Carbon dioxide separation and recovery system

Abstract

By mitigating the effects of day / night cycles and weather conditions, and stably separating and capturing carbon dioxide at a high operating rate, or by converting the separated and captured carbon dioxide into easily usable high-pressure gas or liquefied form, or storing it underground, the aim is to increase the annual amount of carbon dioxide separated and captured, the amount of high-pressure gas or liquefied carbon dioxide obtained from the separation and capture, or the amount of carbon dioxide stored underground. [Solution] A carbon dioxide separation and recovery system comprising: a heat storage unit that stores solar heat and provides heat; a carbon dioxide absorption liquid circulation and regeneration mechanism that uses the heat provided by the heat storage unit to heat an absorption liquid that has absorbed carbon dioxide contained in a gas, releasing carbon dioxide and separating and recovering it, while heating and regenerating the absorption liquid, and then absorbing carbon dioxide contained in a gas again; and a carbon dioxide gas separation and recovery function.

Description

Technical Field

[0001] The present invention relates to a carbon dioxide separation and recovery system.

Background Art

[0002] In Patent Document 1, there is provided a thermal power generation system including a boiler that burns fossil fuel, a steam turbine driven by steam generated by the boiler, a condenser that condenses the steam that has driven the steam turbine, a carbon dioxide separation and recovery device that separates and recovers carbon dioxide from the exhaust gas of the boiler, and a solar heat collector that collects solar heat to generate steam and supplies the steam to a reboiler of the carbon dioxide separation and recovery device. When the amount of steam generated by the solar heat collector decreases below the amount of steam required by the reboiler, extraction steam extracted from the steam turbine is supplied to the reboiler, and a part of the drain drained by the reboiler is recovered by the condenser. When the amount of steam generated by the solar heat collector is excessive compared to the amount of steam required by the reboiler, the excess steam is recovered by the condenser bypassing the reboiler.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Some carbon dioxide separation and recovery methods utilize solar thermal energy to reduce carbon dioxide emissions from the energy used in the process. For example, in chemical absorption methods, when heating the carbon dioxide-containing absorbent in the regeneration tower, some methods use steam generated by solar heat to heat the absorbent. In this case, heating with solar heat, which does not emit carbon dioxide, reduces the carbon dioxide emissions from the energy required to separate the carbon dioxide. However, solar heat cannot be used at night or during bad weather when sunlight is unavailable. In other words, in any carbon dioxide separation and recovery method, whether chemical absorption, physical adsorption using adsorbents, or membrane separation using carbon dioxide separation membranes, being able to stably separate and recover carbon dioxide regardless of day or night or weather conditions allows for stable operation of the equipment at a high operating rate and increases the annual amount of separation and recovery. However, if solar heat cannot be used for thermal storage, it is not possible to operate the equipment continuously at a high operating rate regardless of day or night or weather conditions, and thus the annual amount of separation and recovery cannot be increased. Furthermore, similar to carbon dioxide separation and recovery, compressing the separated and recovered carbon dioxide gas and filling it into high-pressure gas cylinders, liquefying it, or injecting the liquefied carbon dioxide underground for underground storage also consumes a great deal of energy. Therefore, being able to operate stably day and night, regardless of weather conditions, would enhance energy conservation and carbon dioxide reduction. However, if solar heat cannot be used for thermal storage, there is a challenge in being able to stably convert the separated and recovered carbon dioxide gas into high-pressure gas or liquefied carbon dioxide, or store it underground, at a high operating rate. The objective of the present invention is to increase the annual amount of carbon dioxide gas separated and recovered, the amount of separated and recovered carbon dioxide gas converted to high pressure gas, the amount of separated and recovered carbon dioxide gas liquefied, or the amount of separated and recovered carbon dioxide stored underground, by suppressing the effects of day and night and weather conditions, stably separating and recovering carbon dioxide at a high operating rate, converting the separated and recovered carbon dioxide into easily usable high-pressure gas or liquefied carbon dioxide, or storing it underground. [Means for solving the problem]

[0005] The carbon dioxide separation and recovery system to which the present invention applies comprises a heat storage unit that stores and provides solar heat, a turbine driven by the heat provided by the heat storage unit, a separation unit that separates carbon dioxide from a gas, a vacuum pump driven by the rotation of the turbine for sucking carbon dioxide gas provided on the carbon dioxide separation and recovery piping of the carbon dioxide separation membrane, and a carbon dioxide gas compressor for compressing the carbon dioxide separated through the separation membrane. Here, the vacuum pump and carbon dioxide gas compressor may be connected directly to the rotating shaft of the turbine or via a transmission. The separation unit may also consist of a separation membrane module that separates carbon dioxide from a gas, and a suction compressor that sucks carbon dioxide from the separation membrane module, compresses it, and supplies it as high-pressure carbon dioxide gas or liquefied carbon dioxide, and this suction compressor may be connected directly to the rotating shaft of the turbine or via a transmission. Furthermore, the system may be further equipped with an injection pump for injecting and storing the separated liquefied carbon dioxide into the ground, and this injection pump may also be driven by the rotating shaft of the turbine. Furthermore, the aforementioned press-in pump and the rotating shaft of the turbine may be connected via a coaxial cable or a transmission.

[0006] From another perspective, the carbon dioxide separation and recovery system to which the present invention applies comprises a heat storage unit that stores and provides solar heat, a gas compressor or vacuum pump that heats and regenerates a carbon dioxide absorbent liquid or adsorbent material using the heat provided by the heat storage unit, or is operated by the rotational driving force of a turbine driven by the heat provided by the heat storage unit, a separation membrane module that separates carbon dioxide from a gas, and a gas compressor that is driven by the rotation of the turbine to compress the gas supplied to the separation membrane module or the separated and recovered carbon dioxide, or a liquid transfer pump for liquefied carbon dioxide that liquefies and transfers the carbon dioxide. [Effects of the Invention]

[0007] According to the present invention, it is possible to stably separate and recover carbon dioxide with a high operating rate while suppressing the effects of day and night and weather, and further increase the amount of carbon dioxide gas separated and recovered annually, whether it is converted into high-pressure gas or liquefied carbon dioxide, which can then be filled into high-pressure gas cylinders or liquefied to make it suitable for transport and use, or compressed and liquefied carbon dioxide gas and injected underground for underground storage. [Brief explanation of the drawing]

[0008] [Figure 1] This diagram shows the overall configuration of the carbon dioxide separation and recovery system according to the first embodiment. [Figure 2] This diagram shows the overall configuration of a carbon dioxide separation and recovery system according to Modification 1 of the First Embodiment. [Figure 3] This diagram shows the overall configuration of a carbon dioxide separation and recovery system according to a modified example 2 of the first embodiment. [Figure 4] This figure shows the overall configuration of the carbon dioxide separation and recovery system according to the second embodiment. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described in detail below with reference to the attached drawings. [Overall configuration of the carbon dioxide separation and recovery system] Figure 1 shows the overall configuration of the carbon dioxide separation and recovery system 1 according to the first embodiment. The carbon dioxide separation and recovery system 1 recovers carbon dioxide from the atmosphere and stores it by injecting it into the ground. The carbon dioxide separation and recovery system 1 is positioned at the location where the carbon dioxide is injected into the ground.

[0010] The carbon dioxide separation and recovery system 1 according to the first embodiment comprises a solar thermal collection unit 10 and a drive unit 20. The carbon dioxide separation and recovery system 1 also comprises a separation unit 30, a liquefaction unit 40 and an injection unit 50.

[0011] The solar thermal collection unit 10 comprises a solar collector 11, a solar collector tube 12, and a heat storage unit 13. The solar collector 11 concentrates sunlight. The solar collector 11 is, for example, a mirror with a parabolic cross-section, and concentrates sunlight at the focal point of the parabola. The heat collector tube 12 receives sunlight focused by the heat collector 11 and heats the heat transfer medium flowing inside the tube. For example, synthetic oil or molten salt can be used as the heat transfer medium. The heat collector tube 12 is positioned at the focal point of the heat collector 11.

[0012] The heat storage unit 13 stores solar heat and provides heat. A heat transfer medium flows inside the heat storage unit 13. Hereinafter, in this specification, the heat transfer medium flowing inside the heat storage unit 13 will be referred to as the heat storage medium. For example, synthetic oil or molten salt can be used as the heat storage medium inside the heat storage unit 13. The heat storage unit 13 comprises a high-temperature tank 13a, a low-temperature tank 13b, a heat storage pipe 13c, and a heat exchanger 13d. The high-temperature tank 13a and the low-temperature tank 13b are containers capable of storing a heat storage medium. The heat storage tube 13c connects the high-temperature tank 13a and the low-temperature tank 13b. The direction in which the heat storage medium flows through the heat storage tube 13c is controlled by pumps provided in both the high-temperature tank 13a and the low-temperature tank 13b. The heat exchanger 13d is installed in the heat storage tube 13c between the high-temperature tank 13a and the low-temperature tank 13b. The heat collector tube 12 passes through the heat exchanger 13d. The heat exchanger 13d exchanges heat between the heat storage medium flowing in the heat storage tube 13c and the heat medium flowing in the heat collector tube 12.

[0013] The drive unit 20 includes a steam generator 21, a turbine 22, a shaft 23, a steam condenser 24, piping 25, and a circulation pump 26. The steam generator 21, the turbine 22, and the steam condenser 24 are connected by a pipe 25, and water flows inside the pipe 25. The circulation pump 26 causes the water inside the pipe 25 to flow toward the steam generator 21. The water in the pipe 25 flows in the order of the steam generator 21, the turbine 22, and the steam condenser 24 and circulates. In the first embodiment, water is used as the medium for rotating the turbine 22, but other media may be used to rotate the turbine 22.

[0014] The pipe 25 includes a first branch pipe 251 and a second branch pipe 252. The first branch pipe 251 and the second branch pipe 252 are provided between the turbine 22 and the steam condenser 24. The first branch pipe 251 is provided closer to the turbine 22 side than the second branch pipe 252. The first branch pipe 251 returns to the pipe 25 through a heating unit 325 described later. The second branch pipe 252 returns to the pipe 25 through a heat exchanger 42 described later.

[0015] The steam generator 21 exchanges heat between the water in the pipe 25 and the heat medium in the heat collection pipe 12 to vaporize the water in the pipe 25 and generate steam. The turbine 22 is provided with blades that rotate upon receiving steam and a shaft 23 that serves as a rotation axis for the turbine 22 to rotate. The shaft 23 transmits the rotational force of the turbine 22 to various devices and serves as a drive source for driving the various devices. More specifically, the shaft 23 drives a gas compressor 31, a carbon dioxide compressor 41, and a press-fitting pump 51 described later. The steam condenser 24 changes the state of the steam that has rotated the turbine 22 into a liquid.

[0016] The separation unit 30 separates and recovers carbon dioxide from the air in the atmosphere. The separation unit 30 includes a gas compressor 31 and a chemical absorption type separation unit 32. The gas compressor 31 compresses the gas and supplies it to the chemical absorption separation unit 32. The gas compressor 31 is a rotary compressor. The drive unit of the gas compressor 31 is directly connected to the shaft 23 and rotates in conjunction with the rotation of the shaft 23. Alternatively, the shaft 23 and the drive unit of the gas compressor 31 may be connected via a transmission. The transmission is, for example, a device that combines multiple gears with different numbers of teeth. The transmission changes the magnitude of the torque and the rotational speed of the rotational power transmitted from the shaft 23 and transmits the rotational power to the gas compressor 31. The gas compressor 31 only needs to be able to use the rotational power of the shaft 23 and may also be a reciprocating compressor. In this case, the gas compressor 31 converts the rotational power of the shaft 23 into reciprocating motion, causing a piston to reciprocate and compress the gas. In the illustrated example, the gas compressor 31 is supplied with air from the atmosphere, but biogas or combustion exhaust gas may also be supplied.

[0017] The chemical absorption separation unit 32 is a device that separates carbon dioxide by chemical absorption. The chemical absorption separation unit 32 comprises an absorption tower 321, a microbubble supply pipe 322, a regeneration tower 323, a heating unit 325, and absorbent liquid piping 326 and 327. The absorption tower 321 stores an absorbent liquid that absorbs carbon dioxide, and a microbubble supply pipe 322 is inserted into it, through which compressed air from the gas compressor 31 is injected. The absorbent liquid is, for example, an aqueous amine solution. The microbubble supply tube 322 ejects microbubbles into the absorbent liquid. Microbubbles are gases that have been made into tiny bubbles so that carbon dioxide can be easily absorbed into the absorbent liquid. Examples include nanobubbles, which have a size of less than 0.001 mm, and microbubbles, which have a size between 0.001 mm and 0.1 mm. The regeneration tower 323 recovers carbon dioxide by desorbing it from the absorbent liquid that has absorbed it. The heating section 325 heats the absorbent liquid in the regeneration tower 323. The first branch pipe 251 passes through to the heating section 325, and steam that has done work in the turbine 22 is sent through it. This steam heats the absorbent liquid in the regeneration tower 323. The absorbent liquid piping 326 connects the absorption tower 321 and the regeneration tower 323. The absorbent liquid piping 326 is equipped with a liquid transfer pump 326a that delivers the absorbent liquid from the absorption tower 321 to the regeneration tower 323. The absorbent liquid piping 327 connects the absorption tower 321 and the regeneration tower 323. The absorbent liquid piping 327 is equipped with a liquid transfer pump 327a that delivers the absorbent liquid from the regeneration tower 323 to the absorption tower 321. The liquid transfer pumps 326a and 327a are connected to the shaft 23 via a power transmission unit (not shown) and operate using the rotational power of the shaft 23. These liquid transfer pumps 326a and 327a are examples of liquid transfer pumps.

[0018] The liquefaction unit 40 liquefies the carbon dioxide gas separated and recovered by the separation unit 30. The liquefaction unit 40 comprises a carbon dioxide compressor 41, a heat exchanger 42, and a carbon dioxide cooler 43. The carbon dioxide compressor 41 is a rotary compressor. The drive unit of the carbon dioxide compressor 41 is directly connected to the shaft 23 and rotates in conjunction with the rotation of the shaft 23. Alternatively, the shaft 23 and the drive unit of the carbon dioxide compressor 41 may be connected via a transmission. The carbon dioxide compressor 41 only needs to be able to use the rotational power of the shaft 23 and may also be a reciprocating compressor. In this case, the carbon dioxide compressor 41 converts the rotational power of the shaft 23 into reciprocating motion, causing a piston to reciprocate and compress the gas. In the first embodiment, the rotating shaft of the turbine 22 and the rotating shaft of the carbon dioxide compressor 41 are connected coaxially. However, the steam generated from the steam generator 21 may be branched and supplied to multiple turbines, allowing the liquid transfer pump and the carbon dioxide compressor to be operated under independent control.

[0019] The heat exchanger 42 is connected to the regenerator 433 (described later) of the carbon dioxide cooler 43 via the second branch pipe 252. The heat exchanger 42 exchanges heat with the absorption solution in the regenerator 433, heating the absorption solution.

[0020] The carbon dioxide cooler 43 is an absorption-type refrigerator that cools carbon dioxide using the heat of vaporization of water as a refrigerant. The carbon dioxide cooler 43 comprises an evaporator 431, an absorber 432, a regenerator 433, and a condenser 434. The evaporator 431, absorber 432, regenerator 433, and condenser 434 are connected by piping. A pipe through which carbon dioxide gas passes is routed to the evaporator 431. The water supplied to the evaporator 431 vaporizes while absorbing heat from the carbon dioxide gas. As a result, the carbon dioxide gas is cooled and becomes liquefied carbon dioxide. The absorber 432 absorbs the water vaporized in the evaporator 431 into the absorbent solution (for example, an aqueous lithium bromide solution). The absorber 432 then transports the absorbent solution, whose concentration has decreased after absorbing the water, to the regenerator 433. The regenerator 433 uses a heat exchanger 42 to heat the absorption solution and generate steam. The absorption solution, whose concentration has increased due to the generation of steam, is then supplied back to the absorber 432. The condenser 434 condenses the water vapor generated by the regenerator 433. The water liquefied by the condenser 434 is then supplied again to the evaporator 431.

[0021] The press-fitting section 50 includes a press-fitting pump 51 and a press-fitting well 52. The injection pump 51 adds energy to the liquefied, separated carbon dioxide to inject carbon dioxide into the geological formation. The injection pump 51 is, for example, a positive displacement pump. The drive unit of the injection pump 51 is directly connected to the shaft 23 and rotates in conjunction with the rotation of the shaft 23. Alternatively, the shaft 23 and the drive unit of the injection pump 51 may be connected via a transmission. The injection pump 51 only needs to be able to use the rotational power of the shaft 23. The injection pump 51 may impart energy to the liquid by rotational motion or by reciprocating motion. When imparting energy to the liquid by reciprocating motion, the injection pump 51 converts the rotational power of the shaft 23 into reciprocating motion to cause a piston to reciprocate. The injection pump 51 is an example of a liquid transfer pump.

[0022] The injection well 52 is a pipe that extends underground, reaching deep into bedrock or geological formations that do not allow carbon dioxide to pass through. The injection well 52 may extend, for example, to an oil reservoir or a natural gas reservoir, and the separated and recovered carbon dioxide may be injected into the cavity left after the oil or natural gas has been pumped out. The injection pump 51 is connected to the shaft 23. The injection pump 51 is driven by the rotation of the shaft 23. The injection pump 51 pressurizes liquefied carbon dioxide and injects it into the ground through the injection well 52 for storage.

[0023] [The process of separating and recovering carbon dioxide] First, air from the atmosphere is supplied to the gas compressor 31 of the separation unit 30. The gas compressor 31 compresses the supplied air and supplies the compressed air to the chemical absorption separation unit 32. The chemical absorption separation unit 32 supplies the supplied air into the absorption tower 321 via the microbubble supply pipe 322. A portion of the carbon dioxide in the air supplied into the absorption tower 321 is absorbed by the absorbent liquid. Hereinafter, the absorbent liquid that has absorbed carbon dioxide may be referred to as the rich absorbent liquid. The absorption tower 321 releases air with a reduced carbon dioxide concentration into the atmosphere.

[0024] The absorption tower 321 supplies the rich absorbent to the regeneration tower 323. In the regeneration tower 323, the rich absorbent is heated to separate the absorbent from carbon dioxide. The separated carbon dioxide is then supplied to the liquefaction unit 40. The regenerated absorbent is then supplied back to the absorption tower 321 for circulation. The chemical absorption separation unit 32 is an example of a circulation and regeneration mechanism for carbon dioxide absorbent. The chemical absorption separation unit 32 is also an example of a carbon dioxide gas separation and recovery function. However, even if the absorbent has been heated and regenerated, if the temperature of the absorbent is high, its absorption performance when absorbing carbon dioxide again will decrease. Therefore, a cooler may be provided to cool the regenerated absorbent. For example, cold energy may be generated in a carbon dioxide cooler 43, and this cold energy may be used to cool the regenerated absorbent.

[0025] The carbon dioxide gas supplied to the liquefaction unit 40 is compressed by the carbon dioxide compressor 41 to a pressure greater than the pressure at the triple point of carbon dioxide. The compressed carbon dioxide gas is then cooled and liquefied by the carbon dioxide cooler 43 while maintaining its pressure.

[0026] The liquefied carbon dioxide is transported to the injection section 50. The liquefied carbon dioxide transported to the injection section 50 is then pumped into the injection well 52 by the injection pump 51 of the injection section 50. The liquefied carbon dioxide is injected into the underground geological formation to which the injection well 52 is connected and stored underground.

[0027] [Operation of the heat storage unit] The heat storage unit 13 stores excess solar heat generated when sunlight is irradiating the solar collector 11 and the excess heat exceeds the amount of heat required for steam generation in the steam generator 21. The heat storage unit 13 also supplies the stored heat to the drive unit 20 when sunlight is not irradiating the solar collector 11. The period when sunlight is irradiating the solar collector 11 is, for example, a sunny day when sunlight is shining on the ground. The period when sunlight is not irradiating the solar collector 11 is, for example, the night after sunset until sunrise the next day, or periods when the weather is cloudy or rainy.

[0028] When the heat storage unit 13 performs heat storage, the heat storage medium contained in the low-temperature tank 13b is moved to the high-temperature tank 13a. At this time, the heat storage medium passes through the heat exchanger 13d, which is located between the low-temperature tank 13b and the high-temperature tank 13a. In the heat exchanger 13d, the heat storage medium is heated by exchanging heat with the heat medium in the heat collecting tube 12. The heated, high-temperature heat storage medium is then flowed into the high-temperature tank 13a for storage.

[0029] Furthermore, the heat storage unit 13 supplies the heat it stores to the water circulating in the drive unit 20 during periods when solar heat is not supplied to the solar collector 11. More specifically, the heat storage unit 13 flows the heat storage medium from the high-temperature tank 13a to the low-temperature tank 13b, and the heat exchanger 13d exchanges heat with the heat medium in the solar collector tube 12. The heat medium in the solar collector tube 12 is heated by the heat storage medium and becomes hot. The heat medium in the solar collector tube 12 flows to the steam generator 21 and heats the water in the piping 25. The water in the piping 25 is heated by the heat transfer medium in the heat collector tube 12, turning into steam that rotates the turbine 22. In other words, the turbine 22 is driven by the heat provided by the heat storage unit 13. The rotation of the turbine 22 causes the shaft 23 to rotate, which in turn drives various devices that use the shaft 23 as a driving source. More specifically, the gas compressor 31, the carbon dioxide compressor 41, and the injection pump 51 are rotated. In other words, the gas compressor 31 is driven by the rotation of the turbine 22. The carbon dioxide compressor 41 is also driven by the rotation of the turbine 22. The injection pump 51 is also driven by the rotation of the turbine 22.

[0030] Furthermore, the heat supplied from the heat storage unit 13 is supplied to the heating unit 325 via the first branch pipe 251. The heating unit 325 heats the absorbent liquid, separating and recovering carbon dioxide. Furthermore, the heat supplied from the heat storage unit 13 is supplied to the heat exchanger 42 via the second branch pipe 252. The carbon dioxide cooler 43 uses the heat exchanger 42 to cool and liquefy the carbon dioxide gas.

[0031] With this configuration, the carbon dioxide separation and recovery system 1 according to the first embodiment can utilize solar heat to separate and recover carbon dioxide and inject and store it underground with a high operating rate, not only at night, during sunset and sunrise, but also during daytime hours, including rainy or cloudy days.

[0032] Furthermore, when the amount of solar heat collected by the solar collector 11 exceeds the amount of steam generated by the steam generator 21 necessary for the operation of the carbon dioxide separation and recovery system 1, and the excess solar heat is collected and stored in the heat storage unit 13, it is desirable that, as a method of circulating the heat transfer medium in the solar collector tube 12, the excess heat is stored in the heat storage unit 13 via a circulation path that passes through the solar collector 11 and the heat exchanger 13d, in addition to the circulation path that passes through the solar collector 11 and the steam generator 21. To achieve this, it is desirable to control the on / off valves provided on the branched flow paths of the upstream and downstream sections of the heat exchanger 13d, and during periods when excess heat is generated, open the valves on the upstream and downstream circulation paths of the heat exchanger 13d, which were closed during periods when excess heat was not generated, and allow the heat transfer medium to circulate in both the circulation path that passes through the steam generator 21 and the circulation path that passes through the heat exchanger 13d, thereby enabling the carbon dioxide separation and recovery system 1 to operate while the excess solar heat is stored in the heat storage unit 13.

[0033] Furthermore, when supplying the heat stored in the heat storage unit 13 to the water circulating in the drive unit 20 during periods when solar heat is not supplied to the solar collector 11, it is preferable to control the on / off valves provided on the branched flow paths of the upstream and downstream parts of the heat exchanger 13d. During periods when solar heat is not supplied to the solar collector 11, the valve in the circulation path passing through the solar collector 11 is closed, and only the valve that forms a circulation path passing through the heat exchanger 13d and the steam generator 21 is opened. This selectively allows the heat stored in the heat storage unit 13 to circulate only through the circulation path passing through the steam generator 21, thereby efficiently utilizing the heat stored in the heat storage unit 13 for steam generation.

[0034] Furthermore, in the carbon dioxide separation and recovery system 1, the rotational force of the shaft 23 is used to drive the gas compressor 31, the carbon dioxide compressor 41, and the injection pump 51. However, the shaft 23 does not necessarily need to drive all three of the gas compressor 31, the carbon dioxide compressor 41, and the injection pump 51; it may drive only one of them. Also, the second branch pipe 252 is located downstream of the first branch pipe 251 in the direction of water flow within the piping 25, but it may also be located upstream of the first branch pipe 251.

[0035] [Modification 1 of the first embodiment] Figure 2 shows the overall configuration of the carbon dioxide separation and recovery system 2 according to Modification 1 of the first embodiment. Modification 1 of the first embodiment differs from the first embodiment in that the chemical absorption separation unit 32 of the separation unit 30 is replaced with a physical adsorption separation unit 34. Note that the same reference numerals are used for functions similar to those in the first embodiment, and their explanation is omitted here.

[0036] The carbon dioxide separation and recovery system 2 comprises a solar thermal collection unit 10, a drive unit 20, a separation unit 230, a liquefaction unit 40, and an injection unit 50. The separation unit 230 comprises a gas compressor 31 and a physical adsorption separation unit 34. The physical adsorption separation unit 34 comprises an adsorption tank 341, a heat exchanger 342, and a suction pump 343.

[0037] The adsorption tank 341 stores an adsorbent material that adsorbs carbon dioxide inside the tank. Examples of adsorbents include zeolite and activated carbon. The adsorption tank 341 is also equipped with an openable and closable outlet 341a. The outlet 341a is used to replace the gas inside the adsorption tank 341. The heat exchanger 342 heats the inside of the adsorption tank 341. Steam that has done work in the turbine 22 is supplied to the heat exchanger 342 via the first branch pipe 251. The heat from this steam heats the inside of the adsorption tank 341. The suction pump 343 reduces the pressure inside the adsorption tank 341. The suction pump 343 includes a gear 343a mounted on the shaft 23 to obtain rotational power for the shaft 23, and a rotating shaft 343b that transmits the rotational power of the gear 343a to the suction pump 343. The rotating shaft 343b is connected to the drive unit of the suction pump 343, and the suction pump 343 is driven by the rotational power of the rotating shaft 343b.

[0038] [The process of separating and recovering carbon dioxide] In the physical adsorption method, carbon dioxide is separated from other gases using a pressure difference or temperature difference. Specifically, first, the outlet 341a of the adsorption tank 341 is closed and the gas compressor 31 is driven. Compressed air from the gas compressor 31 is supplied to the adsorption tank 341, increasing the pressure inside the adsorption tank 341. When the pressure inside the adsorption tank 341 increases, the adsorbent material adsorbs carbon dioxide. Next, the outlet 341a is opened and the gas with a lower carbon dioxide concentration is discharged. Then, after closing the outlet 341a, the suction pump 343 is driven to reduce the pressure inside the adsorption tank 341. When the pressure inside the adsorption tank 341 decreases, carbon dioxide is desorbed from the adsorbent material. Finally, the desorbed carbon dioxide is recovered.

[0039] Furthermore, adsorbents generally have a higher adsorption rate at low temperatures and a lower adsorption rate at high temperatures. Therefore, the adsorption tank 341 may be heated when desorbing carbon dioxide from the adsorbent. Heating the adsorbent allows more carbon dioxide to be desorbed, so compared to not heating the adsorbent, more carbon dioxide can be adsorbed when the adsorbent is reused. Heating the adsorption tank 341 is performed by supplying steam to the heat exchanger 342 via the first branch pipe 251. Alternatively, the adsorption tank 341 may be cooled when adsorbing carbon dioxide onto the adsorbent. For example, cold energy may be generated using a carbon dioxide cooler 43 and supplied to the adsorption tank 341. The physical adsorption separation unit 34 is an example of a heating and regeneration mechanism for carbon dioxide adsorbent and an example of a carbon dioxide gas separation and recovery function.

[0040] Thus, in this modified example 1 of the first embodiment, carbon dioxide can be separated by changing the pressure inside the adsorption tank 341 using a gas compressor 31 driven by heat supplied from the heat storage unit 13 and a suction pump 343. Furthermore, carbon dioxide can be efficiently separated by changing the temperature inside the adsorption tank 341 using the heat supplied from the heat storage unit 13.

[0041] In Modification 1 of the First Embodiment, carbon dioxide is separated using both pressure changes and temperature changes in the adsorption tank 341. However, carbon dioxide may also be separated using only one of the pressure changes or temperature changes in the adsorption tank 341.

[0042] [Modification 2 of the first embodiment] Figure 3 shows the overall configuration of the carbon dioxide separation and recovery system 3 according to a modified example 2 of the first embodiment. Modification 2 of the first embodiment differs from the first embodiment in that the chemical absorption separation unit 32 is replaced with a separation membrane module 36. The same reference numerals are used for functions similar to those in the first embodiment, and their explanation is omitted here.

[0043] The carbon dioxide separation and recovery system 2 comprises a solar thermal collection unit 10, a drive unit 20, a separation unit 330, a liquefaction unit 40, and an injection unit 50. The separation unit 330 comprises a gas compressor 31 and a separation membrane module 36.

[0044] The separation membrane module 36 comprises a separation membrane 361 and a suction pump 362. The separation membrane 361 selectively allows carbon dioxide to pass through. The separation membrane 361 is positioned inside the tube of the tubular separation membrane module 36, dividing the inside of the tube into an upstream side and a downstream side. The suction pump 362 is located downstream of the separation membrane 361 and reduces the air pressure on the downstream side inside the separation membrane module 36. The suction pump 362 includes a gear 362a mounted on the shaft 23 to obtain rotational power for the shaft 23, and a rotating shaft 362b that transmits the rotational power of the gear 362a to the suction pump 362. The rotating shaft 362b is connected to the drive unit of the suction pump 362, and the suction pump 362 is driven by the rotational power of the rotating shaft 362b. Examples of suction pumps 362 include vacuum pumps and pressure reducing pumps.

[0045] [The process of separating and recovering carbon dioxide] First, atmospheric air is supplied to the gas compressor 31 of the separation unit 30. The gas compressor 31 compresses the supplied air to make the air pressure greater than atmospheric pressure. The magnitude of the air pressure compressed by the gas compressor 31 is set appropriately according to the performance of the separation membrane, etc. Furthermore, the suction pump 362 is driven to reduce the pressure on the downstream side of the separation membrane 361. This creates a pressure difference between the upstream and downstream sides of the separation membrane 361, causing carbon dioxide gas to pass through the separation membrane and move downstream. The carbon dioxide that has moved downstream is recovered and supplied to the liquefaction unit 40. Meanwhile, the air remaining on the upstream side of the separation membrane 361, with a lower concentration of carbon dioxide, is discharged into the atmosphere.

[0046] [Second Embodiment] Figure 4 shows the overall configuration of the carbon dioxide separation and recovery system 4 according to the second embodiment. The second embodiment differs from the second modification of the first embodiment in that it further includes a renewable energy generation unit 60. Furthermore, the liquefaction unit 240 of the second embodiment differs from the liquefaction unit 40 of the first embodiment in that the carbon dioxide cooler 43 is replaced by a turbo chiller 73. Note that the same reference numerals are used for functions similar to those in the first embodiment, and their explanation is omitted here.

[0047] The renewable energy generation unit 60 can be exemplified by solar power generation, solar thermal power generation, wind power generation, geothermal power generation, or hydroelectric power generation. In the second embodiment, solar power generation will be described as an example. The renewable energy generation unit 60 may be equipped with power transmission facilities to supply electricity to the outside, or it may supply electricity only to the carbon dioxide separation and recovery system 4.

[0048] The renewable energy generation unit 60 comprises a photovoltaic power generation device 61 and an energy storage unit 62. The photovoltaic power generation device 61 can use solar cells that generate electricity when exposed to sunlight. The type of solar cell is not particularly limited, but examples include silicon-based solar cells and compound-based solar cells. The electricity generated by the photovoltaic power generation device 61 is supplied to various devices of the carbon dioxide separation and recovery system 4. The energy storage unit 62 is a rechargeable and dischargeable device, such as a battery. The energy storage unit 62 stores a portion of the electricity generated by the solar power generation device 61. The energy storage unit 62 supplies the stored electricity to various devices of the carbon dioxide separation and recovery system 4.

[0049] The liquefaction unit 240 includes a carbon dioxide compressor 41 and a turbo chiller 73. The turbo chiller 73 has an internal compressor, which is used to compress the refrigerant and execute the refrigeration cycle. The carbon dioxide gas cooled by this turbo chiller 73 is liquefied to become liquefied carbon dioxide. In the second embodiment, the compressor of this turbo chiller 73 is driven by electricity supplied by the renewable energy generation unit 60. During periods when sunlight does not irradiate the unit, such as at night, the energy storage unit 62 supplies power to the turbo chiller 73.

[0050] In the carbon dioxide separation and recovery system 4 according to the second embodiment, even in places where there are no power lines, such as deserts, carbon dioxide from the atmosphere can be separated and recovered from the air surrounding the system on-site and stored underground.

[0051] 〔others〕 In this embodiment, an absorption-type refrigerator was used as the carbon dioxide cooler 43, but an adsorption-type refrigerator may also be used. In this embodiment, carbon dioxide is separated and recovered from the atmosphere, but for example, carbon dioxide may be separated from biogas discharged from a biomass fermentation tank. Furthermore, the arrangement of the mirrors for collecting solar heat is not particularly limited. For example, a large number of planar mirrors may be arranged on the ground to surround the tower, with respect to the solar collector 11 mounted on the top of the tower. In this embodiment, liquefied carbon dioxide was stored in the geological formation using the injection pump 51, but liquefied carbon dioxide may also be used as a raw material gas for commercial and industrial purposes. In this case, the injection pump 51 may be used to fill carbon dioxide cylinders with high-pressure carbon dioxide gas or to fill tank trucks, etc., with liquefied carbon dioxide. Alternatively, the recovered carbon dioxide can be solidified and used as dry ice. [Explanation of Symbols]

[0052] 1,2,3,4…Carbon dioxide separation and recovery system, 10…Solar thermal collection unit, 11…Collector, 12…Collector tube, 13…Heat storage unit, 13a…High-temperature tank, 13b…Low-temperature tank, 13c…Heat storage tube, 13d…Heat exchanger, 20…Drive unit, 21…Steam generator, 22…Turbine, 23…Shaft, 24…Steam condenser, 25…Piping, 30…Separation unit, 31…Gas compressor, 32…Chemical absorption separation unit, 34…Physical adsorption separation unit, 36…Separation membrane module, 40…Liquefaction unit, 41…Carbon dioxide compressor, 42…Heat exchanger, 43…Carbon dioxide cooler, 50…Injection unit, 51…Injection pump, 52…Injection Well, 60...Renewable energy generation section, 61...Solar power generation equipment, 62...Energy storage section, 73...Turbo chiller, 230...Separation section, 240...Liquefaction section, 251...First branch pipe, 252...Second branch pipe, 321...Absorption tower, 322...Microbubble supply pipe, 323...Regeneration tower, 325...Heating section, 326a, 326b...Liquid transfer pump, 330...Separation section, 341...Adsorption tank, 341a...Discharge port, 342...Heat exchanger, 343...Suction pump, 344...Shaft, 346b...Rotating shaft, 361...Separation membrane, 362...Suction pump, 362a...Gear, 431...Evaporator, 432...Absorber, 433...Regenerator, 434...Condenser

Claims

1. A heat storage unit that stores solar heat and provides heat, The heat provided by the heat storage unit heats the absorbent liquid that has absorbed carbon dioxide contained in the gas, releasing and separating the carbon dioxide, while simultaneously heating and regenerating the absorbent liquid, and then absorbing carbon dioxide contained in the gas again. This is a carbon dioxide absorbent liquid circulation and regeneration mechanism, and a carbon dioxide gas separation and recovery function. A carbon dioxide separation and recovery system equipped with the following features.

2. A heat storage unit that stores solar heat and provides heat, The heat provided by the heat storage unit heats the adsorbent that has adsorbed carbon dioxide contained in the gas, releasing and separating the carbon dioxide, while simultaneously regenerating the adsorbent by heating it, and then absorbing carbon dioxide contained in the gas again. This is a heating and regeneration mechanism for a carbon dioxide adsorbent, and a carbon dioxide gas separation and recovery function. A carbon dioxide separation and recovery system equipped with the following features.

3. A heat storage unit that stores solar heat and provides heat, A turbine driven by the heat provided by the heat storage unit, A gas compressor or vacuum pump driven by the rotation of the turbine, A carbon dioxide separation and recovery system comprising a carbon dioxide separation membrane provided upstream or downstream of the gas compressor or vacuum pump.

4. A heat storage unit that stores solar heat and provides heat, A turbine driven by the heat provided by the heat storage unit, A gas compressor driven by the rotation of the turbine, A carbon dioxide separation and recovery system characterized by injecting a high-pressure gas containing carbon dioxide, which has been pressurized by the gas compressor, into the carbon dioxide absorption liquid described in claim 1 in the form of fine bubbles.

5. A heat storage unit that stores solar heat and provides heat, A turbine driven by the heat provided by the heat storage unit, A gas compressor driven by the rotation of the turbine, A carbon dioxide separation and recovery system characterized by supplying a high-pressure gas containing carbon dioxide, which has been pressurized by the gas compressor, into a container containing the carbon dioxide absorbent described in claim 2.

6. A heat storage unit that stores solar heat and provides heat, A turbine driven by the heat provided by the heat storage unit, A vacuum pump driven by the rotation of the turbine, A carbon dioxide separation and recovery system characterized in that the vacuum pump is provided on the carbon dioxide gas separation and recovery piping of a container containing the carbon dioxide absorbent described in claim 2, and the carbon dioxide gas is desorbed and then recovered by suction while the pressure inside the container containing the carbon dioxide absorbent is changed.

7. A heat storage unit that stores solar heat and provides heat, A turbine driven by the heat provided by the heat storage unit, The system includes a gas compressor driven by the rotation of the turbine, The carbon dioxide separation and recovery system is characterized in that the gas compressor further pressurizes and compresses the carbon dioxide gas separated and recovered by any of the methods described in claims 1 to 6 to obtain high-pressure carbon dioxide gas.

8. A heat storage unit that stores solar heat and provides heat, An absorption chiller or adsorption chiller driven by the heat provided by the heat storage unit, A carbon dioxide separation and recovery system characterized by supplying the cold energy obtained by driving the aforementioned refrigerator to cool a carbon dioxide absorption liquid, a carbon dioxide adsorbent, or a pressurized compressed gas, thereby improving the carbon dioxide separation and recovery performance or liquefying the separated and recovered carbon dioxide.

9. A heat storage unit that stores solar heat and provides heat, A turbine driven by the heat provided by the heat storage unit, A liquid transfer pump driven by the rotation of the turbine, A carbon dioxide separation and recovery system characterized by using the aforementioned liquid transfer pump to circulate and flow a carbon dioxide absorption liquid, to transfer liquefied carbon dioxide that has been separated and recovered, or to pressurize and store liquefied carbon dioxide that has been separated and recovered into the ground.

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