Efficiency after intermediate H2SO4 making

Fig. 20.3. SO2 oxidation efficiency of acid plants with 1 catalyst bed after intermediate H2SO4 making. Oxidation efficiency increases with increasing number of before-intermediate-H2S04-making beds. However, the difference between 3 -1 and 4 - 1 plants is very small.

Cs catalyst is costly so many acid plants use it in only one catalyst bed. From the SO2 oxidation efficiency point of view, it is best used after intermediate H2SO4 making. 

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