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*The proximate analysis consists of four items: fixed carbon, volatile matter, moisture and ash, all on a weight percent basis. | *The proximate analysis consists of four items: fixed carbon, volatile matter, moisture and ash, all on a weight percent basis. | ||
*The ultimate analysis provides | *The ultimate analysis provides an element-by-element composition of the coal's organic fraction, namely: carbon, hydrogen, oxygen and sulfur, all on a weight percent basis. | ||
Both the proximate and the ultimate analysis may be reported on a dry (d) or moist basis, an ash-free | Both the proximate and the ultimate analysis may be reported on an ''as received'' (ar) basis, a ''dry'' (d) or ''moist'' basis, an ''ash-free'' (af) basis, a ''mineral matter-free'' (mmf) basis and various combinations of those bases. For example, an analysis may report the basis to be: as received (ar), dry and ash-free (daf), moist and ash-free (moist af), dry and mineral matter-free (dmmf) or moist mineral-matter free (moist mmf). | ||
Ash and mineral matter are two distinctly different entities. Mineral matter consists of the various minerals contained in the coal. Ash is the inorganic solids remaining after the coal is completely combusted. The ash is usually less than the mineral matter because of the weight changes that take place during coal combustion. such as the loss of gaseous CO<sub>2</sub> from mineral carbonates, the loss of water from silica minerals and the loss of sulfur (as gaseous SO<sub>2)</sub>) from iron pyrites. | |||
Some examples of proximate and ultimate analyses aregiven in the table below: | |||
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Revision as of 15:16, 2 May 2009
Coal analysis
The composition of a coal is usually reported in terms of its proximate analysis and its ultimate analysis:
- The proximate analysis consists of four items: fixed carbon, volatile matter, moisture and ash, all on a weight percent basis.
- The ultimate analysis provides an element-by-element composition of the coal's organic fraction, namely: carbon, hydrogen, oxygen and sulfur, all on a weight percent basis.
Both the proximate and the ultimate analysis may be reported on an as received (ar) basis, a dry (d) or moist basis, an ash-free (af) basis, a mineral matter-free (mmf) basis and various combinations of those bases. For example, an analysis may report the basis to be: as received (ar), dry and ash-free (daf), moist and ash-free (moist af), dry and mineral matter-free (dmmf) or moist mineral-matter free (moist mmf).
Ash and mineral matter are two distinctly different entities. Mineral matter consists of the various minerals contained in the coal. Ash is the inorganic solids remaining after the coal is completely combusted. The ash is usually less than the mineral matter because of the weight changes that take place during coal combustion. such as the loss of gaseous CO2 from mineral carbonates, the loss of water from silica minerals and the loss of sulfur (as gaseous SO2)) from iron pyrites.
Some examples of proximate and ultimate analyses aregiven in the table below:
Coal Rank |
Proximate Analysis (wt % ar) |
Ultimate Analysis (wt % maf) |
Net Heating Value (maf) (MJ/kg) | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Fixed carbon |
Volatile matter |
Moisture |
Ash |
C |
H |
O |
N |
S | |||
| Anthracite | 81.8 | 7.7 | 4.5 | 6.0 | 91.8 | 3.6 | 2.5 | 1.4 | 0.7 | 36.2 | |
| Bituminous | 54.9 | 35.6 | 5.3 | 4.2 | 82.8 | 5.1 | 10.1 | 1.4 | 0.6 | 36.1 | |
| Subbituminous | 43.6 | 34.7 | 110.5 | 11.2 | 76.4 | 5.6 | 14.9 | 1.7 | 1.4 | 31.8 | |
| Lignite | 27.8 | 24.9 | 36.9 | 10.4 | 71.0 | 4.3 | 23.2 | 1.1 | 0.4 | 26.7 | |
| Notes: • wt % = percent by weight ar = as received maf = moisture and ash free | |||||||||||
- ↑ Chris Higman and Maarten van der Burgt (2008). Coal Gasification, 2nd Edition. Gulf Professional Publishers. ISBN 0-7506-8528-X.