JPH07289853A - Hydrogen gas isotope separation and concentration equipment - Google Patents

Abstract

(57) [Summary] [Purpose] To present an apparatus for inexpensively separating deuterium gas from hydrogen gas using a hydrogen storage alloy. [Composition] In the process of concentrating deuterium in sequence by using multiple hydrogen storage alloys that store light hydrogen and deuterium from hydrogen gas at different pressures, by applying vibration from the outside to the container containing the alloy The alloy is fluidized to eliminate the temperature distribution in the alloy and make it uniform. This has made it possible to virtually eliminate the effect that the deuterium separation coefficient of the alloy changes with temperature.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an apparatus for separating and concentrating deuterium gas from hydrogen gas.

[0002]

Heavy water is widely used in nuclear reactors as a neutron moderator. Heavy water has major advantages over other moderators, such as the ability to reduce the amount of nuclear fuel inside and the use of not only enriched uranium but also natural uranium, but its use was limited because it was expensive. It is expected that the use of heavy water will expand as the research on cold fusion progresses further in the future, and inexpensive heavy water supply is demanded.

Conventionally, the following methods are known as methods for producing heavy water. Compared to the electrolysis method H ₂ O, D ₂ O requires a higher voltage during electrolysis,
Therefore, D _{2 in the} water remaining in the tank due to the electrolysis of water
The concentration of O increases. Utilizing this effect, D ₂ O is concentrated and D ₂ is produced therefrom. Distillation process D ₂ O and HDO water by utilizing the fact that is slightly less vapor pressure than _{H 2} O, _{D 2} O and HDO by repeated distillation
To separate. Liquid hydrogen distillation method In liquid hydrogen, since D ₂ and H ₂ have different vapor pressures, they are separated from liquid hydrogen by distillation to produce D ₂ . Method by chemical reaction In the exchange reaction of H ₂ O + HD = HDO + H ₂ , HDO is obtained by utilizing the fact that the equilibrium constant is different depending on the temperature. Similar exchange reactions such as H ₂ O + HDS = HDO + H ₂ S are also used. Thermal Diffusion Method A heating wire with a temperature of 1000 ° C. is vertically provided at the center of the separation column, and convection is generated in the raw hydrogen gas by cooling the wall of the separation column, and heavy D ₂ is transferred to the bottom of the column for separation. , JP-A-63-205127). Hydrogen storage metal or alloy (hereinafter referred to as "MH")
The method MH has the property of absorbing and releasing hydrogen depending on temperature and pressure, and is therefore used for hydrogen storage, separation and purification, batteries and the like. Since H ₂ and D ₂ have different storage pressure and release pressure to the MH, they are separated by utilizing this property.

However, the above-mentioned prior art has the following problems. In the electrolysis method, since the rate of separation into H ₂ and D ₂ in one stage is small, multi-stage electrolysis is required, and the electric power cost becomes excessive. Therefore, the production was limited to the region where the electric power was inexpensive. The water distillation method is advantageous in that heavy water is directly separated from water, but the amount of energy required for multistage distillation is extremely large, and thus the problem of cost increase is inevitable. The liquid hydrogen distillation method requires a large amount of energy for liquefying hydrogen, and requires low-temperature equipment at -250 ° C, which increases cost. There are problems such as using an expensive platinum catalyst in order to utilize a slight difference in separation coefficient and to accelerate the reaction rate. Although this is a method of utilizing the density difference between H ₂ and D ₂ or HDO, it is difficult to perform gas separation by reducing the turbulence of the air flow inside a long tower. The method using MH is a promising method because it may consume less energy, but this method also uses a slight difference in separation coefficient between H ₂ and D ₂ of a metal or an alloy, and thus accurate control is possible. There is a technically difficult problem because it requires a method and an apparatus.

MH generates heat when hydrogen is occluded, but the separation coefficient of H ₂ and D ₂ of MH changes depending on the temperature. Therefore, if the temperature distribution exists in the MH layer, the result will be significantly different from the target separation capacity. For this reason, the temperature distribution of the MH layer must be as uniform as possible, but in reality, a considerable temperature distribution is generated for the reason described below. That is,
Normally, MH is used in the powder state, but the thermal conductivity in the powder state is as low as 1.0-0.5 Kcal / m, hr, c, which is only a brick-like value. When the raw material hydrogen is absorbed, the entire layer heats up, so it is usual to install a heat exchanger inside to remove this heat.At this time, in order to keep the temperature constant in the layer, the low heat Due to the influence of conductivity, which is difficult, a considerable temperature distribution was generated.

In order to solve this problem, the following two methods have been implemented as countermeasures. (1) A method of increasing the heat transfer area of the heat exchanger,
Specifically, a technique such as using a fin tube heat exchanger is used. As a problem in this case, even if the fin area is too large, the fin tip temperature becomes the same as the surrounding MH temperature, so the effect of widening the area is weakened,
It is pointed out that the so-called fin efficiency decreases. (2) When a powder such as copper or aluminum having a high thermal conductivity is mixed in the MH powder and molded, a molded product having a thermal conductivity about several times that of the MH powder can be obtained. If such a method is used, the above problems can be solved to some extent, but if the molded body is made into a large shape, the temperature difference also becomes large, so the effect is poor unless the shape is small, and there is also the problem of cost increase at the time of molding. I can't ignore it.

Here, a means for keeping the temperature of the alloy layer uniform is required for inexpensive D ₂ separation. The problem of temperature non-uniformity does not occur only when the MH absorbs hydrogen, but the MH itself also causes a temperature drop when hydrogen is released, and thus the same problem of temperature non-uniformity occurs. It is an object of the present invention to provide a hydrogen gas isotope separation / concentration device using a hydrogen storage alloy for separating D ₂ from hydrogen at low cost in a small-scale facility.

[0008]

The present inventors have made it possible to cause MH powder to flow like a liquid by applying mechanical vibration to the MH powder, and at the same time, to form an alloy layer. It has been found that the internal temperature is significantly improved. Therefore, when performing the absorption and separation of hydrogen isotopes, the entire alloy layer can be effectively used without causing a difference in the separation performance of the alloy depending on the location. At the same time, the amount of heat exchanged with the heat exchanger is also remarkably increased by the flow as compared with the stationary state, so that the hydrogen storage-release cycle can be shortened and the productivity can be remarkably enhanced even in the same equipment.

The gist of the present invention is as follows. An apparatus for separating and concentrating hydrogen gas isotopes, characterized by having the following apparatus conditions (a) to (f). (A) A plurality of containers holding hydrogen storage metals or alloys are installed, (b) Each container in (a) above is connected to a hydrogen gas pipe by a valve, and hydrogen gas is first introduced. Pipes and valves for introducing hydrogen gas, which is the raw material, are installed in the container on the inlet side, and the container for introducing hydrogen gas at the end is for introducing hydrogen gas that has been separated and concentrated into another device or container. (C) In addition to the containers (a) and (b), one or a plurality of containers containing a hydrogen storage metal or alloy is installed, and these containers are (a) and (b) are connected to each other by pipes and valves, and (d) the containers (a) and (b) have a heat exchanger built-in and are equipped with a hydrogen storage metal or alloy. It is connected to the pipes for flowing the cold heat medium and the hot heat medium from the outside to change the temperature. (E) All vessels are equipped with pressure detectors, and have a device for controlling the temperature and flow rate of the heat medium flowing into the vessels by the pressure difference between the detected pressure and the set pressure. ) All containers are mounted on a spring that absorbs vibration, and a device that applies vibration in the range of 0.1 G to 10 G is provided.

The present invention will be described in detail below. As shown in FIG. 1, a powder MH is filled in a horizontal cylindrical MH container 1 (inner diameter 100 mm) having a heat exchanger inside, and the M
Vibration motor 2 having the same axial direction as H container 1 (Shinko Denki RV-14B 60Hz, 4P, 200V, 0.1
(kw) was applied and vibrated. The entire device was supported by 4 springs. This device was used to confirm the drop that the alloy layer becomes uniform due to flow, and is not an experiment to actually absorb hydrogen.

Therefore, MH is an inactive FeTi
_The experiment was conducted in an air atmosphere using _1.05 S _0.016 . The vibration was measured using an accelerometer in the vertical direction (X direction), the horizontal right angle direction of the container (Y direction), and the axial direction of the container (Z direction). The MH weighed 10 KG and the motor weight was 18 KG. As the MH container 1, a transparent acrylic container was used for observation. The vibration motor 2 and the vibration exciter are connected by a universal joint 3, and the vibration generated by the vibration exciter is designed not to be transmitted to the motor. The intensity of vibration was adjusted by changing the angle of the pendulum 5 built in the vibration motor. When the vibration acceleration in the X and Y directions was less than 0.1 G, the MH hardly moved, but the alloy layer began to partially move from the stage of exceeding 0.1 G, and at 0.5 G, flow was observed in the entire alloy layer.
Simultaneously with the start of vibration, the internal heat exchanger was filled with hot water at 75 ° C., and changes in the temperature of each part of the MH were examined, and the results shown in FIG. 2 were obtained.

The temperature of each part shown in FIG. 2 indicates the temperature of the thermocouple inserted in the alloy layer, a is the internal heat transfer tube surface temperature, and b, c, d, and e are the heat transfer tube outer surface, respectively. Two
The temperature of the MH powder pair inside is shown at 4, 6 and 8 mm apart. Further, the temperature i indicates the temperature of the inner surface of the container, and h, g, f indicate the temperature of the alloy layer within 2, 4, 6 mm from the inner surface. FIG. 2A shows the MH temperature when no vibration is applied, which is extremely non-uniform, but it is 1.5 G (FIG. 2 (b)) and 2.5 G (FIG. 2 (c)) in the X and Y directions, respectively. )
It is understood that the temperature distribution is remarkably improved when the vibration of about the degree is given.

FIG. 3 shows vibration waveforms in each of the X, Y and Z directions. The vibration values in the X and Y directions are close to a sine waveform. If the vibration value in the Z-axis direction is large, the alloy in the cylindrical container will shift to one side, so it is desirable to suppress it as much as possible, and it is necessary to make it 1/5 or less of X and Y. The vibration in the Z-axis direction as shown in FIG. 3 is sufficiently lower than the vibrations in the X and Y directions, and there is no flow problem. With a strong vibration of 10 G or more, the uniformity of the temperature distribution is further improved, but the effect is saturated and the amount of power consumption is also increased.
This effect is due to the fact that the MH powder flows in the cylindrical cross section of the MH container under the centrifugal force associated with the vibration of the vibration motor, as if the water were heated and boiled to rise, cooling the surroundings. It is similar in appearance to the phenomenon of falling.

In any case, if the vibration acceleration is within the above range, a sufficient flow condition and accompanying uniformity of temperature distribution can be obtained, and the original purpose can be achieved. This measurement was made by placing a cylindrical container horizontally,
Even when placed in the same horizontal direction, if the direction of vibration is different from that in FIG. 1, sufficient flow does not occur. Further, even in the case of a container having the same shape, a preferable fluidized state cannot be obtained when the container is lifted diagonally from the horizontal or when it is stood vertically.

Next, the separating and concentrating apparatus of the present invention will be described based on the example shown in FIG. Containers I, II, III and IV filled with 300, 150, 75 and 37 kg of vanadium as MH were prepared. The reason for preparing a plurality of containers (I to IV) is that the raw material hydrogen gas is divided into a plurality of stages and sequentially separated and purified to increase the concentration of D ₂ . That is, deuterium and hydrogen have very similar properties, and both can be metal hydrides, but deuterium has a large volume because it has neutrons. Therefore, the distance between deuterium and metal atoms in the metal crystal lattice is smaller than that in the case of hydrogen, and the stability in deuterium and hydride is slightly different in the metal crystal. Also, because the dissociation pressure is different, a so-called isotope effect occurs.

The present invention utilizes this difference in dissociation pressure to separate hydrogen and deuterium, but the difference in dissociation pressure is slight, and if there is some temperature distribution in the MH layer, the In reality, the separation is impossible because the difference in dissociation pressure due to the difference is larger.

In the present invention, the temperature distribution of MH is made uniform by the vibration from the outside so that the separation can be carried out efficiently. However, the separation is not sufficient with only one stage, and the degree of deuterium concentration is small. , MH devices must be connected in series in multiple stages to sequentially increase the concentration of deuterium. The number of stages of the MH container varies depending on the target deuterium concentration, and is not limited to four stages.

It is possible to mount one MH container on the vibration device one by one, but when vibrating, it is preferable to have two containers and install the vibration device at the center, because it is preferable in terms of balance and regular vibration is obtained. Therefore, in the embodiment, two containers are grouped into containers I, II, III and IV in the embodiment. Between the respective containers (I to IV), hydrogen pipes (flexible hoses) and valves are connected in order to sequentially separate and purify hydrogen. A hydrogen gas introduction pipe as a raw material and a valve are installed in the container I, and a pipe for introducing the hydrogen gas (containing a large amount of D ₂ ) after the separation process into another device or a container is installed in the final container IV. is doing.

Vanadium is used as the MH because it absorbs a large amount of hydrogen in the temperature range of room temperature to 100 ° C.
_This is because the selective storage properties of ₂ and D ₂ are relatively excellent.
The ability to separate light hydrogen and deuterium is usually determined by the separation factor α =
It is represented by (D / H) solid / (D / H) gas.
Here, solid represents MH, and gas represents a hydrogen atmosphere around MH.

J. J. Reilly (Zeit.fur
Physik. Chem. , 117, 655 (197)
9)), V shows a value of 1.70 or more at 28.0 ° C., 1.05 (27.6 ° C.) of Zr, and 1. of LaNi.
12 (27.7 ° C.), which is a good value compared to 1.37 (40 ° C.) of TiMn. Vanadium is crushed to 50 mesh or less (0.3 mm or less), and all openings (not shown) are sealed with a stopper so that hydrogen does not leak.

The reason why the weight of vanadium is reduced toward the downstream of the containers I to IV is as follows. The ratio between the amount of hydrogen introduced in each container and the amount of hydrogen stored in vanadium (wherein D ₂ is concentrated) is about 1: 0.
The stored hydrogen is MH in the next step.
Is discharged from the container and sent to the next container.
The amount of H will be half. Each container may be made of ordinary steel as long as it is designed to withstand a predetermined pressure made of SUS304. In addition, a SUS sintered alloy filter is installed in the hydrogen outlet pipe of each container in order to prevent the MH powder from being scattered and mixed in the lower step when hydrogen is released.

In addition to the containers I to IV, one or a plurality of containers X containing MH are held. This container X
Is connected to the containers I to IV by pipes and valves, and I, II
In each of the containers IV to IV, it has a function of sending hydrogen gas having a low D ₂ to be left in the space of the container to the container and storing it by using the internal MH. The MH of the container X may be an MH that is generally used because it does not require the function of separating H ₂ and D _2, and an inexpensive titanium-iron-based MH was used here. Instead of the MH container X, it is also possible to use an ordinary cylinder-shaped container or a spherical container. However, it is industrially advantageous to use the MH container to occlude the residual hydrogen because the purpose can be achieved with a much smaller facility.

A heat exchanger is installed in each container, and the gap between the heat exchangers is filled with MH powder. M
The heat exchanger installed in the H container has two purposes. One is that when the internal MH absorbs hydrogen, it generates heat of absorption and the alloy temperature rises. In order to prevent this, the purpose of this is to flow a cooling heat medium into the heat exchanger to cool the alloy so that hydrogen can be absorbed quickly. Another purpose is that when the stored hydrogen is released and sent to the downstream container, the MH is cooled due to the released heat and the hydrogen release is stopped as it is. In order to prevent this, it is necessary to flow a heating medium to warm the MH and accelerate hydrogen release.

The above-mentioned internal pressure detection device is installed in each container, and if the internal hydrogen pressure rises and approaches the container pressure resistance (less than 10 kg / cm ^{2 in} this case), the heat medium flow rate is controlled. As a result, excessive pressure rise can be prevented, and the automatic operation of the entire device becomes possible.

[0025]

EXAMPLES The present invention will be described below with reference to examples. Container I filled with 300 kg of vanadium as MH for separating raw material hydrogen into H ₂ and D ₂ , container I filled with 150 kg
I, a container III filled with 75 kg, and a container IV filled with 37 kg were prepared, and the container was aligned on the longitudinal direction and fixed on a table. Then, the whole container was fixed on a device that vibrates between 0.5G and 10G by a vibration motor having a rotation axis in the same direction as the container longitudinal direction. The entire device rests on a concrete foundation via a spring 6. Each container has a built-in fin-tube heat exchanger in which cooling water or hot water is passed so as to keep the MH temperature constant. Table 1 shows the operating conditions of each MH container.

[0026]

[Table 1]

Each container is provided with a sintered alloy filter inside and the next container (I
→ II → III → IV) is installed with a hydrogen pipe, and in this order, hydrogen enriched with D ₂ is designed to flow according to the pressure difference. As shown in FIG. 4, containers I, II, III
Although the IV and IV are designed to be vibrated by different excitation motors, the same effect can be expected even when all containers are mounted on the same table and vibrated. If 10% of MH is filled inside each container, it will not flow easily.
The filling rate needs to be about 90%. Further, since the pressure design value of each container changes depending on the property of MH, it is necessary to make the thickness corresponding to it.

Further, each of these containers complies with the law, and it is necessary to install a safety valve (not shown) if necessary. It is natural that each MH container is evacuated in advance before starting the operation to activate the MH inside so as to be able to store hydrogen. At first, in this device in which all the control valves and control valves are closed, the control valve K is opened and the hydrogen gas of the raw material from A (9.5 kg / c in this device).
After enclosing m2G) in the container I, the control valve K is closed.
Vanadium in the container I occludes hydrogen gas containing D ₂ and generates heat, but the vanadium is cooled by the cooling water flowing through the heat exchanger and kept at about 40 ° C. At this time, the pressure in the container I is detected by the detection end P1, and this value is 10
When approaching kg / cm ² , the MH temperature is changed by the control valve A-1 on the heat medium inlet side, and as a result, the internal pressure is maintained at a constant pressure, for example, 9.0 kg / cm ² .

In this way, the control valve C is gradually opened with the container I kept constant, and the hydrogen gas in the container I is caused to flow into the container X and stored in the MH inside. The container X is held at 3 kg / cm2G in advance. By these operations, D ₂ in the raw material hydrogen is concentrated and stored in the MH in the container I, and the remaining gas is stored in the container X.

As the next operation, the control valve C is closed and the control valve D is closed.
Is opened and high-temperature water (90 ° C.) is passed through the heat exchanger in the container I, so that the D ₂ -enriched hydrogen gas stored in the MH-I flows out to the container II. At this time, the pressure in the container II is 9.
The flow rate or temperature of II-H was adjusted so as to be controlled at less than 5 kg / cm2G.

In this way, the alloy in the container II is further
Hydrogen is occluded in the concentrated state of ₂ . The heat generated by the MH at this time is absorbed and removed by the heat exchanger in the container II. The hydrogen gas in the space in the container II moves to the container X by closing the valve D and the valve E and opening the valve F in a state where the temperature and pressure are constant in the container II. At this time, by controlling the pressure in the container II to 3 kg / cm ² , the gas mainly containing H ₂ in the space of the container II having a small amount of D ₂ is transferred from the MH-II to the container X.

By performing this operation in the same manner as II → III and III → IV, the D ₂ concentration is gradually increased, and M in the container IV is increased.
26% in the gas released by opening the control valve I from H
Of D ₂ was included. At this time, the D ₂ concentration in the raw material hydrogen was 0.015%. In this embodiment, the container has four stages, but by increasing the number of stages, for example, 9
It is easy to obtain a concentration of D ₂ of 9% or higher.

The feature of the present invention is that by applying vibration,
Since it is to promote heat exchange between the MH powder and the heat transfer surface,
In the examples, deuterium was separated by assuming that the vibration was stopped as a conventional MH apparatus. However, the process at each stage of the containers I, II, III to X is 30 during vibration.
Although the hydrogen absorption was completed in a minute, and the D ₂ concentrated gas was obtained in about 3 hours in total, one step did not complete even after 3 hours when no vibration was applied (the hydrogen absorption was not completed and The pressure did not drop) I had to stop. Even in the conventional MH device which does not give vibration, the heat transfer area in the heat exchanger inside the container is extremely increased, so that the MH device can have a capacity similar to the deuterium separation capacity of the present invention. However, considering the increase in equipment cost and the difficulty of manufacturing, the conventional type becomes an unrealistic device.

[0034]

The separation and concentration of D ₂ from hydrogen has conventionally required a large amount of electric power and energy, but the present invention enables this with a small amount of energy consumption. That is, the energy required in FIG. 4 is 9.5 kg / c.
It is merely power for compressing the raw material hydrogen gas to m ² or more, supplementary power for flowing hot / cold water, and power for vibrating the entire device,
The cost can be significantly reduced as compared with the conventional method. Further, compared to the conventional hydrogen isotope separation method using MH, it is possible to obtain the same production amount in a small-scale facility remarkably in terms of equipment because the heat transfer rate is improved by the flow by applying vibration. Also in this respect, the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the influence of MH on the flow of powder.

FIG. 2 (a) is a diagram showing a change in MH layer temperature due to a high temperature heating medium when no vibration is applied. (B) The figure which shows the change of MH layer temperature when giving a moderate vibration. (C) The figure which shows the change of MH layer temperature when giving strong vibration.

FIG. 3 is a vibration analysis diagram for giving a flow to the MH.

FIG. 4 is a flow chart of a D ₂ separation and concentration device using vanadium according to an embodiment of the present invention.

FIG. 5 is an explanatory view of the MH container of the present invention.

[Explanation of symbols]

1 MH container 2 Vibration motor 3 Universal joint 4 Heat exchanger 5 Pendulum 6 Spring 7 Vibrator 8 Heat medium inlet / outlet pipe I, II, III, IV, X MH container A-1, A-2, A-3, A -4 regulating valve B raw hydrogen introduction pipe C~K control valve P ₁ to P ₄ pressure detector

Claims (1)

[Claims] 1. An apparatus for separating and concentrating hydrogen gas isotopes, which is equipped with the following apparatus conditions (a) to (f). (A) A plurality of containers holding hydrogen storage metals or alloys are installed, (b) Each container in (a) above is connected to a hydrogen gas pipe by a valve, and hydrogen gas is first introduced. Pipes and valves for introducing hydrogen gas, which is the raw material, are installed in the container on the inlet side, and the container for introducing hydrogen gas at the end is for introducing hydrogen gas that has been separated and concentrated into another device or container. (C) In addition to the containers (a) and (b), one or a plurality of containers containing hydrogen-absorbing metals or alloys are installed. (a) and (b) are connected to the vessel by pipes and valves. (d) The vessels of (a) and (b) have a heat exchanger built-in and are made of hydrogen storage metal or alloy. It is connected to a pipe that allows a cold heat medium and a hot heat medium to flow from the outside to change the temperature. And that it has been installed a pressure detector (e) of all the containers,
Having a device for controlling the temperature and flow rate of the heat medium flowing into the container by the differential pressure between the detected pressure and the set pressure, (f) All containers are mounted on a spring that absorbs vibration, and 0 1. Having a device that applies vibration in the range of 1G to 10G.