Smelting

The reduction smelting process involves the reduction of oxidic sources of metals with carbon in the presence of a flux. The process can generally be represented as  

The blast furnace is the most popular of the furnaces used for carrying out reduction smelting operations. An illustrious example of a blast furnace smelting product is iron. 

The reverberatory furnace smelting, on the other hand, is reserved particularly for those situations where reducing conditions are either not necessary or are not desirable. 

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 conversion process for the copper matte removes iron, sulfur and other impurities from matte, thereby yielding liquid metallic copper of about 99% purity (blister copper). The slags which come out of converters contain from 2 to 15% copper and must go through treatment for copper recovery, usually by froth flotation of the copper from solidified and slowly cooled slag. 

Limestone is widely used as a flux in the smelting of copper, lead, zinc and antimony from their ores. It is charged into the smelters with the concentrated ores. The limestone calcines and the resulting lime reacts with silica, alumina and other impurities to form a molten slag. The slag chemistry is similar to that in the blast furnace (section 11.1.3). 

The limestone should be high in calcium carbonate and low in silica and alumina. As with limestones for use in blast furnaces, it should be resistant to decrepitation on heating and produce lime which is strong enough to resist crushing in the smelter. 

Carbon monoxide reacts with combined metal in the ore and reduces it into uncombined molten metal. Smelting iron, for example, proceeds by the conversion of iron oxide, in the ore, to uncombined iron metal  

Most smelting processes (see Fig. 33) result in the formation, in the smelting furnace, of a two-layer melt a dense layer of molten crude (impure) metal at the bottom and a lighter layer of waste, the slag, forming a scum on top. After the furnace cools down and the products of the smelting process solidify, the slag is removed and discarded. The crude metal can then be used as such, or it may be further refined (Tylecote 1992 Bachmann 1982). 

FIGURE 33 Smelting flowchart. The chart shows, in diagrammatic form, the sequence of metallurgical processes required for extracting metals from their ores from the initial mining of metalliferous ores to the final refining of the smelt metals. 

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An additive assisting in fusion - e.g. CaCOj in iron-smelting - although the limestone also helps with slag formation. 

Of our special interest is the thickness measurement of powder coatings. While the sound velocity of the electrostatic applied powder/air mixture is estimated to be two times the velocity in air it is also an estimation that thickness powder / air layer is reduced by a factor of 5 by smelting (burning in process, hardening). 

The process of extraction requires first smelting (to obtain the crude metal) and then refining. In smelting, iron ore (usually an oxide) is mixed with coke and limestone and heated, and hot air (often enriched with oxygen) is blown in from beneath (in a blast furnace). At the lower, hotter part of the furnace, carbon monoxide is produced and this is the essential reducing agent. The reduction reactions occurring may be represented for simplicity as ... 

For example, from Imperial Smelting Corporation. 37. Dover Street, London. W.l, or from The ilatheaon Company, East Rutherford, N.J., U.S.A. 

Large copper ore deposits are found in the U.S., Chile, Zambia, Zaire, Peru, and Canada. The most important copper ores are the sulfides, the oxides, and carbonates. From these, copper is obtained by smelting, leaching, and by electrolysis. 

Selenium is found in a few rare minerals such as crooksite and clausthalite. In years past it has been obtained from flue dusts remaining from processing copper sulfide ores, but the anode metal from electrolytic copper refineries now provide the source of most of the world s selenium. Selenium is recovered by roasting the muds with soda or sulfuric acid, or by smelting them with soda and niter. 

Thallium occurs in crooksite, lorandite, and hutchinsonite. It is also present in pyrites and is recovered from the roasting of this ore in connection with the production of sulfuric acid. It is also obtained from the smelting of lead and zinc ores. Extraction is somewhat complex and depends on the source of the thallium. Manganese nodules, found on the ocean floor, contain thallium. 

The focus of this section is the emission of ultraviolet and visible radiation following thermal or electrical excitation of atoms. Atomic emission spectroscopy has a long history. Qualitative applications based on the color of flames were used in the smelting of ores as early as 1550 and were more fully developed around 1830 with the observation of atomic spectra generated by flame emission and spark emission.Quantitative applications based on the atomic emission from electrical sparks were developed by Norman Lockyer (1836-1920) in the early 1870s, and quantitative applications based on flame emission were pioneered by IT. G. Lunde-gardh in 1930. Atomic emission based on emission from a plasma was introduced in 1964. 

Smelling salts Smell receptors Smelters Smelting... 

Precipitators are currently used for high collection efficiency on fine particles. The use of electric discharge to suppress smoke was suggested in 1828. The principle was rediscovered in 1850, and independently in 1886 and attempts were made to apply it commercially at the Dee Bank Lead Works in Great Britain. The installation was not considered a success, probably because of the cmde electrostatic generators of the day. No further developments occurred until 1906 when Frederick Gardiner Cottrell at the University of California revived interest (U.S. Pat. 895,729) in 1908. The first practical demonstration of a Cottrell precipitator occurred in a contact sulfuric acid plant at the Du Pont Hercules Works, Pinole, California, about 1907. A second installation was made at Vallejo Junction, California, for the Selby Smelting and Lead Company. 

Total 1991 world production of sulfur in all forms was 55.6 x 10 t. The largest proportion of this production (41.7%) was obtained by removal of sulfur compounds from petroleum and natural gas (see Sulfurremoval and recovery). Deep mining of elemental sulfur deposits by the Frasch hot water process accounted for 16.9% of world production mining of elemental deposits by other methods accounted for 5.0%. Sulfur was also produced by roasting iron pyrites (17.6%) and as a by-product of the smelting of nonferrous ores (14.0%). The remaining 4.8% was produced from unspecified sources. 

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