JPS61122103A - Recovery of hydrogen from low pressure mixed gas containing hydrogen - Google Patents

Abstract

PURPOSE:To recover hydrogen gas under low pressure or medium pressure from a low-pressure mixed gas containing hydrogen, by introducing the low- pressure mixed gas into a container filled with a hydrogen-occlusion alloy, occluding the hydrogen as a metal hydride, releasing the remaining mixed gas from the container, and repeating the above processes. CONSTITUTION:A mixed gas containing hydrogen is introduced into a container filled with a hydrogen-occlusion alloy having an equilibrium hydrogen-occlusion pressure of about several atm, while keeping the alloy to a temperature (about 20 deg.C) to lower the equilibrium pressure below the atmospheric pressure. The mixed gas having lowered hydrogen concentration in the container is purged to a pressure near the equilibrium hydrogen occlusion pressure of the alloy. A fresh mixed gas is introduced into the container, and the occlusion of hydrogen and the purge of the remaining mixed gas are repeated. The introduction of the fresh mixed gas and the discharge of the mixed gas having decreased hydrogen concentration can be carried out simultaneously and continuously, by opening the gas outlet for purging in the introduction of the mixed gas into the container.

Description

Detailed Description of the Invention [Industrial Application Field 1] The present invention is a method for separating and recovering hydrogen from a low-pressure hydrogen mixed gas consisting of hydrogen and other gases (nitrogen, hydrocarbons, ammonia, etc.) using a hydrogen storage alloy. Regarding how to.

[Prior art 1] Large amounts of hydrogen gas are used in the chemical industry, electronic industry, etc. Particularly in semiconductor factories, a large amount of high-purity gas is used as an atmospheric gas for silicon. In each step, hydrogen is replaced with an inert gas such as nitrogen, so the used hydrogen is released in a state mixed with an inert gas such as nitrogen. Further, in chemical plants and the like, hydrogen gas may be generated as a byproduct, and these gases are released as a mixture with gases such as hydrocarbons and ammonia. Most of these mixed gases are discarded into the atmosphere as factory exhaust. However, releasing hydrogen gas into the atmosphere wastes resources and is uneconomical, and depending on the hydrogen concentration, there is a risk of explosion.

[Problems to be Solved by the Invention] Conventional methods for separating hydrogen gas from a mixed gas containing hydrogen include upstream membrane separation method, pressure cycle adsorption purification method, and cyrogenic method. Treat factory exhaust 1! ! It is inappropriate and economically impractical to implement this as a large-scale facility. In some cases, hydrogen cannot be easily recovered at low pressures because the diluent gas prevents hydrogen storage. However, there is a strong desire to recover such dilute hydrogen from a gas mixture.

The present invention aims to solve the above-mentioned problems and recover hydrogen from a mixed gas of nitrogen, hydrocarbon, or ammonia and hydrogen at low pressure or medium pressure.

[Means for Solving the Problems] That is, the present invention introduces a low-pressure mixed gas containing hydrogen into a container filled with a hydrogen storage alloy, and transfers the hydrogen in the mixed gas to the hydrogen storage alloy as a metal hydride. After occlusion, the mixed gas in the container is released to a pressure near the hydrogen storage equilibrium pressure, and then a new mixed gas is introduced into the container again, and hydrogen storage and mixed gas release are repeated. This is a method for recovering hydrogen from low-pressure hydrogen mixed gas.

[Function 1: Hydrogen storage alloys have the property of selectively absorbing hydrogen, and at low temperatures they absorb a large amount of hydrogen and at the same time generate heat.

When a hydrogen storage alloy is heated to high temperatures, it releases hydrogen and takes away heat. In other words, since the hydrogen storage alloy stores hydrogen at a pressure higher than the hydrogen storage equilibrium pressure corresponding to the hydrogen partial pressure in the mixed gas at a given temperature, either the hydrogen pressure is set to be higher than the hydrogen storage equilibrium pressure, or the hydrogen storage alloy By maintaining the temperature of the hydrogen storage alloy so that the equilibrium pressure of the hydrogen gas is lower than the pressure of the hydrogen gas to be recovered, hydrogen in the mixed gas can be separated and recovered as a metal hydride.

To carry out the present invention, first, a mixed gas containing hydrogen is introduced into a container filled with a hydrogen storage alloy. At this time, the alloy may rise to a predetermined temperature or higher due to an exothermic reaction, and in this case, the subsequent reaction between hydrogen and the alloy is suppressed. Therefore, in order to accelerate the reaction, it is necessary to maintain the temperature below a certain level, and in some cases, water cooling is performed.Hydrogen is transferred to the hydrogen storage alloy, but components such as nitrogen remain in a gaseous state, and hydrogen It exists as 11 molecules (atoms) of the storage alloy.

Next, this mixed gas with reduced hydrogen concentration is released (parts) from the container.At this time, a considerable amount of adsorbed molecules (atoms) other than hydrogen are initially desorbed and released, so they are released. However, the hydrogen concentration in the human body gradually increases with the time of release.

Parking is performed to a pressure close to the hydrogen storage equilibrium pressure of the hydrogen storage alloy.

After paring the mixed gas from the container, a new mixed gas is introduced into the container again to cause the hydrogen storage alloy to store hydrogen. Next, by repeating the introduction-parking operation of one or more mixed gases in which the mixed gas with reduced hydrogen concentration is removed from the container, the hydrogen in the mixed γ gas can be recovered as a metal hydride.

When the raw material mixed gas concentration is low, hydrogen is stored in the hydrogen storage alloy and the 1)-1 hydrogen partial pressure is lowered, so even if the hydrogen storage alloy is held below a predetermined temperature, the interaction between hydrogen and the alloy is low. The reaction rate slows down, and a large amount of mixed gas other than hydrogen adsorbs on the alloy surface, which inhibits the reaction between hydrogen and the alloy. However, by repeating the above operation several times, it is possible to recover hydrogen. That is, as shown in Fig. 2, the introduction of mixed gas
By repeating step 7, 1. It can be seen that the hydrogen amount it increases.

Furthermore, when introducing the mixed gas into the container, the gas outlet for the Spano gas may be opened, and the introduction of the mixed gas and the discharge of the mixed gas with a reduced amount of hydrogen may be carried out simultaneously and continuously.

Furthermore, if the hydrogen concentration in the mixed gas is to be further reduced, it is possible to recover most of the hydrogen in the mixed gas by introducing it into a container filled with a hydrogen storage alloy that has a low hydrogen absorption equilibrium pressure. .

When reusing hydrogen recovered in this way,
Hydrogen can be released by heating the hydrogen storage alloy inside the container.

In the present invention, any hydrogen storage alloy having a hydrogen storage equilibrium pressure of several atmospheres can be used.

The present invention will be explained below based on Examples.

[Example] In a small test container (made of SO3304, sample chamber volume: 2.7 cc) shown in Fig. 1, Ca-N was added as a hydrogen storage alloy.
A hydrogen gas absorption test was conducted using a mixed gas of hydrogen and nitrogen with hydrogen concentrations of 100%, 90%, 70%, and 50%, respectively, filled with 6 g of 1-M++-AI alloy.

That is, the above hydrogen storage alloy is maintained at a temperature (20°C) at which the equilibrium pressure is below atmospheric pressure, and a mixed gas of hydrogen and nitrogen of each composition is introduced into the test container.Then, the hydrogen concentration in the test container is reduced. Next, a new mixed gas was introduced into the test vessel again, and the hydrogen storage and parts operations were repeated.

Figure FA2 shows the changes in hydrogen storage, the number of repetitions when parts are repeated, and the amount of hydrogen absorbed.From the figure, it can be seen that by repeating parts, the amount of hydrogen storage increases, and the amount of hydrogen recovered can be increased. It turns out that it is possible.

Similar results can be obtained with a mixed gas of hydrogen and ammonia or a hydrocarbon such as methane.

In order to carry out the above-mentioned operations, the apparatus for carrying out the method of the invention is capable of supplying and discharging gas into a container filled with a hydrogen storage alloy, and also capable of cooling or heating the hydrogen storage alloy. Therefore, any type of equipment is sufficient, and hydrogen can be easily recovered.

[Effect 1 of the Invention According to the present invention, hydrogen can be recovered from a hydrogen mixing gas at low pressure. Furthermore, it is possible to effectively utilize the recovered hydrogen.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a test container used in an example of the present invention;
Figure 2 is a diagram showing the relationship between the number of parts and the amount of hydrogen suction when introducing mixed gas and parts are repeated in an example. In Figure 6, A: main body, B, C: stopper metal fittings. , D... Upper lid, E... Metal filter, F... Sample chamber, G...
Temperature measuring thermocouple, H...stainless steel pipe, 0...0
ring.

Claims (2)

[Claims] (1) A low-pressure mixed gas containing hydrogen is introduced into a container filled with a hydrogen storage alloy, and the hydrogen in the mixed gas is stored as a metal hydride in the hydrogen storage alloy. A method for recovering hydrogen from a low-pressure hydrogen mixed gas, characterized in that the pressure is released to a pressure near the storage equilibrium pressure, and then a new mixed gas is introduced into the container again, and hydrogen storage and mixed gas release are repeated. (2) A method for recovering hydrogen from a low-pressure hydrogen mixed gas according to claim 1, wherein the mixed gas is discharged continuously at the same time as the mixed gas is introduced.