Co2 recovery system

Abstract

To provide a CO2 recovery system capable of reducing energy required for recovering CO2.SOLUTION: A CO2 recovery system includes a compression part, a storage part, an expansion part, and a recovery par. The compression part is configured to compress source gas containing CO2 and produce compression gas. The storage part is configured to store the compression gas as it is or converting the compression gas into liquid gas by liquefaction. The expansion part is configured to expand the compression gas or the liquid gas discharged from the storage part. The recovery part is configured to immobilize the CO2 in the compression gas to an immobilization material.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a CO2 capture system for capturing CO2 (carbon dioxide) contained in a source gas. [Background technology]

[0002] Patent Document 1 discloses a technology for recovering CO2 contained in the air by adsorbing it onto an adsorption rotor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-45570 A Summary of the Invention [Problem to be solved by the invention]

[0004] The configuration of Patent Document 1 requires a blower to send a large amount of air to the adsorption rotor. There is a problem in that a huge amount of energy is required to operate the blower, and there is a demand for reducing the energy required for CO2 capture.

[0005] The present invention has been made in view of the above circumstances, and provides a CO2 capture system capable of reducing the energy required for capturing CO2. [Means for solving the problem]

[0006] According to the present invention, the following inventions are provided. [1] A CO2 capture system comprising a compression unit, a storage unit, an expansion unit, and a capture unit, wherein the compression unit is configured to compress a source gas containing CO2 to generate compressed gas, the storage unit is configured to store the compressed gas as is or as a liquefied gas by liquefaction, the expansion unit is configured to expand the compressed gas or the liquefied gas discharged from the storage unit, and the capture unit is configured to fix CO2 in the compressed gas to an immobilization material. [2] A CO2 capture system as described in [1], further comprising a heat exchange unit, the heat exchange unit comprising a cooling unit and a heating unit, the cooling unit configured to cool the compressed gas generated in the compression unit to recover thermal energy, and the heating unit configured to heat the compressed gas or the liquefied gas discharged from the storage unit using the thermal energy recovered in the cooling unit. [3] A CO2 capture system according to the above item [2], wherein the capture unit is configured to regenerate the immobilization material by heating the immobilization material using the thermal energy recovered by the cooling unit to desorb CO2 from the immobilization material. [4] A CO2 recovery system according to [3], wherein the heating of the immobilization material is carried out by contacting water vapor heated using the thermal energy with the immobilization material. [5] A CO2 capture system described in any one of [1] to [4], wherein the compression section is configured to perform the compression using electric power, and the expansion section is configured to use the force generated during the expansion to rotate a turbine to generate electricity. [6] The CO2 recovery system according to any one of [1] to [5], wherein the CO2 concentration in the source gas is 0.01 to 0.1% by volume. [7] The CO2 capture system according to any one of [1] to [6], wherein the immobilization material is a solid. [8] A CO2 capture system according to any one of [1] to [7], wherein the capture unit includes a first and a second capture unit, each of which includes the immobilization material; in a first operating state, the first capture unit performs a fixation operation and the second capture unit performs a regeneration operation; and in a second operating state, the second capture unit performs a fixation operation and the first capture unit performs a regeneration operation; the first operating state and the second operating state are configured to be switchable; in the fixation operation, CO2 is fixed to the immobilization material; and in the regeneration operation, the CO2 is desorbed from the immobilization material. [9] The CO2 recovery system according to any one of [1] to [6], wherein the immobilizing material is an amine solution or an amine-containing liquid. Effect of the Invention

[0007] In the CO2 capture system of the present invention, a capture section for capturing CO2 is incorporated into a compressed air storage system (so-called "CAES") or liquefied air energy storage (so-called "LAES"), which compresses source gas, stores it as compressed gas or liquefied gas, and uses it for power generation when needed. The energy required for compressing the source gas was originally required in CAES or LAES, and the additional energy required by incorporating a capture section into such a system is very small. Therefore, by incorporating a capture section into CAES or LAES, it becomes possible to capture CO2 with almost no additional energy required. Therefore, according to the present invention, the energy required for capturing CO2 can be reduced. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram showing a configuration of a CO2 capture system 1 according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing a configuration of a CO2 capture system 1 according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present invention will be described. Various features shown in the following embodiments can be combined with each other. Also, each feature can be an invention independently.

[0010] 1. First embodiment A CO2 capture system 1 according to a first embodiment of the present invention will be described with reference to Fig. 1. The CO2 capture system 1 of this embodiment includes a compression section 2, a storage section 3, an expansion section 4, and a capture section 5. The system 1 also preferably includes a heat exchanger 6. Each component will be described in detail below.

[0011] <Compression section 2> The compression unit 2 is configured to compress a source gas containing CO2 to generate a compressed gas G1. The "compressed gas G1" refers to the compressed gas before removing CO2. The compressed gas after removing CO2 is called "compressed gas G2", and when there is no need to distinguish whether or not CO2 has been removed, it is called "compressed gas G". The source gas may be the atmosphere or exhaust gas generated in a power plant or the like. The CO2 concentration contained in the source gas is not particularly limited, but the present invention is characterized in that it is possible to efficiently capture CO2 even when the CO2 concentration in the source gas is low, so that the technical significance of applying the present invention is significant when the CO2 concentration of the source gas is low (for example, when the source gas is the atmosphere).

[0012] In addition, if the CO2 concentration in the source gas is high, the CO2 fixation rate in the immobilizing material 5a in the capture section 5 increases accordingly, and the frequency of the regeneration operation of the immobilizing material 5a needs to be increased. From this viewpoint, it is preferable that the CO2 concentration in the source gas is not too high. The CO2 concentration in the source gas is, for example, 0.01 to 20% by volume, preferably 0.01 to 1% by volume, and more preferably 0.01 to 0.1% by volume. Specifically, this concentration is, for example, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 1, 5, 10, 15, or 20% by volume, and may be in the range between any two of the values ​​exemplified here.

[0013] The compression unit 2 is preferably configured to perform the compression using electric power, and in one example, is a compressor operated by driving a motor 2a with electric power. In the compression unit 2, the source gas is compressed, for example, 20 to 200 times, preferably 40 to 100 times. The pressure of the compressed gas G1 is, for example, 20 to 200 barA, and preferably 40 to 100 barA. Specifically, this pressure may be, for example, 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, or 200 barA, or may be in a range between any two of the numerical values ​​exemplified here.

[0014] It is preferable that the power for driving the motor 2a is derived from natural energy such as solar power or wind power. Since it is not easy to adjust the amount of power generated from natural energy, there are cases where more power than necessary is generated, resulting in surplus power. By using this surplus power to drive the motor 2a, the energy of the surplus power can be stored in the storage unit 3. For this reason, it is preferable that the motor 2a is not driven all the time, but is driven to consume the surplus power when it occurs.

[0015] On the other hand, when the source gas is one that requires continuous treatment, such as exhaust gas from a power plant, it is preferable that the motor 2a is continuously driven by electric power from a commercial power source.

[0016] <Heat exchanger 6> The heat exchanger 6 includes a cooling section 6a and a heating section 6b, and can perform heating in the heating section 6b by using thermal energy recovered in the cooling section 6a.

[0017] The cooling section 6a is preferably disposed downstream of the compression section 2. The compressed gas G1 is at a high temperature because the temperature is raised when the source gas is compressed. If the compressed gas G1 is brought into contact with the immobilization material 5a in a high temperature state, problems such as damage to the immobilization material 5a may occur. Therefore, it is preferable to cool the compressed gas G1 in the cooling section 6a to a temperature suitable for contacting the immobilization material 5a and recover the thermal energy at that time. In FIG. 1, the compression section 2 and the cooling section 6a are configured in one stage for convenience of illustration, but it is preferable that the compression section 2 and the cooling section 6a are configured in multiple stages, that is, the compression section 2 and the cooling section 6a are arranged alternately in multiple stages to perform compression and cooling repeatedly. In this case, it is possible to prevent the source gas from becoming too hot due to compression. The number of stages of the compression section 2 and the cooling section 6a is preferably, for example, 2 to 6 stages, specifically, for example, 2, 3, 4, 5, and 6 stages, and may be in a range between any two of the numerical values ​​exemplified here. The temperature of the compressed gas G1 after cooling is, for example, 20 to 80°C, preferably 30 to 70°C, specifically, for example, 20, 30, 40, 50, 60, 70, or 80°C, or may be in the range between any two of the numerical values ​​exemplified here.

[0018] The heating unit 6b preferably includes one or both of a first heating unit 6b1 and a second heating unit 6b2. The first heating unit 6b1 is configured to heat the condensed water to generate water vapor. The second heating unit 6b2 is configured to heat the compressed gas G or the liquefied gas L discharged from the storage unit 3.

[0019] <Collection Division 5> The capture unit 5 is configured to fix CO2 in the compressed gas G1 in the immobilization material 5a. The immobilization material 5a is disposed in the capture unit 5, and the compressed gas G1 is supplied into the capture unit 5 to contact the immobilization material 5a, and then the compressed gas G2 is discharged from the capture unit 5, whereby the CO2 contained in the compressed gas G1 can be fixed in the immobilization material 5a and removed.

[0020] The compressed gas G1 has a higher CO2 partial pressure than the source gas, so that CO2 can be efficiently fixed in the immobilization material 5a. In addition, when the CO2 partial pressure of the source gas is very low, the options for available immobilization materials are limited, but by compressing the source gas and increasing the CO2 partial pressure, the options for available immobilization materials increase, so that cost reduction can be expected.

[0021] The immobilizing material 5a may be solid or liquid. The solid immobilizing material 5a is preferably powdered or porous. Examples of the solid immobilizing material 5a include an amine-supported solid absorbent, zeolite, an organic metal framework, and an ion exchange resin. The amine-supported solid absorbent is configured by supporting an amine on the surface of a carrier. The carrier is preferably an inorganic oxide such as silica. The organic metal framework is a crystalline porous material consisting of a metal and an organic ligand. The liquid immobilizing material 5a is preferably an amine-containing liquid. The amine-containing liquid may be a liquid amine consisting of only amine, or may be an amine solution in which amine is dissolved in a solvent (e.g., water). The ratio of amine in the amine-containing liquid is, for example, 10 to 100% by mass, specifically, for example, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100% by mass, and may be within a range between any two of the numerical values ​​exemplified here.

[0022] As the CO2 in the compressed gas G1 is fixed in the immobilization material 5a, the amount of CO2 fixed in the immobilization material 5a increases, and the function of the immobilization material 5a to fix CO2 decreases accordingly. For this reason, it is preferable to regenerate the immobilization material 5a by performing a regeneration operation to desorb CO2 from the immobilization material 5a. The CO2 desorbed from the immobilization material 5a is compressed in the CO2 compression section 7 and stored in the CO2 storage section 8. The CO2 stored in the CO2 storage section 8 can be used as a CO2 source or can be injected into a reservoir deep underground (for example, deeper than 800 m underground) for long-term storage.

[0023] The desorption of CO2 from the immobilizing material 5a can be performed by changing the environmental conditions such as the temperature, pressure, and humidity of the environment in which the immobilizing material 5a is placed. For example, when the immobilizing material 5a is an amine-supported solid absorbent, a zeolite, or an organic metal framework, the CO2 can be desorbed from the immobilizing material 5a by increasing the temperature of the immobilizing material 5a or reducing the pressure around the immobilizing material 5a. When the immobilizing material 5a is an amine-containing liquid, the CO2 can be desorbed by heating the amine-containing liquid in a reboiler. When the immobilizing material 5a is an ion exchange resin that has the property of adsorbing CO2 in a normal dry state and desorbing CO2 in a wet state, the CO2 can be desorbed from the immobilizing material 5a by humidifying the area around the immobilizing material 5a.

[0024] When the immobilization material 5a is regenerated by heating, it is preferable to heat the immobilization material 5a using the thermal energy recovered by the cooling unit 6a. In this case, the supply of energy required for regeneration of the immobilization material 5a from the outside can be reduced or eliminated. For example, when the source gas is the air at 25°C and compressed 80 times to generate compressed gas, the thermal energy required for desorption of CO2 is 1% or less of the thermal energy recoverable when compressing the source gas, so that the immobilization material 5a can be regenerated without the supply of thermal energy from the outside. On the other hand, when a source gas with a high CO2 concentration such as exhaust gas from a power plant is used, the thermal energy required for desorption of CO2 may exceed the thermal energy recoverable when compressing the source gas. In this case, the immobilization material 5a can be regenerated by supplying the insufficient thermal energy from the outside.

[0025] Methods for heating the immobilizing material 5a include a direct heating method and an indirect heating method. In the direct heating method, a heated heating medium (e.g., steam) is brought into direct contact with the immobilizing material 5a, and the thermal energy of the heating medium is transferred to the immobilizing material 5a to heat the immobilizing material 5a. In the indirect heating method, thermal energy from a heated heating medium (e.g., steam) is transferred to the immobilizing material 5a by heat exchange to heat the immobilizing material 5a. The indirect heating method has the advantage that the heating medium does not come into contact with the immobilizing material 5a, so that deterioration or inactivation of the immobilizing material 5a due to contact with the heating medium is suppressed. On the other hand, the direct heating method has the advantage that thermal energy can be transferred more efficiently than the indirect heating method.

[0026] Fig. 1 shows an example of a system configuration in which the immobilizing material 5a is an amine-supported solid absorbent and is heated by a direct heating method. In the system 1 in Fig. 1, the condensed water is heated in the first heating section 6b1 of the heat exchanger 6 to generate steam, and the steam is brought into contact with the immobilizing material 5a to heat the immobilizing material 5a and desorb the CO2 immobilized in the immobilizing material 5a. If the thermal energy of the steam is insufficient for heating in the first heating section 6b1, a heater may be separately disposed between the first heating section 6b1 and the recovery section 5.

[0027] A vacuum pump 9, a cooler 10, a gas-liquid separator 11, a CO2 compression section 7, and a CO2 storage section 8 are connected to the piping on the output side of the recovery section 5 in this order. The vacuum pump 9 is configured to be able to reduce the pressure inside the recovery section 5. This allows a mixed gas of water vapor and CO2 to be sucked out from the recovery section 5. In addition, since the boiling point of water is lowered by reducing the pressure inside the recovery section 5, the temperature of the water vapor generated in the first heating section 6b1 can be lowered. By lowering the temperature of the water vapor, the deterioration and / or inactivation of the immobilization material 5a can be suppressed. In addition, the desorption of CO2 from the immobilization material 5a is further promoted by combining the heating of the immobilization material 5a and the decompression of the surroundings. The vacuum pump 9 can be omitted if it is not necessary.

[0028] The mixed gas sucked out by the vacuum pump 9 is cooled by the cooler 10 and then sent to the gas-liquid separator 11. At least a portion of the water vapor contained in the mixed gas is liquefied by the cooling in the cooler 10 to become condensed water. The condensed water is extracted by the gas-liquid separator 11 and sent to the first heating section 6b1. In this way, the condensed water is circulated and used, so that the supply of water from the outside can be eliminated or the amount of water supply can be reduced. The CO2 discharged from the gas-liquid separator 11 is compressed by the CO2 compression section 7 and stored in the CO2 storage section 8.

[0029] It is preferable that the capture unit 5 is operated by switching between a fixed operation and a regeneration operation. In the fixed operation, the compressed gas G1 is brought into contact with the immobilization material 5a to fix CO2 in the immobilization material 5a. On the other hand, in the regeneration operation, CO2 is desorbed from the immobilization material 5a. When the motor 2a is operated intermittently, such as when the motor 2a is driven by electricity derived from natural energy, it is preferable to perform the fixed operation while the motor 2a is operating and the regeneration operation while the motor 2a is stopped. The regeneration operation may be performed periodically, or may be performed when a decrease in the fixation speed of CO2 by the immobilization material 5a is detected.

[0030] When the motor 2a is operated continuously, the capture unit 5 needs to be constantly in fixed operation, so that it is not easy to perform regeneration operation of the capture unit 5. In this embodiment, in order to solve such a problem, the capture unit 5 is configured to include first and second capture units 5A and 5B. The first and second capture units 5A and 5B each include an immobilizing material 5a, and both the first and second capture units 5A and 5B can fix CO2 in the same manner. In the first operating state, the first capture unit 5A performs fixed operation and the second capture unit 5B performs regeneration operation, and in the second operating state, the second capture unit 5B performs fixed operation and the first capture unit 5A performs regeneration operation. The first operating state and the second operating state are configured to be switchable. This switching can be realized by operating the switching valves 12 provided on the input side piping and the output side piping of the first and second capture units 5A and 5B to switch the connection of the piping. According to this configuration, while a regeneration operation is being performed in one of the first and second collection sections 5A, 5B, a fixing operation can be performed in the other of the first and second collection sections 5A, 5B, so that the regeneration operation can be performed without completely stopping the fixing operation. This configuration is particularly useful when the immobilization material 5a is a solid.

[0031] <Storage Section 3> The storage unit 3 is configured to store the compressed gas G compressed in the compression unit 2 as it is or as a liquefied gas L by liquefaction. When the compressed gas G is converted into the liquefied gas L, it is preferable to provide a liquefaction device for liquefying the compressed gas G on the upstream side of the storage unit 3. The liquefaction device may recover heat generated by liquefaction. In this embodiment, the recovery unit 5 is arranged between the compression unit 2 and the storage unit 3, and the compressed gas G2 from which CO2 has been removed in the recovery unit 5 is stored in the storage unit 3 as it is or as it is liquefied. In another embodiment, the recovery unit 5 may be arranged between the storage unit 3 and the expansion unit 4, and the compressed gas G1 from which CO2 has not been removed may be stored in the storage unit 3 as it is or as it is liquefied. In the latter case, CO2 is removed from the compressed gas G1 or liquefied gas L taken out from the storage unit 3. When the liquefied gas L is taken out from the storage unit 3, it is preferable to heat it and return it to a compressed gas, and then remove CO2 at a point before generating electricity with a turbine. In either case, the compressed gas G or the liquefied gas L is taken out from the storage section 3 at the required timing and sent to the expansion section 4.

[0032] <Expansion section 4> The expansion section 4 is configured to generate expansion gas by expanding the compressed gas G or liquefied gas L discharged from the storage section 3. It is preferable to dispose the second heating section 6b2 upstream of the expansion section 4 and heat the compressed gas G or liquefied gas L in the second heating section 6b2. This makes it easier for the compressed gas G or liquefied gas L to expand.

[0033] The expansion section 4 is preferably configured to generate electricity by rotating a turbine using the force generated during expansion. The turbine is connected to a generator 4a, and the rotation of the turbine is transmitted to the generator 4a to generate electricity.

[0034] In FIG. 1, for convenience of illustration, the second heating section 6b2 and the expansion section 4 are configured in one stage, but it is preferable that the second heating section 6b2 and the expansion section 4 are configured in multiple stages, that is, the second heating section 6b2 and the expansion section 4 are arranged alternately in multiple stages to repeatedly perform heating and expansion. In this case, the heat recovered by the cooling section 6a can be efficiently used for expansion. The number of stages of the second heating section 6b2 and the expansion section 4 is preferably, for example, 2 to 6 stages, specifically, for example, 2, 3, 4, 5, and 6 stages, and may be in the range between any two of the numerical values ​​exemplified here.

[0035] <Summary> As described above, the system 1 of this embodiment is a system in which the capture unit 5 is incorporated into a CAES or LAES configured to compress and store a source gas using electric power and expand the stored compressed gas G or liquefied gas L to generate electric power. Most of the energy required to operate the system 1 is what was originally required by the CAES or LAES, and the additional energy required to capture CO2 is very small. Therefore, according to this embodiment, it is possible to capture CO2 with very little energy.

[0036] In addition, by attaching inverters to the above-mentioned compressors and turbines and linking them to grid frequency adjustment, it will be possible to sell electricity not only in the capacity market but also in the supply and demand adjustment market.

[0037] 2. Second embodiment A CO2 capture system 1 according to a second embodiment of the present invention will be described with reference to FIG. 2. This embodiment is similar to the first embodiment, and the description of the first embodiment can be applied to this embodiment as well, provided that it does not contradict the spirit of the first embodiment. This embodiment is mainly different from the first embodiment in the configuration of the capture unit 5, etc. The following description will focus on the differences.

[0038] In this embodiment, the immobilizing material 5a is an amine-containing liquid, and the immobilizing material 5a is heated by an indirect heating method. The recovery section 5 includes an absorption section 5C and a regeneration section 5D. The amine-containing liquid circulates between the absorption section 5C and the regeneration section 5D, absorbs CO2 in the absorption section 5C, and desorbs CO2 in the regeneration section 5D. The compressed gas G1 is supplied to the absorption section 5C, and the compressed gas G2 generated by removing CO2 in the absorption section 5C is discharged from the absorption section 5C. The first heating section 6b1 of the heat exchanger 6 heats the condensed water to generate steam, and supplies the steam to the reboiler 5D1 arranged in the regeneration section 5D. In the reboiler 5D1, the steam supplies thermal energy to the amine-containing liquid that has absorbed CO2, and at least a part of the steam becomes condensed water. The condensed water is sent to the first heating section 6b1 again.

[0039] The amine-containing liquid to which thermal energy has been supplied is regenerated by desorbing CO2. The regenerated amine-containing liquid is sent to the absorption section 5C. During regeneration, not only CO2 but also water vapor and evaporated amine are released from the amine-containing liquid. Therefore, a mixed gas of CO2, water vapor, and amine is discharged from the regeneration section 5D. The mixed gas is cooled by the cooler 10 and then sent to the gas-liquid separator 11. At least a part of the water vapor and evaporated amine contained in the mixed gas is liquefied by the cooling in the cooler 10. The condensed water and the amine in liquid form are taken out by the gas-liquid separator 11 and sent to the capture section 5 (preferably the regeneration section 5D). The CO2 discharged from the gas-liquid separator 11 is compressed by the CO2 compression section 7 and stored in the CO2 storage section 8.

[0040] 3. Energy calculation example The technology to capture CO2 in the air is generally called Direct Air Capture (DAC). Compared to implementing DAC alone, when DAC is used in combination with CAES as in the above embodiment, the following two main effects can be expected: -Reduction in the power required for blowing air into the CO2 capture equipment - Reduction of CO2 desorption energy in CO2 capture equipment

[0041] (1) Reduction in the power required for blowing air into the CO2 capture equipment - Blower power when using DAC alone Generally, DAC requires a blower to boost the pressure by the amount of pressure loss in the CO2 capture equipment used. The pressure loss varies depending on the CO2 capture equipment used, but it is about 1 to 5 kPa (Reference material 1: "Proposal for policy planning to realize a low-carbon society: Cost and evaluation of the Direct Air Capture (DAC) method for CO2 (Vol. 2) March 2021").

[0042] Table 1 shows the results of a simulation conducted using Aspen Plus under the conditions that the air is pressurized by 1 kPa using a blower with an isentropic efficiency of 85% and a mechanical efficiency of 90%, and 100% of the CO2 is captured by the CO2 separation and capture equipment. The electricity cost in Table 1 is the value given in Reference Material 1 above. As shown in Table 1, the blower power required per ton of CO2 is estimated to be 491 kW / t-CO2.

[0043] [Table 1]

[0044] -Reduction in fan power when CAES and DAC are combined When using DAC alone, a CO2 separation and capture facility with a pressure drop of 1 kPa would be, for example, an adsorption tank with a solid absorbent as shown in Table 2. The pressure drop was calculated using the Ergun equation shown below.

[0045] If the exact same CO2 separation and capture equipment could be used for CAES+DAC facilities, it is expected that the pressure loss would be extremely small, at around 0.012 kPa, due to a significant reduction in superficial velocity. As a result, compared to DAC alone, the combination of CAES and DAC can reduce the fan power required per 1 ton of CO2 by 491 kW / t-CO2 with almost no energy loss.

[0046]

number

[0047] [Table 2]

[0048] Naturally, when CAES and DAC are combined, there is no need for a blower, so the equipment costs for the blower itself can be completely eliminated. For example, in a CO2 capture facility with a pressure loss of approximately 1 kPa and a CO2 capture rate of 112 t / h (896 kt / y), the number of blowers required and their costs are estimated to be as follows (Reference Material 1).

[0049] [Table 3]

[0050] (2) Reduction of CO2 desorption energy in CO2 capture equipment The lower the concentration of CO2, the greater the energy required to separate and capture it. The cost has been estimated by various organizations, but it is approximately $150-350 / t-CO2 for DAC (CO2 concentration 0.04%) (Reference 2: KEARNEY, 2021, Carbon Capture Utilization and Storage).

[0051] Basically, the partial pressure of CO2 has a significant impact on the reaction of the absorption solution and absorbent that separates and captures CO2. (CO2 partial pressure) = (total pressure) * (CO2 concentration)

[0052] Therefore, while increasing the total pressure is an effective means of increasing the efficiency of CO2 separation and capture from low-concentration CO2 gas, as shown in Table 4, if the pressure were to be increased to 81 bar, it would require an enormous amount of power in the compressor, making this an unrealistic method. Table 4 also shows the results of a simulation performed using Aspen Plus under the conditions shown in Table 1, where the air sent in under the conditions shown in Table 1 is compressed to the same level as CAES (81 MPa) using four compressor stages. The electricity costs in Table 4 are the values ​​given in Reference Material 1 above.

[0053] [Table 4]

[0054] However, CAES, which stores energy as compressed air in the first place, requires the production of extremely high-pressure air (40-100 bar), which results in an increase in the partial pressure of CO2. It is expected that the cost of CO2 capture will approach the cost of Power Generation (approximately 4%) in Reference Material 2 above: approximately $50-100 / tCO2.

[0055] However, the cost estimates in Reference Material 2 are for cases where the number of operating days per year is more than a certain number (for example, 8,000 h / yr). On the other hand, in the case of CAES+DAC, CAES only operates when there is an energy surplus, so compared to normal DAC, the operating rate is lower and the amount of CO2 captured is smaller, so the proportion of capital investment in the CO2 capture cost may be larger.

[0056] In this invention, we are considering using the thermal energy stored during the production of compressed air by CAES in a CO2 separation and capture facility. Here, the results of a simulation using Aspen Plus under the condition of pressurizing the atmosphere to 81 barA are shown in Table 5.

[0057] In the case of CO2 regeneration energy: 95kJ / mol-CO2, the thermal energy required for CO2 separation and capture is 1.1kWh, while the thermal storage energy is 424kWh, which is only about 0.3%. Therefore, it is considered that there is almost no impact on CAES even if the thermal storage energy is used for CO2 separation and capture.

[0058] [Table 5] [Explanation of symbols]

[0059] 1:CO2 capture system 2: Compression section 2a: Motor 3: Storage section 4: Expansion section 4a: Generator 5: Collection section 5A: First recovery section 5B: Second collection section 5C: Absorption section 5D: Playback section 5D1: Reboiler 5a: Immobilization material 6: Heat exchanger 6a: Cooling section 6b: Heating part 6b1: 1st heating section 6b2: 2nd heating section 7: CO2 compression section 8: CO2 storage section 9: Vacuum pump 10:Cooler 11: Gas-liquid separator 12: Switching valve G: Compressed gas G1: Compressed gas G2: Compressed gas L: Liquefied gas

Claims

1. A CO refrigeration system including a compression section, a storage section, an expansion section, and a recovery section. ２ 1. A recovery system comprising: The compression section is ２ to compress a source gas comprising: The storage unit is configured to store the compressed gas as is or as a liquefied gas by liquefaction, The expansion section is configured to expand the compressed gas or the liquefied gas discharged from the storage section, The recovery section detects CO in the compressed gas. ２ The CO is fixed to the fixing material. ２ Collection system.

2. The CO according to claim 1 ２ 1. A recovery system comprising: Further comprising a heat exchanger; The heat exchange unit includes a cooling unit and a heating unit. The cooling unit is configured to cool the compressed gas generated in the compression unit to recover thermal energy, The heating unit is configured to heat the compressed gas or the liquefied gas discharged from the storage unit by using the thermal energy recovered by the cooling unit. ２ Collection system.

3. The CO according to claim 2 ２ 1. A recovery system comprising: The recovery unit heats the immobilization material using the thermal energy recovered by the cooling unit to extract CO from the immobilization material. ２ and regenerating the immobilized material by desorbing CO. ２ Collection system.

4. The CO according to claim 3 ２ 1. A recovery system comprising: The heating of the immobilization material is carried out by contacting the immobilization material with water vapor heated by the thermal energy. ２ Collection system.

5. The CO according to any one of claims 1 to 4. ２ 1. A recovery system comprising: The compression unit is configured to perform the compression using electric power, The expansion section is configured to rotate a turbine using a force generated during the expansion to generate electricity. ２ Collection system.

6. The CO according to any one of claims 1 to 4. ２ 1. A recovery system comprising: CO in the source gas ２ CO having a concentration of 0.01 to 0.1% by volume ２ Collection system.

7. The CO according to any one of claims 1 to 4. ２ 1. A recovery system comprising: The immobilizing material is a solid. ２ Collection system.

8. The CO according to claims 1 to 4 ２ 1. A recovery system comprising: The collection section includes a first collection section and a second collection section, the first and second recovery sections each include the immobilizing material, In the first operating state, the first recovery section performs fixed operation and the second recovery section performs regeneration operation; In the second operating state, the second recovery section performs fixed operation and the first recovery section performs regeneration operation; The first operating state and the second operating state are configured to be switchable, In the fixed operation, CO ２ is fixed to the fixing material, In the regeneration operation, the CO ２ Desorb CO ２ Collection system.

9. The CO according to any one of claims 1 to 4. ２ 1. A recovery system comprising: The immobilizing material is an amine-containing liquid, ２ Collection system.

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