JPH1190193A - Separation membrane module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a module whose gas passing area is increased and whose manufacturing cost is sharply decreased in separation membrane modules for separating specified gas. SOLUTION: In a separation membrane module that a metallic film 15 selectively permeating specified gas and a base plate 11 having a gas catching part are integrated, the base plate 11 has its surface cut or ground after precision casting, and preferably by cutting or grinding the surface of the base plate surface 11 after precision casting, the flatness and the face roughness Ra are made <=0.3 mm and <=10 μm respectively. In this way, both a gas introducing pipe and a gas withdrawing pipe can be cast at the same time, and machining of both sides is made easy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas separation membrane module, and more particularly, to a gas separation membrane module used in a specific gas producing apparatus, a recovering apparatus, a purifying apparatus or the like.

[0002]

2. Description of the Related Art As a means for producing, separating, recovering or purifying a gas, there is a method using a metal or alloy film (hereinafter sometimes abbreviated as "metal film") which selectively transmits a specific gas. Industrially, it has been put to practical use in the production of ultrahigh-purity hydrogen in the semiconductor production field, and its application to the production of ammonia in the petrochemical industry is also advancing. Regarding the phenomenon in which the metal film permeates only the specific gas, when a mixed gas containing the specific gas is brought into contact with one surface of the metal film, the specific gas molecules are absorbed by the metal film, become an atomic state, and further ionized. And diffuses to the opposite side of the metal film, where it recombines and becomes a specific gas molecule again. By utilizing this phenomenon, a specific gas is collected on the opposite side of the metal film. As a method for producing a metal film, a metal or an alloy having a specific gas selective permeability is annealed and cold-rolled, and a surface of a porous body serving as a support of the metal film is plated by electroplating, electroless plating, or the like. Or a method of forming a metal film by a vapor deposition operation such as vacuum deposition by electron beam heating.

In industrial applications, the metal film (foil) formed by the above-described means is placed on the side of the mixed gas containing the specific gas of interest with the metal film (foil) facing the outside, and the mixed gas contact surface of the metal film is contacted. On the opposite side, a separation membrane module provided with a base portion having a space for collecting the permeating specific gas is configured. As the pressure difference between the two sides of the metal film, that is, the pressure difference between the mixed gas and the permeated specific gas is larger, the amount of the specific gas permeating through the metal film increases, but the metal film can withstand this pressure difference. In addition, reinforcing means is required. Therefore, between the metal film and the base portion, a porous body or a reinforcing plate made of a porous body is usually provided to support the metal film and reinforce the film strength. However, since the gas flow path is narrowed by the reinforcement, the pressure loss increases, so a reinforcing plate that can maintain a large pressure difference and secure the flow path of the specific gas is desired. A separation membrane having a structure in which a reinforcing plate combined with a wire mesh and a metal foil are joined (Japanese Patent Application No. 5-203250), or a separation membrane in which a metal membrane is stacked on a metal porous support provided with a large number of through holes ( (Japanese Patent Application No. 5-76738). The shape of the separation membrane module includes a flat plate shape and a cylindrical shape according to the shape of the base portion.

[0004]

FIG. 4 is a view for explaining a specific example of a separation membrane module proposed by the applicant of the present invention in Japanese Patent Application No. 8-60883, and shows a reinforcing plate having a large number of openings. By stacking a plurality of 15 ', the strength of the metal film 15 is increased comprehensively, and the reinforcing plates 15' are arranged so that the long axes of the substantially rectangular openings are orthogonal to each other. In order to manufacture this separation membrane module, for example, a metal film 15 such as a hydrogen selective permeable foil made of a Pd-Ag alloy manufactured by cold rolling and a plurality (three in the illustrated example) of reinforcing plates 15 ′ are provided. A base plate 11 made of metal or alloy having a groove 12 for collecting a specific gas collected through the metal film 15 and the reinforcing plate 15 'is disposed in a partially cutaway perspective view of FIG. As described above, the outer circumferences of the metal film 15, the reinforcing plate 15 'and the base plate 11 are joined by brazing, diffusion bonding, seal welding, or the like, thereby integrating the whole. Reference numeral 16 denotes a joint. Further, a gas extraction pipe 14 which is connected to the groove 12 is attached to the base plate 11 so that a target specific gas can be extracted. In some cases, a sweep gas introduction pipe 17 is also provided so that the sweep gas can flow in and be extracted from the gas extraction pipe 14 together with the permeated specific gas (purified gas).

Conventionally, the base plate 11 is made of a metal or alloy plate such as a stainless steel plate, and its surface is grooved by chemical etching or machining. The gas extraction pipe 14, the sweep gas introduction pipe 17, etc.
Is formed and separately attached by welding. As described above, the production of the base plate 11 is costly and time-consuming, and the production of the separation membrane module is expensive in combination with the production costs of the metal film 15 and the reinforcing plate 15 '. In addition, according to the chemical etching, the etching in the depth direction of the groove 12 is about 1/2 of the groove width, and there is a limit in forming the gas flow path by making the groove deep, and the pressure loss must be reduced. Was difficult. In view of such a current situation, an object of the present invention is to provide a separation membrane module having a structure that can be manufactured at a lower cost than in the past and can form a large gas flow path.

[0006]

As a means for solving the above-mentioned problems, the present invention provides (1) a separation method in which a metal film selectively permeating a specific gas and a base plate having a gas trapping portion are integrated. In the membrane module, the base plate is obtained by cutting or grinding the surface after precision casting, (2) the surface of the base plate has a flatness of 0.3 mm or less; And surface roughness Ra: 10
The separation membrane module according to the above (1), which is not more than μm, (3) gas trapping parts are formed on both surfaces of the base plate, and the metal membranes are respectively arranged outside the gas trapping parts. (1) The separation membrane module according to (1) or (2), wherein the base plate and the gas extraction tube or the base plate and the gas extraction tube and the sweep gas introduction tube are integrally formed by precision casting. The separation membrane module according to any one of the above (1) to (3), which is formed by casting, and (5) the metal membrane is integrated with the base plate via a reinforcing means. A separation membrane module according to any one of the above (1) to (4), characterized by comprising:

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to solve the above problems, the present inventors have studied the use of a low-cost casting method instead of the etching method as a means for producing a base plate.
Conventionally, casting has poor dimensional accuracy and surface smoothness (flatness, surface roughness), and has not been adopted for this type of base plate application. However, if a practical base plate can be manufactured by casting, not only the above cost, but also the degree of freedom in the shape of the groove processing will be greater than by the etching method, and a sweep gas introduction pipe and a gas extraction pipe can be formed at the same time Further, there are many advantages such as that grooves can be formed on both sides of the base plate at the same time. In the present invention, as a casting method, a method generally referred to as a precision casting method for obtaining a casting having a high dimensional accuracy and a good casting surface using a precise mold is employed. According to the precision casting method, generally, almost no machining is required after casting, and it is said that the casting method is suitable for a thin object or a casting having a complicated structure. In the present invention, the periphery of the base plate and the metal film (including the reinforcing plate) are welded and sealed. Laser welding, TIG welding (Tu
ngsten Inert-Gas arc welding) is used. The reason for employing laser welding and TIG welding is that since only a minute area can be heated and welded, heat input is small and damage to the metal film can be reduced.

FIG. 1 is a schematic explanatory view of a specific example of a base plate of the present invention. FIG. 1 (a) is a plan view of a precision-cast base plate, and FIG. 1 (b) is AA of FIG. FIG. 3C is a cross-sectional view taken along line BB of FIG.
Represents a groove acting as a gas trapping portion, and 4 represents a gas extraction tube. In this example, grooves 2 are formed on both sides of the base plate 1, and each groove 2 is connected to the groove 3 at both ends. Also, groove 2
In the cross section, the groove width and the groove depth are formed to have substantially the same length, and the gas extraction pipe 4 is cast integrally with the base plate 1. A bonded body 5 of a metal film (alloy foil) having specific gas selective permeability and a reinforcing plate is attached to both surfaces of the base plate 1 thus precision-cast by seal welding 6 as shown in FIG. It is a membrane module.

However, gas leakage occurred even when the base plate 1 and the metal film-reinforced plate assembly 5 were sealed and welded by the precision casting method. As a result of extensive studies by the present inventors,
As shown in FIG. 3A, the metal film-reinforced plate assembly 5 and the base plate 1 can be completely in close contact with each other, that is, the gap 2
When 0 is 0 mm, or when the gap 20 between the metal film-reinforcement plate assembly 5 and the base plate 1 shown in (b) of the figure is small (for example, 0.1 mm), the metal film-reinforcement plate joint is performed. The body 5 and the base plate 1 are completely connected and joined by the weld bead 21, but as shown in FIG.
It has been found that there is a portion where the weld bead 21 is separated at a position where 0 is large, and that if the gap 20 is set to 0.02 mm or less, seal welding can be performed without separation of the weld bead 21. Then, the present inventors set the above gap 0.02.
In order to obtain the dimensional accuracy of not more than mm, the inventors of the present invention conceived to further cut or grind the contact surface of the precision-cast base plate with the metal film (or the metal film-reinforced plate assembly), and completed the present invention.

[0010] The method of the present invention will be described more specifically.
As the precision casting of the present invention, for example, lost wax method,
Investment method, mold casting method, graphite casting method, show method, gypsum mold method, die casting method and the like,
Particularly preferred is the lost wax method, because a product having a complicated shape can be manufactured with relatively good dimensional accuracy.

The contact surface of the precision-cast base plate with the metal film (metal film-reinforced plate assembly) is cut or ground. In order to obtain the dimensional accuracy of the gap of 0.02 mm or less, the flatness must be 0.3 mm or less and the surface roughness Ra
= 10 μm or less was confirmed by experiments described later.

Here, the flatness in the present invention means JI
It is defined in SB0621 and refers to the magnitude of deviation of a planar feature from a geometrically correct plane (geometric plane). The flatness is expressed by the distance between two planes (unit: mm) when the plane form (P) is sandwiched by two geometric parallel planes and the distance between the parallel planes is minimized.
Or μm). That is, the flatness of the present invention is 0.3 m
The planes below m must be within a plane tolerance zone of 0.3 mm (area sandwiched between two parallel planes separated by 0.3 mm). Specifically, the contact surface of the present invention is used as a measurement surface, and is scanned vertically and horizontally in a mesh pattern with a stylus, and the vertical movement range is represented by two planes. Note that the tolerance refers to an allowable value of the geometric deviation. In order to reduce the flatness to 0.3 mm or less, for example, a lathe or a grinding machine having a good flatness is ground or polished to a flatness of x mm or more by (x-0.3) mm or more.

The surface roughness referred to in the present invention is JIS B
Surface roughness based on 0601 and refers to center line average roughness (Ra). For example, in the stylus method, a fine needle is scanned while pressing it against the object, and a roughness curve y = f (x) is obtained from its vertical movement (Y-axis direction), and the center line of this roughness curve (X-axis) A specific measurement length portion (L) is extracted in the direction, and a value calculated by the formula of Expression 1 is displayed in μm.

(Equation 1)

A metal film (metal film-reinforced plate joint) portion is attached to the base plate obtained above by seal welding.
As a seal welding method, gas laser welding of CO ₂ , YAG or the like, TIG welding, or the like can be applied.

In the present invention, the metal film is not particularly limited as long as it is a metal film (foil) that allows a specific gas to pass therethrough, but examples of the type of metal include Pd or a Pd alloy. Pd alloys include Y and other rare earth elements, Group 11 elements such as Ag, Au and Cu, Pt, Ni
Group 10 elements such as Rh, Co, etc .;
Preferable alloys include one or more selected from the group consisting of Group 8 elements such as Fe, Group 6 elements such as Mo, and Group 5 elements such as V, and Pd. There is no particular limitation on the method of producing the metal film itself, and examples thereof include a method of rolling a metal plate, a method of forming a film on a surface of a substrate by plating, thermal spraying, vapor deposition, and the like, and then removing the substrate. Can be

In the present invention, the material and structure of the reinforcing plate are not particularly limited as long as the reinforcing plate has a portion that can be seal-welded to the base plate. Specifically, it is desirable that the material is made of a weldable metal or alloy,
A porous structure (but may have a non-porous frame on the outer periphery) so that the specific gas of interest permeates, for example, a hole processed by laser method, etching method, drill method, etc. , A network structure, a metal nonwoven fabric and the like.

[0017]

【Example】

EXAMPLE A base plate 1 having the structure shown in FIG. 1 was manufactured by a precision casting method. In the precision casting, the gas extraction tube 4 was also integrally cast by the lost wax method. The channel cross-sectional area of the groove 2 is set in consideration of the pressure loss of hydrogen permeating the hydrogen selectively permeable alloy. In consideration of grinding the surface in post-processing, the depth of the groove 2 is set to a value smaller than the design value. About 1.0 mm was saved. That is, it was manufactured to have a groove width of 1.5 mm, a groove pitch of 3 mm, and a groove depth of 2.5 mm. The flatness of the base plate 1 immediately after precision casting was about 0.5 to 1.0 mm. This was ground on both sides max1.0 mm, and the conditions at this time were variously changed to produce the surface roughness and flatness shown in No. 1 to No. 9 in Table 1. Using each base plate, a flat hydrogen separation membrane module shown in FIG. 2 was produced in the following manner. First, a hydrogen-permselective alloy foil as a metal film and a reinforcing plate were diffusion-bonded using silver braze to prepare a metal film-reinforced plate assembly 5. Next, the metal membrane-reinforcement plate assembly 5 was set on both surfaces of the base plate 1 with a jig, and sealed and welded with a CO ₂ laser welding machine to obtain a separation membrane module (hydrogen separation membrane module) shown in FIG.

For each of the obtained modules, the presence or absence of a leak at the seal welding portion was examined as follows. The gas extraction pipe is connected to an Ar gas cylinder via a pressure gauge and a bubble via a pipe. First, the bubble is opened and an internal pressure of 2 kgf / cm ² G is applied to the metal membrane module. The pressure change is checked with the above pressure gauge. If the pressure did not decrease even after several minutes, it was determined that there was no leak. The results are summarized in Table 1. In the column of seal welding results, ○ indicates no leak among three of the prototypes, and Δ indicates 1
Or, there are two leaks, and x indicates that all three leak. From the results in Table 1, it can be seen that good results were obtained in the range of the present invention where the flatness of No. 6, 8 and 9 was 0.2 mm or less and the surface roughness Ra was 10 μm or less. Thus, the hydrogen separation membrane module according to the present invention has no leak,
It was usable enough. Further, the gas flow path can have a large cross-sectional area and can be formed on both sides of the base plate by a single process, so that it is an efficient separation membrane module. The manufacturing cost according to the present invention is one-fifth that of the conventional chemical etching, and a significant reduction in manufacturing cost has been realized.

[0019]

[Table 1]

[0020]

As described above, in the separation membrane module of the present invention, the flatness and surface roughness can be improved by forming the base plate by precision casting and then cutting or grinding the base plate. No leakage after welding,
An inexpensive base plate can be supplied. In addition, the manufacturing cost was greatly reduced in that the double-sided groove processing and the formation of the gas extraction pipe and the sweep gas introduction pipe were possible by a single casting. As compared with the case of the conventional etching, the inventors of the present invention have achieved a cost of 1/5 according to the method of the present invention.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating the structure of a base plate of the present invention.

FIG. 2 is a partial perspective view of one embodiment of the present invention.

FIG. 3 is a diagram illustrating the present invention.

FIG. 4 is a perspective view illustrating the structure of a metal film module.

FIG. 5 is a partially cutaway perspective view illustrating the structure of a metal film module.

Claims (5)

[Claims] A metal film that selectively permeates a specific gas;
A separation membrane module in which a base plate having a gas trapping portion is integrated, wherein the base plate is subjected to precision casting and the surface thereof is cut or ground. 2. The surface of the base plate has a flatness of 0.3 m.
2. The separation membrane module according to claim 1, wherein the surface roughness Ra is 10 μm or less. 3. The separation according to claim 1, wherein gas trapping portions are formed on both sides of the base plate, and the metal films are respectively arranged outside the gas trapping portions. Membrane module. 4. The gas injection pipe according to claim 1, wherein the base plate and the gas extraction pipe or the base plate, the gas extraction pipe and the sweep gas introduction pipe are integrally molded by precision casting. 4. The separation membrane module according to item 1. 5. The separation membrane module according to claim 1, wherein the metal membrane is integrated with the base plate via a reinforcing means.