Co2 recovery system

Abstract

Provided is a CO2 recovery system that can reduce the energy required to recover CO2.　The present invention provides a CO2 recovery system that comprises a compression unit, a retention unit, an expansion unit, and a recovery unit. The CO2 recovery system is configured such that the compression unit compresses a source gas that includes CO2 to generate a compressed gas, the retention unit retains the compressed gas as is or liquefies the compressed gas for retention as a liquefied gas, the expansion unit expands the compressed gas or the liquefied gas as discharged from the retention unit, and the recovery unit immobilizes the CO2 in the compressed gas at an immobilization material.

Description

CO2 capture system

[0001] The present invention uses CO contained in the source gas. ２ (carbon dioxide) capture CO ２ Regarding collection systems.

[0002] In Patent Document 1, CO contained in the air ２ A technology has been disclosed in which the above-mentioned substances are adsorbed onto an adsorption rotor and collected.

[0003] JP 2023-45570 A

[0004] The configuration of Patent Document 1 requires a blower to send a large amount of air to the adsorption rotor. The operation of the blower requires a huge amount of energy, which is a problem. ２ There is a need to reduce the energy required to recover this.

[0005] The present invention has been made in view of the above circumstances, and ２ CO that can reduce the energy required for recovery ２ It provides a collection system.

[0006] According to the present invention, the following inventions are provided: [1] A CO refrigerant storage system including a compression section, a storage section, an expansion section, and a recovery section. ２ a recovery system, wherein the compression section ２ The storage unit is configured to store the compressed gas as it 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 recovery unit is configured to recover CO ２ configured to fix CO to the immobilization material, ２ [2] The CO recovery system according to [1]. ２A CO recovery system 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 by the cooling unit. ２ [3] The CO recovery system according to [2]. ２ In the recovery system, the recovery unit heats the immobilization material using the thermal energy recovered by the cooling unit to remove CO from the immobilization material. ２ and regenerating the immobilized material by desorbing CO. ２ [4] The CO recovery system according to [3]. ２ a CO recovery system, wherein the heating of the immobilization material is carried out by bringing water vapor heated using the thermal energy into contact with the immobilization material; ２ [5] A CO recovery system according to any one of [1] to [4]. ２ A CO recovery system, wherein the compression unit is configured to perform the compression using electric power, and the expansion unit is configured to rotate a turbine using a force generated during the expansion to generate electricity. ２ [6] A CO recovery system according to any one of [1] to [5]. ２ a recovery system for recovering CO in the source gas; ２ CO having a concentration of 0.01 to 0.1% by volume ２ [7] A CO recovery system according to any one of [1] to [6]. ２ A CO recovery system, wherein the immobilization material is a solid. ２ [8] A CO recovery system according to any one of [1] to [7]. ２ a recovery system, the recovery unit including a first recovery unit and a second recovery unit, each of the first and second recovery units including the immobilizing material; a first operating state in which the first recovery unit performs a fixed operation and the second recovery unit performs a regeneration operation; and a second operating state in which the second recovery unit performs a fixed operation and the first recovery unit performs a regeneration operation; the first operating state and the second operating state are switchable; and in the fixed operation, ２is fixed in the fixing material, and in the regeneration operation, ２ CO ２ [9] A CO recovery system according to any one of [1] to [6]. ２ A CO recovery system, wherein the immobilizing material is an amine solution. ２ Collection system.

[0007] The CO of the present invention ２ In the recovery system, the source gas is compressed and stored as compressed or liquefied gas, and the CO is transferred to a compressed air storage system (also known as "CAES") or liquefied air energy storage (also known as "LAES"), which is used to generate electricity when needed. ２ The energy required for compressing the source gas is what is originally required in a CAES or LAES, and the additional energy required by incorporating a recovery section into such a system is very small. Therefore, by incorporating a recovery section into a CAES or LAES, it is possible to recover CO 2 with almost no additional energy required. ２ Therefore, according to the present invention, CO ２ This reduces the energy required for recovery.

[0008] CO of the first embodiment of the present invention ２ FIG. 1 is a diagram showing the configuration of a recovery system 1 according to a second embodiment of the present invention. ２ FIG. 1 is a diagram showing the configuration of a collection system 1.

[0009] The following describes embodiments of the present invention. The various features shown in the following embodiments can be combined with each other. Furthermore, each feature can be an independent invention.

[0010] 1. First Embodiment Referring to FIG. 1, the CO ２ The CO recovery system 1 of this embodiment will be described. ２ The recovery system 1 includes a compression section 2, a storage section 3, an expansion section 4, and a recovery 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 section 2 is ２ The compressed gas G1 is configured to compress a source gas containing CO ２ It also refers to compressed gas before CO is removed. ２ The compressed gas after removing CO is called "compressed gas G2". ２ When there is no distinction as to whether or not CO has been removed, the gas is referred to as "compressed gas G." The source gas may be the atmosphere or exhaust gas generated at a power plant or the like. ２ The concentration is not particularly limited, but the present invention is ２ Even at low concentrations, CO ２ Therefore, the CO ２ When the concentration is low (for example, when the source gas is the atmosphere), the technical significance of applying the present invention is significant.

[0012] In addition, CO in the source gas ２ If the concentration is high, the CO ２ Therefore, the fixation rate of CO in the source gas becomes high, and the frequency of the regeneration operation of the fixation material 5a must be increased. ２ It is preferable that the concentration is not too high. ２ The concentration 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. Specific examples of the concentration include 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 1, 5, 10, 15, and 20% by volume, and may be within a 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, by 20 to 200 times, preferably by 40 to 100 times. The pressure of the compressed gas G1 is, for example, 20 to 200 barA, and preferably 40 to 100 barA. Specific examples of this pressure include 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, and 200 barA, and may be in a range between any two of the values ​​exemplified here.

[0014] The power for driving the motor 2a is preferably derived from natural energy sources such as solar power and wind power. Since it is not easy to adjust the amount of power generated from natural energy sources, there is a possibility that more power than necessary will be 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 be 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 using thermal energy recovered in the cooling section 6a.

[0017] The cooling section 6a is preferably located downstream of the compression section 2. The source gas is heated during compression, resulting in a high temperature of the compressed gas G1. Contacting the source gas G1 with the immobilizing material 5a while the temperature is high can cause problems such as damage to the immobilizing material 5a. Therefore, it is preferable to cool the compressed gas G1 in the cooling section 6a to a temperature suitable for contacting the immobilizing material 5a, and recover the thermal energy during this process. For convenience of illustration, the compression section 2 and the cooling section 6a are shown in a single stage in FIG. 1 . However, it is preferable to configure the compression section 2 and the cooling section 6a in multiple stages, i.e., to alternately arrange the compression sections 2 and the cooling sections 6a in multiple stages to repeatedly perform compression and cooling. In this case, the source gas can be prevented from becoming too hot due to compression. The number of stages for the compression section 2 and the cooling section 6a is preferably, for example, 2 to 6, specifically, 2, 3, 4, 5, or 6, or may be between any two of the values ​​exemplified herein. The temperature of the compressed gas G1 after cooling is, for example, 20 to 80°C, preferably 30 to 70°C, and specifically, for example, 20, 30, 40, 50, 60, 70, or 80°C, and may be in a range between any two of the 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 steam. The second heating unit 6b2 is configured to heat the compressed gas G or liquefied gas L discharged from the storage unit 3.

[0019] <Recovery section 5> The recovery section 5 recovers CO ２ The recovery section 5 is configured to fix the CO contained in the compressed gas G1 to the immobilizing material 5a. The immobilizing material 5a is arranged in the recovery section 5, and the compressed gas G2 is discharged from the recovery section 5 after the compressed gas G1 is supplied into the recovery section 5 and brought into contact with the immobilizing material 5a. ２ can be fixed to the fixing material 5a and removed.

[0020] The compressed gas G1 has a lower CO ２ Because the partial pressure is increased, CO ２ In addition, CO of the source gas can be efficiently immobilized on the immobilizing material 5a.２ At very low partial pressures, there are few immobilization options available, but compressing the source gas to CO ２ Increasing the partial pressure increases the options for available immobilization materials, which is expected to reduce costs.

[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 amine-supported solid absorbents, zeolites, metal-organic frameworks, and ion exchange resins. The amine-supported solid absorbents are composed of an amine supported on the surface of a carrier. The carrier is preferably an inorganic oxide such as silica. The metal-organic framework is a crystalline porous material composed 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 composed solely of amine, or an amine solution in which amine is dissolved in a solvent (e.g., water). The amine content 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, or may be within a range between any two of the values ​​exemplified here.

[0022] CO in compressed gas G1 ２ As the CO 2 is immobilized in the immobilization material 5a, the amount of CO 2 immobilized in the immobilization material 5a increases. ２ The amount of CO ２ Therefore, the function of immobilizing CO from the immobilizing material 5a is reduced. ２ It is preferable to regenerate the immobilizing material 5a by performing a regeneration operation in which the CO desorbed from the immobilizing material 5a is desorbed. ２ is CO ２ Compressed in the compression section 7 ２ It is stored in the storage section 8. ２ CO stored in storage section 8 ２ is CO ２ It can be used as a source of natural gas, or it can be injected into reservoirs located deep underground (for example, more than 800 meters underground) for long-term storage.

[0023] CO from immobilization material 5a ２The desorption of CO can be achieved 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 CO 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. ２ In addition, when the immobilizing material 5a is an amine-containing liquid, the amine-containing liquid can be heated in a reboiler to desorb CO ２ In addition, when the immobilizing material 5a is in a normal dry state, CO ２ and CO ２ In the case where the immobilizing material 5a is an ion exchange resin having the property of desorbing CO, the immobilizing material 5a can be desorbed by humidifying the surroundings of the immobilizing material 5a. ２ can be released.

[0024] When the immobilizing material 5a is regenerated by heating, it is preferable to heat the immobilizing material 5a using the thermal energy recovered in the cooling section 6a. In this case, the external supply of energy required for regenerating the immobilizing material 5a can be reduced or eliminated. For example, when the source gas is air at 25°C and this is compressed 80 times to generate compressed gas, CO ２ The thermal energy required for desorption of CO is 1% or less of the thermal energy that can be recovered during compression of the source gas, so the immobilizing material 5a can be regenerated without supplying thermal energy from an external source. ２ When using a source gas with a high concentration, CO ２ In some cases, the thermal energy required for desorption of the immobilizing material 5a exceeds the thermal energy that can be recovered during compression of the source gas. In this case, the immobilizing material 5a can be regenerated by supplying the shortfall in thermal energy from an external source.

[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, thereby transferring thermal energy from the heating medium to the immobilizing material 5a and heating the immobilizing material 5a. In the indirect heating method, thermal energy from the heated heating medium (e.g., steam) is transferred to the immobilizing material 5a by heat exchange, thereby heating 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, thereby preventing deterioration or inactivation of the immobilizing material 5a due to contact with the heating medium. 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, condensed water is heated in the first heating section 6b1 of the heat exchanger 6 to generate steam, and this steam is brought into contact with the immobilizing material 5a to heat the immobilizing material 5a and dissolve the CO2 immobilized in the immobilizing material 5a. ２ In addition, if the thermal energy of the water vapor is insufficient when heated by the first heating section 6b1, a heater may be separately disposed between the first heating section 6b1 and the recovery section 5.

[0027] The piping on the output side of the recovery unit 5 includes a vacuum pump 9, a cooler 10, a gas-liquid separator 11, a CO ２ Compression section 7, CO ２ The reservoir 8 is connected in this order. The vacuum pump 9 is configured to be able to reduce the pressure inside the recovery unit 5. This allows water vapor and CO ２ The mixed gas of CO2 and CO2 can be sucked out by reducing the pressure inside 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 steam generated in the first heating section 6b1 can be lowered. By lowering the temperature of the steam, the deterioration and / or inactivation of the immobilizing material 5a can be suppressed. In addition, by combining the heating of the immobilizing material 5a and the pressure reduction around it, the CO2 from the immobilizing material 5a can be reduced. ２ The vacuum pump 9 can be omitted if not required.

[0028] The mixed gas sucked out by the vacuum pump 9 is cooled in the cooler 10 and then sent to the gas-liquid separator 11. By cooling in the cooler 10, at least a portion of the water vapor contained in the mixed gas is liquefied 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 supply can be reduced. CO2 discharged from the gas-liquid separator 11 ２ is CO ２ Compressed in the compression section 7 ２ It is stored in the storage section 8.

[0029] The capture unit 5 preferably operates by switching between fixed operation and regeneration operation. In the fixed operation, the compressed gas G1 is brought into contact with the immobilization material 5a to extract CO ２ On the other hand, in the regeneration operation, CO is fixed in the fixing material 5a. ２ 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 fixed operation while the motor 2a is operating and perform regeneration operation while the motor 2a is stopped. The regeneration operation may be performed periodically, and the CO ２ This may be done when a decrease in the immobilization rate is detected.

[0030] When the motor 2a is operated continuously, the recovery unit 5 must always be in fixed operation, and it is not easy to regenerate the recovery unit 5. In this embodiment, to solve this problem, the recovery unit 5 is configured to include first and second recovery units 5A and 5B. The first and second recovery units 5A and 5B each include an immobilizing material 5a, and both the first and second recovery units 5A and 5B can similarly recover CO ２In the first operating state, fixed operation is performed in the first recovery unit 5A and regeneration operation is performed in the second recovery unit 5B, while in the second operating state, fixed operation is performed in the second recovery unit 5B and regeneration operation is performed in the first recovery unit 5A. The first operating state and the second operating state are switchable. This switching can be achieved by operating the switching valves 12 provided on the input and output piping of the first and second recovery units 5A and 5B to switch the piping connections. With this configuration, while regeneration operation is being performed in one of the first and second recovery units 5A and 5B, fixed operation can be performed in the other of the first and second recovery units 5A and 5B. Therefore, regeneration operation can be performed without completely stopping fixed operation. This configuration is particularly useful when the immobilizing material 5a is solid.

[0031] <Storage section 3> The storage section 3 is configured to store the compressed gas G compressed in the compression section 2 either as is or after liquefaction to form a liquefied gas L. When the compressed gas G is to be liquefied, it is preferable to provide a liquefaction device that liquefies the compressed gas G upstream of the storage section 3. The liquefaction device may recover heat generated during liquefaction. In this embodiment, the recovery section 5 is disposed between the compression section 2 and the storage section 3, and the CO ２ The compressed gas G2 from which CO2 has been removed is stored in the storage section 3 as it is or after being liquefied. In another embodiment, the recovery section 5 is disposed between the storage section 3 and the expansion section 4, and the storage section 3 contains CO2. ２ In the latter case, the compressed gas G1 or the liquefied gas L extracted from the storage unit 3 may be stored as it is or liquefied. ２ When the liquefied gas L is extracted from the storage unit 3, it is heated to return it to a compressed gas, and then CO is removed at a point before generating electricity in the turbine. ２ 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 inflation gas by expanding the compressed gas G or liquefied gas L discharged from the storage section 3. It is preferable to arrange a 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, generating electricity.

[0034] For convenience of illustration in FIG. 1, the second heating section 6b2 and the expansion section 4 are configured in a single stage, but it is preferable that the second heating section 6b2 and the expansion section 4 be 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, 2, 3, 4, 5, or 6 stages, and may be in a 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 recovery 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 originally required by the CAES or LAES, and CO ２ Therefore, according to this embodiment, CO can be recovered with very little energy. ２ It will be possible to recover the

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

[0037] 2. Second embodiment Referring to FIG. 2, the CO２ A collection system 1 will be described. This embodiment is similar to the first embodiment, and the description of the first embodiment can also be applied to this embodiment as long as it does not contradict the spirit of the first embodiment. This embodiment differs from the first embodiment mainly in the configuration of the collection 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 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, and CO ２ and CO ２ The compressed gas G1 is supplied to the absorption section 5C, and CO ２ The compressed gas G2 generated by removing the CO 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 disposed in the regeneration section 5D. In the reboiler 5D1, the steam is ２ Heat energy is supplied to the amine-containing liquid that has absorbed the amine, and at least a portion of the amine-containing liquid becomes condensed water. The condensed water is sent again to the first heating section 6b1.

[0039] The amine-containing liquid to which thermal energy has been supplied is ２ 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, CO2 is released from the regeneration section 5D. ２ A mixed gas of water vapor and amine is discharged. The mixed gas is cooled in a cooler 10 and then sent to a gas-liquid separator 11. At least a portion 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 liquid amine are extracted by the gas-liquid separator 11 and sent to the recovery section 5 (preferably the regeneration section 5D). The CO discharged from the gas-liquid separator 11 ２ is CO ２ Compressed in the compression section 7 ２ It is stored in the storage section 8.

[0040] 3. Energy calculation example: CO in the air ２The technology for capturing CO is generally called Direct Air Capture (abbreviated as DAC). When DAC is used in combination with CAES as in the above embodiment, the following two main effects can be expected compared to when DAC is used alone. ２ Reduced power consumption of the blower to ventilate the separation and recovery equipment. ２ CO in separation and recovery equipment ２ Reduction of desorption energy

[0041] (1) CO ２ Reduction of the power required for the fan to ventilate the separation and recovery equipment. - Power required for the fan when using DAC alone. Generally, DAC uses ２ It is necessary to increase the pressure by a blower to compensate for the pressure loss in the separation and recovery equipment. ２ The pressure loss varies depending on the separation and recovery equipment, but it is about 1 to 5 kPa (Reference 1: "Proposal for Policy Planning to Realize a Low-Carbon Society, CO ２ Cost and Evaluation of the Direct Air Capture (DAC) Method (Vol. 2) March 2021).

[0042] Using a blower with an isentropic efficiency of 85% and a mechanical efficiency of 90%, the air was pressurized to 1 kPa and CO ２ 100% CO with separation and recovery equipment ２ The results of a simulation using Aspen Plus under the condition that CO is recovered are shown in Table 1. The unit price of electricity in Table 1 is the value given in Reference Material 1 above. As shown in Table 1, ２ - The required fan power per ton is 491 kW / t-CO ２ It is estimated that:

[0043]

[0044] ・Reduction in blower power when combining CAES and DAC When using DAC alone, the CO ２ The separation and recovery equipment is, for example, an adsorption tank with a solid absorbent material as shown in Table 2. The pressure loss was calculated using the Ergun formula shown below.

[0045] If the same CO ２ If separation and recovery equipment can be used, the superficial velocity is expected to be significantly reduced, resulting in a very small pressure loss of approximately 0.012 kPa. As a result, compared to the case of using DAC alone, the combination of CAES and DAC allows for CO2 to be separated with almost no energy loss. ２ - 491kW / t-CO, the required fan power per ton ２ can be reduced.

[0046]

[0047]

[0048] Naturally, when CAES and DAC are combined, there is no need to have a blower, so the cost of the blower itself can be reduced. For example, pressure loss: about 1 kPa, CO ２ Capture amount: 112 t / h (896 kt / y) of CO ２ The number of fans required and their costs for the recovery facility are estimated as follows (Reference 1).

[0049]

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

[0051] Basically, CO ２ The absorbent that separates and recovers CO ２ The partial pressure has a large effect. ２ (Partial pressure) = (Total pressure) * (CO ２ concentration)

[0052] Therefore, low concentration CO２ CO from gas ２ Increasing the total pressure is an effective way to improve the efficiency of separation and recovery, but as shown in Table 4, if the pressure were to be increased to 81 bar, the compressor would require an enormous amount of power, making this an unrealistic method. Table 4 also shows the results of a simulation performed using Aspen Plus under the condition that air fed under the conditions shown in Table 1 is compressed to the same level as CAES (81 MPa) using four compressor stages. The electricity unit prices in Table 4 are the values ​​listed in Reference Material 1 above.

[0053]

[0054] However, CAES, which stores energy as compressed air, requires the production of very high-pressure air (40-100 bar), resulting in CO ２ Partial pressure rises, and CO ２ The recovery cost is Power Generation (approximately 4%) in Reference Material 2 above: approximately $50-100 / t-CO ２ It is expected to approach

[0055] However, the cost estimates in Reference Material 2 are for a certain number of operating days per year (for example, 8,000 h / yr). On the other hand, in the case of CAES + DAC, the CAES operates only when there is an energy surplus, so the operating rate is lower than that of a normal DAC, and the amount of CO captured is ２ Because the amount is small, CO ２ The proportion of capital investment in recovery costs may become large.

[0056] In the present invention, the thermal energy stored during the production of compressed air in the CAES is converted into CO ２ We are considering using this in separation and recovery equipment. Table 5 shows the results of a simulation using Aspen Plus under the condition that the atmospheric pressure is increased to 81 barA.

[0057] CO ２ Renewable energy: 95 kJ / mol-CO ２ In this case, CO ２The thermal energy required for separation and recovery is 1.1 kWh, but the thermal energy stored is 424 kWh, which is only equivalent to about 0.3%. ２ Even if it is used for separation and recovery, it is believed that there will be almost no impact on CAES.

[0058]

[0059] 1:CO ２ Recovery system, 2: compression section, 2a: motor, 3: storage section, 4: expansion section, 4a: generator, 5: recovery section, 5A: first recovery section, 5B: second recovery section, 5C: absorption section, 5D: regeneration section, 5D1: reboiler, 5a: immobilization material, 6: heat exchanger, 6a: cooling section, 6b: heating section, 6b1: first heating section, 6b2: second heating section, 7: CO ２ Compression section, 8: CO ２ 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 having a compression section, a storage section, an expansion section, and a recovery section. ２ A recovery system, ２ The storage unit is configured to store the compressed gas as it 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 recovery unit is configured to recover the CO ２ The CO is fixed to the fixing material. ２ Collection system.

2. The CO according to claim 1 ２ A CO recovery system 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 by using the thermal energy recovered by the cooling unit. ２ Collection system.

3. The CO according to claim 2 ２ A recovery system, wherein the recovery unit heats the immobilization material using the thermal energy recovered by the cooling unit to recover 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 A CO recovery system, wherein the heating of the immobilization material is performed 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 A CO recovery system, comprising: the compression unit configured to perform the compression using electric power; and the expansion unit configured to rotate a turbine using a force generated during the expansion to generate electric power. ２ Collection system.

6. The CO according to any one of claims 1 to 4. ２ A recovery system for 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 A CO capture system, wherein the immobilization material is a solid. ２ Collection system.

8. The CO according to claims 1 to 4 ２ A recovery system, wherein the recovery section includes a first recovery section and a second recovery section, each of the first and second recovery sections includes the immobilizing material, in a first operating state, a fixed operation is performed in the first recovery section and a regeneration operation is performed in the second recovery section, in a second operating state, a fixed operation is performed in the second recovery section and a regeneration operation is performed in the first recovery section, and the first operating state and the second operating state are configured to be switchable, and in the fixed operation, ２ is fixed in the fixing material, and in the regeneration operation, the CO is removed from the fixing material. ２ Desorb CO ２ Collection system.

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

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