JP3273641B2 - Hydrogen gas purification equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrogen gas purifying apparatus using a hydrogen permeable membrane of a palladium alloy membrane, and more particularly, to desorption of impurities from a portion of a palladium alloy membrane which comes into contact with high-temperature purified hydrogen gas. The present invention relates to a hydrogen gas purifying apparatus on which a surface film for preventing the formation of hydrogen gas is formed. BACKGROUND ART In the semiconductor manufacturing industry, which has been developing remarkably in recent years, hydrogen gas is actively used as an atmosphere gas in various processes. With the improvement in the degree of integration of semiconductors, the demand for improving the purity of hydrogen gas has been increasing. For this reason, p
pm nitrogen, hydrocarbons, carbon monoxide,
It is desired to remove impurities such as carbon dioxide, oxygen, and moisture to purify to a high level of ppb order or lower.

[0002]

2. Description of the Related Art As a method for purifying hydrogen gas, a purification method utilizing the selective permeability of hydrogen of a palladium alloy membrane under heating, and a combination of a chemical reaction with a metal catalyst and a physical adsorption with an adsorbent at room temperature are used. There are known a room temperature adsorption purification method, a cryogenic adsorption purification method utilizing the physical adsorptivity of an adsorbent installed at cryogenic temperature using liquid nitrogen as a cold heat source, and the like.

[0003] Among these, palladium or a palladium alloy made of palladium and silver, gold, etc. selectively permeates only hydrogen gas. Therefore, a hydrogen gas purifying apparatus for obtaining high-purity hydrogen gas by utilizing this characteristic. Is attracting attention again, and is frequently used. This hydrogen gas purifying apparatus includes, for example, a palladium alloy hydrogen permeator main body, a cooling pipe, a connection pipe, a valve, a joint, and the like. Various types of hydrogen permeable devices are known, but recently, one end is sealed, and a plurality of palladium alloy thin tubes into which a coil spring is inserted are fixed to a tube sheet at an open end, It is housed in a cylindrical container, the interior is partitioned into two spaces by the palladium alloy and the tube sheet, and the mainstream is a palladium alloy thin tube in which the outside is a primary side and the inside is a secondary side. Most of the materials for these devices, except for the palladium alloy thin tube, are usually made of stainless steel.

When purifying hydrogen gas, the hydrogen permeable device is set to 300
While heating to ~ 500 ° C, the raw hydrogen gas is supplied to the primary side in a pressurized state, and only the hydrogen gas is selectively permeated from the outside (primary side) to the inside (secondary side) of the palladium alloy thin tube, It reaches the outlet of the purified gas via the space in the flow path of the coil spring inserted inside the narrow tube, the secondary space of the permeator, the cooling pipe, and the like. The palladium alloy thin tube uses a palladium alloy membrane that has been sufficiently degassed, so that no impurity gas leaks and the purity of hydrogen gas at the time of permeation is substantially 100%.

[0005]

However, at the time of passing through the palladium alloy membrane, even if the hydrogen gas is of extremely high purity, the cooling pipe, valve,
When reaching the outlet of the refinery via pipe joints, impurities such as nitrogen, hydrocarbons, carbon monoxide, carbon dioxide, oxygen, and moisture, which are considered to have been adsorbed on these surfaces, though in trace amounts, are mixed. Therefore, in particular, there has been an aspect that it cannot always be said that it is sufficient for recent demands for ultra-high purity. For this reason, the permeator body, pipes, and valves used are those whose inner surfaces have been polished, or the inner surfaces are baked while heating them during use of the device to desorb the adsorbed impurities, By removing the impurities to the outside of the system, impurities other than water have been almost completely removed.

[0006] However, even if such various measures are taken, the contamination of water cannot be completely prevented, and these technical improvements have been made to purify ultra-high-purity hydrogen having an impurity concentration of ppb level or less. This is an important issue for obtaining a stable gas.

[0007]

Means for Solving the Problems The inventors of the present invention have steadily prevented the incorporation of water due to desorption and the like, and have therefore begun research to obtain purified hydrogen gas of extremely high purity. Was able to understand the fact that effective surface polishing and baking treatments did not always have a sufficient effect on moisture, and as a result of further intensive research on this fact, the high temperature It has been found that the object can be achieved by performing a chromium film forming treatment on the surface of the gas contacting part of the part that comes into contact with the purified hydrogen gas, and completed the present invention.

That is, the present invention relates to a hydrogen gas purifying apparatus utilizing the hydrogen selective permeability of a palladium alloy membrane under heating, wherein a secondary side of the purifying apparatus, the secondary side having permeated the palladium alloy membrane , Splices in palladium alloy thin tubes
Type selected from cooling, cooling pipe, connection pipe and pipe joint
Alternatively, there is provided a hydrogen gas purifying apparatus characterized in that a chromium film is formed on a surface of a gas contacting part of two or more parts with purified hydrogen gas . Except for the palladium alloy film, the parts on which the chromium film is formed in the present invention are used for parts that come into contact with purified hydrogen gas at high temperatures, such as the permeator body, cooling pipes, valves, connection pipes, and springs inserted into the palladium alloy thin tubes. Usually, stainless steel is mainly used, and nickel steel or the like is partially used.

There is no particular limitation on the method for forming the chromium film. In the gas phase method, for example, a vapor deposition method including vacuum
In the VD method and the liquid phase method, for example, electroplating and hot-dip plating are typical methods. Of these, hard chrome plating, which is generally widely used, is preferred. The thickness of the chromium film layer to be formed is usually 0.01 μm to 100 μm, preferably 0.1 μm to 100 μm.
m to 30 μm. If the thickness is smaller than this, it is difficult to form a uniform coating layer depending on the conditions, and a sufficient effect cannot be obtained.If the thickness is larger than this, cracking or peeling of the plating layer is likely to occur, which is stable. The effect becomes difficult to obtain.

Next, the present invention will be described more specifically with reference to the drawings. FIG. 1 is a flow sheet of the rare gas purifying apparatus of the present invention. In FIG. 1, a permeator 1 includes a plurality of thin tubular palladium alloy membranes 3 each having a spring 2 inserted therein for preventing deformation due to pressure and having one end sealed, and a tube sheet 4 to which this is fixed. Thereby, the raw material hydrogen gas chamber 5 (primary side) and the purified hydrogen gas chamber (secondary side) 6 are separated from each other. The raw hydrogen gas chamber 5 includes a raw hydrogen gas pipe 9 having a raw hydrogen gas inlet 7 and a raw hydrogen gas valve 8, a nitrogen gas pipe 12 having a replacement nitrogen gas inlet 10 and a nitrogen gas valve 11, An exhaust pipe for discharging an appropriate amount of hydrogen gas in which impurities are concentrated during purification and a nitrogen gas during replacement, and an exhaust pipe 16 having an exhaust gas inlet 13, a flow control valve 14, and an exhaust gas outlet 15; Is connected. A cooling pipe 17 is connected to the purified hydrogen gas chamber 6, and a purified hydrogen gas pipe 20 having a purified hydrogen gas valve 18 and a purified hydrogen gas outlet 19 is connected downstream of the cooling pipe 17.

[0011]

FIG.

Here, the parts that come into contact with high-temperature hydrogen gas except for the palladium alloy film are the spring 2, the tube plate 4, the purified hydrogen gas chamber 6 of the permeator 1, and the cooling pipe 17. A film is formed on the surface by chrome plating. The permeator 1 is supplied with the raw hydrogen gas while being heated to 350 to 500 ° C. by the heater 21 via the temperature controller, and the high-temperature purified hydrogen gas that has passed through the palladium alloy membrane passes through the cooling pipe 17. After being cooled to room temperature, it is extracted via a purified gas outlet 19 and supplied to a semiconductor manufacturing process or the like.

[0013]

【Example】

Example 1 An apparatus for purifying hydrogen gas having the same configuration as that shown in FIG. 1, in which a wire made of SUS316L steel having a diameter of 0.25 mm was pitched 0.75 mm, a coil diameter was 1.3 mm, and a length was 240 m.
m, and a spring having a thickness of 3 μm and subjected to hard chrome plating is applied to an outer diameter of 1.6 mm and an inner diameter of 1.45.
78 pieces were inserted into a palladium ternary alloy thin tube made of gold, silver, and palladium having a diameter of 245 mm and a tip of 245 mm. Next, a hard chromium plating treatment of 5 μm thickness is performed on a nickel tube sheet having a disk-like shape having a diameter of 48.6 mm and a thickness of 5 mm and 78 through-holes having a diameter of 1.6 mm evenly formed in a flat plate portion excluding a peripheral portion. After performing the above, the plating layer of the peripheral portion serving as a welded portion and the peripheral wall portion of the through hole is scraped off, 78 palladium alloy tubes are inserted into the through hole, and each is welded and fixed to a tube sheet, Integrated.

A pipe made of SUS316L steel having an outer diameter of 48.6 mm and a cap made of SUS316L steel having an outer diameter of 48.6 mm are welded, and a hydrogen gas pipe for replacement, a nitrogen gas pipe for replacement, and a SUS316L steel pipe having an outer diameter of 40 mm are welded. An exhaust pipe provided with an exhaust gas inlet made of a pipe and a disk was attached by welding to form a raw hydrogen gas chamber (primary side). On the other hand, an outer diameter having a 2 μm-thick hard chrome plating on the inner surface.
A cooling pipe manufactured by welding four SUS316L steel pipes of 7 mm and 1 m in length, and eight welding elbow joints of SUS316L steel with an outer diameter of 12.7 mm and having an inner diameter of 3 μm and having a thickness of 3 μm on the inner surface. And SUS with an outer diameter of 48.6 mm with a hard chrome plating of 3 μm thickness on the inner surface
A purified hydrogen gas chamber (secondary side) was manufactured by welding a 316L steel cap. Subsequently, the tube plate integrated with the palladium alloy tube, the raw material hydrogen gas chamber, and the purified hydrogen gas chamber were welded together to obtain a permeator. A heater for heating was attached to the outside of the permeator to complete a hydrogen gas purifying apparatus.

Purification of hydrogen gas was performed as follows. The normal start-up operation raises the temperature of the permeator to 420
° C., as a gauge pressure 6 kgf / cm ² of the raw material hydrogen gas at a gauge pressure of 2 kgf / cm ² purified hydrogen gas 8N
While taking out at L / min, a heater was wound around the purified gas pipe and the cooling pipe at a temperature of 100 ° C. or less, and
After performing a baking treatment at 5 ° C. for 5 hours, purification was started while flowing hydrogen gas as it was. A part of the purified gas was introduced into an atmospheric pressure ionization mass spectrometer (manufactured by Hitachi Tokyo Electronics Co., Ltd.) at a flow rate of 1 NL / min, and the water content was measured. As a result, the water content was 0.1 ppb or less throughout the continuous measurement time of 5 hours. Met. The other impurities were all 0.1 ppb or less.

Comparative Example 1 A test was conducted in the same manner as in Example 1 except that a device in which a spring, a tube plate, a purified hydrogen gas chamber, and a cooling tube were not subjected to chromium plating was used. 0.1
ppb or less, but only water was always 7 ppb or more throughout the continuous measurement time of 5 hours.

[0017]

According to the present invention, the drawback of the prior art that several ppb of water generated by contact of high-temperature purified hydrogen gas with the piping material after the palladium alloy membrane is mixed into the purified gas is prevented. All impurity concentrations are 1p
It has become possible to reliably obtain an ultrahigh-purity purified hydrogen gas of not more than 0.1 ppb, especially not more than 0.1 ppb.

[0018]

[Brief description of the drawings]

FIG. 1 is a flow sheet of a hydrogen gas purifying apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Permeator 2 Spring 3 Palladium alloy film 4 Tube plate 5 Raw material hydrogen gas chamber 6 Purified hydrogen gas chamber 7 Raw material hydrogen gas inlet 8 Raw material hydrogen gas valve 9 Raw material hydrogen gas pipe 10 Replacement nitrogen gas inlet 11 Nitrogen gas valve 12 Nitrogen gas Piping 13 Exhaust gas inlet 14 Flow control valve 15 Exhaust gas outlet 16 Exhaust pipe 17 Cooling pipe 18 Purified hydrogen gas valve 19 Purified hydrogen gas outlet 20 Purified hydrogen gas pipe 21 Heater

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C01B 3/56 B01D 53/22 B01D 71/02 500

Claims (2)

(57) [Claims] 1. A hydrogen gas purifying apparatus utilizing the selective hydrogen permeable palladium alloy film under heating, a secondary side that has been transmitted through the palladium alloy membrane of the purified system, secondary
Side chamber, spring in palladium alloy thin tube, cooling pipe, connection
A hydrogen gas purifying apparatus, characterized in that a chromium film is formed on the surface of one or more parts selected from a continuation pipe and a pipe joint, which is in contact with the purified hydrogen gas . 2. The refining apparatus according to claim 1, wherein the thickness of the chromium film formed on the surface of the gas contact portion is 0.01 μm to 100 μm.