Verfahren zur Gewinnung von Eisen aus Eisen- und Titanoxyd enthaltenden Materialien

摘要

Iron, titanium and aluminium values are recovered from materials comprising their oxides, together with silica such as ilmenite in admixture with silica and alumina, high iron bauxite ores, and the red mud residues resulting from the alkaline extraction of bauxite ores, by calcining the raw charge material, preferably between 800 DEG C. and 1350 DEG C. and smelting the material with a carbonaceous reducing agent in an electric furnace, the ratio of alumina to silica being 1 to 3 moles of alumina to 3 to 2 moles of silica, thus obtaining molten iron, and a slag containing substantially all the titania, alumina, and silica. The smelting is preferably carried out in an electric arc furnace in which the electrode tips are adjusted so as to be from 1/2 inch above the top of the slag bath to 3 inches below the top of the slag bath. This prevents segregation of the components of the charge. Further it is advantageous to arrange the feed of solid down the sides of the furnace, so that the molten slag does not come into contact with the furnace walls. The metallic iron is separated, and the slag is digested with aqueous sulphuric acid, preferably of at least 60% concentration. A solution of aluminium and titanium sulphates, and an insoluble residue of silica is obtained. The residue is removed and the solution is first treated to obtain aluminium sulphate, which may be calcined to the oxide, and then for the recovery of titania. If there is any unreduced iron oxide in the slag, or if the titanium is present as the dioxide, which with sulphuric acid gives the oxysulphate, metallic aluminium is added to the solution in sulphuric acid to reduce the iron oxide to iron, which is precipitated, and to convert the oxysulphate to the sulphate. In a modification, the slag is digested with dilute sulphuric acid to form a solution of aluminium sulphate, and the residue of silica and titania is then treated with a more concentrated sulphuric acid to give a solution of titanium sulphate. The solutions are then separated, treated to recover aluminium sulphate which may be converted to alumina by calcining, preferably by heating to about 690 DEG C. and finishing at 1000-1100 DEG C., and titania by hydrolysis of the titanium sulphate solution.