Maximum Feed Gas SO2 Strength

Gases stronger than 13 volume% SO2 will always give intercept temperatures in the catalyst degradation range. They must be diluted with air before they are catalytically oxidized. 

Dilution is not a problem, but it requires more equipment and gas blowing power. 

However, this requires larger equipment and more gas blowing power. 

Alternatively, some cooled I0W-SO2 first catalyst bed exit gas can be recycled into the first catalyst bed feed gas stream. This is discussed in Chapter 27. 

This chapter assumes that equilibrium is attained in an acid plant s first catalyst bed, i.e., that a feed gas s heatup path always intercepts its equilibrium curve. 

We now add the specification that there is no oxidation or reduction once equilibrium is attained, i.e., that  

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