A process for the removal of hydrogen sulfide (H2S) from a H2S-containing gas stream through two or more serially connected catalytic reactors, which process comprises:
- a) mixing the H2S-containing gas stream with a main oxygen-containing gas stream to obtain a gas stream containing both H2S and oxygen,
- b) introducing the obtained gas stream containing both H2S and oxygen into a furnace whereby a gas stream depleted in H2S is obtained,
- c) transferring the gas stream depleted in H2S to a sulfur condenser to obtain a gas stream depleted in sulfur,
- d) introducing the gas stream depleted in sulfur, optionally together with a first auxiliary oxygen-containing gas stream, into a first catalytic reactor R1 containing a catalyst system which catalyzes the Claus reaction of H2S with sulfur dioxide (SO2), the hydrolysis of COS and CS2 and optionally direct oxidation of H2S with oxygen to sulfur, said reactor being operated at a maximum temperature TR1max between 290 and 350° C., whereby a gas stream depleted in H2S is obtained,
- e) transferring the gas stream depleted in H2S to a sulfur condenser to obtain a gas stream depleted in sulfur,
- f) optionally introducing the gas stream depleted in sulfur obtained from reactor R1 through a series of reactors and condensers, each reactor containing a catalyst system which catalyzes the Claus reaction of H2S with sulfur dioxide (SO2) before reaching a last reactor R of the process,
- g) introducing the gas stream depleted in sulfur together with a last auxiliary oxygen-containing gas stream into the last catalytic reactor R containing a catalyst system which catalyzes the Claus reaction of H2S with sulfur dioxide (SO2) and the direct oxidation of H2S with oxygen to sulfur, said reactor being operated at a maximum temperature TRmax below the maximum temperature TR1max of reactor R1, whereby a gas stream depleted in H2S is obtained,
- h) optionally transferring the gas stream depleted in H2S to a sulfur condenser to obtain a gas stream depleted in sulfur,
- i) measuring the volumetric ratio of H2S/SO2 at the exit of the last catalytic reactor R,
- wherein
- the flow rate of oxygen in the main oxygen-containing gas stream and in the optional auxiliary oxygen-containing gas streams represents 96 to 99.9 vol. % of the total flow rate of the oxygen supplemented in the process,
- the flow rate of oxygen in the last auxiliary oxygen-containing gas stream represents 0.1 to 4 vol. % of the total flow rate of the oxygen supplemented in the process, and
- wherein the flow rate of oxygen in the last auxiliary oxygen-containing gas stream is adjusted depending on the value of the volumetric ratio of H2S/SO2 measured at the exit of the last catalytic reactor R in i) so that the volumetric ratio of H2S/SO2 measured in i) remains between 1.9 and 2.2.