The use of High Efficency, Brownian Diffusion type Mist Eliminators in different Sulphuric Acid condensation processes has been done for more than 30 years, but now there are more installations to treat H2S gas emissions and low strength SO2 emissions from refineries and metals processing plants with wet catalysis or WSA process.
Wet Catalysis (where a Sulphuric Acid plant has no Drying Tower), can generate a liquid load of up to 80,000 mg/Nm3 entering the mist eliminator set. Emissions below 30 mg/Nm3 can still be achieved, to meet atmospheric standard, but extreme care is needed on the fibre bed design, and on the materials of construction.
These exit gases contain between 40,000 and 80,000 mg/m3 and are < 3 microns in size. Flooding / re-entrainment of liquid droplets and excessive pressure loss of the Mist Eliminators are to be avoided / minimised.
The WSA technology of Haldor Topsoe uses a Condensation Tower stage, with special glass tubes inside, each always with a small PTFE mesh filter in the top.
In some plant designs, there is a large knitted mesh demister fitted in the top of, or after, the Condensation Tower, for better droplet capture.
In some more recent WSA plant designs, and in retro-fit designs, lower emission standards including almost total removal of sub-micron mist are to be achieved,
These exit gases contain appx. 2,000 mg/m3 and the mist particles are < 3 microns in size.
Air pollution by H2SO4 (& SO3)
High Efficiency, Brownian Diffusion ‘Becofil’ Candle Filters, standing type F, with TGW16 or B14W Glass Fibre elements and Special Alloy or Polypropylene or GRP/FRP structure.