GB816609A - Improvements relating to the recovery of vanadium from slag - Google Patents

Abstract

Vanadium is recovered from slag produced in the manufacture of iron and steel by dissolving the slag in aqueous hydrochloric acid, evaporating the resultant chloride solution to dryness and distilling the dried residue in the presence of hydrogen chloride gas at up to 400 DEG C. The slag may be fed with hot 30 per cent HCl to a rotary kiln maintained at 95 DEG C. to form the chloride solution. Scrap iron or shot may, if desired, be present to prevent formation of ferric chloride rather than ferrous chloride. This solution which may contain silica in suspension and chlorides of iron, manganese, vanadium, aluminium, titanium, calcium and magnesium, may then be filtered, and evaporated in one or more steps, e.g. by partial evaporation in a steam-heated evaporator followed by spraying into hot combustion gases or a bed of hot fluidized solids, or by partial evaporation by submerged combustion followed by crystallization, filtration, the return of the mother liquor to the crystallization tank and drying of the crystals, e.g. in a steam-heated rotary drier. Drying may be carried out in the presence of hydrogen chloride gas as in Specification 734,081, to avoid hydrolysis, especially of iron chlorides. Aluminium and titanium chlorides are easily hydrolysed to oxide during the drying. The dried residue may then be crushed and fluidized in a stream of preheated hydrogen chloride to distil off the ferric and vanadium chlorides (the latter may be distilled as vanadyl chloride). The mixed gases may be separated as described in Specification 737,889. In one case, the chlorides were condensed, and after acid scrubbing of the gases leaving the condenser to recover remaining vanadium chloride, the condensate and scrubbing liquor were evaporated and roasted to recover vandium pentoxide. The residual ferrous, manganous and calcium chlorides may be hydrolysed as a fluidized bed in steam in two stages, the first at 350-400 DEG C. to yield ferric oxide, the second at 500-550 DEG C. with the addition of siliceous material, if desired, to yield manganese and calcium oxides, the manganese and calcium chlorides being water-leached from the ferric oxide and the so-formed solution dried between the two stages. The Provisional Specification is not restricted to the treatment of slags, or to final distillation but refers also to treating materials which will not respond to gaseous chloridizing below 400 DEG C. and in particular to treating ilmenite to obtain ferric chloride and leave (after the above described distillation or after leaching the dried residue with water) a residue of titanium dioxide formed as a result of hydrolysis during evaporation and drying. If so desired, the iron may be oxidized during drying to the ferric state by addition of an oxidizing component to the heating gases or heating may be continued to form ferric oxide or during distillation air or oxygen may be added to the hydrogen chloride employed. It is stated that the iron may be present in the dried residue as the oxychloride. Specification 701,797 also is referred to in the Provisional Specification.