Facility and method for liquefying carbon dioxide

Abstract

The invention relates to a facility (1) for liquefying carbon dioxide, comprising a compressor unit having an inflow (2) for a carbon dioxide-containing medium, which is supplied at a pressure pinlet and a temperature Tinlet, said compressor unit being designed in such a way that the carbon dioxide-containing medium is compressed and flows out of the compressor unit at an outflow opening under a pressure pcompressor and at a temperature Tcompressor. The compressor unit has at least one liquefaction compressor stage (3, 9, 15), and a liquefaction heat exchanger (5, 11, 17) is provided downstream of the liquefaction compressor stage (3, 9, 15) and is fluidically coupled to the liquefaction compressor stage (3, 9, 15). The compressor unit also has at least one cooling compressor stage (22, 28) which is designed in such a way that the temperature and the pressure of a cooling medium flowing through the cooling compressor stage (22, 28) are increased. A cooling heat exchanger (24) is provided downstream of the cooling compressor stage (22, 28), said cooling heat exchanger being fluidically coupled to the cooling compressor stage (22, 28), and the cooling heat exchanger (24) is designed in such a way that a second cooling medium flows through the cooling heat exchanger (24) and, by means of a thermal contact, the temperature of the cooling medium is lowered and the temperature of the second cooling medium is increased. The liquefaction heat exchanger (5, 11, 17) is designed in such a way that the cooling medium cooled in the cooling heat exchanger (24) flows through the liquefaction heat exchanger (5, 11, 17) and, by means of a thermal contact, the temperature of the medium is lowered and the temperature of the cooling medium is increased.

Description

Description TITLE Plant and process for the liquefaction of carbon dioxide TECHNICAL FIELD

[0001] The invention relates to a plant for liquefying carbon dioxide, comprising a compressor unit with an inflow for a medium containing carbon dioxide, which is at a pressure p inlet and a temperature T inlet, wherein the compressor unit is designed such that the medium containing carbon dioxide is compressed and flows out of the compressor unit at an outflow opening at a pressure p compressor and a temperature T compressor. BACKGROUND

[0002] It is well known that carbon dioxide (CO2) emissions pose a significant threat to global climate change. Therefore, efforts are underway to avoid carbon dioxide production or at least capture the carbon dioxide during production and store it in a future-proof manner. This would require transporting the captured carbon dioxide.

[0003] Transporting captured carbon dioxide for storage or further use presents a challenge, especially over long distances. One option for transporting carbon dioxide would be to provide pipelines, although suitable pipelines are currently scarce.

[0004] To capture carbon dioxide from flue gases, so-called amine plants are suitable, and are currently considered a commercially and industrially successful technology. Amine systems require significant amounts of low-pressure steam or heat to carry out the process. The carbon dioxide captured in an amine system is delivered at low pressure.

[0005] After carbon dioxide capture, the carbon dioxide is typically transported to a storage reservoir or for further utilization. An economically viable solution would be to transport the carbon dioxide via pipelines in a supercritical phase. However, relatively few suitable pipelines are available, and the construction of new pipelines would be a significant time commitment, potentially taking up to ten years. A rapid way to transport carbon dioxide would therefore be to transport liquefied carbon dioxide.

[0006] Carbon dioxide can be liquefied using cryogenic processes at low temperatures and low pressures. The liquefied carbon dioxide can then be transported by truck, rail, or ship.

[0007] Thus, a modern application involves using a separate cryogenic refrigerant liquefaction circuit to liquefy the carbon dioxide after compression to the required pressure. This requires two separate compression trains, one for carbon dioxide compression and the other for the cryogenic refrigerant circuit. A commonly used refrigerant is ammonia, which, however, requires careful consideration due to its toxicity. When carbon dioxide is liquefied, there is a loss of compression energy between the compressor stages, which affects the overall efficiency of a plant. It is desirable to provide a carbon dioxide liquefaction plant that has low investment costs and low process complexity. SUMMARY OF THE INVENTION

[0010] The object of the present invention is therefore to provide a plant for liquefying carbon dioxide which can be implemented cost-effectively.

[0011] The object is achieved by a system for liquefying carbon dioxide comprising a compressor unit with an inflow for a medium containing carbon dioxide, which is at a pressure p inlet and a temperature T inlet, wherein the compressor unit is designed such that the medium containing carbon dioxide is compressed and flows out of the compressor unit at an outlet opening at a pressure p compressor and a temperature T compressor, wherein the compressor unit has at least one liquefaction compressor stage, wherein a liquefaction heat exchanger is arranged downstream of the liquefaction compressor stage and is fluidically coupled to the liquefaction compressor stage, wherein the compressor unit further has at least one cooling compressor stage, which is designed such that the temperature and pressure of a cooling medium flowing through the cooling compressor stage is increased,wherein a cooling heat exchanger is arranged downstream of the cooling compressor stage and is fluidly coupled to the cooling compressor stage, wherein the cooling heat exchanger is designed such that a second cooling medium flows through the cooling heat exchanger and, through thermal contact, the temperature of the cooling medium is lowered and the temperature of the second cooling medium is increased, wherein the condensing heat exchanger is designed such that the cooling medium cooled in the cooling heat exchanger flows through the condensing heat exchanger and, through thermal contact, the temperature of the medium is lowered and the temperature of the cooling medium is increased.

[0012] Advantageous embodiments are the subject of the subclaims.

[0013] The invention therefore proposes to dispense with two separate compressor trains or compressor trains. DESCRIPTION OF THE INVENTION

[0014] The invention is based on the idea of ​​using only one compressor unit. This is preferably achieved by designing the compressor unit as a geared compressor, on which both the condensing compressor stages and the cooling compressor stages are arranged. The geared compressor has a large gear with several pinions coupled to the large gear to transmit torque. A condensing compressor stage or a cooling compressor stage is arranged on one pinion. According to the invention, the system is designed such that a single geared compressor is used, on which all compressor stages, both the condensing compressor stages and the cooling compressor stages, are arranged. This eliminates the need for a second or additional compressor, resulting in enormous cost savings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In the following, an embodiment of the invention is explained in more detail with reference to the following figures.

[0016] The above-described properties, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more clearly understood in connection with the following description of the embodiments, which are explained in more detail in connection with the drawings.

[0017] Identical components or components with the same function are marked with the same reference symbols.

[0018] Embodiments of the invention are described below with reference to the drawings. These are not intended to represent the embodiments to scale; rather, the drawings are presented in a schematic and / or slightly distorted form where necessary for explanation. With regard to additions to the For teachings that are immediately apparent from the drawing, reference is made to the relevant state of the art.

[0019] They show:

[0020] FIG 1 shows a schematic representation of the system according to the invention

[0021] FIG 2 a schematic representation of a gear compressor for use in the system according to the invention DESCRIPTION OF THE EMBODIMENTS

[0022] Figure 1 shows a schematic representation of plant 1 for liquefying carbon dioxide. Plant 1 comprises a compression circuit and a cooling circuit, which are described in more detail below. A medium containing carbon dioxide enters a first liquefaction compressor stage 3 via an inlet 2. In the liquefaction compressor stage 3, the pressure of the medium containing carbon dioxide is increased, and the temperature also increases. After the liquefaction compressor stage 3, the medium flows via a line 4 through a first liquefaction heat exchanger 5, where the temperature of the medium is reduced.

[0023] After the condensation heat exchanger 5, the medium flows through a separator ß. There, the water is separated from the medium and discharged via a line 7.

[0024] The medium then flows via a line 8 into a second condensing compressor stage 9, where the temperature and pressure of the medium are increased. After the condensing compressor stage 9, the medium flows via a line 10 through a second condensing heat exchanger 11, where the temperature of the medium is reduced.

[0025] After the second condensation heat exchanger 11, the medium flows through another separator 12. There, further water is separated from the medium and discharged via a line 13.

[0026] The medium then flows via a line 14 into a third condensing compressor stage 15, where the temperature and pressure of the medium are increased. After the condensing compressor stage 15, the medium flows via a line 16 through a third condensing heat exchanger 17, where the temperature of the medium is reduced.

[0027] The medium flowing downstream of the third condensation heat exchanger 17 contains predominantly pure carbon dioxide in a gas-liquid mixture. In a separator 18, the gas flowing into line 19 is separated from the liquid carbon dioxide flowing into a container 20. The carbon dioxide is now available in a liquid state for transport. In addition to the compression circuit described above, another circuit, which can be referred to as a cooling circuit, is included in system 1. Starting with a cooling medium inlet 21, a cooling medium flows into a cooling compressor stage 22. In the cooling compressor stage 22, the temperature and pressure of the cooling medium are increased. After the cooling compressor stage 22, the cooling medium flows via a line 23 through a first cooling heat exchanger 24. A second cooling medium, such as cold water, also flows through the cooling heat exchanger 24 via a supply line 25. Through thermal contact between the cold water and the warm cooling medium, the cold water is heated to warm water and the cooling medium cools down. The warm water flows out of the cooling compressor stage 24 via a line 26. The cooled cooling medium flows via a line 27 to a second cooling compressor stage 28.

[0029] In the second cooling compressor stage 27, the temperature and pressure of the cooling medium are increased, and it flows out of line 29. In line 29, the cooling medium is present in a mixture of liquid and gaseous form. Therefore, the gaseous cooling medium is discharged via line 31 in a separator 30, while the liquid cooling medium is conducted via line 32 to a distributor 33.

[0030] In the distributor 33, the cooling medium is divided into a first line 34, a second line 35, and a third line 36. A first Joule-Thomson valve 37 is arranged in the first line 34, a second Joule-Thomson valve 38 is arranged in the second line 35, and a third Joule-Thomson valve 39 is arranged in the third line 36.

[0031] The cooling medium is cooled in the first Joule-Thomson valve 37. The cooled cooling medium flows via a line 40 through the first condensing heat exchanger 5. Through thermal contact between the cooling medium and the medium, the medium is cooled and the cooling medium is heated. The heated cooling medium flows via a line 41 into line 21 and then back into the first cooling compressor stage 22.

[0032] The cooling medium is also cooled in the second Joule-Thomson valve 38. The cooled cooling medium flows via a line 42 through the second condensing heat exchanger 11. Thermal contact between the cooling medium and the medium cools the medium and heats the cooling medium. The heated cooling medium flows via a line 43 into line 21 and then back into the first cooling compressor stage 22.

[0033] The cooling medium is also cooled in the third Joule-Thomson valve 39. The cooled cooling medium flows via a line 44 through the third condensing heat exchanger 17. Thermal contact between the cooling medium and the medium cools the medium and heats the cooling medium. The heated cooling medium flows via a line 45 into line 21 and then back into the first cooling compressor stage 22.

[0034] The cooling medium can be, for example, ammonia.

[0035] Figure 2 shows an embodiment of a geared compressor 46 that can be used in the system according to the invention. The geared compressor 46 shown in Figure 2 is intended to illustrate only schematically that in the system 1 according to the invention only one geared compressor 46 can be used, which leads to significant cost savings. A large gear 48 is driven via a drive line 47. On the large gear 48, a first pinion 49, a second A pinion 50 and a third pinion 51 are arranged to transmit torque. Rotation of the large gear 48 also generates rotation of the first pinion 49, the second pinion 50, and the third pinion 51. The cooling compressor stages 22, 28 and the condensing compressor stages 3, 9, 12 are now arranged on the pinions 49, 50, and 51.

[0036] For example, the first cooling compressor stage 22 and the first condensing compressor stage 3 can be arranged on the first pinion 49. The second condensing compressor stage 9 and the second cooling compressor stage 28 can be arranged, for example, on the second pinion 50. Furthermore, the third condensing compressor stage 15 can be arranged, for example, on the third pinion 51. As described above, Figure 2 is intended to symbolize the distribution of the compressor stages 3, 9, 12, 22, 28 only schematically and by way of example. A different arrangement of compressor stages 3, 9, 12, 22, 28 per pinion 49, 50, 51, or even the use of additional pinions, is possible.

Claims

Claims 1. Plant (1) for liquefying carbon dioxide, comprising a compressor unit with an inflow (2) for a medium containing carbon dioxide, which medium is at a pressure p inlet and a temperature T inlet, wherein the compressor unit is designed such that the medium containing carbon dioxide is compressed and flows out of the compressor unit at an outlet opening at a pressure p compressor and a temperature T compressor, wherein the compressor unit has at least one liquefaction compressor stage (3, 9, 15), wherein a liquefaction heat exchanger (5, 11, 17) is arranged downstream of the liquefaction compressor stage (3, 9, 15), which is fluidically coupled to the liquefaction compressor stage (3, 9, 15), wherein the compressor unit further has at least one cooling compressor stage (22, 28), which is designed such that the temperature and the pressure one through the cooling compressor stage (22,28) flowing cooling medium is increased, wherein a cooling heat exchanger (24) is arranged downstream of the cooling compressor stage (22, 28), which is fluidically coupled to the cooling compressor stage (22, 28), wherein the cooling heat exchanger (24) is designed such that a second cooling medium flows through the cooling heat exchanger (24) and, through thermal contact, the temperature of the cooling medium is lowered and the temperature of the second cooling medium is increased, wherein the condensation heat exchanger (5, 11, 17) is designed such that the cooling medium cooled in the cooling heat exchanger (24) flows through the condensation heat exchanger (5, 11, 17) and, through thermal contact, the temperature of the medium is lowered and the temperature of the cooling medium is increased.

2. System (1) according to claim 1, wherein the compressor unit is designed as a gear compressor (46).

3. System (1) according to claim 2, wherein the condensing compressor stage (3, 9, 15) and the cooling compressor stage (22, 28) are arranged on the one gear compressor (46).

4. System (1) according to claim 1 or 2, wherein the cooling medium is ammonia.

5. Plant (1) according to one of the preceding claims, wherein the second cooling medium is water.

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