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Production

Titaniferous magnetites

Vanadium from the magnetite ores of Russia and China and a large proportion of the vanadium from the magnetite ore in South Africa, is extracted as a co-product with iron which is converted to steel. In China and Russia the iron is produced in a blast furnace but in South Africa because of the high titanium content of the ore, the iron is produced by a process involving the pre-reduction of the magnetite with powdered coal in a rotary kiln followed by reduction in a submerged arc electric furnace.

The iron from these operations contains about 1.5% vanadium which is removed as slag by low temperature treatment with oxygen. In China this is carried out by spray refining, while in South Africa it is done in a shaking ladle and in Russia a special oxygen steel converter is used.

The slag from South Africa contains up to 25% V2O5 whereas the slag from China and Russia contains between 12 and 20%. The V2O5 is extracted from the slags by a roast-leach process in which the slags are roasted in kilns or in multi-hearth furnaces with sodium carbonate, chloride or sulphate (or lime in Russia). This produces sodium vanadates which are leached out with water. Ammonium vanadates are precipitated from this solution by addition of ammonia and sulphuric acid to control the pH. The ammonia is removed and the vanadate converted to various oxides by heating under controlled conditions which are varied according to the oxide required. The oxides are used for the production of ferrovanadium and vanadium-aluminium alloys required for the addition of vanadium to steel and titanium respectively. The ammonium vanadate forms the basis for the production of vanadium chemicals.

A large proportion of the slag produced in South Africa is converted to vanadium oxide in South Africa and Europe. Some South African slag is converted to ferrovanadium. Magnetite in South Africa is also treated directly for the production of vanadium oxides by the roast-leach process.

Uranium ores of Colorado

Vanadium from the Colorado ore is extracted as a co-product with uranium at a plant in Utah. The ore is treated with sulphuric acid to dissolve the vanadium and uranium. The uranium and vanadium are separated from the liquid by solvent extraction followed by a liquid-liquid ion exchange process which separates the uranium leaving the vanadium in the acid solution. This is subsequently oxidised and removed from the organic salts with soda ash. Vanadium polyvanadate is precipitated by the addition ammonium sulphate.

Caribbean and other oils containing Vanadium

Vanadium, from oils in which it is present, is obtained by various routes.

1. It is present in the coke produced in the Flexicoke process used in Venezuela for the upgrading of heavy crude oils. The coke from this process is treated with sulphuric acid and the resulting solution with an ion exchange reaction in which ammonium vanadates are precipitated.
2. The fuels are burnt in the boilers of electric power generating plant and vanadium is left in the fly and boiler ashes. Vanadium in these ashes is recovered by the same process as for vanadium coming from Flexicoke. Vanadium is also recovered from the ashes after concentration by adding to the feed of furnaces in which slag is converted to ferrovanadium by silicon reduction.
3. Spent nickel-molybdenum and cobalt-molybdenum catalysts are treated by chemical processes to separate the vanadium from molybdenum, cobalt and nickel to convert the vanadium to oxides.

Iron sands

Slag produced from a steel plant treating iron sands in New Zealand is exported for conversion to oxides.

Production of Ferrovanadium and Aluminium-vanadium

Vanadium, like most other alloys is added to steel as a ferroalloy. Ferrovanadium is available in alloys containing 40, 60 or 80% vanadium. the 60 and 80% grades are mostly produced by the aluminothermic reduction of vanadium oxides in the presence of steel scrap or by direct reduction in an electric furnace. The 40% grade is produced from slag and other vanadium products by the silicon reduction process.

Vanadium additions to titanium alloys are made with aluminium-vanadium master alloys which are also produced by aluminothermic reduction of vanadium oxides followed by vacuum refining.