GB780980A - Improvements in and relating to the extraction of valuable constituents from slags - Google Patents

Abstract

Slag, whilst still in the original molten condition is treated with a gaseous or solid halogenating agent, or a halogenating agent in the form of a gaseous suspension, and volatile compounds such as iron, aluminium, manganese and vanadium chlorides are collected and separated. Suitable halogenating agents are gaseous chlorine and/or hydrochloric acid, alone or carrying entrained alkali or alkaline earth metal chlorides, e.g. sodium or calcium chloride, and these can be blown in below the level of the liquid slag. If desired an oxidizing gas (e.g. air) a neutral gas (e.g. nitrogen) or a reducing gas (e.g. carbon monoxide) may be present. If aluminium chloride is to be produced the combination should be strongly reducing. With basic open hearth slag, sodium chloride entrained in chlorine is preferred to calcium chloride in chlorine unless a temperature above 1500 DEG C. is employed; with an acid open hearth or acid Bessemer slag, gaseous chlorine and/or calcium chloride may be used. The slag may be tapped at 1600 DEG C. into a heat insulated cast iron refractory-lined vessel, taken to the place of treatment and joined to a hood under which the injection of halogenating gas or suspension takes place. The gaseous products are either passed through a box provided with baffles followed by an electrostatic precipitator or dust cyclone, conducted through a first condenser in which chlorides other than vanadium chloride and oxychloride are condensed, and a second condenser in which these two compounds are condensed. The remaining gas, if it contains hydrochloric acid or chlorine is recycled. Vanadium chlorides are decomposed to oxide by steam; iron and manganese chlorides are led to an aeration tank; hydrated ferric oxide is precipitated with caustic soda or limestone; a solution of manganous chloride remains. Examples are given in which slags containing stated proportions of all or some of silica, ferrous and ferric oxides, manganous oxide, calcium oxide, magnesium oxide, barium oxide, aluminium oxide and phosphorus pentoxide are treated at 1500 DEG C. with (1) chlorine; (2) calcium chloride entrained in a mixture of carbon monoxide, carbon dioxide, nitrogen and chlorine; (3) calcium chloride entrained in a mixture of air and chlorine.ALSO:A slag containing soluble sodium-silico-phosphates stated to be useful as a fertilizer is obtained by treating a slag such as a blast furnace or steel works slag whilst still in the original molten condition with a halogen salt entrained in a gas, e.g. in chlorine or hydrochloric acid.