JPS6149241B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydrogen generating device that can control the amount of hydrogen generated by a reaction between a metal hydride and water in accordance with the amount of hydrogen consumed.

This type of hydrogen generator is used, for example, as a simple fuel source for hydrogen/air (or oxygen) fuel cells, and is made by reacting water with a metal hydride, such as calcium hydride or lithium hydride. It is designed to generate hydrogen. However, the reaction rate between the metal hydride and water is extremely fast, and there is a problem in that the hydrogen gas pressure inside the reactor rapidly rises to an excessive pressure. One way to solve this problem is to slow down the reaction rate.
It was widely adopted. For example, methods have already been proposed such as forming metal hydrides into special shapes or mixing metal hydrides with impurities that do not react with water. However, in these methods, even when there is no longer a need to generate hydrogen and the supply of water is stopped, there is a risk that the delayed reaction will proceed and the gas pressure will rise excessively. Conventionally, for this purpose, the pressure resistance of the generator is increased or a safety valve is provided in the generator to release hydrogen at a predetermined pressure or higher to prevent overpressure caused by the generated hydrogen. Among these, increasing pressure resistance increases the weight and volume of the generator.
Furthermore, the release of hydrogen has the disadvantage that the utilization efficiency of the hydride, which is a raw material, decreases. Furthermore, since these methods slow down the reaction rate,
There was a problem in that when there was a sudden need to generate hydrogen, this request could not be met.

In view of the above-mentioned points, the present invention eliminates the drawbacks of the prior art and allows the amount of hydrogen generated to be quickly and continuously controlled in accordance with changes in the amount of hydrogen consumed.
It is an object of the present invention to provide a hydrogen generator that can improve the efficiency of using metal hydrides while preventing the risk of overpressure.

To achieve this objective, the first thing to consider is to control the amount of water supplied to the metal hydride according to the amount of hydrogen generated, but this is quite complicated when the reaction rate is taken into account. Therefore, it does not meet the requirements as a simple fuel source. For this reason, the inventors of the present invention considered using steam instead of water, and after conducting various experiments, it was found that a wide range of reactions could be obtained with a relatively small amount of water. Since the amount of hydrogen generated is proportional to the amount of water supplied, if it is supplied in the form of steam, a relatively small amount of hydrogen can be generated in a short time.

By the way, providing a separate device for generating water vapor would go against the requirement of a simple fuel source. Therefore, as a result of further investigation, the present inventors focused on the reaction heat generated during the reaction between water and metal hydride, and found that if the supplied water was vaporized using this reaction heat, it could be used as a simple device. While meeting the requirements
It has been concluded that the above objectives can be achieved.

Accordingly, the above-mentioned object, according to the invention, comprises a reactor containing a metal hydride and a water supply pipe provided in the reactor for supplying water to the metal hydride, the supply water being This is achieved by vaporizing the feed water in the water supply pipe using the heat of reaction generated when the metal hydride reacts with the metal hydride to generate hydrogen.

Next, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 shows a schematic configuration diagram of an embodiment of the present invention. In the figure, a water tank 1 contains feed water, pressurizes it by gas pressure, spring pressure or other methods, and supplies the feed water to a reactor 5 through a water flow control valve 3 and a check valve 4. A water supply pipe 6 is provided in the reactor 5, and a metal hydride 7 is accommodated therein. Reference numeral 11 denotes an outlet provided at the end portion 10 of the water supply pipe 6. In addition, 8 is a generated hydrogen outflow valve, 9
is a safety valve.

Next, the functions of the above-described configuration will be explained.
Initially, the supply water supplied from the water tank 1 flows out from the outlet 11 of the end portion 10 via the corrugated water supply pipe 6 inserted from the top to the bottom inside the metal hydride 7. This feed water reacts with an adjacent metal hydride, such as calcium hydride (CaH ₂ ), to generate hydrogen and the heat of reaction. This reaction formula is shown in equation (1).

CaH ₂ +2H ₂ O → Ca(OH) ₂ +2H ₂ +49kcal/mole...(1) The temperature inside the reactor 5 rises due to this reaction heat. According to actual measurements by the present inventors, when the inner diameter of the water supply pipe 6 is selected to be relatively small in order to increase the heat exchange rate, the temperature of the supply water in the end portion 10 is approximately
It was confirmed that the temperature reached around 300℃. Therefore,
The supplied water is completely vaporized within the water supply pipe 6 and flows out from the outlet 11. This vaporized feed water has better fluidity than liquid feed water, and spreads over a wide area in the reactor 5, and is not limited to the vicinity of the outlet 11, but is located in calcium hydride 7, which is difficult to reach with water. It also reacts with hydrogen to generate hydrogen. In this way, the reaction can occur throughout the reactor 5, so even if the calcium hydride 7 near the outlet 11 finishes its reaction and no longer contributes to the generation of hydrogen, the effect is small. . That is, by controlling the amount of water vaporized to be supplied, the amount of hydrogen generated can be increased or decreased in a short time, so the delay in the hydrogen generation reaction is reduced, and the pressure fluctuation in the reactor 5 is reduced.

In addition, if the end part 10 of the water supply pipe 6 is tightly attached to the bottom of the reactor 5, the reaction will be completed from the calcium hydride 7 near the end part 10, and it will no longer contribute to the generation of hydrogen. However, when the reactor is next used, the hydrogen generation reaction is carried out only after the water reaches the upper layer of the reactor 5, which is far from the end portion 10, resulting in a slow reaction rate.
For this purpose, the end part 10 is inserted from the bottom of the reactor 5 into the D
If the reactor 5 is installed at a higher position, the reaction inside the reactor 5 will be
First, water supplied in the form of water causes the reaction to occur in the lower layer of the end part, and then water vapor generated by the reaction heat generated by this reaction causes the reaction to occur in the lower part of the end part.
Since the reaction moves to the upper layer of 0, unreacted calcium hydride remains in the lower layer of the end portion 10. Therefore, even when the feed water is supplied in the form of water again during the next use, the reaction in the lower layer is carried out again, so there is no reduction in the reaction rate. If the distance D is selected so that the reaction of the calcium hydride 7 present in the lower layer is likely to be completed when the reaction of the calcium hydride 7 present in the upper layer is completed,
The utilization efficiency of calcium hydride 7 can be improved.

Next, FIG. 2 shows a state diagram of changes in the internal pressure of the reactor due to changes in the amount of hydrogen supplied in FIG. 1. In the figure, line A shows the change in the amount of hydrogen supplied, and line B shows the change in pressure inside the reactor 5 caused by the change in the amount of hydrogen supplied. If the hydrogen supply amount is temporally, e.g. 0.5/mi
When a change of n to 1.5/min occurs, reactor 5
The internal pressure change within the chamber is stable within the range of 1.5Kg/cm ² G to 3.0Kg/cm ² G. In other words, since the feed water is supplied in the form of steam, the reaction delay with calcium hydride 7 is reduced and the reaction rate is improved, so that the amount of hydrogen generated is faster depending on the amount of hydrogen consumed. This is because it has become possible to increase and decrease following the.

Next, FIG. 3 shows a schematic configuration diagram of another embodiment of the present invention. In the figure, a water supply pipe 14 inserted into the reactor 5 from the top to the bottom is provided with a plurality of heat-absorbing fins 15. The size and number of the heat-absorbing fins 15 are such that the heat of reaction is absorbed by the water supply pipe 1.
4, so that the feed water is completely vaporized.

Next, FIG. 4 shows a schematic configuration diagram of still another embodiment of the present invention. In the figure, a water supply pipe 16 is wound around the outer periphery of the reactor 5 in a coil shape from the top to the bottom, the end part 10 is inserted into the reactor 5, and the water vaporized water is supplied from the outlet 11. It is configured to flow out. The number of turns of this coil is selected so that the reaction heat in the reactor 5 is absorbed by the feed water in the water supply pipe 13, and the feed water is completely vaporized.

In this embodiment, the water supply pipe 16 is connected to the reactor 5.
Although it is wound in a coil shape around the outer circumference of the reactor 5, it is also possible to wind it in a coil shape around the inner circumference of the reactor 5.

As explained above, according to the present invention, by using steam instead of water, a hydrogen generating reaction with a wide range of metal hydrides can be obtained with a relatively small amount of water, and the hydrogen generation reaction can be performed in response to changes in the amount of hydrogen consumed. This makes it possible to quickly and continuously control the amount of hydrogen generated, while preventing the risk of overpressure.
In addition, the metal hydride reacts effectively with water vapor, and the utilization efficiency of the metal hydride is improved. Furthermore, the water vapor used in the reaction is vaporized in the water supply pipe by the reaction heat generated during the reaction between the feed water and the metal hydride, without the need for a separate special steam generator. It has the effect of being simple.

In this embodiment, a hydrogen generator attached to a fuel cell is used as an example, but the present invention is effective not only for such applications but also as a means for easily obtaining hydrogen outdoors.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention, and FIG.
The figure is a state diagram of changes in reactor internal pressure with respect to changes in the amount of hydrogen supplied in Figure 1, Figure 3 is a schematic configuration diagram of another embodiment of the present invention, and Figure 4 is a schematic configuration diagram of still another embodiment of the present invention. It is a diagram. 3; Water flow control valve, 4; Check valve, 5; Reactor, 6; Water supply pipe, 7; Metal hydride, 8; Generated hydrogen supply valve, 9; Safety valve, 10; End part, 11;
Air outlet, 13, 14, 16; water supply pipe, 15; heat absorption fin.

Claims (1)

[Claims] 1. A reactor containing a metal hydride, and a water supply that is thermally connected to the metal hydride in the upper part of the reactor and supplies water to the metal hydride in the lower part of the reactor. A hydrogen generating device comprising: a hydrogen generating apparatus, wherein the supplied water is vaporized in the water supply pipe by reaction heat generated when the supplied water reacts with the metal hydride to generate hydrogen.