Production of sulfuric acid and installation therefor

In the production of sulfuric acid by (a) oxidizing a sulfurous material with an oxidant to obtain sulfur dioxide, (b) catalytically oxidizing this with oxygen to obtain sulfur trioxide and (c) producing sulfuric acid and a waste gas, at least part of the waste gas is recycled to the first step. The fabrication of sulfuric acid consists of: (a) producing sulfur dioxide from a sulfur based material and an oxidant; (b) converting catalytically the sulfur dioxide into trioxide in a catalytic converter fed with oxygen; and (c) producing sulfuric acid from the sulfur trioxide. In the last step, some other gases are also produced which are (partially) recycled into the oxidant used in step (a). An Independent claim is also included for apparatus for performing the process. The apparatus for H2SO4 production consists of: (a) production unit (10') of SO2 from a sulfurous raw material and an oxidant; (b) catalytic converter (20') of SO2 equipped with means of feeding O2; and (c) preparation unit (30') of H2SO4 from SO3 It comprises also means for recycling waste gases at the outlet of the preparation unit (30') of H2SO4 towards the SO2 production unit (10').