RU2604228C1 - Method of accumulating hydrogen - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method for hydrogen accumulation and can be used in chemical industry for processing of hydrocarbon gases, as well as in transport and hydrogen technologies. Heated stream, containing water vapour and lower alkanes having one to four carbon atoms, is passed through an adiabatic reactor, filled with a nozzle of a catalyst. Then from heated stream hydrogen is extracted by diffusion through sealed metal wall into a capsule, in which hydrogen-absorbing reaction gas is fed.

EFFECT: reduced consumption of energy resources, reduced costs for pumping and losses, associated with emission of excess heat into atmosphere, low cost of production and accumulation of hydrogen.

12 cl, 1 dwg, 2 tbl, 2 ex

Description

Technical field

The invention relates to a method for the accumulation of hydrogen, hydrogen-containing products and can be used in the chemical industry for the processing of hydrocarbon gases, as well as in transport systems and hydrogen technologies.

State of the art

The prior art method for producing synthesis gas, containing mainly H ₂ and CO, described in the patent of the Russian Federation No. 2228901 for the invention, publ. 2004.05.20. The known method for producing synthesis gas includes two stages: stage A) partial oxidation and stage B) conversion of residual methane with the products of stage A) on the catalyst. Stage A) partial oxidation is carried out in two stages: a) non-catalytic partial oxidation of natural gas with oxygen to obtain in the reaction products a nonequilibrium content of H ₂ O and CH ₄ at a molar ratio of oxygen and methane of approximately 0.76-0.84, b) conversion products stage reaction a) with corrective additions of CO ₂ and H ₂ O or H ₂ O and CH ₄ to obtain a gas mixture which passes residual reforming methane with steam on a catalyst. The method allows the production of synthesis gas with a composition that corresponds to a given ratio of CO / H ₂ . The method can be used to obtain feedstock for further processes for the production of hydrogen, the synthesis of alcohols, dimethyl ether, ammonia or other large-capacity chemical products.

However, the described method has several disadvantages, which include functional and economic limitations of the application of the method associated with the need for the allocation and purification of hydrogen.

At the same time, motor transport is becoming a growing hydrogen consumption segment, in which the storage of hydrogen on board requires the creation of efficient batteries with low overall dimensions and the ability to quickly fill and empty.

The prior art method of hydrogen storage and a hydrogen storage tank (see RF patent No. 2222749 for an invention, publ. 01/27/2004), designed for a hydrogen automobile and made of durable composite relatively light materials. The last modification has a volume of 90 l, a mass of 40 kg, a hydrogen pressure of 400 atm. Estimates show that in this case 3.2 kg of hydrogen can be stored in the tank, which corresponds to a mass content of hydrogen of 8%.

The disadvantages of the technical solution are explosiveness, low hydrogen content per unit volume.

The prior art method for storing and supplying hydrogen using a fuel supply system for fuel cells of electric vehicles described in the patent of the Russian Federation No. 2233511 for the invention, publ. 07/27/2004. This system has a fuel (hydrogen) tank. To ensure the functional purpose through the nozzles, the tank is connected to other components and modules of the fuel supply system by pipelines of gas supply and selection, as well as supply and removal of the working medium of the heat exchanger, providing the given operating modes of the installation. In such a plant, a hydrogen storage filler may be used to increase the hydrogen storage density.

In particular, a hydrogen storage tank is also proposed, consisting of a sealed housing, process pipes, a heater, and a hydrogen filler-accumulator located in the housing. The hydrogen storage filler is hollow microspheres bonded together in a single rigid structure formed layer-by-layer from microspheres of different diameters. The diameter of the microspheres decreases from the central layer to the peripheral. On the outer surface of the rigid structure, a coating can be made of a metal that effectively absorbs hydrogen, for example palladium, or nickel, or an alloy of lanthanum with nickel. As the material of the microspheres, steel, or titanium, or lanthanum, or nickel, or zirconium, or alloys based on these metals or graphite, or graphite-based compositions are used. Microspheres made of metal can be fixed among themselves by diffusion welding. The invention is aimed at creating a tank for the safe storage of hydrogen, providing an increase in the mass content of hydrogen above 6% (see RF patent No. 2267694 for the invention, publ. 10.01.2006).

The disadvantage of this technology is the need to create a paired technology for the production and compression of hydrogen to fill the battery. The production of hydrogen for refueling such batteries requires capital-intensive production.

The prior art method for producing hydrogen, described in the monograph "Nuclear-technological complexes based on high-temperature reactors", A.Ya. Stolyarevsky - Moscow: Energoatomizdat, 1988. - 152 p. (ISBN 5-283-03750-9), p. 107-109. This method of technological conversion of hydrocarbon feedstock involves the multi-stage production of synthesis gas containing mainly H ₂ and CO, in which at least two successive stages are carried out, in each of which a stream containing lower alkanes having about one to four carbon atoms is passed through a heating heat exchanger, and then through an adiabatic reactor filled with a catalyst nozzle, and after the last stage, water vapor is removed from the stream.

The disadvantages of this solution are the relatively low conversion ratio of alkanes (up to 90%) and the relatively low ratio of H ₂ / CO in the synthesis gas as a product of the process, which worsens the conditions for the subsequent extraction of hydrogen from the conversion products.

Part of these problems is solved by a method that allows to increase the conversion coefficient of lower alkanes and create technological capabilities for changing the ratio of H ₂ / CO in the produced synthesis gas. In a multi-stage synthesis gas production in which at least two successive stages are carried out, in each of which a stream containing lower alkanes having approximately one to four carbon atoms is passed through a heating heat exchanger and then through an adiabatic reactor filled with a catalyst nozzle, and after the last stage, water vapor is removed from the stream, after which carbon dioxide and / or hydrogen is removed from the stream, at least part of which is directed to mixing with the stream before and / or between in tadia. The alkane conversion coefficient in this method rises above 90%, and the H ₂ / CO ratio can vary from 2 to 4 depending on the target end product (see RF patent No. 2274600 for an invention, publ. 2006.04.20 - prototype).

The disadvantage of this method is the loss of pressure and temperature in the process of hydrogen removal, which makes it difficult to efficiently accumulate it.

Disclosure of invention

The objective of the claimed invention is to provide a method with improved economic indicators of hydrogen storage and conditions for the effective use of hydrogen.

The technical result of the claimed invention is:

- reduction in energy consumption,

- reduction of pumping costs and losses associated with the release of excess heat into the atmosphere,

- reducing the cost of hydrogen storage.

The technical result is achieved in that a heated stream containing water vapor and lower alkanes having from one to four carbon atoms is passed through an adiabatic reactor filled with a catalyst nozzle, and then hydrogen is removed from the heated stream, while hydrogen is removed by diffusion through a sealed metal a wall into a capsule in which hydrogen is absorbed by the reaction gas.

In a preferred embodiment, the capsule is removable with the possibility of diffusion of hydrogen. After the adiabatic reactor, steam and carbon dioxide are removed from the heated stream. Before heating the stream, the stream is purified from sulfur compounds. After the removal of hydrogen, the cooling of the heated stream is carried out in a heat exchanger by producing water vapor. In an adiabatic reactor, a temperature is maintained in the range of 600 ° C-900 ° C. Lower alkane is methane. The flow pressure is selected in the range removed from 2.0-12.0 MPa. In a heated stream containing water vapor and lower alkanes, oxygen is obtained from the air by separation from nitrogen, which is fed to fill the capsule as a reaction gas. The capsule is filled with benzene as a reaction gas. A nuclear reactor is used as a source of water vapor. The capsule contains a hydrogen absorption catalyst.

Brief Description of the Drawings

The features and essence of the claimed invention are explained in the following detailed description, illustrated by a figure, which shows the following:

1 - lower alkanes in the form of methane;

2 - water vapor;

3 - oxygen;

4 - heated stream;

5 - adiabatic reactor;

6 - synthesis gas;

7 - hydrogen accumulator;

8 - capsule;

9 - supply of capsules;

10 - collector;

11 - capsule shipping system;

12 - hydrogen generator;

13 is hydrogen;

14 - thermal energy;

15 - heat exchanger;

16 - commercial gas;

17 - air;

18 - gas separator;

19 - nitrogen;

20 - gas filler;

21 - a nuclear reactor;

22 - steam turbine.

The implementation of the invention and examples of implementation

An example implementation of the claimed invention is the method of hydrogen storage, described below.

Example 1

In example 1 of the invention, methane is used as lower alkanes 1, water vapor, carbon dioxide and hydrogen are used as heated stream 4, methane vapor-oxygen catalytic conversion products are used in adiabatic reactor 5, nitrogen is used as reaction gas filling capsules 8 that allows you to characterize the features of the invention in relation to the processes of producing hydrogen from natural gas and the accumulation of hydrogen in the state associated with nitrogen in the form of ammonia.

The method is as follows.

Methane 1 is sent to the stage of purification from sulfur compounds (if they are contained in the form of impurities in methane) (not shown in the figure), which is carried out in two stages: first, for example, hydrogenation of organic sulfur compounds, for example mercaptans to hydrogen sulfide, is carried out on an aluminum-cobalt-molybdenum catalyst, and then the flow is directed to the absorption of the resulting hydrogen sulfide by activated zinc oxide in absorption reactors included in series or in parallel. Methane 1 purified (in terms of sulfur) to a mass concentration of sulfur less than 0.5 mg / ^Nm3 at a pressure above 6.0 MPa is mixed with pressurized steam to methane pressure 2, preheated to a temperature of about 400 ° C and the resulting gas stream fed to mixing with oxygen 3, which serves as an oxidizer of the steam mixture. As a result of oxidation, the mixture is heated to a temperature of about 1200 ° C and forms a heated stream 4 supplied to the adiabatic reactor 5 filled with a catalyst nozzle, for which, for example, it is preferable to use a NIAP-03-01 nickel catalyst. Catalysts based on other active metals selected from the group of rhodium, platinum, iridium, palladium, iron, cobalt, rhenium, ruthenium, copper, zinc, iron, their mixtures or compounds can also be used. The composition of the catalyst with a change in the content of platinoids, as well as metals that affect the kinetics of the oxidation of carbon monoxide by water vapor (shear reaction) will allow you to control the content of hydrogen and CO in the commodity gas 16. The resulting synthesis gas is sent to a hydrogen accumulator 7, in which capsules 8 are placed, filled with reaction nitrogen to a pressure of 1.1-1.2 MPa. Due to the diffusion of hydrogen through the walls of the capsules 8, hydrogen enters the capsules 8 and is absorbed due to the reaction of synthesis of ammonia from a nitrogen-hydrogen mixture: 3 Н ₂ + N ₂ ↔ ₂ NH ₃ . The reaction temperature is maintained at 350-400 ° C due to heat removal, for example, to boiling water (not shown in the figure). Then, the capsules 8 are additionally cooled, for example, by the water supplied to the hydrogen accumulator 7, to ambient temperature, during which ammonia condensates and the pressure drops in the capsules 8, which are sent to the collector 10 by the capsule supply system 9, from which the capsule dispatch system 11 sends them sent to a hydrogen generator 12, from which hydrogen 13 is supplied to its final consumer. In the hydrogen generator 12, hydrogen 13 is released from the capsules 8 when they are heated with thermal energy 14 due to the thermolysis of ammonia and subsequent diffusion of hydrogen 13 through the walls of the capsules 8. Hydrogen generator 12 can be placed on board the vehicle and thermal energy 14 can be supplied by cooling the products combustion of hydrogen 13 in the engine of the vehicle. Commodity gas 16 is removed from the hydrogen accumulator 7, which is cooled in the heat exchanger 15 before being discharged to a subsequent utilization system, which can serve as power plants, methanol synthesis units, and other chemical consumers. At the same time, CO ₂ can be removed from the commercial gas 16 in absorption purification, for example, with an aqueous solution of activated mono- and diethanolamine. To obtain nitrogen 19, which is used as a reaction gas, and oxygen 3, air 17 is used, from which nitrogen 19 is separated in a gas separator 18 and sent to a gas filler 20, in which capsules 8 are filled with nitrogen 19, which are then sent to a hydrogen accumulator 7, which also can also be sent capsules 8, freed from hydrogen 13 in the hydrogen generator 12.

To obtain high pressure water vapor 2, a nuclear reactor 21 can be used, the parameters of which allow generating steam with a pressure of 9-13 MPa, which allows part of the energy of water vapor 2 to be generated on a steam turbine 22 in order to generate electricity, some of which can be sent to the gas separator 18 to obtain from the air 17 nitrogen 19 and oxygen 3.

At the outlet of the adiabatic reactor 5, the synthesis gas has the composition shown in table 1.

Thus, in a hydrogen accumulator 7, in which capsules 8 are placed, filled with nitrogen to a pressure of 1.1-1.2 MPa, a medium with a high (over 3.7 MPa) hydrogen partial pressure is created, which allows efficient filling of the capsules 8 with hydrogen. Hydrogen has a very high diffusion permeability. The material of the capsules 8 is selected from metals having good hydrogen solubility. The uniqueness of hydrogen lies primarily in its anomalously high mobility in metals, which is even higher at room temperature than nitrogen (the diffusion coefficient of hydrogen is 10 ¹² times higher than that of C or N). The diffusion coefficient of hydrogen in iron at 25 ° С D _H = 7 × 10 ^-5 cm ² / s - i.e. its penetration is about 1 mm in 3 minutes. Metal defects hold hydrogen for a very long time in a metal at its concentration 3 orders of magnitude higher than equilibrium.

In iron-based alloys, the solubility of hydrogen and the diffusion coefficient depend on the concentration of carbon, alloying elements, impurities and the structural state of the metal or alloy. For example, for St3sp steel, the diffusion coefficient is 1.499 × 10 ^-4 cm ² / s, and for steel 14Kh2GMR - 4.442 × 10 ^-4 cm ² / s. It is known that with an increase in the concentration of carbon, silicon, aluminum, chromium, tungsten, boron in the alloy, the solubility of hydrogen in the metal decreases, and when alloyed with titanium, niobium, etc. it increases. All alloying elements that slow down the diffusion of hydrogen simultaneously reduce the rate of its removal from the metal, while elements that increase the solubility of hydrogen (titanium, niobium, neodymium, zirconium, thorium, cerium, lanthanum, tantalum, vanadium up to 6%) and form Compounds with hydrogen that are durable at low temperatures accelerate the removal of hydrogen.

The solubility of hydrogen in a solid metal is determined by the crystalline structure of the metal. It is known that a-iron (ferrite) is more permeable to hydrogen than g-iron (austenite), although its solubility in g-iron is also large. The largest amount of hydrogen dissolves in austenite, which is explained by the large size of the cavities in the face-centered lattice, compared with a metal with a bcc lattice. Dissolving in the ferrite component of the metal, hydrogen causes an increase in its volume by 1.75 cm ³ / mol.

Inside capsules 8, hydrogen, having passed through the metal wall, reacts with the synthesis of ammonia with reaction nitrogen filling the volume of capsule 8. The content of H ₂ in ammonia exceeds the content of H ₂ in metal hydrides by about an order of magnitude and is about 18%.

The synthesis of ammonia, based on the interaction of reaction nitrogen and hydrogen, can be carried out inside capsules 8 at elevated temperatures and pressures using a ruthenium catalyst at a pressure of 0.6-30.0 MPa, a temperature of 300-500 ° C.

The catalyst can be used as active components, for example, Fe and oxides of K, Ca, Al (such as, for example, FNMS Montecatini-Edison catalyst), described in RF patent 2241667, publ. 12/10/2004. In this case, as the experiment showed, the equilibrium in the synthesis reaction reaches its greatest degree at a temperature of 373 ° C, table 2.

Possible reaction conditions for the synthesis of ammonia and the composition of the reaction mixture in capsule 8 are presented in table 2.

Catalysts may be used to accelerate the reaction in capsule 8.

In the collector 10, the capsules are finally cooled to ambient temperature, which leads to the condensation of ammonia and a decrease in pressure in the capsule 8. The reduced pressure allows the capsules to be created 8 thin-walled, which reduces their weight and size characteristics, reduces the cost and speeds up the process of filling capsules 8 in the hydrogen accumulator 7 and hydrogen production 13 in a hydrogen generator 12.

In the hydrogen generator 12, hydrogen 13 is released from the capsules 8 when they are heated with thermal energy 14 due to thermolysis (cracking) of ammonia and subsequent diffusion of hydrogen 13 through the walls of the capsules 8. Ammonia contains approximately 1.7 times more hydrogen compared to liquid hydrogen per unit volume, thereby allowing more efficient transportation of hydrogen fuel. Thermolysis (cracking) of ammonia in the capsule 8 can be conducted according to the reaction: 2NH ₃ → 3H ₂ + N _2.

Catalysts can be used to accelerate the thermolysis reaction, for example, involving contacting the catalyst for ammonia cracking with ammonia under conditions effective to create nitrogen and hydrogen 13, the ammonia cracking catalyst contains (1) an alloy having the general formula Zr _1-x Ti _x M ₁ M _2, wherein M ₁ and M ₂ are selected independently from the group consisting of Cr, Mn, Fe, Co and Ni, and x has a value between 0.0 and 1.0 inclusive, and (2) between about 20 and 50 % by weight of Al, as described in RF patent No. 2173295, publ. 09/10/2001. Such catalysts allow thermolysis of ammonia to 95% or more.

Filling the capsules with nitrogen 19 is carried out in a gas filler 20. For this purpose, the capsules 8 can be made using technical solutions described, for example, in patent RU 2171765, publ. 08/10/2001, or in patent RU 2173661, publ. 09/20/2001. In particular, the sealing of the outlet channel of the capsule 8 can be made in the form of a valve equipped with an elastic element that opens the release of gas from the capsule 8 only when the pressure inside the capsule 8 exceeds the pressure of the medium surrounding the capsule by a predetermined amount. The capsule body 8 may be made in the form of a cylinder connected from two or more parts. The valve of the capsule 8 can be placed at the junction of the parts of the body. The outlet channel of the capsule 8 may be equipped with a pressure valve with a spring-loaded movable element in the form of a sleeve or a rod, made with the possibility of tight connection of the capsule 8 and the housing of the hydrogen generator 12 and the passage of gas from the capsule 8 into the hydrogen housing 12 by pressing the spring-loaded movable element. In this case, a diffusion separator of hydrogen inside the capsule 8 should be provided.

Example 2

In example 2 of the invention, the reaction gas used is not nitrogen, as in the first example, but benzene, possibly in a mixture with other aromatic hydrocarbons. In this case, hydrogen accumulation is carried out in the form of cyclohexane, which is formed during the hydrogenation of benzene inside capsules 8 placed in a hydrogen accumulator 7 filled with heated synthesis gas 6. Cyclohexane C ₆ H ₁₂ (liquid with a boiling point of 80.7 ° C) inside the capsules 8 when cooled in the collector 10 condenses, which allows the use of thin-walled capsules 8.

Hydrogenation of benzene inside the capsules 8 proceeds with the release of heat (ΔН = -49 kcal). Hydrogenation of benzene is carried out both at a low partial pressure of hydrogen in the synthesis gas 6, and at medium and high pressure. Apparently, the process is most advantageous in terms of technology and technology at high pressure: up to 20-30 MPa and at a temperature of 260-360 ° C. At lower temperatures, the equilibrium of the reversible reaction shifts to the right, but the rate of the binding reaction of hydrogen diffused into the capsule 8 in the catalytic hydrogenation of aromatic hydrocarbons significantly decreases: C ₆ H ₅ R + 3H ₂ = C ₆ H ₁₁ R, where R = H, CH ₃ , C ₂ H _5, C ₃ H _7.

As a rule, the molar ratio of hydrogen to benzene in the initial reaction mixture can be from 3: 1 to 15: 1, preferably 10: 1 when using a hydrogenation catalyst, which, as a rule, is a metal of group VIII of the Periodic table of elements as the main the catalyst component individually or together with promoters and modifiers such as palladium / gold, palladium / silver, cobalt / zirconium, nickel, preferably deposited on a carrier such as alumina, carbon, silicon dioxide and the like. (RF patent No. 2235086, publ. 08/27/2004). As shown experimentally, the use of the Crosfield NTS-400 catalyst (12% nickel on alumina) allows one to achieve a cyclohexane synthesis depth of 99% by mass.

In hydrogen generator 12, hydrogen 13 is released from capsules 8 when they are heated with thermal energy due to the release of bound hydrogen in the catalytic dehydrogenation reaction of cyclohexane hydrocarbons contained in capsule 8: C ₆ H ₁₁ R = C ₆ H ₅ R + 3Н ₂ , where R = Н , CH ₃ , C ₂ H ₅ , C ₃ H ₇ in the presence of catalysts containing platinum group metal (s). The reaction is carried out at high space velocities in the temperature range 300-500 ° C, as described in RF patent No. 2160698, publ. 12/10/2000. The use of industrial platinum catalysts, for example, a catalytic reforming process, for carrying out this reaction provides a selectivity of the dehydrogenation of naphthenic hydrocarbons close to 100 mol. % This circumstance is a prerequisite for the production of high purity hydrogen (> 99 mol.%). Capsules 8, freed of hydrogen 13 in the hydrogen generator 12 by the capsule 11 dispatch system, are returned to the collector 10, where, by supplying the capsules 9 to the hydrogen accumulator 7, the capsules 8 are sent to re-absorb hydrogen by the reaction gas.

Thus, this method will create the conditions for an effective increase in the utilization of energy resources with the ability to maintain reduced energy consumption, reduce pumping costs and losses associated with the release of excess heat into the atmosphere, improve the economic indicators of hydrogen storage, and create conditions for the efficient use of hydrogen.

Claims (12)

1. A method of accumulating hydrogen, in which a heated stream containing water vapor and lower alkanes having from one to four carbon atoms is passed through an adiabatic reactor filled with a catalyst nozzle, and then hydrogen is removed from the stream, characterized in that hydrogen is removed by diffusion through a sealed metal wall into a capsule in which hydrogen is absorbed by the reaction gas. 2. The method according to p. 1, characterized in that the capsule is removable with the possibility of diffusion of hydrogen. 3. The method according to p. 1, characterized in that after the adiabatic reactor water vapor and carbon dioxide are removed from the stream. 4. The method according to p. 1, characterized in that before heating the stream, the stream is purified from sulfur compounds. 5. The method according to p. 1, characterized in that after the removal of hydrogen, the flow is cooled in the heat exchanger due to the production of water vapor. 6. The method according to p. 1, characterized in that in the adiabatic reactor maintain a temperature in the range of 600 ° C-900 ° C. 7. The method according to p. 1, characterized in that the lower alkane is methane. 8. The method according to p. 1, characterized in that the flow pressure is selected in the range of 2.0 -12.0 MPa. 9. The method according to p. 1, characterized in that in the heated stream containing water vapor and lower alkanes, oxygen is supplied from the air by separation from nitrogen, which is fed to fill the capsule as a reaction gas. 10. The method according to p. 1, characterized in that the capsule is filled with benzene as a reaction gas. 11. The method according to p. 1, characterized in that a nuclear reactor is used as a source of water vapor. 12. The method according to p. 1, characterized in that the capsule contains a hydrogen absorption catalyst.

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