JPS60264306A - Method for purifying hydrogen gas - Google Patents

Abstract

PURPOSE:To prevent the deterioration of a metal hydride in purifying hydrogen gas by injecting crude hydrogen gas into a vessel filled with the metal hydride to occlude the hydrogen in the metal hydride, decompressing the vessel to expel impurity gases remaining in the vessel, by decompressing the interior of the vessel previously to a specific pressure. CONSTITUTION:A metal hydride (MH1) is filled in the first vessel 1, and crude hydrogen gas containing impurity gases is introduced from a gas cylinder 7 thereinto under pressure to occlude the hydrogen in the metal hydride (MH1). A valve 9 of a purge pipe 8 is then opened to expel the residual impurity gases in the vessel 1, and a valve 10 is opened to decompress the interior of the vessel 1. Hydrogen gas of high purity is released from the metal hydride (MH1) in the vessel and fed to a system 13 for using the purified hydrogen gas. In this case, the vessel is connected to a vessel 14 filled with a metal hydride (MH2) having a lower hydrogen occlusion pressure than the hydrogen release pressure in the alpha-phase region of the metal hydride (MH1) through a pipe 17 to occlude the hydrogen occluded in the metal hydride (MH1) in the metal hydride (MH2). Crude hydrogen gas is then injected into the vessel 1 to prevent the deterioration of the performance due to the repeated use of the metal hydride (MH1).

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a hydrogen gas purification method, and more particularly to a hydrogen gas purification method using metal hydrides (prior art) Generally, hydrogen gas is produced by decomposition of hydrocarbons and ammonia, Alternatively, hydrogen gas is produced industrially by electrolysis of water, etc., but in addition to inert gases such as helium and argon, hydrogen gas also contains various impurity gases such as oxygen, water, nitrogen, carbon oxide, and carbon dioxide. For example, in the semiconductor industry, metal processing industry, or instrumental analysis,
The crude hydrogen gas described in Section 2 is used after being purified.

Various methods for purifying hydrogen gas have been known in the past, but in recent years certain metals or alloys have selectively absorbed hydrogen gas to form metal hydrides. Hydrogen gas purification has been proposed using the property of reversibly releasing hydrogen.

In principle, this method involves filling a container filled with such a metal hydride with a predetermined amount of crude hydrogen gas under pressure, allowing the metal hydride to selectively absorb hydrogen gas, and then filling the container with the metal hydride. Preferably, some hydrogen is released from the metal hydride by reducing the pressure inside the container, and the impurity gas remaining in the container without being occluded by the metal hydride is removed by purging the container together with this hydrogen. Purified hydrogen gas is obtained by releasing hydrogen at the hydrogen release pressure of the compound. For example, in JP-A-57-156304, 6
After storing a predetermined amount of hydrogen in the metal hydride in the container as described in step 1-, the operation of reducing the pressure inside the container and releasing impurity gas along with the hydrogen is repeated several times to absorb the metal hydride. Is there a method to reduce the pressure to the hydrogen equilibrium release pressure of J?
I'm at 9.

However, as described above, hydrogen gas contains various impurity gases. In particular, carbon monoxide, which is contained in a relatively large amount in silk hydrogen gas, adsorbs to metal hydrides and degrades them most strongly, impairing their hydrogen storage. When hydrogen gas is repeatedly purified using the absorption and release reaction of hydrogen gas in hydrides, the amount of adsorbed and oxidized carbon on the metal hydride accumulates, and its deterioration progresses.1.1.・Hydrogen storage amount 7' decrease ta, = co°°・Hydrogen 0 absorption and release 0 The reaction rate decreases, and as a result, purified hydrogen gas cannot be stably obtained over a long period of time.

(Object of the Invention) Therefore, the present invention was made to solve the above-mentioned problems in hydrogen gas purification using metal hydrides, and suppresses the deterioration of metal hydrides due to repeated absorption and release of hydrogen. Therefore, it is an object of the present invention to provide a hydrogen purification method that can stably obtain purified hydrogen gas of high purity over a long period of time.

(Structure of the Invention) The hydrogen purification method of the present invention involves applying silk hydrogen gas at a pressure higher than the occlusion pressure of the metal hydride into a container filled with a metal hydride that can absorb and release hydrogen. After the metal hydride absorbs a predetermined amount of hydrogen, the pressure inside the container is reduced to eliminate impurity gas in the container, and after this, hydrogen is released from the metal hydride. The method for obtaining hydrogen from the container as purified hydrogen gas is characterized in that the pressure inside the container is reduced to below the hydrogen release pressure in the alpha phase region of the metal hydride before applying Japanese hydrogen gas to the metal hydride. do.

FIG. 1 shows one of the metal hydrides that can be preferably used in the method of the present invention, 1. The hydrogen equilibrium pressure curve at a temperature of 40°C at +1.15 to aNin, as8 is shown, and the horizontal axis is the bonded hydrogen -3t (H/M ratio) to the metal hydride,
The vertical axis is the natural logarithm of the hydrogen equilibrium pressure P. This hydrogen equilibrium pressure has a hydrogen storage pressure shown by a solid line and a hydrogen release pressure shown by a broken line.The hydrogen storage pressure is higher than the hydrogen release pressure, and furthermore, as the 11/M ratio increases, In a flat so-called plateau region where P is substantially constant, the pressure difference between the two is approximately constant.

- In the purification of silk hydrogen gas using a metal hydride, crude hydrogen gas is applied to the container at a predetermined pressure higher than the hydrogen absorption pressure of the metal hydride at a predetermined degree, for example, 40°C, After a predetermined amount of hydrogen is stored in the metal hydride, the pressure inside the container is reduced and the metal hydride releases a portion of the stored hydrogen, removing the impurity gas remaining in the container from the container along with the hydrogen. The hydrogen released by the metal hydride is then used as purified hydrogen gas.

The absorption and desorption of hydrogen in metal hydrides usually takes place in the plateau region. When applying hydrogen to the metal hydride, ensure a large pressure difference between the applied pressure and the hydrogen storage pressure of the metal hydride to ensure rapid hydrogen storage.
Further, when obtaining purified hydrogen from the container, a large pressure difference between the hydrogen pressure in the system in which the purified hydrogen gas is used is ensured, and the purified hydrogen gas is smoothly released into the metal hydride.

Also, the amount of hydrogen removed from the container by reducing the pressure inside the container is
Usually, 5 to 10% of the total amount of hydrogen filled in the container is suitable. Furthermore, as mentioned above, the final hydrogen storage capacity is
It is preferable to set it near the end of the plateau region.

In this way, when the metal hydride releases almost no purified hydrogen in the plateau region, the above operation is repeated again to purify the crude hydrogen gas.

In the present invention, in the purification of hydrogen gas such as No. J, below-1-, before applying crude hydrogen gas to the metal hydride, the pressure inside the container is reduced to below the hydrogen release pressure in the alpha phase region of the metal hydride. In this way, the impurity gas adsorbed on the metal hydride, especially carbon oxide, is deposited together with hydrogen, and the metal hydride is released. Since the metal hydride is regenerated, even if the process of applying crude hydrogen gas to the metal hydride and refining it is repeated from step 1 onwards, the deterioration of the metal hydride is suppressed and stable, highly purified purified hydrogen is produced. You can get gas.

In the method of the present invention, the pressure inside the container may be reduced as described above each time the Japanese hydrogen gas is purified, and the metal hydride may be regenerated. The metal hydride may then be regenerated.

FIG. 2 shows an example of an apparatus suitable for carrying out the method of the present invention. The first container 1 is filled with a first metal water, a hydride M H+, and has a heating medium circuit 2 for maintaining the first metal hydride at a predetermined temperature. A Japanese hydrogen gas pipe 6 equipped with a pressure vessel 3, a flow meter 4, and a crude hydrogen gas supply valve 5 is connected to a Japanese hydrogen gas cylinder 7. In the purification of hydrogen gas, this first metal hydride is maintained at a predetermined temperature by a heat medium circuit, and
A predetermined amount of Japanese hydrogen gas is applied from the cylinder to the container at a predetermined pressure. Then, after closing the valve 5, the purge pipe 8
- Open the purge valve 9 for a predetermined period of time to remove impurity gas from the container.

The hydrogen gas purified in this manner is supplied to the purified hydrogen gas use system 13 at a predetermined pressure through a purified hydrogen gas pipe 12 having a purified hydrogen gas supply valve 10 and a pressure regulator 11.

Second container 1 as means for depressurizing the first container
No. 4 is filled with a second metal hydride M Hz which has a hydrogen storage pressure lower than the hydrogen release pressure in the alpha phase region of the first metal hydride in the operating temperature range of the device, and this metal hydrogen It has a heat medium circuit 15 for maintaining the compound at a predetermined temperature, and is electrically connected to the first container 1 through a conduit 17 having a valve 16. for example,
When the first metal hydride is 1aNis,6 described above, the second metal hydride has a hydrogen equilibrium decomposition pressure curve whose hydrogen equilibrium decomposition pressure curve is not shown in FIG. It is as^1o15.

Therefore, according to this device, before the hydrogen gas purification operation, the valve 16 is opened to conduct the first container to the second container through the conduit 17, and the hydrogen balance between the first and second metal hydrides is established. Hydrogen is released from the first metal hydride using the pressure difference between the decomposition pressures, and hydrogen is stored in the second metal hydride. In this case, if necessary, the first metal hydride is heated and/or the second metal hydride is cooled to
may promote hydrogen transfer from one metal hydride to a second metal hydride.

After regenerating hydrogen by releasing hydrogen from the α-phase region phase of the first metal hydride in this manner, crude hydrogen gas is applied to the first metal hydride for purification treatment as described above. .

Note that the hydrogen occluded in the second metal hydride is inherently highly pure, so if it is released from the second metal hydride as necessary, it can also be used as purified hydrogen gas. be able to. Further, as the pressure reduction means, a vacuum pump can be used instead of the container filled with the second metal hydride, or a pressure lower than the hydrogen release pressure in the α region phase of the first metal hydride can be used. A lowered reservoir can also be used.

(Effects of the Invention) As described below, according to the method of the present invention, before applying Japanese hydrogen gas to the metal hydride in the container, the hydrogen release pressure in the α phase region of the metal hydride in the container is reduced. The pressure is reduced to below, the hydrogen stored in the metal hydride is released in the α phase region, and the metal hydride is regenerated, so the deterioration of the metal hydride is effectively suppressed, and in this way, it is stable for a long period of time. highly purified hydrogen can be obtained.

(Example) The present invention will be explained below with reference to Examples.

0 Example 1 In the apparatus shown in FIG. 2, the first container was filled with 3.5 kg of LaNi5.6 as the first metal hydride.

This container was maintained at 40°C by a built-in heating medium circuit, and crude hydrogen gas was applied at a pressure of 15 atm for 5 minutes.
Hydrogen was stored up to an H7M ratio of 0.9 using a hydrogen flow meter attached to the container. Thereafter, the pressure inside the container was reduced, hydrogen equivalent to 0.1 in H/M ratio was released from the metal hydride, and the container was purged together with the impurity gas remaining in the container. Next, the pressure was reduced to 2 atm using a pressure regulator, and the container was connected to the system in use.

In this purification process, crude hydrogen gas with a purity of 99.99% was processed to obtain purified hydrogen gas with a purity of 99.9999% or more.

After using the purified hydrogen gas until the H/M ratio reached 0.1 in this manner, the first container and the system used were shut off, and the crude hydrogen gas was purified again in the same manner as above.

After repeating this purification process 10 times and using purified hydrogen gas, LaNi4. 3.5 kg of as^10.15 is filled, and 111... 1. The first container is electrically connected to the second container, which is maintained at a temperature of 30°C in the heating medium circuit, and hydrogen is released from the first metal hydride. This was absorbed into the second metal hydride to regenerate the first metal hydride.

As a result of the purification operation, the first metal hydride retained 90% of its initial hydrogen storage capacity when the cycle of absorbing and releasing hydrogen into the first metal hydride was repeated 5,000 times.

On the other hand, for comparison, as a result of repeating 5000 hydrogen storage and desorption cycles without regenerating the first metal hydride, the hydrogen storage amount of the first metal hydride was It decreased to 70%.

In addition, when the second metal hydride in the second container was heated to 80°C to release occluded hydrogen, this hydrogen was also heated to 99.9°C.
It had a purity of 9999% or more.

[Brief explanation of drawings]

FIG. 1 is a hydrogen equilibrium pressure curve of a metal hydride for explaining the present invention in detail, and FIG. 2 is an apparatus configuration diagram showing an example of an apparatus for carrying out the method of the present invention. 2 1... First container, 7... Crude hydrogen gas cylinder, 9
... Purge valve, 13 ... Purified hydrogen gas use system, 14
...Second container. Patent applicant Sekisui Chemical Co., Ltd. Representative Mototoshi Fujinuma 3 Figure 1 H/M

Claims (1)

[Claims] (1) A predetermined amount of hydrogen is applied to the metal hydride by applying crude hydrogen gas at a pressure higher than the storage pressure of the metal hydride into a container filled with a metal hydride that can absorb and release hydrogen. After occluding hydrogen, the pressure in the container is reduced to eliminate impurity gas in the container, and then hydrogen is released from the metal hydride, and the hydrogen is obtained from the container as purified hydrogen gas, the method comprising: A method for purifying hydrogen gas, characterized in that before applying crude hydrogen gas to a metal hydride, the pressure inside the container is reduced to a hydrogen release pressure in an α-phase region of the metal hydride or less.