction. In every condition of reduction, the interface-chemical reaction resistance increases with the increase of reduction degree. external diffusion resistance reaches the maximum when the iron and pellets is reduced by coke oven gas in the condition of the same temperature, and the interface-chemical reaction resistance reaches the maximum with the hydrogen gas content of 68.3%.