Processes for roasting or roasting and smelting of materials containing sulphide of iron

摘要

505,631. Treating ores. HAGLUND, T. R. Nov. 12, 1937, No. 31077. Convention date, Nov. 12, 1936. [Class 82 (i)] [Also in Group III] Materials containing sulphide or iron, e.g. mattes, flotation concentrates comprising pyrites or pyrrhotite, &c., are reacted in suspension with sulphur dioxide at a temperature above the melting point of the sulphide whereby to produce iron oxide which is collected in solid state or as a molten bath. Thus, the finely divided sulphide material may be dispersed in a stream of oxidizing gas, preferably oxygen or oxygen-enriched air, the amount of oxygen supplied being sufficient for oxidation of only part of the sulphur of the sulphide, and then in the absence of free oxygen, the sulphur dioxide formed or previously contained in the gas is reacted with the molten sulphide. Melting of the sulphide may be started by the heat of oxidation of the part of the sulphur, but the oxidizing gas and the sulphide material are preferably preheated, and the temperature may also be regulated by burning powdered coal, sulphur, carbon-monoxide, producer or fuel gas &c. When the sulphur dioxide reacting with the sulphide is produced separately outside the reaction tower, it and the sulphide material must be preheated. As more particularly described, crushed pyrites or pyrrhotite and additional combustible material are injected with the oxidizing gas into the furnace. When the iron oxide is to be collected as a molten bath, the burners are preferably directed at a right or oblique angle thereto, or at the furnace wall near to the bath. The fused iron oxide may be granulated by air, or alternatively after cooling, may be sintered. If the bath contains, say, nickel or copper sulphides, it is allowed to solidify, crushed, and subjected to flotation. If the more valuable ores contain silica, slagproducing additions e.g. quartz, lime, fluorspar may be added to the bath or to the ore, whereby the more valuable sulphides are easily separated in matte form. If the ore contains considerable amounts of sulphides of, say, copper and nickel, the roasting is adjusted so that incomplete oxidation of the iron sulphide occurs. The matte of iron, copper, nickel, &c. so formed, is crushed and subjected in the above described manner to incomplete roasting in combination with smelting. When the process is effected so that the roasted ore is collected in a pulverulent state, the roasting may be effected so that the pulverulent material contains iron sulphide; the material is then smelted for the recovery of the more valuable metals as a matte.