Absorption of wet conversion gas

In a process for the manufacture of sulfuric acid which comprises catalytically oxidizing a wet feed gas containing sulfur dioxide to produce a wet conversion gas, said wet feed gas having been produced by oxidation of a source of sulfur with a source of oxygen comprising undried air, and contacting the wet conversion gas with sulfuric acid, thereby producing sulfuric acid by absorption of components of the wet conversion gas into the sulfuric acid stream, the improvement which comprises:

• contacting a wet conversion gas with sulfuric acid in a heat recovery absorption stage to effect absorption and generate the heat of absorption, said sulfuric acid being introduced into said heat recovery stage at a temperature of at least about 170.degree. C. and a concentration of between about 98.5% and about 99.5%, the sulfuric acid stream as discharged from said heat recovery stage being at a temperature of at least about 190.degree. C. and having a concentration of between about 99% and about 100%, the temperature of the gas entering the heat recovery stage being at least about 50.degree. C. above its dew point, said dew point being not more than about 40.degree. C. above the temperature of the acid as discharged from said heat recovery stage;
• recovering the heat of absorption from said discharge absorption acid stream in useful form by transfer of heat to another fluid in a heat exchanger, thereby heating said another fluid to a temperature of at least about 140.degree. C.;
• and
• contacting the exit gas from said heat recovery absorption stage with sulfuric acid in a condensing stage for absorption of residual sulfur trioxide and condensation of sulfuric acid vapor, said contact in said condensing stage being carried out before said exit gas is either exhausted from the process of catalytically oxidized to produce additional sulfur trioxide.