Best Bed for Cs Catalyst

Cs-enhanced catalyst is useful in permitting cool input gas - because it deactivates at a relatively cool temperature, Chapter 8. 

However, Cs catalyst is costly, so many acid plants use it in only 1 catalyst bed. Fig. 

5 indicates that the best location for the Cs catalyst bed is after H2SO4 making -where it gives maximum total SO2 oxidation. 

Prevention of catalyst overheating may, however, lead it to be used in the catalyst bed (Fig. 12.7) - even though this is not the best SO2 oxidation efficiency location. 

The calculations are aU based on Table 20.1 s values except for gas input temperature. Tail gas SO2 concentrations in parts per nulbon by volume after SO3 removal are shown above each point. 

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