Carbon dioxide capture device

Abstract

To provide a carbon dioxide recovery system that minimizes energy consumption for melting and vaporizing dry ice, as well as heat loss from the container. [Solution] A carbon dioxide recovery device 10 is provided with a separation and recovery unit 20 for separating carbon dioxide from a gas G1 containing carbon dioxide. The separation and recovery unit 20 supplied with the gas G1 is connected in series from the upstream side to which the gas G1 is supplied, a sublimator 15 equipped with a refrigerant circuit through which a refrigerant is passed to sublimate the carbon dioxide, a dewarmer 17 for heating the carbon dioxide recovered from the sublimator 15, and a carbon dioxide storage tank 16 for storing the liquefied carbon dioxide. The device is further equipped with a fifth transport pipe L25 for sending liquefied carbon dioxide from the carbon dioxide storage tank 16 to the sublimator 15, and a first pump Pu3 for increasing the pressure of the carbon dioxide recovered from the sublimator 15. The sublimated carbon dioxide is dissolved by liquefied carbon dioxide supplied from the carbon dioxide storage tank 16 to the sublimator 15 through the fifth transport pipe L25.

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, attempts have been made internationally to reduce the amount of carbon dioxide emitted into the atmosphere in order to solve the climate change problem, and a decrease in the consumption of fossil fuels is predicted through electrification and the like. On the other hand, the demand for dry ice used in beverage applications and logistics remains, and it has become difficult to supply high-concentration carbon dioxide gas as a raw material. For this reason, there is a need 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, a separation device and a carbon dioxide sublimator for sublimating the carbon dioxide separated in the separation device are connected in series in order from the upstream where the separated gas is supplied, a refrigerant circuit using a fluid having cold heat as a refrigerant is connected to the carbon dioxide sublimator, sublimation of carbon dioxide is performed by the refrigerant, and 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.

[0004] ​​[Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2021 / 221007 [Patent Document 2] Japanese Patent Publication No. 2007-69059 [Overview of the project] [Problems that the invention aims to solve]

[0006] 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), possible methods include flowing a high-temperature heat transfer medium through a carbon dioxide sublimator instead of a refrigerant to exchange heat with the dry ice, or heating it using a heater or the like. Patent Document 1 lists natural gas and its main components, such as methane, nitrogen, oxygen, and hydrogen, as candidates for the heat transfer medium to be used for heating.

[0007] When the refrigerant and heat transfer medium have different components, mixing of their components can alter the properties of each heat transfer medium. To prevent this, natural gas or methane, which have the same components as the refrigerant and heat transfer medium, are considered appropriate. However, since both of these media vaporize at room temperature, they have the drawback of supplying less heat per unit time compared to liquefied natural gas. In addition, there is the problem of heat loss equivalent to the heat capacity of the heat transfer tubes and piping of the heat exchanger occurring each time the refrigerant and heat transfer medium are switched.

[0008] On the other hand, while placing heaters inside the carbon dioxide sublimator can increase the amount of heat that can be supplied per unit time, it results in heat loss equivalent to the heat capacity of the heater itself, and uniform heating is difficult unless many heaters are properly arranged inside the carbon dioxide sublimator. Furthermore, repairs are difficult when a wire breaks.

[0009] To minimize heat loss during the melting of dry ice, Patent Document 2 proposes a direct heating method using liquefied carbon dioxide. However, Patent Document 2 requires a pressure application method using a pressurizing pump before introducing liquefied carbon dioxide. In addition, when using a medium-temperature, medium-pressure (-26°C, 1.8 MPa) carbon dioxide storage tank used for transporting liquefied carbon dioxide, heat loss due to the dry ice recovery container becomes large, and the thickness of the steel material must be increased to withstand pressure, resulting in cost problems.

[0010] Therefore, the present invention aims to provide a carbon dioxide recovery device that reduces energy consumption for melting and vaporizing dry ice and heat loss in the container in order to solve these problems. [Means for solving the problem]

[0011] To achieve the above objective, a carbon dioxide recovery device according to one aspect of the present invention has the following features.

[0012] (1) A carbon dioxide recovery apparatus equipped with a separation device for separating carbon dioxide from a gas containing carbon dioxide, The separation device to which the gas to be separated is supplied, A sublimator equipped with a refrigerant circuit through which a refrigerant passes and which sublimes (solidifies) the carbon dioxide, A dewarmer for heating the carbon dioxide recovered from the sublimator, A liquefied 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 carbon dioxide that has been sublimated (solidified) in the sublimator is dissolved by the carbon dioxide supplied from the liquefied carbon dioxide storage tank in liquid or gaseous form. It is characterized by the following.

[0013] (2) In the carbon dioxide recovery device described in (1), The separation device, the sublimator, the dewarmer, and the liquefied carbon dioxide storage tank are connected in series, starting from the upstream side to which the gas to be separated is supplied. The system includes a pipeline for supplying liquefied carbon dioxide from the liquefied carbon dioxide storage tank to the sublimator, Dissolving the sublimated (solidified) carbon dioxide with the liquid or gaseous carbon dioxide supplied from the liquefied carbon dioxide storage tank to the sublimator through the piping, It is preferable.

[0014] In the manner described in (1) and (2) above, carbon dioxide that has sublimated (solidified) into dry ice in the sublimator is dissolved by solid-liquid contact with liquefied carbon dioxide, and the liquefied carbon dioxide is discharged from the sublimator. By introducing liquefied carbon dioxide into the sublimator, it becomes unnecessary to install a heating mechanism inside the sublimator, thus simplifying the structure of the sublimator and improving maintainability. Furthermore, it leads to the efficient vaporization, dissolution, and recovery of dry ice by bringing a liquid, which has a significantly higher density than a gas, into contact with a solid, while suppressing heat loss and energy consumption required for vaporization and dissolution of dry ice. Additionally, by bringing gaseous carbon dioxide into gas-solid contact with dry ice, it is expected that heat loss and energy consumption will be similarly suppressed even when vaporizing and dissolving the dry ice.

[0015] (3) In the carbon dioxide recovery device described in (1), The separation device, the sublimator, the liquefied carbon dioxide storage tank, and the dewarmer are connected in series, starting from the upstream side to which the gas to be separated is supplied. The system includes a piping route for sending liquefied carbon dioxide from the dewarmer to the sublimator, Dissolving the sublimated (solidified) carbon dioxide with the liquid or gaseous carbon dioxide supplied from the dewarmer to the sublimator through the piping, It is preferable.

[0016] The embodiment described in (3) above can simplify the structure of the component devices of the apparatus and the configuration compared to the embodiment described in (2). Therefore, while suppressing heat loss and energy consumption for vaporizing and melting dry ice, it is possible to efficiently vaporize and melt dry ice for recovery and reduce the construction cost of the carbon dioxide recovery apparatus. Also, by bringing gaseous carbon dioxide into gas-solid contact with dry ice, it is expected to have the effect of suppressing heat loss and energy consumption even when dry ice is vaporized and melted.

[0017] (4) In the carbon dioxide recovery apparatus described in (2), connect a second liquefied carbon dioxide storage tank between the sublimator and the reheater, and store liquefied carbon dioxide at a lower temperature and lower pressure than the liquefied carbon dioxide storage tank in the second liquefied carbon dioxide storage tank, which is preferable.

[0018] According to the embodiment described in (4) above, since it includes a liquefied carbon dioxide storage tank and a second carbon dioxide storage tank and stores liquefied carbon dioxide at a lower temperature and lower pressure, it becomes possible to obtain liquefied carbon dioxide at different temperatures and pressures from one carbon dioxide recovery apparatus.

Brief Description of the Drawings

[0019] [Figure 1] It is a schematic diagram showing the configuration of the carbon dioxide recovery apparatus of the first embodiment. [Figure 2] It is a p-h diagram representing the cycle of the first embodiment. [Figure 3] It shows a comparison of the cycle of the first embodiment with the prior art. [Figure 4] It is a conceptual diagram explaining the changes in temperature and pressure of the first embodiment. [Figure 5] It is a p-h diagram representing the cycle of the second embodiment. [Figure 6] It shows a comparison of the cycle of the second embodiment with the prior art. [Figure 7] It is a schematic diagram showing the configuration of the carbon dioxide recovery apparatus of the fifth embodiment. [Figure 8] This is a schematic diagram showing the configuration of the carbon dioxide capture device according to the seventh embodiment. [Modes for carrying out the invention]

[0020] (First Embodiment) First, a first embodiment of the present invention will be described with reference to the drawings. Figure 1 schematically shows the configuration of the carbon dioxide recovery device 10 of the first embodiment. The carbon dioxide recovery device 10 includes an absorption tower 12 and a regeneration tower 13 as a separation and recovery unit 20, and a sublimator 15, a dewarmer 17, and a carbon dioxide storage tank 16 as a liquefaction and recovery unit 30. The configuration is such that carbon dioxide is extracted in the separation and recovery unit 20 and the liquefied carbon dioxide is recovered in the liquefaction and recovery unit 30.

[0021] In the absorption tower 12, carbon dioxide contained in the gas is adsorbed into the absorbent liquid La. In the regeneration tower 13, carbon dioxide is separated from the absorbent liquid La to regenerate it. In the sublimator 15, the recovered carbon dioxide (liquid or gaseous) is cooled to produce dry ice. In the carbon dioxide storage tank 16, liquefied carbon dioxide Lc is extracted. In the dewarmer 17, the liquefied carbon dioxide is heated using a heat exchanger.

[0022] Next, we will explain the separation and recovery unit 20 provided in the carbon dioxide recovery device 10. A gas inlet 22 is provided at the bottom of the absorption tower 12 and is connected to the gas supply line L11. From here, the gas to be separated G1 is taken into the carbon dioxide recovery device 10. Combustion exhaust gas (gas to be separated G1) generated at power plants, steel mills, cement mills, etc., is supplied from the gas supply line L11. Combustion exhaust gas contains less than 20% carbon dioxide, and also contains nitrogen, oxygen, water vapor, etc. In some cases, the combustion exhaust gas may contain sulfur oxides, so a desulfurization device may be installed in the middle of the gas supply line L11.

[0023] The gas to be separated G1 can include not only combustion exhaust gas, but also air, biogas, or off-gas containing carbon dioxide generated from heat treatment passages such as carburizing furnaces or chemical equipment. As the absorbent liquid La, amine-based aqueous solutions or physical absorbents can be used. This does not preclude the use of substances with comparable performance.

[0024] At the top of the absorption tower 12, one end of an exhaust pipe L12 is connected to a gas outlet 25 for discharging treated gas G2, from which carbon dioxide has been removed. Treated gas G2 is the gas remaining after carbon dioxide has been removed by the absorbent liquid La, which will be described later, and consists of nitrogen and oxygen.

[0025] The absorbent liquid La absorbs carbon dioxide from the gas G1 supplied to the absorption tower 12 by passing (falling) between the absorbent liquid inlet 23 located at the top of the absorption tower 12 and the absorbent liquid outlet 24 located at the bottom of the absorption tower 12. A packing material R, such as a Laschig ring, is packed between the absorbent liquid inlet 23 and the absorbent liquid outlet 24. The Laschig ring is a packing material made of borosilicate glass with excellent chemical resistance, possessing superior corrosion and chemical resistance to acids and organic solvents. However, the material of the Laschig ring is not limited to glass; metal or porcelain materials can also be used.

[0026] One end of the first outlet pipe L13 is connected to the absorbent liquid inlet 23, and one end of the second outlet pipe L14 is connected to the absorbent liquid outlet 24. A circulation pump Pu1 is also provided in the first outlet pipe L13.

[0027] The other end of the second outlet pipe L14 is connected to the absorbent liquid inlet 32 ​​located at the top of the regeneration tower 13, and the other end of the first outlet pipe L13 is connected to the absorbent liquid outlet 33 located at the bottom of the regeneration tower 13. Due to the pressure difference between the absorption tower 12 and the regeneration tower 13, the absorbent liquid is naturally transferred to the regeneration tower 13, but a circulation pump may be installed in the first outlet pipe L13 if necessary. A packing material R, such as a Raschig ring, is packed between the absorbent liquid inlet 32 ​​and the absorbent liquid outlet 33. In addition, one end of the separation and recovery pipe L15 is connected to the carbon dioxide outlet 34 located at the top of the regeneration tower 13. Carbon dioxide is discharged from the regeneration tower 13 into the separation and recovery pipe L15.

[0028] Therefore, considering the movement of the absorbent liquid La, the absorbent liquid La2 (rich liquid) that has absorbed carbon dioxide flowing out of the absorption tower 12 is sent to the regeneration tower 13, and the absorbent liquid La1 (lean liquid) with a low carbon dioxide content that flows out of the regeneration tower 13 is sent to the absorption tower 12. In other words, the absorption tower 12 and the regeneration tower 13 are connected by the first outlet pipe L13 and the second outlet pipe L14, and the absorbent liquid La is circulated to recover carbon dioxide.

[0029] The gas to be separated G1, introduced into the absorption tower 12 from the gas inlet 22, rises within the absorption tower 12, while the absorbent liquid (lean liquid) La1 supplied to the absorption tower 12 from the absorbent liquid inlet 23 falls toward the packing material R. Therefore, the gas to be separated G1 rising within the absorption tower 12 from the gas inlet 22 comes into gas-liquid contact with the absorbent liquid (lean liquid) La1 falling within the absorption tower 12 from the absorbent liquid inlet 23, thereby absorbing carbon dioxide. The absorbent liquid (lean liquid) La1, containing carbon dioxide, becomes the absorbent liquid (rich liquid) La2. The absorbent liquid (rich liquid) La2 is discharged to the regeneration tower 13 from the absorbent liquid outlet 24. The treated gas G2, from which carbon dioxide has been removed, is discharged from the gas outlet 25.

[0030] The absorbent liquid (rich liquid) La2 introduced into the regeneration tower 13 from the absorbent liquid inlet 32 ​​is depressurized within the regeneration tower 13, releasing carbon dioxide along with water vapor. The depressurization of the absorbent liquid (rich liquid) La2 is achieved by connecting the regeneration tower 13 and the sublimator 15. Dry ice is generated by the cooling of the sublimator 15, and consequently, the pressure in the regeneration tower 13 and the sublimator 15 is reduced to the sublimation pressure of the dry ice. After releasing carbon dioxide, the absorbent liquid (lean liquid) La1 is discharged from the absorbent liquid outlet 33 of the regeneration tower 13. In other words, the absorbent liquid La circulates between the absorption tower 12 and the regeneration tower 13. Meanwhile, carbon dioxide is discharged from the carbon dioxide outlet 34.

[0031] The other end of the separation and recovery pipe L15, which is connected to the carbon dioxide outlet 34 of the regeneration tower 13, is connected to the gas inlet 42 of the gas-liquid separator 14. In the gas-liquid separator 14, volatile absorbent liquid and water vapor contained in the carbon dioxide released in the regeneration tower 13 are liquefied and separated from the carbon dioxide. Although not shown in the diagram, the liquefied impurities (volatile absorbent liquid and water vapor) are discharged through the drain. Then, the vaporized carbon dioxide is transferred to the sublimator 15 via the first transport pipe L21, one end of which is connected to the outlet 43. In the separation and recovery section 20, the process of extracting carbon dioxide follows the flow described above.

[0032] Regarding the separation of carbon dioxide, while the gas to be separated G1 was separated using the absorbent liquid La, there is no prejudice to applying 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.

[0033] Next, the liquefaction and recovery unit 30 will be described. An inlet 51 is provided at the top of the sublimator 15, to which the other end of the first transport pipe L21 is connected. A circulation inlet 52 and a circulation outlet 53 are provided at the bottom, with one end of the fifth transport pipe L25 connected to the circulation inlet 52 and the other end of the second transport pipe L22 connected to the circulation outlet 53. One end of the discharge pipe L31 is connected to an exhaust port 54 at the top of the sublimator 15. A blower Pu2 (or vacuum pump) is provided in the discharge pipe L31 to extract gaseous carbon dioxide G3.

[0034] The second transport pipe L22 is connected to the first pump Pu3 (or compressor), and one end of the third transport pipe L23 is connected from the first pump Pu3 to the dewarmer 17. Since the second transport pipe L22 and the third transport pipe L23 need to transport liquid carbon dioxide, the first pump Pu3 needs to have the capacity to transport liquid. One end of the fourth transport pipe L24 is connected to the dewarmer 17.

[0035] The other end of the fourth transport pipe L24 is connected to the liquefied carbon dioxide storage tank 16, and a second pump Pu4 is installed in the middle of the fourth transport pipe L24. The second pump Pu4 has the capacity to transport liquid carbon dioxide. One end of the fifth transport pipe L25 is connected to the carbon dioxide storage tank 16. In this way, liquefied carbon dioxide is circulated through the second transport pipe L22, the third transport pipe L23, the fourth transport pipe L24, and the fifth transport pipe L25. One end of the extraction pipe L32 is also connected to extract liquefied carbon dioxide Lc.

[0036] In the liquefaction and recovery unit 30 with the above configuration, liquefied carbon dioxide Lc is extracted by the following procedure. Figure 2 explains each step using a Ph diagram (Mollier diagram). Figure 3 shows an overview of the no-heating cycle. (a) shows the conventional cycle and (b) shows the no-heating cycle of the first embodiment.

[0037] In the sublimation process p1, gaseous carbon dioxide obtained from the separation and recovery unit 20 is introduced into the sublimator 15. At this time, the sublimator 15 is cooled using LNG (-162°C) or the like as a refrigerant, and the internal temperature is cooled to below the triple point TP to solidify (turn into dry ice) the carbon dioxide.

[0038] In the pressurization step p2, carbon dioxide is introduced from the carbon dioxide storage tank 16 through the fifth transport pipe L25 to increase the pressure inside the sublimator 15. During the introduction, liquefied or vaporized carbon dioxide first moves from the carbon dioxide storage tank 16 to the sublimator 15, and as a result, the internal pressure inside the sublimator 15 rises to pressure P1 (0.518 MPa). At this stage, the internal temperature of the sublimator 15 rises.

[0039] In the dissolution step p3, when the sublimator 15 is filled with the introduced liquefied carbon dioxide, the dry ice (temperature T < TP) in the sublimator 15 touches the liquid phase (-20 °C), causing the temperature to rise and proceed to the liquid phase. That is, the dry ice is melted by exchanging heat with the liquefied carbon dioxide. The difference from the conventional cycle is that in Fig. 3(a), the tube is heated to dissolve the dry ice, while in Fig. 3(b), by supplying liquefied carbon dioxide into the sublimator 15, the sensible heat when the liquefied carbon dioxide is cooled to the dry ice temperature is utilized to dissolve the dry ice. When introducing gaseous carbon dioxide into the sublimator 15, the heat of condensation during liquefaction can also be utilized.

[0040] In the liquid extraction step p4, the liquefied carbon dioxide in the sublimator 15 is recovered. Specifically, the fluid F (liquefied carbon dioxide or carbon dioxide in a gas-liquid two-phase state) is passed through the second transport pipe L22 and the third transport pipe L23 to the reheater 17 so that the pressure in the sublimator 15 does not fluctuate. At this time, since the pressure in the sublimator 15 is lower than the pressure in the carbon dioxide storage tank 16, it is pressurized by the first pump Pu3. Also, since the temperature of the fluid F passing through the second transport pipe L22 and the third transport pipe L23 is lower than the temperature of the liquefied carbon dioxide existing in the carbon dioxide storage layer 16, it is heated in the reheater 17. Therefore, liquefied carbon dioxide is stored in the carbon dioxide storage tank 16. Also, the liquefied carbon dioxide Lc is taken out through the extraction pipe L32 from the carbon dioxide storage tank 16.

[0041] In the depressurization step p5, the internal carbon dioxide is cooled by passing the refrigerant through the sublimator 15 again, thereby reducing the temperature (-56.6 °C or lower) and reducing the pressure (below the triple point). In the sublimator 15, the carbon dioxide solidifies due to the temperature drop and becomes dry ice.

[0042] Since the carbon dioxide recovery device 10 of this embodiment has the above configuration, it has the following effects as described below.

[0043] First, it becomes possible to provide a carbon dioxide recovery device 10 that efficiently melts and recovers dry ice. In this carbon dioxide recovery device 10, which includes a separation and recovery unit 20 that separates carbon dioxide from a gas G1 containing carbon dioxide, the separation and recovery unit 20 to which the gas G1 is supplied is connected in series from the upstream side to which the gas G1 is supplied, a sublimator 15 equipped with a refrigerant circuit through which a refrigerant passes and which sublimes (solidifies) the carbon dioxide, a dewarmer 17 that heats the carbon dioxide recovered from the sublimator 15, and a carbon dioxide storage tank 16 that stores the liquefied carbon dioxide.

[0044] The system also includes a fifth transport pipe L25 for sending liquefied carbon dioxide from the carbon dioxide storage tank 16 to the sublimator 15, and a liquid transfer means (first pump Pu3) for increasing the pressure of the carbon dioxide recovered from the sublimator 15. The sublimated (solidified) carbon dioxide is dissolved by the liquefied carbon dioxide supplied from the carbon dioxide storage tank 16 to the sublimator 15 via the fifth transport pipe L25.

[0045] Figure 4 shows a conceptual diagram illustrating the changes in temperature and pressure. Figure 4 shows a simplified configuration of the carbon dioxide recovery device 10 shown in Figure 1. As mentioned above, gaseous carbon dioxide supplied from the separation and recovery unit 20 through the first transport pipe L21 is cooled by a refrigerant in the sublimator 15. Cooling by the refrigerant sublimates (solidifies) the carbon dioxide supplied to the sublimator 15, resulting in a low temperature and low pressure state inside the sublimator 15 with a temperature T1 (-56.6°C or lower) and a pressure P1 (0.518 MPaA or lower). Once sufficiently solidified, as mentioned above, liquid or gaseous carbon dioxide is supplied from the carbon dioxide storage tank 16 to the sublimator 15 and dissolved.

[0046] The dissolved liquefied carbon dioxide is sent as fluid F to the second transport pipe L22 connected to the sublimator 15. Fluid F is in a liquid or gas-liquid two-phase state, and when it leaves the sublimator 15, it is at a pressure P3 (0.8 MPaA) and a temperature T3 (-45°C). Then, the first pump Pu3, located between the second transport pipe L22 and the third transport pipe L23, increases the pressure to P2 (2 MPaA). The dewarmer 17 then raises the temperature T3 to T2 (-20°C). Therefore, carbon dioxide is supplied to the carbon dioxide storage tank 16 at a pressure of P2 and a temperature of T2, and the required amount is stored.

[0047] In this way, a portion of the liquefied carbon dioxide is supplied to the sublimator 15 as described above to dissolve the dry ice produced in the sublimator 15, while the rest is extracted as liquefied carbon dioxide Lc as a product from the carbon dioxide storage tank 16 through the extraction pipe L32, thus efficiently dissolving the dry ice. As a result, it is possible to extract either liquefied carbon dioxide Lc or gaseous carbon dioxide G3 as a product from the sublimator 15 and the carbon dioxide storage tank 16. The carbon dioxide storage tank 16 will store liquefied carbon dioxide at a temperature T2 (-20℃) and a pressure P2 (2MPaA), making it possible to ship liquefied carbon dioxide at a medium temperature and medium pressure. In this case, vaporized carbon dioxide can also be supplied to the sublimator 15 instead of liquefied carbon dioxide to dissolve the dry ice.

[0048] Therefore, as indicated in the problem, there is no need to equip the sublimator 15 with a separate heating device. In addition, by providing a separate dewarmer 17, there is no need to equip the carbon dioxide storage tank 16 with a heater or other heating device. As a result, the construction cost of the device can be reduced, and maintenance is improved by eliminating concerns about heater wire breakage and other issues used in heating devices.

[0049] By simplifying the structure in this way, the carbon dioxide capture device 10 can be used as a large-scale device, such as one installed alongside a thermal power plant, a steel mill, or a cement factory. In such cases, the equipment can cost tens to hundreds of millions of yen, so the reduction in construction costs due to the simplification of the carbon dioxide capture device 10 is of great significance. Furthermore, if a heater is installed inside the carbon dioxide storage tank 16, for example, there is a problem that if a problem such as a broken wire occurs, it will be impossible to ship liquefied carbon dioxide. However, by installing a dewarmer 17 externally, as in the carbon dioxide storage tank 16 of the first embodiment, it is possible to ship liquefied carbon dioxide even if a problem occurs with the dewarmer 17.

[0050] Furthermore, the carbon dioxide recovery device 10 requires a small temperature difference between the temperature inside the sublimator 15 during the sublimation process p1 and the temperature inside the sublimator 15 during the dissolution process p3 and liquid extraction process p4, thus reducing heat loss in the steel material used in the sublimator 15. In other words, the cost of liquefying carbon dioxide can be reduced. For example, when using the technology shown in Patent Document 2, an application means using a pressure pump is required to make the pressure inside the dry ice recovery container (sublimator) the same as the pressure inside the carbon dioxide storage tank. In addition, there are cost-increasing factors such as the need for thicker steel materials, but the carbon dioxide recovery device 10 of the first embodiment can eliminate such cost-increasing factors.

[0051] (Second Embodiment) The second embodiment has the same device configuration as the carbon dioxide recovery device 10 of the first embodiment, but the depressurization process is different. Figure 5 shows a pH diagram representing the cycle of the second embodiment. Figure 6 shows an overview of the no-heating cycle. (a) shows the conventional cycle and (b) shows the no-heating cycle of the second embodiment. In the second embodiment, the first depressurization process p5-1 and the second depressurization process p5-2 are used as the depressurization process.

[0052] The first depressurization step p5-1 is a step of reducing the pressure inside the sublimator 15. Here, the pressure is reduced to near atmospheric pressure using a blower Pu2 or the like, but it may also be flowed towards the carbon dioxide storage tank 16. The second depressurization step p5-2 is the same as the depressurization step p5 of the first embodiment, and is a step of lowering the temperature and pressure inside the sublimator 15 using a refrigerant. By going through the first depressurization step P5-1, the pressure inside the sublimator 15 can be reduced efficiently.

[0053] (Third embodiment) The third embodiment has the same device configuration as the carbon dioxide capture device 10 of the first embodiment, but the temperature conditions are different. The temperature settings for each location shown in Figure 4 are as follows: Temperature T1 (-56.6℃ or lower) and pressure P1 (0.518MPaA or lower), Temperature T2 (10℃) and pressure P2 (4.5MPaA), and Temperature T3 (-20℃) and pressure P3 (2MPaA).

[0054] In the third embodiment, unlike the first embodiment, the temperature at the outlet of the sublimator 15 is raised to -20°C. The temperature in the carbon dioxide storage tank 16 is set to 10°C. In other words, the temperature difference between the sublimator 15 and the carbon dioxide storage tank 16 is large, and therefore the amount of heat supplied from the carbon dioxide storage tank 16 is large, making it possible to reduce the amount of liquefied carbon dioxide used to dissolve the dry ice solidified in the sublimator 15, and also shortening the liquefaction time of the dry ice. Furthermore, since the carbon dioxide storage tank 16 is at a temperature T2 (10°C) and a pressure P2 (4.5 MPaA), it is possible to extract liquefied carbon dioxide in a room temperature pressurized state as a product.

[0055] (Fourth Embodiment) The fourth embodiment has the same device configuration as the carbon dioxide capture device 10 of the first embodiment, but the temperature conditions are different. The temperature settings for each location shown in Figure 4 are as follows: Temperature T1 (-56.6℃ or lower) and pressure P1 (0.518MPaA or lower), Temperature T2 (10℃) and pressure P2 (4.5MPaA), and Temperature T3 (-45℃) and pressure P3 (0.8MPaA).

[0056] In the fourth embodiment, unlike in the third embodiment, the temperature at the outlet of the sublimator 15 is set to -45°C. On the other hand, the temperature in the carbon dioxide storage tank 16 is set to 10°C. By reducing the temperature difference between the sublimator 15 and its outlet, heat loss can be suppressed. Since the carbon dioxide storage tank 16 is at a temperature T2 (10°C) and a pressure P2 (4.5 MPaA), liquefied carbon dioxide in a room-temperature pressurized state can be extracted as a product.

[0057] (Fifth embodiment) The fifth embodiment has almost the same configuration as the carbon dioxide recovery device 10 of the first embodiment, but differs in that it is equipped with a second storage tank 18. Figure 7 shows a schematic diagram of the configuration of the carbon dioxide recovery device of the fifth embodiment. The second storage tank 18 is located at the end of the sixth transport pipe L26, which branches off from the middle of the second transport pipe L22. Although not shown, it is desirable to provide a solenoid valve or the like in the middle of the sixth transport pipe L26 so that it can be opened and closed at any time.

[0058] Furthermore, a seventh transport pipe L27 may be provided to channel carbon dioxide from the second storage tank 18 to the second transport pipe L22 in case the liquid level in the first storage tank 16 becomes insufficient. Although not shown in the figures, it is desirable that backflow prevention means, such as a backflow prevention valve, be provided between the connection points of the sixth transport pipe L26 and the second transport pipe L22, and between the seventh transport pipe L27 and the second transport pipe L22. The second storage tank 18 is equipped with an extraction pipe L33 so that liquefied carbon dioxide Lc can be extracted. In other words, the carbon dioxide storage tank 16 and the second storage tank 18 are incorporated into the configuration of the carbon dioxide recovery device 10.

[0059] With this configuration, liquefied carbon dioxide Lc can be extracted using the following procedure. First, gaseous carbon dioxide supplied from the separation and recovery unit 20 through the first transport pipe L21 is cooled by a refrigerant in the sublimator 15. Cooling by the refrigerant sublimates (solidifies) the carbon dioxide supplied to the sublimator 15, resulting in a low-temperature, low-pressure state inside the sublimator 15 with a temperature T1 (-56.6°C or lower) and a pressure P1 (0.518 MPaA or lower). Once sufficiently solidified, liquefied carbon dioxide is supplied from the carbon dioxide storage tank 16 as described above and dissolved.

[0060] The dissolved liquefied carbon dioxide is sent out as fluid F from the sublimator 15 via the second transport pipe L22. Fluid F is in a liquid state and reaches a pressure P3 (0.8 MPaA) and temperature T3 (-45°C) when it leaves the sublimator 15. From the second transport pipe L22, the liquefied carbon dioxide is taken in and stored in the second storage tank 18, which is connected via a branch. Therefore, liquefied carbon dioxide is stored in the second storage tank 18 at a pressure of P3 and a temperature of T3. Furthermore, the pressure is increased to P2 (2 MPaA) by the operation of the first pump Pu3, which is installed between the second transport pipe L22 and the third transport pipe L23.

[0061] Then, the dewarmer 17 raises the temperature T3 to temperature T2 (-20°C). Therefore, carbon dioxide is supplied to the carbon dioxide storage tank 16 at pressure P2 and temperature T2, and the required amount is stored there. As mentioned above, a portion of the liquefied carbon dioxide is supplied to the sublimator 15 to dissolve the dry ice produced in the sublimator 15, and the rest is extracted as liquefied carbon dioxide Lc as a product from the carbon dioxide storage tank 16 through the extraction pipe L32. In other words, in the fifth embodiment, it is possible to extract as a product liquefied carbon dioxide Lc at a medium temperature and medium pressure of temperature T2 (-20°C) and pressure P2 (2 MPaA) stored in the carbon dioxide storage tank 16, and low temperature and low pressure liquefied carbon dioxide Lc at a temperature T3 (-45°C) and pressure P3 (0.8 MPaA) stored in the second storage tank 18.

[0062] (Sixth Embodiment) The sixth embodiment has the same device configuration as the carbon dioxide recovery device 10 of the fifth embodiment, but the temperature conditions are different. The temperature settings for each location are as follows: Temperature T1 (-56.6℃ or lower) and pressure P1 (0.518MPaA or lower), temperature T2 (10℃) and pressure P2 (4.5MPaA), and temperature T3 (-45℃) and pressure P3 (0.8MPaA). Therefore, in the sixth embodiment, it is possible to extract as products liquefied carbon dioxide Lc at room temperature and pressurized at temperature T2 (10℃) and pressure P2 (4.5MPaA) stored in the carbon dioxide storage tank 16, and low temperature and low pressure liquefied carbon dioxide Lc at temperature T3 (-45℃) and pressure P3 (0.8MPaA) stored in the second storage tank 18.

[0063] (Seventh Embodiment) The seventh embodiment has almost the same configuration as the carbon dioxide recovery device 10 of the first embodiment, but differs in that the carbon dioxide storage tank 16 is located in a different position and the second pump Pu4 is not provided. In other words, the dewarmer 17 is directly connected to the sublimator 15. Specifically, as shown in the schematic diagram of the carbon dioxide recovery device of the seventh embodiment in Figure 8, the separation and recovery unit 20 to which the gas to be separated G1 is supplied, the sublimator (sublimator 15) equipped with a refrigerant circuit through which a refrigerant passes and which sublimates (solidifies) the carbon dioxide, and the dewarmer 17 to which the carbon dioxide recovered from the sublimator 15 are connected in series, starting from the upstream side where the gas to be separated G1 is supplied. The carbon dioxide storage tank 16 for storing the liquefied carbon dioxide is provided by branching off from the middle of the second transport pipe L22 provided between the sublimator 15 and the dewarmer 17.

[0064] Therefore, the gaseous carbon dioxide supplied from the separation and recovery unit 20 through the first transport pipe L21 is cooled by a refrigerant in the sublimator 15. Cooling by the refrigerant sublimates (solidifies) the carbon dioxide supplied to the sublimator 15, resulting in a low temperature and low pressure state inside the sublimator 15 with a temperature T1 (-56.6°C or lower) and a pressure P1 (0.518 MPaA or lower). Once sufficiently solidified, liquefied carbon dioxide sent from the carbon dioxide storage tank 16 is heated and pressurized to a medium temperature and medium pressure state of temperature T2 (-20°C) and pressure P2 (2 MPaA) to melt the dry ice in the sublimator 15.

[0065] The dissolved liquefied carbon dioxide is sent out as fluid F from the sublimator 15 through the second transport pipe L22. Fluid F is in a liquid or gas-liquid two-phase state, and when it leaves the sublimator 15, it is at a pressure P3 (0.8 MPaA) and a temperature T3 (-45°C). From the second transport pipe L22, the liquefied carbon dioxide is taken in and stored in the carbon dioxide storage tank 16, which is connected to the branched sixth transport pipe L26. Therefore, liquefied carbon dioxide is stored in the carbon dioxide storage tank 16 at a pressure P3 and a temperature T3.

[0066] Furthermore, carbon dioxide is returned from the carbon dioxide storage tank 16 to the second transport pipe L22 via the seventh transport pipe L27, and the pressure is increased to P2 (2 MPaA) by the operation of the first pump Pu3 installed between the second transport pipe L22 and the third transport pipe L23. As with the fifth embodiment, although not shown, it is desirable to provide backflow prevention means such as a backflow prevention valve between the connection portion of the sixth transport pipe L26 and the second transport pipe L22, and between the connection portion of the seventh transport pipe L27 and the second transport pipe L22.

[0067] Then, the temperature T3 is raised to temperature T2 (-20°C) in the dewarmer 17. The liquefied carbon dioxide is supplied to the sublimator 15 as described above, and is used to dissolve the dry ice produced in the sublimator 15. The rest is stored in the carbon dioxide storage tank 16, and it is possible to extract low-temperature, low-pressure liquefied carbon dioxide Lc at temperature T3 (-45°C) and pressure P3 (0.8 MPaA) as a product. Furthermore, the configuration is reduced by the absence of the second pump Pu4 compared to the first to fourth embodiments, and by the absence of the second storage tank 18 and the second pump Pu4 compared to the fifth and sixth embodiments, making it possible to reduce the construction cost of the carbon dioxide recovery device 10.

[0068] (Eighth embodiment) The eighth embodiment has the same device configuration as the carbon dioxide recovery device 10 of the seventh embodiment, but the temperature conditions are different. The temperature settings at each location are as follows: Temperature T1 (-56.6℃ or lower) and pressure P1 (0.518MPaA or lower), temperature T2 (10℃) and pressure P2 (4.5MPaA), and temperature T3 (-45℃) and pressure P3 (0.8MPaA). Therefore, in the eighth embodiment, it is possible to extract liquefied carbon dioxide Lc, which is stored in the carbon dioxide storage tank 16 at room temperature and pressure P2 (4.5MPaA), as a product.

[0069] The difference between the eighth and seventh embodiments is that the liquefied carbon dioxide, heated by the dewarmer 17 and pressurized by the operation of the first pump Pu3, is supplied to the sublimator 15 at room temperature and pressurized, which makes it possible to increase the melting efficiency of dry ice in the sublimator 15.

[0070] 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. The first to fourth embodiments, the fifth and sixth embodiments, and the seventh and eighth embodiments have the same configuration, with only the temperature and pressure settings being changed. The temperature and pressure set in these embodiments can be changed to match the state of the liquefied carbon dioxide Lc to be shipped as a product (low temperature low pressure, medium temperature medium pressure, room temperature increased pressure, or other). [Explanation of symbols]

[0071] G1 Gas to be separated 10. Carbon dioxide capture device 12 Absorption Towers 13 Regeneration Tower 15 Sublimation device 16. Carbon dioxide storage tank 17 Reheater

Claims

1. In a carbon dioxide recovery apparatus equipped with a separation device for separating carbon dioxide from a gas containing carbon dioxide, The separation device to which the gas to be separated is supplied, A sublimator equipped with a refrigerant circuit through which a refrigerant passes and which sublimes (solidifies) the carbon dioxide, A dewarmer for heating the carbon dioxide recovered from the sublimator, A liquefied 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 carbon dioxide that has been sublimated (solidified) in the sublimator is dissolved by the carbon dioxide supplied from the liquefied carbon dioxide storage tank in liquid or gaseous form. A carbon dioxide capture device characterized by the following.

2. In the carbon dioxide recovery apparatus according to claim 1, The separation device, the sublimator, the dewarmer, and the liquefied carbon dioxide storage tank are connected in series, starting from the upstream side to which the gas to be separated is supplied. The system includes a pipeline for supplying liquefied carbon dioxide from the liquefied carbon dioxide storage tank to the sublimator, Dissolving the sublimated (solidified) carbon dioxide with the liquid or gaseous carbon dioxide supplied from the liquefied carbon dioxide storage tank to the sublimator through the piping, A carbon dioxide capture device characterized by the following.

3. In the carbon dioxide recovery apparatus according to claim 1, The separation device, the sublimator, the liquefied carbon dioxide storage tank, and the dewarmer are connected in series, starting from the upstream side to which the gas to be separated is supplied. The system includes a piping route for sending liquefied carbon dioxide from the dewarmer to the sublimator, Dissolve the sublimated (solidified) carbon dioxide with the liquid or gaseous carbon dioxide supplied from the dewarmer to the sublimator through the piping. A carbon dioxide capture device characterized by the following.

4. In the carbon dioxide recovery apparatus according to claim 2, A second liquefied carbon dioxide storage tank is connected between the sublimator and the dewarmer. The second liquefied carbon dioxide storage tank stores liquefied carbon dioxide at a lower temperature and pressure than the first liquefied carbon dioxide storage tank. A carbon dioxide capture device characterized by the following.

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