Patent ID: 7691360

Claim:
A process for the production of sulphuric acid, comprising reacting a sulphur dioxide-containing feed gas, at least in part, with oxygen in at least two contact stages of main contacts, arranged in series, to generate sulphur trioxide, feeding the generated sulphur trioxide-containing gas to an absorber and reacting said sulphur trioxide-containing gas therein to form sulphuric acid, withdrawing a partial stream of the sulphur dioxide and sulphur trioxide-containing gas from a contact stage located upstream of the last main contact stage, mixing said partial stream with the feed gas to form a contact gas having a sulphur dioxide content of more than 13% by volume, and returning said mixed partial stream to the first contact stage, wherein the contact stages contain a catalyst and wherein the partial stream withdrawn from the contact stage located upstream of the last main contact stage has a sulphur trioxide content of from about 9% by volume to about 21% by volume.