GB1032747A - Manufacture of ferro-silicon - Google Patents

Abstract

Ferro-silicon e.g. containing 14 to 95% Si is made by pelletizing or briquetting a finely divided mixture of coking coal with iron ore and silica, and coking or carbonising the pellets or briquettes partially or completely to produce a cellular coked structure holding the components of the charge together e.g. interstitial partially reduced finely divided iron ore containing silica, until final reduction to Fe-Si in an electric smelting furnace. Preferably only water is used as a binder for the pellets (or briquettes) but binding agents such as bentonite, sulphite lye or starch may be added to increase the strength of the "green" pellets. Also anthracite, charcoal or coke may be included, and the total amount of carbon may be in excess to provide the requisite amount in the final alloy. The iron ore may be partially replaced by comminuted steel or iron or other forms of iron oxide such as rolling mill scale, and the silica may be in the form of tailings from dressed siliceous iron ores or sand. The pellets may be dried e.g. at 100-300 DEG C. before the coking or carbonising step, which may be performed at 800-1300 DEG C. either within the smelting furnace or outside, e.g. on a grate or in a charging hopper, using the heat provided by combustion of at least part of the combustible gas (mainly CO) produced in the final reduction and/or of part of the coal in the pellets and/or of volatiles produced in the step.ALSO:Ferro-silicon, e.g. containing 14 to 95% Si, is made by pelletizing or briquetting a finely-divided mixture of coking coal with iron ore and silica, and coking or carbonizing the pellets or briquettes partially or completely to produce a cellular coked structure holding the components of the charge together, e.g. interstitial partially reduced finely divided iron ore containing silica, until final reduction to Fe-Si in an electric smelting furnace. Preferably only water is used as a binder for the pellets (or briquettes) but binding agents such as bentonite, sulphite lye or starch may be added to increase the strength of the "green" pellets. Also anthracite, charcoal or coke may be included, and the total amount of carbon may be in excess to provide the requisite amount in the final alloy. The iron ore may be partially replaced by comminuted steel or iron or other forms of iron oxide such as rolling mill scale, and the silica may be in the form of tailings from dressed siliceous iron ores or sand. The pellets may be dried, e.g. at 100-300 DEG C. before the coking or carbonizing step, which may be performed at 800-1300 DEG C. either within the smelting furnace or outside, e.g. on a grate or in a charging hopper, using the heat provided by combustion of at least part of the combustible gas (mainly CO) produced in the final reduction and/or of part of the coal in the pellets and/or of volatiles produced in the step.