Pyrometallurgical processing

Pyrometallurgical Processes Such high temperature processes convert certain minerals into others for easier separation from gangue or for easier recovery of metal. They are accomplished in Idlns, hearth furnaces or fluidized bed reactors. 

Kinetic data available for the reactions of other metal sulphates refer to reaction conditions closer to those of actual pyrometallurgical processes [790]. 

Many reactions among solids are important with regard to pyrometallurgical processes. While some of these reactions are true solid-solid reactions, some others occur through fluid intermediates. For instance, the carbothermic reduction of many metal oxides proceeds through the gaseous intermediates CO and C02 in the following manner ... 

Aluminothermic reduction is one among the few pyrometallurgical processes where the actual process closely follows the route theoretically predicted from thermodynamic data. This characteristic, coupled with the simplicity associated with the whole process, makes it well suited for demonstration experiments. The reduction of magnetite by aluminum is a suitable example in this context. 

Tin slags account for a sizeable fraction of the world s tantalum production. These slags are melted in electric arc furnaces, together with coke and lime (as flux), and this pyrometallurgical process leads to the production of synthetic niobium/tantalum concentrates. The waste products of this operation are mechanically separated slags which can be used, for instance, as landfill. The exhaust gases from this process are of minor consequence if dust is eliminated by the use of filters. 

Onsite processing using hydrometallurgical or pyrometallurgical processes to upgrade the zinc values to zinc oxide or metallic zinc... 

Copper conversion is accomplished by a pyrometallurgical process known as smelting. During smelting the concentrates are dried and fed into one of several different types of furnaces. There the sulfide minerals are partially oxidized and melted to yield a layer of matte, a mixed copper-iron sulfide, and slag, an upper layer of waste. 

Peacey, J. G. Hancock, P. J. Review of pyrometallurgical processes for treating iron residues from electrolytic zinc plants. Iron Control and Disposal, Proceedings of the International Symposium on Iron Control in Hydrometallurgy, 2nd, Ottawa, Oct. 20-23, 1996, 17-35. 

Hara, S., and Ogino, K., Slag-Foaming Phenomena in Pyrometallurgical Processes, ISIJ Int., 32 81 (1992)... 

Dwight-Lloyd A pyrometallurgical process for simultaneously roasting and smelting a ground ore. The ore is contained in a series of shallow iron boxes with perforated bases which are drawn continuously through a furnace having a downward draft of air. Developed by... 

Preparation. Sulphides are readily converted to oxide by roasting in air, that remove all sulphur as S02 this pre-treatment is followed by pyrometallurgical process by heating with carbon, or electrolytic process to obtain zinc. It is also possible by controlled oxidation to convert ZnS to the water soluble ZnS04, which can be extracted and electrolyzed to produce zinc. Crude zinc obtained by pyrometallurgical process can be refined by distillation taking into account the comparatively low boiling temperature of zinc. 

Sulfide ores are processed by a number of pyrometallurgical processes roasting, smelting, and converting. During these processes, sulfur and iron are removed to deld a sulfur-deficient copper-nickel matte. Especially after roasting and converting, the nickel in the matte may consist primarily of nickel subsulfide. After physical separation of the copper and nickel sulfides, the nickel is refined electrochemically or by the carbonyl process. The treatment of the matte depends on the end use of the nickel. Alternatively, the sulfide can be roasted to form a nickel oxide sinter that is used directly in steel production. 

The method incorporates experience from industrial pyrometallurgical processes. 

The TERRAMET process is specifically matched to the soil type, contaminant addressed, and metals concentration of the soil based on results of treatability tests. The presence of surfactants can hinder operations. High levels of carbonates or oxides can cause excessive leachate consumption or foaming. Processing soils with metal concentrations in excess of 100,000 parts per million (ppm) (10% by weight) may be best accomplished with direct pyrometallurgical processing, which is often more cost effective for soils with substantially higher heavy metals content. 

Direct pyrometallurgical processing of heavy-metals-contaminated soils, sands, and dust is often better suited for materials with higher levels of contamination however, it can be effective for low-level contamination as well. The technology is also well suited to process-concentrated heavy metals that have been generated by on-site screening or soil washing (personal communication, M. Thomas, The Doe Run Company, 10/97). 

Lead sulphide (galena - PbS) is another likely candidate for hydrometallurgical processing particularly in the United States where, apart from the problems of the sulphur dioxide emissions, the lead toxicity problem is making it very difficult for the lead smelters to operate their conventional pyrometallurgical process and comply with EPA and OSHA standards. The total amount of lead mined in the United States is about 600,000 tons per year which, if fully converted, would yield about 100,000 tons per year of by-product sulphur. The Bureau of Mines in Reno, Nevada, have an active pilot plant study to produce lead via a hydrometal-lurigal process (2). In this process the common lead mineral galena is dissolved in an acid brine solution of ferric chloride. 

A more recently developed pyrometallurgical process is that of the proposed integral fast reactor, which would use metallic fuel (U—Pu—Zr alloy) and a molten salt electrorefiner as follows ... 

Processes for extracting metals from their ores are generally classified as pyrometallurgical, if high temperatures are used, or hydrometallurgi-cal, if aqueous solutions are used. Copper is extracted by both methods. In the pyrometallurgical process for the extraction of copper, the enriched ore is roasted, or heated in air ... 

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