DE102021214785A1 - Carbon Dioxide Separation Device - Google Patents

Abstract

The present invention relates to a carbon dioxide separation device 10, the carbon dioxide separation device 10 having an absorption device 20 and a desorption device 30, the absorption device 20 having a gas inlet 21 for the gas to be cleaned and a gas outlet 22 for the cleaned gas, the absorption device 20 has an absorption solvent inlet 23 and a solution outlet 24, the desorption device 30 having at least a first solution inlet 31, an absorption solvent outlet 32, a warm solvent inlet 33 and a carbon dioxide outlet 34, the solution outlet 24 being connected to the first solution inlet 31 via a first solution connection 40, the first solution connection 40 having a first heat exchanger 41, the absorption solvent outlet 32 being connected to the absorption solvent inlet 23 via an absorption solvent connection 50, the absorption solvent connection 50 having the first heat exchanger 41 such that the heat of the solvent stream is transferred to the solution stream, the absorption solvent connection 50 has a branch 51 to a warm solvent connection 52 , the warm solvent connection 52 being connected to the warm solvent inlet 33 , the warm solvent connection having a second heat exchanger 53 .

Description

The invention relates to a device for separating carbon dioxide from gases, in particular from exhaust gases.

In order to reduce man-made climate change, carbon dioxide emissions into the atmosphere are increasingly being avoided. Instead, attempts are being made to separate the carbon dioxide that is produced and then either convert it or dump it. A typical method for this is to scrub exhaust gases at about 25°C to 50°C with a basic solution, for example an amine solution. This amine solution acts as a solvent in which the carbon dioxide dissolves. The solution containing the carbon dioxide is then heated and the carbon dioxide is converted back into the gas phase in a desorption step. This recovers the solvent and also produces a pure carbon dioxide gas stream. The carbon dioxide gas stream can then, for example and purely by way of example, be deposited or fed to a methanol synthesis.

From the WO 2010 / 086 039 A1 a method and a device for separating carbon dioxide from an exhaust gas of a fossil-fired power plant are known.

From the CN 111203086A a CO ₂ capture system with low energy consumption and low emissions is known.

From the WO 2014 / 077 919 A1 discloses an apparatus and method for removing acidic gases from a gas stream and regenerating the absorbing solution.

From the U.S. 2017/0197175 A1 an energy-efficient process for extracting acidic gas from a gas stream is known.

From the WO 2013/013 749 A1 heat recovery in absorption and desorption processes is known.

From the WO 2019 / 232 626 A1 CO ₂ separation after combustion with heat recovery is known.

From the U.S. 2021/0220771 A1 carbon dioxide separation with heat recovery downstream of incineration is known.

From the CN 208786105 U carbon dioxide separation with heat recovery is known.

From the U.S. 2014/0127119 A1 a carbon dioxide absorber is known.

From the U.S. 5,145,658 A it is known to recover the heat of reaction of an alkaline scrubbing solution to remove acidic gases.

From the U.S. 3,563,696 A the removal of carbon dioxide from a gas mixture is known.

From the WO 2004/080 573 A1 the regeneration of an aqueous solution from a gas absorption process is known.

From the U.S. 2014/0374105 A1 a method for removing carbon dioxide from a gas is known.

What all systems for separating CO ₂ have in common is that energy must be supplied to release the CO ₂ from the solution again. For this purpose, heat is used at a high and thus comparatively valuable level.

The object of the invention is to provide a carbon dioxide separation device in which the overall process of absorption and desorption is energetically optimized.

This object is achieved by the carbon dioxide separation device having the features specified in claim 1. Advantageous developments result from the dependent claims, the following description and the drawings.

The carbon dioxide separation device according to the invention has an absorption device and a desorption device. The gas to be cleaned of carbon dioxide is introduced into the absorption device and the carbon dioxide is converted from the gas phase into the liquid phase by contact with a solvent, usually an amine solution. A solution is formed from the solvent with the carbon dioxide dissolved therein, which may be bound. This solution is transferred to the desorption device where the carbon dioxide is stripped out of the solution, thereby recovering the solvent and being recycled back to the absorption device. Likewise, a carbon dioxide gas stream is obtained, which can be supplied for further use. This basic principle is already used in a large number of variations.

The absorption device has a gas inlet for the gas to be cleaned and a gas outlet for the cleaned gas. The gas to be cleaned can be, for example, an exhaust gas from the combustion of fossil fuels. The cleaned gas would then mostly be mainly nitrogen with a small remainder of carbon dioxide and possibly a greatly reduced proportion of oxygen due to the combustion process. The cleaned gas can then be released into the atmosphere, for example, without releasing large amounts of carbon dioxide as a greenhouse gas. The absorption device usually has one or more mass transfer elements which are arranged between the gas inlet and the absorption solvent inlet. The mass transfer elements serve to bring the liquid and the gaseous phase into better contact, in particular also to increase the surface area of the liquid phase. Such mass transfer elements are known to those skilled in the art and can, for example, be bubble-cap trays, random packings or structured packing

The absorption device further includes an absorption solvent inlet and a solution outlet. The absorption solvent inlet is usually located at the top of the absorption device, the solution outlet at the bottom of the absorption device. Correspondingly, the gas inlet is usually arranged at the bottom and the gas outlet at the top, so that the gas and solvent flow countercurrently through the absorption device.

The desorption device has at least a first solution inlet, an absorbent solvent outlet, a warm solvent inlet, and a carbon dioxide outlet. The solution outlet of the absorption device is connected to the first solution inlet of the desorption device via a first solution connection. The first solution compound has a first heat exchanger. As a result, the solution stream which flows through the first solution connection is heated, so that the carbon dioxide present in the solution can be emitted again in the desorption device. The absorption solvent outlet of the desorption device is connected to the absorption solvent inlet of the absorption device via an absorption solvent connection. The solvent depleted of carbon dioxide in the desorption device flows back to the absorption device via the absorption solvent connection. The absorption solvent compound also has the first heat exchanger. This transfers the heat of the solvent flow to the solution flow in the absorption solvent connection. The absorption solvent junction has a branch to a warm solvent junction. A partial flow of the solvent flow is therefore branched off and fed into the warm solvent connection. The warm solvent connection is connected to the warm solvent inlet. The warm solvent compound has a second heat exchanger. As a result, additional energy can be introduced into the entire system. The desorption device usually has one or more mass transfer elements which are arranged above and below the first solution inlet. The mass transfer elements serve to bring the liquid and the gaseous phase into better contact, in particular also to increase the surface area of the liquid phase. Such mass transfer elements are known to those skilled in the art and can, for example, be bubble-cap trays, random packings or structured packing.

According to the invention, a third solution connection branches off between the absorption device and the first heat exchanger of the first solution connection. The third solution connection is fluidly connected to the first solution connection after the first heat exchanger or absorption device at the end where the solution flow exits the third solution connection again. The third solution compound has a fourth heat exchanger in which the solution stream of the third solution compound is heated. The fourth heat exchanger and the gas inlet are connected via a gas connection, so that the gas to be cleaned is passed through the fourth heat exchanger before the gas to be cleaned is passed into the absorption device. The gas to be cleaned is usually provided at a temperature between 100° C. and 200° C., for example at 150° C., depending on how it is obtained from the preliminary processes. Temperatures of 30°C to 40°C are common in the absorption device, a heat exchanger is normally required for cooling. However, the heat generated here can often no longer be used, since it occurs at a very low level. Due to the direct heat transfer, the energy can be transferred directly to the solution stream, which is brought to, for example, 100° C. to 110° C. and thus to the temperature level of the desoption device. As a result, the energy supplied to the second heat exchanger, which comes from a higher-value energy source, usually steam, can be saved at least in part.

In a further embodiment of the invention, the first solution connection has an evaporation device downstream of the first heat exchanger in terms of flow. The evaporation device, also known as the pressure expansion tank, is used to allow the solution of the solution stream heated in the first heat exchanger to expand and therefore partially evaporate. The liquid phase of the solution stream is thus separated from the gaseous phase of the solution stream in the evaporation device. The liquid phase is led into the desorption device through the first solution connection. The desorptions The device further has a vapor inlet and the vaporization device has a vapor outlet. The vapor outlet of the evaporation device and the vapor inlet of the desorption device are connected to a gas solution connection for transfer of the gaseous phase. The steam inlet is particularly preferably arranged in the lower area of the desorption device. This optimizes the energetic management of the overall process.

In a further embodiment of the invention, the third solution connection is connected to the evaporation device at the end where the solution stream emerges again from the third solution connection. In this way, as in the case of the heated solution stream of the first solution compound, expansion can take place here and the gas phase can be separated from the liquid phase.

In a further embodiment of the invention, the gas connection has a raw gas cleaning system. In particular and preferably, the raw gas cleaning is designed to remove sulfur oxides.

In a further embodiment of the invention, a second solution connection branches off between the absorption device and the first heat exchanger of the first solution connection. The second solution connection leads directly to the top of the desorption device. In this context, directly means without a heat exchanger or the like. If necessary, a (flow control) valve can be arranged here. The solution loaded with carbon dioxide is thus itself used to cool the gas stream exiting the desorption device. As a result, the heat supplied from the first heat exchanger and the second heat exchanger into the desorption device remains in the desorption device and the solvent and is not released to a cooling medium.

In a further embodiment of the invention, a fourth solution connection branches off between the absorption device and the first heat exchanger of the first solution connection. The fourth solution connection is connected to the first solution connection after the first heat exchanger or absorption device at the end where the solution flow exits the fourth solution connection again. The fourth solution compound has a fifth heat exchanger. The fifth heat exchanger is connected to the second heat exchanger in such a way that the heat exchange medium cooled in the second heat exchanger is fed into the fifth heat exchanger. As a result, the maximum amount of thermal energy can be obtained from the heat exchange medium, usually steam, and the overall energy requirement can thus be reduced in turn.

In a further embodiment of the invention, the fourth solution connection is connected to the evaporation device at the end where the solution stream exits the fourth solution connection again. In this way, as in the case of the heated solution stream of the first solution compound, expansion can take place here and the gas phase can be separated from the liquid phase.

In another embodiment of the invention, the carbon dioxide outlet is connected to a first carbon dioxide compressor. The first carbon dioxide compressor is connected to a first carbon dioxide heat exchanger in order to cool down the carbon dioxide heated by the compression again. This is common, since the carbon dioxide is required at a higher pressure both for dumping and for the further processing of carbon dioxide, for example to form methanol. For this purpose, a plurality of carbon dioxide compressors and carbon dioxide heat exchangers are usually connected in series in a cascaded manner in order to compress the carbon dioxide in stages and to cool it again and again in between. A fifth solution connection branches off between the absorption device and the first heat exchanger of the first solution connection. The fifth solution connection is connected to the first solution connection after the first heat exchanger or absorption device at the end where the solution flow exits the fifth solution connection again. The fifth solution compound includes the first carbon dioxide heat exchanger. This allows the thermal energy generated by compressing the carbon dioxide to be used for the process. If there is a plurality of carbon dioxide heat exchangers, these are preferably integrated in parallel into the fifth solution compound.

In a further embodiment of the invention, the fifth solution connection is connected to the evaporation device at the end where the solution stream emerges again from the fifth solution connection. In this way, as in the case of the heated solution stream of the first solution compound, expansion can take place here and the gas phase can be separated from the liquid phase.

In a further embodiment of the invention, the pressure of the solvent in the second heat exchanger is 0.2 bar to 5 bar higher than the pressure in the desorption device at the absorption solvent outlet. In the second heat exchanger thus a higher starting temperature can be achieved, since the increased pressure can increase the temperature up to the boiling point at the corresponding pressure. This in turn means that the solvent has a higher temperature at the absorption solvent outlet and thus reaches the first heat exchanger at a higher temperature. As a result, it can either be made more compact or a higher outlet temperature can be achieved for the loaded solution stream from the first heat exchanger. The latter in turn leads to more efficient expulsion of the carbon dioxide from the solution.

Here, the pressure of the solvent in the second heat exchanger is dependent on the equipment. There are two exemplary and preferred embodiments for setting the pressure in a targeted manner using equipment. In a first exemplary and preferred embodiment of the invention, the pressure of the solvent in the second heat exchanger is higher by 0.2 bar to 5 bar than the pressure in the desorption device at the absorption solvent outlet in that the second heat exchanger is arranged at least 1 m below the absorption solvent outlet, whereby the pressure in the second heat exchanger is generated by the hydrostatic pressure of the liquid column of the solvent. In a second exemplary and preferred embodiment of the invention, the pressure of the solvent in the second heat exchanger is 0.2 bar to 5 bar higher than the pressure in the desorption device at the absorption solvent outlet by arranging a first pump upstream of the second heat exchanger to generate the corresponding overpressure is.

In a further embodiment of the invention, a pressure loss device, for example a control valve, an orifice plate or a tube constriction, is arranged between the second heat exchanger and the desorption device. With the pressure loss device, the desired overpressure is set or maintained in the second heat exchanger on the gas/steam side. In this way, if necessary, evaporation can already be prevented in the second heat exchanger.

The first solution inlet is preferably arranged in the middle region of the desorption device.

• 1 erste beispielhafte Ausführungsform
• 2 zweite beispielhafte Ausführungsform
• 3 dritte beispielhafte Ausführungsform

The carbon dioxide separation device according to the invention is explained in more detail below with reference to exemplary embodiments illustrated in the drawings.

• 1 first exemplary embodiment
• 2 second exemplary embodiment
• 3 third exemplary embodiment

In 1 a first exemplary embodiment of a carbon dioxide separation device 10 according to the invention is shown. The carbon dioxide separation device 10 is used, for example, to separate the carbon dioxide from an exhaust gas stream, which enters the gas inlet 21 and leaves the gas outlet 22 greatly depleted in carbon dioxide. In the absorption device 20, this gas flow is brought into contact with a solvent, usually an amine solution, in countercurrent, so that the carbon dioxide dissolves. This solution exits the absorption device at the solution outlet 24 and is pumped through the first solution connection 40 by a second pump 46 . The first solution compound 40 has a first heat exchanger 41 in which the solution flow is heated by the solvent flow of the absorption solvent compound 50 . Downstream of the first heat exchanger 41 is an evaporation device 42 in which the solution can partially convert into the gas phase. The liquid phase of the solution stream is conveyed further through the first solution connection 40, for example by means of a third pump 47 through the first solution inlet 31 into the desorption device 30. The gas produced in the evaporation device 42 is conducted through the vapor outlet 43 into the gas dissolving connection 44 and through this via the vapor inlet 35 into the desorption device 30 . The steam inlet 35 is preferably located at the lower end, the bottom, of the desorption device 30.

In the desorption device 30 the carbon dioxide is thermally removed from the solution and discharged via the carbon dioxide outlet 34 . This carbon dioxide stream can then be fed, for example, either to a further reaction or to landfill. The solvent freed from carbon dioxide collects at the bottom of the desorption device 30 and is supplied to the absorption solvent joint 50 through the absorption solvent outlet 32 . The solvent flow transfers its thermal energy to the solution flow in the first heat exchanger 41 . For example, by means of a fourth pump, the solvent stream reaches the absorption device via a third heat exchanger 55 through the absorption solvent inlet 23 .

A partial flow branches off from the solvent flow in the absorption solvent connection 50 at the junction 51 and is conveyed through the warm solvent connection 52 via the second heat exchanger 53, in particular in vapor form or as a vapour/liquid mixture, through the warm solvent inlet 33 back into the desorption device 30. The energy required for expelling the carbon dioxide from the solution is supplied to the system via the second heat exchanger 53 .

A third solution connection 60 , which has a fourth heat exchanger 61 , also branches off from the first solution connection 40 . The third solution connection 60 opens into the evaporation device 42 at the end. The energy, which is transferred to the solution flow in the fourth heat exchanger 61, comes from the gas flow to be cleaned of carbon dioxide. In order to then transfer this gas stream into the absorption device 20 , the fourth heat exchanger 61 and the gas inlet 21 of the absorption device 20 are connected via the gas connection 25 . The gas connection 25 also has a raw gas cleaning 26, in which SO _x is removed and also brings the gas flow to the right temperature for the absorption of the carbon dioxide in the absorption device 20.

2 shows a second exemplary embodiment, which differs from the first exemplary embodiment in that a fourth solution connection 62 is also present, which leads a partial flow of the solution flow in via the fifth heat exchanger 63 into the evaporation device 42. The energy for heating the solution stream in the fifth heat exchanger 63 comes from the heat exchange medium that has already been cooled in the second heat exchanger 53, and whose residual heat is used efficiently as a result.

In 3 a third exemplary embodiment is shown. In addition to the second exemplary embodiment, FIG. In order to use the heat generated by the compression and given off in the carbon dioxide heat exchanger 37 , the carbon dioxide separation device 10 has a fifth solution connection 64 which leads a partial flow of the solution flow through the carbon dioxide heat exchanger 37 into the evaporation device 42 .

Reference List

10

Carbon Dioxide Separation Device

20

absorption device

21

gas inlet

22

gas outlet

23

absorption solvent inlet

24

solution outlet

25

gas connection

26

Raw gas cleaning30 desorption device

31

first solution inlet

32

absorption solvent outlet

33

warm solvent inlet

34

carbon dioxide outlet

35

steam inlet

36

carbon dioxide compressor

37

carbon dioxide heat exchanger

40

first solution connection

41

first heat exchanger

42

vaporizing device

43

steam outlet

44

gas solution compound

45

second solution compound

46

second pump

47

third pump

50

absorption solvent compound

51

junction

52

warm solvent compound

53

second heat exchanger

54

first pump

55

third heat exchanger

60

third solution compound

61

fourth heat exchanger

62

fourth solution compound

63

fifth heat exchanger

64

fifth solution connection

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• WO 2010086039 A1 [0003]
• CN 111203086A [0004]
• WO 2014077919 A1 [0005]
• US20170197175A1 [0006]
• WO 2013013749 A1 [0007]
• WO 2019232626 A1 [0008]
• US20210220771A1 [0009]
• CN 208786105 U [0010]
• US20140127119A1[0011]
• US5145658A [0012]
• US 3563696 A [0013]
• WO 2004080573 A1 [0014]
• US20140374105A1 [0015]

Claims (13)

Carbon dioxide separation device (10), wherein the carbon dioxide separation device (10) has an absorption device (20) and a desorption device (30), the absorption device (20) having a gas inlet (21) for the gas to be cleaned and a gas outlet (22) for the cleaned gas, wherein the absorption device (20) has an absorption solvent inlet (23) and a solution outlet (24), wherein the desorption device (30) has at least a first solution inlet (31), an absorption solvent outlet (32), a warm solvent inlet (33) and a carbon dioxide outlet (34), said solution outlet (24) being connected to said first solution inlet (31) via a first solution connection (40), said first solution connection (40) having a first heat exchanger (41), said absorption solvent outlet ( 32) connected to the absorption solvent inlet (23) via an absorption solvent connection (50), the absorption solvent connection (50) having the first heat exchanger (41) such that the heat of the solvent flow is transferred to the solution flow, the absorption solvent connection (50) having a branch (51) to a warm solvent connection (52), the warm solvent connection (52) being connected to the warm solvent inlet (33), the warm solvent connection having a second heat exchanger (53), characterized in that between the absorption device (20) and the first heat exchanger (41) a third solution connection (60) branches off from the first solution connection (40), the third solution connection (60) being connected at the end to the first solution connection (40) downstream of the first heat exchanger (41) or the absorption device (20). , wherein the third solution connection (60) has a fourth heat exchanger (61), wherein the fourth heat exchanger (61) and the gas inlet (21) are connected via a gas connection (25), so that the gas to be cleaned through the fourth heat exchanger (61) is passed before the gas to be cleaned is fed into the absorption device (10). Carbon dioxide separation device (10) after claim 1 , characterized in that the first solution connection (40) downstream of the first heat exchanger (41) has an evaporation device (42), the liquid phase of the solution stream being separated from the gaseous phase of the solution stream in the evaporation device (42), the liquid phase is conducted through the first solution connection (40) into the desorption device (30), the desorption device (30) having a vapor inlet (35), the evaporation device (42) having a vapor outlet (43), the vapor outlet (43) and the vapor inlet (35) is connected to a gas dissolving connection (44) for transferring the gaseous phase. Carbon dioxide separation device (10) after claim 2 , characterized in that the third solution connection (60) is connected at the end to the evaporation device (42). Carbon dioxide separation device (10) according to one of the preceding claims, characterized in that the gas connection (25) has a raw gas cleaning system (26). Carbon dioxide separation device (10) after claim 4 , characterized in that the raw gas cleaning (25) is designed to remove sulfur oxides. Carbon dioxide separation device (10) according to one of the preceding claims, characterized in that between the absorption device (20) and the first heat exchanger (41) a second solution connection (45) branches off from the first solution connection (40), the second solution connection (45 ) leads directly into the head of the desorption device (30). Carbon dioxide separation device (10) according to one of the preceding claims, characterized in that between the absorption device (20) and the first heat exchanger (41) a fourth solution connection (62) branches off from the first solution connection (40), the fourth solution connection (62 ) is connected at the end to the first solution connection (40) after the first heat exchanger (41) or the absorption device (20), the fourth solution connection (62) having a fifth heat exchanger, the fifth heat exchanger (63) being so connected to the second heat exchanger (53) is connected in that the heat exchange medium cooled in the second heat exchanger (53) is fed into the fifth heat exchanger (63). Carbon dioxide separation device (10) after claim 7 combined with claim 2 , characterized in that the fourth solution connection (62) is connected at the end to the evaporation device (42). Carbon dioxide separation device (10) according to any one of the preceding claims, characterized in that the carbon dioxide outlet (34) is connected to a first carbon dioxide compressor (36), the first carbon dioxide compressor (36) being connected to a first carbon dioxide heat exchanger (37) between which absorption tion device (20) and the first heat exchanger (41) a fifth solution connection (65) branches off from the first solution connection (40), the fifth solution connection (65) at the end with the first solution connection (40) behind the first heat exchanger (41) or the absorption device (20) is connected, wherein the fifth solution connection (65) comprises the first carbon dioxide heat exchanger (37). Carbon dioxide separation device (10) after claim 9 combined with claim 2 , characterized in that the fifth solution connection (65) is connected at the end to the evaporation device (42). Carbon dioxide separation device (10) according to any one of the preceding claims, characterized in that the pressure of the solvent in the second heat exchanger (53) is 0.2 bar to 5 bar higher than the pressure in the desorption device (30) at the absorption solvent outlet (32) . Carbon dioxide separation device (10) after claim 11 , characterized in that the pressure of the solvent in the second heat exchanger (53) is 0.2 bar to 5 bar higher than the pressure in the desorption device (30) at the absorption solvent outlet (32), characterized in that the second heat exchanger (53) by at least 1 m below the absorption solvent outlet (32) so that the pressure is generated by the hydrostatic pressure of the solvent. Carbon dioxide separation device (10) after claim 11 , characterized in that the pressure of the solvent in the second heat exchanger (53) is thereby 0.2 bar to 5 bar higher than the pressure in the desorption device (30) at the absorption solvent outlet (32), that before the second heat exchanger (53) a first pump (54) is arranged to generate the excess pressure.

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