GB776602A - Process for the recovery of tin or tin dioxide from materials containing tin in an oxidic form - Google Patents

Abstract

Stannic oxide is recovered from materials containing tin in oxidic form such as slag, ores and concentrates, by reducing said material at above 1100 DEG C. e.g. 1300-1600 DEG C. with a reducing gas having an oxygen pressure corresponding to that of a mixture of CO and CO2 containing more than 35 per cent, preferably 50-80 per cent by volume of CO and converting the gaseous stannous oxide so obtained into stannic oxide, e.g. by oxidation with air or CO2 at or above the temperature of formation. Suitable reducing gases are carbon monoxide, a mixture thereof with carbon dioxide, hydrogen, water gas and producer gas. Alternatively tin can be obtained from the stannous oxide (see Group II abridgement). It is preferred to use an initial gas with an oxygen pressure corresponding to that of a CO/CO2 mixture containing at least 80 per cent of CO, and when formation of gaseous stannous oxide decreases or is about to decrease, either to reduce the reducing component of the gas in one or more stages (each being dependent on a prior decrease in stannous oxide formation), and/or to add further oxidic material.ALSO:Tin is recovered from materials containing tin in oxidic form such as slags, ores and concentrates, by reducing said material at above 1100 DEG C, e.g. 1300-1600 DEG C. with a reducing gas having an oxygen pressure corresponding to that of a mixture of CO and CO2 containing more than 35 per cent, preferably 50-80 per cent by volume of CO and converting the soformed gaseous stannous oxide to tin, e.g. by cooling the vapours and/or introducing them into a reducing atmosphere containing more CO or other reducing gas than that in which the stannous oxide was formed. Suitable gases for the initial reduction of oxidic materials are carbon monoxide, a mixture thereof with carbon dioxide, hydrogen, water gas and producer gas. Alternatively stannic oxide can be obtained from the stannous oxide (see Group III abridgement). It is preferred to use an initial gas with an oxygen pressure corresponding to that of a CO/CO2 mixture containing at least 80 per cent of CO, and when formation of gaseous stannous oxide decreases or is about to decrease, either to reduce the reducing component of the gas in one or more stages (each being dependent on a prior decrease in stannous oxide formation), and-or to add further oxidic material.