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

TITLE Facility and method for liquefying carbon dioxide TECHNICAL FIELD

[0001] The invention relates to a facility for liquefying carbon dioxide, comprising a compressor unit having an inflow for a carbon dioxide-containing medium which is at a pressure pinlet and a temperature Tinlet, wherein the compressor unit is configured such that the carbon dioxide-containing medium is compressed and flows out of the compressor unit at an outflow opening at a pressure pcompressor and a temperature Tcompressor. BACKGROUND

[0002] It is known that the emission of carbon dioxide (CO2) constitutes a considerable problem for global climate development. Efforts are therefore being made to avoid the production of carbon dioxide or at least to capture the carbon dioxide during production and to store it safely for the future. For this purpose, the captured carbon dioxide would have to be transported.

[0003] The transport of captured carbon dioxide for storage or further use presents a challenge, especially over long distances. One possibility for transporting carbon dioxide would be to provide pipelines, although suitable pipelines are currently available only to a limited extent.

[0004] So-called amine plants are suitable for capturing carbon dioxide from flue gases and are currently regarded as a commercially successful large-scale technology. Amine systems require considerable amounts of low-pressure steam or heat to carry out the process. The carbon dioxide captured in an amine system is supplied at low pressure.

[0005] After the capture of the carbon dioxide, the carbon dioxide is generally transported to a storage reservoir or another use application. 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 require considerable time and could take up to ten years. A quick way of transporting carbon dioxide would therefore be to transport liquefied carbon dioxide.

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

[0007] Thus, a modern application consists of using a separate cryogenic refrigerant liquefaction circuit, in order to liquefy the carbon dioxide after it has been compressed to a required pressure. For this purpose, two separate compression trains are required, one being used for carbon dioxide compression and the other for the cryogenic refrigerant circuit. A frequently used refrigerant is ammonia, which, however, requires careful consideration due to its toxicity.

[0008] In the case of liquefaction of carbon dioxide, there is a loss of compression energy between the compressor stages, which has an effect on the overall efficiency of a plant.

[0009] It is desirable to provide a facility for liquefying carbon dioxide which has low investment costs and low process complexity. SUMMARY OF THE INVENTION

[0010] It is therefore an object of the present invention to provide a facility for liquefying carbon dioxide which can be constructed cost-effectively.

[0011] The object is achieved by a facility for liquefying carbon dioxide, comprising a compressor unit having an inflow for a carbon dioxide-containing medium which is at a pressure pinlet and a temperature Tinlet, wherein the compressor unit is configured such that the carbon dioxide-containing medium is compressed and flows out of the compressor unit at an outflow opening at a pressure pcompressor and a temperature Tcompressor, 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 furthermore has at least one cooling compressor stage which is configured such that the temperature and the pressure of a cooling medium flowing through the cooling compressor stage are increased, wherein a cooling heat exchanger is arranged downstream of the cooling compressor stage and is fluidically coupled to the cooling compressor stage, wherein the cooling heat exchanger is configured such that a second cooling medium flows through the cooling heat exchanger and the temperature of the cooling medium is lowered and the temperature of the second cooling medium is increased by thermal contact, wherein the liquefaction heat exchanger is configured such that the cooling medium cooled in the cooling heat exchanger flows through the liquefaction heat exchanger and the temperature of the medium is lowered and the temperature of the cooling medium is increased by thermal contact.

[0012] Advantageous embodiments are the subject matter of the dependent claims.

[0013] The invention thus proposes dispensing with two separate compressor trains. DESCRIPTION OF THE INVENTION

[0014] The invention is based on the concept of using only one compressor unit. This is preferably achieved in that the compressor unit is configured as a geared compressor, on which both the liquefaction compressor stages and the cooling compressor stages are arranged. The geared compressor has a large wheel with a plurality of pinions which are coupled to the large wheel in a torquetransmitting manner. A liquefaction compressor stage or a cooling compressor stage is arranged on a pinion. According to the invention, the facility is configured such that a single geared compressor is used, on which all compressor stages, both the liquefaction compressor stages and the cooling compressor stages, are arranged. The use of a second or further compressor is thus omitted, which leads to enormous cost savings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] An exemplary embodiment of the invention will be explained in greater detail below with reference to the figures that follow.

[0016] The above-described properties,   features and advantages of this invention and the way in which they are achieved will become clearer and more distinctly understood in connection with the following description of the exemplary embodiments, which will be explained in greater detail in connection with the drawings.

[0017] In this context, identical components or components with the same function are identified by the same reference signs.

[0018] Exemplary embodiments of the invention will be described below with reference to the drawings. These drawings are not intended to illustrate the exemplary embodiments to scale; instead, the drawings are presented in a schematic and / or slightly distorted form where this aids understanding. With regard to additions to the teachings which are directly apparent in the drawings, reference is made to the relevant prior art.

[0019] In the drawings:

[0020] FIG 1 shows a schematic illustration of the facility according to the invention

[0021] FIG 2 shows a schematic illustration of a geared compressor for use in the facility according to the invention DESCRIPTION OF THE EMBODIMENTS

[0022] Figure 1 shows a schematic illustration of the facility 1 for liquefying carbon dioxide. The facility 1 comprises a compression circuit and a cooling circuit, which are described in more detail below. A carbon dioxide-containing medium passes via an inflow 2 into a first liquefaction compressor stage 3. In the liquefaction compressor stage 3, the pressure of the carbon dioxide-containing medium is increased, wherein the temperature likewise 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 liquefaction heat exchanger 5, the medium flows through a separator 6. There, the water is separated from the medium and discharged via a line 7.

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

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

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

[0027] The medium flowing downstream of the third liquefaction heat exchanger 17 contains predominantly pure carbon dioxide in a mixture of gas and liquid. A separator 18 separates the gas, which flows into the line 19, from the liquid carbon dioxide, which flows into a container 20. The carbon dioxide is now present in the liquid state for transport.

[0028] In addition to the above-described compression circuit, a further circuit, which can be called a cooling circuit, is also contained in the facility 1. Starting with a cooling medium inflow 21, a cooling medium flows into a cooling compressor stage 22. In the cooling compressor stage 22, the temperature and the 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, likewise flows via a supply line 25 through the cooling heat exchanger 24 and, by means of thermal contact between the cold water and the warm cooling medium, the cold water heats up into 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 the pressure of the cooling medium are increased and it flows out of the line 29. The cooling medium is present in the line 29 in a mixture of liquid and gaseous forms. Therefore, in a separator 30, the gaseous cooling medium is discharged via a line 31, wherein the liquid cooling medium is conducted via a line 32 to a divider 33.

[0030] In the divider 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 liquefaction heat exchanger 5. The medium is cooled and the cooling medium is heated by thermal contact between the cooling medium and the medium. The heated cooling medium flows via a line 41 into the line 21 and then again into the first cooling compressor stage 22.

[0032] The cooling medium is likewise cooled in the second Joule-Thomson valve 38. The cooled cooling medium flows via a line 42 through the second liquefaction heat exchanger 11. The medium is cooled and the cooling medium is heated by thermal contact between the cooling medium and the medium. The heated cooling medium flows via a line 43 into the line 21 and then again into the first cooling compressor stage 22.

[0033] The cooling medium is likewise cooled in the third Joule-Thomson valve 39. The cooled cooling medium flows via a line 44 through the third liquefaction heat exchanger 17. The medium is cooled and the cooling medium is heated by thermal contact between the cooling medium and the medium. The heated cooling medium flows via a line 45 into the line 21 and then again into the first cooling compressor stage 22.

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

[0035] Figure 2 shows an embodiment of a geared compressor 46 which can be used in the facility according to the invention. The geared compressor 46 shown in figure 2 is intended to illustrate purely schematically that, in the facility 1 according to the invention, in total only one geared compressor 46 may be used, which leads to a great cost saving. A large wheel 48 is driven via a drive line 47. A first pinion 49, a second pinion 50 and a third pinion 51 are arranged on the large gear 48 in a torque-transmitting manner. A rotation of the large gear 48 also causes a rotation of the first pinion 49, the second pinion 50 and the third pinion 51. The cooling compressor stages 22, 28 and the liquefaction compressor stages 3, 9, 12 are now arranged on the pinions 49, 50, 51.

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

Claims

1. A facility (1) for liquefying carbon dioxide, comprising a compressor unit having an inflow (2) for a carbon dioxide-containing medium which is at a pressure pinlet and a temperature Tinlet, wherein the compressor unit is configured such that the carbon dioxide-containing medium is compressed and flows out of the compressor unit at an outflow opening at a pressure pcompressor and a temperature Tcompressor, wherein the compressor unit has at least one liquefaction compressor stage (3,  9,  15), wherein aliquefaction heat exchanger (5,  11,  17) is arrangeddownstream of the liquefaction compressor stage (3, 9, 15)and is fluidically coupled to the liquefaction compressor stage (3, 9, 15), wherein the compressor unit furthermorehas at least one cooling compressor stage (22, 28) which isconfigured such that the temperature and the pressure of a cooling medium flowing through the cooling compressor stage(22, 28) are increased, wherein a cooling heat exchanger(24) is arranged downstream of the cooling compressor stage(22,  28) and is fluidically coupled to the coolingcompressor stage (22,  28), wherein the cooling heatexchanger (24) is configured such that a second cooling medium flows through the cooling heat exchanger (24) and the temperature of the cooling medium is lowered and the temperature of the second cooling medium is increased by thermal contact, wherein the liquefaction heat exchanger (5, 11, 17) is configured such that the cooling medium cooledin the cooling heat exchanger (24) flows through the liquefaction heat exchanger (5, 11, 17) and the temperatureof the medium is lowered and the temperature of the coolingmedium is increased by thermal contact.

2. The facility (1) as claimed in claim 1, wherein the compressor unit is configured as a geared compressor (46).

3. The facility (1) as claimed in claim 2, wherein the liquefaction compressor stage (3, 9, 15) and thecooling compressor stage (22, 28) are arranged on the onegeared compressor (46).

4. The facility (1) as claimed in claim 1 or 2,wherein the cooling medium is ammonia.

5. The facility (1) as claimed in any of the preceding claims,wherein the second cooling medium is water.

Images