Industrially, direct reduction of iron oxides is a strong endothermic reaction, so only the temperatures above 1 000 to 1 100℃ enable reduction reactions to proceed at a rapid rate.
However, it is thermodynamically impossible to industrially enforce the reduction process by solid carbon since the temperature does not rise to 1 100℃ in the sponge iron manufacturing process and to more than 1 350℃ in the case of granulated iron. In other words, if the feed is not mixed evenly, CO gas will not participate in the reduction reaction but will be gone. In addition, the CO2 produced by indirect reduction is not modified to CO, so the carbon required by the sponge iron manufacturing process is two to three times more than the theoretical amount.
Therefore, making coal composite iron ore with fine iron concentrate and coal powder to produce reduced iron can further improve the reduction reaction characteristics of iron oxide and reduce coal consumption.
Ro Myong Su, a researcher at the Faculty of Metallic Engineering, has investigated the characteristics of direct reduction reactions by solid carbon and decided the optimum reduction conditions of the coal composite iron ore—the main materials in a new smelting reduction iron-making furnace.
Firstly, he conducted a softening test to choose the optimum agglomerant. Secondly, he investigated the effect of factors on the reduction characteristics of coal composite iron ore by the mass flop-out method, and decided the optimum reduction conditions.
The results show that the optimum reduction conditions for more than 80% of the reduction ratio in the case of direct reduction of coal composite iron ore by solid carbon are as follows: temperature 1 250℃, carbon-containing ratio 1 and its size 30mm.