Coal analyzer

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At the coal mine this timely coal quality information allows the coal producer to take timely process control actions, such as sorting, blending, or prep plant control. When used in power plants, a coal analyzer can be used for emissions compliance or boiler optimization. Coal quality parameters of greatest interest include ash, moisture, sulfur, and calorific value (also known as heat content). Although most coal operations can obtain this information about coal quality by taking physical samples, then preparing the samples and analyzing them with laboratory equipment, these processes often involve a time lag of up to 24 hours from gathering the sample to final analysis results. In contrast coal analyzers provide analysis information each minute on material being transported by conveyor either at the mine or the power plant. This timely coal quality information in turn allows the operator to improve his process by taking timely process control actions, such as sorting, blending, or prep plant control.

There are several types of coal analyzers. The most sophisticated analyzers use a technique known as prompt gamma neutron activation analysis (PGNAA) to determine the elemental content of the coal. This permits analysis of sulfur, ash, and ash constituents, and when combined with a second type of analyzer--the moisture meter--provides moisture and calorific value as well. Moisture meters are often found in conjunction with the elemental analyzers, but sometimes are used alone, or in conjunction with ash gauges. Most moisture meters use microwave technology, while the simplest ash gauges exploit gamma attenuation principles. Some ash gauges use natural gamma radiation from the coal to estimate ash. There are other types of elemental coal analyzers which measure the composition of the surface of the coal being transported by conveyor. One uses X-ray fluorescence and the other uses Laser Induced Breakdown Spectroscopy (LIBS).

Coal analyzers were first introduced in the early 1980's with the US and Australia leading the way. The demand for coal analyzers has been highest in the US, owing to the need to control sulfur as mandated by the Clean Air Act Amendments of 1977. By the year 2005 more than 600 coal analyzers were in use throughout the world. Most of these analyzers are mounted around an existing conveyor belt, although a significant minority analyze sample streams taken from the main process stream.

[edit] References

  • T. Sikora, I. Motyka, "On-line quality - quantity monitoring or raw coal in coal preparation plant and run of mine in underground of coal mine", "Mechanizacja i Automatyzacja Górnictwa" no 5/2000 p 155-160
  • Snider, Kurt, "Using An On-Line Elemental Coal Analyzer to Reduce Lost Generation Due to Slagging", International On-Line Coal Analyzer Technical Conference, St. Louis, November 8-10, 2004.
  • Evans, Michael, "Cost Justification for a Coal Analyzer Installation", International On-Line Coal Analyzer Technical Conference, St. Louis, November 8-10, 2004.
  • Woodward, Richard, Eric Empey, Michael Evans, "A Major Step Forward for On-Line Coal Analysis", Coal Prep 2003 Conference, Lexington, Kentucky, April 30, 2003.
  • Gaft M, Nagli L (2001). Laser-induced time-resolved evaluation of phosphates with high dolomite content. – Project 99-04-065R, Final report.
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