Air or SO2 is dried with H2SO4 before being fed to the sulphur burner or converter. The Drying Tower can be under pressure or under suction, with the main gas blower being, respectively, in front of or after the tower. The physical limit of drying is 3 mg/SCF of gas as H2O (= 16 mg/SCF as H2SO4) Large particles (>3 microns) are mechanically entrained from the acid distribution system or packing, typically as a load of 500 – 750 mg/m3. As the Drying Tower operates at relatively low temperature, mist is not thermodynamically formed.
Protect downstream equipment from corrosion. If acid is not removed here, it decomposes in the sulphur burner or converter into SO3 and H2O, which will form additional mist load in the I.A.T. or F.A.T., and affects the life and pressure loss of the 1st catalyst bed.
Using this system, no access inside the vessel is required when changing the panels, which is a major safety feature. There are no bolts to fit inside.
It also means the set of panels can be changed much quicker than a standard horizontal demister, and with low risk of mesh damage and eventual gas by-pass.