Hydrogen Chloride is an acidic gaseous pollutant with the chemical formula HCl. It has no colour, has a pungent odour and is considered non-flammable..
Hydrogen Chloride is primarily produced by the combustion of fuels containing traces of Chlorine, which are mainly solid fuels such as coal, municipal solid waste and biomass.
Hydrogen Chloride is known to be highly corrosive and can even be corrosive to metals if dissolved in water forming hydrochloric acid. Exposure to hydrogen chloride can lead to severe skin or eye irritation and respiratory irritation to serious lung issues including pulmonary edema (wet lung).
Control is commonly by the use of gas scrubbers where the polluted air is injected with a highly alkaline material which acts either to neutralise, absorb or otherwise react with the HCl to form a waste eluent which is collected as waste and not exhausted into the atmosphere.
Alkali Environmental perform periodic measurements of Hydrogen Chloride in ducted emissions from point sources to the standard reference method BS EN 1911. The method measures total inorganic chlorides, including hydrogen chloride, with the reported result expressed as HCl. The reported results carry UKAS and MCERTS accreditation where the method can be performed to the standard.
These measurements are taken using a manual sampling train whereby a single result is obtained for a gas sample taken from the duct. In combustion gases the reported results are often corrected for oxygen concentration to avoid the affect of dilution air on the result.
Some examples of common sulphur dioxide emission limits:
30mg/m³ at 11% O₂ – Crematoria
100mg/m³ at 11% O₂ – Combustion of Coated Wood (0.4-3MWth)