Method and device for the desulphurisation of a gas stream containing hydrogen sulphide

Abstract

A method for the desulphurisation of a gas stream containing hydrogen sulphide, in particular a combustion gas stream used for combustion in a gas turbine, wherein the gas stream is brought into contact with a scrubbing medium containing a catalyst to absorb the hydrogen sulphide, forming elementary sulphur; the catalyst is reduced on formation of the elementary sulphur; the scrubbing medium containing the reduced catalyst is fed to a regeneration stage in which the reduced catalyst is regenerated by oxidation with an oxygen-containing gas which is fed to the regeneration stage; the oxygen-containing gas is fed to the regeneration stage from a compression stage of the gas turbine; and the gas which is depleted of oxygen during regeneration of the catalyst is fed to at least one turbine stage fluidically connected downstream of the compression stage.

Claims

1. A method for desulfurizing a gas stream comprising hydrogen sulfide utilizable for combustion in a gas turbine, the method comprising: contacting the gas stream with a catalystcomprising a scrubbing medium for absorbing the hydrogen sulfide with formation of elemental sulfur, the catalyst being reduced in the formation of the elemental sulfur, supplying the scrubbing medium comprising the reduced catalyst to a regeneration stage in which the reduced catalyst is regenerated by oxidation with an oxygen-containing gas fed to the regeneration stage, feeding the oxygen-containing gas to the regeneration stage from a compression stage of the gas turbine, and feeding oxygen-depleted gas from the regeneration of the catalyst to at least one turbine stage of the gas turbine, the at least one turbine stage connected fluidically downstream of the compression stage, and utilizing the oxygen-depleted gas for cooling turbine blades of the gas turbine.

2. The method as claimed in claim 1, wherein the feeding of the oxygen-containing gas to the regeneration stage comprises feeding from a cooling air system of the gas turbine.

3. The method as claimed in claim 1, wherein the feeding of the oxygen-depleted gas to the at least one turbine stage comprises feeding to a combustion chamber of the gas turbine.

4. The method as claimed in claim 1, further comprising: cooling the oxygen-containing gas taken from the compression stage before entry into the regeneration stage.

5. The method as claimed in claim 1, further comprising: decompressing the scrubbing medium before being fed to the regeneration stage.

6. The method as claimed in claim 1, further comprising: removing at least one substream of the scrubbing medium.

7. The method as claimed in claim 1, further comprising: feeding the scrubbing medium which is regenerated to an absorber.

8. The method as claimed in claim 1, wherein an amino acid salt solution is used as scrubbing medium.

9. The method as claimed in claim 1, wherein a metal salt is used as the catalyst.

10. The method as claimed in claim 1, wherein the gas stream comprises a fuel gas stream.

11. An apparatus for desulfurizing a gas stream comprising hydrogen sulfide utilizable for combustion in a gas turbine, the apparatus comprising: an absorber for absorbing hydrogen sulfide from the gas stream to form elemental sulfur by means of a catalystcomprising scrubbing medium, and a regeneration stage, coupled fluidically to the absorber, for regenerating the catalyst, reduced in the formation of sulfur, by an oxygen-containing gas, wherein the regeneration stage is coupled fluidically to a compression stage of a gas turbine for feeding the oxygen-containing gas, wherein the regeneration stage is coupled fluidically to at least one compression stage of a turbine stage for taking off oxygen-depleted gas, the at least one compression stage connected fluidically downstream of the gas turbine, and wherein the regeneration stage is coupled to a cooling system connected fluidically downstream of the compression stage, for cooling turbine blades.

12. The apparatus as claimed in claim 11, wherein the regeneration stage is coupled fluidically to a cooling air system of the gas turbine, for feeding the oxygen-containing gas.

13. The apparatus as claimed in claim 11, wherein the regeneration stage is coupled to a combustion chamber connected fluidically downstream of the compression stage.

14. The apparatus as claimed in claim 11, wherein a decompression stage is connected fluidically between the absorber and the regeneration stage.

15. The apparatus as claimed in claim 11, wherein the gas stream comprises a fuel gas stream.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An exemplary embodiment of the invention will be explained in more detail in the following text on the basis of the drawing.

DETAILED DESCRIPTION OF INVENTION

(2) The FIGURE shows an apparatus 1 for desulfurizing a gas stream 3 and more particularly for desulfurizing a fuel gas stream for a gas turbine. The gas stream 3 is fed to an absorber 5 via a feed line 6 connected to the latter, and is contacted within the absorber 5 with an aqueous amino acid salt solution as scrubbing medium 7. Within the absorber 5, hydrogen sulfide 9 present in the gas stream 3 is absorbed in the scrubbing medium 7. The gas cleaned to remove hydrogen sulfide 9 is withdrawn from the absorber 5 via an offtake line 11 and fed to the combustion in a gas turbine process.

(3) The hydrogen sulfide 9 absorbed in the scrubbing medium 7 is oxidized to elemental sulfur 15 by a catalyst 13 present in the scrubbing medium 7, and in the present case complexed Fe(III) ions. During the oxidation of the hydrogen sulfide 9, the catalyst 13 is reduced to Fe(II) ions. The sulfur 15 precipitates as a solid, and the Fe(II) ions formed by the reduction remain in solution and are masked by EDTA as a complexing agent added to the scrubbing medium 7.

(4) The scrubbing medium 21, comprising the reduced catalyst 17 and the elemental sulfur 15, is fed subsequently to a decompression stage (flash stage) 23 connected fluidically downstream of the absorber 5. The feed is made via a fluidic coupling between an offtake line 25 connected to the absorber 5, and a feed line 27 of the decompression stage 23.

(5) Within the decompression stage 23, the scrubbing medium 21 is decompressed, and methane contained within it is desorbed. The desorbed methane is fed to a gas turbine 31 via an offtake line 29 connected to the decompression stage 23. For this purpose, the offtake line 29 is coupled to a feed line 33 of the gas turbine 31.

(6) Additionally, a substream 35 of the scrubbing medium 21 is withdrawn via a withdrawal line 37 connected to the decompression stage 23. As a result of this, the concentration of precipitated sulfur 15 in the scrubbing medium 21 is lowered to a concentration of about 5%.

(7) The substream 35 taken off from the scrubbing medium 21 is fed to a removal unit 39 in the form of a filter, in which the sulfur 15 is removed from the scrubbing medium 21. The sulfur 15 itself is fed to a further utilization. The scrubbing medium 21, cleaned to remove sulfur 15, is recycled. For this purpose, a recycle line 41 of the removal unit 39 is coupled fluidically to an offtake line 43 of the decompression stage 23. Via this coupling, the scrubbing medium 21 freed of sulfur is combined with the main stream 45 of the scrubbing medium 21.

(8) The degassed scrubbing medium 21, cleaned to remove sulfur 15, is then fed to the top 51 of the regeneration stage 49 via a feed line 47 of said regeneration stage 49, said feed line 47 being coupled to the offtake line 43 of the decompression stage 23. Within the regeneration stage 49, the scrubbing medium 21 is contacted with an oxygen-containing gas 53 which flows into the regeneration stage 49 via a feed line 57 connected to the base 55 of the regeneration stage 49.

(9) The oxygen-containing gas 53 here is withdrawn from a compression stage 59, in other words a compressor of the gas turbine 31. The oxygen-containing gas 53 is fed via the fluidic coupling of an offtake line 61 of the compression stage 59, in the present case of the cooling air system 60 of the gas turbine 31, to the feed line 57 of the regeneration stage 49. By way of this fluidic coupling, oxygen-containing gas 53 withdrawn from the compression stage 59 is able to flow into the regeneration stage 49 and be utilized there for regenerating the reduced catalyst 17 contained in the scrubbing medium 21. The scrubbing medium 21 is regenerated at the same time.

(10) The oxygen-containing gas 53, in other words the air withdrawn from the gas turbine 31, flows into the regeneration stage 49 in a flow direction 65 which is opposite to the flow direction 63 of the scrubbing medium 21. Disposed in the feed line 57 of the regeneration stage 49 is a heat exchanger 67, which cools the gas 53 before entry into the regeneration stage 49. The heat taken off in this procedure can be fed into the operation at a suitable point.

(11) The catalyst 13 is regenerated by the contact of the scrubbing medium 7 with the oxygen-containing gas 53. In this case, the oxygen present in the gas 53 transfers from the gas phase into the liquid phase. Consequently, the Fe(II) ions reduced beforehand in the formation of the sulfur are oxidized to Fe(III) ions and hence the catalyst 13 is recovered. As part of the regeneration, the scrubbing medium 7 is also recovered, and is now available againcontaining the original catalyst 13for removing hydrogen sulfide 9 from a gas stream 3. For that purpose, the regenerated scrubbing medium 7 is withdrawn via an offtake line 69 connected at the base 55 of the regeneration stage 49, and is fed to the absorber 5 by way of a fluidic coupling of the offtake line 69 to a feed line 71 of said absorber 5.

(12) The oxygen-depleted gas 73, in other words the waste air, formed during the regeneration of the catalyst 13 within the regeneration stage 49 is then returned to the gas turbine process.

(13) For this purpose, the oxygen-depleted gas 73 is withdrawn from the regeneration stage 49 via an offtake line 75 connected to said regeneration stage 49, and is fed to a turbine stage 77 connected fluidically downstream of the compression stage 59 of the gas turbine 31. For this feed, offtake line 75 of the regeneration stage 49 is coupled fluidically to a feed line 79 of the turbine stage 77. In the present case, the turbine stage 77 is the combustion chamber 81 of the gas turbine 31, and so the low-oxygen gas 73 flows directly into the combustion process of the gas turbine 31. Alternatively or additionally, the low-oxygen gas 73 may be utilized for cooling the turbine blades of the gas turbine 31.

(14) An above-described procedure allows economic catalyst regeneration even under high pressure. The highly optimized flow conditions in the respective compression stage 59 of the gas turbine 31 are unaffected. As compared with regeneration of the catalyst 17 under atmospheric pressure, the air volume flow for compression when air from the compression stage 59 of a gas turbine 31 is fed in is substantially smaller for achieving the pressure increase needed for the regeneration.

(15) The waste air, in other words the gas 73 depleted in oxygen during the regeneration of the catalyst 17, which has left the regeneration stage 49 again, still has a high pressure level on exit and can be fed accordingly to a turbine stage 77 connected fluidically downstream of the compression stage 59. Not only the withdrawal of air but also the return feed requires only minor structural modifications to the gas turbine 31, if any.

(16) Additionally, the combustion of the low-oxygen gas 73, in other words of the waste air taken off from the regeneration stage 49, reduces unwanted emissions.

(17) The invention, while particularly clear from the exemplary embodiment described above, is nevertheless not confined to this exemplary embodiment. Instead, further embodiments of the invention may be derived from the claims and from the description hereinabove.