What is direct smelting of sulfide ore? What are the advantages and disadvantages of direct smelting compared with traditional methods?

A smelting method for producing metal by directly smelting sulfide concentrate without roasting or sintering roasting. When nonferrous metal sulfide ore or concentrate is smelted into metal, it needs to be desulfurized, and there is a problem of acid production or sulfur dioxide pollution. Copper sulfide concentrate is made into matte by matte melting, and then blown into coarse copper. Sulphur dioxide will be produced by matte smelting and blowing. Although sulfur dioxide is mostly used to make acid in copper smelting, the pollution problem is basically solved, but copper-lead-zinc and copper-zinc complex sulfide mine accidents are treated by matte smelting. Zinc sulfide concentrate is first desulfurized by boiling roasting to produce acid, and metallic zinc is roasted and refined by wet method or fire method; It is also difficult to treat copper-zinc, lead-zinc and copper-lead-zinc complex sulfide ores. The lead sulfide concentrate is firstly sintered, roasted and desulfurized by a sintering pot or a belt sintering machine, and the sintered block is reduced and smelted into crude lead by a blast furnace; The antimony sulfide concentrate is volatilized and smelted into coarse antimony oxide in blast furnace or open hearth furnace, and then reduced and smelted into coarse antimony in reverberatory furnace; The lead-antimony complex sulfide ore concentrate is first roasted in a fluidized bed furnace, sintered and desulfurized in a sintering disc, and then reduced and smelted in a blast furnace to form a lead-antimony alloy. Both lead-antimony single sulfide ore and lead-antimony complex sulfide ore concentrate smelting have the problem that a large amount of low-concentration sulfur dioxide flue gas can not produce acid and pollute the environment, which is an important pollution source of acid rain. Daye refinery, antimony plant and lead-antimony smelter using sintering machine all participated in the treatment of sulfur dioxide pollution. The oldest direct smelting method of sulfide ore without sulfur dioxide emission is precipitation smelting of antimony sulfide ore and bismuth sulfide ore, but the displacement agent used in precipitation smelting is metallic iron or iron filings, which has high cost and poor technical and economic indicators and is not suitable for smelting lead sulfide concentrate and various complex sulfide concentrates. Patent application 94119758.1put forward "the technology of smelting sulfide ore directly to make metal". The sulfur-fixing agent proposed in this patent application is oxides, hydroxides or carbonates of manganese, iron, calcium and magnesium, and the concept is not clear and specific. If it is regarded as a pure substance, the cost is high and the source is not easy, and the treatment object is limited to zinc, copper and carbonate.