GB394539A - Roasting pyrites fines - Google Patents

Abstract

<PICT:0394539/III/1> Finely divided pyrites, marcasite, chalcopyrites, and like sulphide ores are heated to distil off their volatile sulphur and are then roasted with air or oxygen while in gaseous suspension to produce sulphur dioxide and metal oxides. Sintering is thereby avoided. The distillation may also take place with the pyrites &c. in suspension in a hot gaseous medium. The hot gases from the roasting operation may be utilized in the distillation. Pyrites fines or flotation concentrates are fed from a hopper 2 through a screw conveyer 3 and inlet duct 4 into a distillation chamber 1 where they are distilled while in suspension in hot sulphur dioxide gases which enter through tuyeres 6, 7 leading from feed pipes 8, 9. The resulting iron monosulphide is passed by a screw conveyer 16 into a roasting chamber 5 where it is roasted in suspension by means of air or oxygen, if desired preheated, which enters via tuyeres 18. The iron oxide Fe2O3 or Fe3O4 is removed by a screw conveyer 20. The hot sulphur dioxide gases pass to the distillation chamber through a duct 10 and the hot gases containing sulphur dioxide and sulphur leave through an exit duct 14. The heat of these gases may be used to preheat the air or the pyrites. The pyrites in the distillation chamber should be heated to 500-800 DEG C. which is low enough to prevent sintering. The temperature of the upper part of the roasting chamber should not exceed the fusing temperature of iron monosulphide, i.e. 850-900 DEG C. In the lower part of the roasting chamber the temperature may be up to 1400 DEG C. The process may be initiated by preheating the roasting chamber with oil burners or by preheating the distillation chamber electrically. The gases containing sulphur dioxide and sulphur may be burnt to convert the whole of their sulphur content into sulphur dioxide or may be treated with carbonaceous reducing agents such as producer gas, water gas, natural gas, solid carbon and the like or with hydrogen sulphide to convert their whole sulphur content into elementary sulphur.