REDUCIBILITY TEST OF IRON ORE LUMPS
Teruo Ikeno, Tomoro Hagiwara
The authors investigated the gaseous reducibility of several ores in order to estimate the maximum size of ore suitable for blast furnace charge.
About 1kg of each ore, which was crushed to various size (maximum of 3 in), was treated at 900°C using 20l/min/kg of H2 gas as a reducing medium. The reduction degree was based on the total weight of oxygen which combined with the iron in ore, and measured by means of the loss-in-weight method.
It was found that the reduction velocity became higher in the sequence of magnetite→hematite→limonite, and that the higher the porocity of each kind of ores the higher the reduction velocity. Curves expressing the relation between the ore size and the time required for 90% reduction showed a trend to diverge in the case of magnetite and dense hematite, while in the case of porous hematite and limonite to converge.
Further, the authors assumed the maximum size (suitable for blast furnace charge) of hematite-ore of 24% porosity to be 2" (in dia.) and took the size of the other ore which reqiured the same time for 90% reduction as that of the above mentioned standard ore as its maximum size.
It was concluded from the results that the maximum size for magnetite was 25-30mm except those which had very low reducibility, about 40mm for dense hematite and about 50mm for porous hematite. With hematite and limonite of high porgsity or those which suffered cracks during heating, the size of org became no more a dominating factor upon reducibility.