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Aside from electric power, the steel industry, and the chemical industry, small amounts of coal are also used to make activated carbons (also made from coal tars), humic acids for fertilizers and silicon metal for a wide array of silicon products. Coals and coal byproducts have also been tested for a wide array of chemical products such as activated carbons and chemical sieves, but those products are currently made from other materials.

The Blue Gem Coal and Silicon Metal

Silica (SiO2) is one of the most common elements on earth. It is a major constituent of most beach sands and sandstones. Silicon (Si) is an element in silica. Pure silicon, or silicon metal is used in the silicone industry, the aluminum industry, and in the construction of photo-voltaic cells.

Silicon metal is made by chemically and thermally reducing silica sand (SiO2) with carbon (C) materials (coke, coal, wood chips, and/or charcoal) in a submerged electric-arc furnace at very high temperatures (4000°F, 2350°C). The reaction,

SiO2 + 2C Si + 2CO

produces molten silica (Si) and carbon monoxide (CO) gas. The molten silica is cooled and sold as silicon metal. Other elements can be added to the molten silica to make alloys for the semi-conductor industry.

The Blue Gem coal of southeastern Kentucky is widely considered one of the best coal-carbon sources for silicon metal in the world. It is an unusual coal with very low sulfur (< 1%) and exceptionally low ash (<1.5%) yields. For comparison, the average mined eastern Kentucky coal has sulfur values of 1 to 2% and ash yields of 8 to 10%. The ash content of the Blue Gem coal is so unique, that it is actually less than the ash content of the living plants from which the coal formed! The Blue Gem coal also is used to make silicon metal because of its low ash fusion temperature (Gardner and others, 2007; Hower and others, 2007) and high-silicon reactivity (Myrvagnes and Lindstad, 2007). Silicon reactivity is the relative ability of the carbon in the coal to react with silicon. The Blue Gem coal has very high reactivity compared to most other coals.

 

Other Uses of Coal:

References for Specialty products and silicon metal from coal

  • Gardner, J. S., Andrews, R.J., Hower, J.C., and Amick, M., 2007, Blue Gem coal, southeastern Kentucky: A prime resource for the production of silicon metals and anode coke for aluminum: Geological Society of America Abstracts with Programs, v. 39, no. 2, p. 80.
  • Downing, J.H., Mcclincy, R.J., and Wilson, B.J., 1972, Furnace charge for use in the production of silicon metal: U.S. Patent Office, Patent no. US-3660298-A, http://www.google.com/patents/US3660298.
  • Hower, J.C., Andrews, R.J., Rantell, T., Gardner, J.S. and Amick, M., 2007, Utilization of coal for production of silicon metals and aluminum: Example of the Blue Gem coal, Southeastern Kentucky: Geological Society of America Abstracts with Programs, v. 39, no. 6, p. 134.
  • Kuhlmann, A.M., 1965, Silicon metal production: U.S. Patent US-3215522-A, http://www.google.com/patents/US3215522.
  • Lizzio, A.A. and Rostam-Abadi, M., 1993, Production of carbon molecular sieves from Illinois coal: Fuel Processing Technology, v. 34, no. 2, p.97-122.
  • Myrvagnes, V. and Lindstad, T., 2007, The importance of coal-and coke properties in the production of high silicon alloys: Infacon XI, Proceedings of the Innovations in Ferro Alloy Industry, v.18, p. 402-413.

 

 

Last Modified on 2019-09-24
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