JPH0471566B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a gas separation membrane structure used for gas separation based on Knudsen gas diffusion, condensable gas separation, etc. [Prior art] This type of gas separation membrane structure is disclosed in Japanese Patent Application Laid-Open No. 59-186621.
Publication No. 59-193518, Publication No. 59-193519
As disclosed in Japanese Patent Publication No. 59-193520, etc., it is a honeycomb structure having two types of large number of fluid passages that are parallel to each other at partition walls, and one fluid passage is used for the gas to be treated. The other fluid passage is configured as a flow path for a specific gas component in the gas to be treated that has passed through the partition wall. [Problems to be Solved by the Invention] Therefore, in such a gas separation membrane structure, the partition wall can only function as selective permeation from one fluid passage side to the other fluid passage side, and the unit of the structure There is a limit to the selective permeation area per volume. In addition, in such a gas separation membrane structure, for example, the downstream end of one fluid passage must be sealed and a discharge port communicating with the passage must be formed, and the upstream end of the other fluid passage must be sealed. This requires a lot of laborious work. Therefore, an object of the present invention is to configure the partition wall of a gas separation membrane structure into a multi-layer structure including a specific base material part and a gas separation membrane part, and to impart a selective permeation effect to the entire fluid passage side. The object of the present invention is to increase the selective permeation area per unit volume, improve the separation efficiency of the gas separation membrane structure, and eliminate or reduce troublesome work in manufacturing the structure. [Means for Solving the Problems] The present invention includes a large number of fluid passages surrounded by partition walls and arranged in parallel with each other, and the partition walls substantially connect a porous base material portion and the fluid passage side. A gas separation membrane structure comprising a gas separation membrane part located entirely on the base part and integral with the base part, the amount of pure nitrogen permeation through the base part being 20 times or more as the amount of pure nitrogen permeation through the partition wall, and the average pore diameter of the gas separation membrane portion is 1000 Å or less, and the fluid to be treated flows through the fluid passage, and a specific gas component in the fluid to be treated is concentrated and permeates through the gas separation membrane portion. It is characterized in that the gas is diffused in the base material part and discharged to the outside of the structure through a gas discharge part of the base material part. Therefore, in the gas separation membrane structure according to the present invention, it is preferable that the amount of pure nitrogen permeated through the base portion is 50 times or more the amount of pure nitrogen permeated through the partition wall,
In addition, the amount of pure nitrogen permeation through the partition wall is 100mol/ ^m2 .
It is preferable that it is hr・atm or less. Note that the amount of pure nitrogen permeation quantifies the diffusion resistance of partition walls, base material parts, gas separation membrane parts, etc. Further, in the gas separation membrane structure according to the present invention, the gas discharge section may be provided on a side surface or one end of the outer wall, and the gas discharge section may extend inward from the outer wall. Furthermore, the gas separation membrane structure according to the present invention is a honeycomb structure in which the cross-sectional shape of the fluid passages is triangular, quadrangular, other polygonal, circular, oval, etc., and the gas separation membrane structure is a honeycomb structure that prevents mixing between the fluid passages. In order to improve the performance, a cut may be made in the partition wall to provide communication between the fluid passages, and the partition wall is formed of ceramic, sintered metal, porous glass, porous plastic, or the like. When the gas separation membrane structure is made of ceramic, the ceramic raw materials include alumina, silica,
Appropriate materials such as mullite, cordierite, zirconia, titania, etc. are used, and the honeycomb structure consisting only of the base material is made by kneading a mixture of fine powder of ceramic raw materials with an organic binder and a plasticizer, through a large number of slits. It is formed by extruding from a die equipped with and firing it. Also,
The gas separation membrane portion is integrally formed on the inner periphery of the numerous through holes of such a honeycomb structure, and is preferably coated with alumina sol obtained by hydrolyzing aluminum alcoholate or aluminum chelate and fired. Alternatively, it can be appropriately formed by adhering, pressing, and firing ultrafine powder of ceramic raw material. In addition, in the gas separation membrane structure of the present invention,
It is preferable from the viewpoint of separation efficiency that the entire fluid passage side of the partition wall is provided with a gas separation membrane part, but if necessary, a part of the base material part may be sealed with an adhesive or
A thin film having other functions may be formed on a portion of the base material portion. [Operations and Effects of the Invention] In the gas separation membrane structure according to the present invention, the gas separation membrane portion is located on substantially the entire fluid passage side of the base material portion constituting the partition wall, and the gas separation membrane portion in the base material portion The diffusion resistance is defined within a specific range that is extremely smaller than the gas diffusion resistance of the gas separation membrane. Therefore, substantially all of the fluid passage side of the partition wall has a selective permeation effect, and the selectively permeated specific gas component diffuses within the base material part as a second fluid passage, and passes through the gas discharge part to the structure. It is excreted from the body. Therefore, in the gas separation membrane structure, the selective permeation area per unit volume is significantly increased, and the gas separation efficiency is significantly improved compared to the conventional one, and when the same efficiency is constant, the structure can be made smaller. be able to. In addition, in this gas separation membrane structure, since all the fluid passages are used as flow passages for the gas to be treated, it is necessary to specify that all the fluid passages are selectively permeable as the flow passages for the gas to be treated, as in the past. In order to configure two types of gas component flow passages, the open ends of a large number of identified fluid passages on one end side of the structure and the open ends of a large number of other identified fluid passages on the other end side are sealed. There is no need for the troublesome work of doing so. Therefore, the gas separation membrane structure can be easily manufactured. [Example] (1) Gas separation membrane structure FIG. 1 shows a first gas separation membrane structure 10A (hereinafter referred to as the first structure) according to the present invention. The structure 10A is a ceramic honeycomb structure in the shape of a square prism, and is surrounded by continuous partition walls 11 and includes a large number of parallel fluid passages 12 having a square cross section. As shown in FIG. 2, the partition wall 11 is composed of a base material portion 11a and a gas separation membrane portion 11b. The separation membrane portion 11b is integrally located on all surfaces of the base portion 11a on the fluid passage 12 side, and constitutes a peripheral wall of the fluid passage 12. The structure 10A is used housed in a casing 21 as shown in FIG. Left and right support 22 in 21,
The entire outer surface between the supports 22 and 23 is coated with glaze and sealed, and the separation membrane portion 11b is exposed on the outer surface on the end side of each support 22, 23. Note that the discharge pipe 13 protrudes from the casing 21 to the outside, and the exposed portions of the partition wall 11 at both ends of the structure 10A are sealed with adhesive. The gas to be treated is supplied from the inlet port 21a of the casing 21 to the structure 10.
A flows into each fluid passage 12 from one end of A, flows through the same passage 12, and flows out from the other end of the casing 21.
It is discharged through the outlet port 21b. During this time, a specific gas component in the gas to be treated is concentrated and passes through the separation membrane part 11b of the partition wall 11, and diffuses in the base material part 11a while passing through the discharge pipe 1.
It is discharged after 3 steps. Note that in the structure 10A, a plurality of discharge pipes 13 or pipes functioning similarly to the discharge pipe 13 may be provided. FIG. 3 shows a second gas separation membrane structure 10B according to the present invention. The structure 10B has the same external shape as the first structure 10A, and is used while being housed in a casing 24 as shown in the figure. A base material portion 1 is provided on the outer surface 11c between the supports 22 and 23 in the structure 10B.
1a is exposed, and a separation membrane portion 11b is exposed on the outer surface on the end side of both supports 22 and 23. The gas to be treated flows into each fluid passage 12 through the inlet port 24a and is discharged through the outlet port 24b. During this time, a specific gas component in the gas to be treated is concentrated and passes through the separation membrane section 11b, diffuses through the base section 11a, passes through the outer surface 11c between the supports 22 and 23, and passes through the second outlet. It is discharged from port 24c. Therefore, this outer surface 11c functions as a discharge portion. FIG. 4 shows a third gas separation membrane structure 10C according to the present invention. The structure 10C also has the same external shape as the first structure 10A, but a discharge hole 14 is bored in its outer surface instead of the discharge pipe 13. The discharge hole 14 has a rectangular cross section, and as shown in FIG.
It is open on one side of the outer surface of C and extends to a predetermined depth. In the discharge hole 14, the base portion 11a is exposed, and specific gas components are concentrated and permeate the separation membrane portion 11b, diffuse through the base portion 11a, reach the discharge hole 14, and pass through the casing 24. is discharged through the second outlet port 24c. In each of the above structures, the thickness of the base material portion 11a is 0.15 to 1.5 mm, and the average pore diameter is 0.2 to 5 μm.
, and the thickness of the separation membrane portion 11b is 2~
100μm, average pore diameter less than 1000Å. If the average pore diameter of the base material portion 11a is less than 0.2 μm, the diffusion resistance of the base material portion 11a cannot be ignored, and if the average pore diameter exceeds 5 μm, it becomes difficult to form the separation membrane portion 11b made of uniform fine particles. Become.
Further, the amount of pure nitrogen that permeates through the base material portion 11a, which will be described later, is 20 times or more the same amount of permeation through the partition wall 11. In addition,
The partition wall 11 of each of the structures described above is a two-layer structure consisting of a base material part 11a and a separation membrane part 11b. may be integrally interposed. In these cases, it is preferable that the average pore diameter of the base material part 11a is 2 to 5 μm, and the average pore diameter of the sub-base material part is 0.2 to 2 μm. A dense and thin separation membrane portion 11b can be easily formed, and the latter partition wall has a function of protecting the separation membrane portion 11b from dust in the gas to be processed. Note that the structures shown in FIGS. 1 to 5 are only examples of the gas separation membrane structure of the present invention, and these structures do not necessarily need to be housed in a casing. The desired separation performance can be obtained even if the structure 10A provided with the structure 10A is installed in a predetermined space filled with the gas to be processed. Also, whether the outer surface of each structure is the gas separation membrane portion 11b or the base material portion 11a,
Alternatively, whether to seal with glaze, adhesive, etc. is selected as appropriate depending on the operational state of the structure. Further, the exposed portions of the partition wall 11 at both ends of the structure can be sealed with an adhesive or a gas separation membrane can be attached thereto. Furthermore, by using the exposed parts of the partition wall 11 at both ends of the structure as the base material part 11a, it can be used as a gas discharge part, and in this case, it is necessary to plug at least one end of the fluid passage 12. (2) Method for preparing the base material portion 11a The base material portion 11a constituting the partition wall 11 is prepared using the methods (a) to (e) below.
Each was prepared using the following method. (a): To a mixture of 90 parts of α-Al ₂ O ₃ particles with an average particle size of 0.8 μm and 10 parts of kaolin, water and polyvinyl alcohol as an organic binder are added and kneaded. The obtained clay is extruded, dried, and then fired in the atmosphere at 1350°C for 3 hours. The average pore diameter of the obtained molded body (base material part) was 0.2 μm,
The pore volume is 0.1 cc/g. (b): A base material part was obtained by the preparation method (a) except that α-Al ₂ O ₃ particles with an average particle size of 1.5 μm were used. The average pore diameter of the obtained base material portion was 0.7 μm, and the pore volume was 0.19 cc/g. (c): Using α-Al ₂ O ₃ particles with an average particle diameter of 5 μm, a base material portion with an average pore diameter of 2.0 μm and a pore volume of 0.23 cc/g was obtained in the same manner as in the preparation method (b). (d): Using α-Al ₂ O ₃ particles with an average particle size of 12 μm,
A base material portion having an average pore diameter of 5.0 μm and a pore volume of 0.25 cc/g was obtained in the same manner as in the preparation method (c). (e): Preparation method (a) except that the firing temperature was 1500℃
A base material part was obtained. The average pore diameter of the obtained base material portion was 0.1 μm, and the pore volume was 0.07 cc/g. (3) Method for preparing the separation membrane part 11b The separation membrane part 11b constituting the partition wall 11 is prepared in the following (a) to
Each was prepared by the method (e). (a): Aluminum isopropoxide is heated and hydrolyzed, and nitric acid, which is a deflocculant, is added thereto to prepare a sol-supported solution. This sol-supported liquid was coated and supported on the surface of many through-holes in the base material portion, dried, and then baked at 400° C. for 3 hours in the atmosphere.
The average pore diameter of the obtained thin membrane (separation membrane part) is 50
Å, film thickness is 15 μm. (b): The thin film obtained in preparation method (a) was heated with sodium silicate for 3 hours to obtain a separation membrane with an average pore diameter of 30 Å and a film thickness of 15 μm. (C): Prepare a supporting slurry by adding water, nitric acid, and polyvinyl alcohol to α-Al ₂ O ₃ particles with an average particle size of 0.5 μm, and coat and support the slurry on the circumferential surface of the through hole in the base material. 1300℃ in the air after drying
After firing for 3 hours, the average pore size of the base material was 0.2μ.
A sub-base material portion with a film thickness of 50 μm was formed. Next, a separation membrane part with an average pore diameter of 50 Å and a film thickness of 15 μm was formed on this sub-substrate part by the preparation method (a) (three-layer structure). (d): r-Al with a specific surface area of 80 m ² /g. ₂ O ₃ powder to water,
A supporting slurry was prepared by adding nitric acid, and this slurry was coated and supported on the circumferential surface of the through hole of the base material portion, dried, and then baked at 800° C. for 3 hours in the atmosphere. The average pore diameter of the obtained separation membrane portion was 100 Å, and the membrane thickness was 50 μm. (E): Prepare a supporting slurry by adding water and nitric acid to commercially available zirconium hydroxide, coat and support the slurry on the circumferential surface of the through hole in the base material, dry, and sinter at 400°C in the atmosphere for 3 hours. Average pore size 250
A separation membrane portion with a film thickness of 80 μm was obtained. According to the preparation methods (a) to (e) above, the membrane forming component made of substantially uniform particles is deposited on the base material part 11a and fired, thereby forming a separation membrane part made of uniform pores. 11b is obtained. (3) _N2 permeation amount Based on base material preparation methods (a) to (e), outer diameter 10 mm, wall thickness 1
Sample S ₁ for base material part measurement in the shape of a bottomed pipe with a length of 150 mm and a sample for partition wall measurement equipped with a separation membrane part based on separation membrane part preparation methods (a) to (e) using the same sample. S ₂ was prepared. Each of the measurement samples S ₁ and S ₂ was subjected to the measurement method shown in FIG. 6, and the amount of N ₂ permeation was measured by the underwater displacement method.
In addition, for measurement, each measurement sample S ₁ , S ₂ is housed in an airtight container 31, and the connecting tube 32 is connected to each sample S ₁ , S _{2 .}
Connect hermetically to the open end of the As a result, N ₂ gas adjusted to a predetermined pressure is supplied from the cylinder ₃₃ into _the inner holes of each sample _{S 1 and} S ₂ ; , the same N ₂ gas passes through each sample S ₁ and S ₂ and flows out through the discharge pipe 34 connected to the container 31. The supply pressure of _N2 gas (pressure difference inside and outside the sample) is as follows for sample _S1 for base material measurement.
0.2~0.5 atm, 1~ for bulkhead measurement sample _S2
3atm, _N2 permeation amount Qmol/ ^m2・
hr・atm is calculated. Q=V/(A・△P) However, V: _N2 permeation amount (mol/hr) A: Permeable membrane area of each sample ( ^m2 ) △P: Pressure difference between inside and outside of _N2 gas (atm) ( 4) Dehumidification Experiment In order to remove moisture from the air, a dehumidification experiment was conducted using the first structure 10A to the third structure 10C shown in the drawings. The preparation method and characteristics of each structure are shown in Table 1, the results are shown in Table 2, and the shape, structure, and experimental conditions of each structure are as follows. Each structure is a honeycomb structure with a length of 81 mm, a width of 81 mm, and a length of 150 mm, and each fluid passage 12 has a uniform diameter of 3.5 mm.
The thickness of a is 1 mm, and a separation membrane part 11b having a predetermined thickness is formed on the base material part 11a. The volume of the structure is 984 cm ² and the separation area is 6840 cm ² . Each structure is used by being housed in stainless steel casings 21 and 24 with an outer diameter of 120 mm and a length of 200 mm.
Of each structure, the first structure 10A type uses a discharge pipe 13 with an inner diameter of 20 mm, and the second structure
In the structure 10B type, the outer surface 11c that functions as a discharge part is formed over a length of 130 mm, and in the third structure 10C type, the discharge hole 14 is 13.5 mm long, 50 mm wide, and deep. It is formed to a size of 45mm. Air at a temperature of 25° C. and a relative humidity of 70% was used in the dehumidification experiment, and the air was flowed into each structure at a flow rate of 6 m ² /hr. Note that the pressure on the discharge pipe 13 and second outlet port 24c side was reduced to 5 to 10 torr. As a comparative example, a dehumidification experiment was conducted using the following two types of pipe bundle type structures 10D and 10E, with the air to be treated flowing in perpendicularly to the outer periphery of the structures. Structure 10D has a pipe body with a length of 150 mm, which has a separation membrane part on the outer periphery of a pipe-shaped base material part, with an interval of 20 mm.
Arranged in a square array of 144 and bundled inside the casing, the volume of the structure was 8640 cm ² and the area of the separation membrane was
6782 cm ² (same membrane area). The structure 10E consists of 16 pipes arranged in the same way and bundled inside the casing, and the volume of the structure is 960 cm ² and the area of the separation membrane is
It was set to ^754cm2 . (Same volume).

【table】

[Table] (5) Discussion Referring to Table 2, the structure according to the present invention (No.
1 to No. 10), the dehumidifying performance is high, and the ratio of N ₂ permeation amount of the base material portion to the partition wall is particularly high when it is 20 or more (see No. 11). Furthermore, when the ratio of _N2 permeation amount is 50 or more, the outlet relative humidity is low and the amount of dehumidification is large;
Efficient dehumidification is performed (see especially No. 4 and No. 5).
The average pore diameter of the base material part 11a is preferably 0.2 to 5 μm, and when the average pore diameter is as large as 5 μm, it is possible to form a sub-base material part and form a separation membrane part on the same base material part. This is preferred in terms of membrane performance and separation efficiency (see No. 5). The _N2 permeation amount of the base material part 11a is 1000~
A value of 9500 mol/m ² ·hr·atm is suitable. In addition, the amount of N ₂ permeation through the partition wall 11 having dehumidifying performance is 5
The value is ~250mol/ ^m2・hr・atm,
A value of 100 mol/m ² ·hr · atm or less is suitable because the amount of air leakage is small. In the structure according to the present invention, the water permeation rate per separation membrane area is almost the same as that of the pipe bundle type (Nos. 12 and 13), and the inside of the base portion 11a functions as a water flow path. That is clear. In order to obtain the same performance as the structure according to the present invention, the pipe bundle type (No. 12) requires about 9 times the volume, and if the volumes of both are made approximately the same, the pipe bundle type (No.13)
has almost no dehumidification performance. Membrane structure 1
Regarding 0A to 10C, membrane structure 1 with superior dehumidification performance
0C is suitable (see No. 3, No. 9, No. 10). In the present invention, it has been confirmed that H ₂ can be selectively separated from a H ₂ -N ₂ mixed gas using the structure No. 3, and that it is sufficiently effective. Similarly, it is possible to selectively separate H ₂ O from a H ₂ O-EtOH mixed gas, and even if the H ₂ O-EtOH system is supplied in liquid form, H ₂ O can be selectively separated (pervaporation). We have also confirmed that this is possible.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a first gas separation membrane structure according to the present invention, FIG. 2 is a partially enlarged sectional view of the same structure, and FIG. 3 is a perspective view of a second gas separation membrane structure according to the present invention. , FIG. 4 is a perspective view of a third gas separation membrane structure according to the present invention, and FIG. 5 is a partially enlarged sectional view of the same structure.
FIG. 6 is an explanatory diagram of a method for measuring the amount of N ₂ permeation. Explanation of symbols, 10A, 10B, 10C... Gas separation membrane structure, 11... Partition wall, 11a... Base material part, 11b... Separation membrane part, 12... Fluid passage, 2
1,24...Casing.

Claims (1)

[Scope of Claims] 1. A fluid passageway including a large number of parallel fluid passages surrounded by partition walls, and wherein the partition walls are located in substantially all of the porous base material portion and the fluid passage side, A gas separation membrane structure comprising a gas separation membrane unit integral with a gas separation membrane unit, wherein the amount of pure nitrogen permeation through the base portion is 20 times or more that of the amount of pure nitrogen permeation through the partition wall, and The average pore diameter is 1000 Å or less, and as the fluid to be treated flows through the fluid passage, specific gas components in the fluid to be treated are concentrated and permeate through the gas separation membrane section and diffused in the base material section. A gas separation membrane structure characterized in that the gas is discharged to the outside of the structure through a gas discharge part of the base material part. 2. The gas separation membrane structure according to claim 1, wherein the amount of pure nitrogen permeated through the base portion is 50 times or more the amount of pure nitrogen permeated through the partition wall. 3 The amount of pure nitrogen permeation through the partition wall is 100 mol/m ² .
The gas separation membrane structure according to claim 1 or 2, wherein the gas separation membrane structure has a gas separation temperature of hr.atm or less. 4. The gas separation membrane structure according to claim 1, 2, or 3, wherein the gas discharge portion is provided on a side surface of an outer wall. 5. The gas separation membrane structure according to claim 1, 2 or 3, wherein the gas discharge part is provided at one end of the outer wall. 6. The gas separation membrane structure according to claim 4 or 5, wherein the gas discharge portion extends inward from the outer wall. 7. The gas separation membrane structure according to claim 1, 2, 3, 4, 5, or 6, wherein the partition wall is made of ceramic.