Subject smelting

There are no fumes or effluents generated in the processing of powders and the requirements of state and federal environmental protection agencies are met without difficulty. However, the production of powders has been subjected to the same concerns as most other metal refining and smelting operations. 

One case study was identified where a man who had been occupationally exposed to hexachloroethane was treated for a liver tumor (Selden et al. 1989). Exposure had occurred over a period of 6 years as a result of the presence of hexachloroethane in a degassing agent used during aluminum smelting. However, the hexachloroethane reacted at the 700 C use-temperature, releasing a gas that was 96% hexachlorobenzene with small amounts of other chlorinated compounds. Because there was occupational exposure to a mixture of chlorinated compounds rather than just hexachloroethane, it is highly unlikely that the tumor was the result of hexachloroethane exposure alone. Occupational exposure to mineral oil mists for 20 years was also part of the subject s employment history. 

Smelting the Ores.—The next operation is the smelting or reduction of the calcined ore, and the first subject which falls to he considered under this head is the form and materiel of the furnace. 

The nature and qualities of different kinds of fuel have been ftilly discussed in a separate article devoted to that subject, to which the reader is referred for" some important information in conncc--tion- with Its application to the smelting of iron ores. It >s of the utmost importance that the... 

Smelting in Blast Furnaces.—The use of the blast furnace involves the necessity of a somewhat different treatment. The Scotch furnace or ore-hearth, described at page 465, may be taken as the type of this kind of furnace when adapted to the smelting of lead ores. Generally very rich ores are operated upon where the Scotch furnace is employed end these are subjected before smelting to a preliminary roasting in a furnace of the reverberatory class,... 

The ore which is oooaBionally treated in the Scotch furnace, when it contains much carbonate of lead, is not subjected to a previous roasting, but at once sub- mitted to the smelting operations dcsoribod. 

Smelting. After an ore has been subjected to an appropriate treatment as outlined here—or, as is sometimes possible, without any pretreatment—the ore is subjected to a process known as smelting. It is in this procedure that the metal is actually obtained in the elemental condition. Although the details differ considerably among the many metallurgical processes in everyday use, the overall characteristics usually conform to one of the following general methods. 

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