JPH0621001B2 - Ultra high purity hydrogen permeation cell - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ultra-high purity hydrogen permeation cell, and more specifically to an ultra-high purity hydrogen permeation cell using a palladium alloy thin tube in which a coil spring having no crack is inserted. Regarding

Demand for hydrogen gas in the semiconductor industry and the like is rapidly increasing, and with the advancement of technology in these fields, the gas used must be of extremely high purity.

[Conventional technology]

It is known that palladium and a palladium alloy selectively permeate only hydrogen gas, and a hydrogen purifier using a palladium alloy permeable membrane is used to obtain high-purity hydrogen by utilizing this characteristic. Such a hydrogen purifier is composed of, for example, a palladium alloy hydrogen permeation cell, a gas cooler, piping, a joint, a valve, and the like.
A hydrogen permeation cell is normally housed in a cell with a plurality of palladium alloy capillaries sealed at one end fixed to a tube sheet at the open end, and the palladium alloy and tube sheet divide the cell into two spaces. The outer side of the palladium alloy thin tube is the primary side and the inner side is the secondary side. A spring is inserted inside the palladium alloy thin tube in order to withstand a pressure difference between the primary side and the secondary side and to maintain a flow passage space for the permeated hydrogen.

When purifying hydrogen gas, while heating the hydrogen permeation cell to 300 to 500 ° C, the raw material gas is supplied to the primary side of the cell under pressure, and only hydrogen gas is supplied from the outside (primary side) to the inside (second side) of the palladium alloy capillary. It is selectively permeated to the secondary side) and reaches the outlet of the purified gas of the cell via the flow passage space of the coil spring and the secondary side space of the cell.

Palladium alloy capillaries using a fully degassed and highly pure palladium alloy membrane have passed the helium leak test at 1 × 10 ^-10 atm / cc sec, and have no leakage of impurities. The purity of hydrogen gas at the time of permeation is said to be substantially 100%.

[Problems to be solved by the invention]

However, even if a hydrogen permeation cell using such a palladium alloy thin tube is used in a refining device, the purity is lowered at the cell outlet, and even if refining is continued for a long time, 99.999 to 99.9999.
However, there is a problem in that it is not possible to obtain a purified hydrogen gas having a higher purity than that, and it is not possible to cope with the advancement of technology such as manufacturing of submicron class semiconductors.

In the present invention, by investigating the cause of the decrease in purity in the conventional hydrogen permeation cell and improving it, 99.99999%
It is to obtain a hydrogen permeation cell for the above ultra-high purity hydrogen gas.

[Means for solving problems]

As a result of continuous research to obtain ultra-high purity hydrogen from a hydrogen permeation cell using a palladium alloy thin tube, the present inventors have many fine cracks in the coil spring inserted in the palladium alloy thin tube, and these cracks are The inventors have found that the purity of the purified hydrogen gas is greatly affected and have reached the present invention.

That is, the present invention is an ultra high purity hydrogen permeation cell having a plurality of palladium alloy capillaries having a coil spring inserted therein as a permeable membrane, wherein the surface of the coil spring has no cracks. It is a transparent cell.

The hydrogen permeation cell of the present invention is configured as shown in the schematic longitudinal sectional view of FIG. 5, and one end is sealed in a cylindrical cell 4 made of stainless steel or the like having a gas inlet 1, an outlet 2 and a bleeding port 3. , 6 in which the coil springs 5 are inserted are fixedly housed in the tube sheet 7 at their open ends, and the palladium alloy thin tubes 6 ,. The inside of the cell is partitioned into two spaces by the palladium alloy thin tubes 6, ..., 6 with the outside as the primary side and the inside as the secondary side.

In the present invention, the material of the coil spring inserted in the palladium alloy thin tube has sufficient heat resistance at the operating temperature,
A material that does not react with the palladium alloy and has a sufficiently small amount of gas component is selected. The metal wire of the coil spring is stainless steel, Co-Ni-Ci alloy, etc., and the diameter of the metal wire is 0.1.
~ 0.8 mmφ, the outer diameter of the coil is slightly smaller than the inner diameter of the palladium alloy thin tube, and usually 0.8 ~
It is 2.8 mm.

The surface of the coil spring usually has fine dents of various shapes such as wear scratches, cracks, and small holes, which are difficult to see with the naked eye but can be observed in detail with a magnified image by an electron microscope. it can. However, the deep dent cannot be projected to the inside, and this part appears black.

In the present invention, the crack means a dent in which the area of the dent on the surface of the spring which appears black in a 4500 times magnified image by an electron microscope is 20 mm ² or more.

FIG. 1 is an electron microscope 450-times enlarged view of a coil spring having no crack on the surface used in the present invention,
FIG. 2 is an enlarged view of 4500 times. There are linear depressions on the surface, but they are shallow and cracks do not exist.

FIG. 3 is a 450 times enlarged view of the surface of a conventionally used coil spring, and FIG. 4 is a 4500 times enlarged view.
In FIG. 3, cracks are shown in black and scattered, and in FIG. 4, the area of the black portion is larger than 20 mm ² , and it is recognized that the cracks are present. As is clear from Fig. 3, there are 45 cracks as shown in Fig. 4.
There are an extremely large number within one field of view at 0x magnification. As shown in FIG. 1, the surface of the coil spring used in the present invention has almost no cracks in the width of the 450 × magnified field image. In the present invention, a state in which almost no cracks are observed in the 450 × magnified field image is defined as a state without cracks.

When a coil spring with a crack on the surface is used in a hydrogen permeable cell, impure gas such as moisture and air that has entered and stayed in the crack gradually leaks to the outside during gas purification,
High purity hydrogen gas cannot be obtained because it is mixed into the purified hydrogen gas for a long time to lower the purity.

The method for obtaining the crack-free spring used in the present invention is not particularly limited, but the spring can be obtained as follows, for example. Stainless steel or Co-Ni-Cr alloy, etc., which have been sufficiently degassed by vacuum melting once or twice, are cold drawn, and after bright annealing, surface polishing is performed with a polishing cloth or the like. Then, after cold drawing to a predetermined thickness and heat treatment at 700 to 800 ° C., a wire having no cracks is formed by performing a process such as chemical polishing if desired, and the wire is wound around a core wire and processed into a coil spring.

As the palladium alloy thin tube into which the coil spring is inserted, one having an outer diameter of about 1.0 to 3.0 mm and a thickness of about 30 to 200 μ is usually used in view of hydrogen permeation efficiency and mechanical strength. The material is not particularly limited as long as it has a large hydrogen permeability and good workability, but an alloy of palladium and silver, gold, rhodium, ruthenium or the like is preferable, for example, an alloy of palladium and silver of 5 to 50%, palladium. And silver 5-40%
And alloys consisting of 1 to 20% gold, and alloys consisting of 5 to 40% palladium and silver and 2 to 10% rhodium. These alloys are used for hydrogen permeation cells after being made into thin tubes by conventional methods. To be done.

[Effect of the invention] By using the ultra-high purity hydrogen permeation cell of the present invention,
It will be possible to purify hydrogen gas to a purity of 99.99999% or higher, which could not be obtained in the past, and it is expected to make a significant contribution to the ultra-high integration of semiconductors.

〔Example〕

Example 1 A spron (Co-Ni-Cr alloy, manufactured by Seiko Electronic Components Co., Ltd.) from which internal gas was sufficiently removed by vacuum melting twice was brought to 0.8 mmφ by cold wire drawing, and light brightness annealing and endless polishing cloth were carried out. The surface of the wire was polished to remove cracks on the surface of the wire. Next, after cold drawing to 0.3 mmφ, heat treating in nitrogen gas at 700 ° C, and then winding a wire drawn to 0.2 mmφ around the core wire to make a coil spring with an outer diameter of 1.3 mm, a pitch of 0.75 mm, and a length of 340 mm. And No cracks were observed on the surface of this coil spring as shown in FIGS. 1 and 2.

135 palladium tubules having an outer diameter of 1.6 mm, a thickness of 80 μ, and a length of 330 mm, into which such a coil spring without cracks was inserted, were fixed to a tube plate and housed in the cell to obtain a hydrogen permeable cell.

This hydrogen permeation cell raw hydrogen gas (cylinder packed hydrogen) primary pressure 3.5kg / cm ² G, the secondary side pressure 0.03kg / cm ² G 15
Flowing at 00 / hr, dew point measurement and nitrogen and oxygen analysis were performed on the cell outlet gas. As a result, as shown in Table 1, it was found that hydrogen gas having a purity of 99.99999% or more was obtained. Panametric model for dew point measurement
Obtain the water content using Model 700 (manufactured by Nippon Panametric Co., Ltd.)
₂ , N ₂ , CO, CO ₂ , and methane were analyzed by gas chromatograph (TCD) and flame ion detector (FID), and the difference obtained by subtracting them from the whole was taken as the purity of hydrogen gas.

Comparative Example 1 Instead of using a crack-free coil spring,
Hydrogen gas was purified under the same conditions as in Example 1 using the same hydrogen permeation cell as in Example 1 except that coil springs having various cracks on the surface were used as shown in FIGS. The results are shown in Table 1, and the purity was less than 99.9999%.

[Brief description of drawings]

1 and 2 are enlarged views of the surface of a coil spring used in the present invention, FIGS. 3 and 4 are enlarged views of the surface of a conventional coil spring, and FIG. 5 is a schematic vertical sectional view of a hydrogen permeation cell. It is a figure. The numbers in FIG. 5 are as follows. 1 ... Inlet, 2 ... Outlet, 3 ... Bleed port, 4 ... Cell, 5 ... Coil spring, 6 ... Palladium alloy thin tube, 7 ... Tube plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yutaka Koyama 13-11 Uenohigashi, Tomita, Sendai City, Miyagi Prefecture

Claims (1)

[Claims] 1. An ultra-high purity hydrogen permeation cell having a plurality of palladium alloy capillaries having coil springs inserted therein as a permeable membrane, wherein the surface of the coil spring is free of cracks. Transparent cell