Carbon dioxide capture device

Abstract

Providing carbon dioxide capture equipment that reduces energy consumption for melting and vaporizing dry ice. [Solution] A carbon dioxide recovery device 10 comprises a separation and recovery unit 20 for separating carbon dioxide from a gas G1 containing carbon dioxide, and a sublimation tank 15 equipped with a refrigerant circuit for passing a refrigerant through which carbon dioxide supplied from the separation and recovery unit 20 is sublimated (solidified). The device further comprises a reheater 17 for heating the carbon dioxide recovered from the sublimation tank 15, a carbon dioxide storage tank 16 for storing the liquefied carbon dioxide, and a liquid transfer means for increasing the pressure of the carbon dioxide recovered from the sublimation tank 15. The sublimation tank 15 includes a first sublimation tank 15A and a second sublimation tank 15B, which are provided connected in parallel to the piping from the carbon dioxide storage tank 16. The device also includes switching means (first valve V1 and second valve V2) for selectively switching the piping connected to the sublimation tank 15, and connecting piping LE and a communication valve VE for connecting the sublimators 15 to each other.

Description

Technical Field

[0001] The present invention relates to a carbon dioxide recovery device including a separation device for separating carbon dioxide from a gas containing carbon dioxide.

Background Art

[0002] In recent years, internationally, attempts have been made to reduce the amount of carbon dioxide emitted into the atmosphere in order to solve the problem of climate change, and it is predicted that the consumption of fossil fuels will decrease due to the promotion of electrification. On the other hand, the demand for dry ice used in beverage applications and logistics has not decreased. As a result, it is expected that it will be difficult to supply high-concentration carbon dioxide gas as a raw material. For this reason, there is a demand for a technology that can efficiently recover only carbon dioxide from low-concentration carbon dioxide emission sources such as the atmosphere or combustion exhaust gas.

[0003] Patent Document 1 discloses a technology related to a carbon dioxide recovery device. In a carbon dioxide recovery device including a separation device for separating carbon dioxide from a separated gas containing carbon dioxide, in order from the upstream where the separated gas is supplied, a separation device and a carbon dioxide sublimator for sublimating the carbon dioxide separated in the separation device are connected in series. A refrigerant circuit using a fluid having cold heat as a refrigerant is connected to the carbon dioxide sublimator, and sublimation of carbon dioxide is performed by the refrigerant. When sublimation of carbon dioxide is performed, the carbon dioxide sublimator is depressurized, and suction of the carbon dioxide separated in the separation device is performed by becoming a negative pressure.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, Patent Document 1 does not mention any specific method for sublimating carbon dioxide in order to recover it. To sublimate or melt solidified carbon dioxide (dry ice), one possible method is to flow a high-temperature heat transfer medium through a carbon dioxide sublimator instead of a refrigerant and exchange heat with the dry ice. However, if liquefied carbon dioxide produced as a heat refrigerant is used, for example, a large amount of liquefied carbon dioxide is required to secure the amount of liquefied carbon dioxide needed for use in the production process. However, producing a large amount of liquefied carbon dioxide requires repeating the production process, which is time-consuming, so there is a need to improve the efficiency of this production process.

[0006] Therefore, the present invention aims to provide a carbon dioxide recovery device that can reduce the amount of refrigerant required for depressurization and melting in order to solve these problems. [Means for solving the problem]

[0007] To achieve the above objective, a carbon dioxide recovery device 10 according to one aspect of the present invention has the following features.

[0008] (1) A carbon dioxide recovery apparatus comprising a separation device for separating carbon dioxide from a gas to be separated that contains carbon dioxide, and a sublimator equipped with a refrigerant circuit through which a refrigerant passes and for sublimating (solidifying) the carbon dioxide supplied from the separation device, A dewarmer for heating the carbon dioxide recovered from the sublimator, A carbon dioxide storage tank for storing the liquefied carbon dioxide, The system includes a liquid transfer means for increasing the pressure of the carbon dioxide recovered from the sublimator, The sublimation apparatus includes a first sublimation apparatus and a second sublimation apparatus, which are installed connected in parallel to the piping from the carbon dioxide storage tank. The system includes a switching means for selectively switching the piping connected to the sublimator, connecting piping for connecting the sublimators to each other, and a valve for opening and closing the piping. The carbon dioxide that has been sublimated (solidified) in the sublimator is dissolved by the liquefied carbon dioxide supplied from the liquefied carbon dioxide storage tank. It is characterized by the following.

[0009] As described in (1) above, it becomes possible to exchange pressure between the first sublimator and the second sublimator, and as a result, the volume of heat transfer medium required for the operation of the carbon dioxide recovery device can be reduced. In other words, it can contribute to reducing energy consumption. This is achieved by providing two sublimators, a first sublimator and a second sublimator, and selectively switching the piping connected to each sublimator during operation, thereby shifting the timing of the operation process. For example, if the first sublimator is at high temperature and high pressure while the second sublimator is at low temperature and low pressure, it becomes possible to exchange pressure between the sublimators by opening the valves in the connecting piping that connects the two sublimators and allowing them to communicate.

[0010] As a result, the amount of refrigerant used for pressurization or depressurization can be reduced, thereby lowering the energy consumption required to melt and vaporize dry ice. Depending on the size of the sublimator, the reduction in operating costs may outweigh the increase in construction costs, thus contributing to overall cost reduction.

[0011] (2) In the carbon dioxide recovery device described in (1), The sublimator includes a third sublimator, The aforementioned connecting pipe is A first connecting pipe connecting the first sublimator and the second sublimator, A second connecting pipe connecting the second sublimator and the third sublimator, The system includes a third connecting pipe connecting the third sublimator and the first sublimator, The aforementioned valve is A first valve provided in the first connecting pipe, A second valve provided in the second connecting pipe, The third valve provided in the third connecting pipe, It is preferable.

[0012] According to the aspect described in (2) above, by providing the third sublimator, it is possible to reduce the energy consumption by combining it with the first sublimator and the second sublimator. This is because when the operation process is classified into four processes: solidification process, pressure boosting process, liquid extraction process, and pressure reduction process, the process of sublimating (solidifying) carbon dioxide requires the most time, and there are cases where it can be operated more efficiently by combining the third sublimator rather than only the first sublimator and the second sublimator.

[0013] (3) In the carbon dioxide recovery device described in (1), the separation device is connected to the first sublimator and the second sublimator, the first sublimator and the second sublimator are connected to the rewarming device, the rewarming device is connected to the carbon dioxide storage tank via the liquid feeding means, the carbon dioxide storage tank is connected to the first sublimator and the second sublimator, it is preferable that the carbon dioxide storage tank is provided with an outlet for taking out liquefied carbon dioxide as a product. is preferred.

[0014] According to the aspect described in (3) above, it becomes possible to take out liquefied carbon dioxide as a product from the carbon dioxide storage tank. By adjusting the temperature by the rewarming device and the pressure by the liquid feeding means, liquefied carbon dioxide at an appropriate temperature and pressure can be taken out from the carbon dioxide storage tank.

Brief Description of Drawings

[0015] [Figure 1] It is a schematic diagram showing the configuration of the carbon dioxide recovery device of the first embodiment. [Figure 2] It is a conceptual diagram showing a cycle that does not require heating in the first embodiment. [Figure 3] It is a conceptual diagram when the pressure is shared between the sublimation tanks for equalization in the first embodiment. [Figure 4] It is a flowchart regarding the operation of the liquefaction recovery section in the first embodiment. [Figure 5] Flowchart of the depressurization process according to the first embodiment. [Figure 6] Flowchart of the pressurization process according to the first embodiment. [Figure 7] Flowchart of the liquid extraction process according to the first embodiment. [Figure 8] Flowchart of the depressurization process according to the first embodiment. [Figure 9] Comparison of the volume of the heat medium required for the depressurization process according to the first embodiment. [Figure 10] Comparison of the volume of the heat medium required for the pressurization process according to the first embodiment. [Figure 11] Conceptual diagram when pressure is supplied from the carbon dioxide storage tank in the second embodiment. [Figure 12] Schematic diagram showing the configuration of the carbon dioxide recovery device in the third embodiment.

Mode for Carrying Out the Invention

[0016] First, the first embodiment of the present invention will be described with reference to the drawings. FIG. 1 schematically shows the configuration of a carbon dioxide recovery device 10 according to the first embodiment. The carbon dioxide recovery device 10 includes a separation and recovery unit 20 (not shown but including an absorption tower and a regeneration tower), and a liquefaction and recovery unit 30 including a sublimation tank 15, a reheater 17, and a carbon dioxide storage tank 16. The separation and recovery unit 20 extracts carbon dioxide, and the liquefaction and recovery unit 30 recovers the liquefied carbon dioxide.

[0017] First, the separation and recovery unit 20 provided in the carbon dioxide recovery device 10 will be described. A separated gas G1 is supplied to the separation and recovery unit 20. From the gas supply line L11, for example, combustion exhaust gas (separated gas G1) generated in a power plant, a steel mill, or a cement factory is supplied. The combustion exhaust gas contains about 20% or less of carbon dioxide, and in addition, nitrogen, oxygen, water vapor, etc. are included. Note that since there are cases where the combustion exhaust gas contains sulfur oxides, nitrogen oxides, and dust, a desulfurization device, a denitration device, a dust collector, etc. may be provided in the middle of the gas supply line L11.

[0018] The gas to be separated G1 can include not only combustion exhaust gas, but also air, biogas, or off-gases containing carbon dioxide generated from heat treatment passages such as carburizing furnaces or chemical equipment. Amine-based aqueous solutions or physical absorbents can be used as absorbents. Note that this does not preclude the use of alternative substances with comparable properties.

[0019] The separation and recovery unit 20 is provided with a gas supply channel L11 for supplying the aforementioned gas to be separated G1 and a discharge channel L12 for discharging the treated gas G2 from which carbon dioxide has been removed. The treated gas G2 is the gas remaining after carbon dioxide has been removed by the absorbent liquid provided inside the separation and recovery unit 20, and consists of nitrogen, oxygen, and water vapor. Regarding the separation of carbon dioxide, although the gas to be separated G1 was separated using an absorbent liquid, there is no prejudice to using any method that can be driven or regenerated by reduced pressure. Examples include non-volatile chemical absorbents, adsorbents, solid absorbents, and separation membranes. It is desirable to select a method that can efficiently separate the gas to be separated G1.

[0020] Next, the liquefaction and recovery unit 30 will be described. The first transport pipe L13 connected to the separation and recovery unit 20 is branched into the first branch pipe L14 and the second branch pipe L15, which are connected to the first sublimation tank 15A and the second sublimation tank 15B. The sublimation tanks 15 (first sublimation tank 15A and second sublimation tank 15B) are equipped with the function of sublimating (solidifying) the carbon dioxide (gas) supplied from the separation and recovery unit 20. The sublimation tanks 15 are connected to a cooling circuit that is configured to exchange heat with refrigerant tanks (first refrigerant storage tank 19A and second refrigerant storage tank 19B). LNG or the like is used as the refrigerant.

[0021] The first sublimation tank 15A and the second sublimation tank 15B are piped in parallel, and a connecting pipe LE and a communication valve VE are provided between them, so that the sublimation tanks 15 can exchange pressure with each other. The first branch pipe L14, which branches off from the first transport pipe L13, is connected to the first sublimation tank 15A, and the second branch pipe L15, which branches off from the first transport pipe L13, is connected to the second sublimation tank 15B. The first branch pipe L14 is provided with a first valve V1, and the second branch pipe L15 is provided with a second valve V2, so that the separation and recovery unit 20 can be selectively connected to or disconnected from the first sublimation tank 15A and the second sublimation tank 15B.

[0022] The first sublimation tank 15A is connected to the first pump Pu1 via the third branch pipe L16. The third branch pipe L16 is equipped with a fifth valve V5. The second sublimation tank 15B is connected to the first pump Pu1 via the fourth branch pipe L17. The fourth branch pipe L17 is equipped with a sixth valve V6. Therefore, the fifth valve V5 and the sixth valve V6 allow for selective communication and disconnection between the first sublimation tank 15A and the second sublimation tank 15B and the first pump Pu1.

[0023] In the dewarmer 17, liquid or gaseous carbon dioxide in the piping is heated by heat exchange. The first pump Pu1 is connected to the dewarmer 17 by the second transport pipe L18, the dewarmer 17 is connected to the second pump Pu2 by the third transport pipe L19, and the second pump Pu2 is connected to the carbon dioxide storage tank 16 by the fourth transport pipe L20. The dewarmer 17 has the function of raising the temperature by heat exchange with carbon dioxide (gas) or carbon dioxide (liquid) supplied from the second transport pipe L18. The carbon dioxide storage tank 16 has the function of storing a certain amount of carbon dioxide (gas) or carbon dioxide (liquid), and an extraction pipe L24 is connected to it so that liquefied carbon dioxide Lc can be extracted as a product.

[0024] The carbon dioxide storage tank 16 is connected to the sublimation tank 15 by a fifth transport pipe L21. The fifth transport pipe L21 is branched into a fifth branch pipe L22 and a sixth branch pipe L23. The fifth branch pipe L22 is connected to the first sublimation tank 15A, and the sixth branch pipe L23 is connected to the second sublimation tank 15B. A third valve V3 is provided in the fifth branch pipe L22, and a fourth valve V4 is provided in the sixth branch pipe L23, allowing for selective communication and disconnection between the carbon dioxide storage tank 16 and the first sublimation tank 15A and the second sublimation tank 15B.

[0025] The supply of refrigerant to the sublimation tank 15 is achieved by connecting to the first refrigerant storage tank 19A and the second refrigerant storage tank 19B. Specifically, the first refrigerant piping L31 connected to the first refrigerant storage tank 19A is branched into a first refrigerant branch pipe L32 and a second refrigerant branch pipe L33. The first refrigerant branch pipe L32 is connected to a heat exchanger located in the first sublimation tank 15A, and is connected and disconnected by a seventh valve V7. The second refrigerant branch pipe L33 is connected to a heat exchanger located in the second sublimation tank 15B, and is connected and disconnected by an eighth valve V8.

[0026] The third refrigerant branch pipe L34 is connected from the heat exchanger of the first sublimation tank 15A to the second cooling pipe L36, the fourth refrigerant branch pipe L35 is connected from the heat exchanger of the second sublimation tank 15B to the second cooling pipe L36, and the second cooling pipe L36 is connected to the second refrigerant storage tank 19B. In this way, the first refrigerant storage tank 19A and the second refrigerant storage tank 19B can be selectively connected to the first refrigerant storage tank 19A and the second refrigerant storage tank 19B using the seventh valve V7 and the eighth valve V8, and can be cooled using refrigerant.

[0027] In the liquefaction and recovery unit 30 with the above configuration, a no-heating cycle will be performed as described below. Figure 2 shows an overview of the no-heating cycle for the first sublimation tank. Based on this figure, we will first explain the no-heating cycle for the first sublimation tank 15A.

[0028] In the solidification step p11, the seventh valve V7 is opened, the eighth valve V8 is closed, and refrigerant is supplied from the first refrigerant storage tank 19A to the first sublimation tank 15A for preliminary cooling. From the first refrigerant storage tank 19A, it is connected to a heat exchange part (not shown) provided inside the first sublimation tank 15A via the first refrigerant pipe L31 and the first refrigerant branch pipe L32, and the inside is flowed with LNG (-162 °C) or the like serving as the refrigerant to cool the first sublimation tank 15A. Then, by opening the first valve V1, the carbon dioxide gas obtained from the separation and recovery unit 20 is introduced into the first sublimation tank 15A.

[0029] At this time, the second valve V2 is in the closed state. The temperature inside the first sublimation tank 15A is cooled to below the triple point TP to solidify (dry ice form) carbon dioxide. At this time, the internal pressure of the first sublimation tank 15A rises with the generation of dry ice. At this stage, the internal temperature of the first sublimation tank 15A also rises. This process is continued until the solidification of carbon dioxide ends.

[0030] Next, in the pressure increase step p12, after the pressure equalization process described later, the third valve V3 is opened and the fourth valve V4 is closed, and liquefied carbon dioxide (or gaseous carbon dioxide) is introduced from the carbon dioxide storage tank 16 through the fifth transport pipe L21 and the fifth branch pipe L22. Then, when the first sublimation tank 15A is filled with the introduced liquefied carbon dioxide, the dry ice (temperature T < TP) inside the first sublimation tank 15A touches the liquid phase (-20 °C), and the temperature rises and proceeds to the liquid phase. That is, the latent heat when the liquefied carbon dioxide is cooled to the dry ice temperature is used to dissolve the dry ice.

[0031] In the next step, liquid extraction step p13, the liquefied carbon dioxide in the first sublimation tank 15A is discharged from the tank. Specifically, fluid F (liquefied carbon dioxide or carbon dioxide gas) is flowed from the first sublimation tank 15A through the third branch pipe L16 and the second transport pipe L18 to the dewarmer 17. At this time, the temperature of the fluid F passing through the third branch pipe L16 and the second transport pipe L18 is lower than the temperature of the liquefied carbon dioxide present in the carbon dioxide storage tank 16, so it is heated in the dewarmer 17. Then, the liquefied carbon dioxide is stored in the carbon dioxide storage tank 16. After that, it is extracted from the carbon dioxide storage tank 16 as liquefied carbon dioxide Lc through the extraction pipe L24.

[0032] Finally, in the depressurization process p14, after the pressure equalization process described later, the refrigerant is passed through the first sublimation tank 15A again to cool the carbon dioxide inside, thereby lowering the temperature (to below -56.6°C) and the pressure (to below the triple point). Due to the decrease in temperature, the carbon dioxide inside the first sublimation tank 15A also solidifies into dry ice. In other words, it is necessary to lower the internal pressure of the first sublimation tank 15A at this stage.

[0033] As shown in Figure 2, the solidification step p11 increases the internal pressure of the first sublimation tank 15A, and the depressurization step p14 decreases the internal pressure of the first sublimation tank 15A. This process is carried out similarly in the second sublimation tank 15B. In other words, the process basically proceeds from the solidification step p11 to the depressurization step p14, and liquefied carbon dioxide Lc is stored in the carbon dioxide storage tank 16.

[0034] Specifically, in the solidification process p21, the seventh valve V7 is closed and the eighth valve V8 is open to supply refrigerant from the first refrigerant storage tank 19A to the second sublimation tank 15B for pre-cooling. The first refrigerant storage tank 19A is connected to a heat exchange section (not shown) located inside the second sublimation tank 15B via the first refrigerant piping L31 and the second refrigerant branch pipe L33, and the second sublimation tank 15B is cooled by flowing refrigerant through this section. Then, by opening the second valve V2, carbon dioxide gas obtained from the separation and recovery section 20 is introduced into the second sublimation tank 15B. At this time, the first valve V1 is kept closed. The temperature inside the second sublimation tank 15B is then cooled to below the triple point TP to solidify (turn into dry ice) the carbon dioxide.

[0035] Next, in the pressurization process p22, after the equalization process described later, the third valve V3 is closed and the fourth valve V4 is open, and liquefied carbon dioxide (or gaseous carbon dioxide) is introduced from the carbon dioxide storage tank 16 through the fifth transport pipe L21 and the sixth branch pipe L23. When the second sublimation tank 15B is filled with the introduced liquefied carbon dioxide, the dry ice is melted by heat exchange with the liquefied carbon dioxide.

[0036] In the next step, liquid extraction (p23), the liquefied carbon dioxide in the second sublimation tank 15B is recovered. Specifically, fluid F (liquefied carbon dioxide or carbon dioxide gas) is flowed from the second sublimation tank 15B through the fourth branch pipe L17 and the second transport pipe L18 to the dewarmer 17. At this time, the temperature of the fluid F passing through the fourth branch pipe L17 and the second transport pipe L18 is raised in the dewarmer 17. Then, the liquefied carbon dioxide is stored in the carbon dioxide storage tank 16. After that, it is extracted from the carbon dioxide storage tank 16 as liquefied carbon dioxide Lc through the extraction pipe L24.

[0037] Finally, in the depressurization process p24, after the pressure equalization process described later, the refrigerant is passed through the second sublimation tank 15B again to cool the carbon dioxide inside, thereby lowering the temperature (to below -56.6°C) and the pressure (to below the triple point). As both the carbon dioxide and the temperature inside the second sublimation tank 15B decrease, the carbon dioxide inside the second sublimation tank 15B solidifies into dry ice.

[0038] In this manner, the first sublimation tank 15A and the second sublimation tank 15B, which are arranged in parallel, perform sublimation of carbon dioxide, and liquefied carbon dioxide Lc is supplied from the carbon dioxide storage tank 16 to dissolve the dry ice and recover it in the carbon dioxide storage tank 16. At a predetermined timing, the liquefied carbon dioxide Lc is discharged from the outlet pipe L24.

[0039] In this process, by staggering the sublimation timings of the first sublimation tank 15A and the second sublimation tank 15B, it becomes possible to equalize the pressure by exchanging pressure between them. Figure 3 shows a conceptual diagram of the case where pressure is exchanged between sublimation tanks to equalize the pressure. In Figure 3, when the first sublimation tank 15A is at low pressure (P1, T1), the communication valve VE is opened to connect it with the second sublimation tank 15B, which is at high pressure (P2, T2), thereby equalizing the pressure between the first sublimation tank 15A and the second sublimation tank 15B. Therefore, it is necessary to adjust the timing so that the internal pressure of the first sublimation tank 15A is reduced in the depressurization process p14 and the internal pressure of the second sublimation tank 15B is increased in the solidification process p21.

[0040] Because the carbon dioxide capture device 10 of this embodiment has the above configuration, it provides the following effects and advantages.

[0041] First, it becomes possible to provide a carbon dioxide recovery device 10 that efficiently melts and recovers dry ice. This is achieved by the following configuration: The carbon dioxide recovery device 10 includes a separation and recovery unit 20 that separates carbon dioxide from a gas G1 containing carbon dioxide, and a sublimator (sublimation tank 15) equipped with a refrigerant circuit through which a refrigerant passes and which sublimes (solidifies) the carbon dioxide supplied from the separation and recovery unit 20. The device also includes a reheater 17 that heats the carbon dioxide recovered from the sublimation tank 15, a carbon dioxide storage tank 16 that stores the liquefied carbon dioxide, and a liquid transfer means that increases the pressure of the carbon dioxide recovered from the sublimation tank 15.

[0042] The sublimation tank 15 includes a first sublimation tank 15A and a second sublimation tank 15B, which are connected in parallel to the piping from the carbon dioxide storage tank 16. It is equipped with switching means (third valve V3 and fourth valve V4) for selectively switching the piping connected to the sublimation tank 15, connecting pipes LE for connecting the sublimation tanks 15 to each other, and a valve (communication valve VE) for opening and closing the connecting pipes LE. The carbon dioxide sublimated (solidified) in the sublimation tank 15 is dissolved by liquefied carbon dioxide supplied from the carbon dioxide storage tank 16.

[0043] Thus, by equipping the sublimation tank 15 with a first sublimation tank 15A and a second sublimation tank 15B, and configuring them to share pressure between them, liquefied carbon dioxide Lc can be efficiently separated from the gas G1 to be separated. Specifically, this is for the following reasons. Figure 4 shows a flowchart of the operation of the liquefaction recovery unit 30. For the sake of explanation, the flowchart in Figure 4 is explained separately for the process performed on the first sublimation tank 15A and the process performed on the second sublimation tank 15B.

[0044] In S10, the solidification process p11 of the first sublimation tank 15A is performed, in S11, the pressurization process p12 of the first sublimation tank 15A is performed, in S12, the liquid removal process p13 of the first sublimation tank 15A is performed, and in S13, the depressurization process p14 of the first sublimation tank 15A is performed. In S14, the solidification process p11 of the first sublimation tank 15A is performed again, and in S15, the pressurization process p12 of the first sublimation tank 15A is performed again.

[0045] Meanwhile, in S16, which proceeds in parallel with S12, the solidification process p21 of the second sublimation tank 15B is carried out. In S17, the pressurization process p22 of the second sublimation tank 15B is carried out, and in S18, the liquid extraction process p23 of the second sublimation tank 15B is carried out, and in S19, the depressurization process p24 of the second sublimation tank 15B is carried out. In this way, the first sublimation tank 15A and the second sublimation tank 15B are operated with staggered timings to sublimate (solidify) gaseous carbon dioxide.

[0046] First, we will explain the solidification process p11. Figure 5 shows a flowchart of the solidification process p11.

[0047] In S20, it is determined whether pre-cooling is necessary. Since pre-cooling is performed in the depressurization process p14 described later, pre-cooling here is unnecessary when the cycle is run. If pre-cooling is necessary (S20: Yes), proceed to S21. If pre-cooling is not necessary (S20: No), proceed to S24. In S21, the seventh valve V7 is opened. Refrigerant is introduced from the first refrigerant storage tank 19A through the first refrigerant piping L31 to a heat exchanger (not shown) located inside the first sublimation tank 15A. Then, in S22, the refrigerant supply process is performed. In this way, the refrigerant and the carbon dioxide in the first sublimation tank 15A exchange heat, causing the temperature T1 to decrease and the gaseous carbon dioxide to begin sublimation (solidification). As a result, the pressure in the first sublimation tank 15A is reduced and the pressure P1 (internal pressure of the first sublimation tank 15A) decreases.

[0048] In S23, it is determined whether pre-cooling is complete. Whether pre-cooling is complete is determined by checking the value of the pressure P1, and it is determined whether the pressure has been reduced to below the pressure required to achieve the target carbon dioxide recovery rate of the separation and recovery unit 20. If the condition for completion of pre-cooling is met (S23: Yes), proceed to S24. Continue supplying refrigerant until the condition is met (S23: No). The condition for completion of pre-cooling may also be determined by the refrigerant supply time or by using the temperature T1 of the first sublimation tank 15A.

[0049] In S24, the first valve V1 is opened. At this stage, the pressure P1 in the first sublimation tank 15A is reduced, so the carbon dioxide supplied from the separation and recovery unit 20 via the first transport pipe L13 and the first branch pipe L14 is drawn into the first sublimation tank 15A, and the gaseous carbon dioxide is sublimated (solidified) sequentially. Then, in S25, the sublimation process (solidification process) is carried out.

[0050] In S26, it is determined whether solidification is complete. Since solidification in the first sublimation tank 15A basically takes place around the capillary tubes that perform heat exchange, the efficiency of heat exchange deteriorates when the solidified dry ice covers the capillary tubes. For this reason, the process is terminated when a predetermined amount has solidified. The termination condition for carbon dioxide solidification is assumed to be determined by the carbon dioxide supply time, but it may also be determined using other methods such as fluctuations in the pressure P1 value in the first sublimation tank 15A or the temperature T1.

[0051] In S27, the first valve V1 and the seventh valve V7 are closed. Once the solidification of carbon dioxide is complete, the first valve V1, which stops the supply of carbon dioxide from the separation and recovery unit 20, is closed, and the seventh valve V7, which stops the supply of refrigerant from the first refrigerant storage tank 19A, is closed, and the process moves to the next step. At this stage, the conditions in the first sublimation tank 15A are such that gaseous carbon dioxide solidifies, so the pressure P1 is 0.518 MPaA or less and the temperature T1 is -56.6°C or less.

[0052] Figure 6 shows the flowchart for the pressurization process p12. In S30, the communication valve VE is opened. At this time, if it is the pressurization process p12 in S15, the second sublimation tank 15B has entered the depressurization process p24, and therefore the second sublimation tank 15B is in a high temperature and high pressure state. Therefore, opening the communication valve VE results in carbon dioxide flowing from the second sublimation tank 15B to the first sublimation tank 15A.

[0053] In S31, a pressure equalization process is performed, and in S32, it is maintained until P1 = P2. When the pressure P1 on the first sublimation tank 15A side becomes the same as the pressure P2 on the second sublimation tank 15B side (S32: Yes), the process moves to the next step. Then, in S33, the communication valve VE is closed. After confirming that the pressure P1 on the first sublimation tank 15A side has risen and the pressure P2 on the second sublimation tank 15B side has decreased and the pressures have been equalized, the communication valve VE is closed.

[0054] In S34, the third valve V3 is opened. Opening the third valve V3 supplies liquefied carbon dioxide stored in the carbon dioxide storage tank 16 into the first sublimation tank 15A (pressurization step p12 in Figure 2). Then, direct heating treatment is performed in S35, and in S36, P1 is maintained at 0.518 MPaA or higher. Once the pressure P1 reaches 0.518 MPaA or higher (S35: Yes), the third valve V3 is closed in S37, and the process is terminated.

[0055] Figure 7 shows the flowchart of the liquid extraction process p13. At S40, the fifth valve V5 is opened. The fifth valve V5 is a valve that connects and disconnects the third branch pipe L16, which connects the first sublimation tank 15A to the defroster 17. By opening the fifth valve V5, liquefied carbon dioxide is transported from the first sublimation tank 15A through the third branch pipe L16 and the second transport pipe L18 to the defroster 17. The defroster 17 exchanges heat with the liquefied carbon dioxide to raise its temperature.

[0056] In S41, the discharge process is performed. The second pump Pu2 is used to send liquefied carbon dioxide (including vaporized carbon dioxide) from the first sublimation tank 15A through the defroster 17 to the carbon dioxide storage tank 16. The second pump Pu2 is located between the third transport pipe L19 and the fourth transport pipe L20, and the pressure P3 of the liquefied carbon dioxide stored in the carbon dioxide storage tank 16 can be adjusted using the first pump Pu1 and the second pump Pu2. In other words, the temperature T3 of the liquefied carbon dioxide stored in the carbon dioxide storage tank 16 is adjusted by the defroster 17, and the pressure P3 is adjusted by the first pump Pu1 and the second pump Pu2.

[0057] In S42, check if the dispensing is complete, and maintain the dispensing process until dispensing is complete (S42:Yes) or (S42:No). Completion of dispensing can be determined by checking the liquid level in the first sublimation tank 15A or by referring to the pressure P1, etc. Then, in S43, close the fifth valve V5 to terminate the process.

[0058] Figure 8 shows the flowchart of the depressurization process p14. At S50, the communication valve VE is opened. At S51, the pressure equalization process is performed. When the communication valve VE is opened, the first sublimation tank 15A and the second sublimation tank 15B are connected through the connecting pipe LE. At this time, the first sublimation tank 15A is pressurized and is in a high temperature and high pressure state, while the second sublimation tank 15B is in a low temperature and low pressure state (the process of the pressurization process p22 is being performed). Therefore, carbon dioxide flows from the first sublimation tank 15A to the second sublimation tank 15B, and the pressure P1 in the first sublimation tank 15A and the pressure P2 in the second sublimation tank 15B become equal.

[0059] In S52, a check is performed to see if P1 = P2. The pressure equalization process is maintained until pressures P1 and P2 become equal (S52: Yes) (S52: No). Once the pressure equalization process is complete, the communication valve VE is closed in S53.

[0060] In S54, the seventh valve V7 is opened. Refrigerant is introduced from the first refrigerant storage tank 19A through the first refrigerant piping L31 to a heat exchanger (not shown) located inside the first sublimation tank 15A. Then, in S55, the refrigerant supply process is performed. If the pressure P1 in the first sublimation tank 15A does not reach the target pressure due to the pressure equalization process, the refrigerant supply process is performed again to pre-cool the first sublimation tank 15A.

[0061] In S56, it is determined whether pre-cooling is complete. This is done by checking the pressure P1 value, and it is determined whether the pressure has been reduced to below the pressure required to achieve the target carbon dioxide recovery rate of the separation and recovery unit 20. If the condition for pre-cooling completion is met (S56: Yes), the process is terminated. If the condition is not met (S56: No), the refrigerant supply continues. The pre-cooling completion condition may be determined by the refrigerant supply time or by using the temperature T1 of the first sublimation tank 15A. Although not shown in the flowchart, the same process is performed on the second sublimation tank 15B. The first sublimation tank 15A and the second sublimation tank 15B are processed in parallel as shown in Figure 4 to produce liquefied carbon dioxide.

[0062] Figure 9 shows a comparison of the volume of heat transfer medium required in the depressurization process p14. Figure 10 shows a comparison of the volume of heat transfer medium required in the boosting process p12. Here, V1 represents the volume of heat transfer medium originally required, and V2 represents the volume of heat transfer medium required when the present invention is implemented. In addition, the heat transfer medium (refrigerant) used in the depressurization process p14 shown in Figure 9 is LNG, and the heat transfer medium used in the boosting process p12 shown in Figure 10 is liquefied carbon dioxide. Considering the model with maximum efficiency, in a large-scale carbon dioxide recovery device 10, the estimated difference in the volume of heat transfer medium required in the depressurization process p14 is 0.00005 times, and the difference in the volume of heat transfer medium required in the boosting process p12 is 0.9 times. In other words, it is possible to significantly reduce the amount of heat transfer medium required in the depressurization process p14, and it is possible to reduce the amount of heat transfer medium required in the boosting process p12 by 10%.

[0063] In this way, by sharing the pressure between the first sublimation tank 15A and the second sublimation tank 15B, it is possible to reduce the amount of heat transfer medium required, thereby reducing the operating costs of the carbon dioxide recovery device 10. The most significant effect is the reduction in the refrigerant used in the depressurization process p14, which reduces the consumption of refrigerant (LNG) that needs to be supplied from an external source, and thus is expected to reduce overall costs. In addition, although the heat transfer medium used in the pressurization process p12 is liquefied carbon dioxide, it is undesirable for the amount of liquefied carbon dioxide Lc extracted as a product to decrease, so it is desirable to reduce consumption as much as possible.

[0064] In this way, by combining the first sublimation tank 15A and the second sublimation tank 15B and switching between them in a batch operation, the amount of refrigerant used can be significantly reduced compared to performing the depressurization process p14 using only refrigerant, and the residual pressure in either the first sublimation tank 15A or the second sublimation tank 15B can be effectively utilized.

[0065] (Second Embodiment) The second embodiment has the same device configuration as the carbon dioxide recovery device 10 of the first embodiment, but differs in that it uses a second carbon dioxide storage tank 31 in addition to the carbon dioxide storage tank 16. Figure 11 shows a conceptual diagram of the case in the second embodiment where pressure is transferred from the second carbon dioxide storage tank 31 to equalize the pressure. Note that the lines for the dewarmer 17, carbon dioxide storage tank 16, first refrigerant storage tank 19A, and second refrigerant storage tank 19B are omitted in Figure 11 as they are not explained therein.

[0066] The second carbon dioxide storage tank 31 is connected to the first sublimation tank 15A by the sixth transport pipe L41 and the fifth branch pipe L42, and is connected and disconnected by the ninth valve V9. Similarly, the second sublimation tank 15B is connected to the sixth transport pipe L41 and the sixth branch pipe L43, and is connected and disconnected by the tenth valve V10. Therefore, the ninth valve V9 and the tenth valve V10 allow the second carbon dioxide storage tank 31 to be selectively connected to the first sublimation tank 15A and the second sublimation tank 15B.

[0067] Pressure equalization is achieved by connecting the first sublimation tank 15A with a carbon dioxide storage tank 31 (pressure P4 ≥ 0.518 MPa, temperature T4 ≥ -56.6°C) that has a pressure P4 and temperature T4 above the triple point. Examples of the second carbon dioxide storage tank 31 include vaporized carbon dioxide storage tanks such as gas holders, and liquefied carbon dioxide storage tanks such as tanks and containers. In this case, if the pressure P4 of the second carbon dioxide storage tank 31 is higher than the pressure P2 of the second sublimation tank 15B as shown in the first embodiment, the pressure difference with the pressure P1 of the first sublimation tank 15A will be larger, so by adjusting the amount of carbon dioxide in the second carbon dioxide storage tank 31, it becomes possible to further reduce the amount of heat transfer medium required for the pressurization process p12 of the first sublimation tank 15A.

[0068] Although the explanation described equalizing the pressure in the first sublimation tank 15A and the second carbon dioxide storage tank 31, this does not prevent equalizing the pressure with the second sublimation tank 15B before or after this. For example, after equalizing the pressure in the first sublimation tank 15A and the second carbon dioxide storage tank 31, the pressure P1 in the first sublimation tank 15A becomes equal to the pressure P4 in the second carbon dioxide storage tank 31, and this does not prevent equalizing the pressure P1 in the first sublimation tank 15A and the pressure P2 in the second sublimation tank 15B.

[0069] (Third embodiment) The third embodiment is almost the same as the configuration of the first embodiment, but differs in that a third sublimation tank 15C is provided in parallel with the first sublimation tank 15A and the second sublimation tank 15B. Figure 12 shows a schematic diagram of the configuration of the carbon dioxide recovery device 10 of the third embodiment. Note that in Figure 12, the third sublimation tank 15C is connected to the carbon dioxide storage tank 16 and the first refrigerant storage tank 19A and the second refrigerant storage tank 19B, similar to the first sublimation tank 15A and the second sublimation tank 15B, but this is omitted here.

[0070] The third sublimation tank 15C is operated in the same manner as the first sublimation tank 15A and the second sublimation tank 15B. That is, just as the first sublimation tank 15A performs the solidification process p11, the pressurization process p12, the liquid extraction process p13, and the depressurization process p14 in sequence, the third sublimation tank 15C sublimes carbon dioxide in the same procedure, but with a staggered timing. Since the third sublimation tank 15C is connected to the first sublimation tank 15A and the second sublimation tank 15B by connecting pipes LE2 and LE3, respectively, it can contribute to increasing the operational efficiency of the carbon dioxide recovery device 10 by exchanging pressure at the appropriate timing.

[0071] Although embodiments of the carbon dioxide recovery device 10 according to the present invention have been described above, the present invention is not limited thereto, and various modifications are possible without departing from its spirit. For example, in the first embodiment, the first sublimation tank 15A and the second sublimation tank 15B are combined, and in the third embodiment, the first sublimation tank 15A and the third sublimation tank 15C are combined, but there is no prerequisite for further increasing the number of sublimation tanks and combining them for operation. Also, as shown in the second embodiment, there is no prerequisite for increasing the number of carbon dioxide storage tanks 16 or the second carbon dioxide storage tank 31 for pressure exchange. [Explanation of Symbols]

[0072] G1 Gas to be separated 10. Carbon dioxide capture device 15 Sublimation tank 15A 1st sublimation tank 15B 2nd sublimation tank 16. Carbon dioxide storage tank 17 Reheater VE communication valve V1 First Valve V2 2nd valve

Claims

1. A carbon dioxide recovery apparatus comprising a separation device for separating carbon dioxide from a gas containing carbon dioxide, and a sublimator equipped with a refrigerant circuit through which a refrigerant passes and for sublimating (solidifying) the carbon dioxide supplied from the separation device, A dewarmer for heating the carbon dioxide recovered from the sublimator, A carbon dioxide storage tank for storing the liquefied carbon dioxide, The system includes a liquid transfer means for increasing the pressure of the carbon dioxide recovered from the sublimator, The sublimation apparatus includes a first sublimation apparatus and a second sublimation apparatus, which are installed connected in parallel to the piping from the carbon dioxide storage tank. The system includes a switching means for selectively switching the piping connected to the sublimator, connecting piping for connecting the sublimators to each other, and a valve for opening and closing the piping. The carbon dioxide that has been sublimated (solidified) in the sublimator is dissolved by the liquefied carbon dioxide supplied from the liquefied carbon dioxide storage tank. A carbon dioxide capture device characterized by the following.

2. In the carbon dioxide recovery apparatus according to claim 1, The sublimator includes a third sublimator, The aforementioned connecting pipe is A first connecting pipe connecting the first sublimator and the second sublimator, A second connecting pipe connecting the second sublimator and the third sublimator, The system includes a third connecting pipe connecting the third sublimator and the first sublimator, The aforementioned valve is A first valve provided in the first connecting pipe, A second valve provided in the second connecting pipe, The third valve provided in the third connecting pipe is included, A carbon dioxide capture device characterized by the following.

3. In the carbon dioxide recovery apparatus according to claim 1, The separation device is connected to the first sublimator and the second sublimator, The first sublimator and the second sublimator are connected to the dewarmer. The reheater is connected to the carbon dioxide storage tank via the liquid supply means, The carbon dioxide storage tank is connected to the first sublimator and the second sublimator, The carbon dioxide storage tank is equipped with an outlet for extracting liquefied carbon dioxide as a product. A carbon dioxide capture device characterized by the following.

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