Briquets for washing blast furnaces

Periodic washing,of the hearth of a blast furnace by charging hard-to-reduce iron-bearing materials helps fiom fluid iron-bearing slags whose iron is reduced mainly by coke fines in the coke column. Lump iron ore, specially prepared washing sinters, or welding slag are usually used for this purpose. The washing sinter cotitains up to 50% ferrous oxide. One alternative to the washing sinter might be briquets made from mill scale. Washing briquets made from mill scale with a cement binder (8-10% Portland cement M500) are made by vibrational compaction. These briquets have good cold strength, remain intact when heated in a reducing atmosphere to 1200 degrees C at a rate of 500 degrees C/h (which corresponds to the rate of heating of the blast-furnace charge), and have low reducibility. Inside the fusion zone, the form primaty slags based oil iron-calcium olivines with all FeO content oil the order of 50%.