Carbon dioxide recovery method and carbon dioxide recovery apparatus

Abstract

To provide a new CO2 recovery method capable of efficiently recovering CO2 from a raw material gas containing CO2 in low concentration (specifically, 100-10000 ppm).SOLUTION: A CO2 recovery method from a raw material gas using a CO2 permselective membrane includes: a step 1 to obtain a first permeation gas by contacting the raw material gas with a first CO2 permselective membrane; and a step 2 to obtain a second permeation gas by contacting the first permeation gas to the second CO2 permselective membrane. In the step 1, the raw material gas has a CO2 concentration of 100-10000 ppm, and a steam fraction of 1-10%, and the steam fraction of the first permeation gas is made higher than the steam fraction of the raw material gas by the first CO2 permselective membrane. In the step 2, the second CO2 permselective membrane is a promotion transport membrane and the CO2 purity of the second permeation gas is made higher than the CO2 purity of the first permeation gas by the second CO2 permselective membrane.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a CO2 recovery method and a CO2 recovery device using a CO2 selective permeable membrane. [Background technology]

[0002] In recent years, a technology called "Direct Air Capture (DAC)" that directly captures CO2 from the atmosphere has been attracting attention. In Japan, too, it is being considered for use as one of the measures to reduce greenhouse gas emissions in order to achieve "net zero" by 2050, as outlined in the Paris Agreement.

[0003] The CO2 concentration in the atmosphere is around 400 ppm, which is about 1 / 100 to 1 / 300 of the CO2 concentration in exhaust gas from thermal power plants. Therefore, capturing CO2 from the atmosphere has traditionally required a greater amount of energy than capturing CO2 from exhaust gases produced when fossil fuels are burned.

[0004] Furthermore, in order to capture low-concentration CO2, which exists in the atmosphere at only about 400 ppm, existing technologies require a large amount of energy to separate and capture CO2, such as by applying pressure and heating. In order to efficiently increase the amount of CO2 captured, there is no choice but to take advantage of economies of scale, which necessitates large-scale facilities.

[0005] In urban areas with high population density and high CO2 emissions, there are limited locations for constructing large-scale DAC facilities. Therefore, there is a demand for the development of small-sized equipment that can be installed in densely populated areas and industrial areas with high CO2 concentrations, as well as technology with high capture efficiency. As a technology that is expected to realize such compact CO2 separation and capture, a separation and capture method using a CO2 separation membrane (CO2 selective permeable membrane) has attracted attention.

[0006] As CO2 separation membranes with excellent selective permeability for CO2, various polymer membranes such as rubber-like polymer membranes, glassy polymer membranes, and facilitated transport membranes have been developed. For example, Patent Document 1 discloses a CO2 capture method using a facilitated transport membrane as a gas separation membrane. In the facilitated transport membrane, a mixed gas containing carbon dioxide together with water (water vapor) is supplied to one side of the facilitated transport membrane as a gas separation membrane, and the CO2 is ionized by the gas separation membrane, allowing the carbon dioxide to selectively permeate the gas separation membrane and the CO2 to be captured. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2012-192316 A Summary of the Invention [Problem to be solved by the invention]

[0008] The main object of the present disclosure is to provide a novel CO2 capture method for efficiently capturing CO2 from a raw gas containing CO2 at a low concentration (specifically, about 100 to 10,000 ppm). Another object of the present disclosure is to provide a CO2 capture device that can be suitably used in the CO2 capture method. [Means for solving the problem]

[0009] The inventors of the present disclosure have conducted intensive research to solve the above problems. As a result, they have found that a method for recovering CO2 from a raw gas using a CO2 selective permeable membrane includes a step 1 of contacting the raw gas with a first CO2 selective permeable membrane to obtain a first permeable gas, and a step 2 of contacting the first permeable gas with a second CO2 selective permeable membrane to obtain a second permeable gas, in which the raw gas has a CO2 concentration of 100 to 10,000 ppm and a water vapor fraction of 1 to 10%, the water vapor fraction of the first permeable gas is increased by the first CO2 selective permeable membrane in the step 1, the second CO2 selective permeable membrane is used as a facilitated transport membrane, and the second CO2 selective permeable membrane is used to increase the CO2 purity of the second permeable gas to be higher than the CO2 purity of the first permeable gas in the step 2, thereby enabling efficient recovery of CO2 from a raw gas containing a low concentration of CO2.

[0010] The present disclosure has been completed based on these findings and through further investigations. That is, the present disclosure provides the invention of the following aspects. Item 1. A method for recovering CO2 from a raw gas using a CO2 selective permeable membrane, A step 1 of contacting the raw material gas with a first CO2 permselective membrane to obtain a first permeable gas; a step 2 of contacting the first permeable gas with a second CO2 selective permeable membrane to obtain a second permeable gas; Equipped with In the step 1, the raw material gas has a CO2 concentration of 100 to 10,000 ppm and a water vapor fraction of 1 to 10%, In the step 1, the water vapor fraction of the first permeable gas is increased by the first CO2 selective permeable membrane to be higher than the water vapor fraction of the raw material gas; In the step 2, the second CO2 permselective membrane is a facilitated transport membrane, A CO2 recovery method, in which in the step 2, the CO2 purity of the second permeable gas is increased to be higher than the CO2 purity of the first permeable gas by the second CO2 selective permeable membrane. Item 2. The method for recovering CO2 according to Item 1, wherein the steps 1 and 2 are carried out in a temperature range of 1 to 200°C. Item 3. The CO2 recovery method according to Item 1 or 2, wherein the facilitated transport membrane has a water vapor permeability coefficient of 500,000 barrer or less. Item 4. The surface area of ​​the first CO2 selective permeable membrane is 5 to 100 m 2 and the surface area of ​​the second CO2 selective permeable membrane is 2 to 200 m 2 4. The method for recovering CO2 according to any one of items 1 to 3, Item 5. The method for recovering CO2 according to any one of Items 1 to 4, wherein the second permeable gas has a CO2 purity of 10% or more. Item 6. A CO2 recovery device used to recover CO2 from a raw gas, a first CO2 selective permeable membrane for contacting the raw material gas to obtain a first permeable gas; a second CO2 selective permeable membrane for contacting the first permeable gas to obtain a second permeable gas; Equipped with The water vapor fraction of the first permeable gas is increased to be higher than the water vapor fraction of the feed gas by the first CO2 selective permeation membrane, The second CO2 permselective membrane is a facilitated transport membrane, A CO2 recovery device, wherein the second CO2 selective permeable membrane increases the CO2 purity of the second permeable gas to be higher than the CO2 purity of the first permeable gas. Effect of the Invention

[0011] According to the present disclosure, it is possible to provide a novel CO2 capture method for efficiently capturing CO2 from a raw material gas containing CO2 at a low concentration (specifically, about 100 to 10,000 ppm). Furthermore, according to the present disclosure, it is also possible to provide a CO2 capture device that can be suitably used in the CO2 capture method.

[0012] According to the CO2 capture method of the present disclosure, it is possible to capture CO2 at a high concentration (for example, CO2 purity of 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, or even 90% or more). In conventional technology, large-scale equipment is required to obtain gas containing high concentration CO2 (CO2 capture gas), but according to the CO2 capture method of the present disclosure, it can be realized with a small CO2 capture device (for example, the size of a small refrigerator (for example, volume of 40 L to 2000 L). [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a conceptual diagram showing the molar flow rate of gas component j in a membrane module in a simulation of CO2 gas recovery using a CO2 selective permeable membrane (calculation of CO2 recovery rate, CO2 purity, etc. under specified calculation conditions). [Diagram 2] FIG. 1 is a schematic diagram of a CO2 recovery method (three-stage process) of Reference Example 1. [Diagram 3] 2 is a graph showing the relationship between the membrane area (m2), the CO2 recovery rate (%), and the CO2 purity (%) in the first, second, and third stage membrane modules of the CO2 recovery method of Reference Example 1. [Figure 4] FIG. 1 is a schematic diagram of a CO2 recovery method (three-stage process) of Reference Example 2. [Diagram 5] 1 is a graph showing the relationship between membrane area (m2), CO2 recovery rate (%), and CO2 purity (%) in the first, second, and third membrane modules of the CO2 recovery method of Reference Example 2. [Figure 6] FIG. 1 is a schematic diagram of a CO2 recovery method (single-stage process) of Reference Example 3. [Figure 7] 1 is a graph showing the relationship between CO 2 permeation rate and water vapor fraction in the membrane module of Reference Example 3. [Figure 8] FIG. 1 is a schematic diagram of a CO2 recovery method (single-stage process) of Reference Example 4. [Figure 9] 1 is a graph showing the relationship between the membrane area (m2), the CO2 recovery rate (%), and the CO2 purity (%) in the membrane module of Reference Example 4. [Figure 10] FIG. 1 is a schematic diagram of a CO2 recovery method (single-stage process) of Reference Example 5. [Figure 11] 1 is a graph showing the relationship between the membrane area (m2), the CO2 recovery rate (%), and the CO2 purity (%) in the membrane module of Reference Example 5. [Figure 12] FIG. 1 is a schematic diagram of a CO2 recovery method (two-stage process) of Example 1. [Figure 13] 2 is a graph showing the relationship between the membrane area (m2), the CO2 recovery rate (%), and the CO2 purity (%) in the first and second stage membrane modules of the CO2 recovery method of Example 1. [Figure 14] FIG. 1 is a graph showing the results of calculating the relationship between the water vapor permeability coefficient (barrer), the CO2 recovery rate (%), and the CO2 purity (%) in the second-stage membrane module of Example 2 (the same as in Example 1). [Figure 15] The graph shown in Fig. 1 of SJMrets et al. / Journal of Membrane Science 251 (2005) 29-41 (a graph showing the relationship between H2O / N2 selectivity and water vapor permeability coefficient of various membranes) [Figure 16] FIG. 1 is a schematic diagram of a CO2 recovery method (three-stage process) according to Example 3. [Figure 17] FIG. 1 is a graph (left) showing the relationship between the membrane area (m2) and the CO2 recovery rate (%) and CO2 purity (%) in the second-stage membrane module of the CO2 recovery method of Example 3, and a graph (right) showing the relationship between the membrane area (m2) and the CO2 recovery rate (%) and CO2 purity (%) in the second-stage (AAIL-SILM) of the CO2 recovery method of Example 1. [Figure 18] 1 is a graph showing the relationship between the membrane area (m2), the CO2 recovery rate (%), and the CO2 purity (%) in the first, second, and third stage membrane modules of the CO2 recovery method of Example 3. [Figure 19] FIG. 1 is a schematic diagram of a CO2 recovery method (three-stage process) according to Example 4. [Figure 20]FIG. 1 is a graph (left side) showing the relationship between the membrane area (m2) and the CO2 recovery rate (%) and CO2 purity (%) in the first stage membrane module of the CO2 recovery method of Example 4, and a graph (right side) showing the relationship between the membrane area (m2) and the CO2 recovery rate (%) and CO2 purity (%) in the first stage (PIM membrane) of Example 1. [Figure 21] FIG. 1 is a graph (left side) showing the relationship between the membrane area (m2) and the CO2 recovery rate (%) and the CO2 purity (%) in the second stage membrane module of the CO2 recovery method of Example 4, and a graph (right side) showing the relationship between the membrane area (m2) and the CO2 recovery rate (%) and the CO2 purity (%) in the second stage (AAIL-SILM) of the CO2 recovery method of Example 1. [Figure 22] FIG. 1 is a graph (left side) showing the relationship between the membrane area (m2) and the CO2 recovery rate (%) and the CO2 purity (%) in the third stage membrane module of the CO2 recovery method of Example 4, and a graph (right side) showing the relationship between the membrane area (m2) and the CO2 recovery rate (%) and the CO2 purity (%) in the third stage (AAIL-SILM) of the CO2 recovery method of Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The CO2 recovery method disclosed herein is a method for recovering CO2 from a raw gas using a CO2 selective permeable membrane, and includes step 1 of contacting the raw gas with a first CO2 selective permeable membrane to obtain a first permeable gas, and step 2 of contacting the first permeable gas with a second CO2 selective permeable membrane to obtain a second permeable gas, wherein in step 1, the raw gas has a CO2 concentration of 100 to 10,000 ppm and a water vapor fraction of 1 to 10%, and in step 1, the first CO2 selective permeable membrane increases the water vapor fraction of the first permeable gas above that of the raw gas, and in step 2, a facilitated transport membrane is used as the second CO2 selective permeable membrane, and in step 2, the second CO2 selective permeable membrane increases the CO2 purity of the second permeable gas above that of the first permeable gas. The water treatment method of the present disclosure, by being provided with the above-described configuration, can efficiently recover CO2 from a raw material gas containing CO2 at a low concentration (specifically, about 100 to 10,000 ppm).

[0015] The CO2 capture method and CO2 capture device disclosed herein will be described in detail below.

[0016] In this specification, a numerical value connected with "~" means a numerical range including the numerical values ​​before and after "~" as the lower limit and upper limit. When multiple lower limit values ​​and multiple upper limit values ​​are listed separately, any lower limit value and upper limit value can be selected and connected with "~".

[0017] 1.CO 2 Collection method The CO2 capture method of the present disclosure is a method for capturing CO2 from a raw material gas using a CO2 selective permeable membrane. The CO2 capture method of the present disclosure includes at least the following steps 1 and 2.

[0018] (Step 1) A step of contacting a raw material gas with a first CO2 selective permeable membrane to obtain a first permeable gas. (Step 2) A step of contacting the first permeable gas with a second CO2 selective permeable membrane to obtain a second permeable gas.

[0019] In the CO2 capture method of the present disclosure, in step 1, the water vapor fraction of the first permeable gas is increased to be higher than the water vapor fraction of the feed gas by a first CO2 selective permeable membrane. In addition, in step 2, the CO2 purity of the second permeable gas is increased to be higher than the CO2 purity of the first permeable gas by a second CO2 selective permeable membrane (facilitated transport membrane). In the CO2 capture method of the present disclosure, by combining these steps 1 and 2, it becomes possible to efficiently capture CO2 from a feed gas containing a low concentration of CO2 (specifically, about 100 to 10,000 ppm).

[0020] In the CO2 capture method of the present disclosure, a step of adjusting the composition of the first permeable gas obtained through step 1 may be further included between step 1 and step 2. In the present disclosure, even when such a step is further included, the gas that is supplied to step 2 through step 1 is referred to as the first permeable gas. In addition, between step 1 and step 2, it is preferable to adjust the temperature and pressure suitable for step 2.

[0021] Furthermore, the CO2 capture method of the present disclosure may further include, after step 2, a step of adjusting the composition, temperature, pressure, etc. of the second permeable gas obtained in step 2.

[0022] In a simulation of CO2 gas recovery using a CO2 selective permeable membrane (calculation of CO2 recovery rate, CO2 purity, etc. under given calculation conditions), the molar flow rate of gas component j in the membrane module can be shown as shown in Figure 1. In CO2 gas recovery using a membrane module, both the CO2 partial pressure and the water vapor fraction change continuously from the inlet to the outlet of the membrane module. Within the membrane module, the CO2 permeation rate also changes continuously with changes in the CO2 partial pressure and water vapor fraction.

[0023] Furthermore, the mass balance in the micro-section in the membrane module can be expressed by the following formula: The mass balance in the micro-section in the membrane module in steps 1 and 2 can be calculated using the following formula.

[0024]

number

[0025] Steps 1 and 2 of the CO2 capture method of the present disclosure will be described in detail below.

[0026] [Process 1] In step 1, the raw material gas contacted with the first CO2 selective permeable membrane has a CO2 concentration of 100 to 10,000 ppm and a water vapor fraction of 1 to 10%. Examples of raw material gases that satisfy such a composition include the atmosphere (outside air, airtight houses and offices, indoor air of long-distance passenger air, etc.).

[0027] The CO2 concentration of the raw material gas may be 100 to 10,000 ppm, but from the viewpoint of more suitably exerting the effects of the present disclosure, it is preferably 200 ppm or more, more preferably 250 ppm or more, even more preferably 300 ppm or more, and is preferably 5,000 ppm or less, more preferably 2,000 ppm or less, even more preferably 1,000 ppm or less. As a preferred range, it is about 100 to 5,000 ppm, 100 to 2,000 ppm. m, about 100 to 1000 ppm, about 200 to 10000 ppm, about 200 to 5000 ppm, about 200 to 2000 ppm, about 200 to 1000 ppm, about 250 to 10000 ppm, about 250 to 5000 ppm, about 250 to 2000 ppm, about 250 to 1000 ppm, about 300 to 10000 ppm, about 300 to 5000 ppm, about 300 to 2000 ppm, and about 300 to 1000 ppm.

[0028] The water vapor fraction of the raw material gas may be 1 to 10%, but from the viewpoint of more suitably exerting the effects of the present disclosure, it is preferably 1.2% or more, more preferably 1.7% or more, and even more preferably 2.3% or more, and is preferably 7.4% or less, more preferably 5.6% or less, and even more preferably 3.7% or less. Preferred ranges include about 1 to 7.4%, about 1 to 5.6%, about 1 to 3.7%, about 1.2 to 10%, about 1.2 to 7.4%, about 1.2 to 5.6%, about 1.2 to 3.7%, about 1.7 to 10%, about 1.7 to 7.4%, about 1.7 to 5.6%, about 1.7 to 3.7%, about 2.3 to 10%, about 2.3 to 7.4%, about 2.3 to 5.6%, and about 2.3 to 3.7%.

[0029] Furthermore, other components of the source gas are not particularly limited as long as the effects of the present disclosure are achieved, but for example, the N2 concentration is about 75 to 78%, and the O2 concentration is about 20 to 21%.

[0030] The temperature of the raw material gas is not particularly limited, but is preferably 1°C or higher, more preferably 10°C or higher, and even more preferably 20°C or higher, and is preferably 200°C or lower, more preferably 40°C or lower, and even more preferably 30°C or lower. Preferred ranges include about 1 to 200°C, about 1 to 40°C, about 1 to 30°C, about 10 to 200°C, about 10 to 40°C, about 10 to 30°C, about 20 to 200°C, about 20 to 40°C, and about 20 to 30°C.

[0031] The relative humidity of the raw material gas is not particularly limited, but is preferably higher, and is preferably 10% or more, more preferably 30% or more, and even more preferably 50% or more. The upper limit is, for example, 99% or less, 95% or less, more preferably 90% or less, or 80% or less. Preferred ranges include about 10 to 99%, about 10 to 95%, about 10 to 90%, about 10 to 80%, about 30 to 99%, about 30 to 95%, about 30 to 90%, about 30 to 80%, about 50 to 99%, about 50 to 95%, about 50 to 90%, and about 50 to 80%.

[0032] In step 1, the temperature at which the raw material gas is contacted with the first CO2 selective permeable membrane to obtain the first permeable gas is not particularly limited as long as the first CO2 selective permeable membrane can increase the water vapor fraction of the first permeable gas to be higher than the water vapor fraction of the raw material gas. The temperature is preferably 1°C or higher, more preferably 10°C or higher, and even more preferably 20°C or higher, and is preferably 200°C or lower, more preferably 40°C or lower, and even more preferably 30°C or lower. Preferred ranges include about 1 to 200°C, about 1 to 40°C, about 1 to 30°C, about 10 to 200°C, about 10 to 40°C, about 10 to 30°C, about 20 to 200°C, about 20 to 40°C, and about 20 to 30°C.

[0033] The first CO2 selective permeable membrane used in step 1 is not particularly limited, and any known CO2 selective permeable membrane can be used as long as it can increase the water vapor fraction of the first permeable gas to be higher than the water vapor fraction of the raw material gas, and a commercially available product can also be used. For example, rubber-like polymer membranes, glass-like polymer membranes, zeolite membranes, ceramic membranes, etc. are known as CO2 selective permeable membranes, and these membranes can be suitably used as the first CO2 selective permeable membrane in the present disclosure.

[0034] Examples of the rubber-like polymer film include polydimethylsiloxane (PDMS film), polyethylene glycol (PEO film), etc. Specific examples of the rubber-like polymer film include those described in the Examples.

[0035] Examples of the glassy polymer membrane include a PIM (Polymer of Intrinsic Microporosity) membrane, a polyimide membrane, etc. Specific examples of the glassy polymer membrane include those described in the Examples.

[0036] In the first CO2 permselective membrane, the CO2 permeation rate is preferably 10,000 to 100,000 GPU, more preferably 20,000 to 50,000 GPU, and further preferably 30,000 to 40,000 GPU.

[0037] Furthermore, in the first CO2 selective permeable membrane, the CO2 / N2 permeation selectivity is preferably 5 or more, more preferably 7 or more, even more preferably 10 or more, and even more preferably 15 or more, and the upper limit is, for example, 50 or less, 20 or less, and preferred ranges include about 5 to 50, about 5 to 20, about 7 to 50, about 7 to 20, about 10 to 50, about 10 to 20, about 15 to 50, and about 15 to 20.

[0038] Moreover, in the first CO2 selective permeable membrane, the water vapor permeability coefficient is preferably 10,000 to 1,000,000 barrer, more preferably 100,000 to 1,000,000 barrer, and further preferably 500,000 to 1,000,000 barrer.

[0039] Moreover, the first CO2 permselective membrane has a membrane thickness of preferably about 0.1 to 50 μm, more preferably about 0.1 to 10 μm, and further preferably about 0.1 to 1 μm.

[0040] In order to more effectively exert the effects of the present invention, the surface area of ​​the first CO2 selective permeable membrane is preferably 5 m 2 More than 10m, preferably 10m 2 More than 20m, more preferably 20m 2 More than 100m, preferably 2 Less than or equal to 50m, preferably 2 Less than 30m, more preferably 30m 2 The preferred range is 5 to 100 m. 2 Approximately 5~50m 2 Approximately 5~30m 2 Approximately 10~100m 2 Approximately 10~50m 2 Approximately 10~30m 2 Approximately 20~100m 2 Approximately 20~50m 2 Approximately 20~30m 2 The degree of

[0041] In step 1, it is preferable to use a membrane module of the first CO2 selectively permeable membrane (a single membrane module made up of a plurality of first CO2 selectively permeable membranes). Step 1 may be configured as a single stage using one membrane module of the first CO2 selectively permeable membrane, or as a two or more stages using two or more membrane modules. The first CO2 selectively permeable membrane contained in one membrane module may be of only one type, or of two or more types. When two or more membrane modules are used, the first CO2 selectively permeable membrane may be of only one type, or of two or more types.

[0042] In step 1, it is preferable to design the membrane module so that the surface area of ​​the first CO2 selectively permeable membrane is the above-mentioned surface area. For example, the number of first CO2 selectively permeable membranes included in one membrane module is preferably 1 to 1000, more preferably 3 to 100, and even more preferably 5 to 10. The size of one membrane module is, for example, a volume of 1000 to 200000 cm. 3 From the viewpoint of compact CO2 separation and capture, it is preferable that step 1 has a one-stage configuration using one membrane module of the first CO2 selectively permeable membrane, or a two-stage configuration using two membrane modules of the first CO2 selectively permeable membrane.

[0043] For example, as shown in FIG. 12, in step 1, a blower is used to send the raw material gas to the first CO2 selective permeable membrane, the raw material gas is brought into contact with the first CO2 selective permeable membrane, and the gas that has permeated the first CO2 selective permeable membrane from the raw material gas is obtained as a first permeated gas. By providing a pressure difference between one side and the other side of the first CO2 selective permeable membrane, the gas can be permeated from one side to the other side of the first CO2 selective permeable membrane. In order to provide a pressure difference between one side and the other side of the first CO2 selective permeable membrane, a decompression pump or the like can be used. The pressure difference between one side and the other side of the first CO2 selective permeable membrane is, for example, 105,000 to 100,000 Pa. The raw material side is, for example, atmospheric pressure, which varies depending on the weather, etc. Also, the permeation side is, for example, 0.5 to 5 kPa.

[0044] The CO2 recovery rate (%) in step 1 varies depending on the surface area of ​​the first CO2 selective permeable membrane, but is preferably 30% or more, more preferably 40% or more, and even more preferably 50% or more, and is preferably 90% or less, more preferably 80% or less, and even more preferably 70% or less. Preferred ranges include approximately 30 to 90%, approximately 30 to 80%, approximately 30 to 70%, approximately 40 to 90%, approximately 40 to 80%, approximately 40 to 70%, approximately 50 to 90%, approximately 50 to 80%, and approximately 50 to 70%.

[0045] The CO2 purity (%) in step 1 varies depending on the surface area of ​​the first CO2 selective permeable membrane, but is preferably 0.05% or more, more preferably 0.1% or more, and even more preferably 0.3% or more, and is preferably 50% or less, more preferably 10% or less, and even more preferably 1% or less. Preferred ranges include about 0.05 to 50%, about 0.05 to 10%, about 0.05 to 1%, about 0.1 to 50%, about 0.1 to 10%, about 0.1 to 1%, about 0.3 to 50%, about 0.3 to 10%, and about 0.3 to 1%.

[0046] In step 1, the ratio of the water vapor fraction of the first permeable gas to the water vapor fraction of the raw material gas (water vapor fraction of first permeable gas / water vapor fraction of raw material gas) is preferably 10 or more, more preferably 50 or more, and even more preferably 100 or more. Preferred ranges include 10 to 200, 50 to 200, and 100 to 200.

[0047] [Process 2] In step 2, the first permeable gas obtained through step 1 is contacted with a second CO2 permselective membrane to obtain a second permeable gas. In step 2, the second CO2 permselective membrane is a facilitated transport membrane. In step 2, the second CO2 permselective membrane increases the CO2 purity of the second permeable gas to be higher than the CO2 purity of the first permeable gas.

[0048] From the viewpoint of more suitably exerting the effects of the present invention, the CO2 concentration of the first permeable gas supplied to step 2 is preferably 1000 ppm or more, more preferably 2000 ppm or more, and even more preferably 4000 ppm or more, and is preferably 500,000 ppm or less, more preferably 300,000 ppm or less, and even more preferably 100,000 ppm or less, and preferred ranges are about 1000 to 500,000 ppm, about 1000 to 300,000 ppm, about 1000 to 100,000 ppm, about 2000 to 500,000 ppm, about 2000 to 300,000 ppm, about 2000 to 100,000 ppm, about 4000 to 500,000 ppm, about 4000 to 300,000 ppm, and about 4000 to 100,000 ppm.

[0049] From the viewpoint of more suitably exerting the effects of the present invention, the water vapor fraction of the first permeable gas subjected to step 2 is preferably 5% or more, more preferably 10% or more, and even more preferably 20% or more, and is preferably 95% or less, more preferably 90% or less, and even more preferably 80% or less, and preferred ranges are about 5 to 95%, about 5 to 90%, about 5 to 80%, about 10 to 95%, about 10 to 90%, about 10 to 80%, about 20 to 95%, about 20 to 90%, and about 20 to 80%.

[0050] The first permeable gas used in step 2 has, for example, an N2 concentration of about 15 to 65% and an O2 concentration of about 5 to 15%.

[0051] In step 2, the temperature at which the first permeable gas is contacted with the second CO2 selective permeable membrane to obtain the second permeable gas is not particularly limited as long as the CO2 purity of the second permeable gas can be increased to be higher than the CO2 purity of the first permeable gas by the second CO2 selective permeable membrane in step 2. The temperature is preferably 1°C or higher, more preferably 50°C or higher, and even more preferably 75°C or higher, and is preferably 200°C or lower, more preferably 150°C or lower, and even more preferably 100°C or lower. Preferred ranges include about 1 to 200°C, about 1 to 150°C, about 1 to 100°C, about 50 to 200°C, about 50 to 150°C, about 50 to 100°C, about 75 to 200°C, about 75 to 150°C, about 75 to 100°C, and about 75 to 100°C.

[0052] The second CO2 selectively permeable membrane used in step 2 may be a known facilitated transport membrane, or a commercially available product, as long as it is a facilitated transport membrane. Examples of facilitated transport membranes as CO2 selectively permeable membranes include amino acid-containing membranes, alkali metal carbonate-containing membranes, and amino acid ionic liquid-containing membranes. In the present disclosure, these facilitated transport membranes can be suitably used as the second CO2 selectively permeable membrane. In the present disclosure, the facilitated transport membrane may be used in combination with other membranes in step 2. Specific examples of facilitated transport membranes include those described in the Examples.

[0053] In the second CO2 permselective membrane, the CO2 permeation rate depends on the temperature, CO2 partial pressure, and water vapor fraction, but is preferably 100 to 10,000 GPU, more preferably 500 to 7,000 GPU, and further preferably 1,000 to 5,000 GPU.

[0054] In addition, in the second CO2 selective permeable membrane, the CO2 / N2 permeation selectivity depends on the temperature, CO2 partial pressure, and water vapor fraction, but is preferably 10 or more, more preferably 50 or more, and even more preferably 100 or more. Preferred ranges include 10 to 1000, 50 to 1000, and 100 to 1000.

[0055] Furthermore, in the second CO2 selective permeable membrane, the water vapor transmission rate is preferably 1 to 2000 GPU, more preferably 100 to 10000 GPU, and further preferably 200 to 1000 GPU.

[0056] Moreover, the second CO2 permselective membrane has a membrane thickness of preferably about 0.1 to 100 μm, more preferably about 0.5 to 50 μm, and further preferably about 1 to 20 μm.

[0057] In order to more effectively exert the effects of the present invention, the surface area of ​​the second CO2 selective permeable membrane is preferably 2 m 2 More than 5m, preferably 5m 2 More than 10m, preferably 10m 2 More than 200m, preferably 2Less than or equal to 100m, preferably 2 Less than 50m, more preferably 2 The preferred range is 2 to 200 m. 2 Approximately 2~100m 2 Approximately 2~50m 2 Approximately 5~200m 2 Approximately 5~100m 2 Approximately 5~50m 2 Approximately 10~200m 2 Approximately 10~100m 2 Approximately 10~50m 2 The degree of

[0058] In step 2, it is preferable to use a membrane module of the second CO2 selectively permeable membrane (a single membrane module made up of a plurality of second CO2 selectively permeable membranes). Step 2 may be configured as a single stage using one membrane module of the second CO2 selectively permeable membrane, or as a two or more stages using two or more membrane modules. The second CO2 selectively permeable membrane included in one membrane module may be of only one type, or of two or more types. When two or more membrane modules are used, the second CO2 selectively permeable membrane may be of only one type, or of two or more types.

[0059] Furthermore, step 2 may be a single-stage configuration using one membrane module of the second CO2 selectively permeable membrane, or a two-stage or more configuration using two or more. In step 2, it is preferable to design the membrane module so that the surface area of ​​the second CO2 selectively permeable membrane is the above-mentioned surface area. For example, the number of second CO2 selectively permeable membranes included in one membrane module is preferably 1 to 50, more preferably 2 to 50, and even more preferably 5 to 10. Furthermore, the size of one membrane module is, for example, a volume of 10,000 to 200,000 cm. 2 From the viewpoint of compact CO2 separation and capture, it is preferable that step 2 has a one-stage configuration using one membrane module of the second CO2 selectively permeable membrane, or a two-stage configuration using two membrane modules of the second CO2 selectively permeable membrane.

[0060] For example, as shown in FIG. 12, in step 2, for example, the first permeable gas obtained through step 1 is sent to a second CO2 selective permeable membrane using a vacuum pump, the first permeable gas is brought into contact with the second CO2 selective permeable membrane, and the gas that has permeated the second CO2 selective permeable membrane among the first permeable gas is obtained as a second permeable gas. By providing a pressure difference between one side and the other side of the second CO2 selective permeable membrane, the gas can be permeated from one side to the other side of the second CO2 selective permeable membrane. In order to provide a pressure difference between one side and the other side of the second CO2 selective permeable membrane, a vacuum pump or the like can be used, as in step 1. The pressure difference between one side and the other side of the second CO2 selective permeable membrane is, for example, 105,000 to 100,000 Pa. The raw material side is, for example, atmospheric pressure, which varies depending on the weather, etc. In addition, the permeation side is, for example, 0.5 to 5 kPa.

[0061] The CO2 recovery rate (%) in step 2 will vary depending on the CO2 recovery rate (%) in step 1 and the surface area of ​​the second CO2 selective permeable membrane, but is preferably 50% or more, more preferably 80% or more, and even more preferably 90% or more. Also, it is preferably 100%, 99% or less, 98% or less, 97% or less, etc., and preferred ranges include about 50 to 100%, about 50 to 99%, about 50 to 98%, about 50 to 97%, about 80 to 100%, about 80 to 99%, about 80 to 98%, about 80 to 97%, about 90 to 100%, about 90 to 99%, about 90 to 98%, and about 90 to 97%.

[0062] The CO2 purity (%) in step 2 varies depending on the CO2 purity (%) in step 1, the surface area of ​​the second CO2 selective permeable membrane, etc., but is preferably 10% or more, more preferably 20% or more, even more preferably 30% or more, even more preferably 40% or more, even more preferably 50% or more, even more preferably 60% or more, even more preferably 70% or more, even more preferably 80% or more, and even more preferably 90% or more, and the upper limit is, for example, 99% or less, and preferred ranges include about 10 to 99%, about 20 to 99%, about 30 to 99%, about 40 to 99%, about 50 to 99%, about 60 to 99%, about 70 to 99%, about 80 to 99%, and about 90 to 99%.

[0063] The CO2 recovery method of the present disclosure includes at least steps 1 and 2 described above, and thus can efficiently recover CO2 from a raw material gas containing CO2 at a low concentration (specifically, about 100 to 10,000 ppm).

[0064] The CO2 capture method of the present disclosure can be carried out, for example, using the CO2 capture device of the present disclosure described below.

[0065] 2.CO 2 Recovery device The CO2 capture device of the present disclosure is a CO2 capture device used to capture CO2 from a raw material gas. The CO2 capture device of the present disclosure can be suitably applied to the CO2 capture method of the present disclosure described in the above section "1. CO2 capture method".

[0066] The CO2 recovery device of the present disclosure includes a first CO2 selective permeable membrane for contacting a raw material gas to obtain a first permeable gas, and a second CO2 selective permeable membrane for contacting the first permeable gas to obtain a second permeable gas. The second CO2 selective permeable membrane is a facilitated transport membrane. The second CO2 selective permeable membrane increases the CO2 purity of the second permeable gas to be higher than the CO2 purity of the first permeable gas.

[0067] In the CO2 recovery device of the present disclosure, the composition of the raw gas from which CO2 is to be recovered is not particularly limited, as long as it contains CO2. From the viewpoint of optimally exerting the effects of the present disclosure, the raw gas preferably has a CO2 concentration of 100 to 10,000 ppm and a water vapor fraction of 1 to 10%. As described above, examples of raw gases that satisfy such a composition include the atmosphere (outdoor air, airtight houses and offices, indoor air of long-distance passenger air, etc.).

[0068] From the viewpoint of more suitably exerting the effects of the present disclosure, the CO2 concentration of the raw material gas is preferably 200 ppm or more, more preferably 250 ppm or more, and even more preferably 300 ppm or more, and is preferably 5000 ppm or less, more preferably 2000 ppm or less, and even more preferably 1000 ppm or less, and preferred ranges are about 200 to 5000 ppm, about 200 to 2000 ppm, about 200 to 1000 ppm, about 250 to 5000 ppm, about 250 to 2000 ppm, about 250 to 1000 ppm, about 300 to 5000 ppm, about 300 to 2000 ppm, and about 300 to 1000 ppm.

[0069] From the viewpoint of more suitably exerting the effects of the present invention, the water vapor fraction of the raw material gas is preferably 1.2% or more, more preferably 1.7% or more, and even more preferably 2.3% or more, and is preferably 7.4% or less, more preferably 5.6% or less, and even more preferably 3.7% or less, and preferred ranges are about 1 to 7.4%, about 1 to 5.6%, about 1 to 3.7%, about 1.2 to 10%, about 1.2 to 7.4%, about 1.2 to 5.6%, about 1.2 to 3.7%, about 1.7 to 10%, about 1.7 to 7.4%, about 1.7 to 5.6%, about 1.7 to 3.7%, about 2.3 to 10%, about 2.3 to 7.4%, about 2.3 to 5.6%, and about 2.3 to 3.7%.

[0070] The source gas has, for example, an N2 concentration of about 75 to 78% and an O2 concentration of about 20 to 21%.

[0071] The temperature of the raw material gas is not particularly limited, but is preferably 1°C or higher, more preferably 10°C or higher, and even more preferably 20°C or higher, and is preferably 200°C or lower, more preferably 40°C or lower, and even more preferably 30°C or lower. Preferred ranges include about 1 to 200°C, about 1 to 40°C, about 1 to 30°C, about 10 to 200°C, about 10 to 40°C, about 10 to 30°C, about 20 to 200°C, about 20 to 40°C, and about 20 to 30°C.

[0072] The relative humidity of the raw material gas is not particularly limited, but a higher humidity is preferable, and is preferably 10% or more, more preferably 30% or more, and even more preferably 50% or more. The upper limit is, for example, 99% or less, 95% or less, 90% or less, 80% or less, and preferred ranges include about 10 to 99%, about 10 to 95%, about 10 to 90%, about 10 to 80%, about 30 to 99%, about 30 to 95%, about 30 to 90%, about 30 to 80%, about 50 to 99%, about 50 to 95%, about 50 to 90%, and about 50 to 80%.

[0073] The first CO2 permselective membrane and the second CO2 permselective membrane are as described above in the section "1. CO2 capture method."

[0074] The CO2 capture method to which the CO2 capture device of the present disclosure is applied is not particularly limited, as long as the effects of the present disclosure are achieved, but the CO2 capture method of the present disclosure described in the above section "1. CO2 capture method" can be suitably applied. Therefore, as a specific method for capturing CO2 using the CO2 capture device of the present disclosure, the method described in the above section "1. CO2 capture method" can be applied.

[0075] The overall size of the CO2 capture device of the present disclosure is, for example, a volume of 0.1 to 10 m 3 Approximately 0.3 to 5 m 3 More preferably, the volume is 0.5 to 1 m 3 The degree of EXAMPLES

[0076] The present disclosure will be described more specifically below with reference to examples, but the present disclosure is not limited to these examples.

[0077] In a simulation of CO2 gas recovery using a CO2 selective permeable membrane (calculation of CO2 recovery rate, CO2 purity, etc. under given calculation conditions), the molar flow rate of gas component j in the membrane module can be shown as shown in Figure 1. From the inlet to the outlet of the membrane module, both the CO2 partial pressure and the water vapor fraction change continuously. Within the membrane module, the CO2 permeation rate also changes continuously with the changes in the CO2 partial pressure and water vapor fraction.

[0078] The mass balance in a small section in a membrane module can be expressed by the following formula: The following formula was also used in the following calculations.

number

[0079] <Reference example 1> The CO2 capture rate when capturing CO2 from the atmosphere using an existing rubber-like polymer membrane (PDMS membrane: S. Fujikawa et al., Chem. Lett., 48, 1351-1354, 2019 (doi:10.1246 / cl.190558)) was calculated under the following calculation conditions. A three-stage process was used, as shown in Figure 2, with PDMS membranes in the first, second, and third stages. The membrane module size was 5 cm high, 10.5 cm wide, and 20 cm deep, with 340 modules, and the overall size was 0.4 m, the size of a small refrigerator. 3 (Specifically, a diaphragm type vacuum pump (maximum vacuum level 1 kPa) is assumed for the pressure reducing pump. The size is 15 (W) x 25 (L) x 20 (H) cm. 3 =7500cm 3 We assume that the boosters are the same size. Three of each are needed, so the total size is 7500 x 2 x 3 = 45000 cm 3 The total capacity including the membrane module is approximately 400,000 cm 3 =0.4m 3)did.

[0080] (calculation conditions) The PDMS membrane had a CO2 permeation rate of 3,500 barrer, a CO2 / N2 permeation selectivity of 7, a membrane thickness of 1 μm, and a water vapor permeability coefficient of 500,000 barrer. The raw gas was air (CO2 concentration 400 ppm, temperature 25°C, relative humidity 50%).

[0081] The membrane area (m2) of the first, second, and third membrane modules in the CO2 capture method of Reference Example 1 2 Graphs showing the relationship between the CO2 recovery rate (%) and the CO2 purity (%) are shown in FIG.

[0082] As is clear from the results shown in Figure 3, the amount of CO2 captured by the PDMS membrane, a conventional rubber-like polymer membrane, was high at 6.22 kg / day in the third stage, but the CO2 purity in the captured gas was low at 3.4% (dry basis).

[0083] <Reference example 2> The CO2 capture rate when capturing CO2 from the atmosphere using an existing rubber-like polymer membrane (PIM membrane: Energy Environ. Sci., 2019, 12, 2733-2740) was calculated under the following calculation conditions. A three-stage process was used, as shown in Figure 4, with PIM membranes used in the first, second, and third stages. The size of the membrane module was 5 cm high, 10.5 cm wide, and 20 cm deep, with 179 modules, and the overall size was 0.15 m, the size of a small refrigerator. 3 (Specifically, three vacuum pumps and three boosters are required for the three-stage process, each with a size of 7,500 cm 3 Therefore, the total is about 45,000 cm 3 Membrane module (179 units) 87,950 cm 3 In total, this amounts to approximately 150,000 cm 3 =0.15m 3 )did.

[0084] (calculation conditions) The PIM membrane had a CO2 permeation rate of 20,400 barrer (426 days-aged TMN-Trip PIM), a CO2 / N2 permeation selectivity of 18.5 (426 days-aged TMN-Trip PIM), a membrane thickness of 1 μm, and a water vapor permeability coefficient of 10,000 barrer. The raw gas was air (CO2 concentration 400 ppm, temperature 25°C, relative humidity 50%).

[0085] The membrane area (m2) of the first, second, and third membrane modules in the CO2 capture method of Reference Example 2 2 Graphs showing the relationship between the CO2 recovery rate (%) and the CO2 purity (%) are shown in FIG.

[0086] As is clear from the results shown in Figure 5, the CO2 recovery amount of the PIM membrane, which is an existing glassy polymer membrane, was 7.25 kg / day in the third stage, which was even greater than that of the PDMS membrane shown in Reference Example 1. In addition, the CO2 purity in the recovered gas was 10.9% (dry basis), which was a higher value than that of the PDMS membrane.

[0087] <Reference example 3> Existing facilitated transport membranes ([P 4444 ][Pro]SILM:S. Kasahara et al., Chem. Commun., 2012, 48, 6903-6905(DOI: 10.1039 / c2cc17380h)S. Kasahara et al., Journal of Membrane Science 415-416 (2012) 168-175) was used to calculate the CO2 capture rate when capturing CO2 from the atmosphere using the following calculation conditions. A one-stage process was used as shown in Figure 6. The size of the membrane module was 5 cm in height, 10.5 cm in width, and 20 cm in depth, with 150 modules, and the overall size was 0.2 m, the size of a small refrigerator. 3 (150 membrane modules: 157,500 cm 3 and one vacuum pump and one booster for the one-stage process (7500 x 2 = 15,000 cm 3 ) totals approximately 0.2m 3)did.

[0088] (calculation conditions) The facilitated transport membrane had a CO2 permeation rate dependent on the CO2 partial pressure and water vapor fraction, a CO2 / N2 permeation selectivity dependent on the temperature, CO2 partial pressure and water vapor fraction, a membrane thickness of 1 μm and a water vapor permeability coefficient of 10,000 barrer. The raw gas was air (CO2 concentration 400 ppm, temperature 25°C, relative humidity 50%).

[0089] FIG. 7 shows a graph showing the relationship between the CO2 permeation rate and the water vapor fraction in the membrane module of the CO2 recovery method of Reference Example 3.

[0090] <Reference example 4> As in Reference Example 3, the existing facilitated transport membrane ([P 4444 ][Pro]SILM:S. Kasahara et al., Chem. Commun., 2012, 48, 6903-6905(DOI: 10.1039 / c2cc17380h)S. Kasahara et al., Journal of Membrane Science 415-416 (2012) 168-175) was used to calculate the CO2 capture rate when capturing CO2 from the atmosphere using the following calculation conditions. In Reference Example 4, a one-stage process as shown in Figure 8 was used. In Reference Example 4, the size of the membrane module was 5 cm in height, 10.5 cm in width, and 20 cm in depth, with 2000 modules, and the overall size was 2.2 m 3 (2,000 membrane modules) 2,100,000 cm 3 and one vacuum pump and one booster for the one-stage process (7500 x 2 = 15,000 cm 3 ) totals approximately 2.2m 3 )did.

[0091] (calculation conditions) The facilitated transport membrane had a CO2 permeation rate of 5,400-8,000 barrer (dependent on CO2 partial pressure and water vapor fraction), a CO2 / N2 permeation selectivity dependent on temperature, CO2 partial pressure and water vapor fraction, a membrane thickness of 20 μm and a water vapor permeability coefficient of 500,000 barrer. The raw gas was air (CO2 concentration 400 ppm, temperature 25°C, relative humidity 50% (water vapor fraction 0.0157 mol / mol)).

[0092] The membrane area (m ) of the membrane module of the CO2 recovery method of Reference Example 4 2 9 shows a graph showing the relationship between the CO2 recovery rate (%) and the CO2 purity (%).

[0093] As is clear from the results shown in Figure 9, the CO2 capture rate of the existing facilitated transport membrane was very low even with 2,000 modules.

[0094] <Reference example 5> As in Reference Examples 3 and 4, the existing facilitated transport membrane ([P 4444 ][Pro]SILM:S. Kasahara et al., Chem. Commun., 2012, 48, 6903-6905(DOI: 10.1039 / c2cc17380h)S. Kasahara et al., Journal of Membrane Science 415-416 (2012) 168-175) was used to calculate the CO2 capture rate in the case of capturing CO2 from the atmosphere under the following calculation conditions. In Reference Example 5, a one-stage process as shown in Figure 10 was used. In Reference Examples 3 and 4, the temperature in each process was 25°C, but in Reference Example 5, the temperature in each process was 100°C, the size of the membrane module was 5 cm high, 10.5 cm wide, and 20 cm deep, and there were 2000 units, and the overall size was 2.2 m 3 (2,000 membrane modules) 2,100,000 cm 3 and one vacuum pump and one booster for the one-stage process (7500 x 2 = 15,000 cm 3 ) totals approximately 2.2m 3 )did.

[0095] (calculation conditions) The facilitated transport membrane had a CO2 permeation rate of 5,400-8,000 barrer (dependent on CO2 partial pressure and water vapor fraction), a CO2 / N2 permeation selectivity dependent on temperature, CO2 partial pressure and water vapor fraction, a membrane thickness of 20 μm and a water vapor permeability coefficient of 500,000 barrer. The raw gas was air (CO2 concentration 400 ppm, temperature 100°C, relative humidity 1.6% (water vapor fraction 0.0157 mol / mol)).

[0096] The membrane area (m ) of the membrane module of the CO2 recovery method of Reference Example 5 2 FIG. 11 shows a graph showing the relationship between the CO2 recovery rate (%) and the CO2 purity (%).

[0097] As is clear from the results shown in Figure 11, the CO2 capture rate of the existing facilitated transport membrane was very low even when the temperature in each process was 100°C and 2,000 modules were used.

[0098] From the results of Reference Examples 1 to 5 above, it is found that it is difficult to increase the CO2 purity in the captured gas (for example, CO2 purity of 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, or even 90% or more) with the existing high-performance polymer membranes (PDMS membrane and PIM membrane). On the other hand, it is found that the CO2 capture rate is very low with the existing facilitated transport membrane (AAIL-SILM), and it is difficult to increase the CO2 capture rate to 50% or more.

[0099] <Example 1> We compared the existing rubber-like polymer membrane (PDMS membrane: S. Fujikawa et al., Chem. Lett., 48, 1351-1354, 2019 (doi:10.1246 / cl.190558)) and the existing facilitated transport membrane ([P 4444][Pro]SILM:S. Kasahara et al., Chem. Commun., 2012, 48, 6903-6905(DOI: 10.1039 / c2cc17380h)S. Kasahara et al., Journal of Membrane Science 415-416 (2012) 168-175) was combined to calculate the CO2 capture rate when capturing CO2 from the atmosphere under the following calculation conditions. A two-stage process was used as shown in Figure 12, with the first stage being a PDMS membrane and the second stage being a facilitated transport membrane. The size of the membrane module was 5 cm high, 10.5 cm wide, and 20 cm deep, with 250 PDMS membranes and 2000 facilitated transport membranes. The overall size was 2.4 m 3 (2,250 membrane modules) 2,362,500 cm 3 The vacuum pumps and boosters for the two-stage process are two each (7500 x 2 x 2 = 30,000 cm 3 ) totals approximately 2.4m 3 )did.

[0100] (calculation conditions) The PDMS membrane had a CO2 permeability rate of 10,000 barrer, a CO2 / N2 permeability selectivity of 7, a membrane thickness of 1 μm, and a water vapor permeability coefficient of 500,000 barrer. The facilitated transport membrane had a CO2 permeation rate dependent on temperature, CO2 partial pressure, and water vapor fraction, a CO2 / N2 permeation selectivity dependent on temperature, CO2 partial pressure, and water vapor fraction, a membrane thickness of 20 μm, and a water vapor permeability coefficient of 500,000 barrer. The raw gas was air (CO2 concentration 400 ppm, temperature 25°C, relative humidity 50%). The permeating gas is heated in the second stage so that its temperature is such that water vapor does not condense under atmospheric pressure.

[0101] The membrane area (m ) of the first and second membrane modules in the CO2 recovery method of Example 1 2 Graphs showing the relationship between the CO2 recovery rate (%) and the CO2 purity (%) are shown in FIG.

[0102] As is clear from the results shown in FIG. 13, by combining a PDMS membrane, which is an existing rubber-like polymer membrane, with a facilitated transport membrane, it is possible to increase the amount of CO2 captured and the purity of CO2 in the captured gas.

[0103] <Example 2> FIG. 14 shows a graph illustrating the results of calculating the relationship between the water vapor permeability coefficient (barrer) and the CO2 recovery rate (%) and the CO2 purity (%) in the second-stage membrane module in the case of the two-stage process shown in FIG. 12, which is the same as in Example 1.

[0104] As is clear from the graph shown in Figure 14, it can be seen that in the facilitated transport membrane, the CO2 recovery rate (%) and CO2 purity (%) are highest when the water vapor permeability coefficient is about 10,000 barrer. It is considered that the smaller the water vapor permeability coefficient of the facilitated transport membrane is below 10,000 barrer, the smaller the effect of diluting (reducing the concentration) CO2 by water vapor in the gas that has permeated the facilitated transport membrane, and the lower the driving force for permeation. On the other hand, it is considered that the larger the water vapor permeability coefficient of the facilitated transport membrane is above 10,000 barrer, the greater the decrease in the water vapor fraction in the module, and the lower the CO2 permeation rate.

[0105] <Example 3> The CO2 capture rate when an existing rubber-like polymer membrane (PDMS membrane: S. Fujikawa et al., Chem. Lett., 48, 1351-1354, 2019 (doi:10.1246 / cl.190558)) is combined with a facilitated transport membrane to capture CO2 from the atmosphere was calculated under the following calculation conditions. As a facilitated transport membrane, for example, an amino acid ionic liquid-impregnated membrane containing [P4444][Ala], which has alanine, a relatively hydrophobic amino acid, as the anion, or [P4444][Phe], which has phenylalanine, a hydrophobic amino acid, as the anion, can be considered. Of these, the synthesis method of [P4444][Ala] is described in "S. Kasahara et al., Journal of Membrane Science 415-416 (2012) 168-175". The synthesis method of [P4444][Phe] also follows the above paper. A three-stage process was used as shown in Figure 16. The first stage was a PDMS membrane, and the second and third stages were facilitated transport membranes. The size of the membrane module was 5 cm high, 10.5 cm wide, and 20 cm deep, with 250 PDMS membranes, 1000 facilitated transport membranes in the second stage, and 50 in the third stage. The overall size was 1.45 m. 3 (1,300 membrane modules) 1,365,000 cm 3 and a three-stage process vacuum pump and booster (three units each, 7500 x 2 x 3 = 45,000 cm 3 ) in total, 1.45m 3 In Example 3, the facilitated transport membrane was assumed to have a water vapor permeability coefficient of 10,000 barrer.

[0106] In addition, such a facilitated transport membrane with a low water vapor permeability coefficient can also be realized by combining an existing polyimide membrane with a low water vapor permeability coefficient with a facilitated transport membrane. For example, as shown in Figure 15, a polyimide membrane (PI) with a low water vapor permeability coefficient (about 1,000 barrer) is described in SJMrets et al. / Journal of Membrane Science 251 (2005) 29-41.

[0107] (calculation conditions) The PDMS membrane had a CO2 permeability rate of 10,000 barrer, a CO2 / N2 permeability selectivity of 7, a membrane thickness of 1 μm, and a water vapor permeability coefficient of 500,000 barrer. The facilitated transport membrane had a CO2 permeation rate dependent on temperature, CO2 partial pressure, and water vapor fraction, a CO2 / N2 permeation selectivity dependent on temperature, CO2 partial pressure, and water vapor fraction, a membrane thickness of 20 μm, and a water vapor permeability coefficient of 10,000 barrer. The raw gas was air (CO2 concentration 400 ppm, temperature 25°C, relative humidity 50%). The permeating gas is heated so that the gas temperature in the second and third stages is a temperature at which water vapor does not condense under atmospheric pressure.

[0108] The membrane area (m2) of the second-stage membrane module in the CO2 recovery method of Example 3 2 The graph showing the relationship between the membrane area (m2) in the second stage (AAIL-SILM) of the CO2 capture method in Example 1 and the CO2 purity (%) is shown in FIG. 2 ) and the CO2 recovery rate (%) and CO2 purity (%) are shown in FIG. 17 (right side).

[0109] As is clear from the results shown in Figure 17, by combining a facilitated transport membrane with a PDMS membrane, an existing rubber-like polymer membrane, and further using a facilitated transport membrane with a low water vapor permeability coefficient of about 10,000 barrer, the amount of CO2 captured and the purity of CO2 in the captured gas can be further increased.

[0110] The membrane area (m ) of the first, second and third membrane modules in the CO2 recovery method of Example 3 2 FIG. 18 shows a graph showing the relationship between the CO2 recovery rate (%) and the CO2 purity (%).

[0111] From the results shown in FIG. 18, according to the CO2 capture method of Example 3, the CO2 end amount in the third stage was 4.8 kg / day, and the CO2 concentration in the captured gas was 85.8% (dry basis), which were very high values.

[0112] <Example 4> Assuming a combination of an existing glassy polymer membrane (PIM membrane) and a facilitated transport membrane, the CO2 capture rate when capturing CO2 from the atmosphere was calculated under the following calculation conditions. As the facilitated transport membrane, for example, (1) an ionic liquid-type facilitated transport membrane with a small water vapor permeation rate, or (2) a highly gas-permeable polymer membrane with high CO2 / N2 permeation selectivity can be used. For (1) an ionic liquid-type facilitated transport membrane with a small water vapor permeation rate, for example, the design of the ionic liquid that serves as the CO2 carrier is changed from the conventional one, and a highly hydrophobic ionic liquid is used. The method of producing such a facilitated transport membrane is the same as that of the existing facilitated transport membrane, and the ionic liquid to be impregnated is changed. The synthesis method of the ionic liquid is also the same as that used for the conventional facilitated transport membrane, and it is sufficient to change the raw material. (2) As for the use of a highly gas-permeable polymer membrane with high CO2 / N2 permeation selectivity, a method of stacking a polymer membrane with a high CO2 and N2 permeation rate but a low water vapor permeation rate and a facilitated transport membrane to use as a composite membrane can be mentioned. As such a polymer membrane, for example, a PIM membrane (Bibiana Comesana-Ga'ndara et al., Energy Environ. Sci., 2019, 12, 2733 (DOI: 10.1039 / c9ee01384a)) is expected to be used. A three-stage process was used as shown in Figure 19, with the first stage being a PIM membrane and the second and third stages being facilitated transport membranes. The size of the membrane module was 5 cm high, 10.5 cm wide, and 20 cm deep, with 250 PIM membranes, 300 facilitated transport membranes in the second stage, and 30 in the third stage. The overall size was 0.66 m 3 (Membrane module (580 pieces) 609,000 cm 3 and a three-stage process vacuum pump and booster (three of each, 7500 x 2 x 3 = 45,000 cm 3 ) together is approximately 0.66m 3 In Example 4, the facilitated transport membrane was assumed to have a water vapor permeability coefficient of 10,000 barrer. Furthermore, in Example 4, the CO2 / N2 permeation selectivity of the PIM membrane was set to 15.

[0113] (calculation conditions) The PIM membrane had a CO2 permeation rate of 10,000 barrer, a CO2 / N2 permeation selectivity of 15, a membrane thickness of 1 μm, and a water vapor permeability coefficient of 500,000 barrer. The facilitated transport membrane had a CO2 permeation rate dependent on temperature, CO2 partial pressure, and water vapor fraction, a CO2 / N2 permeation selectivity dependent on temperature, CO2 partial pressure, and water vapor fraction, a membrane thickness of 20 μm, and a water vapor permeability coefficient of 10,000 barrer. The raw gas was air (CO2 concentration 400 ppm, temperature 25°C, relative humidity 50%). The permeating gas is heated so that the gas temperature in the second and third stages is a temperature at which water vapor does not condense under atmospheric pressure.

[0114] The membrane area (m ) of the first-stage membrane module of the CO2 recovery method of Example 4 2 The graph showing the relationship between the CO2 recovery rate (%) and the CO2 purity (%) is shown in FIG. 20 (left side). 2 ) and the CO2 recovery rate (%) and CO2 purity (%) are shown in FIG. 20 (right side).

[0115] As is clear from the results shown in FIG. 20, the CO2 recovery rates in the first stage (PIM membrane) in Example 1 and Example 4 are equivalent, but the CO2 concentration in the permeated gas in Example 4 is approximately twice that of Example 1.

[0116] The membrane area (m2) of the second-stage membrane module in the CO2 capture method of Example 4 2 The graph showing the relationship between the membrane area (m2) in the second stage (AAIL-SILM) of the CO2 capture method in Example 1 and the CO2 purity (%) is shown in FIG. 2 ) and the CO2 recovery rate (%) and CO2 purity (%) are shown in FIG. 21 (right side).

[0117] As is clear from the results shown in FIG. 21, both the CO2 capture rate and the CO2 concentration in the permeable gas are higher in Example 4 than in Example 1. In Example 4, a CO2 capture rate of 90% can be achieved with 300 modules. In Example 1, 1000 modules are required. In Example 4, the CO2 purity in the permeable gas at a CO2 capture rate of 90% is 56.5% (dry). In Example 1, it is 26.1% (dry).

[0118] The membrane area (m ) of the third membrane module in the CO2 recovery method of Example 4 2 The graph showing the relationship between the membrane area (m2) in the third stage (AAIL-SILM) of the CO2 capture method in Example 1 and the CO2 purity (%) is shown in FIG. 2 ) is plotted on the right side of FIG. 22.

[0119] As is clear from the results shown in Figure 22, both the CO2 capture rate and the CO2 concentration in the permeable gas are higher in Example 4 than in Example 1. In Example 4, the CO2 purity in the permeable gas at a CO2 capture rate of 90% is extremely high at 93.8 (dry), compared to 85.8 (dry) in Example 1.

Claims

1. CO 2 Using a selectively permeable membrane, CO is extracted from the raw gas. 2 A method for recovering The raw material gas is mixed with a first CO 2 Step 1: contacting the gas with a selectively permeable membrane to obtain a first permeable gas; The first permeable gas is mixed with a second CO 2 a step 2 of contacting the gas with a selectively permeable membrane to obtain a second permeable gas; Equipped with In the step 1, the raw material gas is CO 2 The concentration is 100 to 10,000 ppm, and the water vapor fraction is 1 to 10%, In the step 1, the first CO 2 a water vapor fraction of the first permeable gas is increased to be higher than the water vapor fraction of the raw material gas by a selectively permeable membrane; In the step 2, the second CO 2 A selectively permeable membrane is a facilitated transport membrane, In the step 2, the second CO 2 The second permeable gas, CO 2 The purity of the first permeable gas is determined by the 2 Higher than purity, CO 2 Recovery method.

2. The CO method according to claim 1, wherein the steps 1 and 2 are carried out in a temperature range of 1 to 200° C. 2 Recovery method.

3. 3. The CO 2 according to claim 1, wherein the water vapor permeability coefficient of the facilitated transport membrane is 500,000 barrer or less. 2 Recovery method.

4. The first CO 2 The surface area of ​​the selectively permeable membrane is 5 to 100 m 2 and the second CO 2 The surface area of ​​the selectively permeable membrane is 2 to 200 m 2 The CO according to claim 1 or 2, 2 Recovery method.

5. The second permeation gas is CO 2 3. The CO according to claim 1 or 2, having a purity of 10% or more. 2 Recovery method.

6. CO from raw gas 2 Used to recover CO 2 A recovery device comprising: a first CO 2 gas for contacting the raw material gas to obtain a first permeable gas; 2 A selectively permeable membrane; a second CO 2 gas for contacting the first permeable gas to obtain a second permeable gas; 2 A selectively permeable membrane; Equipped with The first CO 2 a water vapor fraction of the first permeable gas is increased to be higher than a water vapor fraction of the feed gas by a selectively permeable membrane; The second CO 2 A selectively permeable membrane is a facilitated transport membrane, The second CO 2 The second permeable gas, CO 2 The purity of the first permeable gas is 2 Purity is increased by CO 2 Recovery device.

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