Abstract
Although it is ideal to obtain a magnetically uniform product when hematite is reduced to magnetite by roasting, pracbically always over reduction is accompanied and this causes a low recovery of iron as magnetic conrentrate. The auther studied reducing conditions on ores from Taikozan, Ohtoen, Higashi Anzan, and Nishi Anzan mines using coke oven gas and clearly demonstrated a way to obtain a magnetically uniform product and pointed out the followings;
1. The ores from above mentioned mines changes to Fe2O4 and completely magnetized by reducing with coke oven gas (CO2 3.6, O2 1.5, CnH2n 2.2, CO 93, H2 42.4, CH4 22.4 1 for 30 minutes at 600°C. However, if this operation is continued longer they are easily over reduced.
2. When Fe2O3 is reduced with coke oven gas Fe2O3 Fe3O4→FeO→Fe takes place and the last stagb is rather difficult, and therefore, it is apt to result considerable amount of FeO which is nonmagnetic.
3. Thermno-balance experiment on oxidation of over reduced ore shows FeO→Fe3O4 commences at 150°C and proceedes easily but Fe3O4→Fe2O3 is rather difficult even at higher temperature. By oxidation at 200-400°C the over reduced ore becomes a uniform magnetic product and consequently it gives a high recovery of iron by magnetic concentration.
4. Although this is a Iaboratory result, the auther believes that if the ore is reduced with coke oven gas at 600-700°C and quenched in air at about 400°C magnetically uniform product is obtained.
