Facility and method for liquefying carbon dioxide

Abstract

The invention relates to a method for producing liquid carbon dioxide in a facility (1), wherein the pressure and temperature of a medium containing carbon dioxide are first increased in a compressor unit (2); the medium containing carbon dioxide is separated into a first mass flow (34) and into a second mass flow (35) in a first separating device (32), said first mass flow (34) flowing through a first conversion device (36) and said second mass flow (35) flowing through a second conversion device (37); the temperature and the pressure of the medium are reduced downstream of the first and second conversion device (36, 37), the temperature of the medium downstream of the first conversion device (36) being lower than the temperature of the medium downstream of the second conversion device (37); and the medium downstream of the first conversion device (36) is conducted to a liquid heat exchanger (41) where the thermal energy of the medium from the first conversion device (36) is exchanged with the thermal energy of the medium from the second conversion device (37), as a result of which the carbon dioxide from the second conversion device (37) is liquefied downstream of the liquid heat exchanger (41).

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 opening 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 under 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, which 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, there are comparatively few suitable pipelines available, and the construction of new pipelines would be a significant time-consuming process, potentially taking up to ten years. A rapid way to transport carbon dioxide would therefore be to transport liquefied carbon dioxide. The 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.

[0009] 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 plant for liquefying carbon dioxide, comprising a compressor unit with an inflow opening 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 under a pressure p compressor and a temperature T compressor, further comprising a first separation device, which is fluidically connected to the inlet side of the compressor unit and divides the medium containing carbon dioxide coming from the compressor unit into a first mass flow MMSO1 and a second mass flow MMSO2, further comprising a first conversion device, which is designed such that the temperature Tumw_oi,in and the pressure p Umw_i,in of the first mass flow MMSOI to a lower temperature Tumw_oi,out and a lower pressure Pumw_1,out, further comprising a second conversion device which is designed such that the temperature Tumw_o2,in and the pressure p U mw_2,in of the second mass flow MMso2 to a lower temperature Tumw_o2,out and a lower pressure Pumw_2,out, where Tumwoi ,out < Tumw02,out, further comprising a liquid heat exchanger which is designed such that the thermal energies of the medium coming from the first conversion device are exchanged with the medium coming from the second conversion device such that the medium coming from the second conversion device is liquid after passing through the liquid heat exchanger.

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

[0013] The invention proposes to dispense with a separate refrigeration circuit, which requires a separate compressor. When liquefying the carbon dioxide, a portion of the carbon dioxide itself is used as a refrigerant. This requires only a single compressor unit. Furthermore, the invention eliminates the need for a dedicated refrigerant circuit. Furthermore, the heat released during the compression process is utilized to generate water vapor. DESCRIPTION OF THE INVENTION

[0014] The invention is based on the idea of ​​generating a current from Using carbon dioxide to liquefy previously captured carbon dioxide. This process drives down investment costs. No additional refrigeration compressor or refrigerant circuit is required.

[0015] Furthermore, the invention is based on the idea of ​​using the compression heat generated in the compressor unit to generate low-pressure steam. This reduces the water vapor to the required level.

[0016] The temperature at which carbon dioxide exists in a liquid state depends on the pressure to which it is subjected. Carbon dioxide is comparatively unique because it can exist as a gas, liquid, or solid at various combinations of temperature and pressure. At atmospheric pressure, the temperature at which carbon dioxide becomes a liquid is -78.5°C. However, when pressure is applied, the carbon dioxide can exist as a liquid at higher temperatures. According to the invention, liquefaction of carbon dioxide is achieved here at approximately 15 bar and -30°C, which is well suited for commercial tank or ship transport. Other pressure and temperature levels can be achieved according to the invention.

[0017] The plant and method according to the invention are explained in detail below. A medium containing carbon dioxide is compressed at high temperature, and in a recooling unit, the heat is recovered by supplying saturated water at low pressure, which is evaporated from the heat of compression and converted into low-pressure steam. The gaseous carbon dioxide is fed into a separator to remove the condensed water before it is fed to the next stage of the compressor. After each compression stage, the heat is recovered and steam is generated. After a few compression stages, a process pressure for the carbon dioxide is reached. The carbon dioxide is then split into two streams, and both streams are expanded to two different pressure levels by two conversion devices, preferably designed as Joule-Thomson valves.The low-pressure streams are used as refrigerants, and the high-pressure streams are then liquefied by exchanging cold energy with cold energy from the lower cryogenic-temperature stream. At the same time, the carbon dioxide refrigerant stream absorbs heat from the compressed carbon dioxide stream and evaporates. The mass flow of carbon dioxide is divided so that the refrigerant stream can generate enough cooling to liquefy the other carbon dioxide stream. The evaporated refrigerant is then returned to the inlet of the compressor stages based on the respective inlet pressure.

[0018] In a first advantageous development, the system further comprises a second separation device with a first outlet line and a second outlet line, wherein the second separation device is designed such that the gaseous medium coming from the first conversion device flows into the first outlet line and the liquid medium coming from the first conversion device flows into the second outlet line, wherein the second outlet line is coupled to the liquid heat exchanger such that the thermal energies of the medium coming from the second outlet line be exchanged with the medium coming from the second conversion device.

[0019] This ensures that the carbon dioxide emerging from the first conversion device, which comprises a mixture of gaseous and liquid carbon dioxide, is separated in the second separation device. The liquid carbon dioxide reaches the liquid heat exchanger, where it becomes gaseous again through the exchange of thermal energy as it interacts with the warmer gaseous carbon dioxide from the second conversion device. This interaction ultimately transforms the gaseous carbon dioxide from the second conversion device into liquid carbon dioxide, which has physical parameters suitable for transport.

[0020] In a further advantageous development, the first conversion device and / or the second conversion device are designed as a Joule-Thomson valve.

[0021] In a Joule-Thomson valve, the temperature of the carbon dioxide is reduced upon expansion, provided the pressure is below the inversion temperature of carbon dioxide. A Joule-Thomson valve is a comparatively inexpensive way to appropriately reduce the temperature of carbon dioxide.

[0022] In an alternative embodiment, the first conversion device and / or the second conversion device are designed as an expansion turbine.

[0023] As an alternative to a Joule-Thomson valve, the temperature and pressure can also be reduced using a suitable expansion turbine. The resulting rotational energy can be further utilized.

[0024] In a further advantageous development, the compressor unit has various compression stages. It should be noted that the compressor unit represents a compressor or compressor with a single drive. The compressor or compressor has multiple compression stages. In the case of a geared compressor as an embodiment of the compressor or compressor, a large gear is driven by a drive unit. Several pinions are arranged on the large gear, with each pinion having an impeller for a compression stage.

[0025] One advantage of the invention is that only one compressor is required for the system. This can be a geared compressor, for example. This leads to significant cost savings.

[0026] In a further advantageous development, the compressor unit has a first compressor stage with the inflow opening, wherein the first compressor stage has a first compressor stage outlet, wherein the compressor unit further has a second compressor stage with a second flow inlet, wherein the first compressor stage outlet is fluidically connected to the second flow inlet, wherein a first heat exchanger is arranged between the first compressor stage outlet and the second flow inlet, which first heat exchanger is designed such that the thermal energy of the medium flowing in the compressor unit is exchanged with an exchange medium flowing through the first heat exchanger.

[0027] This allows the carbon dioxide-containing medium to be cooled after each compressor stage before entering the next compressor stage. The thermal energy converted in the first heat exchanger can be used to heat the exchange medium. Ideally, if water is used as the exchange medium, it is evaporated, and the resulting water vapor can be used for further processing.

[0028] In a further advantageous development, a third compressor stage is arranged after the second compressor stage, wherein the third Compressor stage is fluidically connected to the second compressor stage, wherein a second heat exchanger is arranged between the second compressor stage and the third compressor stage, wherein the second heat exchanger is designed such that the temperature of the exchange medium is increased.

[0029] In an advantageous further development, a third heat exchanger is arranged between the compressor unit and the first separation device, wherein the third heat exchanger is designed such that the temperature of the exchange medium increases.

[0030] In a further advantageous development, the system has a cooling supply line which is designed such that the gaseous medium present after the second separation unit and after the liquid heat exchanger is supplied to the compressor unit.

[0031] Thus, the carbon dioxide required in the liquid heat exchanger for the liquefaction of carbon dioxide is fed to a suitable point in the compressor unit in order to further reduce the temperature of the medium containing carbon dioxide.

[0032] Advantageously, the cooling supply line supplies the gaseous medium present after the second separation unit and after the liquid heat exchanger to the second compressor stage.

[0033] The object is also achieved by a method for liquefying carbon dioxide, wherein in a compressor unit, a medium containing carbon dioxide is first increased to a pressure and a temperature, wherein in a first separation device, the medium containing carbon dioxide is divided into a first mass flow and a second mass flow, wherein the first mass flow flows through a first conversion device and the second mass flow through a second conversion device, wherein the temperature and the pressure of the medium are reduced after the first and second conversion device, wherein the temperature of the medium after the first conversion device is lower than the temperature of the medium after the second conversion device, wherein the medium after the first conversion device is led to a liquid heat exchanger, where the thermal energy of the medium from the first conversion device is exchanged with the thermal energy of the medium from the second conversion device, whereby a liquefaction of the carbon dioxide from the second conversion device after the liquid heat exchanger takes place. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In the following, an embodiment of the invention is explained in more detail with reference to the following figures.

[0035] 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.

[0036] Identical components or components with the same function are marked with the same reference symbols.

[0037] Embodiments of the invention are described below with reference to the drawings. These are not intended to represent the embodiments to scale; rather, where useful for explanation, the drawings are presented in a schematic and / or slightly distorted form. For supplements to the teachings immediately apparent in the drawings, reference is made to the relevant prior art.

[0038] They show:

[0039] FIG 1 shows a schematic representation of the system according to the invention DESCRIPTION OF THE EMBODIMENTS

[0040] Figure 1 shows a schematic representation of the plant 1 for liquefying carbon dioxide. The plant 1 comprises a compressor unit 2. The compressor unit 2 here comprises a geared compressor having a plurality of compressor stages 3, 4, 5. One compressor stage 3, 4, 5 is arranged as a radial turbine on a large wheel of the geared compressor. The geared compressor is driven solely by a drive unit (not shown). The compressor stages 3, 4, 5 have impellers. The structure of a geared compressor is well known. Therefore, a detailed description of a geared compressor is omitted here. The number of compressor stages can vary. The plant according to the invention can therefore also be designed with fewer than three or with more than three compressor stages.

[0041] A medium 7 containing carbon dioxide enters the compressor unit 2, more precisely into the first compressor stage 3, via an inlet opening 6. In this embodiment, the medium 7 is made up of gaseous Carbon dioxide contaminated with water is assumed. It should be noted that the system 1 according to the invention can also be operated with gaseous carbon dioxide without impurities. Medium 7 is usually at atmospheric pressure.

[0042] In the first compressor stage 3, the temperature and pressure of the medium 7 are increased, and the medium is conveyed via a line 8 to a first heat exchanger 9. An exchange medium such as water is supplied to the first heat exchanger 9 via an inlet line 10. Through the exchange of thermal energy between the medium emerging from the first compressor stage 3 and the water, the temperature of the water is increased and the temperature of the medium is decreased, so that water vapor flows out via an outlet line 11.

[0043] The medium cooled in the first heat exchanger 9 is fed via a line 12 to a separator 13, where part of the water is separated from the medium and discharged via a line 14.

[0044] The medium flows through another line 15 to a second compressor stage 4, where the temperature and pressure of the medium are increased. After the second compressor stage 4, the medium flows through an outlet line 16 to a second heat exchanger 17. Water is also supplied to the second heat exchanger 17 via a line 18. The exchange between the medium coming from the second compressor stage 4 and the water increases the temperature of the water and decreases the temperature of the medium, so that water vapor flows out through an outlet line 19.

[0045] After the second heat exchanger 17, the medium passes via a line 20 to a further separator 21, where again some of the water is separated from the medium and discharged via a line 22. After the separator 21, the cooled medium passes to a third compressor stage 5, where the temperature and pressure are increased. After the third compressor stage 5, the medium passes via an outlet-side line 24 to a third heat exchanger 25. Water is also supplied to the third heat exchanger 25 via a line 26. Through the exchange of the medium coming from the third compressor stage 5 and the water, the temperature of the water is increased and the temperature of the medium is reduced, so that water vapor flows out via an outlet-side line 27.

[0046] The outflowing steam is discharged via a collecting line 28 and reused (not shown). The incoming water is fed to the respective heat exchangers 9, 17, and 25 via a collecting line 29.

[0047] It should be noted again that the first compressor stage 3, the second compressor stage 4 and the third compressor stage 5 are part of a single geared compressor, which leads to a significant cost saving. The compressor unit 2 is thus designed such that the medium 7 containing carbon dioxide is compressed and flows out of the compressor unit 2 at an outlet opening 31 under a pressure pcompressor and a temperature Tcompressor. The medium enters a separator 30, which also Dryer. In separator 30, water is again separated from the medium. After the separator, the medium ideally comprises pure gaseous carbon dioxide.

[0049] In a first separation device 32, which is also referred to as a divider, the inlet 33 of the first separation device 32 is fluidically connected to the compressor unit 2. The medium containing carbon dioxide coming from the compressor unit 2 is divided in the first separation device 32 into a first mass flow (MMSOI ) 34 and a second mass flow (MMSO2) 35. The first mass flow (MMSOI ) 34 flows through a first conversion device 36. In this first conversion device 36, the temperature Tumw_oi, in and the pressure p U mw_oi,in of the first mass flow (MMSOI ) 34 to a lower temperature T Umw_oi, out and a lower pressure Pumw_01, out. For this purpose, the first conversion device 36 is designed as a Joule-Thomson valve. The operation of a Joule-Thomson valve is known. A detailed description of a Joule-Thomson valve is therefore omitted here. Other embodiments of the first conversion device are possible. For example, in an alternative embodiment, the first conversion device 36 can be designed as an expansion turbine. The second mass flow (MMSO2) 35 flows through a second conversion device 37. In this second conversion device 37, the temperature Tumw_o2, in and the pressure p U mw_02,in of the second mass flow (MMSO2) 35 to a lower temperature T Umw_02,out and a lower pressure Pumw_02,out. For this purpose, the second conversion device 37 is designed as a Joule-Thomson valve. The operation of a Joule-Thomson valve is known. A detailed description of a Joule-Thomson valve is therefore omitted here. Other embodiments of the second conversion device are possible. For example, in an alternative embodiment, the second conversion device 37 can be designed as an expansion turbine.

[0051] The first conversion device 36 and the second conversion device 37 are designed such that the following applies: Tumwoi.out < T U mw02,out. This means that the medium coming from the first conversion device 36 is cooler than the medium coming from the second conversion device 37.

[0052] The medium coming from the first conversion device 36 is fed to a second separation device 38. In this second separation device 38, the medium coming from the first conversion device 36 is divided into a line with a gaseous portion 39 and a line with a liquid portion 40.

[0053] The system 1 further comprises a liquid heat exchanger 41. The medium from the line with the liquid portion 40 flows through the liquid heat exchanger 41. The cooler medium coming from the second conversion device 37 also flows through the liquid heat exchanger 41, wherein the medium coming from the second conversion device 37 is further cooled in the liquid heat exchanger 41 such that the medium becomes liquid at an outlet 42 of the liquid heat exchanger 41. The medium, which after the various dewatering devices (separator 30, separator 21, separator 13) is now pure carbon dioxide, is now in liquefied form and can be transported in a transport container 43. The liquefied Carbon dioxide exists at a temperature of approximately -30°C and a pressure of approximately 14 bar. Other temperatures and pressures can be achieved with the system according to the invention.

[0054] The gaseous portion 39 of the medium in the line is collected in a collecting device 44 and fed to a suitable location via a cooling supply line 45 of the system 1. The medium in the cooling supply line 45 has physical parameters such as pressure and temperature that are suitable for use in the compressor unit 2 for cooling purposes. Thus, a suitable location would be to connect the cooling supply line 45 to the further line 15. so that the medium can flow in before the second compressor stage 4. Another arrangement would be possible.

[0055] The gaseous medium heated from the liquid heat exchanger 41 is also led to the collecting device 44 via a line 46.

Claims

Claims 1. Plant (1) for liquefying carbon dioxide, comprising a compressor unit (2) with an inflow opening (6) for a medium containing carbon dioxide, which is at a pressure p inlet and a temperature T inlet, wherein the compressor unit (2) is designed such that the medium containing carbon dioxide is compressed and flows out of the compressor unit (2) at an outflow opening (31) at a pressure p compressor and a temperature T compressor, further comprising a first separation device (32) which is fluidically connected to the inlet side of the compressor unit (2) and divides the medium containing carbon dioxide coming from the compressor unit (2) into a first mass flow MMSO1 (34) and a second mass flow MMSO2 (35), further comprising a first conversion device (36) which is designed such that the temperature Tumw_oi, in and the pressure p Umw_i,in of the first mass flow MMSOI (34) to a lower temperature T U mw_oi, out and a lower pressure Pumw_1 ,out, further comprising a second conversion device (37) which is designed such that the temperature Tumw_o2,in and the pressure p U mw_2,in of the second mass flow MMSO2 (35) to a lower temperature T U mw_02,out and a lower pressure Pumw_2,out, where Tumwoi ,out < Tumw02,out, further comprising a liquid heat exchanger (41) which is designed such that the thermal energies of the medium coming from the first conversion device (36) are exchanged with the medium coming from the second conversion device (37) such that the medium coming from the second conversion device (37) is liquid after passing through the liquid heat exchanger (41).

2. Plant (1) according to claim 1, wherein the plant (1) further comprises a second separation device (38) with a first outlet line (39) and a second outlet line (40), wherein the second separation device (38) is designed such that the gaseous medium coming from the first conversion device (36) flows into the first outlet line (39) and the liquid medium coming from the first conversion device (36) flows into the second outlet line (40), wherein the second outlet line (40) is coupled to the liquid heat exchanger (41) such that the thermal energies of the medium coming from the second outlet line (40) are exchanged with the medium coming from the second conversion device (37).

3. System (1) according to claim 1 or 2, wherein the first conversion device (36) and / or the second conversion device (37) are designed as a Joule-Thomson valve.

4. Plant (1) according to claim 1 or 2, wherein the first conversion device (36) and / or the second conversion device (37) are designed as an expansion turbine.

5. System (1) according to one of the preceding claims, wherein the compressor unit (2) has different compressor stages (3, 4, 5).

6. System (1) according to claim 5, wherein the compressor unit (2) has a first compressor stage (3) with the inflow opening (6), wherein the first compressor stage (3) has a first compressor stage outlet, wherein the compressor unit (2) further has a second compressor stage (4) with a second flow inlet, wherein the first compressor stage outlet is fluidically connected to the second flow inlet, wherein a first heat exchanger (9) is arranged between the first compressor stage outlet and the second flow inlet, which first heat exchanger is designed such that the thermal energy of the medium flowing in the compressor unit (2) is exchanged with an exchange medium flowing through the first heat exchanger (9).

7. Plant (1) according to claim 6, wherein the first heat exchanger (9) is designed such that the temperature of the exchange medium is increased.

8. Plant (1) according to claim 6 or 7, wherein a third compressor stage (5) is arranged after the second compressor stage (4), wherein the third compressor stage (5) is fluidically connected to the second compressor stage (4), wherein a second heat exchanger (17) is arranged between the second compressor stage (4) and the third compressor stage (5), wherein the second heat exchanger (17) is designed such that the temperature of the exchange medium is increased.

9. Plant (1) according to one of the preceding claims, wherein a third heat exchanger (25) is arranged between the compressor unit (2) and the first separation device (32), wherein the third heat exchanger (25) is designed such that the temperature of the exchange medium is increased.

10. System (1) according to one of claims 6 to 9, comprising a cooling supply line (45) designed such that the gaseous medium present after the second separation unit (32) and after the liquid heat exchanger (41) is supplied to the compressor unit (2).

11. System (1) according to claim 10, wherein the cooling supply line (45) supplies the gaseous medium present after the second separation unit (32) and after the liquid heat exchanger (41) to the second compressor stage (4).

12. Plant (1) according to one of claims 6 to 11, wherein the exchange medium is water.

13. System (1) according to one of claims 1 to 12, wherein the compressor unit (2) is designed as a gear compressor.

14. A method for producing liquid carbon dioxide, wherein in a compressor unit (2) a medium containing carbon dioxide is first increased to a pressure and a temperature, wherein in a first separation device (32) the medium containing carbon dioxide is divided into a first mass flow (34) and a second mass flow (35), wherein the first mass flow (34) flows through a first conversion device (36) and the second mass flow (35) through a second conversion device (37), wherein the temperature and the pressure of the medium are reduced after the first (36) and second conversion device (37), wherein the temperature of the medium after the first conversion device (36) is lower than the temperature of the medium after the second conversion device (37), wherein the medium after the first conversion device (36) is led to a liquid heat exchanger (41),where the thermal energy of the medium from the first conversion device (36) is exchanged with the thermal energy of the medium from the second conversion device (37), whereby a liquefaction of the carbon dioxide from the second conversion device (37) takes place after the liquid heat exchanger (41).

15. A method for producing liquid carbon dioxide according to claim 14, wherein the first conversion device (36) and / or the second conversion device (37) are designed as Joule-Thomson valves.

16. A method for producing liquid carbon dioxide according to claim 14, wherein the first conversion device (36) and / or the second conversion device (37) are designed as an expansion turbine.

17. A method for producing liquid carbon dioxide according to any one of claims 14 to 16, wherein the compressor unit (2) has a first compressor stage (3) through which the medium containing carbon dioxide flows, wherein a first heat exchanger (9) is arranged after the compressor stage (3), in which the thermal energy of the medium is exchanged with the thermal energy of an exchange medium.

18. A process for producing liquid carbon dioxide according to claim 17, wherein the exchange medium is water.

19. A method for producing liquid carbon dioxide according to any one of claims 14 to 18, wherein the compressor unit (2) has a second compressor stage (4) arranged downstream of the first compressor stage (3), wherein the temperature and the pressure in the second compressor stage (4) are further increased, wherein a second heat exchanger (17) is arranged downstream of the second compressor stage (4), where the thermal energy of the medium is exchanged with the thermal energy of the exchange medium.

20. A method for producing liquid carbon dioxide according to any one of claims 14 to 19, wherein the compressor unit (2) has a third compressor stage (5) arranged downstream of the second compressor stage (4), wherein the temperature and the pressure in the third compressor stage (5) are further increased, wherein a third heat exchanger (25) is arranged downstream of the third compressor stage (5), where the thermal energy of the medium is exchanged with the thermal energy of the exchange medium.

21. A method for producing liquid carbon dioxide according to any one of claims 14 to 20, wherein the compressor unit (2) is designed as a gear compressor.

22. A method for producing liquid carbon dioxide according to one of claims 14 to 20, wherein the cooled carbon dioxide present in gaseous form after the first conversion device (36) and the carbon dioxide present in gaseous form after the liquid heat exchanger (41) are fed to the compressor unit (2).

23. A method for producing liquid carbon dioxide according to claim 22, wherein the cooled carbon dioxide present in gaseous form after the first conversion device (36) and the carbon dioxide present in gaseous form after the liquid heat exchanger (41) are fed to the second compressor stage (4) of the compressor unit (2).

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