Method and device for the treatment of a gas stream, in particular for the treatment of a natural gas stream

Abstract

A method for the treatment of a gas stream, wherein before the combustion of the gas stream, hydrogen sulfide is separated out of the gas stream in a first absorber by an absorption medium, the treated gas stream purified of hydrogen sulfide is burnt in a combustion apparatus, the carbon dioxide contained in the exhaust gas of the burnt gas stream after combustion is separated in a second absorber by an absorption medium, and the separated hydrogen sulfide and carbon dioxide are separated in at least one desorber from the absorption medium for the regeneration of the latter. The same absorption medium separates the hydrogen sulfide out of the gas stream and the carbon dioxide out of the exhaust gas. A corresponding device for the treatment of a gas stream has a first absorber and a second absorber flow-connected to one another for the exchange of absorption medium.

Claims

1. A method for the treatment of a gas stream, the method comprising: before the combustion of the gas stream, separating out hydrogen sulfide from the gas stream in a first absorber by an absorption medium, burning the treated gas stream purified of hydrogen sulfide in a combustion apparatus, separating carbon dioxide contained in the exhaust gas of the burnt gas stream in a second absorber by the absorption medium, and separating the separated hydrogen sulfide and the separated carbon dioxide from the absorption medium in at least one desorber for the regeneration of the absorption medium, wherein the same absorption medium is used for separating the hydrogen sulfide out of the gas stream and for separating the carbon dioxide out of the exhaust gas, the absorption medium containing dioxide flowing out of the second absorber via a discharge line of the second absorber directly into a delivery line of the first absorber.

2. The method as claimed in claim 1, wherein an amine-containing absorption medium is used.

3. The method as claimed in claim 1, wherein an amino acid salt is used as the absorption medium.

4. The method as claimed in claim 1, wherein the desorption of the hydrogen sulfide and the desorption of the carbon dioxide out of the absorption medium takes place in a common desorber.

5. The method as claimed in claim 1, wherein the desorption of the hydrogen sulfide and the desorption of the carbon dioxide out of the absorption medium takes place in each case in a separate desorber.

6. The method as claimed in claim 1, wherein the gas stream comprises a natural gas stream.

7. A device for the treatment of a gas stream, comprising: a first absorber for separating hydrogen sulfide out of the gas stream by an absorption medium, a combustion apparatus, following the first absorber, for the combustion of the gas stream purified of hydrogen sulfide, a second absorber, following the combustion apparatus, for separating carbon dioxide out of the exhaust gas of the combustion apparatus by the absorption medium, and at least one desorber for the desorption of separated hydrogen sulfide and of separated carbon dioxide out of the absorption medium, wherein the first absorber comprises a delivery line and a discharge line for the absorption medium, and the delivery line of the first absorber is flow-connected to a discharge line of the second absorber for the exchange of the absorption medium.

8. The device as claimed in claim 7, wherein the first absorber is flow-connected via its discharge line to the delivery line of a first desorber.

9. The device as claimed in claim 8, wherein the first desorber is flow-connected to the delivery line of the second absorber via a recirculation line.

10. The device as claimed in claim 8, wherein the first desorber has connected to it a discharge line which issues in a treatment apparatus.

11. The device as claimed in claim 7, further comprising: a branch line connected to the discharge line of the second absorber and flow-connected to the delivery line of a second desorber.

12. The device as claimed in claim 11, further comprising: a reboiler connected to the first desorber and/or to the second desorber.

13. The device as claimed in claim 11, wherein the first desorber and the second desorber are coupled thermally to one another.

14. The device as claimed in claim 7, wherein the combustion apparatus comprises a gas turbine.

15. The device as claimed in claim 7, further comprising: a heat recovery apparatus arranged between the combustion apparatus and the second absorber.

16. The device as claimed in claim 7, wherein the gas stream comprises a natural gas stream.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the invention are explained below by means of a drawing in which:

(2) FIG. 1 shows a device for the treatment of a natural gas stream with two flow-connected absorbers and with a desorber,

(3) FIG. 2 shows a further device for the treatment of a natural gas stream with two flow-connected absorbers and with two separate desorbers, and

(4) FIG. 3 shows a further device for the treatment of a natural gas stream with two flow-connected absorbers and with two thermally coupled desorbers.

DETAILED DESCRIPTION OF INVENTION

(5) FIG. 1 shows a device 1 for the treatment of a natural gas stream (EG) by the absorption of hydrogen sulfide (H.sub.2S) and of carbon dioxide (CO.sub.2). The device 1 comprises a first absorber 3 designed as an H.sub.2S absorber and having an absorption medium 5 for the separation of hydrogen sulfide out of the natural gas stream.

(6) The crude natural gas stream flows via a delivery line 7 to the first absorber 3 and comes into contact there with the absorption medium 5. The absorption medium 5 used is an aqueous amine solution in which the hydrogen sulfide contained in the natural gas stream is absorbed.

(7) The natural gas stream, as far as possible purified of H.sub.2S, is then delivered from the first absorber 3 to a following combustion apparatus 9 designed as a gas turbine. In the gas turbine 9, the natural gas stream is burnt, and the resulting flue gas (RG) is subsequently delivered to a heat recovery apparatus 11 having a flue gas cooler 13. The flue gas cooler 13 in this case precools the flue gas arising from combustion in the gas turbine 9 for absorption purposes. The flue gas is streamed into a second absorber 17 via a blower 15 following the flue gas cooler 13.

(8) The second absorber 17 is designed as a CO.sub.2 absorber and serves correspondingly for separating the carbon dioxide contained in the flue gas. For this purpose, after combustion in the second absorber 17, the flue gas is likewise brought into contact with the absorption medium 5 and absorbs the CO.sub.2 contained in the flue gas.

(9) The absorption medium 5 employed thus serves equally for absorbing hydrogen sulfide out of the natural gas stream before combustion (pre-combustion capture) and for absorbing carbon dioxide from the flue gas after combustion (post-combustion capture). The first absorber 3 and the second absorber 17 are correspondingly flow-connected to one another for the exchange of the absorption medium 5.

(10) Connection is made possible in that the first absorber 3 comprises for the absorption medium 5 a delivery line 19 which is connected to a discharge line 21 of the second absorber 17. The exchange of the absorption medium 5 between the two absorbers 3, 17 thereby becomes possible.

(11) The absorption medium 5 in this case performs both separation tasks, that is to say it is suitable for separating the hydrogen sulfide in the first absorber 3 out of the natural gas before combustion and for likewise separating the carbon dioxide out of the flue gas in the second absorber 17 after combustion.

(12) Furthermore, the first absorber 3 comprises a discharge line 23. The first absorber 3 is flow-connected to the delivery line 25 of a desorber 27 via this discharge line 23. The absorption medium 5 laden with H.sub.2S and CO.sub.2 is pumped via these two lines 23, 25 into the desorber 27 by means of a pump 29, along with a rise in temperature, for regeneration.

(13) In this case, the laden absorption medium 5 passes through a heat exchanger 31 in which the heat of the regenerated absorption medium 5 flowing from the desorber 27 to the second absorber 17 is transferred to the laden absorption medium 5 delivered by the first absorber 3. The heat exchanger 31 in this case utilizes the waste heat of the first desorber 27 in order to preheat the absorption medium 5 from the first absorber 3 before entry into the desorber 27.

(14) Within the desorber 27, the CO.sub.2 absorbed in the absorption medium 5 and the absorbed H.sub.2S are desorbed thermally. For the treatment and transfer of the desorbed components, a discharge line 33 is connected to the first desorber 27 and issues in a treatment apparatus 35. In the treatment apparatus 35, which is designed as a Claus plant, sulfur is produced by reaction with oxygen. The desorbed CO.sub.2-rich gas stream may be compressed in order to allow transport to a storage depot. The desorber 27 is thus configured as a common desorber for H.sub.2S and for CO.sub.2.

(15) Furthermore, a recirculation line 37 is connected to the first desorber 27. The recirculation line 37 is flow-connected to the delivery line 39 of the second absorber 17. The absorption medium 5 regenerated in the desorber 27 is recirculated into the second absorber 17 via the flow connection between the recirculation line 37 and the delivery line 39 and is available there for the renewed absorption of CO.sub.2 from the flue gas and, further, also for the absorption of H.sub.2S from the crude natural gas stream in the first absorber 3.

(16) Furthermore, the desorber 27 has connected to it a reboiler 41 which supplies the necessary regeneration heat for separating CO.sub.2 and H.sub.2S from the absorption medium 5. The laden absorption medium 5 is in this case regenerated by steam which is generated in the reboiler 41. The reboiler 41 is heated by imported heat, for example from a connected steam power plant, although this is not shown in the present case.

(17) FIG. 2 shows a further device 51 for the treatment of a natural gas stream (EG) by the absorption of hydrogen sulfide (H.sub.2S) and of carbon dioxide (CO.sub.2). Like the device 1 according to FIG. 1, the device 51 comprises a first absorber 53 designed as an H.sub.2S absorber and having an absorption medium 55 for separating the hydrogen sulfide out of the natural gas stream.

(18) For this purpose, the natural gas is delivered to the first absorber 53 via a delivery line 57 and comes into contact there with the absorption medium 55. The absorption medium 55 used is an aqueous amino acid salt solution.

(19) The hydrogen sulfide contained in the natural gas is removed in the first absorber 55 by absorption, and the purified natural gas stream is then delivered to a following combustion apparatus 59 designed as a gas turbine. In the gas turbine 59, the natural gas stream is burnt, and the flue gas (RG) occurring during combustion is delivered to a heat recovery apparatus 61. The heat recovery apparatus 61 comprises a flue gas cooler 63 which precools the flue gas for absorption in a second absorber 65. The flue gas is blown into the second absorber 65 via a blower 67 following the flue gas cooler 63.

(20) The second absorber 65 serves for separating the carbon dioxide contained in the flue gas. For this purpose, the flue gas is brought into contact with the absorption medium 55 in the second absorber 65, and the CO.sub.2 contained in the flue gas is absorbed by the absorption medium 55. Here, too, the absorption medium 55 serves likewise for absorbing the hydrogen sulfide from the natural gas stream before combustion and for absorbing the carbon dioxide from the flue gas after combustion. Correspondingly, the first absorber 53 and the second absorber 65 are flow-connected to one another for the exchange of the absorption medium 55.

(21) The flow connection is ensured in that the delivery line 69 of the first absorber 53 is connected to a discharge line 71 of the second absorber 65. The exchange of the absorption medium 55 between the two absorbers 53, 65 can thus take place.

(22) In addition to the delivery line 69, the first absorber 53 comprises a discharge line 73 which is flow-connected to the delivery line 75 of a first desorber 77. Laden absorption medium 55 can flow out of the first absorber 53 via the discharge line 73 and, after passing through a heat exchanger 79, into the first desorber 77 and can be regenerated there.

(23) In contrast to the device 1 according to FIG. 1, however, the first desorber 77 is used essentially for the desorption of hydrogen sulfide out of the absorption medium 55. The carbon dioxide absorbed in the absorption medium 55 is desorbed in a separate second desorber 81. In order to ensure that essentially the hydrogen sulfide is desorbed in the first desorber 77 and essentially the carbon dioxide is desorbed in the second desorber 81, the desorption conditions within the respective desorbers 77, 81 are selected correspondingly. This may be achieved, in particular, by the targeted choice of the absorption medium 55 and/or the temperature within the respective desorber 77, 81.

(24) In order to allow desorption of H.sub.2S and CO.sub.2 in two separate desorbers, the discharge line 71 of the second absorber 65 has connected to it a branch line 83, via which the second absorber 65 is flow-connected to the second desorber 81.

(25) Part of the CO.sub.2-laden absorption medium 55 is delivered from the absorber sump of the second absorber 65, and via its discharge line 71, to the first absorber 53. The absorption medium 55 is used there for the absorption of hydrogen sulfide and is finally delivered to the first desorber 77 for regeneration. The first desorber 77 is thus designed essentially as an H.sub.2S absorber.

(26) Another part of the absorption medium 55 flows through the branch line 83 to the second desorber 81. In this case, the absorption medium 55 likewise passes through a heat exchanger 84 in which the heat of the regenerated absorption medium 55 flowing from the desorber 81 to the second absorber 65 is transferred to the laden absorption medium 55 delivered by the second absorber 65.

(27) Since the absorption medium 55 flowing to the second desorber 81 is laden essentially only with CO.sub.2, the second desorber 81 is designed essentially as a CO.sub.2 absorber. In the present case, the two desorbers 77, 81 are each designed with a treatment apparatus 85, 87 for the further use and/or storage of the desorbed components.

(28) For the further use of the regenerated absorption medium 55, the two desorbers 77, 81 are each provided with a recirculation line 89, 91. The two recirculation lines 89, 91 are flow-connected to the delivery line 93 of the second absorber 65, so that the regenerated absorption medium 55 can be delivered from the two desorbers 77, 81 to the second absorber 65 for further use.

(29) In addition, the two desorbers 77, 81 are each provided with a reboiler 95, 97 which supplies the necessary regeneration heat for separating CO.sub.2 and H.sub.2S from the absorption medium 55. The laden absorption medium 55 is in this case regenerated by steam which is generated in the respective reboilers 95, 97.

(30) FIG. 3 shows a further device 101 which serves for the treatment of a natural gas stream (EG) by the absorption of hydrogen sulfide (H.sub.2S) and of carbon dioxide (CO.sub.2). Since the device 101 corresponds essentially to the device 51 according to FIG. 2, the respective components of the device 101 are given the same reference symbols as the components of the device 51. The detailed description of the device 51 may also be transferred accordingly to the device 101 according to FIG. 3.

(31) The difference between the device 101 and the device 51 according to FIG. 2 is the thermal coupling of the two desorbers 77, 81. Coupling between the first desorber 77 and the second desorber 81 takes place via a heat exchanger 103. The heat exchanger 103 is incorporated in the discharge line 105 of the first desorber 77 and serves for heating the reboiler 97 of the second desorber 81. The reboiler 97 is therefore in this case not heated by imported steam, but instead uses the waste heat of the first desorber 77.

(32) Overall, all the devices 1, 51, 101 according to FIGS. 1, 2 and 3 and the methods which can be carried out by means of these devices 1, 51, 101 afford the possibility of obtaining at low cost and at a low outlay in terms of process technology raw materials contained in hitherto scarcely utilized natural gas streams, with undesirable emissions harmful to climate being largely avoided, and of processing these raw materials further, depending on the application.

(33) Furthermore, the use of the same absorption medium 5, 55 for the absorption both of H.sub.2S before combustion (pre-combustion capture) and of CO.sub.2 after combustion (post-combustion capture) makes it possible to have cost-effective operation at a low outlay in terms of process technology.