JPS6197101A - Device and method of thermochemically generating hydrogen - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION The present invention relates to hydrogen generation apparatus and methods, and more particularly, to the co-cracking of endothermically and exothermically decomposable hydrides. Regarding the generation of hydrogen by.

Thermal hydrogen generation from metal hydrides or hydrogen generation by the reaction of metals or metal aqueous compounds with water is known, and such hydrogen generation systems have major safety concerns compared to storage systems for gaseous or liquid hydrogen. It is widely acknowledged that he is right-handed.

However, the relatively small amount of hydrogen per unit ff1 that most metal hydrides can store results in an unacceptably large amount of hydrogen in terms of weight and (in some cases) volume in hydride-based devices. This may result in disadvantages. For commercial hydrogen storage purposes, composite metal hydrides of titanium and iron, for example, have been used. However, 60 bonds of such hydride (Ti Fe H) are required to release one pound of hydrogen.

Therefore, in order to generate 10 bonds of hydrogen, ff1ffi of the hydride alone becomes 600 bonds, and ff1ffl of the hydride reaction initiator is added to it. Such weight is unacceptable in applications requiring hydrogen production in light quantities, such as when inflating balloons launched from rockets at high altitudes.

The weight of hydride-based devices can be reduced by using other metal aqueous compounds that are lighter in weight. For example, in the case of magnesium hydride, approximately 1 pound of hydrogen can be generated with 14 bonds of hydride, so the total ff1m of hydride required to generate 10 bonds of hydrogen is reduced to 140 bonds. . However, in order to decompose magnesium hydride, it is necessary to supply multiple ω heat, which creates a new problem. In order to decompose magnesium hydride, approximately 3,900 kcal or 1
17.8 kcal of heat per mole must be delivered at operating temperatures around 300°C. The heat source required for this increases the weight of the device. When using a chemical heat source, according to the chemical reaction formula % formula % (1) (in the formula, ΔH = 17.9 kcal), 1 kc
It is expected that approximately 1 (+) or 8.6 lbs @ will be added per pound of hydrogen generated.
Approximately 226 pounds of chemicals alone (<102 ka) will be required to generate Bond's hydrogen. Also, the estimated volume of such a device is about 90-100 liters or about 3.2-3.5 square feet.

Other sources of hydrogen include ionic hydrides of calcium and lithium and complex hydrides such as Li AI H4, which react with water to generate heat and hydrogen. A hydrogen generator using calcium hydride is based on the following reaction.

Ca Hz +2Hz O-+Ca (OH)2 +2
The calorific value of reaction (2) at Hz 25°C is Q, 7 kcal per 1 g of reactant, and the color of hydrogen evolution is 7 kcal per 1 g of reactant.
5.17 bonds per pound. Therefore, to generate 10 bonds of hydrogen, approximately 104.4 bonds of calcium hydride and 89.4 pounds of water are required, making their total weight approximately 200 bonds. In addition, calcium hydride has a density of 1.9 g/Cm2, i
Melting point higher than ooo °C, and -45 kcal/mo
It has a heat of formation of 1.

The reaction between lithium hydride and water not only generates more hydrogen than calcium hydride, but also has the chemical reaction formula L! H+H20→L! OH+H2+ΔH(3)
It also generates more heat, as represented by ΔH=26 kcal. The calorific value of reaction (3) at 25°C is 1.0 kcal per 1 g of reactant, and the amount of hydrogen generated is 7.7 kcal per 100 bonds of reactant.
5 bond. Therefore, to liberate 10 bonds of hydrogen, 40 bonds of lithium hydride and 90 bonds of water are required, so the total weight of the chemical is 13
It becomes 0 bond.

Note that lithium hydride has a density of 0.780/c1, 6
Melting point of 86 °C, and -21,7 kcal/lot +
7) It has heat of formation. By the way, lithium hydride melts without decomposing at 471°C. The exotherm from such a reaction raises the temperature of the product to about 900'C, which is well above the melting point of lithium hydroxide.

Since the reaction of calcium hydride and lithium hydride is exothermic, means must be provided to dissipate the heat generated, which can significantly increase the weight and complexity of the equipment. could be.

There is therefore a need for a hydride-based hydrogen generation system and method which can overcome the above-mentioned drawbacks of known hydride applications and methods while taking advantage of the safety and relatively long storage life of the hydride medium. Therefore, it would be desirable to provide a method.

The present invention aims to achieve such an objective.

SUMMARY OF THE INVENTION According to the present invention, a uniquely advantageous hydrogen generation device and method is provided which is characterized by large volumetric storage capacity, low weight, small external dimensions and relatively simple construction. Such a device is therefore suitable for applications such as devices for inflating balloons at high altitudes, devices for producing fuel for combustion engines, and safe, compact, lightweight hydrogen transportation devices.

The invention is based on hydrogen generation by the joint action of an endothermically decomposable metal hydride and an exothermically decomposable hydride. While all of these hydrides liberate hydrogen, the heat generated from the exothermically decomposable hydride is utilized to decompose the endothermically decomposable hydride. The relative proportions of these hydrides are adjusted to control reaction temperature, optimize hydrogen evolution and heat dissipation, and minimize weight and volume.

Briefly stated, the hydrogen generator of the present invention includes a first base material made of a metal hydride that decomposes endothermically to liberate hydrogen;
It includes a second base material made of an ionic hydride that exothermically decomposes to liberate hydrogen upon reaction with water, and a container containing these base materials. The first and second base materials are arranged adjacent to each other so that heat generated by decomposition of the ionic hydride is transferred to the metal hydride. Additionally, the ratio of metal hydride to ionic hydride is adjusted to ensure decomposition of the metal hydride and to control the temperature within the vessel.

The water distribution means for evenly distributing water to the ionic hydride is connected to a source of pressurized water via valve means and is provided with valve actuation means for opening the valve means to initiate the reaction. ing. Furthermore, means are provided for collecting the hydrogen liberated from the hydride and directing it to the outlet of the vessel.

Preferably, the metal hydride is magnesium hydride and the ionic hydride is lithium hydride. 1st
The second base material can also be formed into a non-cylindrical shape. In that case, the first matrix is disposed coaxially around the second matrix, forming a passageway for free hydrogen between the two matrixes in the first compartment of the container, and The material is arranged coaxially around the water distribution means. The water distribution means may consist of a manifold tube provided with a number of openings to evenly distribute water to the ionic hydride. The water may be placed in the second compartment of the container and pressurized with an inert gas.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As previously noted, the present invention is particularly well suited for safe, lightweight hydrogen generation systems with large volumetric storage capacities useful for inflating balloons launched from rockets or the like at high altitudes. The following description will also be made in connection therewith. However, as will become clear from the description below, this is merely one example of the application of the present invention.

Large volume storage capacity II provided by the present invention
As mentioned above, ffi's hydrogen generator utilizes the chemical properties of the reaction between ionic hydrides and water to efficiently generate hydrogen and heat, and also dissipates the heat generated in this reaction to the outside world. Thermochemical principles to optimize systems consisting of metal hydrides and ionic hydrides/water by instead using them for the decomposition of metal hydrides to generate additional hydrogen at lower temperatures. Based on.

Utilizing the heat generated from the exothermic reaction of the ionic hydride and water for the decomposition of the metal hydride avoids the need to provide such a heat dissipation mechanism, thus reducing the l1lfi (and volume) of the device. It becomes possible to reduce this. In this case, the ratio of the three chemicals (ionic hydride, water and metal hydride) will control the mountain pass temperature, since the decomposition of the metal hydride provides a regulating effect.

A suitable example of an endothermically decomposable metal hydride is magnesium hydride. This is because, among metal hydrides, magnesium hydride has a relatively large hydrogen storage capacity per unit ff151, and can generate about 1 pound of hydrogen per 14 pounds of hydrogen. However, it is of course possible to use any endothermically decomposable metal hydride in the practice of the present invention. A preferred ionic hydride is lithium hydride. As pointed out above,
This produces about 7.75 pounds of hydrogen per 100 pounds of reactants and 1.75 pounds per gram of reactants at 25°C.
Generates 0 kcal of heat of reaction. It is of course also possible to use any ionic hydride that reacts exothermically with water to generate hydrogen in the practice of the present invention.

The chemical weight of the lithium hydride/water system is chosen such that the heat of formation decomposes the magnesium hydride and provides a final operating temperature on the order of 300°C, relative to the chemical gravity of the magnesium hydride. By combining the lithium hydride/water system and the magnesium hydride system in this way, the amount of hydrogen generated per m unit of chemical substance does not decrease, and the need to dissipate excess heat is avoided. The final device mm will be reduced.

Table 1 below shows the thermochemical properties of the system consisting of lithium hydride/water and magnesium hydride, as well as the calculation results that lead to the following general equilibrium chemical reaction equation for the reaction at 300°C.

I Li H+1820+0.8Mg+2→1 L!
OH+0.8MO+1.882 (4) Table 1 Thermochemical properties and calculation results Heat of reaction (ΔH) Li H+Hz O-+L
i OH + H226kcal/mat - exothermic M (II H2 → M17 +Hz 19, 8kcal/mol - endothermic 6006K Li OH10cal/mo
l-deg specific heat CP MgH2
11.6 cal/mol ・deQ82 7
cal/mol -deg density ρ
M(I 82 1.8 a/ccLi t1
0. 78g/cc reaches 300℃ L
i Amount of heat required for O83kcal/mol
MgHz 3.48kcal/mo at 1300℃ (a) Used for decomposition of theoretical value MgHz
17.42kcal/mat (Li H+H
2) Possible net heat ffl (b) Value assuming 12% loss 15, 3 kcal/mo1 M! ; I +2 /Li 8 molar ratio (decomposed) Mg
+2=0.8 In Table 2 below, the total weight and volume calculations for a 10 bond hydrogen generating device are given.

As noted, the total ff1ffi and total volume of chemicals are 130.9 pounds and 1.78 cubic feet, respectively.

Generated 8 2 4.53kg balloon (variable)
(10 bond) L i 8 10.17kg 13.04
1J v To/L/(22,45 Bonton H2022,88Jl 22.88 liters (50,48 Bond) MU H226,27Jl 14.59 liters (57,99 lbs 59.32kill 50.51 liters total (130,9 (1,78 cubic feet) Figures 1 and 2 show a preferred hydrogen generator ff10 of the present invention using metal hydrides and ionic hydrides/water, which The purpose is to inflate a balloon launched from a high place.

As shown in the figure, the hydrogen generator 10 includes a container 12, but the container 12 may be made of stainless steel and have a cylindrical shape, for example. Such a shape is preferred because it can be easily adapted to a limited space. The container 12 is divided into a plurality of compartments 14, 16, 18 and 20 and has an outlet 22 connectable to a balloon filling tube (not shown). container 12
The upper compartment 14 serves as a plenum for collecting the hydrogen liberated by the reaction of the hydride in the compartment 16 (as indicated by the arrow in the figure), as will be explained in more detail below. The plenum is connected to the outlet 22 via a normally closed, pressure-operated check valve 24 designed to open under a predetermined pressure.

For the reasons mentioned above, it is preferable that the hydrogen generator 10 consists of a system of magnesium hydride and lithium hydride/water. Lithium hydride and magnesium hydride are contained within compartment 16 in respective hydride matrices 26 and 2.
It is arranged as 8. Preferably, each base material has a cylindrical shape. The dimensions of the cylindrical base material are such that the magnesium hydride base material 28 can be disposed coaxially around the lithium hydride base material 26 as shown, and an annular passage 30 is formed between the two base materials. It is preferable that the Preferably, the lithium hydride matrix 26 is porous or porous with a predetermined porosity that allows hydrogen release without creating excessive local pressure. The lithium hydride matrix 26 also includes a number of radially extending passageways 34 that communicate with the annular passageway 30 and with a longitudinally extending coaxial cylindrical space 36 within the lithium hydride matrix 26. It is also possible to provide one. Magnesium hydride may be solid or granular. If in granular form, it may contain a binder to bind the particles together and slow down the reaction, and a supporting annular retaining screen (not shown).
It may be placed inside. Note that the relative dimensions of the hydride base material are determined by the chemical reaction formula (4) as described above.

Disposed within the cylindrical space 36 is water distribution means, which may consist of a manifold tube 40 extending in the longitudinal direction. Such a manifold tube 40 has a large number of openings 42 evenly distributed along its length and circumference.
is provided.

The lower end of manifold tube 40 (shown in FIG. 1) is connected to a source of pressurized water within compartment 20 via isolation valve 44. The valve 44, which is normally closed, is operated by a conventional M4 electric detonator actuated by a pressure switch.
It can be operated by the mechanism 46. Actuator M44
Electric power for the container 12 is supplied from a battery 48, and atmospheric pressure is applied to the pressure switch through a pressure detection port 50 provided in the side wall of the container 12. A water filling port 52 communicating with the compartment 20 is also provided in the side wall of the container 12 adjacent to the pressure detection port 50 .

Compartment 20 can be divided into two parts by movable piston 54. Water may be supplied to the upper portion of the compartment 20 through a water fill port 52, and pressurized inert gas may be supplied to the lower side of the piston 54 through a gas fill valve 56.

For safe storage of the hydrogen generator, it is desirable to keep the water and inert gas containing portions of compartment 20 empty and to leave the detonator actuation mechanism for valve 44 uninserted. In use, there is a water fill port 52 in the upper part of the compartment 20.
The lower portion of the compartment 20 may be supplied with pressurized inert gas through the gas fill valve 56.

Finally, the detonator actuation mechanism is inserted. After the launch, the production
A pressure sensor on the J-side 46 senses atmospheric pressure through a pressure detection port 50, and when a predetermined altitude is reached, the electric detonator is actuated to open the valve 44. Water pressurized by inert gas from below the piston 54 is transferred to the manifold pipe 40.
Press-fitted inside. At the same time, the piston 54 moves upward (in FIG. 1) until the water is completely evacuated from the compartment 20. In that case, the speed of movement of the piston 54 is determined by the reaction rate of the hydride within the compartment 16. When the water contacts the inner lithium hydride matrix 26, the lithium hydride is converted to lithium hydroxide and heat and hydrogen gas are evolved. Note that hydrogen gas may initially carry away water vapor from the gray fabric. The heated hydrogen gas passes through the porous lithium hydride matrix to passageway 30 where it releases water vapor and some thermal energy. Most of this thermal energy flows into the outer magnesium hydride matrix 28. The absorption of such heat by the magnesium hydride reduces the temperature within the compartment 16 and causes the magnesium hydride to thermally decompose and generate additional hydrogen. The generated hydrogen flows into the plenum (compartment 14) above compartment 16 and a pressure increase occurs. When the pressure in the plenum reaches a predetermined value, the check valve 24
opens to allow hydrogen to flow into the balloon filling tube. This inflow of hydrogen continues until the reaction is completed. If the amounts of hydride and water are selected according to chemical reaction equation (4), the heat generated by the reaction between lithium hydride and water is substantially completely absorbed into magnesium hydride, thereby allowing hydrogen dissociation to occur. It becomes possible to maintain the temperature of 300°C required for this purpose.

Table 3 below lists typical dimensions for the chemical composition of a hydrogen generator such as those in Figures 1 and 2 with a volume storage capacity equal to twice the volume storage capacity required to generate 10 Bonds of hydrogen. , volumes and strain amounts are shown.

That is, the hydrogen generator shown in Table 3 has a safety factor of 2. Assuming complete reaction of all materials, the minimum parameters for a hydrogen generator to generate 10 pounds of hydrogen may be 1/2 of the values shown in Table 3.

Table 3 (inch) (inch) (inch) (cubic)
(pounds) 8 porosity 25% Assuming that the maximum allowable payload of the balloon is 300 Bond, a hydrogen generator with the parameters shown in Table 3 will have 38 Bond for structural members, mechanisms and fittings. This means that there is a margin of

As can be seen from the above description, the present invention provides a compact, light fjt, highly efficient thermochemical hydrogen generation device useful for a variety of applications. In addition to being used as a balloon expansion device, the hydrogen generation device of the present invention is also useful as a fuel source for combustion engines and as a safe, compact, and lightweight hydrogen transportation device.

Although the preferred embodiments of the present invention have been described above, various changes may be made to the embodiments without departing from the principles and spirit of the present invention whose scope is defined by the claims. will be obvious to those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a hydrogen generator according to the present invention, and FIG. 2 is a cross-sectional view along line 2--2 of the vJ1 diagram. In the figure, 10 is a hydrogen generator, 12 is a container, 14°16.
18 and 20 are compartments, 22 is an outlet, 24 is a check valve, 26 is a lithium hydride matrix, 28 is a magnesium hydride matrix, 30 is an annular passage, 34 is a radial passage, 3
6 is a cylindrical space, 40 is a manifold pipe, 42 is an opening, 4
4 is a shutoff valve, 46 is an operating mechanism, 48 is a battery, 50 is a pressure detection port, 52 is a water filling port, 54 is a movable piston, and 56 is a gas filling valve.

Claims (1)

[Claims] 1. (a) a first base material made of a metal hydride that decomposes endothermically to liberate hydrogen; (b) that decomposes exothermically to liberate hydrogen by reaction with water; a second matrix comprising an ionic hydride; (c) a container containing said first and second matrices; (d) a source of pressurized water; and (e) distributing said water evenly to said ionic hydride. (f) valve means connected between said water distribution means and said pressurized water source;
and (g) valve actuation means for actuating said valve means to direct pressurized water to said water distribution means, wherein said first and second base materials contain water generated by decomposition of said ionic hydride. are arranged adjacent to each other in the container so that heat transferred to the metal hydride is transferred to the metal hydride;
and a hydrogen generating device characterized in that the ratio of the metal hydride to the ionic hydride is adjusted so as to ensure decomposition of the metal hydride and control the temperature within the container. 2. The device according to claim 1, wherein the metal hydride is magnesium hydride. 3. The apparatus of claim 1, wherein the ionic hydride is selected from the group consisting of lithium hydride and calcium hydride. 4. The device according to claim 1, wherein the ionic hydride is lithium hydride. 5. Each of the first and second base metals has a cylindrical shape, and the first base metal forms a passage for free hydrogen between the two base metals in the first compartment of the container. Claim 1, wherein the water distributing means is coaxially disposed around the second base material, and the second base material is coaxially disposed around the water distribution means. equipment. 6. The second base material is provided with a large number of passages extending in the radial direction, and the radial passages extend through the passage formed between both base materials and the internal space of the second base material. Apparatus according to claim 5, which follows. 7. The water distribution means consists of a manifold tube coaxially arranged in the interior space of the second base material, and the manifold tube has a number of openings distributed along the longitudinal direction and the circumferential direction. and wherein said source of pressurized water comprises a second compartment of said container divided into first and second parts by a movable piston, said first and second parts containing water and 6. Apparatus according to claim 5, each containing a pressurized gas. 8. said valve means comprising a normally closed valve connected between said manifold tube and said first portion of said second compartment, and said valve actuating means for opening said valve; 8. The apparatus of claim 7, comprising an electrical actuator and operating means for operating said electrical actuator in response to a predetermined condition. 9. The apparatus of claim 8, wherein said predetermined condition is atmospheric pressure and said operating means comprises a power source and a pressure sensitive switch for connecting said power source to said electrical actuator. 10. The container has water in communication with the first and second parts, respectively, to enable the first and second parts of the second compartment to be filled with water and gas, respectively. 8. Apparatus as claimed in claim 7, characterized in that filling means and gas filling means are provided and the container is also configured to allow insertion of the valve actuation means prior to use. 11. The container is provided with a plenum that communicates with the passage between both base materials and the outlet of the container, and a pressure-operated valve that is always closed is disposed between the plenum and the outlet. A device according to claim 1. 12. The device of claim 1, wherein the device is configured to be placed inside a rocket for inflating a balloon launched from the rocket at a high altitude. 13, (a) a first base material made of magnesium hydride;
and a second matrix comprising an ionic hydride that reacts with water and decomposes exothermically within the first compartment of the container;
(b) placing pressurized water within a second compartment of said container;
c) uniformly supplying pressurized water to the second base material to cause a reaction between the ionic hydride and the water; (d) controlling the temperature in the container and decomposing the magnesium hydride; By selecting the ratio of the magnesium hydride, the ionic hydride, and the water to ensure that the heat generated by the reaction is transferred to the magnesium hydride to endothermically decompose the magnesium hydride. (e) collecting hydrogen generated by the reaction of the ionic hydride with the water and decomposition of the magnesium hydride; and (f) supplying the hydrogen to an outlet of the container. Characteristic hydrogen generation method. 14. The method of claim 13, wherein said ionic hydride is selected from the group consisting of lithium hydride and calcium hydride. 15. The method according to claim 13, wherein the ionic hydride is lithium hydride. 16. In the case where the step of forming the first and second base materials as cylinders of magnesium hydride and ionic hydride, respectively, is additionally included, the first base material has a passageway between the two base materials. a plurality of radially extending passageways are disposed coaxially around the second base material such that the second base metal forms a plurality of radially extending passageways in the second base metal; 14. The method of claim 13, wherein the passageway therebetween communicates with the interior space of the second base material. 17. The method of claim 16, wherein the second base material is formed to have a predetermined porosity that allows hydrogen liberation without creating excessive local pressure. 18. In the case where the magnesium hydride is granular, the first base material contains a binder that binds the magnesium hydride particles together so as to control the decomposition rate of the magnesium hydride. The method according to paragraph 13. 19. The method of claim 13, wherein the pressurized water is provided in response to the predetermined atmospheric pressure condition, wherein the method further includes the step of sensing the predetermined atmospheric pressure condition. 20. The method of claim 19, further comprising the step of using the hydrogen to inflate a balloon launched from a rocket at altitude.