Inadequate SO2 oxidized in first catalyst bed

5O2 —i- SO3 oxidation efficiency in a first catalyst bed is always below - 80%. This is totally inadequate for efficient, low SO2 emission H2SO4 production. 

This limitation is overcome industrially by passing first catalyst bed exit gas through two or more gas cooling catalytic oxidation steps bringing SO2 oxidation efficiency up to 98+%. 

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