Swelling of Iron Ore Pellets During Reduction

The extraordinary swelling of iron are pellets during reduction was analyzed in a controlled CO-C0 2 mixture at temp eraturefrolll 600 0 to 1 200°C.[n addition to the iron ore pel/ets, the pelletiz ing feed, several kinds if iron are, and reagent grade ferric oxides were reduced under the same condition as the pellets.M ost of swelling takes jJlace in the stage if reduction from wiistite to metallic iron.The apparent volume change is related to the appearance of fi brous iron as the reduction product . I. IntroductionFor the Japanese blast furnace which has increased her productivity by charging self-fluxing sin tel's, it has come into qu estion wh ether iron ore pellets as th e charging material for a blast furnace wi ll have more advantages than sintered iron ore in the n ear future.However, the first tria l to ch arge iron ore pellets, imported from the Marcona Mining Company, to a blast furnace did not succeed a s w ell as expected to improve op eration and productivity.It was a problem to be solved promptly.So far it was disclosed phenomenally that during reduction pell ets expanded and took powder form , and were not strong enoug h as blast furnace burd en.The cause of swelling of Marcona pellets has been discussed as due to carbon deposition or formation of , -hematite.I ) Watanabe and Yoshinaga 2 ) suggested the appearance of fibrou s iron from wustite to b e related to the extraordinary swelling of t he Marcona pellets.Matoba and Otake 3 ) observed previously fibrou s metalli c iron inThis paper will clarify the mechanism of swelling of iron ores, whose characteristic is not li mited to the Marcona p ellets.In other words, in gen eral, pure iron oxid e swells in the step from wiistite to m etallic iron in process of reduction and becomes fibrou s metallic iron under certa in conditions.