Method for co2 recovery

Abstract

The present disclosure provides a CO2 recovery method. The CO2 recovery method is a method in which adsorption and desorption of CO2 are alternately repeated, in which CO2 contained in a supplied gas is adsorbed on a CO2 adsorption body, and CO2 adsorbed on the CO2 adsorption body is desorbed from the CO2 adsorption body by adjusting the CO2 adsorption body to a higher temperature than at the time of adsorption of CO2 and is recovered, wherein, when the shortest time in which the adsorption rate of CO2 with respect to the CO2 adsorption body becomes 80% or more by volume is set to t1, and the time of one cycle consisting of the adsorption and desorption of CO2 is set to t2, t1 < t2 < 4 x t1 is satisfied.

Description

Technical Field

[0001] This disclosure relates to a method for CO2 recovery. Background Technology

[0002] Currently, efforts are underway to develop CO2 recovery methods that recover CO2 (carbon dioxide) from the atmosphere. For example, a known method involves passing air directly through an air recovery device at room temperature to adsorb CO2, and then heating the device to approximately 100°C to remove the CO2, thereby recovering the CO2 (Japanese Patent Application Laid-Open No. 2024-154557). Summary of the Invention

[0003] However, the method disclosed in Japanese Patent Application Publication No. 2024-154557 has a high cost for recovering CO2 from the atmosphere, and therefore improvement in cost is desired.

[0004] This disclosure was made in view of the above background, and its purpose is to provide a CO2 recovery method that can recover CO2 in a low-cost and efficient manner.

[0005] The CO2 recovery method disclosed herein is a method of alternating and repeatedly performing CO2 adsorption and desorption. In the CO2 adsorption and desorption, CO2 contained in the supplied gas is adsorbed onto a CO2 adsorbent, and by adjusting the CO2 adsorbent to a higher temperature than that during CO2 adsorption, the CO2 adsorbed on the CO2 adsorbent is desorbed from the CO2 adsorbent and recovered. When the shortest time for the adsorption rate of CO2 relative to the CO2 adsorbent to reach 80% or more is set as t1, and the time for one cycle consisting of CO2 adsorption and desorption is set as t2, t1 < t2 < 4 × t1 is satisfied.

[0006] As described above, the CO2 recovery method disclosed herein recovers CO2 in a shorter cycle time compared to conventional CO2 recovery methods that maximize the adsorption capacity of the CO2 adsorbent by setting the adsorption rate of CO2 relative to the CO2 adsorbent to 100% by volume. Thus, in the method disclosed herein, which performs CO2 recovery in a shorter cycle time than conventional methods, if the CO2 recovery amount and various costs involved in CO2 recovery are comprehensively considered, the CO2 recovery cost can be reduced compared to conventional recovery methods, thereby enabling efficient CO2 recovery.

[0007] The CO2 adsorbent may also comprise a CO2 adsorbent and a plurality of porous supports on which the CO2 adsorbent is loaded, and the CO2 adsorbent comprises polyethyleneimine having isopropyl groups.

[0008] The porous carrier can also have a honeycomb structure.

[0009] The gas supply rate to the CO2 adsorbent can also be 11 m / s or higher.

[0010] The porous carrier can also be coated with silica gel, and the thickness of the silica gel is less than 250 μm.

[0011] According to this disclosure, a CO2 recovery method that can recover CO2 at low cost and high efficiency can be provided. Attached Figure Description

[0012] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, wherein like symbols denote like elements, and wherein: Figure 1 This diagram illustrates a structural example of a CO2 recovery apparatus that can be used in the CO2 recovery method disclosed herein.

[0013] Figure 2 This diagram illustrates the operation of the CO2 recovery device in the CO2 recovery method disclosed herein.

[0014] Figure 3 A graph illustrating an example of the relationship between the adsorption rate of a CO2 adsorbent and the thickness of the silica gel coating on a porous support.

[0015] Figure 4 A graph illustrating the relationship between cycle time and cost in the CO2 recovery method disclosed herein. Detailed Implementation

[0016] The present invention will now be described through embodiments thereof, but this is not intended to limit the invention to the embodiments described in the claims. Furthermore, not all structures described in the embodiments are necessarily necessary as means of solving the problem. For clarity, the following description and drawings have been appropriately omitted and simplified.

[0017] The CO2 recovery method disclosed herein (hereinafter also referred to as "this method") adsorbs CO2 contained in a gas supplied from the outside onto a CO2 adsorbent. Furthermore, the adsorption and detachment of CO2 are performed alternately and repeatedly by adjusting the adsorbent to a temperature higher than that during CO2 adsorption, thereby detaching the CO2 adsorbed on the adsorbent. When the shortest time for achieving an adsorption rate of 80% or more of CO2 relative to the CO2 adsorbent is defined as t1, and the time for one cycle consisting of the adsorption and detachment of CO2 is defined as t2, a specific relationship is satisfied, namely, Equation 1: t1 < t2 < 4 × t1. By ensuring that one cycle time t2 satisfies this relationship (Equation 1), costs such as electricity expenses can be further suppressed. Figure 1 An example structure of a CO2 recovery apparatus that can be used in the CO2 recovery method disclosed herein is shown. Furthermore, Figure 2 A diagram is shown to illustrate the operation of the CO2 recovery device.

[0018] Figure 1 The CO2 recovery device shown is a device that recovers CO2 by alternately and repeatedly performing CO2 adsorption and CO2 desorption processes. This CO2 recovery device includes a blower 1, a first valve 2, a desorption gas supplier 3, an adsorber 4 equipped with a heating / cooling mechanism, a vacuum pump 5, and a second valve 6.

[0019] More specifically, such as Figure 2 As shown, after the ventilator 1 is set to start (on), the gas (exhaust gas, atmosphere) supplied from the outside before CO2 recovery is sent into the adsorber 4 equipped with a heating / cooling mechanism via the opened first valve 2. In addition, the gas can be exhaust gas from factories or power plants with relatively high CO2 concentration, or it can be atmosphere with relatively low CO2 concentration.

[0020] Then, the CO2 (carbon dioxide) contained in the gas is adsorbed onto the CO2 adsorbent in the adsorber 4 at room temperature (e.g., 25°C). The gas after CO2 recovery, with a portion of the CO2 recovered by the CO2 adsorbent, is discharged to the outside through the opened second valve 6.

[0021] Then, in this manner, after an adsorption process of, for example, less than 5 minutes, a CO2 removal process is performed. Specifically, firstly, the adsorber 4 is evacuated using the vacuum pump 5, and oxygen purging and heating by the heating mechanism are performed. As a result, the temperature of the adsorber 4 (CO2 adsorbent) is adjusted to a higher temperature (gas removal temperature) compared to the CO2 adsorption process. Furthermore, in the CO2 removal process, the adsorber 4 can also be adjusted to a lower pressure or a lower CO2 partial pressure by allowing the flow of gases such as water vapor. As a result, the CO2 adsorbed on the CO2 adsorbent begins to be removed. At this time, with the removal gas supply 3 and the vacuum pump 5 in an on state, the CO2 adsorbed on the CO2 adsorbent is removed from the CO2 adsorbent and recovered. Then, while continuing the CO2 recovery process, the adsorber 4 is cooled using a cooling mechanism to allow the gas before CO2 recovery to be adsorbed back into the adsorber 4, thereby continuing the CO2 recovery process.

[0022] Furthermore, the CO2 recovery device can also be configured with multiple units, where the blower 1, the detached gas supply 3, and the vacuum pump 5 are shared, and each has multiple first valves 2, adsorbers 4, and second valves 6. In such a CO2 recovery device, since the blower 1, the detached gas supply 3, and the vacuum pump 5 are shared, it is preferable to have units consisting of first valves 2, adsorbers 4, and second valves 6. Figure 2 The actions shown are controlled in a non-repetitive manner.

[0023] In addition, the CO2 recovery device may also have a temperature regulator for regulating the temperature of the adsorber 4, a pressure regulator for regulating the pressure of the adsorber 4, and a humidity regulator for regulating the humidity of the adsorber 4.

[0024] Furthermore, the CO2 recovery device may also have a control unit that controls the alternating and repeated CO2 adsorption and CO2 removal processes. In addition, the control unit can also set the respective processing conditions (temperature, pressure, humidity, etc.) for CO2 adsorption and CO2 removal processes.

[0025] In addition, this method can be configured to perform short-term cycles at high speeds compared to conventional CO2 recovery methods, thus enabling the device to be miniaturized compared to conventional CO2 recovery devices.

[0026] Furthermore, this method allows for CO2 removal at lower temperatures (e.g., below 60°C) compared to conventional CO2 recovery methods. For example, by setting the removal temperature to 60°C within a 10-minute cycle of 5 minutes for adsorption and 5 minutes for removal, the same amount of CO2 recovered can be achieved as in cases where CO2 recovery is performed under conventional high-temperature conditions (e.g., above 80°C) for the same 10-minute cycle. Thus, lower costs can be further achieved through low-temperature removal and high-speed cycling.

[0027] This method repeatedly operates the CO2 recovery device by treating the four actions of adsorption, heating, desorption, and cooling in the adsorber as a cycle. This alternating cycle of CO2 adsorption (cooling and adsorption) and CO2 desorption (heating and desorption) allows for CO2 recovery. As described above, the operating time of the four actions is set such that the cycle time t2 is within the time frame of Equation 1: t1 < t2 < 4 × t1, where t1 is the time when the adsorption rate of CO2 relative to the CO2 adsorbent used reaches 80% by volume or more. While the operating time of each action is not specifically limited as long as Equation 1 is satisfied, for example, the CO2 adsorption (cooling and adsorption) time can be set to be greater than or equal to t1 / 2 and less than 2 × t1, and the CO2 desorption (heating and desorption) time can be set to be greater than or equal to t1 / 2 and less than 2 × t1.

[0028] The temperature during detachment can be appropriately set by heating, for example, it can be set to below 90°C, below 85°C, below 80°C, below 75°C, or below 70°C. In addition, the temperature during adsorption can be appropriately set by cooling, for example, it can be set to above 20°C, above 25°C, above 30°C, above 35°C, or above 40°C.

[0029] Here, t1 refers to the shortest time when the adsorption capacity of the adsorber 4 (more specifically, the CO2 adsorbent) reaches 80% or more, provided that the adsorption capacity of the adsorber 4 is set to 100% by volume, and the adsorption capacity is used to the maximum extent possible (e.g., more than 1 hour). In other words, t1 can be described as the adsorption time when the CO2 adsorption capacity of the adsorber 4 reaches 80% by volume.

[0030] While t1 can be appropriately set depending on the CO2 recovery device used (more specifically, the CO2 adsorbent used), it can be set to, for example, less than 5 minutes, less than 4 minutes and 30 seconds, less than 4 minutes, less than 3 minutes and 30 seconds, less than 3 minutes, less than 2 minutes and 30 seconds, or less than 2 minutes. By setting t1 to less than 5 minutes, cost reduction can be easily achieved.

[0031] Furthermore, while from a cost perspective, t1 is set as the shortest time when the adsorption rate of CO2 relative to the CO2 adsorbent used reaches 80% by volume or more, the CO2 adsorption rate at t1 can also be set to, for example, 75% by volume or more, 81% by volume or more, 82% by volume or more, 83% by volume or more, 84% by volume or more, or 85% by volume or more. However, from the viewpoint of minimizing costs, the CO2 adsorption rate at t1 is preferably set to 80% by volume or more.

[0032] t2 is the time of one cycle consisting of CO2 adsorption and desorption, and can be appropriately set according to the adsorber used, within the range of Equation 1 above. For example, t2 can be set to less than 60 minutes, less than 55 minutes, less than 50 minutes, less than 45 minutes, less than 40 minutes, less than 35 minutes, less than 30 minutes, less than 25 minutes, less than 20 minutes, or less than 20 minutes.

[0033] Furthermore, the lower limit of t2, within the range satisfying Equation 1 above, can be appropriately set according to the adsorber used. For example, it can be set to t2 ≥ 1.1 × t1, t2 ≥ 1.2 × t1, t2 ≥ 1.3 × t1, t2 ≥ 1.4 × t1, or t2 ≥ 1.5 × t1. By satisfying Equation 1 above, the lower limit of t2 can ensure sufficient CO2 removal and adsorption. For example, t2 can be set to 4 minutes or more, 4.5 minutes or more, or 5 minutes or more.

[0034] Furthermore, in this method, the gas supply rate from the outside to the adsorber 4 (CO2 adsorbent) is preferably 11 m / s or higher. In other words, the air velocity of the blower 1 in the CO2 recovery device is preferably 11 m / s or higher. By setting the supply rate to the adsorber to 11 m / s or higher and increasing the adsorption rate, it is possible to shorten t1, thereby making it easier to reduce costs. The upper limit of this supply rate can be appropriately set within the range that yields the effects of this disclosure and is not particularly limited. Alternatively, the supply rate may be less than 11 m / s.

[0035] Furthermore, the various components of the CO2 recovery apparatus can be appropriately used with conventionally known equipment to the extent that the effects of this disclosure are achieved, and are not particularly limited. Therefore, in the following description, only the parts that deserve special attention are described in this method, while other structural details are omitted.

[0036] The CO2 adsorbent may comprise a CO2 adsorbent capable of adsorbing CO2 and multiple porous supports on which the CO2 adsorbent is loaded. The adsorber 4 containing the CO2 adsorbent used in this method is preferably an adsorber capable of achieving an adsorption rate of 80% or more of the CO2 adsorbent even during short-time cycles (e.g., a cycle of 4 minutes or more but less than 60 minutes).

[0037] The porous carrier preferably has a honeycomb structure. By giving the porous carrier a honeycomb structure, pressure loss and wind speed reduction in CO2 recovery can be easily suppressed, and t1 can be set to a shorter time, thereby easily achieving cost reduction.

[0038] Porous carriers can be configured, for example, as a structure in which a porous material is coated on a honeycomb-shaped substrate (honeycomb substrate), wherein the porous material is mainly composed of either silica gel or alumina, and has multiple pores with an average pore size of 2 nm to 200 nm. Thus, the porous carrier is preferably coated with silica gel or alumina (especially silica gel).

[0039] Here, in Figure 3 The diagram shows an example graph illustrating the relationship between the adsorption rate of a CO2 adsorbent and the thickness of the silica gel coating on a porous support. Furthermore, the adsorption rate of the CO2 adsorbent refers to the value (adsorption capacity) assuming the adsorption capacity of the CO2 adsorbent is set to 100% by volume, provided that the CO2 adsorbent has been adsorbed for a sufficiently long time (e.g., more than 1 hour). Additionally, in... Figure 3 The figure shows the relationship between the thickness of the silica gel and the adsorption rate of the CO2 adsorbent (the same in each mode) in four modes when the adsorption time of CO2 relative to the CO2 adsorbent is set to 200 seconds, 300 seconds, 500 seconds and 900 seconds.

[0040] like Figure 3 As shown, the thinner the coating, the shorter the time it takes for CO2 to penetrate from the surface of the adsorbent to the interior, thus accelerating the adsorption of CO2 onto the adsorbent and increasing the adsorption rate. The thickness of the silica gel coating can be set to, for example, less than 250 μm, less than 220 μm, less than 200 μm, less than 180 μm, less than 150 μm, less than 120 μm, or less than 100 μm. For example, in... Figure 3In the example shown, with an adsorption time of 200 seconds and a silica gel (coating) thickness of less than 120 μm, the adsorption rate of the CO2 adsorbent can be set to more than 80% by volume.

[0041] CO2 adsorbents are not specifically limited, and examples include any of the following polyamines or amino compounds containing polyamines: polyethyleneimine, methylated polyethyleneimine, isopropylated polyimine, polyallylamine, pentaethylenehexamine, methylated pentaethylenehexamine, isopropylated pentaethylenehexamine, tetraethylenepentamine, methylated tetraethylenepentamine, and isopropylated tetraethylenepentamine.

[0042] From the perspective of excellent cycle durability, the CO2 adsorbent preferably contains polyethyleneimine with isopropyl groups.

[0043] As for the various costs involved in CO2 recovery (CO2 recovery cost: the cost required to recover 1 kg of CO2), for example, it can be considered to be divided into the following two aspects. Based on a comprehensive assessment of these costs and the amount of CO2 recovered, a judgment can be made on whether low-cost reduction is possible (refer to the JST (Science and Technology Agency) Low-Carbon Society Technology and the Recommendation for Innovation Strategy Development Based on Economic / Social Quantitative Scripts LCS-FY 2020-PP-06). Furthermore, the amount of CO2 recovered per unit time by the CO2 recovery device is the product of the number of cycles per unit time and the amount of CO2 that can be recovered in one cycle.

[0044] •CAPEX: The value obtained by dividing the total cost of equipment, depreciation years, construction / labor costs by the total amount of CO2 recovered by the equipment.

[0045] •OPEX: Energy costs, replacement costs for deteriorated adsorbents, and operating costs required to recover 1 kg of CO2.

[0046] In this method, for example, by using a low-pressure-loss honeycomb adsorber, the rate of CO2 adsorption and desorption (the number of times adsorption / desorption treatment is switched per equal time interval) is increased compared to the past, thereby reducing the proportion of equipment cost (CAPEX) in the cost of CO2 recovery. As a result, CO2 recovery can be implemented at a lower cost than before.

[0047] For example, this method can use an adsorber with the following features (and Figure 1 The CO2 recovery device (shown in other structures) performs CO2 recovery.

[0048] • Adsorber: A CO2 adsorbent (polyamines such as isopropyl polyethyleneimine) was impregnated and loaded into the silica gel portion (120 μm thick) of a porous carrier (a carrier formed by coating silica gel onto a honeycomb substrate). The honeycomb substrate was made of cordierite with a pore density of 400 cpsi and a wall thickness of 4.5 mil, and the loading of the coating material (silicone gel) was set to 50–150 g / L.

[0049] Thickness in the direction of wind speed: 0.1 meters Pressure loss: 0.0218 × (wind speed (m / s) squared): an approximation based on the following measured data. Actual measurement data: In a honeycomb substrate with L=0.05m, 400cpsi-4.5mil, and 100g / L silicone coating, The pressure is 1.7 kPa at a wind speed of 11.8 m / s and 6 kPa at a wind speed of 23.6 m / s. • Action conditions The total cycle time for adsorption and desorption treatment is less than 60 minutes (t1: 15 minutes, t2 < 60 minutes). As a comparison, a CO2 recovery device equipped with an amine / nanofiber adsorbent is used as a typical CO2 recovery method.

[0050] • Adsorber: A fiber filter formed by impregnating the following amine, which serves as a CO2 adsorbent, with the following substrate, which serves as a carrier. Amine: N-(2-aminoethyl)-3-aminopropyl-methyldimethoxysilane: AEAPDMS Substrate: Nanofibers (fibralatellulosesuspension) Thickness in the direction of wind speed: 1.2 meters Pressure loss: 5.53 kPa (wind speed 0.573 m / s) • Action conditions Adsorption treatment: room temperature (25℃), 1 atmosphere, 30 minutes Detachment process: 90℃, 0.03 atmospheres, 30 minutes per cycle, totaling 60 minutes. Figure 4A graph showing the relationship between cycle time (minutes) and cost ratio in this method and the aforementioned conventional CO2 recovery method used as a comparison is presented. This graph shows the cost ratio when using the aforementioned conventional CO2 recovery method, and the relative cost ratio when the baseline S is set to 1. Furthermore, the cost is comprehensively judged using the aforementioned CAPEX and OPEX. Additionally, since the electricity price (yen / kWh) has a significant impact on CO2 recovery costs, in addition to showing the scenarios with an electricity price of 4 yen / kWh, three other scenarios are also shown with electricity prices of 6 yen / kWh and 12 yen / kWh.

[0051] At this point, a trial calculation is performed on the cost ratio of CO2 recovery costs relative to baseline S based on the following five assumptions, and... Figure 4 The results are shown in the figure.

[0052] 1) The value of CAPEX is set to remain unchanged. The proportion of CAPEX in the recovery of 1 kg of CO2 decreases as the cycle time becomes shorter, that is, as the amount of CO2 recovered per unit time increases.

[0053] 2) The amount of air supplied to the adsorbent during one cycle is set to be constant.

[0054] 3) The shorter the circulation time, the higher the wind speed, and the more energy is required for air delivery due to pressure loss. Therefore, the cost per kg of CO2 recovered will increase accordingly.

[0055] 4) The energy required for air supply is proportional to the square of the wind speed.

[0056] 5) The cost of CO2 recovery is a trade-off between 1) and 3) above.

[0057] Referring to the graph, in this method using the aforementioned CO2 recovery device, when t2 is less than 60 minutes, it is possible to achieve a lower cost compared to the benchmark S, which serves as the comparison object for conventional CO2 recovery methods, regardless of electricity price.

[0058] Furthermore, although the lower limit of the cycle time that enables low-cost operation can be appropriately set depending on the adsorber used, Figure 4 In the CO2 recovery device shown, when t2 is 4 minutes or more, the cost ratio becomes less than 1. Therefore, the range of cycle times, indicated by the symbol X, becomes a range where cost reduction is achievable compared to the past. Furthermore, if we refer to this... Figure 4 In cases where the cycle time is, for example, more than 4 minutes but less than 20 minutes, further cost reduction can be achieved.

[0059] This invention is not limited to the embodiments described above, but can be appropriately modified without departing from the spirit of the invention. This invention contributes to carbon neutrality, decarbonization, and sustainable development goals (SDGs).

Claims

1. A CO2 recovery method comprising alternating and repeated adsorption and desorption of CO2, wherein in the adsorption and desorption of CO2, CO2 contained in the supplied gas is adsorbed onto a CO2 adsorbent, and by adjusting the CO2 adsorbent to a higher temperature than that during CO2 adsorption, the CO2 adsorbed on the CO2 adsorbent is desorbed from the CO2 adsorbent and recovered, wherein... When t1 is defined as the shortest time for CO2 to achieve an adsorption rate of 80% or more relative to the CO2 adsorbent, and t2 is defined as the time for one cycle consisting of the adsorption and desorption of CO2, t1 < t2 < 4 × t1 is satisfied.

2. The CO2 recovery method as described in claim 1, wherein, The CO2 adsorbent comprises a CO2 adsorbent and multiple porous supports on which the CO2 adsorbent is loaded. The CO2 adsorbent contains polyethyleneimine having isopropyl groups.

3. The CO2 recovery method as described in claim 2, wherein, The porous carrier has a honeycomb structure.

4. The CO2 recovery method as described in claim 1 or 2, wherein, The gas is supplied to the CO2 adsorbent at a rate of 11 m / s or higher.

5. The CO2 recovery method as described in claim 2 or 3, wherein, The porous carrier is coated with silica gel, the thickness of which is less than 250 μm.

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