Patent Application
20220280896
This disclosure relates to a gas separation membrane module.
In recent years, hydrogen has attracted attention as a clean energy source. Hydrogen is obtained by gasifying natural gas and fossil fuel such as coal and removing carbon dioxide from a mixed gas containing hydrogen and carbon dioxide as main components. The gas to be treated has undergone steam reforming and water gas shift, and is characteristic in having high temperature and high pressure. Further, hydrogen is also used in the Haber-Bosch process for ammonia synthesis. This is a method of synthesizing ammonia by reacting hydrogen and nitrogen at high temperature and high pressure. In a production plant, it is necessary to have a process of separating and recovering unreacted hydrogen and nitrogen.
As a method of concentrating a specific gas from a mixed gas at low cost, a membrane separation method in which a target gas is selectively permeated using a difference in gas permeability of a material has attracted attention.
Japanese Patent Laid-open Publication No. 2016-137462 discloses a technique in which a channel material of a gas separation membrane module is inclined in a thickness direction to increase the turbulent intensity of feed gas. Further, WO 2016/194833 A discloses a technique in which a dimensional difference is provided in dimensions of a separation membrane and a channel material to improve airtightness of a spiral separation membrane module. Furthermore, Japanese Patent Laid-open Publication No. 2015-136634 discloses a technique in which an adhesive or the like is used to provide a wall in a feed flow path formed by a net, and a flow direction of feed gas is forcibly changed to improve separation characteristics.
However, the conventional gas separation membrane module has a problem that a defect occurs in the separation membrane and the separation performance is deteriorated. That is, as a means of increasing the filling amount of the separation membrane per unit volume in the gas separation membrane module, it is considered to decrease the thickness of the channel material. However, in simply thinning the channel material, the channel material is broken, thereby impairing its function, or wrinkles are generated when the channel material is wound around the center pipe. In addition, even when the channel material can be wound without any problem, fine defects that do not occur in a liquid separation membrane module occur due to stress when the gas separation membrane module is loaded in a pressure vessel.
Therefore, it could be helpful to provide a gas separation membrane module in which a filling amount of a gas separation membrane can be increased while improving winding stability and loading properties into a pressure vessel.
We thus provide:
It is thus possible to increase the filling amount of the gas separation membrane while improving the winding stability of the gas separation membrane module and the loading properties into the pressure vessel.
Hereinafter, examples of our modules will be described in detail.
As shown in
The center pipe (6) is a hollow (cylindrical) member whose at least downstream end is open so that a permeate gas described later is discharged. When a plurality of gas separation membrane modules 100 is connected, a center pipe whose both ends are open is employed. A plurality of holes is provided to a side surface (side surface in a cylindrical shape) of the center pipe 6.
The separation membrane leaf includes: a plurality of separation membranes (1) each having a feed surface and a permeate surface, the separation membranes being arranged such that the feed surfaces face each other and the permeate surfaces face each other; and a feed channel material (2) arranged between the feed surfaces of the separation membranes (1). When, for example, one membrane is folded with its permeate or feed surface facing inward and wound around the center pipe is also included when a “plurality of separation membranes” is provided.
Further, the permeate channel material (3) is arranged between the permeate surfaces of the separation membranes (1), and is wound around the center pipe (6) together with the separation membrane leaf to form the gas separation membrane module (100).
A feed gas (201) is fed from one end surface of the gas separation membrane module (100). The feed gas (201) is separated while moving in the longitudinal direction of the center pipe (6) of the gas separation membrane module (100), and a permeate gas (202) that has permeated through the separation membrane passes the holes at the side surface of the center pipe (6) through the inside of the center pipe (6) and is discharged from the end of the center pipe. The feed gas that has not been filtered is discharged as a concentrated gas (203) from the other end surface of the gas separation membrane module (100).
As another form of the gas separation membrane module,
The feed channel material and the permeate channel material described later can also be applied to a gas separation membrane module according to an aspect other than
The gas separation membrane module includes a feed channel material and a permeate channel material. Examples of the channel material include a net and a nonwoven fabric, as well as a knit such as tricot, a woven fabric such as a plain weave mesh, and a porous sheet having protrusions such as a rugged sheet. Further, a protrusion functioning as a channel material may be fixed to the feed surface and/or the permeate surface of the separation membrane.
In operation at several MPa such as in water treatment applications, a reinforcing material such as filament winding is attached to the outer periphery of the module to prevent breakage of the module. Meanwhile, in the gas separation membrane module, since the viscosity and density of the feed fluid are low, the module is less likely to be broken, and filament winding can be removed. However, if only the filament winding is omitted, the module is strongly gripped when the module is loaded into the pressure vessel, whereby the separation membrane is damaged by the channel material, and the module performance may be deteriorated.
On the other hand, since the module includes a channel material having a small average pore size, the space where the separation membrane falls is small even when the module is strongly gripped, and the loaded stress is dispersed. As a result, an excessive load is not applied to the module during loading, and thus physical destruction of the separation membrane is reduced, and deterioration of separation performance is suppressed.
To suppress falling of the separation membrane into the channel material and disperse stress during module loading, an average pore size on a front surface and an average pore size on a back surface of the feed channel material are each 0.95 mm or less, and an average pore size on a front surface and an average pore size on a back surface of the permeate channel material are each 0.95 mm or less. The average pore size is preferably 0.4 mm or less, and particularly preferably 0.1 mm or less.
The average pore size is an average value of circle equivalent diameters represented by “4× area of pore in surface direction of channel material/circumferential length of the pore.” The areas and circumferential lengths of 30 pores in one surface of the channel material are measured to calculate circle equivalent diameters. Further, an average value of 30 circle equivalent diameters is calculated. An average value of circle equivalent diameters in the other surface of the channel material is calculated in the same manner as described above. In this way, the average pore sizes on the front and back surfaces of each channel material are calculated.
The feed channel material and the permeate channel material may be the same or different in material, shape, and average pore size.
For example, the permeate channel materials may be bonded as shown in
In the production of the gas separation membrane module, the end of one permeate channel material A (3A) of the permeate channel materials (3A, 3B) is fixed to the center pipe (6) by adhesion, and the other permeate channel materials B (3B) are bonded onto the permeate channel material A (3A). In a state where the separation membranes and the feed channel materials are stacked between the permeate channel materials (3A, 3B), the permeate channel material fixed to the center pipe is wound while applying tension toward the outside in the winding direction of the center pipe (in the example of
As the permeate channel material A to which a load is applied as described above, a permeate channel material having a breaking tension of 15 kgf/300 mm (147 N/300 mm) or more may be used so that it is possible to reduce the occurrence of breakage and wrinkling Meanwhile, when a large repulsive force is generated against the load at the time of winding, it is necessary to increase the winding tension so a crack may occur in the permeate channel material A. In addition, when the gas separation membrane module is wound while increasing the winding tension, the channel material is continuously wound while being bent, and the circularity of the cross section of the gas separation membrane module decreases, whereby it is difficult to load the gas separation membrane module into the vessel. When the breaking tension of the permeate channel material A is 100 kgf/300 mm (980 N/300 mm) or less, the occurrence of such a defect is suppressed. That is, the breaking tension of the permeate channel material A is preferably 15 kgf/300 mm or more and 100 kgf/300 mm or less (147 N/300 mm or more and 980 N/300 mm or less), and more preferably 15 kgf/300 mm or more and 30 kgf/300 mm or less (147 N/300 mm or more and 294 N/300 mm or less).
In addition, since the rigidity of the permeate channel material that supports the separation membrane at the time of winding affects the winding properties, the breaking tension of the permeate channel material B may be set to be lower than that of the permeate channel material A. Consequently, even when the permeate channel material A having a high breaking tension is used, it is possible to reduce the strength of the entire laminated body of the separation membrane, the feed channel material, and the permeate channel material, and it is possible to suppress the repulsive force against the winding. Specifically, the breaking tension of the permeate channel material B may be set to 2 kgf/300 mm or more and 10 kgf/300 mm or less (19.6 N/300 mm or more and 98 N/300 mm or less), and preferably 5 kgf/300 mm or more and 10 kgf/300 mm or less (49 N/300 mm or more and 98 N/300 mm or less) so that it is possible to suppress breakage, wrinkling, displacement, and reduction in circularity.
From the same viewpoint as the reason why the average pore size and breaking tension are as described above and from the viewpoint of handleability, a plain weave mesh or a rugged sheet (such as a porous sheet to which protrusions are fixed or a film formed into a rugged shape and subjected to perforation processing) is preferable as the permeate channel material A, and a nonwoven fabric is preferable as the permeate channel material B.
The feed channel material and the permeate channel material are preferably thin. As described above, when deformation such as bending is applied to a channel material for producing a module, stress is generated in the channel material and the channel material is easily broken. Accordingly, it is necessary that the thickness of the channel material is decreased to appropriately reduce the rigidity against bending. For these reasons, the thickness of the channel material is preferably 250 μm or less, more preferably 100 μm or less, still more preferably 80 μm or less, and most preferably 50 μm or less. Meanwhile, the lower limit is preferably 10 μm or more to secure a sufficient flow path.
As a material for casting or molding the feed channel material and the permeate channel material, a thermoplastic resin is preferable from the viewpoint of casting or molding properties, and polyester, nylon, polyphenylene sulfide, polyethylene, polypropylene, polysulfone, polyether sulfone, polylactic acid, an acrylonitrile-butadiene-styrene (ABS) resin or a UV curable resin is more preferable from the viewpoint of suppressing damage to the separation membrane.
The feed channel material and the permeate channel material may be provided with curved or linear walls that control the flow of the feed gas and the permeate gas. Further, the wall material is not limited as long as it is not deteriorated depending on the pressure and temperature at which the separation membrane module is operated and the kind of the gas at the feed side.
The ends of the separation membrane sandwiching the feed channel material are appropriately sealed. Examples of the method of “sealing” include adhesion using an adhesive, a hot-melt technique or the like, fusion using heating, laser or the like, and insertion of a rubber sheet, and sealing by simple adhesion is preferable.
Thicknesses of the permeate channel material and the feed channel material are reduced to create a space for the gas separation membrane module, and the space is filled with the separation membrane so that it is possible to increase the membrane area of the gas separation membrane module. Particularly, the flow resistance of the channel material is reduced, whereby the influence of the increase in the flow resistance becomes insignificant if the thickness of the channel material is decreased. Thus, it is possible to improve the gas permeability by the increase in the membrane area.
As a form of the center pipe, a cylindrical shape can be used as described above, and the center pipe has one or a plurality of holes through which gas can pass at the outer periphery. Further, it may be configured that a partition wall is provided inside the center pipe, and the gas fed from one end cannot move to the other end and passes through holes provided to the outer periphery.
The separation membrane may include a substrate, a porous support layer on the substrate, and a separation functional layer on the porous support layer. However, the substrate is not an essential element, and the separation membrane may include at least a porous support layer and a separation functional layer.
Examples of the substrate include a polyester-based polymer, a polyamide-based polymer, a polyolefin-based polymer, or a mixture or copolymer of these polymers. Among others, a cloth fabric of a polyester-based polymer having high mechanical and thermal stability is particularly preferable. As the form of the cloth fabric, a long fiber nonwoven fabric, a short fiber nonwoven fabric, and a weave or knit fabric can be preferably used. The long fiber nonwoven fabric refers to a nonwoven fabric having an average fiber length of 300 mm or more and an average fiber diameter of 3 to 30 μm.
The volume of airflow through the substrate is preferably 0.5 cc/cm2/sec or more and 5.0 cc/cm2/sec or less. When the volume of airflow through the substrate is within the above range, the substrate is impregnated with a polymer solution that serves as the porous support layer. Accordingly, the adhesion to the substrate is improved, and the physical stability of the porous support membrane can be enhanced.
The thickness of the substrate is preferably 10 to 200 μm, and more preferably 30 to 120 μm. The thickness means an average value unless otherwise noted. The average value represents an arithmetic mean value. Specifically, the thickness of the substrate is determined by calculating an average value of thicknesses at 20 points measured at intervals of 20 μm in a direction (surface direction of the membrane) orthogonal to the thickness direction in cross-section observation.
The porous support layer does not substantially have gas separation performance, and imparts strength to the separation functional layer having substantially separation performance. The size and distribution of the pores of the porous support layer are not particularly limited. A preferable example is a porous support layer having uniform and fine pores or fine pores gradually increasing in size from one surface on the side where the separation functional layer is formed to the other surface, the fine pores on the surface on the separation functional layer formed side having a size of 0.1 nm or more and 100 nm or less. However, the material used and the shape thereof are not particularly limited.
The porous support layer contains, for example, at least one polymer selected from the group consisting of homopolymers and copolymers of polysulfone, polyether sulfone, polyamide, polyester, cellulose-based polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, and polyphenylene oxide. Examples of the cellulose-based polymer include cellulose acetate and cellulose nitrate, and examples of the vinyl polymer include polyethylene, polypropylene, polyvinyl chloride, and polyacrylonitrile. The porous support layer more preferably contains cellulose acetate, polysulfone, polyether sulfone, polyamide, polyphenylene sulfide sulfone, or polyphenylene sulfone. Among these materials, polysulfone, polyether sulfone, and polyamide are particularly preferable because they have high chemical, mechanical, and thermal stability and are easily molded.
The thicknesses of the substrate and the porous support layer affect the strength of the separation membrane and the filling density when the separation membrane is formed into a module. To obtain sufficient mechanical strength and filling density, the total thickness of the substrate and the porous support layer is preferably 30 μm or more and 300 μm or less, and more preferably 100 μm or more and 220 μm or less. The thickness of the porous support layer is preferably 20 μm or more and 100 μm or less. The thicknesses of the substrate and the porous support layer are determined by calculating an average value of thicknesses at 20 points measured at intervals of 20 μm in a direction (surface direction of the membrane) orthogonal to the thickness direction in cross-section observation.
The porous support layer can be selected from various commercially available materials such as “Millipore Filter VSWP” (trade name) manufactured by Millipore Corporation and “Ultra Filter UK 10” (trade name) manufactured by Toyo Roshi Kaisha, Ltd., and can be manufactured according to the method described in “Office of Saline Water Research and Development Progress Report” No. 359 (1968).
The separation functional layer includes, on the support layer, a graphene layer or a thin film layer mainly containing polyamide obtained by a polycondensation reaction of a polyfunctional amine and a polyfunctional acid halide. In other words, the separation functional layer contains graphene or crosslinked polyamide as a main component. Specifically, in the separation functional layer, the ratio of the graphene or the crosslinked polyamide may be 50 wt % or more, 70 wt % or more, or 90 wt % or more, and the separation functional layer may be configured to contain only the graphene or the crosslinked polyamide. When the separation functional layer contains 50 wt % or more of graphene or crosslinked polyamide, high membrane performance is easily exhibited.
The crosslinked polyamide may be a wholly aromatic polyamide or a wholly aliphatic polyamide, or may have both an aromatic moiety and an aliphatic moiety. The crosslinked polyamide is preferably wholly aromatic to exhibit higher performance.
The polyfunctional amine is specifically a polyfunctional aromatic amine or a polyfunctional aliphatic amine, and the polyfunctional acid halide is a polyfunctional aromatic acid halide or a polyfunctional aliphatic acid halide. The polycondensation reaction is interfacial polycondensation.
The thickness of the separation functional layer is usually 0.01 to 1 μm, and preferably 0.1 to 0.5 μm to obtain sufficient separation performance and gas permeability. The separation functional layer is also referred to as “polyamide separation functional layer.”
In a crosslinked polyamide functional layer constituting a composite semipermeable membrane, when the number of terminal amino groups is A, the number of terminal carboxy groups is B, and the number of amide groups is C, (A+B)/C≤0.66 is preferably satisfied.
An amino group and a carboxy group are known to be a functional group having strong affinity for carbon dioxide. When the proportion of such functional groups in the polyamide is reduced, the affinities for carbon monoxide and carbon dioxide are reduced, and only the permeance of carbon monoxide and the permeance of carbon dioxide decrease without decreasing the permeance of a light gas such as hydrogen or helium, whereby the light gas/carbon monoxide separation selectivity and the light gas/carbon dioxide separation selectivity are improved.
In addition, as the proportion of the amide group in the polyamide increases, the degree of crosslinking in the polyamide is improved, the pore size decreases, the permeance of nitrogen, carbon monoxide, carbon dioxide, hydrogen sulfide, sulfurous acid gas, and hydrocarbons having a larger size than light gases such as hydrogen and helium decreases. Thus, the light gas/nitrogen separation selectivity, the light gas/carbon monoxide separation selectivity, the light gas/carbon dioxide separation selectivity, the light gas/hydrocarbon separation selectivity, the light gas/hydrogen sulfide separation selectivity, and the light gas/sulfurous acid gas separation selectivity are improved. The molecular size of the gas is hydrogen<carbon dioxide<carbon monoxide=nitrogen<sulfur content (hydrogen sulfide and sulfurous acid gas), and the gas having a larger molecular size tends to be more easily separated. For example, the hydrogen/nitrogen separation selectivity, the hydrogen/carbon monoxide separation selectivity, the hydrogen/hydrocarbon separation selectivity, the hydrogen/hydrogen sulfide separation selectivity, and the hydrogen/sulfite gas separation selectivity tend to be higher than the hydrogen/carbon dioxide separation selectivity.
The ratio of the number A of terminal amino groups, the number B of terminal carboxy groups, and the number C of amide groups can be determined by 13C solid NMR measurement of the separation functional layer. Specifically, the substrate is peeled off from 5 m2 of the separation membrane to obtain the polyamide separation functional layer and the porous support layer, and then the porous support layer is dissolved and removed to obtain the polyamide separation functional layer. The obtained polyamide separation functional layer is measured by the DD/MAS-13C solid NMR method, and the ratio of numbers of respective functional groups can be calculated by comparing the integrated value of carbon peaks of each functional group or peaks of carbon bonded with each functional group.
The “polyfunctional aromatic amine” means an aromatic amine having two or more amino groups per molecule, in which the amino groups are at least either one of a primary amino group and a secondary amino group and at least one of those amino groups is a primary amino group, and the “polyfunctional aliphatic amine” means an aliphatic amine having two or more amino groups per molecule, in which the amino groups are at least either one of a primary amino group and a secondary amino group.
Examples of the polyfunctional aromatic amine include a polyfunctional aromatic amine in which two amino groups are bonded to an aromatic ring in a positional relationship of any of ortho-position, meta-position and para-position such as o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, o-xylylenediamine, m-xylylenediamine, p-xylylenediamine, o-diaminopyridine, m-diaminopyridine and p-diaminopyridine; a polyfunctional aromatic amine such as 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 3-aminobenzylamine, 4-aminobenzylamine, 2,4-diaminothioanisole, 1,3-diaminothioanisole, 1,3-diamino-5-(dimethylphosphino)benzene, (3,5 -diaminophenyl)dimethylphosphine oxide, (2,4-diaminophenyl)dimethylphosphine oxide, 1,3-diamino-5-(methylsulfonyl)benzene, 1,3-diamino-4-(methylsulfonyl)benzene, 1,3-diamino-5-nitrosobenzene, 1,3-diamino-4-nitrosobenzene, 1,3-diamino-5-(hydroxyamino)benzene, and 1,3-diamino-4-(hydroxyamino)benzene; and a polyfunctional aliphatic amines such as ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, piperazine, 2-methyl piperazine, 2,4-dimethyl piperazine, 2,5-dimethyl piperazine, and 2,6-dimethyl piperazine. These polyfunctional amines may be used singly or in combination of two or more kinds thereof.
The polyfunctional acid halide is also expressed as a polyfunctional carboxylic acid derivative, and indicates an acid halide having at least two carbonyl halide groups per molecule. Examples of the trifunctional acid halide include trimesic acid chloride, and examples of the bifunctional acid halide include biphenyldicarboxylic acid dichloride, azobenzenedicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, naphthalenedicarboxylic acid chloride, and oxalyl chloride. In consideration of reactivity with the polyfunctional amine, the polyfunctional acid halide is preferably a polyfunctional acid chloride, and in consideration of selective separability and heat resistance of the membrane, a polyfunctional acid chloride having 2 to 4 carbonyl chloride groups per molecule is preferable. Among others, trimesic acid chloride is more preferably used from the viewpoint of availability and ease of handling. These polyfunctional acid halides may be used singly or in combination of two or more kinds thereof
Polyamides have high cohesiveness, and the solubility of light gases such as hydrogen and helium having low cohesiveness is low. However, the cohesiveness of the polyamides is reduced by introducing fluorine into an aromatic ring, and the solubility of the light gases is improved; as a result, the light gas/nitrogen separation selectivity is improved.
The “polyfunctional aromatic amine” means an aromatic amine having two or more amino groups per molecule, in which the amino groups are at least either one of a primary amino group and a secondary amino group and at least one of those amino groups is a primary amino group.
Examples of the polyfunctional aromatic amine include a polyfunctional aromatic amine in which two amino groups are bonded to an aromatic ring in a positional relationship of any of ortho-position, meta-position and para-position such as o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, o-xylylenediamine, m-xylylenediamine, p-xylylenediamine, o-diaminopyridine, m-diaminopyridine and p-diaminopyridine; and a polyfunctional aromatic amine such as 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 3-aminobenzylamine, 4-aminobenzylamine, 2,4-diaminothioanisole, 1,3-diaminothioanisole, 1,3-diamino-5-(dimethylphosphino)benzene, (3,5 -diaminophenyl)dimethylphosphine oxide, (2,4-diaminophenyl)dimethylphosphine oxide, 1,3-diamino-5-(methylsulfonyl)benzene, 1,3-diamino-4-(methylsulfonyl)benzene, 1,3 -diamino-5-nitrosobenzene, 1,3-diamino-4-nitrosobenzene, 1,3-diamino-5-(hydroxyamino)benzene, and 1,3-diamino-4-(hydroxyamino)benzene. These poly-functional aromatic amines may be used singly or in combination of two or more thereof.
The polyfunctional aromatic acid halide is also expressed as a polyfunctional aromatic carboxylic acid derivative, and indicates an aromatic acid halide having at least two carbonyl halide groups per molecule. Examples of the trifunctional acid halide include trimesic acid chloride, and examples of the bifunctional acid halide include biphenyldicarboxylic acid dichloride, azobenzenedicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, and naphthalenedicarboxylic acid chloride. In consideration of reactivity with the polyfunctional aromatic amine, the polyfunctional aromatic acid halide is preferably a polyfunctional aromatic acid chloride, and in consideration of selective separability and heat resistance of the membrane, a polyfunctional aromatic acid chloride having 2 to 4 carbonyl chloride groups per molecule is preferable. Among others, trimesic acid chloride is more preferably used from the viewpoint of availability and ease of handling. These polyfunctional aromatic acid halides may be used singly or in combination of two or more kinds thereof.
Further, the crosslinked aromatic polyamide may have fluorine bonded to an aromatic ring. The aromatic ring to which fluorine is bonded may be derived from an amine or an acid halide.
The gas separation membrane module can be utilized in a gas separation method to selectively permeate a light gas such as hydrogen or helium to increase the concentration. That is, the gas separation method includes:
In the gas separation method, the spiral gas separation membrane module described above can be housed in the pressure vessel and used. That is, a mixed gas is fed to the gas separation membrane module and separated into permeate gas and concentrated gas, whereby a specific gas is separated from the feed gas. At this time, the feed gas may be fed to the gas separation membrane or its module by raising the pressure with a compressor, or the permeate side of the gas separation membrane or its module may be depressurized by a pump. Further, gas separation may be performed by disposing the modules described above over a plurality of stages. In using a plural-stage modules, either concentrated gas or permeate gas in the previous-stage module may be fed to the subsequent-stage module. In addition, concentrated gas or permeate gas in the subsequent-stage module may be mixed with the feed gas in the previous-stage module. At the time of feeding permeate gas or concentrated gas to the subsequent-stage module, the permeate gas or the concentrated gas may be pressurized by the compressor.
The gas feed pressure is not particularly limited, and is preferably 0.1 MPa to 2.5 MPa. When the gas feed pressure is 0.1 MPa or more, the gas permeation rate increases, whereas when the gas feed pressure is 2.5 MPa or less, the gas separation membrane or its module member can be prevented from undergoing pressure deformation. The value of “pressure at feed side/pressure at permeate side” is also not particularly limited, and is preferably 2 to 20. When the value of “pressure at feed side/pressure at permeate side” is 2 or more, the gas permeation rate can be increased, whereas when the value of “pressure at feed side/pressure at permeate side” is 20 or less, the power cost of the compressor for the feed side or the pump for the permeate side can be saved.
The gas feed temperature is not particularly limited, and is preferably 0° C. to 200° C., and more preferably 25° C. to 180° C. When the temperature is 25° C. or more, good gas permeability is obtained, whereas when the temperature is 180° C. or less, it is possible to prevent thermal deformation of the module member.
Hereinafter, our modules will be described in more detail with reference to Examples, but this disclosure is not limited thereto at all.
As the channel material A, a polypropylene net (A-1) obtained by melt molding with a rotary die was used.
As the channel material B, the following plain weave meshes were used:
As the channel material C, the following three kinds of nonwoven fabrics were used:
An unstretched polypropylene film (Torayfan (registered trademark) manufactured by Toray Industries, Inc.) was subjected to imprint processing and CO2 laser processing, thereby obtaining a rugged sheet having through-holes. Specifically, the unstretched polypropylene film was sandwiched between metallic molds having grooves formed by cutting, subjected to pressure keeping at 140° C. and 15 MPa for 2 minutes, cooled at 40° C., and then taken out from the molds. Subsequently, recesses in the ruggedly were subjected to laser processing using the 3D-Axis CO2 Laser Marker MLZ9500, thereby obtaining through-holes. The through-holes had a diameter of 600 μm, and were provided at a pitch of 2 mm in each groove. In the table, the channel material was indicated by D-1.
The surface of the channel material was observed at a magnification of 100 times using a high-precision shape measurement system KS-1100 manufactured by KEYENCE CORPORATION, and the areas and circumferential lengths of 30 pores randomly extracted were measured. From the measured values, the circle equivalent diameters represented by “4× area of pore in surface direction of channel material/circumferential length of the pore” were calculated. An average value of the 30 circle equivalent diameters thus obtained was calculated. An average value of circle equivalent diameters in the back surface of the channel material was calculated in the same manner as described above. The front surface and the back surface simply mean one surface and the other surface, respectively, and do not refer to a specific surface.
The surface of the nonwoven fabric was photographed at a magnification of 100 times using a high-precision shape measurement system KS-1100 manufactured by KEYENCE CORPORATION, and the resulting image was processed to black and white with a texture value of 0. Subsequently, the obtained digital image was analyzed with image analysis software (ImageJ) to measure the pore area and the pore circumferential length. From the obtained values, the average value of the circle equivalent diameters was calculated in the same manner as in the mesh. The same operation was performed on both surfaces of the channel material.
The thicknesses at 30 randomly selected places were measured using a Digimatic indicator (product number 547-301 manufactured by Mitutoyo Corporation), and the average value of the thicknesses was defined as the thickness.
Two center pipes were prepared, permeate channel materials were cut into a width of 300 mm and a length of 1200 mm, and both ends of respective permeate channel materials in the length direction were attached to the two center pipes, respectively, using a double-sided tape (NICETACK NW-20 manufactured by NICHIBAN Co., Ltd.). Meanwhile, one center pipe was fixed at both ends, a knot was provided in the other center pipe with a PP rope threaded through a hollow portion, and a standard mechanical force gauge (PS-100N manufactured by IMADA CO., LTD.) was installed on the knot. Then, the permeate channel material A was pulled in the horizontal direction, and the tension when the permeate channel material A was broken was measured with the standard mechanical force gauge.
A dimethylformamide (DMF) solution containing 15 mass % of polysulfone was cast on a nonwoven fabric (air permeability: 1.0 cc/cm/sec) formed of polyester fibers produced by a papermaking method at room temperature (25° C.) and with an application thickness of 190 μn, and then immediately immersed in pure water for 5 minutes to form a porous support on the nonwoven fabric as a substrate.
Next, the substrate having the porous support formed thereon was immersed for 10 seconds in an aqueous solution in which 5.0 mass % of 2-ethyl piperazine, 500 ppm of sodium dodecyl diphenyl ether disulfonate and 2.0 mass % of trisodium phosphate were dissolved, and then nitrogen was blown from an air nozzle to remove an excessive aqueous solution. Subsequently, an n-decane solution containing 0.2 mass % of trimesic acid chloride which had been heated to 70° C. was uniformly applied to the surface of the porous support, and held at a membrane surface temperature of 60° C. for 3 seconds. Thereafter, the membrane surface temperature was cooled to 10° C., and the porous support was allowed to stand for 1 minute in an air atmosphere while this temperature was maintained, thereby forming a separation functional layer. The obtained composite semipermeable membrane was vertically held to remove the liquid, and washed with pure water at 60° C. for 2 minutes to obtain a separation membrane.
The obtained separation membrane was cut into a width of 300 mm and air-dried in a greenhouse at 25° C. Thereafter, the separation membrane was folded while changing the separation membrane length according to the thickness of the channel material (i.e., as the thickness of the channel material decreases, the separation membrane becomes longer, and the area increases), and the feed channel material shown in Table 1 was arranged to be sandwiched between the folded surfaces of the separation membrane. Further, the permeate channel material was arranged on the surface of the separation membrane on the side opposite to the side where the feed channel material was arranged, an adhesive was applied to three sides of the end of the permeate channel material, and a separation membrane unit (the number of leaves: 3) as a laminate of the permeate channel material, the separation membrane, and the feed channel material was spirally wound around an ABS resin-made water collecting pipe (width: 300 mm, diameter: 17 mm, 80 pores×2 rows of straight lines). After that, the obtained module was rotated by 50 turns while applying a load of 10 kg/300 mm with a contact pressure roller. Finally, the edges of both ends of the module were cut, and the tape was wound only on both the ends of the module to which the end plates were attached, and the diameter of the region was adjusted to 2.5 inches to produce a gas separation membrane module V.
One side of a permeate channel material A was bonded to an ABS resin-made center pipe (width: 300 mm, diameter: 17 mm, 80 pores×2 rows of straight lines) with an adhesive. A first permeate channel material B was bonded onto the permeate channel material A, and another permeate channel material B was bonded onto the first permeate channel material B, and this process was repeated to produce a laminate of permeate channel materials as shown in
The separation membrane air-dried in a greenhouse at 25° C. was wound 3 times around a rod having a diameter of 17 mm, and held for 24 hours. Thereafter, the separation membrane was stretched out and cut into a circular shape having an effective membrane area of 25 cm2. The resulting separation membrane was attached to a permeation cell separated into two chambers of the feed side and the permeate side, and a feed gas containing 0.95 mol % of hydrogen and 5 mol % of oxygen was fed at 100 mL/min at a pressure of 0.1 MPa and a temperature of 25° C. While the chamber of the permeate side was sucked by a diaphragm pump, the operation was performed in a state where a difference between the pressure at the feed side and the pressure at the permeate side was 0.1 MPa. After the operation for 30 minutes, a permeate gas (i.e., a mixed gas of hydrogen and oxygen) was sent to gas chromatography having a thermal conductivity detector (TCD), the concentration of the permeate gas in the mixed gas was analyzed, and the permeance of hydrogen and oxygen was calculated. The hydrogen permeance was divided by the oxygen permeance to calculate the hydrogen/oxygen selectivity of the separation membrane.
End plates were attached to both ends of the gas separation membrane module, the module was housed in a pressure vessel (R2514B300E manufactured by Harbin ROPV Industrial Co., Ltd.), and high purity hydrogen gas was fed as a feed gas at a temperature of 25° C. and 10 L/min. The operation was performed such that the chamber of the permeate side was sucked by a diaphragm pump so that a difference between the inlet pressure at the feed side and the outlet pressure at the permeate side was 0.1 MPa. After the operation for 30 minutes, a permeate gas (i.e., a mixed gas of hydrogen and oxygen) was sent to gas chromatography having a thermal conductivity detector (TCD), the hydrogen concentration of permeate gas in the mixed gas was analyzed, and the permeance of hydrogen was calculated. Next, the same measurement was performed using oxygen as the feed gas, and the oxygen permeance was calculated. Then, the obtained oxygen permeance was divided by the hydrogen permeance to obtain hydrogen/oxygen selectivity of the gas separation membrane module.
The hydrogen/oxygen selectivity of the gas separation membrane module with respect to the hydrogen/oxygen selectivity of the separation membrane described above was calculated and defined as loading properties. Hence, as the calculated value is closer to 1, even when stress is applied to the outer periphery of the gas separation membrane module, the damage of the separation membrane is small and the gas separation membrane module has excellent loading properties into a pressure vessel.
The tension applied to the permeate channel material during winding was set to 5 kg/300 mm (49 N/300 mm), and 30 permeate channel materials were manually wound. The obtained gas separation membrane module was disassembled to take out a total of 300 separation membrane units. The feed channel material and the permeate channel obtained by removing separation membrane where no adhesive was applied were observed. When the number of the channel materials in which breakage or wrinkling occurred was 10 or less was evaluated as A, where the number of the channel materials in which breakage or wrinkling occurred was 11 or more and 20 or less was evaluated as B, where the number of the channel materials in which breakage or wrinkling occurred was 21 or more and 50 or less was evaluated as C, and where the number of the channel materials in which breakage or wrinkling occurred was 50 or more was evaluated as D.
The hydrogen permeation amount per minute was calculated from the hydrogen permeance measured by the hydrogen/oxygen selectivity of the gas separation membrane module, and the hydrogen permeation amount was divided by the feed amount (5.7 L/min) of hydrogen in the feed gas. The obtained value was expressed as a percentage and was defined as the hydrogen recovery rate.
A gas separation membrane module V was produced and evaluated, and the results were as shown in Table 1.
Gas separation membrane modules were produced in the same manner as in Example 1 except that the feed channel material and the permeate channel material were changed as shown in Tables 1 and 2. That is, gas separation membrane modules V each having one kind of permeate channel material were produced. The obtained gas separation membrane modules V were evaluated, and the results were as shown in Tables 1 and 2.
Gas separation membrane modules V were produced in the same manner as in Example 1 except that the feed channel material and the permeate channel material were changed as shown in Table 2.
The obtained gas separation membrane modules V were evaluated, and the results were as shown in Table 2.
In Comparative Examples 1 to 3, since the average pore size of the channel material was large, the separation membrane fell into the average pore size of the channel material due to the load of a contact pressure roll, and the separation membrane was broken. The loading properties were deteriorated as the hydrogen/oxygen selectivity gets lowered.
The feed channel material and the permeate channel material were as shown in Tables 3 and 4, and gas separation membrane modules W each including two kinds of permeate channel materials were produced. The obtained gas separation membrane modules W were evaluated, and the results were as shown in Tables 3 and 4.
As is apparent from the results shown in Tables 1 to 4, the gas separation membrane modules in Examples 1 to 17 have high loading properties to a pressure vessel and high winding stability while increasing the filling amount of the gas separation membrane.
Our gas separation membrane modules can be suitably used for separation of a mixed gas and the like.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-157775 | Aug 2019 | JP | national |
| 2019-178654 | Sep 2019 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2020/023601 | 6/16/2020 | WO |
