GB827470A - Treatment of titanium dioxide ores - Google Patents

Abstract

Titanium dioxide ores containing iron oxide are heated in admixture with carbon in amounts sufficient to reduce substantially all the iron to elemental form but not in excess of that required to reduce both the iron oxide and all the titanium dioxide to titanium monoxide, at a temperature in the range 1100 DEG to 1600 DEG C., the temperature being a sintering temperature below that at which any of the constituents of the ore will coalesce to form a fluid slag. The sintering is continued in the absence of air and, <PICT:0827470/III/1> if necessary in a reducing atmosphere until all the carbon is oxidized and the resulting carbon monoxide removed and the ore residue is converted into a partially reduced carbon-free sintered mass in which the iron is present as elemental iron. The product may be crushed and mixed with a binder to form a steel welding rod but is preferably further treated to remove the iron contaminant to form an iron-free titania concentrate. If partial or complete reduction of the titania to lower oxide is desired the ore should be heated between 1300 DEG and 1600 DEG C. in an atmosphere of hydrogen and the amount of carbon should be sufficient to combine with the oxygen to be removed from the titania. Material containing such reduced titania values may be digested in sulphuric acid for the manufacture of titanium pigment. Alternatively the carbon-free sintered material may be chloridized with hydrogen chloride, chlorine or a mixture thereof at temperatures between 750 DEG to 1000 DEG C., thereby selectively chloridizing the iron which is removed as ferrous or ferric chloride. The latter may be treated as described in Specification 827,471 for the recovery of metallic iron and hydrogen chloride which may be recycled as chloridizing gas. The iron-free concentrate may be chlorinated, preferably in the presence of further added carbon, or it may be further reduced by mixing therewith carbon in an amount at least sufficient to reduce the titanium dioxide to a lower oxide and heating the mixture in a hydrogen atmosphere at a temperature between 1300 DEG and 1600 DEG C. The resulting residue may be dissolved in sulphuric acid for the production of titanium pigment or may be further chlorinated with, for example, phosgene, to produce titanium tetrachloride. Thus ilmenite may be mixed with lamp black or graphite in an amount sufficient to combine with the iron oxide and heated to a temperature of 1100 DEG to 1600 DEG C.; the partially reduced ore containing metallic iron is broken up and treated with hydrogen chloride at 750 DEG to 1000 DEG C. or with chlorine at 600 DEG to 1000 DEG C. to form iron chlorides. The preferred procedure is shown in the Figure where the titanium ore is reduced with carbon in the furnace 1 and passed into a reactor 2 where it is treated with chlorine, hydrogen chloride or a mixture thereof to form iron chloride and a titanium oxide concentrate. The evolved iron chloride passes to a condenser 5 maintained at 350 DEG to 650 DEG C. and the condensate is passed to an electrolytic cell 7 which contains a fused alkali metal chloride electrolyte through which is passed a stream of hydrogen from container 16 through the hollow anode 15. Metallic iron is deposited and a mixture of hydrogen chloride and excess hydrogen is removed from line 18. This is recirculated through line 3 to the chlorination reactor 2. Chlorine equivalent to the excess hydrogen may be supplied from container 22 to react in a gas burner type nozzle at 27. The system may be put into operation by supplying hydrogen and chlorine from sources 22 and 16.