JPH068161B2 - How to absorb hydrogen gas - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for absorbing hydrogen gas by a hydrogen storage alloy, and is particularly advantageously applied to absorbing hydrogen in purge gas of a chemical plant or by-product gas of a steel mill. Regarding the same method.

[Prior Art] Conventional hydrogen storage alloy is filled with its powder in a container, and a gas containing hydrogen is pressed into this container to collect hydrogen in the form of metal hydride, and to release hydrogen, the container is used. When it is heated to decompose the metal hydride, it is used in various usage forms.
The present inventors also proposed on the same day a new form of a slurry form in which a hydrogen storage alloy is suspended in a solvent in order to solve the drawbacks of the powder filling method.

[Problems to be solved by the invention]

 Such a powder filling method has the following drawbacks.

(1) The hydrogen storage alloy is a clean metal reduced with hydrogen, so that it can be used as an impurity gas that coexists with hydrogen, such as CO or C
_{O 2, NH 3, N 2} , H 2 O, H 2 S, to react with O _2, metal carbonyl, carbonate, nitride, hydroxide, sulfide, deteriorates rapidly and form oxides.

(2) Since it is a fixed bed, it is necessary to release hydrogen and regenerate the alloy after absorbing hydrogen, which makes continuous treatment of feed gas difficult.

(3) When the alloy absorbs hydrogen and changes to a metal hydride, its thermal conductivity is extremely reduced, so that the heat conduction when heating and releasing hydrogen is poor. That is, the hydrogen release time is long.

(4) The alloy absorbs hydrogen and expands when it changes to a metal hydride, which may cause deformation or damage of the container.

(5) A filler is installed at the gas inlet / outlet of the container because the filled fine powder accompanies it when releasing hydrogen, but troubles occur due to clogging of the filter.

(6) Further, by the method proposed on the same day, that is, by using a slurry state, deterioration due to N ₂ , NH ₃ , CO ₂ , O ₂ , and H ₂ O can be prevented as will be apparent from Experimental Example 4 and Comparative Example 3 described later. However, it has been found that even in the slurry state, the poisoning durability is not improved with respect to carbon monoxide, hydrogen sulfide, and sulfur compounds such as sulfur oxides.

[Means for solving problems]

The present invention provides a slurry in which a hydrogen storage alloy is suspended in a solvent selected from the group consisting of saturated hydrocarbons composed only of carbon and hydrogen, aromatic hydrocarbons and alicyclic saturated hydrocarbons, and a gas containing hydrogen. In the method of contacting and absorbing hydrogen gas, carbon monoxide and / or sulfur compounds in the gas are
It is a method of absorbing hydrogen gas, which is characterized in that the hydrogen gas is removed before the contact with the slurry.

In the present invention, the hydrogen storage alloy powder is suspended in a solvent and used as a slurry. The solvent cannot react with the alloy, and an organic solvent can be used, but is limited to a saturated hydrocarbon composed of carbon and hydrogen, an aromatic hydrocarbon, and an alicyclic saturated hydrocarbon in the organic solvent. .

The saturated hydrocarbons, aromatic hydrocarbons and alicyclic saturated hydrocarbons used in the present invention are at least about 100 ° C. in order to release hydrogen by heating and utilize heat generated during hydrogen storage.
A liquid having the above boiling point and being liquid at room temperature is used. Examples of these are given below.

Saturated hydrocarbon Example: n-heptane, 2-methylhexane, 3-methylhexane, 3-ethylpentane, 2,2-dimethylpentane, 2,3-dimethylpentane, 2,4-dimethylpentane, 3,3-dimethyl Pentane, 2,2,3-trimethylbutane, n-octane, 2-methylheptane, 3-methylheptane, 4-methylheptane, 3-ethylhexane, 2,
2-dimethylhexane, 2,3-dimethylhexane, 2,4
-Dimethylhexane, 2,5-dimethylhexane, 3,3-
Dimethylhexane, 3,4-dimethylhexane, 2-methyl-3 ethylpentane, 3-methyl-3 ethylpentane, 2,2,3-trimethylpentane, 2,2,4-trimethylpentane, 2,2,3- Trimethylpentane, 2,3,4-trimethylpentane, 2,2,3,3-tetramethylbutane, n-
Nonane, n-decane, n-undecane, n-dodecane,
Aromatic hydrocarbons such as n-tridecane Examples: methylbenzene, ethylberethene, 1,2-dimethylbenzene, 1,3-dimethylbenzene, 1,4-dimethylbenzene, n-propylbenzene, i-propylbenzene, 1-methyl- 2-ethylbenzene, 1-methyl-3
-Ethylbenzene, 1-methyl-4-ethylbenzene,
1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, 1,2,5-trimethylbenzene, n-butylbenzene, n-pentylbenzene, n-hexylbenzene, n
-Heptylbenzene, n-octylbenzene, n-nonylbenzene, n-decylbenzene, etc. Alicyclic saturated hydrocarbon Examples: ethylcyclopentane, n-propylcyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane, p-propylcyclohexane, etc. Furthermore, since the durability against poisoning against CO, H ₂ S, and SOx is not improved, it is necessary to remove CO, H ₂ S, and SOx from the hydrogen gas before contacting the slurry with hydrogen gas containing these impurities. did.

[Action]

(1) Since the surface of the alloy is covered with a solvent, C is also highly toxic.
Since O, H ₂ S, and SOx are removed in the previous stage, the poisoning of the alloy by the impurity gas is reduced.

(2) Pumping is possible and the regeneration process can be separated in the absorption process, allowing continuous absorption and regeneration.

(3) The solvent serves as a heat medium to improve heat conduction.

(4) There is no obstacle due to expansion of alloy or scattering.

Hereinafter, examples of the present invention will be described in more detail.

Experimental Example 1 33.1 g of LaNi ₅ was sampled in a container, and 7N (seven nines: 99.99999%) hydrogen was press-fitted to 16 atm, and hydrogen was stored at room temperature. After that, the gas outlet valve was opened, and the container was heated to 80 ° C. to release hydrogen gas. This operation was repeated several times to complete the activation treatment of LaNi ₅ .

Next, the gas outlet of the container was connected to an aspirator, and 298 g of normal heptane was sucked into the container from the gas inlet of the container to prepare a 10 wt% slurry of LaNi ₅ . The stirrer was started, and hydrogen was stored in the LaNi ₅ / normal heptane slurry at a hydrogen pressure of 16 atm and room temperature. As shown in Fig. 1, La
The hydrogen storage performance was almost the same as that of the Ni ₅ alloy.

Experimental Example 2 In the same manner as in Experimental Example 1, the solvent was replaced with propylbenzene to occlude hydrogen. The results are shown in Fig. 1. It has been found that the hydrogen storage performance is almost the same as that of the alloy.

Experimental Example 3 In the same manner as in Experimental Example 1, hydrogen was occluded by changing the solvent to n-propylcyclohexane. The results are shown in Fig. 1. It was found that the hydrogen storage performance was similar to that of the alloy.

Comparative Example 1 Tetradecene {CH ₃ (CH ₂ ) ₁₁ CH = CH ₂ } was used as a solvent, and hydrogen absorption by the slurry was tested in the same manner as in Experimental Example 1. As shown in FIG. It occluded about 7 times more hydrogen. After the test, the solvent is tetradecane {CH
₃ (CH ₂ ) ₁₂ · CH ₃ }. It is clear that the olefin hydrocarbons undergo a hydrogenation reaction due to the catalytic action of LaNi ₅ and change to saturated hydrocarbons.

Comparative Example 2 The results when methylene iodide was used as the solvent are shown in FIG. The hydrogen was stored for a long time, and the storage amount reached 80% of that of the alloy alone. It is clear that the alloy itself is poisoned by the solvent.

Experimental Example 4 LaNi ₅ / normal heptane 10 wt% slurry was prepared in the same manner as in Experimental Example 1, and hydrogen storage performance was tested in the same manner as in Experimental Example 1 using hydrogen gas having an impurity concentration shown in Table 1.

Time to reach 80% of storage capacity with 7N hydrogen (T ₈₀ ).
The time is set to 1 for each 7N hydrogen, and the
Shown in the table.

Comparative Example 3 LaNi ₅ was activated in the same manner as in Experimental Example 1, and hydrogen storage performance was tested using hydrogen gas containing impurities shown in Table 1. The results are shown in Table 2.

From the above experimental examples, it was found that CO, H ₂ S, and SOx must be removed in advance in the slurry as well.

Example 1 10% by weight of LaNi ₅ / propylbenzene in the embodiment shown in FIG.
The slurry was used to absorb and desorb hydrogen gas. In FIG. 3, reference numeral 1 denotes a gas-liquid contactor, which supplies gas having the composition shown in Table 3 from the line (a) through the pretreatment device 2 after removing CO, SOx, and H ₂ S, and stirring by the stirrer 3. It was contacted with the LaNi ₅ slurry which is being used. The residual gas was exhausted from the line (b). The pressure in the gas-liquid contactor 1 was 16 atm, and cooling water was supplied from the line (c) and discharged from the line (d) to control the temperature at 20 ° C. The slurry in the gas-liquid contactor 1 was continuously extracted from the line (e), the pressure was reduced from 16 atm to 1 atm, and the regenerator 4 was supplied. Steam line for playback device 4
It was supplied from (f) and discharged from the line (g) to control the temperature at 80 ° C. Hydrogen gas generated in the regenerator 4 was extracted from the line (h) via the cooler 5. The slurry in the regenerator 4 was continuously extracted by the pump 6 and pressure-fed to the gas-liquid contactor 1 via the cooler 5 via the line (2).

The amount of gas supplied from the line (a) was 4 l / min, and the residence time of the slurry was 10 minutes. It was found that the amount of hydrogen released from the line (h) was 2.2 l / min, and almost all of the supplied hydrogen was recovered.

In the pretreatment apparatus 2, first, steam was introduced into the supply gas, and CO + H ₂ O was passed through the CO shift catalyst layer at 400 ° C.
→ CO ₂ + H ₂ reaction converts CO to CO ₂ and then 400
H ₂ S was adsorbed and removed through an iron-based adsorbent layer mainly composed of Fe ₃ O ₄ maintained at ℃. After that, the gas was cooled to room temperature and supplied to the gas-liquid contactor 1.

Example 2 In the same manner as in Example 1, hydrogen gas was absorbed and desorbed by using a 10 wt% slurry of LaNi ₅ / n-propylcyclohexane. The amount of hydrogen released from the line (chi) was 2.2 l / min, and the same result as in Example 1 was obtained.

〔The invention's effect〕

Slurry the hydrogen storage alloy and prepare CO, H ₂ S, SOx in advance.
By absorbing the hydrogen by bringing it into contact with a gas containing hydrogen from which (1) the alloy powder has been removed, it is possible to prevent the alloy powder from scattering. (2) Mobility is added. (3) The durability of the alloy against impurity gas is improved. (4) The thermal conductivity is improved. (Five)
There are no obstacles due to expansion or contraction of the alloy. Therefore, the conventional drawbacks can be solved and a continuous hydrogen recovery method becomes possible.

[Brief description of drawings]

FIG. 1 is a chart showing hydrogen absorption of LaNi ₅ slurry as an experimental example of the present invention, and FIG. 2 is LaNi ₅ as a comparative example of the present invention.
₅ A diagram showing hydrogen absorption of the slurry, and FIG. 3 is a diagram showing a hydrogen recovery flow as an example of the present invention.

Claims (1)

[Claims] 1. A gas containing hydrogen and a slurry in which a hydrogen storage alloy is suspended in a solvent selected from the group consisting of saturated hydrocarbons composed only of carbon and hydrogen, aromatic hydrocarbons and alicyclic saturated hydrocarbons. In the method for absorbing hydrogen gas by contacting with hydrogen gas, the method for absorbing hydrogen gas, comprising removing carbon monoxide and / or sulfur compounds in the gas before the contact with the slurry.