1. Field of the Invention
This invention is in the field of smelting sulfidic ores utilizing a smelting cyclone to produce an enriched metal matte and a basic slag, the metal and slag being further treated by means of a plurality of lances which blow reducing gases onto the melt to form a metal-rich phase and a slag phase which is very low in the desired metal.
2. Description of the Prior Art
The treatment of fine-grained sulfidic ore concentrates by melting in an oxidizing atmosphere, and aftertreating the melt by means of blowing reducing gases thereon through a plurality of lances in the form of focused streams with high kinetic energy was described initially in German AS No. 29 22 189.
Until now, only as much sulfur was oxidized into sulfur dioxide in the oxidizing atmosphere of the smelting reactor as to produce a molten metal matte phase containing approximately 40 to 50% by weight of the metal to be recovered. In the case of sulfidic copper ore concentrate, the slag phase was converted by means of reduction into a copper-depleted slag of approximately 0.35% copper which could then be directly settled. The metal matte, for example, copper matte, must then be converted in a converter to blister copper. In the flash smelting method, the processing of sulfidic ore concentrate into a metal-enriched metal matte is beset with problems because in order to achieve the metal-enriched matte in the flash smelting reactor, more sulfide must be burned into sulfur dioxide with the result that the increasing amount of heat can no longer be diverted out of the reactor. Thus, the production of a high-grade metal matte containing, for example, 80% of the valuable metal content is only possible in a conventional, large smelting furnace. The use of a flash smelting method in combination with a flash smelting stack has only been previously proposed in references such as German AS No. 25 36 392. In that disclosure, a flash smelting stack having a capacity of only about 0.5 through 3 metric tons per hour was used, and that size is not suitable for industrial use.
A flash smelting stack with a height of a few meters provides additional furnace wall surfaces through which the heat of oxidation could be discharged. In a smelting cyclone with the same throughput power having a small volume in comparison thereto, the cooled wall surface area available is reduced to approximately one-tenth, that is, the specific thermal transmission coefficient is at least 10 times higher in the smelting cyclone than in the smelting stack. Therefore, it was not possible previously, by employing a smelting cyclone for melting sulfidic ore concentrate to produce a metal matte phase which exhibited a higher metal content than approximately 50%. The copper matte containing 72% copper achieved in the numerical example of German AS No. 29 22 189 relates to a smelting cyclone having a throughput which was not on an industrial scale.
A further difficulty in producing a metal matte phase with a high valuable metal content of, for example, 80% arises from the fact that the metal content in the slag increases noticeably at the same time so that the slag cannot readily be treated to recover the dissolved metal.
It is not feasible to enlarge a smelting cyclone at random in order to create larger cooled wall surfaces. This is because the cyclone eddy currents cannot be provided with the required high velocity and the danger exists that particles of ore concentrate will fall to the bottom of the cyclone unsmelted.