Measurement of SO₃ in Flue Gas from Anode Baking Furnace

Anode baking furnaces can have significant emissions of sulphuric gases, SO₃ is of particular concern due to its acidity. It can condense to sulphuric acid and result in severe corrosion, as well as giving the “blue plume” of sulphuric acid mist around the chimneys. In addition, SO₃ mist is a significant problem for many CO₂ capture technologies. The NaCl trap methodology was used for sampling, selectively reacting SO₃ with NaCl at 200 °C to form Na₂SO₄. SO₂ and other sulphuric compounds will not react under these conditions. All samples were collected with two traps in series. It was found that sulphur was only present in the first salt trap, and no breakthrough was observed. Analytical sensitivity for the samples was estimated, the main factors determining the level of detection (LOD) are background sulphur from the salt and analytical accuracy in the ICP-MS methodology.