Process for the desulphurization of gaseous substrate

A process for desulfurizing a feed gas containing O.sub.2, SO.sub.2, SO.sub.3, H.sub.2 SO.sub.4, H.sub.2 S, CS.sub.2, COS and/or organic sulfur-containing components, the process comprising the steps of:

• i) adjusting the water content in the feed gas to provide sufficient water for the production of H.sub.2 SO.sub.4 ;
• ii) passing the feed gas into a first of two serially-arranged catalytic heat exchange reactors, wherein each of the catalytic heat exchange reactors contains a catalyst unit disposed over a heat exchange unit, so that the feed gas absorbs heat from the heat exchange unit and passes into the catalyst unit where the oxidizable components in the feed gas are catalytically oxidized into SO.sub.2, H.sub.2 O and CO.sub.2 at a temperature in the range of 300-500.degree. C.;
• iii) discharging the oxidized feed gas from the first of the two catalytic heat exchange reactors and injecting the oxidized feed gas into the second catalyst tower so that the oxidized feed gas passes first through the catalyst unit and residual amounts of SO.sub.2 are oxidized into SO.sub.3 at a range of 300-500.degree. C.;
• iv) passing the SO.sub.3 -containing feed gas into the heat exchange unit within the catalytic heat exchange reactor where the SO.sub.3 -containing feed gas is cooled and the water within the feed gas hydrolyzes the SO.sub.3 into H.sub.2 SO.sub.4, which is condensed and removed from the second catalytic heat exchange reactor;
• v) discharging treated gas from the second catalyst tower at a temperature that is at least 50.degree. C. below the H.sub.2 SO.sub.4 dew point of the process gas after oxidation of the sulfur content in the feed gas;
• wherein the direction of the feed gas flow is cyclically changed, after a period of about 1 to 40 minutes, so that the feed gas is injected into the catalytic heat exchange reactor from which the treated gas was discharged in the previous cycle and first passes through the heat exchange unit in this catalytic heat exchange reactor.