Fundamental Study On Oxidized Pellets Production And Metallurgical Properties Improvement For Typical Magnetite With High Alkalis Load

In recent years, with the rapid steel output growth, iron ore imports has also been increasing year by year, which leads to China’s steel industry dependence on imported iron ore above50%, severely restricting our country steel enterprise of the good development. In order to reduce raw material cost to improve the economic benefit, the steel enterprises in China pay much attention to the domestic iron ore resources development. The iron ore of west BayanObo of Inner Mongolia (Barun) is of fine grain, low price, and can be used to produce pellets. So Bao steel factory intends to make use of this good iron ore. However, there are several kinds of bad elements in it, including K, Na, F, CaO, MgO that have a far more higher proportion than others, which is not good for the pellets’properties to limits its utilization seriously. So, considering the pellets should be of good properties, it is an urgent job to explore this good iron ore’s appropriate rate in the row material, research how the bad elements affect the pellets properties, and find ways to improve the pellets properties to raise the iron ore proportion to low the cost.On the basis of practical row material and laboratory conditions, by modeling the pellets producing technological process in Bao steel factory, this paper changes the proportion of the iron ore, reagents including K, Na, F and CaO additives containing boron in the row material, so does the boronic iron concentrate. At meanwhile, the pellets’metallurgical properties including crushing strength and swelling index are investigated in this study.Through this study, the conclusions can be drawn as follows:(1) When the Barun iron ore and Bao steel iron ore concentrate are mixed to produce pellets, with the rising content of Barun iron ore in raw material, there is little difference in different kind of green balls strength. By contrast, the crushing strength of pellets decreases and the more proportion the lower strength will be. But the index of reduction swelling becomes higher and higher. To meet the practical demand for swelling index, the content of Barun iron should be controlled below30%.(2) By adding different reagents of K, Na, F, CaO to the pure iron ore concentrate of Bao steel factory respectively, the result indicates that the crushing strength changes little. But the reduction swelling becomes high and the reagent with K is the largest factor.(3) When the boron-magnesium compound additive is added into pellets by0.6%, on the basis of pellets properties being good, the content of Barun iron ore concentrate can be raised to40%.(4) If the boronic iron concentrate and Barun iron ore are used to produce pellets, the content of Barun iron ore can be raised to80%, with the pellets properties being good.(5) When5%boronic iron concentrate is added additionaliy into pellets with40%proportion of Barun iron concentrate, the crushing strength of pellets is largely raised and reduction swelling index is limited.(6) If7.5%boronic iron concentrate is added into pellets with40%proportion of Barun iron concentrate, the firing temperature can be reduced from1200℃to1150℃and the properties of pellets are good.