Metallurgical Uses

Commercial primary magnesium has a typical purity of 99.8%, which is sufficient for most chemical and metallurgical uses. A typical analysis might be expected to show about 0.003% each of aluminum and copper, 0.04% iron, 0.08% manganese, 0.001% nickel, and 0.005% siHcon. Primary magnesium is available in five grades (Table 3). Considerably higher purity can be obtained by distillation. 

Until 1960—1970, in countries where natural gas was not available, large amounts of coal were carbonized for the production of town gas, as well as a grade of coke which, although unsuitable for metallurgical use, was satisfactory as a domestic fuel in closed stoves. The early cast-iron and siUca horizontal retorts used at gasworks were replaced by continuous vertical retorts. These operated at flue temperatures of 1000—1100°C. The volatile products were rapidly swept from the retort by the introduction of steam at 10—20% by weight of the coal carbonized. 

Other uses in terms of production. In terms of value, the proportions were 50%, 47%, and 3%, respectively, for metallurgical uses, abrasives, and refractories and other uses. 

Figure 25. Evolution of commercial consumption of contained REMs in iron and steel starting in 1967 and projecting tentatively through 1985. Other metallurgical uses of mischmetal and RES are not included but amount to no more than 15% of the totals of the graphs.

Limestones vary greatly in color and texture, the latter ranging front dense and hard limestone, e.g.. marble or travertine, which can be suwed and polished, to soft, friable forms, e.g., chalk and marl. Chalk is a very fine-grained white limestone, while marl is an impure deposition product that contains clay and sand. Texture, hardness, and porosity appear to be functions of the degree of cementation and consolidation during the formation of these materials. Color variations arise from the presence of impurities. Some impurities, such as sulfur and phosphorus, make limestone unattractive for metallurgical uses. 

Rhenium alkoxocomplexes are of interest as homogeneous catalysts of olefine metathesis [519], They have also been used for the preparation of fine powders ofrhenium and rhenium alloys for catalytical and powder metallurgical use [1452]. 

Refractory metals such as titanium and zirconium can be won from their oxides by reduction with metals which have oxides with a high heat of formation. Of these, only calcium (or calcium hydride) is capable of producing refractory metals in purities approaching those required for metallurgical uses. 

Sulfur Content. Another important feedstock physical property related to delayed coking is the sulfur content. The sulfur present in the feedstock tends to concentrate in the coke, where the sulfur level is usually equal to or higher than that of the feedstock. Sulfur levels as high as 4 weight % in today s feedstocks can cause unacceptably high levels of sulfur in the coke product. The resulting coke may not be acceptable for metallurgical use and may be a problem when burned as fuel. 

The estimation of the world production of tellurium is difficult, since the two major producers do not publish production figures. The worldwide consumption in 2002 is estimated as 220 tonnes. It has slightly reduced over die recent years. Metallurgical uses dominate tellurium demand. In 2002, about 60% of tellurium was used as an alloying element to improve the properties of copper, iron, lead, and steel. Other uses include catalysts and chemicals (25%), photoreceptors and thermoelectric devices (8%), and miscellaneous minor uses %) ... 

Carbon brick is currently manufactured in the western hemisphere by only one company and the greatest volume of its product goes into steel mills and into other metallurgical uses. (At the time of this writing one other manufacturer has started production of an acceptable carbon brick.) Because it is employed primarily in refractory service, it has always been manufactured in refractory sizes-in the 9" X 4.5" X 2.5" or 9" x 4.5" x 3" modules. All standard shapes-spiits, soaps, arches, keys and wedges-are available. The tolerances in manufacture and supply are ... 

The largest non-metallurgical use of MnC)2 is in the manufacture of dry-cell batteries (p. 1204) which accounts for about half a million tonnes of ore annually. The most common dry batteries are tif the carbon-zinc Leclanche type in which carbon is the positive pole. Mn02 is incorporated as a depolari/cr to prevent the undesirable liberation of hydrogen gas on to the carbon, probably by the reaction... 

D. H. Scott, Developments Affecting Metallurgical Uses of Coal, IEACR/74, IEA Coal Research, London, 1994. 

The iron and steel industry accounts for about 80% of all molybdenum consumption. The balance of consumption is split between nonferrous metallurgical uses (12%) and chemical applications (11%). 

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