Monitoring SO3 for Process Control

Treatments using fuel additives or injection processes can drastically effect the flue gas composition.

Monitor SO₃ slip within an ESP to improve ash collection efficiency whilst minimising sulphuric acid aerosol emissions
Monitor SO₃ slip in an ESP to improve ash collection efficiency. This particular problem is mainly an issue where the fuel has a lower sulphur content (and high fly ash resistivity). The injection of SO₃ into flue gas immediately prior to the precipitator lowers the resistivity of the fly ash, allowing better collection by the ESP.

Any fly ash that is not collected using this method can be clearly termed ‘Sulphuric Acid Smut Emissions’.

It is also possible to over-saturate the gas stream with injected SO₃ - which will produce higher levels of free SO₃ and subsequent sulphuric acid formation - with the downstream problems of cold-end corrosion, visibility etc.

The concentration of SO₃ in the gas stream can be accurately determined from the sulphuric acid dewpoint temperature measurement. Acid Dewpoint Temperature (ADT) monitors display the SO₃ concentration as standard.

Monitoring SO3 slip from an electrostatic precipitator