Smelting furnace, electric

Ore Size. The particle size of manganese ores is an important consideration for the smelting furnace. In general, the ore size for the furnace charge is —75 mm with a limit to the amount of fines (—6 mm) allowed. Neither electric furnaces nor blast furnaces operate satisfactorily when excessive amounts of fines are in the charge. 

Reduction to Liquid Metal. Reduction to Hquid metal is the most common metal reduction process. It is preferred for metals of moderate melting point and low vapor pressure. Because most metallic compounds are fairly insoluble in molten metals, the separation of the Hquified metal from a sohd residue or from another Hquid phase of different density is usually complete and relatively simple. Because the product is in condensed form, the throughput per unit volume of reactor is high, and the number and si2e of the units is rninimi2ed. The common furnaces for production of Hquid metals are the blast furnace, the reverberatory furnace, the converter, the flash smelting furnace, and the electric-arc furnace (see Furnaces, electric). 

Recovery of copper metal and alloys from copper-bearing scrap metal and smelting residues requires preparation of the scrap (e.g., removal of insulation) prior to feeding into the primary process. Electric arc furnaces using scrap as feed are also common. 

Charcoal is used in electrically heated furnaces to smelt specialty metals such as ferrosilicon. It is a preferred household fuel in developing countries with adequate forest resources. In the United States 95 percent of charcoal use is for barbecuing, while in Japan and Europe charcoal use is split evenly between cooking and industrial needs. 

The emission problem associated with the reverberatory smelting may be solved by electric furnace smelting. In the electric smelting process the quantity of effluent gas can be rather small and the sulfur dioxide concentration can readily be controlled by adjusting the air entrainment into the electric furnace. 

The technology for the production of titania slag by direct reduction smelting in electric arc furnaces (particularly for smelting of iron titanates and ilmenites having lower amounts of titania) is very old and the process has been in vogue in Canada, Norway, South Africa,... 

Tetronics A process for treating dusts from electrical arc furnaces for making steel and nonferrous metals. Volatile metals (zinc, lead, cadmium) are recovered, and residual slag is nontoxic and suitable for landfill. The dusts, mixed with coal dust and a flux, are fed to a furnace heated by a plasma gun. The metal oxides present are selectively reduced and the vapors of zinc, lead, and cadmium are condensed in a modified Imperial Smelting furnace. Developed by Tetronics Research Development Company, United Kingdom, and first commercialized for steel dusts at Florida Steel, Jackson, TN, in 1989. Seven plants were operating in several countries in 1992. 

Tin is produced from oxide by heating at high temperatures with carbon. Small amounts of limestone and sand are added to coal for this reduction and to promote removal of impurities. Primary smelting is carried out in a rever-baratory furnace at a temperature between 1,200 to 1,300°C. Electric arc furnaces also are used. The molten tin collected at the bottom is cast into slabs. The slags are resmelted at a higher temperature, up to 1,480°, in the same type of furnaces to recover more tin that is combined as silicates. 

For arc furnace worker safety, high power electrical systems require proper design and precautions, and handling of molten materials requires a minimum of fire-retardant clothing and often dust masks. Water must be prevented from coming in contact with the melt. Furthermore, since open-arc furnace noise levels commonly exceed 100 dB A, hearing protection is a necessity. Noise is normally not a problem with smelting furnaces. 

The alloys have been smelted in an electric arc furnace with a permanent tungsten electrode on the copper water-cooled bottom. The bottom has holes in which the batch is alloyed from different components. 

The alloy has been smelted in an electric arc furnace (mass of an ingot 100 g). 

Iridium-rhodium alloys were prepared in electric arc furnace in argon atmosphere by smelting refined powders of rhodium and iridium of 99.95 mass% purity. The composition of the alloys was controlled by the atomic adsorption analysis using the Perkin-Elmer spectrophotometer with HUS-72 analyzer. X-ray phase analysis indicated that all binary systems had a single-phase FCC-structure characteristic of... 

Part of the raw material mixture evaporates during smelting fluoride (as hydrogen fluoride, silicon and boron fluorides) and nitrogen oxides are formed in addition to water and carbon dioxide. Effective scrubbing of the flue gases is therefore necessary, which is easier with an electrically heated furnace than with a gas-heated one. 

The first patent for the use of chromium in steel was granted in 1865 - but the large-scale use of chromium had to wait until chromium metal could be produced by the alumino-thermic route, developed in the early 1900s and when the electric arc furnace could smelt chromite into the master alloy, ferrochromium. 

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