DEVICE AND METHOD FOR SEPARATING CARBON DIOXIDE FROM A GAS FLOW

Abstract

A device for separating carbon dioxide from a gas flow, in particular from a flue gas flow, having an absorption unit for separating carbon dioxide from the gas flow using a scrubbing medium, a desorption unit which is fluidically connected to the absorption unit for releasing the absorbed carbon dioxide from the scrubbing medium, and a compressor unit which is connected fluidically downstream of the desorption unit for compressing the released carbon dioxide, the compressor unit being connected fluidically upstream of a cleaning device for the carbon dioxide. A method separates carbon dioxide from a gas flow, in particular from a flue gas flow.

Claims

1.-16. (canceled)

17. An apparatus for removing carbon dioxide from a gas stream, comprising: an absorption unit for separating carbon dioxide from the gas stream by a scrubbing medium; a desorption unit connected fluidically to the absorption unit and adapted for liberating the absorbed carbon dioxide from the scrubbing medium; a compressor unit located fluidically downstream of the desorption unit and adapted for compressing the liberated carbon dioxide; and a purification apparatus for the carbon dioxide, for removing oxygen present in the liberated carbon dioxide, which is located fluidically upstream of the compressor unit.

18. The removal apparatus of claim 17, wherein the purification apparatus is designed for catalytic reduction of the oxygen present in the carbon dioxide.

19. The removal apparatus of claim 17, wherein a discharge line of the desorption unit and a feed line for a hydrogen-containing gas are connected to a feed line of the purification apparatus.

20. The removal apparatus of claim 18, wherein the purification apparatus comprises a reactor having a catalytically active material.

21. The removal apparatus of claim 20, wherein the purification apparatus comprises a cooler fluidically between the reactor and the compressor unit.

22. The removal apparatus of claim 20, wherein the purification apparatus comprises a drying apparatus fluidically between the reactor and the compressor unit.

23. A method for removing carbon dioxide from a gas stream, comprising: feeding a gas stream comprising carbon dioxide to an absorption unit, wherein carbon dioxide present in the gas stream is removed therefrom by a scrubbing medium, feeding the scrubbing medium laden with carbon dioxide to a desorption unit, wherein the carbon dioxide absorbed in the scrubbing medium is liberated therefrom, and feeding the liberated carbon dioxide prior to compression to a purification apparatus, wherein oxygen present in the carbon dioxide is removed from the liberated carbon dioxide.

24. The method of claim 23, wherein oxygen present in the carbon dioxide is reduced catalytically in the purification apparatus.

25. The method of claim 24, wherein hydrogen is metered into the purification apparatus for catalytic reduction of the oxygen present in the carbon dioxide.

26. The method of claim 24, wherein the catalytic reduction takes place by a catalytically active material.

27. The method of claim 23, wherein the carbon dioxide reduced of the oxygen is cooled, and water eliminated in this process is drawn off.

28. The method of claim 27, wherein the cooled carbon dioxide is dried.

29. The method of claim 28, wherein the cooled and/or dried carbon dioxide is compressed.

30. The removal apparatus of claim 17, wherein the gas stream comprises a flue gas stream.

31. The removal apparatus of claim 22, wherein the purification apparatus comprises a drying apparatus fluidically between the cooler and the compressor unit.

32. The method of claim 23, wherein the gas stream comprises a flue gas stream.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Below, exemplary embodiments of the invention are illustrated with a drawing. In the drawing

[0037] FIG. 1 shows an apparatus for removing carbon dioxide from a flue gas stream, with a schematic purification apparatus, and

[0038] FIG. 2 shows a purification apparatus suitable for a removal apparatus in accordance with FIG. 1.

DETAILED DESCRIPTION OF INVENTION

[0039] FIG. 1 shows an apparatus 1 for removing carbon dioxide from a flue gas stream. This removal apparatus 1 comprises an absorption unit 3 and a desorption unit 5.

[0040] A flue gas 8 for purification flows via a flue gas line 7 into the absorption unit 3. Within the absorption unit 3, the flue gas 8 is contacted with a scrubbing medium 9, and carbon dioxide present in the flue gas 8 is absorbed by the scrubbing medium 9. An aqueous amino acid salt solution is the scrubbing medium 9 used. The purified flue gas is discharged into the atmosphere via a discharge line 11 at the top 13 of the absorption unit 3.

[0041] The scrubbing medium 9 laden with carbon dioxide is taken off via a discharge line 17 connected at the bottom 15 of the absorption unit 3. Via a fluidic coupling or communication of the discharge line 17 with a feed line 19 of the desorption unit 5, the laden scrubbing medium 9 is fed to the desorption unit 5. In this case the scrubbing medium 9 passes through a heat exchanger 21.

[0042] Within the desorption unit 5, the carbon dioxide is liberated from the scrubbing medium 9 again by thermal desorption. By way of the fluidic communication between a discharge line 23 connected to the desorption unit 5 and a feed line 25 of the absorption unit 3, the scrubbing medium 9, freed from carbon dioxide, is returned to the absorption unit 3, where it is available for renewed absorption of carbon dioxide from a flue gas 8. Connected additionally to the desorption unit 5 is a reboiler 27, which as a bottoms vaporizer supplies part of the regeneration heat for the liberation of the carbon dioxide absorbed in the scrubbing medium 9.

[0043] The carbon dioxide released from the scrubbing medium 9 within the desorption unit 5 is taken from said unit at the head 29 of the desorption unit 5, via a discharge line 31 which is connected there, and the carbon dioxide passes through a condenser 33. The carbon dioxide stream also contains small amounts of oxygen, which must be removed from the gas stream. For this purpose, a purification apparatus 35 is located fluidically downstream of the desorption unit 5, and communicates via a feed line 37 with the discharge line 31 of the desorption unit 5.

[0044] In the purification apparatus 35, the oxygen present in the carbon dioxide is removed. Only after the purification, which is described comprehensively in FIG. 2, is the carbon dioxide fed to a compressor unit 39, where it is compressed.

[0045] In other words, the purification apparatus 35 is located fluidically between the desorption unit 3 and the compressor unit 39, and so the carbon dioxide stream leaving the desorption unit 5 is fed in uncompressed form to the purification apparatus 35.

[0046] Within the purification apparatus 35, which is shown in FIG. 2, the oxygen present in the carbon dioxide stream is removed. This is accomplished by catalytic reduction of the oxygen present in the carbon dioxide stream, using hydrogen, over a catalytically active surface.

[0047] The oxygen-containing carbon dioxide stream is fed to the purification apparatus 35 by way of the fluidic communication of the discharge line 31 of the desorption unit 5 and of the feed line 37 of the purification apparatus 35.

[0048] For the metering of the hydrogen, a feed line 41 for a hydrogen-containing gas is connected to the feed line 37 of the purification apparatus 35. After passing through a preheater 43, the hydrogen-containing gas flows together with the oxygen-containing carbon dioxide stream into the reactor 45, which as part of the purification apparatus 35 is located fluidically downstream of the desorption unit 5.

[0049] The reactor 45 is charged with a catalytically active material 47. In the present case, platinum meshes are used. The surface of the mesh structure provides the catalytically active surface over which the catalytic oxidation of the hydrogen, or catalytic reduction of the oxygen, takes place. In this process, water is formed, and flows out of the reactor 45 together with the carbon dioxide via a discharge line 49 of said reactor.

[0050] Disposed in the discharge line 49 is a cooler 51, in which the water is condensed out and drawn off via a corresponding offtake line 53. For the final drying, the carbon dioxide emerging from the cooler 51 is passed further to a drying apparatus 55, where the water fraction in the carbon dioxide is reduced to below 1 ppmv by adsorption of the water still present.

[0051] Only after purification has taken place, in other words after there has been passage through the reactor 45, the cooler 51, and the drying apparatus 55, is the carbon dioxide fed to the compressor unit 39 shown in FIG. 1. For this purpose, the purification apparatus 35 is coupled fluidically via a discharge line 57 to a feed line 59 of the compressor unit 39.