Carbon dioxide liquefaction system

Abstract

To provide a carbon dioxide liquefaction system capable of liquefying carbon dioxide included in carbon dioxide-containing gas with low energy.SOLUTION: A carbon dioxide liquefaction system 1 includes: a water ejector 40 that uses water as drive fluid and carbon dioxide-containing gas as suction fluid; a water drum 10 provided in the wake flow of the water ejector 40 to temporarily store water and carbon dioxide-containing gas; a water drum outlet gas line 81 for discharging the carbon dioxide-containing gas in a gas layer of the water drum 10; a dehumidifier 50 provided in the water drum outlet gas line 81 to dehumidify the carbon dioxide-containing gas; a carbon dioxide separation film 60 for concentrating carbon dioxide included in the carbon dioxide-containing gas dehumidified by the dehumidifier 50; and a carbon dioxide condenser 110 and a liquefaction carbon dioxide drum 120 for liquefying carbon dioxide by cooling the carbon dioxide-containing gas in which carbon dioxide is concentrated by the carbon dioxide separation film 60.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a carbon dioxide liquefaction system for liquefying carbon dioxide. [Background technology]

[0002] There is a need for technology to liquefy gaseous carbon dioxide for the purpose of storage and transportation for CCS (Carbon dioxide Capture and Storage) and CCU (Carbon dioxide capture and utilization). Carbon dioxide can be liquefied at lower pressures at lower temperatures, so if it can be liquefied at low temperatures, the compression power required can be reduced, but a minimum pressure of 0.42 MPaG is required.

[0003] In this regard, Patent Document 1 discloses a technology for liquefying carbon dioxide by utilizing part of the cold energy of an air cryogenic separation unit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5932127 Summary of the Invention [Problem to be solved by the invention]

[0005] However, since Patent Document 1 does not mention the pressure, it is thought that the pressure is increased to a minimum of 0.42 MPaG, which cannot be achieved unless an air cryogenic separation unit is installed, making commercialization difficult.

[0006] Furthermore, since it is assumed that a single component gas of carbon dioxide is obtained, it is necessary to separate carbon dioxide from a carbon dioxide-containing gas in which carbon dioxide is contained in other gases, such as exhaust gas. However, if a large amount of energy is consumed in the process of separating carbon dioxide from a carbon dioxide-containing gas, this will not be energy-efficient and will contradict carbon dioxide capture, so there is a demand for a low-energy process that also includes the separation of carbon dioxide from a carbon dioxide-containing gas.

[0007] The present invention has been made to solve the above problems, and has an object to provide a carbon dioxide liquefaction system that can liquefy carbon dioxide contained in a carbon dioxide-containing gas with low energy consumption. [Means for solving the problem]

[0008] (1) The carbon dioxide liquefaction system according to the present invention comprises: a water ejector using water as a driving fluid and a carbon dioxide-containing gas as a suction fluid; a water drum that is provided downstream of the water ejector and that temporarily stores water and a carbon dioxide-containing gas; a water drum outlet gas line for discharging the carbon dioxide-containing gas from the gas layer in the water drum; a carbon dioxide-containing gas dehumidifier provided in the water drum outlet gas line for dehumidifying the carbon dioxide-containing gas; a carbon dioxide concentrator that concentrates the carbon dioxide contained in the carbon dioxide-containing gas dehumidified by the carbon dioxide-containing gas dehumidifier; and a carbon dioxide liquefaction device that liquefies carbon dioxide by cooling the carbon dioxide-containing gas in which carbon dioxide has been concentrated by the carbon dioxide concentrator.

[0009] (2) The carbon dioxide liquefaction system according to the present invention comprises: a water ejector using water as a driving fluid and a carbon dioxide-containing gas as a suction fluid; a water drum that is provided downstream of the water ejector and that temporarily stores water and a carbon dioxide-containing gas; a carbon dioxide concentrator that concentrates carbon dioxide contained in the carbon dioxide-containing gas received by the ejector; a water drum outlet gas line for discharging the carbon dioxide-containing gas from the gas layer of the water drum; a carbon dioxide-containing gas dehumidifier provided in the water drum outlet gas line for dehumidifying the carbon dioxide-containing gas; and a carbon dioxide liquefaction device that liquefies carbon dioxide by cooling the carbon dioxide-containing gas dehumidified by the carbon dioxide-containing gas dehumidification device.

[0010] (3) Furthermore, in the device described in (1) or (2) above, the carbon dioxide concentrator is characterized by having a carbon dioxide separation membrane that uses the differential pressure between the upstream and downstream streams as a driving force to preferentially allow carbon dioxide to permeate from the carbon dioxide-containing gas.

[0011] (4) In addition, in the device described in (1) above, the carbon dioxide concentrator has a carbon dioxide adsorbent that preferentially adsorbs and desorbs carbon dioxide, The carbon dioxide liquefaction device is a liquefied carbon dioxide ejector that uses liquefied carbon dioxide produced by cooling the high-concentration carbon dioxide-containing gas produced by the carbon dioxide concentrator as a driving fluid and uses the high-concentration carbon dioxide-containing gas produced by the carbon dioxide concentrator as a suction fluid; and a liquefied carbon dioxide drum that is arranged downstream of the liquefied carbon dioxide ejector and that temporarily stores liquefied carbon dioxide formed by condensing carbon dioxide contained in the high-concentration carbon dioxide-containing gas and the liquefied carbon dioxide that is the driving fluid.

[0012] (5) In addition, in the above-described (2), a carbon dioxide adsorption device is provided between the carbon dioxide-containing gas dehumidification device and the carbon dioxide liquefaction device, and the carbon dioxide adsorption device has a carbon dioxide adsorbent that preferentially adsorbs and desorbs carbon dioxide from the carbon dioxide-containing gas dehumidified by the carbon dioxide-containing gas dehumidification device, The carbon dioxide liquefaction device is a liquefied carbon dioxide ejector that uses liquefied carbon dioxide produced by cooling the high-concentration carbon dioxide-containing gas produced by the carbon dioxide concentrator as a driving fluid and that uses the high-concentration carbon dioxide-containing gas desorbed from the carbon dioxide adsorbent of the carbon dioxide adsorption device as a suction fluid; and a liquefied carbon dioxide drum that is arranged downstream of the liquefied carbon dioxide ejector and that temporarily stores liquefied carbon dioxide formed by condensing carbon dioxide contained in the high-concentration carbon dioxide-containing gas and the liquefied carbon dioxide that is the driving fluid. [Effects of the Invention]

[0013] According to the present invention, carbon dioxide contained in a carbon dioxide-containing gas can be liquefied with low energy. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram showing a carbon dioxide liquefaction system according to a first embodiment of the present invention. [Figure 2] FIG. 4 is a schematic diagram showing a carbon dioxide liquefaction system according to a second embodiment of the present invention. [Figure 3] FIG. 10 is a schematic diagram showing a carbon dioxide liquefaction system according to a third embodiment of the present invention. [Figure 4] FIG. 10 is a schematic diagram showing a carbon dioxide liquefaction system according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] [Embodiment 1] First, the configuration and functions of the first embodiment of the present invention will be described with reference to FIG. The carbon dioxide liquefaction system 1 according to the first embodiment of the present invention includes a water drum 10, a water pump 20, a water cooler 30, a water ejector 40, a dehumidifier 50, a carbon dioxide separation membrane 60, a carbon dioxide condenser 110, a liquefied carbon dioxide drum 120, and a liquefied carbon dioxide cooler 130.

[0016] The water drum 10 is a vertical cylindrical drum that temporarily stores the water received from the water ejector outlet line 74 .

[0017] The water pump 20 is a centrifugal pump that receives water temporarily stored in the water drum 10 through a water pump inlet line 71, pressurizes it, and discharges it to a water pump outlet line 72. The amount of pressure increase by the water pump 20 corresponds to the pressure loss within the system including the water cooler 30 and the water ejector 40.

[0018] The water cooler 30 is a typical shell-and-tube heat exchanger that cools the water received from the water pump outlet line 72 with a low-temperature refrigerant. The refrigerant is supplied from a refrigerant supply line 76 and is discharged to a refrigerant discharge line 77 after heat exchange. Although the cooler 30 is disposed downstream of the water pump 20 in FIG. 1, it may be disposed upstream of the water pump 20.

[0019] The water ejector 40 is a general ejector, which creates a reduced pressure state using water supplied from a water ejector inlet line 73 as a driving fluid, and receives exhaust gas from an exhaust gas receiving line 75 .

[0020] The dehumidifier 50 is a typical pressure swing adsorption (PSA) type dryer that switches between multiple cylinders filled with dehumidifying materials such as zeolite. It receives gas from the gas layer in the water drum 10 through the water drum outlet gas line 81, dehumidifies it, and discharges it to the dried exhaust gas line 83.

[0021] The carbon dioxide separation membrane 60 is a membrane separation unit made up of stacked carbon dioxide separation membranes made of polymeric materials, and utilizes the differential pressure between the dry exhaust gas line 83 and the carbon dioxide-enriched exhaust gas line 85 to concentrate carbon dioxide from the dry exhaust gas flowing through the dry exhaust gas line 83 and discharge it as carbon dioxide-enriched exhaust gas to the carbon dioxide-enriched exhaust gas line 85.

[0022] The carbon dioxide condenser 110 is a typical shell-and-tube type heat exchanger that cools the carbon dioxide-enriched exhaust gas by heat exchange with a low-temperature refrigerant supplied from the refrigerant supply line 86, thereby condensing the carbon dioxide contained in the carbon dioxide-enriched exhaust gas and discharging it to the liquefied carbon dioxide supply line 87.

[0023] The liquefied carbon dioxide drum 120 is a typical vertical cylindrical container that receives the liquefied carbon dioxide supplied from the liquefied carbon dioxide supply line 87 and non-condensable gases such as nitrogen and oxygen contained in the exhaust gas, separates them into a liquid layer and a gas layer, and temporarily stores them. The carbon dioxide condenser 110 and the liquefied carbon dioxide drum 120 constitute the carbon dioxide liquefaction apparatus of the present invention. The liquefied carbon dioxide accumulated at the bottom of the liquefied carbon dioxide drum 120 is discharged to the outside through a liquefied carbon dioxide discharge line 88, and the non-condensable gas accumulated at the top is discharged to the outside through a non-condensable gas discharge line 90. A non-condensable gas flow rate control valve 91 is provided in the non-condensable gas discharge line 90.

[0024] The liquefied carbon dioxide cooler 130 is a typical plate-type heat exchanger that cools the liquefied carbon dioxide by heat exchange between the liquefied carbon dioxide flowing through the liquefied carbon dioxide discharge line 88 and the decompressed non-condensable gas flowing through the non-condensable gas discharge line 90.

[0025] The non-condensable gas flow rate control valve 91 is a typical remotely controlled globe valve, and controls the flow rate while reducing the pressure of the gas in the gas layer of the liquefied carbon dioxide drum 120 to approximately atmospheric pressure.

[0026] Next, the operation of the carbon dioxide liquefaction system 1 according to this embodiment will be described. The carbon dioxide liquefaction system 1 circulates water within the system by operating the water pump 20. Water is stored in the water drum 10 at, for example, 1.2 MPaG and 5°C, and is pressurized by the water pump 20 to, for example, 1.9 MPaG.

[0027] The water pressurized by the water pump 20 is cooled in the water cooler 30 to a temperature within the range where the water will not solidify, for example, 3° C., by a refrigerant supplied from cold heat generating equipment (for example, a chiller) not shown.

[0028] The water cooled by the water cooler 30 is supplied to the water ejector 40, and a reduced pressure state is created by the water flowing at high speed through a small diameter portion inside the water ejector 40 using Bernoulli's principle. As a result, exhaust gas is supplied to the water ejector 40 from the exhaust gas receiving line 75. The composition of the exhaust gas is, for example, 5% carbon dioxide, 10% oxygen, 70% nitrogen, and 15% water.

[0029] Inside the water ejector 40, the high-speed flowing water mixes with the exhaust gas supplied from the exhaust gas receiving line 75. As the diameter of the water ejector 40 expands and the flow rate decreases, the pressure recovers to, for example, 1.2 MPaG, and the mixed exhaust gas is compressed and cooled.

[0030] At this time, the exhaust gas is compressed while coming into contact with the water and being cooled, so the compression process of the exhaust gas is close to isothermal compression, resulting in high compression efficiency. After the water ejector 40, a multiphase flow of water and exhaust gas flows through the ejector outlet line 74 toward the water drum 10.

[0031] The multiphase fluid of water and exhaust gas that flows into the water drum 10 becomes saturated at 1.2 MPaG and separates into a gas layer and a liquid layer. The amount of water held in the system increases as the moisture contained in the exhaust gas received from the exhaust gas receiving line 75 condenses. As a result, water equal to the condensed water is discharged from the water drum 10 to the outside via the water discharge line 78.

[0032] Furthermore, nitrogen, oxygen, and carbon dioxide do not condense and therefore accumulate in the gas layer of the water drum 10. Therefore, the gas layer of the water drum 10 is discharged to the outside of the drum through the water drum outlet gas line 81.

[0033] The exhaust gas discharged from the water drum outlet gas line 81 to the outside of the drum is supplied to the dehumidifier 50 at a pressure of 1.2 MPaG, where it is dehumidified to a dew point of approximately −70°C under atmospheric pressure, and then discharged to the dried exhaust gas supply line 83. Meanwhile, the humid purge gas generated in the dehumidifier 50 is discharged from the purge gas discharge line 82.

[0034] The dry exhaust gas discharged to the dry exhaust gas supply line 83 is supplied to the carbon dioxide separation membrane 60, where the carbon dioxide concentration is increased to about 50%, and the dry exhaust gas is discharged from the high-concentration carbon dioxide exhaust gas supply line 85. On the other hand, the non-permeated gas that did not permeate the carbon dioxide separation membrane 60 is discharged from the non-permeated gas discharge line 84.

[0035] The high-concentration carbon dioxide exhaust gas discharged to the high-concentration carbon dioxide exhaust gas supply line 85 is cooled to approximately -50°C in the carbon dioxide condenser 110. If the carbon dioxide concentration in the high-concentration carbon dioxide exhaust gas is 50%, the pressure losses in the dehumidifier 50 and the carbon dioxide separation membrane 60 are each 100 kPa, and the total pressure is 1.0 MPaG, the partial pressure of carbon dioxide will be 0.5 MPaG. Because carbon dioxide becomes liquid under conditions of -50°C, it condenses in the carbon dioxide condenser 110. The liquefied carbon dioxide and low-temperature nitrogen and oxygen are discharged to the liquefied carbon dioxide supply line 87.

[0036] The liquefied carbon dioxide and low-temperature nitrogen and oxygen discharged to the liquefied carbon dioxide supply line 87 are supplied to a liquefied carbon dioxide drum 120, where they are separated into liquefied carbon dioxide as a liquid layer and low-temperature nitrogen and oxygen as gas layers. The liquefied carbon dioxide is discharged to a liquefied carbon dioxide discharge line 88 and supplied to a liquefied carbon dioxide cooler 130. Meanwhile, the low-temperature nitrogen and oxygen are discharged from a non-condensed gas discharge line 90.

[0037] The low-temperature nitrogen and oxygen discharged to the non-condensable gas discharge line 90 is decompressed to approximately atmospheric pressure in the non-condensable gas flow control valve 91, and the temperature drops by several degrees Celsius due to the Joule-Thomson effect, and is supplied to the liquefied carbon dioxide cooler 130.

[0038] The liquefied carbon dioxide supplied to the liquefied carbon dioxide cooler 130 is cooled by heat exchange with nitrogen and oxygen that are at a lower temperature than the internal temperature of the liquefied carbon dioxide drum 120. The low-temperature nitrogen and oxygen that have cooled the liquefied carbon dioxide in the liquefied carbon dioxide cooler 130 are discharged to the outside.

[0039] According to the carbon dioxide liquefaction system 1 of this embodiment, the reduced pressure state created by the water ejector 40 can be utilized to take in exhaust gas and increase the pressure of the exhaust gas by pressure recovery downstream of the water ejector 40, so that the pressure required to liquefy carbon dioxide can be obtained with less power than a compressor.

[0040] Furthermore, according to the carbon dioxide liquefaction system 1 of this embodiment, the pressure recovery process downstream of the water ejector 40 described above is carried out while in contact with low-temperature water, which is close to isothermal compression, and therefore the exhaust gas can be compressed efficiently.

[0041] Furthermore, according to the carbon dioxide liquefaction system 1 of this embodiment, exhaust gas with a high concentration and a high carbon dioxide partial pressure can be obtained by passing the exhaust gas through the dehumidifier 50 and the carbon dioxide separation membrane 60 using the pressure obtained by the water ejector 40, and only the carbon dioxide can be liquefied by cooling, so that the separation and liquefaction of carbon dioxide from the exhaust gas can be performed comprehensively.

[0042] Furthermore, according to the carbon dioxide liquefaction system 1 of this embodiment, the temperature of the non-condensable gas can be made lower than that inside the liquefied carbon dioxide drum 120 by reducing the pressure in the non-condensable gas flow control valve 91, and this low-temperature non-condensable gas can be used to cool the liquefied carbon dioxide in the liquefied carbon dioxide cooler 130, thereby reducing the thermal load on the carbon dioxide condenser 110 and reducing the energy consumption of the entire system.

[0043] In this embodiment, the water ejector 40 is described as receiving exhaust gas, but the present invention is not limited to exhaust gas. Gases containing carbon dioxide, such as the atmosphere or gases with an increased carbon dioxide concentration from the atmosphere, or gases produced by steam reforming of hydrocarbon gas, can also be used.

[0044] Furthermore, in this embodiment, the dehumidifier 50 has been described as a pressure swing adsorption (PSA) type dryer, but a thermal swing adsorption (TSA) type dryer in which the adsorbent is regenerated by heating may also be used.

[0045] Furthermore, in this embodiment, a membrane separation unit in which carbon dioxide separation membranes made of a polymer material are stacked as the carbon dioxide concentrator is exemplified as an example of the carbon dioxide concentrator, but the carbon dioxide concentrator according to the present invention is not limited to this and may use an inorganic material such as zeolite, or a hybrid type membrane of both, or may have a multi-stage configuration in series. The number and configuration of the carbon dioxide concentrators are selected appropriately according to the design conditions. This also applies to the following embodiments 2 and 4.

[0046] In addition, in the present embodiment, the non-permeable gas from the carbon dioxide separation membrane 60 is described as being discharged to the outside, but it may be used for cooling purposes within the system after reducing the pressure and lowering the temperature. For example, by cooling the exhaust gas in the exhaust gas receiving line 75, the moisture content can be reduced, and the amount of carbon dioxide received by the water ejector 40 can be increased. Furthermore, by cooling the water drum outlet gas flowing through the water drum outlet gas line 81, the moisture content can be reduced, thereby reducing the load on the dehumidifier 50. Furthermore, by cooling the carbon dioxide-enriched exhaust gas flowing through the carbon dioxide-enriched exhaust gas line 85, the thermal load on the carbon dioxide condenser 110 can be reduced.

[0047] Furthermore, in this embodiment, it has been described that the low-temperature nitrogen and oxygen obtained by cooling the liquefied carbon dioxide in the liquefied carbon dioxide cooler 130 are discharged to the outside, but the low temperature may also be used for cooling purposes within the system. For example, by cooling the carbon dioxide-enriched exhaust gas flowing through the carbon dioxide-enriched exhaust gas line 85, the thermal load of the carbon dioxide condenser 110 can be reduced.

[0048] [Embodiment 2] Next, the configuration and functions of the second embodiment will be described with reference to FIG. The same numbers are used for components having the same configurations and functions as those in the first embodiment. The carbon dioxide liquefaction system according to the second embodiment includes an exhaust gas pre-dryer 210 and a carbon dioxide separation membrane 220.

[0049] The exhaust gas pre-dryer 210 is a typical temperature swing adsorption (TSA) type dryer that uses multiple cylinders filled with dehumidifying materials such as zeolite by switching between them. It dehumidifies the exhaust gas received from the exhaust gas receiving line 75, lowers the dew point to a level that meets the requirements of the carbon dioxide separation membrane 220, and discharges it to the pre-dried exhaust gas supply line 271.

[0050] The carbon dioxide separation membrane 220 is a membrane separation unit made of a stack of carbon dioxide separation membranes made of a polymer material, and utilizes the pressure difference between the pre-dry exhaust gas supply line 271 and the carbon dioxide-enriched exhaust gas receiving line 273 to concentrate carbon dioxide from the pre-dry exhaust gas flowing through the pre-dry exhaust gas supply line 271 and discharge it as carbon dioxide-enriched exhaust gas to the carbon dioxide-enriched exhaust gas receiving line 273.

[0051] Next, the operation of the carbon dioxide liquefaction system 200 according to this embodiment will be described. The explanation of the same functions as those in the first embodiment will be omitted.

[0052] The exhaust gas received from the exhaust gas receiving line 75 is dehumidified in the exhaust gas pre-dryer 210 so that the dew point is lower than the saturation temperature by about 10° C., for example, and is then supplied to the carbon dioxide separation membrane 220 .

[0053] The pre-dried flue gas supplied to the carbon dioxide separation membrane 220 is concentrated in the carbon dioxide separation membrane 220 until the carbon dioxide concentration reaches, for example, 10% to 50%, and is supplied to the water ejector 40 via a carbon dioxide concentrated flue gas receiving line 273. The non-permeated gas of the pre-drying flue gas that did not permeate the carbon dioxide separation membrane 220 is discharged to the outside through a non-permeated gas discharge line 272.

[0054] The carbon dioxide-enriched flue gas received by the water ejector 40 is pressurized as the pressure recovers downstream of the water ejector 40, and is supplied to the water drum 10 together with the circulating water. The inside of the water drum 10 is saturated at 1.2 MPaG, and part of the water contained in the carbon dioxide-enriched flue gas condenses due to the cooling effect of the water. The condensed water is discharged to the outside via a water discharge line 78.

[0055] In the water drum 10, the carbon dioxide-enriched exhaust gas moves to the gas layer and is supplied to the dehumidifier 50 through the water drum outlet gas line 81.

[0056] The high-concentration carbon dioxide dried exhaust gas, which has consumed a differential pressure of 100 kPa in the dehumidifier 50 and has a pressure of 1.1 MPaG and an atmospheric dew point of −70° C., is supplied to the carbon dioxide condenser 110 through the dried exhaust gas line 83 .

[0057] In the carbon dioxide condenser 110, the high-concentration carbon dioxide dried exhaust gas is cooled to −50° C., and due to the high partial pressure of carbon dioxide (partial pressure 0.55 MPaG compared to total pressure 1.1 MPaG), only carbon dioxide is condensed and supplied to the liquefied carbon dioxide drum 120.

[0058] According to the carbon dioxide liquefaction system 200 of this embodiment, the carbon dioxide in the exhaust gas is concentrated by the carbon dioxide separation membrane 220 before being received in the water ejector 40, so that it is possible to reduce the circulating flow rate of water per unit mass of carbon dioxide and reduce the power of the water pump 20. As a result, it is possible to separate and liquefy carbon dioxide from the exhaust gas with less energy.

[0059] [Embodiment 3] Next, the configuration and functions of the third embodiment will be described with reference to FIG. The same numbers are used for components having the same configurations and functions as those in the first embodiment. The carbon dioxide liquefaction system 300 according to the third embodiment includes a liquefied carbon dioxide drum 310 , a liquefied carbon dioxide pump 320 , a liquefied carbon dioxide cooler 330 , a liquefied carbon dioxide ejector 340 , and a carbon dioxide adsorption device 350 .

[0060] The liquefied carbon dioxide drum 310 is a vertical cylindrical drum that temporarily stores the liquefied carbon dioxide received from the ejector outlet line 374 .

[0061] The liquefied carbon dioxide pump 320 is a centrifugal pump that receives liquefied carbon dioxide temporarily stored in the liquefied carbon dioxide drum 310 through a liquefied carbon dioxide pump inlet line 371, pressurizes the liquefied carbon dioxide, and delivers it to a liquefied carbon dioxide pump outlet line 372. The pressure increase range of the liquefied carbon dioxide pump 320 corresponds to the pressure loss in the system including the liquefied carbon dioxide cooler 330 and the liquefied carbon dioxide ejector 340 .

[0062] The liquefied carbon dioxide cooler 330 is a typical shell-and-tube heat exchanger, and cools the liquefied carbon dioxide received from the liquefied carbon dioxide pump outlet line 372 using a low-temperature refrigerant. The refrigerant is supplied from a refrigerant supply line 375 and is discharged to a refrigerant discharge line 376 after heat exchange. In FIG. 3, the liquefied carbon dioxide cooler 330 is disposed downstream of the liquefied carbon dioxide pump 320, but it may be disposed upstream of the liquefied carbon dioxide water pump 320.

[0063] The liquefied carbon dioxide ejector 340 is a general ejector, which creates a reduced pressure state using liquefied carbon dioxide supplied from an ejector inlet line 373 as a driving fluid, and receives a high-concentration carbon dioxide containing gas from a high-concentration carbon dioxide containing gas supply line 378 . The liquefied carbon dioxide drum 310, the liquefied carbon dioxide pump 320, the liquefied carbon dioxide cooler 330, and the liquefied carbon dioxide ejector 340 in this embodiment constitute the carbon dioxide liquefaction device of the present invention. However, in the carbon dioxide liquefaction apparatus of the present invention, it is not necessarily required to circulate liquefied carbon dioxide, and liquefied carbon dioxide may be supplied from the outside to the liquefied carbon dioxide ejector 340. In this case, the carbon dioxide liquefaction apparatus of the present invention can be composed of the liquefied carbon dioxide drum 310 and the liquefied carbon dioxide ejector 340.

[0064] The carbon dioxide adsorption device 350 is a typical temperature swing adsorption (TSA) type carbon dioxide adsorption device that uses multiple cylinders filled with dehumidifying material such as zeolite by switching between them. It adsorbs carbon dioxide from the dry exhaust gas received from the dry exhaust gas line 83, discharges nitrogen and oxygen to the outside through the excess gas line 377, and delivers the high-concentration carbon dioxide-containing gas to the high-concentration carbon dioxide-containing gas supply line 378.

[0065] Next, the operation of the carbon dioxide liquefaction system 300 according to this embodiment will be described. The explanation of the same functions as those in the first embodiment will be omitted.

[0066] The dried exhaust gas supplied from the dried exhaust gas line 83 to the carbon dioxide adsorption device 350 has its carbon dioxide concentration increased in the carbon dioxide adsorption device 350 to become a gas containing high concentration carbon dioxide, which is then discharged to a high concentration carbon dioxide containing gas supply line 378. On the other hand, the dried nitrogen and oxygen with reduced carbon dioxide concentration are discharged to the outside through a surplus gas line 377.

[0067] The liquefied carbon dioxide pump 20 circulates the liquefied carbon dioxide within a flow path including the liquefied carbon dioxide drum 310 and the liquefied carbon dioxide ejector 340. In the liquefied carbon dioxide drum 310, the liquefied carbon dioxide is stored at, for example, 0.9 MPaG and −50° C., and is pressurized by the liquefied carbon dioxide pump 320 to, for example, 1.6 MPaG.

[0068] The liquefied carbon dioxide pressurized by the liquefied carbon dioxide pump 320 is cooled in the liquefied carbon dioxide cooler 330 to a temperature range where it will not solidify, for example, -53°C, using a refrigerant supplied by cold heat generation equipment (e.g., a refrigerator) not shown.

[0069] The liquefied carbon dioxide cooled by the liquefied carbon dioxide cooler 330 is supplied to the liquefied carbon dioxide ejector 340, and flows as a high-speed flow through the small diameter portion inside the liquefied carbon dioxide ejector 340, creating a reduced pressure state using Bernoulli's theorem.

[0070] As a result, the high-concentration carbon dioxide-containing gas supply line 378 is put into a reduced pressure state, and a high-concentration carbon dioxide-containing gas containing, for example, 50% carbon dioxide and other excess gases for regeneration such as nitrogen and oxygen is supplied from the carbon dioxide adsorption device 350 to the liquefied carbon dioxide ejector 340.

[0071] Inside the liquefied carbon dioxide ejector 340, the high-concentration carbon dioxide-containing gas supplied from the high-concentration carbon dioxide-containing gas supply line 378 mixes with the high-speed flowing liquefied carbon dioxide. As the diameter expands inside the liquefied carbon dioxide ejector 340 and the flow rate decreases, the pressure recovers to, for example, 0.9 MPaG, and the mixed carbon dioxide gas is compressed, cooled, and condensed. In addition, nitrogen and oxygen are compressed and cooled as the pressure recovers.

[0072] In this case, carbon dioxide, nitrogen, and oxygen are compressed while coming into contact with the liquefied carbon dioxide and being cooled, and therefore the compression process of these gases is close to isothermal compression, resulting in high compression efficiency.

[0073] In the downstream of the liquefied carbon dioxide ejector 340, liquefied carbon dioxide flows through the ejector outlet line 374 towards the liquefied carbon dioxide drum 310, but if there is carbon dioxide gas that has not been completely condensed inside the liquefied carbon dioxide ejector 340, this will also be included, and uncondensed nitrogen and oxygen will also be included in the gaseous state, resulting in a multiphase flow.

[0074] The liquefied carbon dioxide that flows into the liquefied carbon dioxide drum 310 becomes saturated at 0.9 MPaG and separates into a gas layer and a liquid layer. The amount of carbon dioxide held in the system increases as carbon dioxide gas is supplied from the high-concentration carbon dioxide-containing gas supply line 378. As a result, liquefied carbon dioxide is discharged from the liquefied carbon dioxide drum 310 to the outside via the liquefied carbon dioxide discharge line 379 in an amount equal to the amount of carbon dioxide gas that has been supplied.

[0075] Furthermore, since nitrogen and oxygen do not condense, they accumulate in the gas layer of the liquefied carbon dioxide drum 310, and are discharged to the outside through the non-condensed gas discharge line 381 connected to the top of the liquefied carbon dioxide drum 310.

[0076] According to the carbon dioxide liquefaction system 300 of this embodiment, even when a gas containing high concentration of carbon dioxide is extracted in a low-pressure state by the carbon dioxide adsorption device 350 from the high-pressure exhaust gas discharged from the water drum 10, the gas can be received in the liquefied carbon dioxide ejector 340 and pressurized, and only the carbon dioxide gas can be condensed. Therefore, it is possible to reduce the energy required not only for separation of carbon dioxide but also for liquefaction at the same time.

[0077] Furthermore, according to the carbon dioxide liquefaction system 300 of this embodiment, dry nitrogen and oxygen are discharged from the carbon dioxide adsorption device 350 in a high-pressure state, and therefore, by installing equipment that requires high-pressure dry air, such as cryogenic separation, in addition, the energy required for that equipment can also be reduced.

[0078] Furthermore, in this embodiment, the carbon dioxide adsorption device 350 has been described as being of a thermal swing adsorption (TSA) type, but it may also be of a pressure swing adsorption (PSA) type in which the adsorbent is regenerated by a pressure difference.

[0079] [Embodiment 4] Next, the configuration and functions of the fourth embodiment will be described with reference to FIG. The same numbers are used for components having the same configurations and functions as those in the first and third embodiments. The carbon dioxide liquefaction system 400 according to the fourth embodiment has the same configuration as the third embodiment, and further includes the flue gas pre-dryer 210 and the carbon dioxide separation membrane 220 according to the second embodiment.

[0080] Next, the operation of the carbon dioxide liquefaction system 400 according to this embodiment will be described. The explanation of the same functions as those in the second and third embodiments will be omitted. The carbon dioxide-enriched exhaust gas, in which the carbon dioxide concentration has been increased to about 50% by the carbon dioxide separation membrane 220, is received by the water ejector 40. The subsequent operations are the same as those in the third embodiment.

[0081] According to the carbon dioxide liquefaction system 400 of this embodiment, carbon dioxide-enriched exhaust gas is produced by the carbon dioxide separation membrane 220, and the gas is pressurized by the water ejector 40 and supplied to the carbon dioxide adsorption device 350. This makes it possible to significantly reduce the energy consumption per mass of carbon dioxide in the carbon dioxide adsorption device 350. Consequently, it is possible to significantly reduce the power required for separating and liquefying carbon dioxide. [Industrial Applicability]

[0082] The present invention can be used as a carbon dioxide liquefaction system that can liquefy carbon dioxide contained in a carbon dioxide-containing gas with low energy consumption. [Explanation of symbols]

[0083] 1. Carbon dioxide liquefaction system 10 water drums 20 Water Pump 30 water cooler 40 Water ejector 50 Dehumidifier 60 Carbon dioxide separation membrane 71 Water pump inlet line 72 Water pump outlet line 73 Water ejector inlet line 74 Water ejector outlet line 75 Exhaust gas receiving line 76 Refrigerant supply line 77 Refrigerant discharge line 78 Water Dispensing Line 81 Water drum outlet gas line 82 Purge gas discharge line 83 Dry exhaust gas line 84 Non-permeable gas discharge line 85 High concentration carbon dioxide exhaust gas supply line 86 Refrigerant supply line 87 Liquefied carbon dioxide supply line 90 Non-condensable gas discharge line 91 Non-condensable gas flow control valve 110 Carbon dioxide condenser 120 liquefied carbon dioxide drums 130 Liquefied Carbon Dioxide Cooler 200 Carbon dioxide liquefaction system (embodiment 2) 210 Exhaust gas pre-dryer 220 Carbon dioxide separation membrane 271 Pre-dried exhaust gas supply line 272 Non-permeable gas discharge line 273 Carbon dioxide enriched exhaust gas receiving line 300 Carbon dioxide liquefaction system (embodiment 3) 310 Liquefied Carbon Dioxide Drums 320 Liquefied Carbon Dioxide Pump 330 Liquefied Carbon Dioxide Cooler 340 Liquefied Carbon Dioxide Ejector 350 Carbon dioxide adsorption device 371 Liquefied carbon dioxide pump inlet line 372 Liquefied carbon dioxide pump outlet line 373 Ejector inlet line 374 Ejector outlet line 375 Refrigerant supply line 376 Refrigerant discharge line 377 Surplus Gas Line 378 High-concentration carbon dioxide gas supply line 379 Liquefied carbon dioxide discharge line 400 Carbon dioxide liquefaction system (embodiment 4)

Claims

1. a water ejector using water as a driving fluid and a carbon dioxide-containing gas as a suction fluid; a water drum that is provided downstream of the water ejector and that temporarily stores water and a carbon dioxide-containing gas; a water drum outlet gas line for discharging the carbon dioxide-containing gas from the gas layer in the water drum; a carbon dioxide-containing gas dehumidifier provided in the water drum outlet gas line for dehumidifying the carbon dioxide-containing gas; a carbon dioxide concentrator that concentrates the carbon dioxide contained in the carbon dioxide-containing gas dehumidified by the carbon dioxide-containing gas dehumidifier; a carbon dioxide liquefaction device that liquefies carbon dioxide by cooling the carbon dioxide-containing gas in which carbon dioxide has been concentrated by the carbon dioxide concentrator.

2. a water ejector using water as a driving fluid and a carbon dioxide-containing gas as a suction fluid; a water drum that is provided downstream of the water ejector and that temporarily stores water and a carbon dioxide-containing gas; a carbon dioxide concentrator that concentrates carbon dioxide contained in the carbon dioxide-containing gas received by the ejector; a water drum outlet gas line for discharging the carbon dioxide-containing gas from the gas layer of the water drum; a carbon dioxide-containing gas dehumidifier provided in the water drum outlet gas line for dehumidifying the carbon dioxide-containing gas; a carbon dioxide liquefaction device that liquefies carbon dioxide by cooling the carbon dioxide-containing gas dehumidified by the carbon dioxide-containing gas dehumidification device.

3. The carbon dioxide liquefaction system according to claim 1 or 2, characterized in that the carbon dioxide concentrator has a carbon dioxide separation membrane that preferentially permeates carbon dioxide from the carbon dioxide-containing gas using the differential pressure between the upstream and downstream streams as a driving force.

4. the carbon dioxide concentrator has a carbon dioxide adsorbent that preferentially adsorbs and desorbs carbon dioxide, The carbon dioxide liquefaction device is a liquefied carbon dioxide ejector that uses liquefied carbon dioxide produced by cooling the high-concentration carbon dioxide-containing gas produced by the carbon dioxide concentrator as a driving fluid and uses the high-concentration carbon dioxide-containing gas produced by the carbon dioxide concentrator as a suction fluid; The carbon dioxide liquefaction system described in claim 1, characterized in that it comprises a liquefied carbon dioxide drum arranged downstream of the liquefied carbon dioxide ejector and temporarily storing liquefied carbon dioxide formed by condensing carbon dioxide contained in the high concentration carbon dioxide-containing gas and the liquefied carbon dioxide of the driving fluid.

5. a carbon dioxide adsorption device disposed between the carbon dioxide-containing gas dehumidification device and the carbon dioxide liquefaction device, the carbon dioxide adsorption device having a carbon dioxide adsorbent that preferentially adsorbs and desorbs carbon dioxide from the carbon dioxide-containing gas dehumidified by the carbon dioxide-containing gas dehumidification device; The carbon dioxide liquefaction device is a liquefied carbon dioxide ejector that uses liquefied carbon dioxide produced by cooling the high-concentration carbon dioxide-containing gas produced by the carbon dioxide concentrator as a driving fluid and that uses the high-concentration carbon dioxide-containing gas desorbed from the carbon dioxide adsorbent of the carbon dioxide adsorption device as a suction fluid; The carbon dioxide liquefaction system according to claim 2, further comprising: a liquefied carbon dioxide drum arranged downstream of the liquefied carbon dioxide ejector for temporarily storing liquefied carbon dioxide formed by condensing carbon dioxide contained in the high-concentration carbon dioxide-containing gas and the liquefied carbon dioxide serving as a driving fluid.

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