JPS6086005A - Hydrogen gas purification - Google Patents

Abstract

PURPOSE:To purify a hydrogen gas with low energy consumption, by packing metal hydrogen compounds having different hydrogen equilibrium decomposition pressure at a given operation temperature in the order of hydrogen equilibrium decomposition pressure in the containers, passing a crude hydrogen gas successively through the containers, occluding and releasing hydrogen. CONSTITUTION:Metal hydrides having different hydrogen equilibrium decomposition pressure at a given operation temperature are packed into the containers 1, 2 and 3, respectively, in the order of hydrogen equilibrium decomposition pressure. A crude hydrogen gas is sent through the feed pipe 5 to the container 1 at a given temperature, hydrogen is occluded, and impure gases are exhausted from the purge valve 7. When the valve 6 is opened, the containers 1 and 2 are communicated, since the container 2 has lower hydrogen equilibrium decomposition pressure than the container 1, occluded hydrogen is released in the container 1 by this pressure difference, and impure gases occluded in the container 2 are released from the purge valve 10. The same operation is carried out between containers 2 and 3, and purified hydrogen is stored in the reservoir tank 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydrogen gas purification method, and more particularly to a hydrogen gas purification method using a metal hydride.

Hydrogen gas is generally produced industrially by decomposing hydrocarbons and ammonia, or by electrolyzing water, but hydrogen gas can be produced using inert gases such as helium and argon, as well as oxygen, water, nitrogen, and oxidized gas. Since it contains various inert gases such as carbon and carbon dioxide, the above-mentioned crude hydrogen gas is used after being purified, for example, in fields such as semiconductor industry, metal processing industry, and instrumental analysis.

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 using the property of reversibly releasing hydrogen has been proposed. In principle, this method involves filling a container filled with metal hydride with crude hydrogen gas under a predetermined pressure, allowing the metal hydride to selectively absorb hydrogen gas, and then filling the container with metal hydride. Remaining impurity gases that are not occluded are removed by purging the container, and then hydrogen is released at the hydrogen equilibrium decomposition pressure of the metal hydride to obtain purified hydrogen gas.

For example, JP-A-55-149104 discloses that a first metal hydride with a low equilibrium hydrogen decomposition pressure and a second metal hydride with a higher hydrogen equilibrium decomposition pressure are used in combination in a predetermined temperature range, and Hydrogen containing impurity gas is absorbed at a low temperature while being in contact with the first metal hydride, and then absorbed into the metal hydride to release hydrogen from the first metal hydride, which is purified in this way. After hydrogen is absorbed while being brought into contact with the second metal hydride cooled to a predetermined low temperature, impurity gases that are not occluded by the 11111ml metal hydride are removed again, and then the metal hydride is heated to produce purified hydrogen. and repeat this operation,
A method for obtaining purified hydrogen from a final stage metal hydride is disclosed.

However, as mentioned above, this method requires alternate heating and cooling of the metal hydride in order to absorb and release hydrogen, which has the problem of consuming a large amount of energy. Since the hydrogen equilibrium decomposition pressure in metal hydrides gradually increases, this method can obtain high-pressure purified hydrogen from low-pressure crude hydrogen, but conversely, when obtaining low-pressure purified hydrogen from high-pressure crude hydrogen, There are some problems that cannot be applied.

The present invention has been made in order to solve the above-mentioned problems in hydrogen gas purification using metal hydrides. The purpose of the present invention is to provide a hydrogen purification method suitable for obtaining low-pressure purified hydrogen from high-pressure crude hydrogen while reducing loss and thus reducing energy consumption for absorbing and desorbing hydrogen into metal hydrides. shall be.

In the hydrogen purification method of the present invention, at least two types of metal hydrides having different hydrogen equilibrium decomposition pressures at a predetermined operating temperature are respectively filled in containers and connected in series, and a first metal hydride having a high hydrogen equilibrium decomposition pressure is connected in series. After supplying crude hydrogen gas to the first container filled with metal hydride and storing hydrogen, the residual inertia is removed, and then the first and second metal hydrides are 7, the first metal hydrogen gas releases hydrogen due to inertia force due to the difference in elementary equilibrium decomposition pressure, and this hydrogen is stored in the second metal hydrogen gas, then impurity gas is removed, and this second metal hydrogen gas is removed. It is characterized by obtaining (higher purity) hydrogen power from the metal hydrides of 2.

The present invention will be explained below based on the drawings.

FIG. 1 shows a detailed set-up for carrying out the method according to the invention.
An example is shown below, in which the first and second containers have different hydrogen equilibrium decomposition pressures at the operating temperature, for example, room temperature.
and a third metal hydride (hereinafter referred to as MH
I, MH2 and Ml-13. ) are filled in sequentially numbered f so that the decomposition pressure of each i-digit hydrogen molecule decreases in this order. The container IG filled with MHI, which has the highest hydrogen equilibrium decomposition pressure, is connected to a crude hydrogen power common supply pipe 5 via a crude hydrogen gas supply valve 4, and communicated through a purified hydrogen power outlet valve 6. Possibly connected to an adjacent second container 2 , and also connected via a purge valve 7 to a reservoir tank 8 for nocuzi gas. The second container 2 is also communicatively connected to an adjacent third container through a purified hydrogen gas outlet valve 9, and a purge valve 10.
It is connected to the purge gas reservoir tank 8 via. The third container 3 is Ifil! It is connected to a purified hydrogen gas reservoir tank 12 through a hydrogen gas outlet valve 11, and is also connected to a purge gas reservoir bank 8 through a purge valve 13.

In the illustrated apparatus, a second series of apparatuses consisting of containers having the same configuration as the above-mentioned series of apparatuses consisting of the first, second and third containers is arranged, and corresponding parts are indicated by dashed references. indicated by numbers.

The metal hydride in each container generates heat when absorbing hydrogen, and also absorbs heat when releasing hydrogen, but in order to keep the temperature of the metal hydride substantially constant, each container is Heat transfer pipes 14 are introduced and can heat or cool the metal hydride.

Next, the operation of the above device will be explained based on FIG. 2.

Figure 2 shows the hydrogen equilibrium decomposition pressure curve of metal hydride, and the horizontal axis is the amount of bound hydrogen per mole of metal hydride (H/M).
, the vertical axis indicates hydrogen equilibrium decomposition pressure (P). Strictly speaking, the hydrogen equilibrium decomposition pressure is slightly different between the absorption pressure shown by the solid line and the release pressure shown by the broken line, and hydrogen transfer between metal hydrides at a given temperature is caused by the pressure difference between the hydrogen release pressure and the hydrogen storage pressure. However, in practice, it may be determined that the difference in hydrogen equilibrium decomposition pressure is used.

Therefore, when crude hydrogen gas containing impurity gas is supplied from the crude hydrogen gas supply pipe 5 to the first container 1 at a predetermined pressure,
MHI stores hydrogen at a predetermined high pressure, and impurity gases remain in the container without being stored by MHI. Therefore, the crude hydrogen gas supply valve 4 is closed, the purge valve 7 is opened to discharge the impurity gas from the container, and then the purified hydrogen gas outlet valve 6
When opened to communicate the first container and the second container, the MH
Since the hydrogen equilibrium decomposition pressure of 2 is lower than that of MHI, MHI releases occluded hydrogen due to this pressure difference, and MH2 occludes this hydrogen at a lower pressure, and the remaining impurity gas is removed as before. It stays in the container without being occluded by MH2. Therefore, after hydrogen release and storage is completed in this way, if the purified hydrogen gas outlet valve 6 that communicates the first container and the second container is closed and the purge valve 1o of the second container is opened, The impurity gas is discharged from the second container.

By repeating the same operation for the third container 3,
MH3 stores hydrogen at a lower pressure, and after purging impurity gas from this container, when the purified hydrogen gas outlet valve 11 is opened, highly purified hydrogen is stored in the reservoir cylinder 12 for purified hydrogen gas. From this, purified hydrogen gas can be obtained.

If the same operation is performed with a half-cycle delay for the second series of devices consisting of vessels 1°, 2" and 3", purified hydrogen gas can be obtained continuously from the first and second series of devices. , - It is obvious that the degree of purification of the hydrogen gas obtained increases as the number of containers increases in the equipment in the series.In general, the hydrogen release pressure of the nth metal hydride and the (n+1)th It is preferable that the difference between the hydrogen absorption pressure of the metal hydride and the hydrogen storage pressure is 0.2 atm or more in consideration of the pressure drop between the containers.In addition, the pressure on the purge side is also lower than the hydrogen release pressure of the metal hydride in each container. It is preferable that the pressure is lower than 0.2 atm.

As described above, according to the method of the present invention, at a predetermined operating temperature, MHI on the crude hydrogen gas supply side has the highest hydrogen equilibrium decomposition pressure, and MH2 and MH3 have lower hydrogen equilibrium decomposition pressures in this order. As shown in the figure, containers filled with each metal hydride are connected in series to create a pressure difference between the hydrogen equilibrium decomposition pressures of the metal hydride in each container, and the movement of hydrogen gas between the containers is controlled by this pressure difference. Therefore, unlike the case where the metal hydride is alternately heated and cooled to release and store hydrogen, loss of sensible heat is small and the amount of energy required can be reduced. Especially if the operating temperature is set to room temperature,
An inexpensive heat medium such as water at room temperature can be used.

Furthermore, according to the method of the present invention, low-pressure purified hydrogen gas can be obtained from high-pressure crude hydrogen gas.

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

EXAMPLE In the apparatus shown in FIG. 1, containers 1 and 1 were filled. When crude hydrogen gas is applied at 6 atm (absolute) to the first container at an operating temperature of 20°C, the differential pressure of hydrogen equilibrium decomposition pressure between each container is the crude hydrogen gas, and Pn'' is Pn indicates the hydrogen absorption pressure of the metal hydride in the n-th stage container, and Pn indicates the hydrogen release pressure of the metal hydride in the n-th stage container.

As previously described, the first vessel was filled with crude hydrogen gas at 6 atmospheres, allowing the MHI to selectively absorb hydrogen, and then purging 5% of the gas. Then, the first container and the second
As shown in Figure 2, by using the pressure difference between the hydrogen storage pressure of MH2 and the hydrogen release pressure of MHI,
MHI was allowed to release hydrogen, and this hydrogen was stored in MH2.

After occlusion is completed, 5% of impurity gas is purged from the container,
The second container and the third container were brought into communication.

Similarly, MH2 is made to release hydrogen, and this hydrogen is transferred to the third
The MH3 in the container was occluded, and 5% of it was purged.

In this way, 100 parts of crude hydrogen gas can be fed into the first container and 86 parts of purified hydrogen can be obtained from the third container, the acquisition rate being When operated, it was 6Nrrr/hour.

Furthermore, when crude hydrogen gas with a purity of 99.9% is used, the purity of the purified hydrogen gas is 99.99% at the outlet of the first container, 99°999% at the outlet of the second container, and 99.99% at the outlet of the second container. 3
At the outlet of the container, the purity exceeds the analytical limit and is 99% pure.
．． It was 9999% or more.

[Brief explanation of the drawing]

FIG. 1 shows an example of an apparatus configuration suitable for carrying out the method of the present invention, and FIG. 2 is a graph showing the relationship between the H7M ratio of a metal hydride and the hydrogen equilibrium decomposition pressure. 1.2 and 3...first, second and third containers, respectively, 4...purified hydrogen gas supply valve, 5...crude hydrogen gas supply pipe, 6.9.11...purified hydrogen Gas outlet valve, 7.
10.13... Purge valve, 8... Reservoir tank for purge gas, 12... Reservoir tank for purified hydrogen gas. Patent applicant Mototoshi Fujinuma, Representative of Sekisui Chemical Co., Ltd.

Claims (1)

[Claims] (1) At least two types of metal hydrides having different hydrogen equilibrium decomposition pressures at a predetermined operating temperature are respectively filled in a container and connected in series, and the first metal hydride having a high hydrogen equilibrium decomposition pressure is filled. After supplying crude hydrogen gas to the first container containing hydrogen and storing hydrogen, removing impurity gas,
Next, hydrogen is released from the first metal hydride due to the difference in hydrogen equilibrium decomposition pressure between the first and second metal hydrides, this hydrogen is stored in the second metal hydride, and then impurity gas is removed. A hydrogen gas purification method characterized in that hydrogen gas with higher purity is obtained from this second metal hydride.