JPS6227302A - Treatment of hydrogen storage alloy - Google Patents

Abstract

PURPOSE:To effectively restore the performance of a hydrogen storage alloy when the hydrogen storage alloy is repeatedly subjected to hydrogenation with crude gaseous hydrogen of low purity and dehydrogenation, by hydrogenating the hydrogen storage alloy with gaseous hydrogen of high purity and dehydrogenating it. CONSTITUTION:A hydrogen storage alloy such as a Ti-Mn alloy is repeatedly subjected to hydrogenation with crude geseous hydrogen of <=99.9% purity and dehydrogenation. In order to improve the performance of the hydrogen storage alloy deteriorated by impurities, the alloy is hydrogenated at least once with gaseous hydrogen of >=99.9% purity and dehydrogenated. The initial superior performance of the hydrogen storage alloy can be restored. This method is applicable to the separation of gaseous hydrogen from crude gaseous hydrogen by purification and other many fields in which the hydrogen storage alloy is utilized. This method is useful because it prolongs the life of the hydrogen storage alloy and is economical.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to hydrogen storage, which occurs when a hydrogen storage alloy is repeatedly hydrogenated and dehydrogenated using crude hydrogen gas with a hydrogen gas purity of 99.9% or less. It relates to a processing method for improving the performance deterioration caused by impurity components of the alloy.
It can be widely used in various fields of application of hydrogen storage alloys, mainly in the field of separating and refining hydrogen gas from crude hydrogen gas.

Conventional technology Hydrogen storage alloys are used in the storage of hydrogen, I transport medium, energy conversion medium such as pressure and heat, and the separation of hydrogen gas.

Its application and development as a functional material, mainly as a purification medium, is being actively developed.

This hydrogen storage alloy is used in various application fields, mainly in the field of separating and refining hydrogen gas from crude hydrogen gas, and in the storage and transportation field of hydrogen. It is often seen that the performance as a hydrogen storage alloy deteriorates due to the influence of

In this case, the impurity component absorbs blue onto the surface of the hydrogen storage alloy, inhibits the reaction between hydrogen gas and the hydrogen storage alloy, significantly reduces the reaction rate, and reduces the storage capacity of hydrogen gas. Ta.

In response to the R effect on hydrogen storage alloys due to impurity components, the problem of how to prevent adsorption of impurity components and maintain the performance of hydrogen storage alloys has been an important issue from a practical standpoint.

In the prior art, no practical treatment method has been found for this problem, and the deterioration in performance has been treated as the end of the life of the hydrogen storage alloy. However, on a laboratory scale, while heating to a relatively high temperature of 300 to 500°C,
It has been known that forced degassing using a vacuum pump or the like can restore significantly degraded performance. However, such one-temperature, one-state gas treatment is extremely difficult in practice.

In addition to the problems that the invention aims to solve, problems such as a decrease in the reaction rate of the hydrogen storage alloy due to the R effect on the hydrogen storage alloy due to impurity components in hydrogen gas and a decrease in the hydrogen storage capacity, The use of storage alloys poses many problems in terms of efficiency, maintenance, and economics in the system. Therefore, it is an important issue to effectively improve these problems.

An object of the present invention is to provide a treatment method that effectively improves various performance degradations of a hydrogen storage alloy due to the effect of 6M6 on the hydrogen storage alloy due to such impurity components in hydrogen gas.

Means to Solve the Problem In order to solve the above-mentioned problem, the present invention provides a method for repeatedly hydrogenating and dehydrogenating a hydrogen storage alloy with crude hydrogen gas having a hydrogen gas purity of 99.9"X or less. After doing so, create a new [9
This is a method for treating a hydrogen storage alloy, characterized in that hydrogenation and dehydrogenation are performed at least once using hydrogen gas having a purity of 9.9% or higher.

Preferably, after hydrogenation is performed using hydrogen gas having a purity of 99.9% or more, the hydrogen storage alloy is heated during dehydrogenation, or the hydrogen gas is forcibly evacuated using a vacuum pump or the like. The method is characterized in that dehydrogenation is carried out by one or both of the following means.

In addition, iJg whose hydrogen storage alloy is mainly composed of Ti and Mn
Zn2 type (C14 type) This is a Laves phase Ti-Mn system combination.

When a hydrogen storage alloy is hydrogenated using hydrogen gas, the performance of the hydrogen storage alloy varies greatly depending on the amount of impurities in the hydrogen gas used for hydrogenation.

When carrying out hydrogenation with extremely high purity hydrogen gas, the hydrogen storage capacity of the hydrogen storage alloy and the hydrogenation reaction rate are good, but in the present invention, when the hydrogen gas purity is 99. When hydrogenation is carried out using hydrogen gas, impure components in the hydrogen gas act on the hydrogen storage alloy, resulting in the aforementioned deterioration in performance. In this case, the performance decrease is due to impurity component 4
′! It has a close relationship with the rt term and its quantity.

The impurity components in the hydrogen gas are adsorbed onto the surface of the hydrogen storage alloy during the hydrogenation reaction of the hydrogen storage alloy, resulting in a lower temperature during the first stage. Therefore, in order to restore performance, it is important to remove impurity components other than hydrogen gas adsorbed on the alloy surface.

While studying the behavior of these impurity components in hydrogen storage alloys, the present inventors determined that the state in which impurity components were adsorbed on the alloy surface using I'lt crude hydrogen gas, etc., was determined to be an adsorbent with good initial performance. It has been confirmed that the treatment method according to the present invention is effective in achieving a state where there is almost no oxidation.

An important finding in the present invention is that (1) impurity components adsorbed on the surface of the 0 alloy can be considerably removed by a dehydrogenation reaction. (2) The hydrogenation reaction in the regeneration tank will be more effective if it is carried out with hydrogen gas having a purity of 99.9 or higher. ■It is more effective to carry out the hydrogenation reaction by heating the hydrogen storage alloy at the cutting edge, or by forcibly discharging hydrogen gas, or both. . ■Hydrogen storage alloy is a poem of Ti
Mgzn2 type La va s phase T whose main components are
In the case of an i-Mn alloy, the effects of (1) to (3) are even higher. There are four points. These findings are important points in removing adsorbed impurity components from the surface of hydrogen storage alloys.

Example Next, examples of the present invention will be shown.

(Example 1) As a hydrogen storage alloy, Ti from among Ti-Mn alloys was used.
Mn1. ,, Tio8Zro2Mno, 80r4. .

A total of four alloys were selected: Cuo, 2, TiFe2.9"0.1 from the Ti-Fe alloys, and LaNi5 from the rare earth alloys. Place the ingredients in step 1 into a cylindrical stainless steel reaction vessel.
Hydrogenation and dehydrogenation were performed using hydrogen gas above 99.9 and crude hydrogen gas below 9 sH, and the performance as a hydrogen storage alloy was evaluated. These four types of alloys were created using the high frequency melting method or the argon mark melting method, and were made using hydrogen gas with a purity of 99.9% or higher.
Initial hydrogenation and dehydrogenation reactions from ``S- to 10% (~ is a cycle) indicate that normal hydrogen equilibrium pressure Kerr composition - isomixture (P-C-T ) Confirmed by measuring properties.

Using this as an example of crude hydrogen gas having a hydrogen purity of 999% or less, hydrogenation and dehydrogenation were repeated from 11 to 15 using crude hydrogen gas having the gas composition shown in Table 1.

Table 1 Composition of the crude hydrogen gas used Then, 16 to 20% of the hydrogen gas was hydrogenated again using hydrogen gas having a purity of 99.9π or higher, and hydrogenation was repeated once again.

The evaluation under these conditions was conducted at a constant temperature of 20'C, at a maximum pressure of 9/crA of hydrogen gas, and at each cycle (~), the performance was measured by measuring the hydrogenation characteristics.

Among the above evaluation studies, the case of TiMn, 5 will be explained as a representative example.

(The following is a blank space) Table 2 shows the results of the evaluation study of the TiMn 1.5 alloy. Figure 1 also shows the relationship between hydrogenation reaction time and hydrogen storage capacity per alloy 12 for 5%, 15'%, and 1 (3), which are performance points from the results in Table 2. This is what I did.

As is clear from Table 2 and Figure 1, TiMn +,
Alloy No. 5 can absorb hydrogen by hydrogenating it with the crude hydrogen gas shown in Table 1 from No. 11 to No. 16.

The amount of hydrogen released has drastically decreased, and the time required for hydrogenation to reach saturation has increased by a large margin. For example, 5-=
The performance ratio Ik312 between - and 11~ shows that 11~ is the hydrogen storage amount, which is about 27% lower, and the hydrogenation time is 75 times or more, which is a performance drop. If it were to be used in the conventional manner, the performance of 11 to 16 would continue to be used from then on, but in the present invention, it is possible to change the performance from 1θ to 2.
The performance of the TiMn,5 alloy is
It can be seen that the performance of the hydrogen storage alloy and reaction rate is improved to that before hydrogenation with hydrogen gas (11~) (1~1 ob).

In addition, similarly evaluated Ti o, B Zro2Mno
8Cr.

It was confirmed that the results were almost the same for the Cu o22 alloy and the TiMnt55 alloy.

It's a trench, Ti Fe o, p ff1no,, alloy,
It was found that the LaNi5 alloy exhibits almost the same behavior as the TiMn5 alloy. therefore,
It was expected that many alloys known as hydrogen storage alloys would also have the effect of the present invention.

However, TiFe o, , Mno, + alloy,
Both LaNi5 alloys are inferior to the previous two Ti-Mn alloys when evaluated in terms of hydrogen storage capacity and reaction rate.
It was found that Ti--Mn based alloy is the most effective.

(Example 2) This example was studied using almost the same method as the previous actual gun example, but the difference from the previous actual gun example is the crude hydrogen gas term. The composition of the crude hydrogen gas used in this example was as shown in Table 3 below.

(Left space below) Table 3 Composition of crude hydrogen gas used in the second example Using these nine types of crude hydrogen gas, performance was evaluated focusing on TiMn and 5 alloy. Figure 2 shows representative results of the crude hydrogen gas A, B, C:, D shown in Table 3.
This figure shows the relationship between the hydrogen storage amount ()l and the N2 gas concentration when a TiMnt t55 alloy is hydrogenated using a seed gas. Similarly, in Figure 2, after that, from crude hydrogen gas 9
The hydrogen storage amount (Y) in the case of hydrogenation by switching to high-purity hydrogen gas with a purity of 9.9 or higher is also shown as a comparative example of the effect of the present invention. Figure 2 shows that when the N2 gas concentration in the hydrogen gas becomes poor, the hydrogen storage capacity decreases in proportion to the N2 gas concentration, but when hydrogen is re-hydrogenated with high-purity hydrogen, the negative effects of the crude hydrogen gas are eliminated. , the performance was recovered to approximately 100-97 of the initial gU performance. In this case,
, Y are all shown in relative amounts, with the initial performance in high-purity hydrogen being 100.

Although FIG. 2 shows the effect on the amount of hydrogen storage, recovery using high-purity hydrogen gas also showed similar results on the reaction speed.

In addition, Go such as g, F, (zH, I, etc. in Table 3).

It was confirmed that the same tendency as in the case of N2 shown in FIG. 2 was observed in the case of CO2 and crude hydrogen gas made from a mixture thereof.

(Example 3) This example was investigated using the same method as the first and second examples, but the difference from these examples is that hydrogen having a purity of 99.9π or more was used. When hydrogenation is performed using gas and then dehydrogenation is performed, the hydrogen storage alloy is heated by means of heating, or by means of a vacuum pump, etc.
Dehydrogenation is carried out by one or both of the methods of exhausting hydrogen gas.

In the previous examples, dehydrogenation was performed using the pressure characteristics of a hydrogen storage alloy at a predetermined temperature. When proceeding with dehydrogenation, the treatment time for dehydrogenation was shortened and the poisoning effect caused by impurities in the crude hydrogen gas was more effectively recovered. For example, it was confirmed that by heating a cylindrical stainless steel container containing a hydrogen storage alloy to about 100 to soo'c using an external heater, the Y value shown in FIG. 2 becomes even closer to 100%.

Furthermore, similar results were obtained by opening the inside of the stainless steel reaction vessel to a vacuum of around 10-1 to 10-' Torr using a vacuum pump instead of the heating means. Furthermore, it was natural that using both heating and vacuum evacuation methods would be even more effective.

It is thought that these external forced dehydrogenation treatment methods are due to the fact that impurity components in the crude hydrogen gas adsorbed on the alloy surface are more easily desorbed.

In addition, it was confirmed that the method of dehydrogenating the hydrogenated product using crude hydrogen gas under these forced external temperature and pressure conditions is also quite effective. However, if heating is performed with more impurity components adsorbed, the performance of the hydrogen storage alloy may deteriorate depending on the column head of the crude hydrogen gas, so care must be taken in this case. It was necessary.

Furthermore, the hydrogen purity used in the present invention is closely related to the effects of the present invention, and fresh hydrogen gas purity after using crude hydrogen gas is good if it is 99.9 or higher.
In the case of 9 koto or less, the hydrogen storage capacity and reaction rate were not sufficient.

Effects of the Invention As described above, by adopting the hydrogen storage alloy treatment method of the present invention, the hydrogen storage performance and reaction rate can be improved by using crude hydrogen gas having a hydrogen purity of 99.9 or less. Even in a degraded state, it is possible to restore the initial excellent performance again. The method of the present invention can restore such abilities in an extremely simple manner.
Can be effectively turned blue.

Therefore, the method of the present invention can be applied to many fields that utilize hydrogen storage alloys, mainly in the field of separating and refining hydrogen gas from crude hydrogen gas, and can extend the lifespan of hydrogen storage alloys and improve economic efficiency. It is beneficial in this respect.

[Brief explanation of drawings]

Figure 1 shows each hydrogenation cycle (
Fig. 2 shows the relationship between the N2 concentration of the N2-containing crude hydrogen gas and the hydrogen storage capacity in another embodiment of the present invention. FIG. 3 is a diagram in which X represents the relationship between the amount of hydrogen absorbed by the subsequent high-purity hydrogen gas and Y represents the relationship between the amount of hydrogen absorbed and the subsequent high-purity hydrogen gas. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure, U°-+ (High 67-shi 2-rep knit-height n' included) □

Claims (3)

[Claims] (1) After repeatedly hydrogenating and dehydrogenating the hydrogen storage alloy using crude hydrogen gas with a hydrogen gas purity of 99.9% or less, using hydrogen gas with a purity of 99.9% or more A method for treating a hydrogen storage alloy, characterized by carrying out at least one hydrogenation and one dehydrogenation. (2) After hydrogenation with hydrogen gas having a purity of 99.9% or more, either heating the hydrogen storage alloy or forcibly exhausting the hydrogen gas with a vacuum pump, etc., or A method for treating a hydrogen storage alloy according to claim 1, characterized in that dehydrogenation is carried out by both means. (3) MgZ hydrogen storage alloy whose main components are Ti and Mn
3. The method for treating a hydrogen storage alloy according to claim 1 or 2, wherein the hydrogen storage alloy is an n_2 type Laves phase and a Ti-Mn alloy.