Function of Sponge Iron In Electric Furnace

March 25, 2021

Function of Sponge Iron In Electric Furnace

The commonly used raw material for electric arc furnaces is scrap steel because scrap steel is cheap and relatively easy to obtain, but social scrap often contains unwanted impurity elements. In order to reduce harmful impurities in scrap steel, a certain amount of pig iron or sponge iron must be added to dilute the scrap steel. The residual metal elements can keep the residual element content in the final molten iron or molten steel at an acceptable level. In the electric arc furnace smelting, the advantages of low-sulfur sponge iron are particularly obvious, because there is no need to desulfurize in the furnace, which can save a lot of time.

The traditional charging method of the electric arc furnace is to uncover the entire furnace cover and load the charging materials into the furnace with a basket hoisted into the top of the furnace. Using this traditional charging method not only prolongs the charging time but also loses a lot of heat. The sponge iron can be loaded into the furnace through small holes, so it is not necessary to uncover the entire furnace cover again after the starting material is melted. Furthermore, it is not required that a large amount of charge is charged into the furnace at one time, and the sponge iron can be continuously fed into the electric furnace at the same speed as it melts, so higher smelting efficiency can be achieved.

Due to the inherent difference between sponge iron and scrap steel, the following four items need to increase energy consumption when using sponge iron:

　　1) Melt the amount of slag added due to the higher content of sponge iron gangue;

　　 2) Lime is added to melt the gangue;

　　3) Endothermic reduction of residual iron oxide;

　　4) Heat loss of carbon monoxide gas due to reduction of iron oxide.

　　 From the first three items listed above, it can be seen that in order to reduce energy consumption to the lowest level, it is required that the gangue content be as low as possible and the metallization rate as high as possible. However, if the sponge iron gangue content is low (under 2%) and the metallization rate is high (95% or more), the total smelting time can be shortened, and the loss caused by heat transfer and radiation can be minimized. The amount of increase in energy consumption is less than calculated.