JP2001219025A - Gas separating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas separation membrane capable of separating gases in high efficiency when a gaseous mixture of relatively low pressure is supplied to a gas separation membrane module, to provide an economical gas separating method having only small adverse affects on the durability of the gas separation membrane module and, in particular, to provide a dehydrating method of a water-organic material solution which is economical, has only a small adverse effects on the durability of the gas separation membrane module and which can yield organic material vapor reduced in steam content by selectively separating the steam from the gaseous mixture obtained by vaporizing a solution containing water and organic material. SOLUTION: The highly efficient and economical gas separation is attained by supplying a gaseous mixture heated to a high temperature to the inside of a hollow fiber of a supply gas/carrier gas counter flow type gas separation membrane module having a specified structure at <=5.0 kg/cm2 pressure and performing gas separation in a state in which the pressure of the outside (permeation side) is reduced to 1-500 mmHg.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for separating a gas having a high permeability from a mixture of two or more gases using a gas separation membrane. Specifically, a gas mixture containing a first gas having a high permeability and a second gas having a low permeability is heated to a high temperature, and a gas mixture membrane hollow fiber having a membrane filling rate of 30% or more is focused in a crossed arrangement. The carrier gas is supplied into the hollow fiber of the gas separation membrane module containing the bundle at a supply pressure of 5.0 kg / cm ² G (hereinafter referred to as “gauge pressure”) or less, and the carrier gas is supplied to substantially the center of the hollow fiber bundle. The present invention relates to a gas separation method in which a gas having a high permeability is selectively separated from a gas mixture while the outside (permeation side) is circulated countercurrently to a mixture and the permeation side is set in a reduced pressure state.

The present invention also relates to a gas separation membrane containing a gas mixture heated to a high temperature containing water vapor and organic vapor in a crossed arrangement and containing a gas separation membrane hollow fiber bundle having a membrane filling rate of 30% or more. 5.0kg / cm into the hollow fiber of the module
^The carrier gas is supplied at a supply pressure of ² G or less, the carrier gas is supplied to substantially the center of the hollow fiber bundle, the outside (permeate side) of the hollow fiber is circulated in a countercurrent to the mixture, and the permeate side is depressurized. The present invention relates to a method for dehydrating a water-organic solution, which comprises selectively separating water vapor from a gas mixture containing water vapor and organic vapor to obtain an organic vapor having a reduced water vapor content.

[0003]

2. Description of the Related Art A gas separation method for selectively permeating and separating a specific gas component from a gas mixture by a gas separation membrane is used in many applications as an efficient and economical method. In many of these cases, high efficiency gas separation is achieved by supplying the gas mixture at high pressure. Since the permeation amount of the permeated component gas permeating the gas separation membrane is proportional to the partial pressure difference of the permeated component gas on both sides of the gas separation membrane,
By supplying the gas mixture at a higher pressure, the efficiency of gas separation can be easily increased. For this reason, for example, in the case of hydrogen separation, it is supplied at a high pressure of about 100 kg / cm ² G, or in the case of separating nitrogen gas and oxygen gas from air, it is supplied at 1 kg / cm ² G.
By supplying at a high pressure of 0 kg / cm ² G or more, highly efficient gas separation is achieved.

However, in a case where a specific component is permeated and separated by a gas separation membrane from a gas mixture obtained by heating and evaporating a solution that is liquid at normal temperature and atmospheric pressure, the gas separation efficiency is increased by supplying the gas mixture at a high pressure. To increase the temperature, the temperature of the gas mixture must be higher than at atmospheric pressure (because the boiling point of the high-pressure gas mixture rises), and the heat resistance of the gas separation membrane and the gas separation membrane module is reduced. Exceeding the temperature makes the gas mixture impractical, or the high pressure and high temperature of the gas mixture adversely affects the durability of the gas separation membrane and the gas separation membrane module, causing practical problems. Further, in order to obtain a gas mixture having a higher pressure and a higher temperature as described above, a greater amount of energy is consumed, which causes a problem in terms of economy.

Under such circumstances, conventionally, as a method for dehydrating an organic substance aqueous solution, as described in JP-A-63-267415, an aqueous solution containing an organic substance is vaporized to contain an organic substance vapor and water vapor. A gas mixture is generated, and then the gas mixture is selectively permeated and separated at a temperature of 70 ° C. or more at a temperature of 70 ° C. or higher while contacting one side of the aromatic polyimide gas separation membrane, thereby reducing the water vapor content. A method for dehydrating and concentrating an organic aqueous solution comprising obtaining a reduced organic vapor-containing gas mixture has been proposed, in which case the permeate side of the separation membrane is maintained at a high level of reduced pressure to selectively remove water vapor from the gas mixture. The method for permeation and separation is described in Examples and the like, and instead of keeping the permeate side in a reduced pressure state, dry gas is passed along the membrane surface on the permeate side. Only by circulating the carrier gas, a method for selectively transmitting and separating the water vapor it is described as such example.

Also, Japanese Patent No. 2743346 discloses that
A solution containing water and organic matter is vaporized to produce a mixed gas containing water vapor and organic matter vapor, and then a) a water vapor transmission rate ( _P'H2O ) of 1 × 10 ^-5 cm ³ / c
m or ² · sec · cmHg or more, b) transmission speed ratio 'and _H2O) organic vapor permeation rate (P' water vapor transmission rate (P and _{org) (P 'H2O / P} ' org) is 1
The above-mentioned gas mixture is supplied at a temperature of 70 ° C. or more to a separation membrane module containing an aromatic polyimide separation membrane that is at least 00, and further, in the separation membrane module,
The gas mixture is brought into contact with the supply side of the separation membrane, while the permeate side of the separation membrane is brought to a reduced pressure of 50 to 500 mmHg, and an inert dry gas or a non-permeated vapor discharged from the separation membrane module is discharged. While partially circulating as a carrier gas, water vapor is selectively permeated from the supply side to the permeation side of the separation membrane to separate water vapor from the gas mixture, thereby obtaining an organic vapor having a reduced water vapor content. A method for dehydrating a water-organic solution is disclosed. Further, as an example, a method is disclosed in which a gas mixture obtained by evaporating a solution containing water and an organic substance by an evaporator is superheated by a heater and then supplied to a separation membrane module.

Although the above-mentioned method has made it possible to efficiently dehydrate a water-organic substance solution, there is a need for a more efficient method of dehydrating water-organic substance vapor with a higher efficiency. Further, there is a need for a method of separating a gas having a higher efficiency and a higher membrane permeability from a gas mixture as well as a water-organic vapor. In particular, while the supply pressure of the gas mixture is relatively low (and thus the supply temperature is relatively low),
There is a demand for a gas separation method capable of high-efficiency gas separation and having little adverse effect on the durability of a gas separation membrane and a gas separation membrane module, and even a gas mixture containing a high-boiling organic compound, There is a need for a highly efficient and economical gas separation method that has little adverse effect on the durability of the gas separation membrane module.

On the other hand, with respect to the structure of the separation membrane module, Japanese Patent Publication No. 60-13722 discloses that a hollow fiber having selective permeability to a fluid is formed on a core tube without making a round in the circumferential direction of the core tube. A separation membrane device which is arranged so as to reach from the end to the other end, and the hollow fibers reaching the ends are folded back at the ends and sequentially arranged to form hollow fiber layers cross-laminated on the core tube. Is disclosed. However, the device disclosed in the above publication is one in which the processing fluid is supplied to the outside of the hollow fiber, and the fluid uniformly flows through the space outside the hollow fiber. It is used for treating a liquid such as removing salt from salt water, and there is no mention of a case where a gas mixture is supplied into the hollow fiber.

[0009] Japanese Patent Publication No. 6-91932 discloses that a specific gas component (for example, a gas mixture) is contained in a cylindrical container having a raw material gas inlet, a permeated gas outlet, and a non-permeated gas outlet. A special thread bundle assembly formed from a thread bundle of hollow fibers that has the ability to selectively permeate hydrogen gas components, etc. A gas separation membrane module coated with a material is disclosed. However, the module disclosed in the above publication is applied to the recovery of hydrogen and the like, and the permeate side of the separation membrane is configured to only discharge the permeated gas, and the gas mixture containing the water vapor and the organic vapor is used. As in the case of separating water vapor from
This method cannot be applied to the case where the permeate side of the separation membrane is depressurized and the carrier gas flows.

[0010] Furthermore, Japanese Patent Publication No. 7-79954 discloses that
In a cylindrical container having a raw material gas inlet, a permeated gas outlet and a non-permeated gas outlet, a gas separation membrane module having a plurality of hollow fiber bundles having gas separation performance, in a substantially central portion of the hollow fiber bundle, There is disclosed a structure having a core tube communicating with a non-permeate gas outlet having a communication hole formed therein, and a tubular partition plate arranged along the hollow fibers in a hollow fiber bundle. An object of the present invention is to increase the gas flow path while maintaining the length of the hollow fiber-shaped separation membrane, and to increase the supply linear velocity of the raw material gas. However, since there is a space between the outside of the hollow fiber bundle and the module container, the gas is short-passed in that space, making it difficult for the gas to pass effectively between the hollow fibers, and the flow direction of the gas inside the hollow fiber. There is a part where the gas separation efficiency cannot be increased as compared with the case of the counterflow since there is a portion where the flow direction of the outside and the outside is the same direction.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a gas mixture at high pressure, and therefore as a gas at a higher temperature than at atmospheric pressure, consumes more energy and is not economical. When the gas mixture is supplied in a relatively low-pressure state, and thus in a high-pressure state, overcoming the problem that the durability of the gas separation membrane and the gas separation membrane module is adversely affected and is not practically preferable. The present invention provides a high-efficiency and economical gas separation method that enables highly efficient gas separation even when supplied at a relatively low temperature, and has little adverse effect on the durability of a gas separation membrane and a gas separation membrane module. The purpose is to: In particular, an economical and gaseous method comprising selectively separating water vapor from a gas mixture containing water vapor and organic vapor generated by vaporizing a solution containing water and organic matter to obtain an organic vapor having a reduced water vapor content. It is an object of the present invention to provide a method for dehydrating a water-organic substance solution that does not adversely affect the durability of a separation membrane module.

[0012]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned situation, and the present inventors utilize the entire hollow fiber bundle in a gas separation membrane module more effectively for separation. As a result of various studies on methods and gas separation conditions, the present invention was created.

That is, the present invention relates to a gas mixture containing a first gas having high permeability and a second gas having low permeability having a permeation rate ratio of 50 or more to a gas separation membrane and heated to a high temperature, 4. into a hollow fiber of a supply gas / carrier gas counter-flow hollow fiber gas separation membrane module containing a hollow fiber bundle having the following features (1) and (2) in a cylindrical container;
It is supplied at a supply pressure of 0 kg / cm ² G (gauge pressure) or less. (1) The whole hollow fiber bundle is bundled so as to have an axis substantially in the same direction as the axis of the module. The constituting hollow fibers are bundled so as to alternately cross each other at an angle of 5 to 30 degrees with respect to the axis (module axis) direction of the hollow fiber bundle for every 1 to 100 fibers. (2) Hollow fibers The membrane packing ratio of the bundle is 30% or more. Further, a carrier gas is introduced into a substantially central portion of the hollow fiber bundle and circulated along the outside (permeate side) of the hollow fiber and outside of the hollow fiber (permeate side). A pressure of 1 to 500 mmHg to selectively permeate at least a first gas from the gas mixture through a membrane, thereby obtaining a second gas having a reduced first gas. About.

Further, the present invention relates to the above gas separation method, wherein the outer peripheral portion of the hollow fiber bundle of the supply gas / carrier gas countercurrent type hollow fiber gas separation membrane module is coated with a film-like substance.

Further, a core tube having a communication hole for introducing a carrier gas is arranged at substantially the center of the hollow fiber bundle of the supply gas / carrier gas counter-flow type hollow fiber gas separation membrane module. The gas separation method described above.

Further, the gas mixture heated to a high temperature treated by the evaporator equipped with a heating device is supplied to the supply gas / carrier gas countercurrent type hollow fiber gas separation membrane module while keeping the temperature. The present invention relates to the above gas separation method.

Also, a demister (mist separator)
The gas mixture heated to a high temperature treated by the above method is supplied to a feed gas / carrier gas countercurrent hollow fiber gas separation membrane module while keeping the temperature maintained.

Further, the first gas is water vapor, the second gas is organic vapor having a boiling point of 30 to 200 ° C. at atmospheric pressure, and the temperature of the supplied gas mixture is 70 ° C. or higher. The gas separation method described above.

Further, the present invention relates to the above gas separation method, wherein the vapor of the organic substance is vapor of at least one organic substance selected from the group consisting of acetone, methyl ethyl ketone, ethanol, butanol and propanol.

Further, the present invention relates to the above gas separation method, wherein a part of the unpermeated gas obtained by separating the first gas is circulated to a carrier gas supply port and used as a carrier gas.

Further, the present invention relates to the above gas separation method, wherein the carrier gas is nitrogen gas.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the gas separation method of the present invention will be described in detail. In the gas separation membrane module used in the gas separation method of the present invention, the supplied gas mixture flows inside the hollow fiber while contacting the membrane, and at the same time, the carrier gas flows along the outside of the hollow fiber. This is a carrier gas counterflow type hollow fiber gas separation membrane module in which a hollow fiber bundle having the following features (1) and (2) is housed in a cylindrical container. (1) The hollow fiber bundle is bundled in a direction substantially the same as the axial direction of the module as a bundle, but every 1 to 100 hollow fibers are aligned with respect to the axial direction of the hollow fiber bundle (module axis). 5-
(2) Hollow fiber bundles have a membrane filling ratio of 30% or more.

FIG. 1 is a schematic diagram showing the outline of a method for bundling the hollow fibers so that they are alternately arranged. 1-100
A hollow fiber (indicated by a single line in FIG. 1) 1 is distributed to a core tube 2 by a yarn distribution guide 3 which reciprocates at a constant speed in an axial direction of a tubular material (core tube) 2 serving as a core. At the same time, the core tube 2 rotates at a constant speed. Therefore, the hollow fibers 1 are not arranged parallel to the axis, but are arranged at an angle as much as the rotation of the core tube with respect to the axial direction. When the yarn distribution reaches one end, the hollow fiber 1 is fixed there, and the yarn distribution guide 3 turns back in the opposite direction to perform further yarn distribution. Since the core tube 2 continues to rotate in the same direction, the yarn is distributed at an angle which is the same as the previous direction and just opposite to the axial direction. By repeating this, the hollow fibers 1 to be arranged are alternately arranged alternately on the hollow fibers 1 arranged at opposite angles and are bundled into a hollow fiber bundle.

The bundle of hollow fibers thus bundled is obtained by removing the core tube or fixing both ends of the bundle with a hardening resin such as an epoxy resin while keeping the core tube 2 substantially at the center of the bundle. At the same time, the folded portions of both ends of the hollow fiber are cut, and the hollow fibers are kept open at both ends to form a hollow fiber bundle fixed by the tube sheet 4. FIG. 2 schematically shows an example of the hollow fiber bundle assembly manufactured as described above.

The hollow fiber bundles of the gas separation membrane module used in the present invention are bundled so as to be alternately arranged by the above-mentioned method. If the hollow fibers are arranged in parallel in the axial direction without being crossed, the outer surfaces of the hollow fibers are likely to come into contact with each other, and the effective membrane area is reduced. Furthermore, during use, the hollow fibers are unevenly distributed, and unnecessarily large voids are generated, so that a short path of the carrier gas is easily generated, and the effect of the carrier gas cannot be sufficiently exhibited. On the other hand, if the cross-arrangement is performed as described above, the adjacent hollow fibers rarely contact each other only at small contact points to reduce the effective membrane area, and since the hollow fibers hold each other, the space between the hollow fibers is reduced. Since a uniform space is arranged and maintained during use, the carrier gas can be uniformly distributed throughout the hollow fiber bundle, and the effect of the carrier gas can be exhibited more effectively. In the present invention, the bundles are alternately crossed at an angle of 5 to 30 degrees, particularly preferably at an angle of 10 to 25 degrees, with respect to the axis of the hollow fiber bundle (the axis of the module). If the angle with respect to the axial direction is less than 5 degrees, there is practically no difference from the one arranged in parallel. On the other hand, when the angle with respect to the axial direction is 3
If it exceeds 0 degree, the number of contact points increases and the film filling rate decreases,
The carrier gas is no longer countercurrent and the effect of the carrier gas cannot be fully exerted. Also, the number of hollow fibers to be distributed is 1 to 100 (preferably 1 to 50).
(Especially, preferably 1 to 30) when a relatively large bundle of hollow fibers is arranged, the above-mentioned effect can be sufficiently obtained even if the hollow fibers are grouped and arranged alternately and crosswise. This is because the manufacturing efficiency is high.

Further, in the gas separation membrane module used in the gas separation method of the present invention, the membrane filling rate of the hollow fiber bundle is 30% or more (preferably 35% or more). The effective membrane area of the hollow fiber bundle is a percentage of the total cross-sectional area of the hollow fiber in the cross-sectional area of the hollow fiber bundle. When the core tube is disposed substantially at the center of the hollow fiber bundle and the outer peripheral portion of the hollow fiber bundle is coated with a film-like substance, the cross-sectional area of the hollow fiber bundle is the inside area covered with the film-like substance. This is the cross-sectional area excluding the core tube. Since the gas separation efficiency of the module increases as the effective membrane area increases, it is preferable that the membrane filling rate is high. If it is less than 30%, it becomes difficult to increase the gas separation efficiency of the module. Further, when the membrane filling rate is less than 30%, a large space is formed between the hollow fibers, so that there is no difference even if the hollow fiber bundles are not arranged in a crossed arrangement.

[0027] In the gas separation method of the present invention, the gas mixture is not condensed until the gas mixture is supplied to the gas separation membrane module, flows inside the hollow fiber and is discharged from the non-permeate gas outlet. It is supplied to the gas separation membrane module as a gas mixture heated to a high temperature. Specifically, the solution mixture is vaporized by an evaporator equipped with a heating device or the like, and is simultaneously subjected to a heat treatment to form a gas mixture heated to a temperature higher than or equal to a degree not condensing while flowing through the gas separation membrane module, and maintaining the temperature. Then, the gas mixture is supplied to the gas separation membrane module, or the vaporized gas mixture is supplied to the gas separation membrane module after performing a process of lowering the pressure while maintaining the temperature. The pressure may be reduced by a normal pressure reducing valve or the like, or a vaporized gas mixture may be treated with a demister (mist separator) or the like to remove mist and simultaneously generate pressure loss to reduce pressure. . The above-described solution mixture may be vaporized by an evaporator equipped with a heating device or the like, and the heat treatment and the treatment for lowering the pressure may be performed simultaneously. The gas mixture after the treatment is a gas mixture having a pressure less than the saturated vapor pressure at that temperature, and is supplied to the gas separation membrane module while maintaining that state (specifically, keeping the temperature). Therefore, it is not condensed until it passes through the hollow fiber and is discharged from the non-permeate gas outlet. The untreated gas mixture is likely to be condensed during the passage through the hollow fiber and discharged from the non-permeate gas outlet, and if condensed, the gas separation efficiency is reduced and the durability of the gas separation membrane is adversely affected. give.

In the present invention, the supply pressure of the gas mixture supplied to the gas separation membrane module is 5 kg / cm.
² G or less, preferably 3 kg / cm ² G or less, particularly preferably 2 kg / cm ² G or less. By setting the supply pressure of the supplied gas mixture to a relatively low pressure as described above, it becomes possible to make the temperature of the supplied gas mixture relatively low. Even if the gas mixture is supplied at such a relatively low pressure, the method of the present invention can separate the permeate gas with high efficiency.

FIG. 3 shows a core tube 6 having a communication hole 5 for introducing a carrier gas into a substantially central portion of a hollow fiber bundle 13 which is an example of a gas separation membrane module used in the gas separation method of the present invention. FIG. 3 is a cross-sectional view schematically showing a gas separation membrane module having a hollow fiber bundle 13 and an outer peripheral portion of which is covered with a film-like substance 7. In this separation membrane module,
The outer frame is formed of a cylindrical container having a supply gas inlet 8, a carrier gas inlet 9, a permeated gas outlet 10, and a non-permeate gas outlet 11, and a carrier gas is provided substantially in the center of the cylindrical container. A hollow fiber bundle 13 composed of a large number of hollow fibers having a core tube 6 having a communication hole 5 for introduction and having an outer peripheral portion covered with a film-like substance 7 is accommodated therein.
As described above, the hollow fiber bundle 13 is formed by alternately arranging hollow fibers in a bundle, and is bundled at one end on the permeable gas discharge port side by the second tube sheet 15 made of a curable resin. At the other end on the gas outlet side side, each is fixed by a first tube sheet 14 also made of a curable resin to form a hollow fiber bundle assembly as a whole. In this hollow fiber bundle assembly, each hollow fiber constituting the fiber bundle 13 is connected to the tube sheets 14 and 1.
5 and is fixed in an open state. Further, the outer peripheral portion of the hollow fiber bundle 13 is coated with a film material at a position where the carrier gas is introduced and discharged. The flow of the supply gas and the carrier gas in the module is configured to be countercurrent across the separation membrane.

In the example shown in FIG. 3, the core tube 6 penetrates through the first tube plate 14 on the side of the carrier gas inlet 9 and is disposed substantially in the center of the bundle of hollow fibers in the axial direction of the hollow fibers. A communication hole 5 is formed in the core tube for communicating between the inside of the core tube located near the first tube sheet 14 and the inside of the hollow fiber bundle. In this case, the end of the core tube 6 is closed and buried in the second tube sheet 15, but it is not always necessary to be fixed to the tube sheet. Preferably, there is a gap. In addition, the substantially central portion of the hollow fiber bundle here is intended to spread the carrier gas over the entire hollow fiber bundle, and it is sufficient that the purpose is achieved, and is limited to a strict central portion. Not something.

In the above example, the tip of the core tube is buried in the second tube sheet 15 on the side of the permeated gas discharge port 10, but the gas separation membrane module used in the gas separation method of the present invention is shown. The length is not limited to this, and may be, for example, as long as it penetrates the first tube sheet 14 on the side of the carrier gas inlet 9 as shown in FIG.

In the gas separation method of the present invention, the outside (permeation side) of the hollow fiber is 1 to 500 mmHg (preferably 1 to 30 mmHg).
0 mmHg, particularly preferably 1 to 200 mmHg). Since the amount of permeated gas passing through the membrane is proportional to the partial pressure difference of the permeated gas sandwiching the membrane, setting the outside (permeation side) of the hollow fiber to a reduced pressure promotes gas permeation. In the gas separation method of the present invention, since the supply pressure of the supply gas is relatively low, the outside (permeate side) of the hollow fiber is depressurized to promote gas permeation. When the reduced pressure state is 500 mmHg or more, the effect of promotion becomes small. Generating a reduced pressure of 1 mmHg or less is not practical because special means is required.

As the hollow fiber membrane of the gas separation membrane module, an aromatic polyimide hollow fiber membrane is optimal because of its high separation performance and excellent solvent resistance and heat resistance.

The gas to be separated is not particularly limited as long as it is a gas mixture containing a first gas having high permeability and a second gas having low permeability having a ratio of permeation speed to the separation membrane of 50 or more. It is not something to be done. When the first gas is water vapor and the second gas is organic vapor, the present invention is a method for dehydrating organic vapor. When the second gas is an organic gas whose boiling point at atmospheric pressure is 30 to 200 ° C., the method of the present invention is useful because it can be performed more efficiently than other dehydration methods such as distillation. In particular,
The second gas has a boiling point at atmospheric pressure of 30 to 150.
° C, specifically, when the second gas is at least one organic vapor selected from the group consisting of acetone, methyl ethyl ketone, ethanol, butanol, propanol, etc., the method of the present invention High efficiency at a relatively low temperature compared with the case of supplying at a relatively low pressure state, and thus a high pressure state, and furthermore, high stability and economical efficiency (since the durability of the gas separation membrane module is less adversely affected). Water-To provide a method of dehydrating an organic solution,
Extremely useful.

It is preferable that the ratio of the permeation rate of the gas to be separated to the specific two-component membrane is large because the effect of improving the separation efficiency is large, and if the ratio is less than 50, the separation efficiency does not increase and is not practical.

The carrier gas does not substantially contain the above-mentioned first gas component, or the partial pressure of the first gas on the permeation side across the membrane in use is the first gas on the non-permeation side. If the gas contains the first gas having a concentration lower than the partial pressure of
There is no particular limitation. For example, nitrogen, air, and the like can be used. Nitrogen is preferable because it is inert (has no side reaction), has high safety, and hardly causes reverse osmosis from the permeate side to the supply side of the membrane. It is also preferable that a part of the non-permeated gas from which the first gas is separated is circulated to the carrier gas supply port and used as the carrier gas. Further, it is also preferable to use dry air in which moisture has been removed from air by a separation membrane or nitrogen-enriched air in which oxygen has been removed in advance.

The gas separation membrane module used in the gas separation method of the present invention will be described in more detail. As long as the cylindrical container and the core tube have predetermined airtightness and pressure resistance, the material is not particularly limited, and metal, reinforced plastic,
It can be formed of plastic, ceramics, or the like.

The hollow fiber membrane is a separation membrane having a permeation speed ratio of 50 or more between a first gas having a high permeation speed and a second gas having a low permeation speed, and having a permeation speed ratio of 200 or more. And a separation membrane having a permeation speed ratio of 500 or more is particularly preferable. In the case of steam-organic vapor separation, the water vapor transmission rate ( _P'H2O ) of the hollow fiber membrane is 1 * 10 < ^-5 > cm < ³ > (STP) / cm < ² >.
sec · cmHg or more, preferably 5 × 10 ⁻¹ to 1 × 1
About 0 ^-4 cm ³ (STP) / cm ² · sec · cmHg,
More preferably, 0.5 to 5.0 × 10 ⁻³ cm ³ (ST
P) / cm at ² · sec · cmHg about, water vapor transmission rate (P _'H2O) and organic vapor transmission rate (P' permeation rate ratio of _{o rg) (P 'H2O /} P' org) is 50 or more, preferably Is 2
It is preferably an aromatic polyimide hollow fiber membrane of 00 or more, particularly preferably 500 or more. Further, as the hollow fiber membrane, an asymmetric membrane or a composite separation membrane can be suitably used. A separation membrane having a permeation speed ratio of less than 50 between the first gas having a high permeation speed and the second gas having a low permeation speed is not practical because the separation efficiency is reduced.

The curable resin constituting the resin tube sheet is required to have heat resistance and organic solvent resistance. For example, a thermosetting resin such as polyurethane resin, phenol resin and epoxy resin is preferable. be able to.

The film-like substance may be formed of any material that does not substantially permeate the supplied gas mixture or any material that is hardly permeable, for example, polyethylene, polypropylene, polyamide A plastic film of polyester, polyimide, or the like, or a film of aluminum or stainless steel can be used, and a polyimide film is particularly preferable in terms of heat resistance, solvent resistance, and workability. Further, the thickness of the film-like substance is not particularly limited, but is preferably in the range of several tens μm to several mm. Furthermore, this film-like substance
It is preferable that 70% or more of the area of the outer peripheral portion of the portion sandwiched between the two tube sheets except for the both end portions of the hollow fiber bundle is covered.

An assembly composed of a bundle of hollow fibers having a core tube at a substantially central portion and an outer peripheral portion covered with a film-like substance can be manufactured, for example, as follows. First, a hollow fiber bundle is formed by arranging hollow fibers alternately in an intersecting manner by the method described above with the core tube as the center, and a polyimide film is wound around the bundle, and the overlapping portion is glued. Next, both ends of the bundle are fixed with, for example, an epoxy resin to form a tube sheet equivalent portion. At this time, the polyimide film is also fixed together at the end corresponding to the first tube sheet side on the carrier gas inlet side, and the polyimide film is piped at the end corresponding to the second tube sheet on the permeated gas discharge outlet side. A gap is secured so that the permeated gas and the carrier gas flow out of the hollow fiber bundle to the permeated gas outlet without being fixed to the plate. Thereafter, the fixing resin at both ends of the bundle is cut, and the ends of the hollow fiber separation membrane are opened at the cut surfaces (outer end surfaces) at both ends, whereby the assembly is produced.

FIG. 5 is a schematic diagram showing an example of a method for dehydrating a water-organic solution using the gas separation method of the present invention. The water-organic solution is supplied from a tank 17 to an evaporator 19 with a heating device by a pump 18. The evaporator 19 with a heating device is provided with, for example, a heat exchanger to which a heat medium at a predetermined temperature is supplied, and the supplied water-organic solution is vaporized into steam and organic vapor, and is heated at the same time. It becomes a gas mixture heated to a high temperature. Next, the gas mixture is treated in a demister 20 while maintaining the temperature to remove mist that may be contained in the gas mixture. At this time, by passing through the demister 20, the pressure of the gas mixture decreases. The gas mixture heated to the high temperature is 5 kg / cm ² G or less (preferably 3 kg / cm ² G).
(kg / cm ² G or less, particularly preferably 2 kg / cm ² G or less) at a supply gas inlet 8 of the gas separation membrane module.
Is supplied to the gas separation membrane module 21 and circulated inside the hollow fiber. While flowing through the inside of the hollow fiber, the water vapor in the gas mixture selectively permeates through the hollow fiber membrane and flows outside (permeation side) of the hollow fiber membrane. At the same time, the carrier gas is heated to a predetermined temperature by the heater 22 as required, and the carrier gas inlet 9 of the gas separation membrane module is heated.
And is released from the communication hole 5 of the core tube to the outside (permeation side) of the hollow fiber through the core tube, and dilutes the water vapor as a carrier gas of the water vapor that has passed through the hollow fiber membrane to promote removal. The flow direction of the carrier gas and the gas mixture across the hollow fiber membrane is countercurrent. The permeated water vapor and the carrier gas are discharged from the permeated gas outlet 10 to the outside of the gas separation membrane module, cooled by the cooler 23, the water vapor is condensed into water, and the carrier gas is separated from the water vapor. The condensed water is stored in a tank 24 and discharged through a valve 25. The separated carrier gas is stored in tank 2
4. Collected through a valve 26 and a pressure reducer (ejector) 27. Further, the outside (permeation side) of the hollow fiber of the gas separation membrane module is depressurized by the decompressor (ejector) 27. In the gas separation membrane module, the non-permeate gas becomes organic vapor from which most of the water vapor has been removed, and is sent to the cooler 28 through the non-permeate gas outlet 11 of the module and condensed. The condensed organic liquid is stored in a tank 29 and collected through a valve 30.

Next, a more specific description will be given based on the example of FIG. The gas mixture heated to the high temperature is 5 kg /
Pressure of not more than cm ² G (for example, in the case of water-isopropyl alcohol, 115 to 120 ° C., 1.5 kg / cm ² G)
Then, the hollow fiber bundle of the hollow fiber bundle supplied from the supply gas inlet 8 of the gas separation membrane module and stored in the cylindrical container flows in the direction of the non-permeate gas outlet 11 while being in contact with the membrane. Water vapor selectively permeates the hollow fiber membrane by contact of the gas mixture with the membrane, and is discharged from the permeated gas outlet 10. The remaining non-permeate gas mainly composed of organic vapor is taken out from the non-permeate gas outlet 11. On the other hand, the carrier gas is introduced into the core tube 6 from the carrier gas inlet 9 and is discharged from the communication hole 5 of the core tube 6 to a substantially central portion in the hollow fiber bundle. The released carrier gas flows uniformly in the gaps between the hollow fibers formed uniformly because the hollow fiber bundles 13 are cross-arranged, and the film-like substance 7 on the outer peripheral portion of the hollow fiber bundles 13 In this way, the hollow fiber bundle 13 is prevented from flowing out of the hollow fiber bundle 13 through a short path in the middle thereof, and the hollow fiber bundle 13 uniformly flows along the hollow fiber,
It arrives at the permeated gas outlet 10 through a gap near the second tube sheet 15 that is not covered with a film-like substance. During this time,
Water vapor permeating the outside of the hollow fiber is diluted into a carrier gas and is combined with the carrier gas to form a permeated gas outlet 1
Emitted from 0. Further, in the present invention, the outside (permeate side) of the hollow fiber is evacuated through the permeated gas outlet 10, and the mixture of the water vapor and the carrier gas is discharged from the permeated gas outlet 10. Further promote. From the above, the water vapor that has passed through the hollow fiber membrane is removed very efficiently, so that the partial pressure of the water vapor on the permeation side extends over the entire area of the hollow fiber bundle 13 from the supply gas inlet 8 to the non-permeate gas outlet 11. It is kept lower than the normal supply side to promote the permeation of water vapor from the supply side to the permeation side of the membrane. As a result, the gas separation method of the present invention has extremely high separation efficiency (dewatering efficiency when removing water).

In this method, the gas mixture composed of water vapor and organic vapor which is vaporized and supplied to the gas separation membrane module is supplied to the gas separation membrane module preferably at a temperature of 70 ° C. or higher.

In this method, although not shown in FIG. 5, the water-organic solution is subjected to at least one pretreatment such as ion exchange resin treatment, distillation, or filtration before being vaporized. , Solid particles, high-boiling components, metal ions, and the like contained in the solvent may be removed. Further, after the organic vapor recovered as a non-permeate gas is condensed and liquefied in a cooler, for example, ion exchange resin treatment,
Solid particles, high-boiling components, metal ions and the like contained in the solution may be removed by at least one post-treatment such as distillation and filtration.

[0046]

Examples of the present invention will be described below.

Example 1 A water-isopropyl alcohol solution was supplied to an evaporator equipped with a heating device to generate a gas mixture and further subjected to a demister treatment to obtain 5% by weight of steam at a temperature of 125 ° C. and a pressure of 2 kg / cm ² G and isopropyl alcohol. A gas mixture of 95% by weight was obtained. This gas mixture was converted into a hollow fiber having an asymmetric structure composed of an aromatic polyimide having a structure as schematically shown in FIG.
When a gas mixture consisting of 0% by weight of isopropyl alcohol vapor is supplied at a supply pressure of ² kg / cm ² G and the pressure on the permeate side is measured at 4 mmHg, the permeation rate (P ′ _H2O ) of water vapor is 1.2 × 10 ^-3 cm ³ (STP) / cm
² · sec · cmHg, permeation rate (P ′ _IPA ) of isopropyl alcohol is 8.5 × 10 ⁻⁷ cm ³ (STP) / c
m ² · sec · cmHg) an effective membrane area 5.8 m ^2, film filling rate 38%, a flange outer diameter of 125m accommodating the hollow fiber bundle that is focused at crossover sequence of 20 degrees with respect to the axis in the cylindrical container
m, a body part outer diameter of 89 mm, a total length of 1050 mm, was introduced at a flow rate of 8.72 kg / h into a supply gas introduction port of a gas separation membrane module, and nitrogen gas heated to 125 ° C. was introduced as a carrier gas into the carrier gas introduction port at 0.43 kg. / H, and the outside of the hollow fiber (permeation side) is
The pressure was reduced to 0 mmHg. A gas containing about 45% by weight of steam is discharged from the permeated gas outlet at a flow rate of 0.97 kg / h, and a non-permeated gas is discharged at a flow rate of 8.18 from the non-permeate gas outlet.
kg / h. This unpermeated gas was cooled to 20 ° C. by a cooler, condensed, and stored in a condensate tank. This condensate has an isopropyl alcohol purity of 99.
The content was 99% by weight and the water content was 0.01% by weight. Table 1 shows the results.

Comparative Example 2 Gas separation was carried out in the same manner as in Example 1 except that the hollow fiber bundles were arranged in parallel with the axial direction. Table 1 shows the results.

Comparative Example 2 Gas separation was performed in the same manner as in Example 1 except that no carrier gas was introduced. Table 1 shows the results.

Comparative Example 3 Gas separation was carried out in the same manner as in Example 1 except that the hollow fiber bundles were arranged in parallel with the axial direction and no carrier gas was introduced. Table 1 shows the results.

Example 2 A water-isopropyl alcohol solution was supplied to an evaporator equipped with a heating device to generate a gas mixture and further subjected to a demister treatment to obtain a temperature of 110 ° C. and a pressure of 0.8 kg / cm ^2.
G was a gas mixture of 5% by weight of steam and 95% by weight of isopropyl alcohol. This gas mixture was converted into a hollow fiber having an asymmetric structure composed of an aromatic polyimide having a structure as schematically shown in FIG. 3 (a gas mixture composed of 10% by weight steam and 90% by weight isopropyl alcohol vapor at a temperature of 120 ° C.). Is supplied at a supply pressure of ² kg / cm ² G, and when the pressure on the permeation side is measured at 4 mmHg, the permeation rate (P ′ _H2O ) of water vapor is 1.2 × 10 ⁻³ cm ³ (STP) /
cm ² · sec · cm Hg, permeation rate (P ′ _IPA ) of isopropyl alcohol is 8.5 × 10 ⁻⁷ cm ³ (STP)
/ Cm ² · sec · cmHg) with an effective film area of 5.8.
A gas separation membrane module having a flange outer diameter of 125 mm, a trunk outer diameter of 89 mm, and a total length of 1050 mm, in which a hollow fiber bundle bundled in a cylindrical container with a m ² , a membrane filling rate of 38%, and a crossing arrangement of 20 degrees with respect to the axis is housed. 8.72k flow rate to supply gas inlet
g / h and heated at 110 ° C. as a carrier gas to the carrier gas inlet at 0.43 kg / h.
h, and the outside (permeation side) of the hollow fiber was evacuated to 40 mmHg by an ejector. A gas containing about 48% by weight of water vapor flows from the permeated gas outlet at a flow rate of 0.89 kg.
/ H, and a non-permeate gas was obtained from the non-permeate gas outlet at a flow rate of 8.26 kg / h. This unpermeated gas was cooled to 20 ° C. by a cooler, condensed, and stored in a condensate tank. This condensate had an isopropyl alcohol purity of 99.93% by weight and a water content of 0.07% by weight. Table 1 shows the results.

Comparative Example 4 Gas separation was carried out in the same manner as in Example 2 except that the hollow fiber bundles were arranged in parallel to the axial direction. Table 1 shows the results.

Comparative Example 5 Gas separation was carried out in the same manner as in Example 2 except that no carrier gas was introduced. Table 1 shows the results.

Comparative Example 6 Gas separation was carried out in the same manner as in Example 2 except that the hollow fiber bundles were arranged in parallel to the axial direction and no carrier gas was introduced. Table 1 shows the results.

[0055]

[Table 1]

[0056]

According to the method of the present invention, two or more kinds of gas mixtures can be supplied to a gas separation membrane module at a relatively low pressure to separate and remove specific components with high efficiency. It is a very economical gas separation method. In particular,
In the case of a gas mixture containing water vapor and an organic substance having a boiling point of 30 to 200 ° C. at atmospheric pressure, a highly efficient and economical dehydration of a water-organic substance solution which does not adversely affect the durability of the gas separation membrane module. The present invention provides a method, in which a high level of dryness (very low moisture content) of dried organic matter can be easily obtained.

[0057]

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a cross-array convergence method which is a convergence method of a hollow fiber bundle of a gas separation membrane module used in the present invention.

FIG. 2 is a schematic view showing an example of a hollow fiber bundle assembly of a gas separation membrane module used in the present invention.

FIG. 3 is a schematic sectional view showing an example of a gas separation membrane module used in the present invention.

FIG. 4 is a schematic sectional view showing another example of the gas separation membrane module used in the present invention.

FIG. 5 is a schematic view showing an example of a method for dehydrating a water-organic solution using the gas separation method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hollow fiber 2 Tubular material (core tube) which becomes core 3 Yarn distribution guide 4 Tube sheet 5 Communication hole 6 Core tube 7 Film-like substance 8 Supply gas inlet 9 Carrier gas inlet 10 Permeate gas outlet 11 Unpermeate gas discharge Outlet 12 Cylindrical container 13 Hollow fiber bundles bundled so as to be alternately cross-arranged 14 First tube sheet 15 Second tube sheet 16 Water-organic solution 17 Tank 18 Pump 19 Evaporator with heating device 20 Demister 21 Gas separation membrane Module 22 Heater 23 Cooler 24 Tank 25 Valve 26 Valve 27 Decompressor (Ejector) 28 Cooler 29 Tank 30 Valve

Claims (9)

[Claims] 1. A first gas having a high permeability and a second gas having a low permeability having a transmission speed ratio of 50 or more to a gas separation membrane.
And a gas mixture heated to a high temperature and containing a bundle of hollow fibers having the following features (1) and (2) in a cylindrical container: a supply gas / carrier gas counter-flow hollow fiber gas separation membrane. 5.0 kg / cm ² G into the hollow fiber of the module
(1) The hollow fiber bundle as a whole is bundled so as to have an axis substantially in the same direction as the axis of the module, and the hollow fibers constituting the hollow fiber bundle are Are bundled so as to alternately cross each other at an angle of 5 to 30 degrees with respect to the axis (axis of the module) of the hollow fiber bundle for every 1 to 100 fibers. (2) The membrane filling rate of the hollow fiber bundle Is 30% or more. Further, a carrier gas is introduced into a substantially central portion of the hollow fiber bundle and circulated along the outside (transmission side) of the hollow fiber, and the outside (transmission side) of the hollow fiber is 1 to 500 mmHg. A gas separation method comprising selectively passing at least a first gas from a gas mixture through a membrane in a reduced pressure state, thereby obtaining a second gas having a reduced first gas. 2. The gas separation device according to claim 1, wherein the outer periphery of the hollow fiber bundle of the supply gas / carrier gas counterflow type hollow fiber gas separation membrane module is coated with a film-like substance. Method. 3. A core tube having a communication hole for introducing a carrier gas is disposed substantially at the center of a hollow fiber bundle of a supply gas / carrier gas counterflow type hollow fiber gas separation membrane module. 3. The gas separation method according to claim 1, wherein: 4. A gas mixture heated to a high temperature treated by an evaporator equipped with a heating device is supplied to a supply gas / carrier gas counter-flow hollow fiber gas separation membrane module while keeping the temperature. The gas separation method according to claim 1. 5. A high-temperature heated gas mixture treated by a demister (mist separator) is supplied to a feed gas / carrier gas counter-flow hollow fiber gas separation membrane module while keeping the temperature. The gas separation method according to claim 1. 6. The method according to claim 1, wherein the first gas is water vapor, the second gas is organic vapor having a boiling point of 30 to 200 ° C. at atmospheric pressure, and the temperature of the gas mixture to be supplied is 70 ° C. or higher. The gas separation method according to claim 1, wherein: 7. The gas separation method according to claim 6, wherein the organic vapor is at least one organic vapor selected from the group consisting of acetone, methyl ethyl ketone, ethanol, propanol and butanol. 8. The gas separation method according to claim 1, wherein a part of the unpermeated gas from which the first gas is separated is circulated to a carrier gas supply port and used as a carrier gas. 9. The gas separation method according to claim 1, wherein the carrier gas is nitrogen gas.