Gas separation system and gas separation method using same

Abstract

[Problem] To provide a novel gas separation system using a gas separation membrane that contains a glassy polymer. [Solution] This gas separation system comprises: a first gas separation membrane unit having a first gas separation membrane that includes a first support layer and a first separation function layer which is disposed on the first support layer and contains a glassy polymer, a first gas supply port and a first non-permeated gas discharge port that are disposed on one surface side of the first gas separation membrane, and a first permeated gas discharge port that is disposed on the other surface side of the first gas separation membrane; a first gas pressure-feeding means for pressure-feeding a raw-material gas to the first gas supply port, the first gas pressure-feeding means being disposed upstream of the first gas supply port; a first gas flow path connecting the first gas pressure-feeding means and the first gas supply port; a driver for adiabatically expanding non-permeated gas, the driver being disposed downstream of the first non-permeated gas discharge port; a heat exchanger disposed on the first gas flow path; and a non-permeated gas flow path for guiding the non-permeated gas that has passed through the driver to the heat exchanger, the heat exchanger exchanging heat between the non-permeated gas flowing through the non-permeated gas flow path and the raw-material gas flowing through the first gas flow path, thereby cooling the raw-material gas.

Description

Gas separation system and gas separation method using the same

[0001] The present invention relates to a gas separation system and a gas separation method using the same.

[0002] In recent years, as part of efforts to reduce greenhouse gas emissions, CO2 has been removed from the atmosphere and exhaust gases emitted from thermal power plants, etc. ２ Technologies for separating and recovering CO2 are being developed. For example, Non-Patent Document 1 describes how to directly extract CO2 from air. ２ As a new technology for recovering gases, known as DAC (direct air capture), a multi-stage membrane separation process using gas separation membranes has been proposed. In this multi-stage membrane separation process, multiple units having gas separation membranes containing siloxane nanomembranes, which are classified as rubbery polymers, are connected in series, and the process is driven by a vacuum pump installed downstream of each unit and a blower installed upstream of the first unit.

[0003] Shigenori Fujikawa et al., A new strategy for membrane-based direct air capture, Polymer Journal, (2021), 53, 111-119

[0004] The present invention aims to provide a novel gas separation system using a gas separation membrane containing a glassy polymer.

[0005] The present inventors have discovered that in a gas separation system using a gas separation membrane containing a glassy polymer, the non-permeable gas discharged from the gas separation membrane unit without passing through the gas separation membrane is supplied to a drive unit such as a gas turbine, causing adiabatic expansion to lower the temperature of the non-permeable gas. By exchanging heat between the lowered temperature non-permeable gas and the raw material gas compressed by a compressor such as a compressor and supplied to the gas separation membrane unit, the raw material gas is cooled, resulting in good gas separation performance, and thus the present invention has been completed.

[0006] That is, one embodiment of the present invention relates to a gas separation system having a first gas separation membrane unit having a first support layer and a first separation functional layer containing a glassy polymer disposed on the first support layer; a first gas supply port and a first impermeable gas outlet disposed on one side of the first gas separation membrane; and a first permeable gas outlet disposed on the other side of the first gas separation membrane; and a first gas pumping means disposed upstream of the first gas supply port for pumping raw material gas to the first gas supply port; a first gas flow path connecting the first gas pumping means and the first gas supply port; a drive unit disposed downstream of the first impermeable gas outlet for adiabatically expanding the impermeable gas; a heat exchanger disposed on the first gas flow path; and an impermeable gas flow path for guiding the impermeable gas that has passed through the drive unit to the heat exchanger. Furthermore, the gas separation system is characterized in that the heat exchanger cools the raw material gas by exchanging heat between the non-permeable gas flowing through the non-permeable gas channel and the raw material gas flowing through the first gas channel.

[0007] This is a cross-sectional view showing an example of the configuration of a gas separation system according to one embodiment of the present invention. This is a cross-sectional view showing an example of the configuration of the first gas separation membrane shown in Figure 1.

[0008] One embodiment of the present invention is a gas separation system comprising: a first gas separation membrane unit having a first support layer and a first separation functional layer containing a glassy polymer disposed on the first support layer; a first gas supply port and a first impermeable gas outlet disposed on one side of the first gas separation membrane; and a first permeable gas outlet disposed on the other side of the first gas separation membrane; a first gas pumping means disposed upstream of the first gas supply port for pumping raw material gas to the first gas supply port; a first gas flow path connecting the first gas pumping means and the first gas supply port; a drive unit disposed downstream of the first impermeable gas outlet for adiabatically expanding the impermeable gas; a heat exchanger disposed on the first gas flow path; and an impermeable gas flow path for guiding the impermeable gas that has passed through the drive unit to the heat exchanger, wherein the heat exchanger cools the raw material gas by exchanging heat between the impermeable gas flowing through the impermeable gas flowing through the impermeable gas flowing through the first gas flow path and the raw material gas flowing through the first gas flow path. According to this embodiment of the gas separation system, good gas separation performance can be achieved.

[0009] The embodiments of the present invention will be described below with reference to the attached drawings, but the technical scope of the present invention is not limited to the following forms. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant explanations are omitted. Also, the dimensional ratios in the drawings are exaggerated for illustrative purposes and may differ from the actual ratios. In this specification, "X to Y" indicating a range means "X or more and Y or less". Unless otherwise specified, operations and measurements of physical properties, etc., are performed under conditions of room temperature (20 to 25°C) / relative humidity 40 to 50%.

[0010] <Gas Separation System> Figure 1 is a cross-sectional view showing an example of the configuration of a gas separation system 1 according to one embodiment of the present invention. The gas separation system 1 comprises a plurality of gas separation membrane units (a first gas separation membrane unit 10, a second gas separation membrane unit 20, and a third gas separation membrane unit 30).

[0011] Here, using the first gas separation membrane unit 10 as an example, the internal space of the first gas separation membrane unit is divided into two parts, a first part 10a and a second part 10b, by the first gas separation membrane 11. One surface 11a of the first gas separation membrane 11 faces the first part 10a, and the other surface 11b of the first gas separation membrane 11 faces the second part 10b. The first gas separation membrane unit 10 has a first gas supply port 12 and a first non-permeable gas outlet 13 on the first part 10a side. The first gas supply port 12 is for the gas to be separated (for example, CO ２ The first gas separation membrane unit 10 has an opening for taking in a raw material gas (for example, air) containing the first gas separation membrane 11. The first non-permeable gas outlet 13 is an opening for discharging gas that does not permeate the first gas separation membrane 11 to the outside of the first gas separation membrane unit 10. The first gas separation membrane unit 10 has a first permeable gas outlet 14 on the second portion 10b side. The first permeable gas outlet 14 is an opening for discharging permeable gas that has permeated the first gas separation membrane 11 to the outside of the first gas separation membrane unit 10. The second gas separation membrane unit 20 and the third gas separation membrane unit 30 also have a similar configuration.

[0012] Upstream of the gas supply port of each gas separation membrane unit, compressors (first compressor 15, second compressor 25, and third compressor 35) are positioned. These compressors, also called pressurizers, function as gas pumping means (first to third gas pumping means) that compress (pressurize) the gas on the upstream side and send it to the downstream side. Each compressor and the gas supply port are connected via gas flow paths (first gas flow path 17, second gas flow path 27, and third gas flow path 37).

[0013] In this embodiment, an air turbine 100 is located downstream of the first impermeable gas outlet 13. This air turbine 100 functions as a drive unit for adiabatically expanding the impermeable gas discharged from the first impermeable gas outlet 13.

[0014] Meanwhile, a heat exchanger 200 is positioned on the first gas flow path 17, which connects the first compressor 15 and the first gas supply port 12. The impermeable gas, which has undergone adiabatic expansion via the air turbine 100, flows through the impermeable gas flow path 110 and is guided to the heat exchanger 200. The main components of the gas separation system 1 according to this embodiment will be described in detail below. Components common to the first gas separation membrane unit 10 to the third gas separation membrane unit 30 will be described collectively using the first gas separation membrane unit as an example.

[0015] [First to Third Gas Separation Membrane Units] The first gas separation membrane unit 10 has a first gas separation membrane 11, a first gas supply port 12, a first non-permeable gas outlet 13, and a first permeable gas outlet 14. The size, shape, material, etc. of the first gas separation membrane unit 10 itself are not particularly limited as long as the first gas separation membrane 11 can partition the first part 10a and the second part 10b.

[0016] (First to Third Gas Separation Membranes) Figure 2 is a cross-sectional view showing an example of the configuration of the first gas separation membrane 11 shown in Figure 1. The first gas separation membrane 11 is composed of three layers: a first support layer 111, a first intermediate layer 112 covering one main surface of the first support layer 111, and a first separation function layer 113 covering the surface of the first intermediate layer 112 opposite to the surface facing the first support layer 111. In the first gas separation membrane 11 shown in Figure 2, the first separation function layer 113 is located on the outermost surface (constituting the outermost layer). The first support layer 111 has a plurality of pores 111a that communicate from one surface 11a to the other surface 11b of the first gas separation membrane 11. With this configuration, gas that reaches one surface 11a of the first gas separation membrane 11 dissolves in the first separation functional layer 113, diffuses through the interior of the first separation functional layer 113, reaches the interface between the first separation functional layer 113 and the first intermediate layer 112, and desorbs from the first separation functional layer 113. Subsequently, the gas permeates through the first intermediate layer 112, passes through the pores 111a of the first support layer 111, and flows out from the other surface 11b of the first gas separation membrane 11 to the second portion 10b. The solubility and diffusivity of gas in the first separation functional layer differ depending on the type of gas. These differences are utilized to achieve the gas separation performance of the first gas separation membrane 11.

[0017] The material constituting the first support layer 111 may be either an organic material or an inorganic material, but an organic material is preferred. Examples of organic materials include various resin materials such as polytetrafluoroethylene (PTFE), polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET). These can be used individually or in combination of two or more. When two or more different resin materials are combined, they may be mixed to form a uniform material, or they may have a structure with two or more layers, each consisting of one layer of the same type of resin material. Suitable materials for constituting the first support layer 111 include PTFE and PP.

[0018] From the viewpoint of providing mechanical strength and high gas permeability, the thickness of the first support layer 111 is preferably 1 μm to 3000 μm, more preferably 5 μm to 500 μm, and even more preferably 5 μm to 150 μm. The thickness of the first support layer 111 can be measured and calculated in the following manner. First, the first gas separation membrane 11 is cut along the thickness direction at an arbitrary position on the first gas separation membrane 11. Next, the obtained cut surface is observed with an SEM or TEM, and the distance from one surface to the other of the first support layer 111 is measured at four locations. Then, the average value of these four distances is calculated and taken as the thickness of the first support layer 111.

[0019] In the first support layer 111, the average pore diameter and porosity are not particularly limited, as long as the first support layer 111 has sufficient gas permeability. The average pore diameter (diameter) of the first support layer 111 may be, for example, 0.01 μm or more, 0.02 μm or more, 0.03 μm or more, or 0.05 μm or more, or it may be 0.5 μm or less, 0.3 μm or less, or 0.1 μm or less. That is, the average pore diameter of the first support layer 111 is, for example, 0.01 to 0.3 μm, and more specifically, 0.02 to 0.1 μm. Furthermore, the porosity of the first support layer 111 is preferably 40% to 80%. The average pore diameter of the first support layer 111 can be measured and calculated in the following manner. Depending on whether the pores of the first support layer 111 are elongated or interconnected, the surface or cross-section of the first support layer 111 is observed using a SEM or TEM, and the maximum distance between any two points on the contour line of the pores (observation surface) of the first support layer 111 is measured. The average value of the pores observed within several to tens of fields of view is then calculated and used as the average pore diameter. The porosity of the first support layer 111 can also be measured using a general immersion method.

[0020] The first intermediate layer 112 is positioned between the first support layer 111 and the first separation function layer 113. The "intermediate layer" is also referred to as the "gutter layer." The first intermediate layer 112 has the function of suppressing excessive penetration of the composition into the first support layer 111 when applying the composition for forming the first separation function layer 113 onto the first support layer 111. Therefore, by providing the first intermediate layer 112, the first separation function layer 113 can be formed well on the first support layer 111. Furthermore, the first intermediate layer 112 has the function of suppressing the leakage of gas (raw material gas) from defects even if defects occur in the first separation function layer 113.

[0021] The material constituting the first intermediate layer 112 is not particularly limited, and a resin having gas permeability can be appropriately employed. Examples of such resins include silicone resins, amorphous fluorine resins, and the like. The first intermediate layer 112 may have a single-layer structure or a multi-layer structure. Note that the first intermediate layer 112 is an arbitrarily provided layer in the first gas separation membrane 11 according to this embodiment. Therefore, the first gas separation membrane 11 may not have the first intermediate layer 112. In this case, the first separation functional layer 113 may be directly provided on the surface of the first support layer 111.

[0022] The first separation functional layer 113 is a layer directly related to gas separation in the first gas separation membrane 11. Since the first separation functional layer 113 is responsible for gas dissolution and desorption, it is preferably located on the outermost surface (constituting the outermost layer) so as to be in direct contact with the gas on one surface 11a and the other surface 11b of the first gas separation membrane 11. However, as long as sufficient gas dissolution and desorption can be achieved, another layer with high gas permeability (for example, a protective layer) may be provided on the first separation functional layer 113.

[0023] In the first gas separation membrane 11 according to this embodiment, the first separation functional layer 113 contains a glassy polymer. The glassy polymer is an amorphous (non-crystalline) solid in a thermodynamically non-equilibrium metastable state, and is a polymer in which the movement of polymer chains is very slow and all parts exhibit a glassy state where only thermal vibration occurs at their positions. The glassy polymer is not particularly limited, and conventionally known materials can be preferably employed. Examples of such materials include organic polymer materials such as polymers of intrinsic microporosity (PIM), polytrimethylsilylpropyne (PTMSP), polyimide, and silicone. These can be used alone or in combination of two or more. Among them, it is preferable to use polyimides such as aromatic polyimide and fluorine-containing polyimide, and polymers of intrinsic microporosity such as PIM-1 and PIM-7, and it is more preferable to use PIM-1. Note that PIM-1 has a structural unit represented by, for example, the following formula (I).

[0024]

[0025] In the above formula (I), R １ is a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms, and R ２ is a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, or a cyano group, and R ３ is a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, or a cyano group. A plurality of R １ , R ２ and R ３ in the same structural unit may be the same or different respectively.

[0026] As shown by formula (I), PIM-1 is a polymer having a rigid ladder structure and a bent skeleton, and can form micropores inside the layer. Therefore, the first separation functional layer 113 containing PIM-1 has excellent gas permeability.

[0027] The above glassy polymer may have the property that the permeability of CO ２ and / or O ２ is high with respect to the permeability of N ２ . Therefore, the above glassy polymer can selectively permeate CO ２ from a mixed gas (raw material gas) containing CO ２ and N ２ . Also, the above glassy polymer can selectively permeate O ２ from a mixed gas (raw material gas) containing O ２ and N ２ . That is, the first gas separation membrane 11 may be a CO ２ separation membrane that selectively permeates CO ２ from a mixed gas (raw material gas) containing CO ２ and N ２ . Also, the first gas separation membrane 11 may be an O ２ separation membrane that selectively permeates O ２ from a mixed gas (raw material gas) containing O ２ and N ２ . Here, a mixed gas containing CO ２ and N ２ and a mixed gas containing O ２ and N２ The mixed gas containing (raw material gas) can be air. Air as a raw material gas has the advantage of being available in virtually unlimited quantities and can be used without any special treatment.

[0028] The first separation functional layer 113 may further contain inorganic particles in addition to the glassy polymer. Examples of materials constituting the inorganic particles include ceramic materials such as silica and zeolites. In the case of silica particles, examples include (1) fumed silica nanoparticles synthesized by a gas-phase method (dry method) in which silicon-containing raw materials such as silicon tetrachloride are burned in an oxygen and hydrogen flame to hydrolyze them, and (2) colloidal silica nanoparticles synthesized by a liquid-phase method (wet method), such as the water glass method in which sodium is removed by ion exchange of sodium silicate and then heated and aged, or the alkoxide hydrolysis method in which alkoxides such as tetraethoxysilane are hydrolyzed and polycondensed in an alcohol solvent.

[0029] From the viewpoint of forming a first separation functional layer 113 with superior gas permeability and gas selectivity by forming fine pores between the inorganic particles and between the inorganic particles and the glassy polymer, the average particle diameter (D50) of the inorganic particles is preferably 1 nm or more and 20 nm or less, more preferably 1 nm or more and 10 nm or less, and even more preferably 1 nm or more and 5 nm or less. The particle diameter of the inorganic particles can be measured and calculated in the following manner. First, the first gas separation membrane 11 is cut along the thickness direction at an arbitrary position on the first gas separation membrane 11. Next, the obtained cut surface is observed with an optical microscope, scanning electron microscope (SEM), or transmission electron microscope (TEM), and if necessary, further observed with energy dispersive X-ray analysis (EDS) or X-ray photoelectron spectroscopy (XPS), and the maximum distance between any two points on the contour line for four particles is measured. Then, the average value of the maximum distance of the four particles is calculated and taken as the average particle diameter of the particles.

[0030] From the viewpoint of forming a first separation functional layer 113 with excellent gas permeability and gas selectivity by forming fine pores between inorganic particles having sterically hindrance-inducing modifying groups and a glassy polymer, it is preferable that the inorganic particles have modifying groups on their surface. Such inorganic particles having modifying groups can be obtained, for example, by surface-modifying inorganic particles with a silane coupling agent.

[0031] From the viewpoint of improving gas permeability and gas selectivity, the first separation functional layer 113 preferably contains a polymer and the inorganic particles described above. From the viewpoint of improving gas permeability and gas selectivity, the inorganic particle content in the first separation functional layer 113 is preferably 10% by mass or more and 80% by mass or less, and more preferably 20% by mass or more and 60% by mass or less. The inorganic particle content in the first separation functional layer 113 can be measured and calculated in the following manner. First, a fixed amount (1 g) of the first separation functional layer 113 is taken and its mass is measured. Next, the glassy polymer is removed from the first separation functional layer 113 by combustion or the like, and the mass of the residual inorganic particles is measured. Then, the ratio of the mass of the inorganic particles to the mass of the first separation functional layer 113 is calculated to determine the inorganic particle content in the first separation functional layer 113.

[0032] From the viewpoint of improving gas permeability, the thickness of the first separation functional layer 113 is preferably 500 nm or less, and more preferably 400 nm or less. Furthermore, from the viewpoint of the mechanical strength of the first separation functional layer 113, the thickness of the first separation functional layer 113 is preferably 5 nm or more, and more preferably 10 nm or more. In one embodiment, the thickness of the first separation functional layer 113 is preferably 5 nm or more and 500 nm or less, and more preferably 10 nm or more and 400 nm or less. The thickness of the first separation functional layer 113 can be measured and calculated in the following manner. The cross-section of the first gas separation membrane 11 when it is cut in the thickness direction is observed with an optical microscope, SEM or TEM, etc., and the thickness is measured at four locations. Then, the average value of the thicknesses at these four locations is calculated and taken as the thickness of the first separation functional layer 113.

[0033] (First to Third Gas Supply Ports) The first gas supply port 12 is an opening provided for taking in raw material gas into the first gas separation membrane unit 10. The first gas supply port 12 only needs to be provided at least one location on the first portion 10a side of the first gas separation membrane unit 10, and there are no particular restrictions on its number, position, size, etc. When the raw material gas supply source and the first gas separation membrane unit are far apart, the raw material gas supply source and the first gas supply port 12 may be connected by a gas supply line.

[0034] (First to Third Impermeable Gas Outlets) The first impermeable gas outlet 13 is an opening provided to discharge from the first gas separation membrane unit 10 gas that has not permeated the first gas separation membrane 11 (impermeable gas) from the first gas separation membrane unit 10. The first impermeable gas outlet 13 only needs to be provided at least one location on the first portion 10a side of the first gas separation membrane unit 10, and there are no particular restrictions on its number, position, size, etc. In addition, to promote the discharge of impermeable gas from the first gas separation membrane unit 10, an impermeable gas discharge means (for example, a vacuum pump) may be located outside the first gas separation membrane unit 10 and upstream of the air turbine 100 (driver). In this case, it is preferable that the impermeable gas discharge means is connected to the first impermeable gas outlet 13 via a gas supply line.

[0035] (First to Third Permeate Gas Outlets) The first permeate gas outlet 14 is an opening provided to discharge the gas that has permeated through the first gas separation membrane 11 (permeate gas) from the first gas separation membrane unit 10. The first permeate gas outlet 14 only needs to be provided at least one location on the second portion 10b side of the first gas separation membrane unit 10, and there are no particular restrictions on its number, position, size, etc. The first permeate gas outlet 14 is connected to the second compressor 25 installed in the second gas flow path 27.

[0036] [First Compressor 15] The first compressor 15 is a gas pumping means that increases the pressure of a raw material gas such as air and supplies it to the first gas supply port 12 via the first gas flow path 17. The first compressor 15 has the function of increasing the air pressure of the first portion 10a of the first gas separation membrane unit 10, thereby making it easier for gas to permeate from one surface 11a to the other surface 11b of the first gas separation membrane 11. In this specification, the "gas pumping means" is not particularly limited as long as it is capable of pumping gas in such a way that it lowers the air pressure on its upstream side and raises the air pressure on its downstream side. Examples of gas pumping means include compressors, vacuum pumps (water-sealed vacuum pumps, liquid-sealed vacuum pumps, oil-sealed rotary vacuum pumps, dry vacuum pumps), blowers, etc. Among these, compressors or vacuum pumps are preferred, and compressors are more preferred.

[0037] [Air Turbine 100] The air turbine 100 is a drive unit that converts the energy of compressed air into turbine output and uses it as a power source for other machines. The air turbine 100 generates rotational motion by directing the flow of compressed air onto the turbine blades, and utilizes this rotational motion as energy. At this time, the compressed air generates work equivalent to air power within the turbine, and expands (adiabatic expansion) without heat exchange with the outside, causing the temperature of the air to decrease. In this way, air at a relatively low temperature and relatively low pressure is discharged from the air turbine 100. The (relatively low temperature) air discharged after adiabatic expansion in the air turbine 100 flows through the impermeable gas flow path 110 and is introduced into the heat exchanger 200. In this embodiment, electricity can be generated using the rotational motion generated inside the air turbine 100 as a power source. Therefore, there is also the advantage of improved energy efficiency for the entire system. Furthermore, in this specification, the "drive unit" is not particularly limited as long as it can cause an impermeable gas to undergo adiabatic expansion and reduce its temperature and pressure.

[0038] [Heat Exchanger] The heat exchanger 200 exchanges heat between the relatively low-temperature non-permeable gas flowing through the non-permeable gas channel 110 and the relatively high-temperature raw material gas flowing through the first gas channel 17. This cools the raw material gas. The cooled raw material gas is then supplied to the first gas separation membrane unit 10 from the first gas supply port 12 via the first gas channel 17. Meanwhile, the non-permeable gas heated by the heat exchange with the raw material gas is released into the atmosphere.

[0039] During operation of the gas separation system 1, the temperature of the raw material gas supplied to the first gas supply port 12 by the first compressor 15 (first gas pumping means) rises due to pressurization in the first compressor. Here, the gas separation performance of the gas separation membrane containing the glassy polymer is better when the temperature of the supplied raw material gas is lower. Therefore, if this raw material gas is supplied directly to the first gas separation membrane unit 10, it will be a factor that reduces the gas separation performance in the first gas separation membrane unit 10. In contrast, the gas separation system 1 according to this embodiment uses an impermeable gas whose temperature has been lowered by adiabatic expansion via the air turbine 100 (driver) to cool the raw material gas flowing through the first gas flow path 17. As a result, the temperature of the raw material gas, which has risen due to pressurization, decreases, and a lower temperature raw material gas is supplied to the first gas separation membrane unit 10. As a result, the gas separation performance of the gas separation system 1 is improved. It should be noted that drive units such as the air turbine 100 are generally installed for the purpose of generating power for purposes such as electricity generation, and the adiabatic expansion of the introduced gas is merely a secondary function. Therefore, using a drive unit primarily for the adiabatic expansion of compressed air, as in this embodiment, is quite different from the typical uses of drive units in this technological field.

[0040] [Second and Third Compressors and Second and Third Gas Separation Membrane Units] In the gas separation system 1 according to this embodiment, as described above, a second compressor 25 is located upstream of the second gas supply port 22 (downstream of the first permeate gas outlet 14) that constitutes the second gas separation membrane unit 20. Similarly, a third compressor 35 is located upstream of the third gas supply port 32 (downstream of the second permeate gas outlet 24) that constitutes the third gas separation membrane unit 30. The second compressor 25 and the third compressor 35 are connected to the second gas supply port 22 and the third gas supply port 32, respectively. These second compressors 25 and the third compressors 35 also pump gas in such a way that they lower the pressure on their upstream side and raise the pressure on their downstream side. As a result, the gases pressurized by the first compressor 15 and the second compressor 25 and supplied to the first gas separation membrane unit 10 and the second gas separation membrane unit 20 from the first gas supply port 12 and the second gas supply port 22, respectively, become more permeable to the first gas separation membrane 11 and the second gas separation membrane 21, respectively. Furthermore, the permeated gas that has permeated the first gas separation membrane 11 will further permeate the second gas separation membrane 21 and the third gas separation membrane 31, thus separating the target gas (for example, CO2). ２ This makes it possible to increase the purity of the target gas (for example, CO). In this way, by providing multiple gas separation membrane units in the gas separation system 1 and increasing the number of separations by the gas separation membrane, the target gas to be separated (for example, CO) can be purified. ２ Further purification of the gas can be achieved. The number of gas pumping means and gas separation membrane units can be appropriately determined by those skilled in the art depending on the type and purity of the gas to be separated.

[0041] In this embodiment, a first gas cooler 16 (first gas cooling means) is installed between the second compressor 25 and the second gas supply port 22 to lower the temperature of the gas pumped by the second compressor 25. Similarly, a second gas cooler 26 (second gas cooling means) is installed between the third compressor 35 and the third gas supply port 32 to lower the temperature of the gas pumped by the third compressor 35. Since the gas that has passed through the second compressor 25 and the third compressor 35 is pressurized, its temperature may be higher than before pressurization. The glassy polymer contained in the second gas separation membrane 21 and the third gas separation membrane 31 has the property that the solubility of the gas decreases as the gas temperature rises. Therefore, by lowering the respective gas temperatures with the first gas cooler 16 and the second gas cooler 26, the decrease in the gas separation performance of the second gas separation membrane 21 and the third gas separation membrane 31 is suppressed, and the target gas to be separated (for example, CO) is reduced. ２ Further purification of the gas is possible. The gas cooling means is not particularly limited, and conventionally known coolers and heat exchangers can be used as appropriate. The gas temperature after cooling by the first and second gas cooling means is not particularly limited, but for example, it is 40°C or lower, preferably 30°C or lower, more preferably 25°C or lower, even more preferably 20°C or lower, and particularly preferably 0°C or higher and 20°C or lower. However, if sufficient gas separation performance can be obtained without installing the first and / or second gas cooling means, it is also preferable not to install them.

[0042] [Drain Discharge Channel 300] In the first gas flow path 17 according to this embodiment, a drain discharge channel 300 is further installed downstream of the heat exchanger 200 to discharge the drain, which is cooled and liquefied by the heat exchange in the heat exchanger 200, to the outside. Here, the drain, which is cooled and liquefied by the heat exchange of the raw material gas, may contain acidic substances such as sulfur dioxide and hydrogen sulfide, or oil, derived from the components of the first compressor 15 or lubricating oil. When such acidic substances or oil are supplied to the first gas separation membrane unit 10 from the first gas supply port 12 together with the raw material gas and reach the first gas separation membrane 11, it may cause deterioration of the first gas separation membrane 11. In contrast, according to this embodiment, the drain, which is liquefied raw material gas, can be discharged via the drain discharge channel 300, thus preventing deterioration of the first gas separation membrane 11. Furthermore, the drain discharge channel 300 according to this embodiment is configured so that the raw material gas exchanges heat with the drain flowing through the drain discharge channel 300. Specifically, as shown in Figure 1, the drain discharge channel 300 is arranged to wrap around the first gas flow path 17, thereby achieving the heat exchange described above. This configuration liquefies the water vapor in the raw material gas cooled by the heat exchanger 200, reducing the humidity of the raw material gas, thereby preventing condensation inside the first gas separation membrane unit 10 and the resulting deterioration of the first gas separation membrane 11. Note that the configuration for achieving the heat exchange described above is not limited to the form shown in Figure 1; for example, the configuration of a Liebig cooler may be applied to the drain discharge channel 300 and the first gas flow path 17. Furthermore, if there are few impurities in the raw material gas or the humidity of the raw material gas is low, it may not be necessary to provide the drain discharge channel 300, or even if it is provided, heat exchange with the raw material gas may not be necessary.

[0043] [Cooling Mechanism] The gas separation system 1 according to this embodiment has a cooling mechanism that uses condensation water generated on the outer surface of the impermeable gas channel 110 to cool the raw material gas flowing through the first gas channel. When the impermeable gas, whose temperature has decreased due to adiabatic expansion in the air turbine 100, flows through the impermeable gas channel 110, water vapor in the air can condense around the piping that constitutes the impermeable gas channel 110, generating condensation water. In this embodiment, a condensation water guide frame 400 is provided below the impermeable gas channel 110, which is located above the first gas channel 17, to guide the condensation water that has fallen from the impermeable gas channel 110 to drip into the first gas channel 17. With this configuration, the raw material gas flowing through the first gas channel 17 can be further cooled by utilizing the heat of vaporization when the condensation water that has dripped into the first gas channel 17 evaporates. As a result, the gas separation performance in each gas separation membrane unit can be further improved. Furthermore, a condensation water pan 410 is provided below the first gas flow path 17 to collect condensation water that drips into the first gas flow path 17 and then flows out of the first gas flow path 17. In this case, the condensation water pan 410 may be positioned so that the condensation water stored in the condensation water pan 410 comes into contact with the first gas flow path 17. This allows the first gas flow path 17 to be further cooled by the condensation water in contact with it. Note that the above cooling mechanism may be omitted in some cases.

[0044] [Heating Mechanism] The gas separation system 1 according to this embodiment further includes a mechanism (heating mechanism) that heats the air turbine 100 (driver) using the waste heat from the first compressor 15 (first gas pumping means) (dashed line shown in Figure 1). When the air turbine 100 (driver) is driven, the temperature may drop below freezing, which can cause a malfunction due to freezing. However, with the above configuration, the heat generated by the operation of the first compressor 15 is used to heat the air turbine 100 (driver), preventing the air turbine 100 (driver) from freezing and causing a malfunction. The specific form of the heating mechanism is not particularly limited. For example, the first compressor 15 and the air turbine 100 can be placed close together so that the waste heat from the first compressor 15 can be transmitted through the air to heat the air turbine 100. Alternatively, the air turbine 100 (drive unit) may be heated by exchanging heat between the raw material gas immediately after it is discharged from the first compressor 15 (first gas pumping means) and the raw material gas immediately before it is supplied to the air turbine 100. This heating mechanism may also be omitted in some cases.

[0045] <Gas Separation Method> According to the present invention, a gas separation method using the above gas separation system is also provided. This gas separation method comprises supplying a raw material gas to the first gas supply port.

[0046] The raw material gas is a mixed gas containing the gas to be separated and other gases. The raw material gas is not particularly limited, but CO ２ and N ２ It may also be a mixed gas containing O ２ and N ２ The gas mixture may also contain the following. More specifically, the source gas may be air or exhaust gas emitted from an internal combustion engine.

[0047] From the viewpoint of improving the gas separation performance of the gas separation membrane, the temperature of the raw material gas supplied to the first gas supply port is preferably low. Specifically, the temperature is, for example, 40°C or lower, preferably 30°C or lower, more preferably 25°C or lower, even more preferably 20°C or lower, and particularly preferably 0°C or higher and 20°C or lower.

[0048] Furthermore, the following embodiments are also included in the scope of the present invention: a gas separation system of claim 1 having the features of claim 2; a gas separation system of claim 2 having the features of claim 3; a gas separation system of any of claims 1 to 3 having the features of claim 4; a gas separation system of any of claims 1 to 4 having the features of claim 5; a gas separation system of any of claims 1 to 5 having the features of claim 6; a gas separation system of any of claims 1 to 6 having the features of claim 7; a gas separation system of any of claims 1 to 7 having the features of claim 8; a gas separation method using any of the gas separation systems of claims 1 to 8; and a gas separation method according to claim 9 having the features of claim 10.

[0049] A gas separation system 1, shown in Figure 1, comprising a first gas separation membrane unit 10 (equipped with a first gas separation membrane 11 made of PIM-1), a first compressor 15, a first gas flow path 17, an air turbine 100, a non-permeable gas flow path 110, and a heating mechanism for heating the drive unit, was simulated using ASPENTECH's process simulation software "ASPENPLUS (V14.1)". Various conditions were set as follows.

[0050] [Setting Conditions] (1) Raw material gas (air) Atmospheric pressure: 1 [bar] Temperature: 25 [°C] Supply flow rate: 100 [kmol / hr] Component composition: N ２ = 78 [volume %], O ２ = 21.96 [volume %], CO ２0.04 [volume %] (2) First compressor 15 (first pumping means) Inlet pressure: 1 [bar] Outlet pressure: 1.3 [bar] Inlet temperature: 25 [°C] Discharge temperature: 86 [°C] Mechanical efficiency: 70 [%] (3) Heat exchanger 200 High temperature side: Inlet temperature = 44 [°C], Outlet temperature = 36 [°C] Low temperature side: Inlet temperature = 1 [°C], Outlet temperature = 10 [°C] (4) Heating mechanism - Temperature of raw material gas immediately after discharge from the first compressor 15 (first gas pumping means) before heat exchange = 86 [°C], Temperature after heat exchange = 44 [°C] - Temperature of raw material gas immediately before heat exchange just before being supplied to the air turbine 100 (driver) = 36 [°C], Temperature after heat exchange = 81 [°C] (5) Air turbine 100 (driver) Discharge pressure: 0.3 [bar] Mechanical efficiency: 70 [%] (6) Non-permeable gas temperature after adiabatic expansion: 1 [°C] Mechanical efficiency: 70 [%] Flow rate: 92.1 [kmol / hr] (7) Pressure on the supply side of the first gas separation membrane unit: 1.3 [bar] Pressure on the permeate side: 0.05 [bar] Based on the above simulation results, CO in the first gas separation membrane unit 10 ２ The results showed that the permeability improved by approximately five times compared to the case where the raw material gas discharged from the first compressor 15 at a discharge temperature of 86°C was supplied directly to the first gas separation membrane unit. Furthermore, the CO2 in the first gas separation membrane unit 10 ２ Regarding selectivity, the results showed an improvement of approximately three times compared to the case where the raw material gas discharged from the first compressor 15 at a discharge temperature of 86°C was supplied directly to the first gas separation membrane unit. These results demonstrate that the gas separation system and gas separation method according to this embodiment can achieve good gas separation performance.

[0051] 1 Gas separation system, 10 First gas separation membrane unit, 10a First part, 10b Second part, 11 First gas separation membrane, 11a, 11b, 21a, 21b surfaces, 12 First gas supply port, 13 First impermeable gas outlet, 14 First permeable gas outlet, 15 First compressor (first gas pumping means), 16 First gas cooler (first gas cooling means), 20 Second gas separation membrane unit, 21 Second gas separation membrane, 22 Second gas supply port, 23 Second impermeable gas outlet, 24 Second permeable gas outlet, 25 Second compressor (second gas pumping means), 26 Second gas cooler (second gas cooling means), 30 Third gas separation membrane unit, 32 Third gas supply port, 100 Air turbine (driver), 110 Impermeable gas flow path, 111 First support layer, 111a pores, 112 first intermediate layer, 113 first separation functional layer, 200 heat exchanger, 300 drain discharge channel, 400 condensation water guide frame, 410 condensation water pan.

Claims

1. A first gas separation membrane unit having: a first support layer and a first separation functional layer containing a glassy polymer disposed on the first support layer; a first gas supply port and a first impermeable gas outlet disposed on one side of the first gas separation membrane, and a first permeable gas outlet disposed on the other side of the first gas separation membrane; a first gas pumping means disposed upstream of the first gas supply port for pumping raw material gas to the first gas supply port; a first gas flow path connecting the first gas pumping means and the first gas supply port; a drive unit disposed downstream of the first impermeable gas outlet for adiabatically expanding the impermeable gas; a heat exchanger disposed on the first gas flow path; and an impermeable gas flow path for guiding the impermeable gas that has passed through the drive unit to the heat exchanger. The heat exchanger is a gas separation system that cools the raw material gas by exchanging heat between the non-permeable gas flowing through the non-permeable gas flow path and the raw material gas flowing through the first gas flow path.

2. The gas separation system according to claim 1, further comprising a drain discharge channel for discharging condensate, which is cooled and liquefied by heat exchange in the heat exchanger, to the outside.

3. The gas separation system according to claim 2, wherein the drain discharge passage is configured such that the raw material gas exchanges heat with the drain flowing through the drain discharge passage.

4. The gas separation system according to claim 1, further comprising a mechanism for cooling the raw material gas flowing through the first gas channel using condensation water generated on the outer surface of the non-permeable gas channel.

5. The gas separation system according to claim 1, further comprising a mechanism for heating the drive unit using the waste heat from the first gas pumping means.

6. The first gas separation membrane is CO ２ and N ２ CO from the aforementioned raw material gas ２ Selectively separating CO ２ The gas separation system according to claim 1, wherein the separation membrane is a separation membrane.

7. The first gas separation membrane is O ２ and N ２ From the aforementioned raw material gas containing O ２ Selectively separates O ２ The gas separation system according to claim 1, wherein the separation membrane is a separation membrane.

8. The gas separation system according to claim 6 or 7, wherein the raw material gas is air.

9. A gas separation method using the gas separation system according to claim 1 or 2, comprising supplying the raw material gas to the first gas supply port.

10. The gas separation method according to claim 9, wherein the temperature of the raw material gas supplied to the first gas supply port is 25°C or lower.

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