Smelting and Refining

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. 

The refining process generally entails either the volatilization or the controlled oxidahon of the impurities. 

Some impurities are converted into gases that are then released from the hot molten metal others are oxidized (converted into oxides), making up slag, the layer of useless matter on the upper surface of the molten, refined metal, from where it is removed. 

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The most significant occupational exposures to zinc would occur during the smelting and refining of zinc ore. The standards for occupational exposure have been estabUshed at a level to prevent the onset of metal fume fever. This temporary condition is caused by excessive exposure to freshly formed fumes of zinc oxide and results in flulike symptoms of fever, chills, headache, muscle pain, nausea and vomiting. 

By-Product and Secondary Antimony. Antimony is often found associated with lead ores. The smelting and refining of these ores yield antimony-hearing flue, baghouse, and CottreH dusts, drosses, and slags. These materials may be treated to recover elemental antimony or antimonial lead from which antimony oxide or sodium antimonate may be produced. 

Most copper is processed using a combination of mining, concentrating, smelting, and refining, or by leaching waste and solvent... 

Scra.p Copper. The energy required for copper production from scrap is appreciably less than that needed production from ores. If the scrap is of low grade and has to be smelted and refined, the energy consumption is about 45 GJ /1 (43 x 10 Btu/t) of copper (52). Scrap that only requires melting and casting uses about 5 GJ/t (4.7 X 10 Btu/t) of copper. 

Some fugitive particulate emissions occur around copper mines, concentrating, and smelting facilities, but the greatest concern is with emissions from the ore preparation, smelting, and refining processes. Table 30-9 gives the emissions of SO2 from the smelters. 

Primary smelting and refining of copper 3334 Primary production of aluminum 3339 Primary smelting and refining of nonferrous metals, except copper and aluminum 3341 Secondary smelting and refining of nonferrous metals... 

The SIC code of the battery plant is 3691 (storage batteries) the SIC code for the smelter is 3341 (secondary smelting and refining of non-ferrous metals). A lead oxide production plant located adjacent to the battery plant, on the same property, also falls under SIC code 3691. 

A nonprofit international association of companies engaged in the mining, smelting and refining of bismuth. 

Seeondary smelting and refining and alloying of nonferrous metals and alloys 3341... 

Tables 3.39 and 3.40 illustrate TRI releases and transfers for the primary nonferrous metals smelting and refining industry. For this industry as a whole, chlorine comprises the largest number of TRI releases. This is reflected in the fact that chlorine is a byproduct of the magnesium industry and the largest reporter is a magnesium facility. The other top releases are copper compounds, zinc compounds, lead compounds, and sulfuric acid.

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