Absorption of wet conversion gas

Abstract

An improved process for manufacture of sulfuric acid by catalytic oxidation of wet sulfur dioxide gas. Wet conversion gas is contacted with sulfuric acid in a heat recovery stage to effect absorption and generate the heat of absorption. Wet gas having a mole ratio of sulfur trioxide to water vapor of at least 0.95 is introduced into the heat recovery stage at a temperature above the dew point of the gas. Sulfuric acid is introduced into the heat recovery absorption stage at a temperature of at least about 170.degree. C. and a concentration between about 98.5% and about 99.5%. The sulfuric acid stream as discharged from the absorption stage is at a temperature of at least about 190.degree. C. and has a concentration between about 99% and about 100%. The heat of absorption is recovered from the discharge absorption acid stream in useful form by transfer of heat to another fluid in a heat exchanger, the another fluid being heated to a temperature of at least about 140.degree. C. The exit gas stream from the heat recovery stage is contacted with sulfuric acid in a condensing stage for absorption of residual sulfur trioxide and condensation of sulfuric acid vapor. The liquid/gas contact in the condensing stage is carried out before the exit gas is either exhausted from the process or catalytically oxidized to produce additional sulfur trioxide.