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INVENTION
Patent of the Russian Federation RU2192072
METHOD FOR PRODUCTION AND STORAGE OF HYDROGEN
IN AUTONOMOUS ENERGY INSTALLATIONS
The name of the inventor: Avakov VB; Zinin VI; Shulyakovsky OB; Shevelkin V.I.
The name of the patent holder: JSC "Special Design Bureau of Boiler Building"
Address for correspondence: 199106, St. Petersburg, VO, 23 line, 2, OAO SKBK
Date of commencement of the patent: 2001.05.22
The invention relates to autonomous power engineering, in particular to a method for producing and storing hydrogen in autonomous power plants with a cycle of operation from tens to thousands of hours, primarily for submarines. According to the invention, the method comprises producing hydrogen by generating water vapor, passing it through a sorbent consisting of iron and a catalyst, and conducting an iron oxidation reaction. One of the initial components of the reaction is water, which is formed during the reaction of generation of electricity in ECG. In addition, in autonomous, air-independent plants for generating steam necessary for the iron vapor process for producing hydrogen, the heat of the exothermic decomposition reaction of a substance (eg, hydrogen peroxide) containing oxygen can be used. For a uniform supply of hydrogen, the oxidation reaction of iron is carried out with a variable (increasing) temperature during the process, volumetric constructions 4-6 g / cm 3 in weight of compacted fine iron are used to completely oxidize the iron and then recover it, providing steam access to a depth of not more than 1 -2 mm. In addition, the iron storage is divided into sections and, as the hydrogen evolution rate decreases, new sections are serially connected in the running section. A combination of these methods is possible. Reduction of oxidized iron is carried out in an autonomous power plant by hydrogen, carbon monoxide or a mixture thereof. The technical result of the invention is to ensure the safety and duration of hydrogen storage.
DESCRIPTION OF THE INVENTION
The invention relates to the field of autonomous power engineering, namely to the field of hydrogen production and storage systems for autonomous power plants, mainly with electrochemical generators (ECG).
A distinctive feature of autonomous power plants (EI) is the periodicity of their functioning during a relatively short time, the duration of which is determined by the reserves of reagents (fuel and oxidizer).
Such facilities include installations for submarines, underwater vehicles, ships, rail and road transport, household energy sources of periodic action, and periodically operating stationary power plants used in critical facilities that do not allow power interruption.
The method of hydrogen production and storage of autonomous EC must ensure safe production of hydrogen, and its long and safe storage at the minimum cost, mass and volume of the hydrogen production and storage system, the simplicity of the operation of the EA and the utilization (or regeneration) of the reaction products.
The following methods of hydrogen production and storage for autonomous power plants are known (see NS Lidorenko, GF Muchnik "Electrochemical generators", Moscow, 1982):
- storage in the gaseous state, where hydrogen is stored in vessels under high pressure (up to 50 MPa) and after throttling is supplied to ECG;
- storage in a liquid state (cryogenic), when hydrogen before gas is supplied to the ECG;
- storage in the composition of intermetallic compounds, in which it is pre-sorbed, and before being fed to ECG, it is desorbed with heat absorption;
- storage of hydrogen in a chemically bound state in the composition of hydrogen-containing compounds, when hydrogen is produced by an appropriate chemical process.
The last method of obtaining and storing hydrogen is:
- storage of hydrogen in the composition of ammonia and its production by dissociation;
- storage of hydrogen in the composition of methanol and other liquid hydrocarbons and its production by steam or steam-oxygen conversion thereof;
- storage of hydrogen in the composition of metal hydrides and its production by thermal decomposition;
- storage of hydrogen in the composition of hydrides of metals and water and its production by hydrolysis of metal hydrides;
- storage of hydrogen in water and its production by interaction with magnesium or aluminum alloys.
None of the above methods of storage and production of hydrogen does not meet all the requirements for hydrogen production and storage systems for autonomous EC.
The method of storage in intermetallic compounds is the most safe and convenient to use, but it is expensive in manufacturing and predetermines a large mass of EC because the cost of 1 kg of intermetallic compound is $ 15-35, and the mass capacity of sorbents that have found wide application is only 1.5-2.0% . The lowest mass and volume of the installation can be obtained with a sufficient level of safety using methanol or hydrocarbon fuel conversion, but gaseous reaction products are inevitable, which in some cases are unacceptable (on submarines and other similar objects), because Can lead to the loss of stealth.
The question of stealth with sufficient safety and optimal weight and size indicators can be realized by using the method of storing hydrogen in water and obtaining it as a result of hydrolysis using metal hydrides, magnesium and aluminum alloys, but the chemical process is irreversible, because The reaction products are not regenerated.
A method for producing hydrogen by the interaction of water vapor with iron at high temperatures, which was discovered by Lavoisier in 1783, is also known. The iron-vapor method for producing hydrogen is that a superheated water vapor with a temperature of 200 ° C is passed through a sorbent consisting of fine iron, 1000 o C. The higher the temperature, the lower the equilibrium concentration of hydrogen in the steam-water mixture, but the higher the reaction rate.
The interaction of iron with water vapor is carried out according to the following reactions:
Fe + H 2 O 
FeO + H 2 (1)
3Fe + 4H2O Fe 3 O 4 + 4H 2 (2)
2Fe + 3H2O Fe 2 O 3 + 3H 2 (3)
According to the first reaction, 0.4 l H 2 / g Fe (3.56% by weight) can be produced, respectively, 0.53 l H 2 / g Fe (4.7% by weight), respectively, and 0 , 6 L H 2 / g Fe (5.3% by weight). All three reactions are weakly exothermic, however, taking into account the heat required for steam production, the iron-steam method of hydrogen production requires energy expenditure, although the cost of these costs is low and with the proper organization of the process (the use of heat recovery) is equivalent to the energy released At oxidation of 10-12% of hydrogen produced.
The reduction of iron oxides produced by reactions 1, 2, 3 can be carried out by hydrogen or a mixture of hydrogen with carbon monoxide. The interaction of iron oxides with carbon monoxide can proceed according to the following reactions:
FeO + CO Fe + CO 2 (4)
Fe 3 O 4 + CO 3FeO + CO 2 (5)
Fe 2 O 3 + CO 2FeO + CO 2 (6)
Reaction 4 is weakly endothermic, and reactions 5 and 6 are weakly exothermic.
The beginning of the practical application of the iron-vapor method should be attributed to 1794 in France. Hydrogen was produced in iron retorts filled with iron shavings. After heating to red heat, water vapor was passed through them. The resulting hydrogen was used to fill the balloons. Further development of the iron-vapor method was obtained after ZHilar in 1846 began to recover iron oxides with generator gas. At the end of the 19th century and in the first quarter of the 20th century, the iron-steam method was one of the most common methods of producing hydrogen.
However, the iron-vapor process of hydrogen production was periodic, inefficient, the resulting hydrogen was often used to reduce the oxides. This led to the fact that with the need to obtain large amounts of hydrogen, new, more progressive ways of industrial hydrogen production appeared, for example, coal gasification, and from the middle of this century the steam-oxygen conversion of natural gas, which completely replaced the iron-vapor process, and it was forgotten.
Recently, especially in Germany, there have been developments of new modified versions of the continuous iron-vapor process for the industrial production of hydrogen. The German application 4226496 A1 dated August 11, 1992 proposes a method for producing hydrogen at a temperature of 850 K in the iron-vapor process. Iron comes in the form of iron scrap and reacts with water vapor in a conventional shaft furnace. The process is continuous. The resulting gas contains 60% H 2 and 40% H 2 O. The resulting iron oxides are withdrawn from the shaft furnace and sent for recovery, which is carried out with a gas mixture containing CO, for example, conversion gas. Hydrogen in the process can be selectively isolated using molecular sieves. In the process, an additional stage of oxidation of FeO to Fe 2 O 3 with oxygen is provided. This is an exothermic reaction, and the heat generated during this process is used to obtain the necessary additional steam for the iron-vapor process.
In German patent No. 1242193 of 1967, a continuous two-step method for producing hydrogen of high purity is proposed. Oxidation of finely divided iron is carried out by water vapor at high temperature and pressure. Iron is mainly oxidized to FeO. Recovery of FeO is carried out with gaseous methane. Upon reduction, a mixture containing 60-95% Fe and about 5% FeO is obtained. The reduction temperature is 600-850 ° C.
It is proposed to carry out the process of reduction of iron oxides using solar energy (see the German application 4410915 A1 from 1995):
3Fе 2 0 3 + h 
= 2Fe 2 O 4 + 0.5 O 2 .
Of considerable interest is the thesis of A.Kh. Krause (Kontinuerliche Erzeugung von Wasserstoffnach Eisen-Dampf-Prozess, Thesis of RWTH Aachen, 1989). It details the physicochemical aspects of the iron-vapor process of hydrogen production and suggests a continuous method for its implementation. In the journal "Energietechnik", 1978, 28 11, p. 407-413 outlines the engineering problems of large-scale hydrogen production by iron-steam method.
Thus, the whole history of the development of the industrial iron-steam method for producing hydrogen is aimed at achieving the continuity of the generation process. There are also suggestions on the use of the iron-vapor method of hydrogen production for autonomous power plants.
Thus, in US Pat. No. 5,629,102 of 1997, a car with ECG is proposed. Hydrogen is produced at the fuel station of a car using the iron-steam method. After oxidation of iron, reaction products are unloaded at specialized filling stations, and a new portion of iron is loaded into the reactor instead.
Similar plants for hydrogen production and regeneration are described in US Pat. Nos. 4,547,356 of 1985, 5,510,201 of 1996 and 6,093,501 of 2000. The above hydrogen production methods are designed for greater productivity in relatively short periods of time (not more than a few hours). The main thrust of the proposals is a decrease in the hydrogen generation temperature due to the use of catalysts and removal of the process of iron generation outside the power plant. These proposals refer to autonomous power plants with a short cycle of operation (not more than a few hours), which is most typical for passenger cars.
This proposal refers to self-contained power plants with a long operation cycle - from tens to thousands of hours, primarily installations for submarines and underwater vehicles. For this type of installation it is characteristic that the mass of the reagent (iron) is many times greater than the mass of the actual power plant, therefore, the removal of the process of iron generation outside the power plant is of little use. In addition, the organization of separate bins to store freshly loaded and reacted iron leads to a loss of useful volume. Therefore, for installations with a long cycle of operation, iron regeneration is proposed to be carried out as part of the power plant.
The investigations carried out by the authors have shown that ensuring the completeness of the reaction of iron with a sufficient rate of hydrogen evolution for the plant to operate is a complex problem that can not be solved only by the use of catalysts. First of all, it is necessary to provide steam access to the reacting gland and at the same time to have an acceptable volume of storage. For this purpose, it is expedient to compact the iron powder with the catalyst to a density of 4-6 g / cm 3 (which provides the necessary porosity), choosing the shape of the compressed tablets in such a way that steam access at any place of the tablet to a depth of not more than 2 mm is guaranteed. In addition, studies have shown that the rate of hydrogen evolution during the reaction is variable and decreases as the amount of unreacted iron decreases. In order to maintain the required hydrogen capacity during the entire operation cycle of the plant, separation of storage into sections can be used, and new sections can be connected in series as the hydrogen generation rate is reduced to those previously included in operation or an increase in the generation temperature from 200-300 ° C at the beginning of the process to 500-600 ° C at the end, or a combined method combining both methods, i. E. Sectional connection and an increase in temperature as the amount of unreacted iron decreases.
Analysis of the properties of the iron-vapor method of hydrogen production shows that it meets the requirements of autonomous ECs with a large cycle of functioning to a much greater extent than the methods used up to now. It ensures the safe production of hydrogen, as well as its long and safe storage. By these parameters, it is not inferior, but even surpasses the safest known way of storing hydrogen autonomous installations in intermetallides. In this case, the dispersed iron powder is one order of magnitude cheaper than sorbents of the La-Ni or Fe-Ti type, and the necessary mass and volume is much less than for these intermetallic compounds, since its mass capacity in hydrogen is about 5% against 1.5-2 %, And density in the compressed state can be 4-6 g / cm 3 . The reaction products are pure hydrogen and iron oxides, which are easily regenerated and can be repeatedly used up to 10,000 times according to the experience of industrial application. Thus, the initial product - fine iron can be incorporated into the system once for the entire life of the plant. For another initial component of the process - water, there is no need to reserve the mass and volume in the autonomous EC, since the water produced during the reaction in the ECG or other device is sufficient for these purposes.
The question of heat consumption for the production of steam necessary for the reaction is especially important. It can be shown that, taking into account the low exothermicity of reactions 1, 2, 3 and the partial use of heat released in the ECG or other device, the heat recovery of the generated hydrogen, the total amount of additional heat that must be supplied from the outside to generate steam is relatively small and may be Is compensated by burning about 10% of the hydrogen formed.
In addition, in autonomous air-independent plants, where oxygen is the required starting reagent, the latter can be stored in chemical compounds (for example, hydrogen peroxide) whose decomposition reaction is exothermic, and the heat produced during decomposition can be used to generate steam necessary for the organization of iron Steam method of hydrogen storage.
CLAIM
1. A method for producing and storing hydrogen in autonomous power plants with an electrochemical generator generating electric power and water, including air-independent ones, to produce oxygen therein by decomposition of an oxygen-containing substance, with a cycle of operation from tens to thousands of hours, mainly for submarines, Generating water vapor, passing it through a sorbent consisting of iron with a catalyst and carrying out an iron oxidation reaction, characterized in that as a sorbent, volumetric structures of 2 to 4 mm in thickness from pressed iron with a catalyst with a density of 4 to 6 g / cm 3 , located in the repositories; The oxidation reaction of the iron is carried out with increasing temperature during the process and the regeneration of the oxidized iron is carried out as part of an autonomous power plant by performing an iron reduction reaction with hydrogen, carbon monoxide or a mixture thereof.
2. A method according to claim 1, characterized in that the iron storage is divided into sections and, as the rate of hydrogen evolution is reduced in the operating sections, new sections are serially connected.
3. A method according to claim 1, characterized in that water generated from the operation of an autonomous power plant is used to generate water vapor.
4. The method according to claim 1, characterized in that the heat of the exothermic decomposition reaction of the oxygen-containing substance is used to carry out the hydrogen generation reaction in the air-independent power plants.
print version
Publication date 27.02.2007gg
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