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Fluorine in Australian export thermal coals

An examination of fluorine in Australian export thermal coals intended for industrial, scientific and research audiences.

• 21 July 2010 | Updated 14 October 2011

• Modes of occurrence
• Behaviour during combustion
• Health and environmental effects
• Analytical methods

Trace elements in coals may be associated with specific minerals or with organic 'coaly' matter.

The sources of trace elements include biological material (plants, algae and bacteria) that is the precursor of the coaly material, water in the peat swamp and mineralogical material washed or blown into the swamp.

Fluorine has been identified as a Hazardous Air Pollutant (HAP) by environmental authorities.

Modes of occurrence

Fluorine occurs in the clay minerals and micas associated with coal and may occur as the mineral fluorapatite and possibly fluorite.

Behaviour during combustion

Fluorine is vaporised during combustion; probably as hydrogen fluoride. There is little condensation on ash particles.

Health and environmental effects

On the spectrums:

• for the NPI health hazard of 0-3, fluorine and compounds registers 1.5
• for the NPI environmental of 0-3, fluorine and compounds registers 1.8.

Fluoride is generally low in coals. Fluoride can be emitted into the atmosphere from power station stacks; some plant species are sensitive to fluoride. Fluoride can leach from coal ash; environmental impacts are unlikely to be significant.

Analytical methods

Techniques based on bomb combustion procedures are not considered accurate. The Australian Standard 1038.10.3 and the ASTM Standard D5987 are based on a pyrohydrolysis procedure. Procedures based on proton induced gamma ray emission (PIGME or PIGE) are also accurate.

AS 1038.10.0, Australian Standard, Coal and coke - Analysis and testing - Part 10.0: Determination of trace elements – Guide to the determination of trace elements.

AS 1038.10.4, Australian Standard Coal and coke – Analysis and testing, Part 10.4: Determination of trace elements – Coal, coke and fly-ash – Determination of fluorine content – Pyrohydrolysis method.

ASTM D5987-96, Standard Test Method for Total Fluorine in Coal and Coke by Pyrohydrolytic Extraction and Ion Selective Electrode or Ion Chromatograph Methods.

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