THE REDUCING VELOCITIES OF AN IRON ORE BY THE VARIOUS GAS MIXTURES OF CO, CO_2 AND N_2

The reducing velocities of the Johore hematite ore were tested by the various gas mixtures of CO, CO_2 and N_2. The reducing gas, in which the sum of the partial pressures of CO and CO_2 was kept at 0.4 or 0.6 atm. press., and the ratios of CO_2/CO were varied from zero to 2.5, was passed through the sample in the rate of 100cc per min. The temperature of the experiments were 700, 800, 900 and 1, 000℃. The CO_2 in the exhausted gas passed through the sample was analysed every ten minutes, and thus the amount of oxygen from the iron ore was calculated from the difference between the volume of CO_2 contained in the exhaused gas and the same in the reducing gas. From the results of the above experiments we concluded as follows : - (1) The more the ratio of CO_2 to CO in the reducing gas increases, the more the reducing velocity of the ore decreases, and at the lower temperature, a small variation of that ratio effects more greately on the reducing velocity than at the higher temperature. In general, when the value of CO_2/CO in the reducing gas approaches the value of CO_2/CO at the equilibrium condition of the reaction FeO+CO⇄Fe+CO_2, the reducing velocities become very slow. (2) Being referred our experimental results to the reports of W. A. Schlesinger, who had measured the temperatures and the ratios of CO_2 to CO in the furnace gases at the various heights in an iron blast furnace, the reducing velocities of an iron ore in the various heights of the stack of the aforesaid blast furnace were surveyed. Taking the temperatures, the partial pressures of CO+CO_2 and the ratios of CO_2 to CO equal to those measured by W. A. Schlesinger, we find from our experimental curves that the time taken for the reduction of the Johore ore at 700℃ is about 33 times of that at 1000℃ in our experiment in which we passed 100cc. of the reducing gas per min. through 1g of the sample of 1mm. size.