Industrial multicatalyst bed SO2 oxidation

Industrial SO2 oxidation is done in a sequence of three to five catalyst beds (Figs. 7.6 and 7.7). This section and Fig. 7.8 describe passage of warm feed gas through three catalyst beds with gas cooling between the beds. The sequence is  

Addition of a fourth bed would probably not be worthwhile from the SO3 production (hence H2SO4 production) point of view. It might, however, be worthwhile from the point of view of minimizing SO2 escape to the environment (because SO2 passes untouched through subsequent H2SO4 making). These factors are detailed in Chapters 12-22. 

This chapter describes SO2 oxidation in single contact acid plants. These plants  

Its advantages are more efficient SO2 oxidation and H2S04( ) production—and lower SO2 escape to the enviromnent. However, it is more costly. 

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