Gas separation system

Abstract

Provided is a novel gas separation system suitable for reducing recovery power. A gas separation system (100) is provided with: a combustion device (10) to which a first gas (G1) containing oxygen is supplied and which discharges a second gas (G2) containing carbon dioxide; a second gas circulation path (64) for conveying at least a portion of the second gas (G2) to the combustion device (10); and a gas separation device (20) that separates the second gas (G2) and obtains a third gas (G3) having a higher carbon dioxide content than the second gas (G2).

Description

Technical Field

[0001] The present invention relates to gas separation systems. Background Art

[0002] In recent years, the technology of separating and recovering carbon dioxide contained in the exhaust gas discharged from combustion devices such as boilers has attracted attention. For example, Patent Document 1 proposes a technology of removing CO2 and SO2 from the exhaust gas by separating the exhaust gas of the boiler using a membrane separation unit in a reduced pressure mode.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application No. 2020-501884 Summary of the invention

[0006] Problems to be solved by the invention

[0007] The system described in Patent Document 1 adopts a decompression type membrane separation unit to separate exhaust gas from a boiler. In the system configuration of Patent Document 1, a large recovery power is required to separate carbon dioxide.

[0008] An object of the present invention is to provide a new gas separation system suitable for reducing recovery power.

[0009] Means for solving problems

[0010] The present invention provides a gas separation system, which comprises:

[0011] a combustion device which is supplied with a first gas containing oxygen and discharges a second gas containing carbon dioxide;

[0012] a second gas circulation path for conveying at least a portion of the second gas to the combustion device; and

[0013] A gas separation device separates the second gas to obtain a third gas having a higher carbon dioxide content than the second gas.

[0014] Effects of the Invention

[0015] According to the present invention, a new gas separation system suitable for reducing recovery power can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] [ Figure 1 ] is a schematic diagram showing an example of the gas separation system of the present embodiment.

[0017] [ Figure 2] is a schematic cross-sectional view showing an example of a gas separation device provided in a gas separation system.

[0018] [ Figure 3 ] is a schematic cross-sectional view showing an example of a separation membrane provided in a gas separation device.

[0019] [ Figure 4 ] is an expanded stereoscopic view showing a modified example of the gas separation device provided in the gas separation system.

[0020] [ Figure 5 ] is a schematic diagram showing the structure of the gas separation system used in calculation example 6.

[0021] [ Figure 6 ] is a schematic diagram showing the structure of the gas separation system used in calculation example 7.

[0022] [ Figure 7 ] is a graph showing the relationship between the carbon dioxide recovery power and the content of carbon dioxide in the second gas based on the simulation results of calculation examples 1 to 5. DETAILED DESCRIPTION

[0023] A gas separation system according to a first aspect of the present invention includes:

[0024] a combustion device which is supplied with a first gas containing oxygen and discharges a second gas containing carbon dioxide;

[0025] a second gas circulation path for conveying at least a portion of the second gas to the combustion device; and

[0026] A gas separation device separates the second gas to obtain a third gas having a higher carbon dioxide content than the second gas.

[0027] Regarding a second aspect of the present invention, for example, in the gas separation system according to the first aspect, the gas separation device includes a separation membrane that separates the second gas.

[0028] Regarding a third aspect of the present invention, for example, in the gas separation system according to the first or second aspect, the combustion device includes a boiler.

[0029] Regarding a fourth aspect of the present invention, for example, in the gas separation system according to any one of the first to third aspects, the content of carbon dioxide in the second gas is 20 vol% or more.

[0030] Regarding a fifth aspect of the present invention, for example, in the gas separation system according to the fourth aspect, the content of carbon dioxide in the second gas is 70 vol% or less.

[0031] Regarding a sixth aspect of the present invention, for example, in the gas separation system according to any one of the first to fifth aspects, the oxygen content in the first gas is 20 vol% or more.

[0032] According to a seventh aspect of the present invention, for example, in the gas separation system according to any one of the first to sixth aspects, a pressurizing device for pressurizing the second gas is further provided.

[0033] According to an eighth aspect of the present invention, for example, in the gas separation system according to any one of the first to seventh aspects, a gas supply unit for supplying the first gas to the combustion device is further provided.

[0034] Regarding a ninth aspect of the present invention, for example, in the gas separation system according to the eighth aspect, the gas supply unit includes a gas generating device that generates the first gas from air.

[0035] Hereinafter, the present invention will be described in detail, but the following description is not intended to limit the present invention to specific embodiments.

[0036] <Embodiment of Gas Separation System>

[0037] Figure 1 1 is a schematic diagram showing an example of a gas separation system 100 according to the present embodiment. The gas separation system 100 includes a combustion device 10, a gas separation device 20, and a second gas circulation path 64. The first gas G1 containing oxygen is supplied to the combustion device 10. The combustion device 10 discharges the second gas G2 containing carbon dioxide. The second gas circulation path 64 is a path for conveying at least a portion of the second gas G2 to the combustion device 10. The gas separation device 20 is a device for separating the second gas G2 to obtain a third gas G3 having a higher carbon dioxide content than the second gas G2.

[0038] The gas separation device 20 is not particularly limited as long as it can separate the second gas G2 to obtain the third gas G3 having a higher carbon dioxide content than the second gas G2. For example, the gas separation device 20 may be a device that uses a membrane separation method to separate the second gas G2 using a separation membrane to obtain the third gas G3, or may be a device that uses a physical adsorption method to separate the second gas G2 using an adsorbent to obtain the third gas G3. Physical adsorption methods include, for example, PSA (pressure swing adsorption; Pressure Swing Adsorption) method, TSA (temperature swing adsorption; Temperature Swing Adsorption) method, PTSA (pressure and temperature swing adsorption; Pressure and Temperature Swing Adsorption) method, etc. The PSA method, TSA method, and PTSA method are methods of separating gases using an adsorbent in which a chemical adsorption component such as potassium carbonate or amine is supported on a carrier such as activated carbon or a porous resin. In the PSA method, the gas is separated by using the difference in adsorption capacity caused by the pressure of the adsorbent. In the TSA method, the difference in adsorption capacity caused by the temperature of the adsorbent is used to separate the gas. In the PTSA method, the difference in adsorption capacity caused by the pressure and temperature of the adsorbent is used to separate the gas. When the gas separation device 20 adopts the physical adsorption method, the gas separation device 20 can adopt the PSA method.

[0039] When the gas separation device 20 adopts a membrane separation method, the gas separation device 20 may include a separation membrane 21 for separating the second gas G2. The second gas G2 is separated by the separation membrane 21, and the third gas G3 can be obtained.

[0040] In the present specification, a "combustion device" refers to a device that uses fuel gas to burn fuel and discharge exhaust gas. Examples of the combustion device 10 include boilers, incinerators, and internal combustion engines such as engines. The combustion device 10 is typically a boiler.

[0041] In the gas separation system 100 of the present embodiment, at least a portion of the second gas G2 can be transported to the combustion device 10 using the second gas circulation path 64. As a result, the content of carbon dioxide in the second gas G2 supplied to the gas separation device 20 of the rear stage can be increased. In this way, according to the gas separation system 100 of the present embodiment, even in a low carbon dioxide concentration range (for example, the carbon dioxide content of the exhaust gas is less than 10 vol%), carbon dioxide can be efficiently recovered using the gas separation device 20. Here, for the separation power of the gas separation device, it shows a tendency that the higher the content of carbon dioxide in the exhaust gas supplied, the lower the separation power. Therefore, according to the gas separation system 100, the recovery power of carbon dioxide can be reduced. In the present specification, "the recovery power of carbon dioxide" is the sum of the power required for recovering carbon dioxide. The recovery power of carbon dioxide of the gas separation system 100 includes the separation power of the gas separation device 20 per unit amount of carbon dioxide to be recovered.

[0042] The content of carbon dioxide in the second gas G2 supplied to the gas separation device 20 is preferably 20 vol% or more. If the content of carbon dioxide in the second gas G2 is 20 vol% or more, the separation power of the gas separation device 20 can be reduced. In the present specification, the content of carbon dioxide in the second gas G2 (vol%) is the volume ratio of carbon dioxide relative to the second gas G2 under the condition of standard state (0°C, 101.33 kPa).

[0043] The lower limit of the content of carbon dioxide in the second gas G2 supplied to the gas separation device 20 is preferably 25 vol%, and more preferably 30 vol%.

[0044] The carbon dioxide content in the second gas G2 supplied to the gas separation device 20 is preferably 70 vol% or less. When the carbon dioxide content in the second gas G2 is 70 vol% or less, the separation power of the gas separation device 20 can be more efficiently reduced.

[0045] The content of carbon dioxide in the second gas G2 supplied to the gas separation device 20 may be 65 vol% or less, 60 vol% or less, 55 vol% or less, or even 50 vol% or less.

[0046] [Combustion device]

[0047] The combustion device 10 uses the fuel gas to burn the fuel and discharges the second gas G2 as exhaust gas. Before at least a portion of the second gas G2 is delivered to the combustion device 10 via the second gas circulation path 64, the fuel gas is the first gas G1. After at least a portion of the second gas G2 is delivered to the combustion device 10 via the second gas circulation path 64, the fuel gas is a mixed gas G containing the first gas G1 and the second gas G2.

[0048] The fuel used in the combustion device 10 is not particularly limited. As the fuel, for example, liquid fuels such as petroleum, gaseous fuels such as natural gas, solid fuels such as coal and wood, special fuels such as waste, etc. can be cited. A fuel supply device (not shown) for supplying fuel can also be connected to the combustion device 10.

[0049] The combustion device 10 may include a burner for burning fuel, a fuel supply pipe for supplying fuel to the burner, and a fuel gas supply pipe for supplying the burner with a mixed gas G. In this case, in the combustion device 10, the fuel is burned using the mixed gas G supplied to the burner, thereby generating the second gas G2 containing carbon dioxide.

[0050] The oxygen content in the first gas G1 supplied to the combustion device 10 is preferably 20 vol% or more. If the oxygen content in the first gas G1 is 20 vol% or more, the carbon dioxide content in the second gas G2 discharged from the combustion device 10 can be increased. Therefore, the separation power of the gas separation device 20 can be reduced. In the present specification, the oxygen content (vol%) in the first gas G1 is the volume ratio of oxygen to the first gas G1 under standard conditions.

[0051] The lower limit of the oxygen content in the first gas G1 supplied to the combustion device 10 is preferably 25 vol%, and more preferably 30 vol%.

[0052] The upper limit of the oxygen content in the first gas G1 supplied to the combustion device 10 is not particularly limited. The upper limit of the oxygen content in the first gas G1 is, for example, 100 vol%. The oxygen content in the first gas G1 supplied to the combustion device 10 may be 90 vol% or less, 80 vol% or less, or 70 vol% or less.

[0053] [Gas separation device]

[0054] Figure 2 1 is a schematic cross-sectional view showing an example of a gas separation device 20 included in the gas separation system 100. Figure 2In the example of , the gas separation device 20 includes a separation membrane 21 for separating the supplied second gas G2. The third gas G3 obtained by the separation membrane 21 has a higher carbon dioxide content than the second gas G2.

[0055] The separation membrane 21 of the gas separation device 20 can be called a separation membrane 21 for separating the second gas G2 into the permeated gas S1 and the non-permeated gas S2. The permeated gas S1 may be the third gas G3, and the non-permeated gas S2 may be the third gas G3.

[0056] like Figure 2 As shown, the gas separation device 20 includes a separation membrane 21 and a container 22. The container 22 has a first chamber 23 and a second chamber 24. The first chamber 23 functions as a supply space to which the second gas G2 is supplied. The second chamber 24 functions as a permeation space to which the permeated gas S1 is supplied. The permeated gas S1 is obtained by the second gas G2 permeating through the separation membrane 21.

[0057] The separation membrane 21 is disposed inside the container 22. The separation membrane 21 partitions the inside of the container 22 into a first chamber 23 and a second chamber 24. The separation membrane 21 extends from one of a pair of wall surfaces of the container 22 to the other.

[0058] The first chamber 23 has a supply space inlet 23a and a supply space outlet 23b. The second chamber 24 has a permeation space outlet 24b. The supply space inlet 23a is an opening for supplying the second gas G2 to the supply space (the first chamber 23). The permeation space outlet 24b is an opening for discharging the permeation gas S1 from the permeation space (the second chamber 24). The supply space outlet 23b is an opening for discharging the second gas G2 (non-permeation gas S2) that has not permeated the separation membrane 21 from the supply space (the first chamber 23). The supply space inlet 23a, the supply space outlet 23b, and the permeation space outlet 24b are respectively formed on, for example, the wall surface of the container 22.

[0059] The gas separation device 20 is suitable for a flow-through (continuous) membrane separation method. The gas separation device 20 can also be used for a batch membrane separation method.

[0060] The structure of the separation membrane 21 is not particularly limited. Figure 3 To show Figure 2 FIG. 2 is a schematic cross-sectional view of an example of a separation membrane 21 included in the gas separation device 20 shown in FIG. Figure 3 As shown, the separation membrane 21 may include a separation functional layer 1, a porous support 3 supporting the separation functional layer 1, and an intermediate layer 2 disposed between the separation functional layer 1 and the porous support 3. The intermediate layer 2 is in direct contact with the separation functional layer 1 and the porous support 3, for example.

[0061] In a preferred embodiment of the present invention, the separation membrane 21 is a membrane (carbon dioxide separation membrane) that allows carbon dioxide contained in the second gas G2 to preferentially permeate. In this case, the content of carbon dioxide in the permeated gas S1 is higher than the content of carbon dioxide in the second gas G2. On the other hand, the content of carbon dioxide in the non-permeated gas S2 is lower than the content of carbon dioxide in the second gas G2. That is, when the separation membrane 21 is a carbon dioxide separation membrane, the permeated gas S1 corresponds to the third gas G3.

[0062] (Separation Functional Layer)

[0063] In the case where the separation membrane 21 is a carbon dioxide separation membrane, the separation functional layer 1 is a layer that allows carbon dioxide contained in the second gas G2 to preferentially pass through. The separation functional layer 1 preferably contains a resin. As the resin contained in the separation functional layer 1, for example, polyether block amide resins, polyamide resins, polyether resins, polyimide resins, polyetherimide resins, cellulose acetate resins, silicone resins and fluororesins can be cited. The separation functional layer 1 preferably contains a polyimide resin or a cellulose acetate resin, and more preferably contains a cellulose acetate resin. The separation functional layer 1 is preferably substantially formed of a resin. In the present specification, "substantially formed of..." means excluding other components that change the essential characteristics of the material, and means, for example, that more than 95wt%, and further more than 99wt% is composed of the material.

[0064] The thickness of the separation functional layer 1 is, for example, 50 μm or less, preferably 25 μm or less, and more preferably 15 μm or less. The thickness of the separation functional layer 1 may be 0.05 μm or more, or 0.1 μm or more.

[0065] (Middle layer)

[0066] The intermediate layer 2 includes, for example, a resin, and may further include nanoparticles dispersed in the resin (matrix). The nanoparticles may be separated from each other in the matrix, or may be partially aggregated. The material of the matrix is ​​not particularly limited, and examples thereof include silicone resins such as polydimethylsiloxane; fluororesins such as polytetrafluoroethylene; epoxy resins such as polyethylene oxide; polyimide resins; polysulfone resins; polyacetylene resins such as polytrimethylsilylpropyne and polydiphenylacetylene; and polyolefin resins such as polymethylpentene. The matrix preferably includes a silicone resin.

[0067] Nanoparticles may contain inorganic materials or organic materials. Examples of inorganic materials contained in nanoparticles include silicon dioxide, titanium dioxide, and aluminum oxide. Nanoparticles preferably contain silicon dioxide.

[0068] The thickness of the intermediate layer 2 is not particularly limited, and is, for example, less than 50 μm, preferably 40 μm or less, and more preferably 30 μm or less. The lower limit of the thickness of the intermediate layer 2 is not particularly limited, and is, for example, 1 μm. The intermediate layer 2 is, for example, a layer having a thickness of less than 50 μm.

[0069] (Porous Support)

[0070] The porous support 3 supports the separation functional layer 1 via the intermediate layer 2. Examples of the porous support 3 include nonwoven fabrics; porous polytetrafluoroethylene; aromatic polyamide fibers; porous metals; sintered metals; porous ceramics; porous polyesters; porous nylons; activated carbon fibers; latex; silicone resins; silicone rubbers; permeable (porous) polymers containing at least one selected from the group consisting of polyvinyl fluoride, polyvinylidene fluoride, polyurethane, polypropylene, polyethylene, polystyrene, polycarbonate, polysulfone, polyetheretherketone, polyacrylonitrile, polyimide, and polyphenylene ether; metal foams having open or closed cells; polymer foams having open or closed cells; silicon dioxide; porous glass; meshes, etc. The porous support 3 may be composed of a combination of two or more of these.

[0071] The porous support 3 has an average pore size of, for example, 0.01 to 0.4 μm. The thickness of the porous support 3 is not particularly limited, and is, for example, 10 μm or more, preferably 20 μm or more, and more preferably 50 μm or more. The thickness of the porous support 3 is, for example, 300 μm or less, preferably 200 μm or less, and more preferably 150 μm or less.

[0072] The structure of the separation membrane 21 is not limited to Figure 3 The example shown. The separation membrane 21 can be composed of, for example, a separation functional layer 1, and a porous support body 3 arranged on one side of the separation functional layer 1 to support the separation functional layer 1. The separation membrane 21 can be composed of, for example, a separation functional layer 1, a protective layer arranged on one side of the separation functional layer 1 to protect the separation functional layer 1, and a porous support body 3 arranged on the other side of the separation functional layer 1 to support the separation functional layer 1. As the protective layer, a layer containing the material described for the intermediate layer 2 can be used.

[0073] In another preferred embodiment of the present invention, the separation membrane 21 is a membrane (nitrogen separation membrane) that allows nitrogen contained in the second gas G2 to preferentially permeate. In this case, the content of carbon dioxide in the permeated gas S1 is lower than the content of carbon dioxide in the second gas G2. On the other hand, the content of carbon dioxide in the non-permeated gas S2 is higher than the content of carbon dioxide in the second gas G2. That is, when the separation membrane 21 is a nitrogen separation membrane, the non-permeated gas S2 corresponds to the third gas G3.

[0074] (Separation Functional Layer)

[0075] When the separation membrane 21 is a nitrogen separation membrane, the separation functional layer 1 is a layer that can preferentially permeate nitrogen contained in the second gas G2 .

[0076] (Middle layer)

[0077] As the intermediate layer 2 , the intermediate layers mentioned as the intermediate layer 2 in the case where the separation membrane 21 is a carbon dioxide separation membrane can be used.

[0078] (Porous Support)

[0079] As the porous support 3 , the porous support exemplified as the porous support 3 in the case where the separation membrane 21 is a carbon dioxide separation membrane can be used.

[0080] [Pressure device]

[0081] The gas separation system 100 may further include a pressurizing device 30 for pressurizing the second gas G2. When the gas separation system 100 includes the pressurizing device 30, the pressurizing device 30 may be disposed upstream of the gas separation device 20 and pressurize the supply space 23 of the gas separation device 20.

[0082] As described above, the separation power of the gas separation device shows a tendency to decrease as the content of carbon dioxide in the supplied exhaust gas increases. On the other hand, compared with the operation mode (decompression mode) in which a pressure difference is generated by reducing pressure from the permeation side of the gas separation device and the operation mode (pressurization mode) in which a pressure difference is generated by pressurizing from the supply side of the gas separation device, the lower the content of carbon dioxide in the supplied exhaust gas, the greater the difference in the required separation power. For example, the separation power required for exhaust gas with a carbon dioxide content of 10 vol% is 1.06 MWh / t-CO2 in the decompression mode, while it is 1.92 MWh / t-CO2 in the pressurization mode, which is a difference of nearly 2 times. Therefore, from the perspective of operating cost, in the past, the decompression mode was adopted in the gas separation device for treating exhaust gas with a carbon dioxide content of less than 10 vol% (such as the exhaust gas discharged from the boiler).

[0083] The inventors of the present application have found that the above-mentioned difference in separation power tends to be eliminated as the content of carbon dioxide in the exhaust gas supplied to the gas separation device becomes higher. For example, the separation power required for exhaust gas with a carbon dioxide content of 50 vol% is 0.16 MWh / t-CO2 in both the decompression method and the pressurization method. Based on the above findings, the inventors of the present application have considered adopting a pressurization method in the gas separation device 20 of the gas separation system 100 of the present embodiment. Compared with the decompression method, the membrane area required for the pressurization method is small. Therefore, by adopting a pressurization method in the gas separation device 20 of the gas separation system 100 of the present embodiment, not only can the increase in separation power be suppressed, but also the required membrane area can be greatly reduced. As a result, the overall compactness of the system can be achieved.

[0084] The pressurizing device 30 may be a pump that pressurizes the second gas G2 to the supply space 23 of the gas separation device 20. Typically, the pump is a gas delivery pump, and examples include a reciprocating pump, a rotary pump, and the like. Examples of reciprocating pumps include diaphragm pumps and swing piston pumps. Examples of rotary pumps include liquid seal pumps; oil rotary pumps (rotary pumps); mechanical booster pumps; various dry pumps such as Roots type, claw type, screw type, turbine type, and vortex type. The pump as the pressurizing device 30 may also have a variable speed mechanism for changing the rotation speed, etc. An example of a variable speed mechanism is an inverter that drives the motor of the pump. By controlling the rotation speed of the pump, etc. using a variable speed mechanism, the pressure in the supply space 23 of the gas separation device 20 can be appropriately adjusted.

[0085] [Gas supply unit]

[0086] The gas separation system 100 may further include a gas supply unit 40 that supplies the first gas G1 to the combustion device 10. When the gas separation system 100 includes the gas supply unit 40, the gas supply unit 40 may be connected to the combustion device 10.

[0087] The gas supply unit 40 may be a tank or a gas cylinder storing the first gas G1 . Such a tank or a gas cylinder may be connected to the combustion device 10 .

[0088] The gas supply unit 40 may include a gas generating device that generates the first gas G1 from air. The gas generating device may be connected to the combustion device 10. The first gas G1 generated by the gas generating device may be configured to be stored in the above-mentioned gas tank or gas cylinder. As long as the first gas G1 can be generated from air, the configuration of the gas generating device is not particularly limited. The gas generating device generates the oxygen-containing first gas G1 by, for example, separating oxygen from air. The gas generating device may also generate the oxygen-containing first gas G1 by separating air into inert gases such as oxygen and nitrogen. The oxygen content in the first gas G1 generated by the gas generating device is, for example, 20 vol% or more.

[0089] The gas generating device may adopt the PSA (Pressure Swing Adsorption) method or the PVSA (Pressure Vacuum Swing Adsorption) method. When the PSA method is adopted, the gas generating device can be made compact and the installation area can be reduced compared to the PVSA method. When the PVSA method is adopted, the operating cost can be suppressed compared to the PVSA method. The gas generating device may separate oxygen from the air using a separation membrane. As the separation membrane of the gas generating device, for example, the separation membrane described for the separation membrane 21 of the gas separation device 20 may be used.

[0090] [Gas Path]

[0091] The gas separation system 100 may further include a first gas supply path 61 , a second gas circulation path 64 , a permeated gas exhaust path 65 , and a non-permeated gas exhaust path 66 as gas paths in addition to the second gas circulation path 64 .

[0092] The first gas supply path 61 is a path for supplying the first gas G1 from the gas supply unit 40 to the combustion device 10 during operation, and is connected to the outlet 40b of the gas supply unit 40 and the first gas inlet 10a of the combustion device 10. The second gas supply path 62 is a path for supplying the second gas G2 from the combustion device 10 to the gas separation device 20 during operation, and is connected to the second gas outlet 10b of the combustion device 10 and the supply space inlet 23a of the gas separation device 20.

[0093] exist Figure 1 In the example, the second gas supply path 62 has a first portion 62A and a second portion 62B. The first portion 62A is a portion connecting the second gas outlet 10b of the combustion device 10 and the branch position 63, and the second portion 62B is a portion connecting the branch position 63 and the supply space inlet 23a of the gas separation device 20. Figure 1In the example of FIG. 1 , the second gas circulation path 64 branches from the second gas supply path 62 at the branch position 63 and is connected to the second gas inlet 10c of the combustion device 10. However, the connection position of the second gas circulation path 64 is not limited to Figure 1 For example, the second gas circulation path 64 may be branched from the second gas outlet 10 b of the burner 10 and connected to the second gas inlet 10 c of the burner 10 .

[0094] The second gas circulation path 64 is a path for conveying at least a portion of the second gas G2 discharged from the combustion device 10 to the combustion device 10 during operation. That is, during operation, the second gas G2 is mixed with the first gas G1 in the combustion device 10 and circulated in the first portion 62A of the second gas supply path 62 and the second gas circulation path 64. By circulating at least a portion of the second gas G2 in the combustion device 10, the content of carbon dioxide in the second gas G2 supplied to the gas separation device 20 can be increased. The content of carbon dioxide in the second gas G2 supplied to the gas separation device 20 is, for example, 20 vol% or more and 70 vol% or less.

[0095] The permeated gas discharge path 65 is a path for discharging the permeated gas S1 from the gas separation device 20 during operation, and is connected to the permeation space outlet 24b of the gas separation device 20. For example, a pump for controlling the flow rate of the permeated gas S1 may be disposed in the permeated gas discharge path 65. The non-permeated gas discharge path 66 is a path for discharging the non-permeated gas S2 from the gas separation device 20 during operation, and is connected to the supply space outlet 23b of the gas separation device 20. For example, a pump for controlling the flow rate of the non-permeated gas S2 may be disposed in the non-permeated gas discharge path 66.

[0096] exist Figure 1 In the example of FIG. 6 , the pressurizing device 30 is disposed in the second portion 62B of the second gas supply path 62 . The pressurizing device 30 can pressurize the inside of the supply space 23 of the gas separation device 20 .

[0097] A pressurizing device (not shown) may be disposed in the second gas circulation path 64. By disposing the pressurizing device in the second gas circulation path 64, the second gas G2 circulating in the combustion device 10 can be pressurized.

[0098] Unless otherwise specified, each gas path of the gas separation system 100 is formed of a pipe made of metal or resin, for example.

[0099] The gas separation system 100 may further include a control device 50 for controlling the various components of the gas separation system 100. The control device 50 is, for example, a DSP (digital signal processor) including an A / D conversion circuit, an input / output circuit, an operation circuit, a storage device, etc. A program for properly operating the gas separation system 100 is stored in the control device 50. For example, the control device 50 can adjust the pressure in the supply space 23 of the gas separation device 20 by controlling the operation of the pressurizing device 30, thereby pressurizing the second gas G2.

[0100] In this embodiment, the carbon dioxide content in the third gas G3 (permeated gas S1 or non-permeated gas S2) obtained by the gas separation system 100 is, for example, 95 vol% or more. Thus, by using the gas separation system 100, high-purity carbon dioxide can be recovered.

[0101] The gas separation system 100 may further include a recovery unit (not shown) for recovering the carbon dioxide separated by the gas separation device 20. The configuration of the recovery unit is not particularly limited. When the separation membrane 21 of the gas separation device 20 is a carbon dioxide separation membrane, a permeate gas discharge path 65 is connected to the inlet of the recovery unit. When the separation membrane 21 of the gas separation device 20 is a nitrogen separation membrane, a non-permeate gas discharge path 66 is connected to the inlet of the recovery unit.

[0102] The recovery unit may include a liquefaction unit that liquefies the third gas G3. That is, the recovery unit may liquefy the carbon dioxide separated by the gas separation device 20 and recover the carbon dioxide in a liquid state.

[0103] The recovery unit may include a solidification unit that solidifies the third gas G3. That is, the recovery unit may solidify the carbon dioxide separated by the gas separation device 20 and recover it in a solid (dry ice) state.

[0104] The utilization method of the carbon dioxide recovered by the gas separation system 100 of the present embodiment is not particularly limited. For example, the carbon dioxide recovered to the recovery unit in a liquid state can be taken out from the recovery unit and maintained in a liquid state for utilization. The carbon dioxide recovered to the recovery unit in a gaseous state can be taken out from the recovery unit and maintained in a gaseous state for utilization. The carbon dioxide recovered to the recovery unit in a solid state can be taken out from the recovery unit and maintained in a solid (dry ice) state for utilization. The recovered carbon dioxide can be reused as a carbon resource (carbon compound).

[0105] <Embodiment of the method for operating the gas separation system>

[0106] The operating method of the gas separation system 100 includes: supplying a first gas G1 containing oxygen to the combustion device 10, and discharging a second gas G2 containing carbon dioxide from the combustion device 10 (step ST1); passing through the second gas circulation path 64 and delivering at least a portion of the second gas G2 to the combustion device 10 (step ST2); and using the gas separation device 20 to separate the second gas G2 to obtain a third gas G3 having a higher carbon dioxide content than the second gas G2 (step ST3).

[0107] In step ST1, first, the first gas G1 is supplied to the combustion device 10. The oxygen content in the first gas G1 is, for example, 20 vol% or more. By burning the fuel in the combustion device 10, the second gas G2 containing carbon dioxide is generated. The generated second gas G2 is discharged from the combustion device 10.

[0108] In step ST2, at least a portion of the second gas G2 exhausted from the combustion device 10 is fed to the combustion device 10. This can increase the content of carbon dioxide in the second gas G2 supplied to the gas separation device 20. The content of carbon dioxide in the second gas G2 supplied to the gas separation device 20 is, for example, 20 vol% or more and 70 vol% or less.

[0109] In step ST3, the second gas G2 is separated by the gas separation device 20 to obtain the third gas G3. When the gas separation device 20 has a separation membrane 21, the second gas G2 is separated by the separation membrane 21 to obtain the third gas G3. Regarding the specific implementation method of step ST3, taking the case where the gas separation device 20 has a separation membrane 21 and the separation membrane 21 is a carbon dioxide separation membrane as an example, refer to Figure 2 and Figure 3 In step ST3 , first, the second gas G2 is supplied from the supply space inlet 23a to the supply space 23 of the gas separation device 20 . This allows the second gas G2 to contact one surface (eg, the main surface 21a ) of the separation membrane 21 .

[0110] Next, preferably, the space adjacent to one side surface of the separation membrane 21 is pressurized while the second gas G2 is in contact with one side surface of the separation membrane 21. That is, step ST3 preferably includes pressurizing the second gas G2 using a pressurizing device 30. In detail, the pressurizing device 30 is used to pressurize the supply space 23 from the supply space inlet 23a. The pressure in the supply space 23 is, for example, 200 kPa or more, and may be 400 kPa or more, 600 kPa or more, 800 kPa or more, 1000 kPa or more, or 1500 kPa or more. The pressure in the supply space 23 is preferably in the range of 300 kPa to 900 kPa.

[0111] By pressurizing the supply space 23 with the pressurizing device 30, the third gas G3, that is, the permeated gas S1 with a high carbon dioxide content can be obtained on the other side surface (e.g., the main surface 21b) of the separation membrane 21. In other words, the permeated gas S1 is supplied to the permeation space 24. The permeated gas S1 passes through the permeation space outlet 24b and is discharged to the outside of the gas separation device 20.

[0112] On the other hand, the carbon dioxide content in the second gas G2 gradually decreases from the supply space inlet 23a to the supply space outlet 23b of the supply space 23. The second gas G2 processed in the supply space 23, i.e., the non-permeated gas S2, passes through the supply space outlet 23b and is discharged to the outside of the gas separation device 20.

[0113] In step ST3, carbon dioxide contained in the second gas G2 can be preferentially permeated by the separation membrane 21 of the gas separation device 20. Therefore, the carbon dioxide content of the permeated gas S1 obtained by the operation of the gas separation device 20 is higher than that of the second gas G2 supplied to the gas separation device 20. The ratio of the carbon dioxide content (wt%) in the permeated gas S1 to the carbon dioxide content (wt%) in the second gas G2 supplied to the gas separation device 20 is not particularly limited.

[0114] According to step ST3, for example, the third gas G3, that is, the permeated gas S1 having a high carbon dioxide content can be produced. In other words, according to step ST3, carbon dioxide can be obtained as the permeated gas S1.

[0115] The operating method of the gas separation system 100 may further include recovering carbon dioxide through a recovery unit (step ST4). Step ST4 may include liquefying the third gas G3 through a liquefaction unit. That is, step ST4 may include recovering the carbon dioxide separated by the gas separation device 20 in a liquid state by liquefying it. Step ST4 may include storing the third gas G3 through a storage unit. That is, step ST4 may include recovering the carbon dioxide separated by the gas separation device 20 in a gaseous state. The storage unit is, for example, a tank or a gas cylinder for storing carbon dioxide. The tank or the gas cylinder may have a porous material as an adsorbent, such as activated carbon, zeolite, metal organic structure (MOF), etc. Step ST4 may include solidifying the third gas G3 through a solidification unit. That is, step ST4 may include recovering the carbon dioxide separated by the gas separation device 20 in a solid (dry ice) state.

[0116] The utilization method of the carbon dioxide recovered by step ST4 is not particularly limited. For example, the carbon dioxide recovered in a liquid state can be utilized while maintaining the liquid state. The carbon dioxide recovered in a gaseous state can be utilized while maintaining the gaseous state. The carbon dioxide recovered in a solid state can be utilized while maintaining the solid (dry ice) state. The recovered carbon dioxide can be reused as a carbon resource (carbon compound).

[0117] According to the method of operating the gas separation system 100 of the present embodiment, it is possible to reduce the power required to recover carbon dioxide.

[0118] [Variations of the Gas Separation Device]

[0119] When the gas separation device 20 has the separation membrane 21 , the gas separation device 20 may be a spiral membrane element, a hollow fiber membrane element, a coil-type membrane element in which a plurality of pervaporation membranes are stacked, a plate-and-frame membrane element, or the like. Figure 4 FIG. 2 is a schematic diagram showing an expanded stereogram of a spiral membrane element. The gas separation device 20 can be Figure 4 The spiral membrane element shown. Figure 4 The gas separation device 20 (membrane element) includes a central tube 26 and a membrane leaf 27 having a separation membrane 21 and wound around the central tube 26 .

[0120] The center tube 26 has a cylindrical shape. A through hole 26h is formed on the surface of the center tube 26 for allowing the permeating gas S1 to flow into the center tube 26. The number of through holes 26h is not particularly limited, and may be one or more than two. Examples of the material of the center tube 26 include resins such as acrylonitrile / butadiene / styrene copolymer resin (ABS resin), polyphenylene ether resin (PPE resin), and polysulfone resin (PSF resin); and metals such as stainless steel and titanium. The inner diameter of the center tube 26 is, for example, in the range of 20 to 100 mm.

[0121] The gas separation device 20 has a plurality of membrane leaves 27. Each membrane leaf 27 includes a separation membrane 21 and a permeate side flow path material 29. For example, the membrane leaf 27 has two layers of separation membranes 21. The two separation membranes 21 overlap each other and are sealed at three sides in a bag-like structure. The permeate side flow path material 29 is arranged between the two separation membranes 21 so as to be located inside the bag-like structure. The permeate side flow path material 29 ensures a space (permeate space) between the two separation membranes 21 as a flow path for the permeated gas S1. In this way, the permeate side flow path material 29 is used in combination with the separation membrane 21. The number of membrane leaves 27 is not particularly limited, and is, for example, 2 to 30.

[0122] The gas separation device 20 further includes a supply side flow path material 28. The supply side flow path material 28 is located outside the bag-like structure and is stacked on the membrane leaf 27. Specifically, a plurality of supply side flow path materials 28 and a plurality of membrane leaves 27 are alternately stacked. The supply side flow path material 28 ensures a space (supply space) between the membrane leaves 27 as a flow path for the second gas G2.

[0123] As the supply side flow path material 28 and the permeate side flow path material 29, for example, a net, woven fabric or knitted fabric made of a resin obtained from polyethylene, polypropylene, polyethylene terephthalate (PET), polyphenylene sulfide (PPS) or ethylene-chlorotrifluoroethylene copolymer (ECTFE) can be used.

[0124] The outer peripheral surface of the membrane element is formed by a shell (not shown) made of a material that does not allow gas to pass through. The shell can be made of FRP (fiber reinforced plastic). The membrane element can be accommodated in a housing (not shown).

[0125] Figure 4 The gas separation device 20 (membrane element) can be operated, for example, by the following method. First, the second gas G2 is supplied to one end of the wound membrane leaf 27. The space in which the membrane leaf 27 is accommodated is pressurized. The pressurization can be performed by a pressurizing device 30. As a result, the permeated gas S1 that permeates the separation membrane 21 of the membrane leaf 27 moves to the inside of the central tube 26. The permeated gas S1 passes through the central tube 26 and is discharged to the outside. The non-permeated gas S2 treated by the gas separation device 20 is discharged to the outside from the other end of the wound membrane leaf 27.

[0126] The descriptions of the above-mentioned embodiments can be applied to each other as long as there is no technical contradiction. Furthermore, the above-mentioned embodiments and modifications can be combined with each other as long as there is no technical contradiction.

[0127] Example

[0128] Hereinafter, the present invention will be described in more detail using calculation examples, but the present invention is not limited thereto.

[0129] (Calculation Example 1)

[0130] A carbon dioxide separation membrane with a CO2 permeation rate of 800 GPU, a N2 permeation rate of 26.6 GPU, and a separation coefficient α of 30 was used to separate the Figure 1 The gas separation system 100 shown in the figure is simulated during operation. Specifically, in the gas separation system 100, it is assumed that the above-mentioned carbon dioxide separation membrane is used as the separation membrane provided in the gas separation device 20. The gas separation system 100 includes a combustion device 10, a gas separation device 20, a pressurizing device 30, and the like.

[0131] In the operation of the gas separation device 20 of calculation example 1, it is assumed that: the first gas G1 is supplied from the gas supply unit 40 to the combustion device 10; a portion of the second gas G2 is passed through the second gas circulation path 64 and transported to the combustion device 10, thereby making the carbon dioxide content in the second gas G2 supplied to the gas separation device 20 20 vol%; and the supply space 23 of the gas separation device 20 is pressurized by the pressurizing device 30.

[0132] In Calculation Example 1, the recovery power of carbon dioxide (MWh / t-CO2) and the number of required membranes were calculated under the following assumptions. Symmetry, a process simulation software manufactured by Schlumberger, was used for the calculation.

[0133] <Assumptions>

[0134] The content of carbon dioxide in the third gas G3 (permeated gas S1) exhausted from the gas separation device 20 was 95 vol%.

[0135] The recovery rate of carbon dioxide using the gas separation system 100 was 90 wt %.

[0136] (Calculation Example 2)

[0137] The carbon dioxide recovery power and the required number of membranes were calculated under the same conditions as in Calculation Example 1 except that the carbon dioxide content in the second gas G2 supplied to the gas separation device 20 was assumed to be 25 vol %.

[0138] (Calculation Example 3)

[0139] The carbon dioxide recovery power and the required number of membranes were calculated under the same conditions as in Calculation Example 1 except that the carbon dioxide content in the second gas G2 supplied to the gas separation device 20 was assumed to be 33 vol %.

[0140] (Calculation Example 4)

[0141] The carbon dioxide recovery power and the required number of membranes were calculated under the same conditions as in Calculation Example 1 except that the carbon dioxide content in the second gas G2 supplied to the gas separation device 20 was assumed to be 50 vol %.

[0142] (Calculation Example 5)

[0143] The carbon dioxide recovery power and the required number of membranes were calculated under the same conditions as in Calculation Example 1 except that the carbon dioxide content in the second gas G2 supplied to the gas separation device 20 was assumed to be 65 vol %.

[0144] (Calculation Example 6)

[0145] The same carbon dioxide separation membrane as in Calculation Example 1 was used to perform Figure 5 The simulation of the operation of the gas separation system 200 shown in FIG. 2 is performed. Specifically, in the gas separation system 200, it is assumed that the above-mentioned carbon dioxide separation membrane is used as the separation membrane provided in the gas separation device 80. The gas separation system 200 includes a combustion device 70, a gas separation device 80, and a pressurizing device 90. The gas separation system 200 is different from the combustion device 70 in that it does not include a gas supply unit for supplying the first gas G1 to the combustion device 70 and a second gas circulation path for conveying at least a part of the second gas G2 to the combustion device 70. Figure 1 The gas separation system 100 shown is different.

[0146] In the operation of the gas separation device 80 of Calculation Example 6, it is assumed that the carbon dioxide content in the second gas G2 supplied to the gas separation device 80 is less than 10 vol % and the supply space of the gas separation device 80 is pressurized by the pressurizing device 90 .

[0147] In Calculation Example 6, the recovery power of carbon dioxide and the number of required membranes were calculated under the following assumptions. Symmetry, a process simulation software manufactured by Schlumberger, was used for the calculation.

[0148] <Assumptions>

[0149] The content of carbon dioxide in the third gas G3 (permeated gas S1) exhausted from the gas separation device 80 was 95 vol%.

[0150] The recovery rate of carbon dioxide using the gas separation system 200 was 90 wt %.

[0151] (Calculation Example 7)

[0152] The same carbon dioxide separation membrane as in Calculation Example 1 was used to perform Figure 6 The simulation of the operation of the gas separation system 300 shown in FIG. 1 is performed. Specifically, in the gas separation system 300, it is assumed that the above-mentioned carbon dioxide separation membrane is used as the separation membrane provided in the gas separation device 80. The gas separation system 300 is similar to the gas separation system 80 in that a pressure reducing device 91 for reducing pressure from the permeation side of the gas separation device 80 is provided instead of the pressurizing device 90. Figure 5 The gas separation system 200 shown is different.

[0153] In the operation of the gas separation device 80 of Calculation Example 7, it is assumed that the carbon dioxide content in the second gas G2 supplied to the gas separation device 80 is less than 10 vol % and the pressure in the permeation space of the gas separation device 80 is reduced by the pressure reducing device 91 .

[0154] In Calculation Example 7, the recovery power of carbon dioxide and the number of required membranes were calculated under the following assumptions. Symmetry, a process simulation software manufactured by Schlumberger, was used for the calculation.

[0155] <Assumptions>

[0156] The content of carbon dioxide in the third gas G3 (permeated gas S1) exhausted from the gas separation device 80 was 95 vol%.

[0157] The recovery rate of carbon dioxide using the gas separation system 300 was 90 wt %.

[0158] It should be noted that, for calculation examples 1 to 5, the sum of the separation power of the gas separation device 20 and the power consumption of the gas supply unit 40 is regarded as the power for recovering carbon dioxide. As the power consumption of the gas supply unit 40, the power consumption of the PVSA type oxygen generation device provided by Shinko AirTech is referred to. For calculation examples 6 to 7, the separation power of the gas separation device 80 is regarded as the power for recovering carbon dioxide.

[0159] The simulation results of calculation examples 1 to 7 are shown in Table 1. The relationship between the carbon dioxide recovery power based on the simulation results of calculation examples 1 to 5 and the content rate of carbon dioxide in the second gas G2 is shown in Table 1. Figure 7 middle.

[0160] [Table 1]

[0161]

[0162] According to the comparison of the simulation results of calculation examples 1 to 5 and calculation examples 6 to 7 in Table 1, it can be seen that Figure 1 When the gas separation system 100 is operated, the power for recovering carbon dioxide can be greatly reduced. Comparison of the simulation results of Calculation Examples 1 to 6 with Calculation Example 7 shows that the number of required membranes can be greatly reduced when a pressurization method is used in the gas separation device.

[0163] In addition, according to Figure 5It can be seen that the recovery power of carbon dioxide shows a tendency that the higher the content of carbon dioxide in the second gas G2 supplied to the gas separation device, the lower the recovery power, but when the content of carbon dioxide in the second gas G2 exceeds 50 vol%, the recovery power of carbon dioxide remains roughly the same. Based on this result, it can be considered that the recovery power of carbon dioxide can be more efficiently reduced, especially when the content of carbon dioxide in the second gas G2 supplied to the gas separation device is 50 vol% or less.

[0164] Industrial Applicability

[0165] The gas separation system of the present embodiment is suitable for efficiently recovering carbon dioxide from exhaust gas (discharged from a combustion device).

Claims

1. A gas separation system comprising: a combustion device which is supplied with a first gas containing oxygen and discharges a second gas containing carbon dioxide; a second gas circulation path for conveying at least a portion of the second gas to the combustion device; and A gas separation device separates the second gas to obtain a third gas having a higher carbon dioxide content than the second gas.

2. The gas separation system according to claim 1, wherein: The gas separation device includes a separation membrane for separating the second gas.

3. The gas separation system according to claim 1, wherein: The combustion device comprises a boiler.

4. The gas separation system according to claim 1, wherein: The content of carbon dioxide in the second gas is 20 vol% or more.

5. The gas separation system according to claim 4, wherein: The content of carbon dioxide in the second gas is 70 vol% or less.

6. The gas separation system according to claim 1, wherein: The oxygen content in the first gas is 20 vol% or more. 7 . The gas separation system according to claim 1 , further comprising a pressurizing device for pressurizing the second gas. 8 . The gas separation system according to claim 1 , further comprising a gas supply unit for supplying the first gas to the combustion device.

9. The gas separation system of claim 8, wherein: The gas supply unit includes a gas generating device that generates the first gas from air.

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