Process for the removal of hydrogen sulfide from a gas stream

A process for the removal of hydrogen sulfide from a gas stream containing hydrogen sulfide by catalytic direct oxidation, which process comprises

• a) mixing a gas stream containing hydrogen sulfide with an oxygen containing gas to obtain a gas stream containing both hydrogen sulfide and oxygen,
• b) transferring the gas stream containing both hydrogen sulfide and oxygen into a first section of a first reactor, which first section contains a non-cooled adiabatic bed containing a first catalyst which catalyzes the oxidation of hydrogen sulfide with oxygen and the oxidation of hydrogen sulfide with sulfur dioxide, wherein the temperature of the adiabatic bed is T1,
• c) transferring the gas stream from the first section of the first reactor to a second section of the first reactor, which second section contains a second catalyst which is different from the first catalyst and which second section is kept at a temperature T2 wherein T2≦T1 and T2 is higher than the dew point temperature of elemental sulfur and not higher than 300° C. whereby a gas stream depleted in hydrogen sulfide is obtained,
• d) transferring the gas stream depleted in hydrogen sulfide to a sulfur condenser to obtain a gas stream depleted in sulfur,
• e) transferring the gas stream depleted in sulfur into the first section of a second reactor, which first section contains the same catalyst as the first section of the first reactor, wherein the first section of the second reactor is kept at a temperature that is above the dew point of the elemental sulfur so that in the first section of the second reactor no elemental sulfur precipitates as liquid or solid on the catalyst,
• f) transferring the gas stream from the first section of the second reactor to the second section of the second reactor which contains the same catalyst as the second section of first reactor and which second section is kept at a temperature that is at or below the dew point of elemental sulfur so that in the second section of the second reactor elemental sulfur precipitates as liquid or solid on the catalyst,
• g) removing the desulfurized gas stream from the second reactor and
• h) after a defined time switching the operation conditions of the first reactor and the second reactor and switching the gas flow simultaneously so that the previous second reactor becomes the new first reactor and the previous first reactor becomes the new second reactor,
• i) wherein the gas stream containing hydrogen sulfide that is introduced into the first reactor has not previously been subjected to the combustion step of a Claus process, and
• j) wherein the temperature of the first section of the first reactor is in the range of 180 to 300° C.