Overall SO2 Oxidation Efficiency

So far, this chapter has examined after-intermediate-H2S04-making SO2 oxidation ejficiency. However, Section 19.6 also provides the information needed to calculate total % SO2 oxidized after SO2 oxidation in all of Fig. 19.2 s catalyst beds. The values are  

FromFig.19.2 kg mol SO2 in first catalyst bed feed gas = 0.1 From Section 19.6 kgmolS02inafter-intermediate-H2S04-makingcatalystbed exit gas = 0.000022 

All values are per kg mol of first before-H2S04-making catalyst bed feed gas. The matrix shows that a 695 K gas temperature is equivalent to oxidation of 69.3% of the after-H2S04-making catalyst bed s input SO2. Cells D8-F8 contain values (Eq. (11.7)). Cells G8-J8 contain H° values. 

12 Matrix rasuits per kg mol of first before-H2S04-making feed gas  

Temperature (K) Heatup path % SO2 oxidized, Equilibrium % SO2 oxidked, 

Total %S02 oxidized after 3 before-H2S04-making beds and 1 after-H2S04-making catalyst bed 

This is somewhat above industrial total SO2 oxidation (99.5-99.9% Hansen, 2004), but it confirms the high SO2 oxidation and H2SO4 making efficiencies of double contact acid plants. 

1 Effect of incomplete SOj-from-gas removal during intermediate H2SO4 making 

Appendix U examines this situation. It shows that this small amount of SO3 has little effect on double contact s overall SO2 oxidation efficiency. 

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Fig. 16.4. Blowup of top portion of Fig. 16.3. Overall SO2 oxidation efficiency increases with each bed but the gain diminishes.

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