Metrology for sampling and conditioning SO2 emissions from stacks

Industrial processes account for a significant proportion of polluting emissions, including sulfur dioxide (SO₂), a toxic gas which contributes to respiratory illnesses, especially in children and the elderly.

The 2010 Industrial Emissions Directive (IED) requires EU member states to control and reduce effects of emissions and could reduce premature deaths in Europe by 13,000 annually.  The IED requires ~50,000 facilities to meet stricter emission limit values (ELVs) through abatement technologies. These are overseen by continual emission monitoring systems, which are periodically tested using Standard Reference Methods (SRMs).

Comité Européen de Normalisation (CEN) has developed SRMs for SO₂ emissions, as specified in EN 14791, but this manual ‘wet chemistry’ method takes weeks to produce data. Doubts additionally emerged about the method’s suitability for measuring the lower levels of SO₂ expected after the IED. Portable automated measuring systems (P-AMS) were also available, but it was uncertain whether these instrumental methods could be developed into a new SRM as necessary quality assurance and control procedures were lacking.

This project clarified limitations of the existing SRM, proved the equivalence of instrumental methods and provided a lead for developing a replacement standard method.

A method for measuring SO₂ concentrations using instrumental techniques was devised by the consortium, then refined and enhanced through work by CEN/TC 264/WG 16. The methodology was discussed at three TC 264 meetings and set the course for a final draft specification, CEN/TS 17021, which describes a method for sampling and determining concentrations of gaseous SO₂ emissions from stacks. Publication of the CEN/TS 17021 enabled the Environment Agency of England to amend its guidance on monitoring stack emissions.

As lower emission limits come into force, CEN/TS 17021 will assure plant operators that the quality of increasingly sensitive instruments can be assured for measuring this important pollutant — so the IED can support the health and the environmental benefits it was designed to deliver.