JPS62128903A - Ultrahigh-purity hydrogen permeable cell - Google Patents

Abstract

PURPOSE:To produce ultrahigh-purity gaseous hydrogen by using the titled cell contg. plural Pd-alloy thin tubes wherein a coil spring without any cracks on its surface is inserted as the permeable membrane. CONSTITUTION:Plural Pd-alloy thin tubes 6 wherein the coil spring 5 is inserted are housed in the cylindrical hydrogen permeable cell 4, and the opening ends of the tubes are fixed to a tube plate 7. Stainless steel, Co-Ni-Cr steel, etc., are selectively used as the material of the coil spring 5, and the coil spring without any cracks on its surface is used. Consequently, water, air, etc., penetrated into the cracks are never leaked and mixed into the purified gas when the gas is purified, and the gaseous hydrogen can be purified to >=99.9999% purity.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an ultra-high purity hydrogen permeation cell, and more particularly to an ultra-high purity hydrogen permeation cell using a palladium alloy capillary in which a crack-free coil spring is inserted. Regarding.

The demand for hydrogen gas in the semiconductor industry and the like is rapidly increasing, and as the technology in these fields becomes more sophisticated, the gas used is also required to have extremely high purity.

[Conventional technology]

It is known that palladium and palladium alloys selectively permeate only hydrogen gas, and hydrogen purification equipment using palladium alloy permeable membranes is used to utilize this property to obtain high-purity hydrogen. Such a hydrogen purification apparatus is comprised of, for example, a palladium alloy hydrogen permeation cell, a gas cooler, piping, fittings, valves, and the like. A hydrogen permeation cell usually has a plurality of palladium alloy thin tubes with one end sealed and the open end fixed to a tube plate and housed inside the cell, and the inside of the cell is partitioned into two spaces by the palladium alloy and the tube. The outside of the palladium alloy thin tube is the primary side, and the inside is the secondary side. A spring is inserted inside the palladium alloy thin tube to withstand the pressure difference between the primary side and the secondary side and to maintain a flow path space for permeated hydrogen.

When refining hydrogen gas, the hydrogen permeation cell is heated to 300-500℃.
The raw material gas is supplied under pressure to the primary side of the cell while being heated to
- The purified gas is selectively permeated from the inside (secondary side) to the inside (secondary side) and reaches the purified gas outlet of the cell via the flow path space of the coil spring and the secondary side space of the cell.

The palladium alloy tube uses a highly purified palladium alloy membrane that has been thoroughly degassed, and has a helium leak test rating of IX 10-'' atm/cc se.
It is said that a product that passed the criteria c was obtained, and there was no leakage of impurities at all, and the purity of the hydrogen gas at the time of permeation was substantially 100%.

[Problem that the invention seeks to solve]

However, even if a hydrogen permeation cell using such a palladium alloy thin tube is used in a purification device, the purity decreases at the cell outlet, and even if the purification is continued for a long time, the purity will be 9! It 999
The limit is ~99.9999%, and there is a problem that it is impossible to obtain purified hydrogen gas with a purity higher than this, and it is not possible to cope with the advancement of technology such as the production of submicron-level semiconductors.

The present invention investigates the cause of purity reduction in conventional hydrogen permeation cells and improves the purity to 99.99%.
The object of the present invention is to obtain a hydrogen permeation cell for ultra-high purity hydrogen gas of 999% or more.

[Means for solving problems]

The inventors of the present invention continued intensive research to obtain ultra-high purity hydrogen from a hydrogen permeation cell using palladium alloy tubes, and found that the coil spring inserted into the palladium alloy tube had many fine racks. The present invention was achieved based on the discovery that the purity of purified hydrogen gas is greatly affected.

That is, the present invention provides an ultra-high purity hydrogen permeation cell whose permeation membrane is a plurality of palladium alloy thin tubes each having a coil spring inserted therein, wherein the ultra-high purity hydrogen permeation cell is characterized in that there are no cracks on the surface of the coil spring. It is a transmission cell.

The hydrogen permeation cell of the present invention is constructed as shown in the schematic longitudinal cross-sectional view shown in FIG. A plurality of palladium alloy thin tubes into which coil springs 5 are inserted 6. −． 6 are housed with their open ends fixed to the tube plate 7, and the palladium alloy thin tubes 6. The inside of the cell is partitioned into two spaces by palladium alloy thin tubes 6, 6 and tube plate 7.・・・
-16, the outside is the primary side, and the inside is the secondary side.

In the present invention, the material of the coil spring inserted into the palladium alloy thin tube has sufficient heat resistance to the operating temperature,
A material that does not react with the palladium alloy and has a sufficiently low internal gas component is selected.

The metal wire of the coil spring is stainless steel, C.

-Ni-Cr alloy, etc., and the diameter of the metal wire is 0.1~
The outer diameter of the coil is approximately 0.8 mmφ, and the outer diameter of the coil is slightly smaller than the inner diameter of the palladium alloy thin tube.
It is 8 to 2.8 mm.

The surface of a coil spring usually has various shapes of minute dents such as wear scars, cracks, and small holes.These are difficult to see with the naked eye, but can be observed in detail with magnified photographs taken with an electron microscope. can. However, it is not possible to image the inside of a deep dent, and this part is black.

In the present invention, a crack refers to a dent on the surface of a spring in which the area of the black part is 20 mm 2 or more in a 4500 times enlarged photograph taken with an electron microscope.

FIG. 1 is a 450 times enlarged photograph taken by an electron microscope of a coil spring with no cracks on the surface used in the present invention, and FIG. 2 is a 4500 times enlarged photograph. Although there are linear dents on the surface, they are all shallow and the depth of the dents has been illuminated, and there are no cracks.

Figure 3 shows a 45mm coil spring that has been used conventionally.
This is a 0x magnified photograph, and FIG. 4 is a 4500x magnified photograph. In Fig. 3, the cracks are shown in black and are scattered, but in Fig. 4, the area of the black part is 20 mm.
It is larger than 2 and is recognized as a crack. As is clear from FIG. 3, an extremely large number of racks exist in one field of view magnified 450 times as seen in FIG. 4. As shown in FIG. 1, there are almost no cracks on the surface of the coil spring used in the present invention in a 450x magnified field image. In this invention, a state in which no cracks are observed in the 450 times magnified field image is defined as a crack-free state.

If a coil spring with cracks on its surface is used in a hydrogen permeation cell, impure gases such as moisture and air that have penetrated into the cracks and remain will gradually leak out during gas purification.
High purity hydrogen gas cannot be obtained because it is mixed into purified hydrogen gas over a long period of time and reduces its purity.

There are no particular limitations on the method of obtaining the crack-free spring used in the present invention, but it can also be obtained, for example, as follows. Stainless steel or Co--N 1--Cr alloy, which has been sufficiently degassed by vacuum melting once or twice, is cold drawn, bright annealed, and then surface polished with a polishing cloth or the like.

Subsequently, the wire is cold-stretched to a predetermined thickness, heat-treated at 700 to 800°C, and optionally subjected to chemical polishing or other treatments to obtain a crack-free wire, which is then wound around a core wire and processed into a coil spring.

The palladium alloy thin tube into which the coil spring is inserted usually has an outer diameter of 1.0 to 3.0 mm and a thickness of about 30 to 200 .mu.m from the viewpoint of hydrogen permeation efficiency and mechanical strength. There are no particular restrictions on the material as long as it has high hydrogen permeability and good workability, but palladium, silver,
Alloys of gold, rhodium, ruthenium, etc. are preferred, such as alloys of palladium and 5 to 50% silver, alloys of palladium and 5 to 40% silver and 1 to 20% gold, and alloys of palladium and 5 to 40% silver and rhodium. 2-10
These alloys are made into thin tubes by conventional methods and used in hydrogen permeation cells.

〔Effect of the invention〕

By using the ultra-high purity hydrogen permeation cell of the present invention,
99.9999 where hydrogen gas could not be obtained conventionally
It is now possible to purify the material to a purity of 9% or higher, and is expected to make a significant contribution to the ultra-high integration of semiconductors.

〔Example〕

In the example, a spron (manufactured by Seiko Electronics Parts, Co-Ni-Cr alloy) from which the internal gas had been sufficiently removed by vacuum melting was cold drawn to a diameter of 0.8 mm, and the surface was brightly annealed and polished with an endless polishing cloth. Cracks on the wire surface were removed by polishing. Next, the wire was cold drawn to 0.3 mmφ, heat treated at 700°C in nitrogen gas, and then the wire drawn to 0.2 mmφ was wound around the core wire, resulting in an outer diameter of 1.3 mm.
The coil spring had a pitch of 0, 75 mm, and a length of 340 mm.

No cracks were observed on the surface of this coil spring, as shown in the enlarged photographs of FIGS. 1 and 2.

A hydrogen permeation cell was prepared by temporarily fixing 135 palladium alloy thin tubes each having an outer diameter of 1.6 mm, a thickness of 80 μm, and a length of 330 mm, each made of a coil spring without a rack, and then housed in a cell.

This hydrogen permeation cell is fed with raw water poisonous gas (hydrogen in cylinders).
Outlet pressure 3.5 kg/ciG, outlet pressure 0,03
kg/cnf G at 15001/hr,
Dew point measurements and nitrogen and oxygen analyzes were performed on the cell discharge log gas. As a result, as shown in Table 1, it was found that hydrogen gas with a purity of 99.99999% or higher was obtained. Paname for dew point measurement) IJ Book Model 70
Moisture was determined using Type 0 (Japan Paname L-1) manufactured by Tsuta Corporation), and analyzed using 02, N2, CO1Co2, methane bag gas chromatograph (TCD) and flame ion detector (PID), and these were subtracted from the total. The difference was defined as the purity of hydrogen gas.

Comparative Example 1 Instead of using a crack-free coil spring, the third
Hydrogen gas was purified under the same conditions as Example 1 using the same hydrogen permeation cell as in Example 1, except that a coil spring with various cracks on the surface was used as shown in the enlarged photograph in Figure 4 and Figure 4. Ta. The results are shown in Table 1, and the purity was lower than 99.9999%.

Table 1

[Brief explanation of drawings]

Figures 1 and 2 are enlarged photographs taken with an electron microscope of the surface of the coil spring used in the present invention, Figures 3 and 4 are enlarged photographs taken with an electron microscope of the surface of a conventional coil spring, and Figure 5 is an enlarged picture taken with an electron microscope of the surface of a coil spring used in the present invention. FIG. 2 is a schematic vertical cross-sectional view of a transmission cell. The numbers in the figure are as follows. 1. Entrance 2. Exit 3. Pliedro 4. Cell 5, coil spring 6. Palladium Alloy Thin Tube 7, Tube Sheet Patent Applicant Tadahiro Omi (and 2 others) Representative Patent Attorney Tadashi Kobori Bunkan Figure 1 Jin 30 Figure 2 Name Figure 4 Figure 5 Procedural Amendment (Method) % Formula % Display of the case 1985 Patent Application No. 264959 Name of the invention Person who corrects ultra-high purity hydrogen permeation cell Relationship to the case Patent applicant Address 2-1-17-301 Yonegabukuro, Sendai City, Miyagi Prefecture Name Tadahiro Omi

Claims (1)

[Claims] An ultra-high purity hydrogen permeation cell whose permeation membrane is a plurality of palladium alloy thin tubes with coil springs inserted therein, characterized in that there are no cracks on the surface of the coil springs.