Hydrogen storage system and hydrogen storage method

Abstract

The invention provides a hydrogen storage system and a hydrogen storage method, and belongs to the technical field of green hydrogen storage. The hydrogen storage system comprises an energy conversion unit suitable for converting solar energy and / or wind energy into electric energy; the water electrolysis hydrogen production unit is suitable for preparing hydrogen in a water electrolysis mode by utilizing the electric energy output by the energy conversion unit; and the methane synthesis unit is communicated with the water electrolysis hydrogen production unit and is suitable for enabling the hydrogen from the water electrolysis hydrogen production unit to react with the introduced coke and obtaining a mixed gas containing methane, so that the chemical energy of the hydrogen is transferred into the methane to be stored. According to the invention, coke is used as a medium for hydrogen storage and transportation, and the coke is consumed through green hydrogen, so that methane with high added value is produced, and the problems of high cost, poor safety and the like in hydrogen storage and transportation are solved.

Description

Technical Field

[0001] This invention relates to the field of green hydrogen storage technology, and more particularly to a hydrogen storage system and a method for storing hydrogen. Background Technology

[0002] Building a clean, low-carbon, safe, and efficient new energy system requires vigorous development of renewable and clean energy, especially in remote areas such as Xinjiang, by accelerating the construction of new energy bases in desert areas and coordinating the local production and transmission of clean energy.

[0003] Hydrogen is an important component of clean energy. However, due to its small atomic radius, hydrogen can easily pass through the molecular gaps in steel. This is especially true under high-pressure gaseous hydrogen storage conditions, which can easily lead to leaks during storage, necessitating improvements in safety.

[0004] Especially for regions like Xinjiang in western China, hydrogen storage at the "Shagohuang" new energy base requires investment in infrastructure such as large-capacity compressors and high-pressure hydrogen storage tanks, resulting in high energy consumption and high hydrogen storage costs. Summary of the Invention

[0005] To at least partially solve the aforementioned technical problems, the present invention provides a hydrogen storage system and a method for storing hydrogen.

[0006] According to one embodiment of the present invention, a hydrogen storage system is provided, comprising: an energy conversion unit adapted to convert solar and / or wind energy into electrical energy; a water electrolysis hydrogen production unit adapted to use the electrical energy output from the energy conversion unit to produce hydrogen gas by water electrolysis; and a methane synthesis unit connected to the water electrolysis hydrogen production unit, adapted to react hydrogen gas from the water electrolysis hydrogen production unit with introduced coke to obtain a mixed gas containing methane, thereby realizing the transfer of the chemical energy of hydrogen gas to methane for storage.

[0007] In some embodiments, the hydrogen storage system further includes a coal pyrolysis unit connected to a methane synthesis unit, the coal pyrolysis unit being adapted to provide coke to the methane synthesis unit.

[0008] In some embodiments, the coal pyrolysis unit includes: a coal pyrolysis furnace, suitable for pyrolyzing raw coal to obtain pyrolysis products, including coke, coke oven gas, and tar; and a combustion chamber, suitable for burning and releasing heat from the coke oven gas and tar in the pyrolysis products, and transferring the released heat to the coal pyrolysis furnace.

[0009] In some embodiments, the hydrogen storage system further includes an exhaust gas purification chamber, located downstream of the combustion chamber, suitable for recovering gaseous products from the combustion chamber.

[0010] In some embodiments, a heat exchange unit is arranged between the water electrolysis hydrogen production unit and the methane synthesis unit, and is adapted to exchange heat between the mixed gas in the first temperature range and the hydrogen gas from the water electrolysis hydrogen production unit in the second temperature range, so that the heated hydrogen gas in the third temperature range after heat exchange is input into the methane synthesis unit.

[0011] In some embodiments, the hydrogen storage system further comprises a pressure swing adsorption unit arranged downstream of the methane synthesis unit, and adapted to separate methane from the mixed gas containing methane.

[0012] According to an embodiment of another aspect of the present application, a hydrogen storage system is provided, comprising: a power conversion unit adapted to convert solar energy and / or wind energy into electric energy; a water electrolysis hydrogen production unit adapted to produce hydrogen gas by water electrolysis using the electric energy output by the power conversion unit; a coke production unit adapted to produce coke; a methane synthesis unit in communication with the water electrolysis hydrogen production unit, and adapted to react hydrogen gas from the water electrolysis hydrogen production unit with coke from the coke production unit, and obtain a mixed gas containing methane, so as to transfer chemical energy of the hydrogen gas to the methane for storage; a transport distance between the water electrolysis hydrogen production unit and the methane synthesis unit is less than or equal to a preset distance threshold.

[0013] According to an embodiment of still another aspect of the present application, a hydrogen storage method is provided, comprising: converting solar energy and / or wind energy into electric energy by means of a power conversion unit, and driving a water electrolysis hydrogen production unit to produce hydrogen gas; mixing and reacting hydrogen gas from the water electrolysis hydrogen production unit with coke input into a methane synthesis unit, and obtaining a mixed gas containing methane, so as to transfer chemical energy of the hydrogen gas to the methane for storage.

[0014] In some embodiments, the method further comprises: inputting raw coal into a coal pyrolysis unit for pyrolysis, and obtaining a mixture containing coke; the pyrolysis temperature is 800-1100℃, and the pressure is 0.1-4MPa.

[0015] In some embodiments, the coke obtained by coal pyrolysis is composed of graphite carbon with highly ordered arrangement, and has stable structure, and needs high temperature and high pressure environment to break carbon-carbon bonds, so as to promote the reaction between the coke and hydrogen gas. Therefore, the methane synthesis reaction conditions are: the reaction temperature is 500-700℃, and the reaction pressure is 0.1-4MPa.

[0016] In some embodiments, the pyrolysis comprises drying, degassing, first pyrolysis, second pyrolysis and polycondensation in sequence.

[0017] In some embodiments, the drying temperature is 10-200℃; the degassing temperature is 200-350℃; the first pyrolysis temperature is 350-550℃; the second pyrolysis temperature is 550-800℃; and the polycondensation temperature is >800℃.

[0018] The hydrogen storage system according to the embodiment of the present application realizes stable and safe storage and utilization of hydrogen by preparing the coke as a hydrogen storage and transport carrier into methane; and realizes clean and low-carbon utilization of high-carbon energy by converting the high-carbon fuel into methane with the aid of hydrogen as a coke gasification agent. The present application integrates renewable energy resources such as solar energy and wind energy, and improves the utilization rate of renewable energy by using multiple energy complementation of the energy conversion unit. The water electrolysis hydrogen production unit directly utilizes green electricity to produce hydrogen, thereby avoiding carbon emissions.

[0019] In addition, the chemical energy of hydrogen is transferred to methane for storage, which can be transmitted in a targeted manner by using the existing natural gas pipeline, thereby reducing energy consumption and hydrogen storage cost. BRIEF DESCRIPTION OF DRAWINGS

[0020] The above and other objects, features and advantages of the present application will become more apparent from the following description of embodiments of the present application taken in conjunction with the accompanying drawings, in which:

[0021] Figure 1 FIG. 1 shows a structural schematic diagram of a hydrogen storage system according to an embodiment of the present application;

[0022] Figure 2 FIG. 2 shows a structural schematic diagram of a hydrogen storage system according to another embodiment of the present application;

[0023] Figure 3 FIG. 3 shows a flowchart of a hydrogen storage method according to an embodiment of the present application;

[0024] Figure 4 FIG. 4 shows a process flowchart of hydrogen storage according to an embodiment of the present application;

[0025] Figure 5 FIG. 5 shows a coke hydrogenation fixed bed experiment measurement graph according to an embodiment of the present application;

[0026] Figure 6 FIG. 6 shows a coke hydrogenation reaction equilibrium conversion rate curve graph in a simulation process according to an embodiment of the present application.

[0027] In the drawings, the meanings of the reference signs are as follows:

[0028] 1 - energy conversion unit;

[0029] 2 - water electrolysis hydrogen production unit;

[0030] 3 - methane synthesis unit;

[0031] 4 - coal pyrolysis unit;

[0032] 41 - coal pyrolysis furnace;

[0033] 42 - combustion chamber;

[0034] 43 - tail gas purification chamber;

[0035] 44 - drying chamber;

[0036] 45 - tar storage tank;

[0037] 46 - coke oven gas storage tank;

[0038] 5 - heat exchange unit;

[0039] 6 - preheating chamber;

[0040] 7 - pressure swing adsorption unit;

[0041] 8 - coke production unit. DETAILED DESCRIPTION

[0042] Hereinafter, embodiments of the present application will be described with reference to the accompanying drawings. It should be understood, however, that the description which follows is merely illustrative and is not intended to limit the scope of the present application. In the following detailed description of embodiments of the present application, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the present application. However, it will be apparent to one skilled in the art that the embodiments of the present application can be practiced without these specific details. In other instances, well-known structures and functions have not been described in detail in order to avoid obscuring aspects of the present application.

[0043] The terms used herein are merely used to describe specific embodiments and are not intended to limit the present application. The term "include" used herein indicates the presence of a feature, step, operation, but does not exclude the presence or addition of one or more other features.

[0044] In the case of using expressions such as "at least one of A, B, and C", it should generally be interpreted to include any of one, two, or all of the items listed after the term, unless the term is clearly understood to be interpreted only in the sense of "one of A or B or C" in a context (e.g., "at least one of A, B, and C" can be interpreted as "at least one of A or B or C" in a context where two items from among A, B, and C are chosen at random). In the case of using expressions such as "at least one of A, B, or C", it should generally be interpreted to include any of one, two, or all of the items listed after the term, unless the term is clearly understood to be interpreted only in the sense of "one of A or B or C" in a context (e.g., "at least one of A, B, and C" can be interpreted as "at least one of A or B or C" in a context where two items from among A, B, and C are chosen at random).

[0045] In the present application, "Sagor" can be understood as a general term for desert, Gobi, and desert, which are regions with sparse vegetation, flying sand, and harsh climate. However, the "Sagor" region has abundant wind energy and solar energy resources.

[0046] At present, for regions such as Xinjiang, it is necessary to accelerate the construction of "shaguo barren" new energy base, and to coordinate the local consumption and external channel construction. Hydrogen is an important part of renewable clean energy, but hydrogen has a small atomic radius and is easy to leak, making it difficult to achieve safe storage. Especially in remote areas, hydrogen storage requires the construction of large-capacity compressors, high-pressure hydrogen storage tanks and other infrastructure, not only making energy consumption large, but also increasing the cost of hydrogen storage.

[0047] In the process of implementing the inventive concept, it is found that for the storage and long-distance transportation of hydrogen, the existing natural gas pipe network can be used to realize the continuous directional transportation of hydrogen by mixing hydrogen with natural gas. However, due to the hydrogen embrittlement effect of metal materials (which can be understood as the phenomenon that the mechanical properties of metal materials deteriorate significantly under the action of hydrogen, and brittle fracture occurs under the action of stress lower than the yield strength of the material), the volume ratio of hydrogen mixed with natural gas is about 10%, and such a low mixing ratio is difficult to meet the future demand for large-scale green hydrogen transmission in "shaguo barren" new energy base.

[0048] In order to solve the above problems, the electrolytic water hydrogen production unit is communicated with the methane synthesis unit, and the hydrogen produced by renewable abundant solar energy and / or wind energy is driven by electric energy to react with the coke introduced to obtain methane, and the chemical energy of hydrogen is transferred to methane for storage. By setting up, using coke as the medium for hydrogen storage and transportation, green hydrogen is converted into high value-added methane, and the problems of hydrogen storage and transportation are solved, and a new hydrogen storage and transportation device is proposed.

[0049] Specifically, according to an embodiment of one aspect of the present application, a hydrogen storage system is provided, Figure 1 The structure diagram of the hydrogen storage system of an embodiment of the present application is shown as Figure 1 As shown, the hydrogen storage system comprises an energy conversion unit 1, an electrolytic water hydrogen production unit 2 and a methane synthesis unit 3.

[0050] The energy conversion unit 1 is suitable for converting solar energy and / or wind energy into electric energy. The energy conversion unit 1 may, for example, be a unit composed of solar panels, wind turbine generators and the like. By using flat and vast land in "shaguo barren" area to layout large-scale photovoltaic array composed of solar panels and wind turbine generators, the generated electric energy can be integrated into subsequent applications to reduce unit power generation cost.

[0051] The water electrolysis hydrogen production unit 2 is adapted to produce hydrogen by water electrolysis using the electrical energy (green electricity, which can be understood as electrical energy produced with zero or close to zero carbon dioxide emissions, and the source of which is renewable energy) output by the energy conversion unit 1. The water electrolysis hydrogen production unit 2 produces hydrogen and oxygen through the electrolysis of water molecules. The water electrolysis hydrogen production unit 2 may, for example, be an alkaline electrolytic cell, a proton exchange membrane electrolytic cell or a solid oxide electrolytic cell. The reaction equation is as follows:

[0052] H2O + green electricity → H2 + 0.5O2.

[0053] Taking alkaline water electrolysis hydrogen production as an example, the structure may specifically include a cathode, an anode and a diaphragm, wherein the cathode is adapted to produce hydrogen; the anode is adapted to produce oxygen. The diaphragm is adapted to separate hydrogen and oxygen to prevent safety problems caused by mixing of the two gases, but the diaphragm can allow ions to pass through.

[0054] The type of the water electrolysis hydrogen production unit 2 is not particularly limited in the present application, and the unit can continuously produce hydrogen.

[0055] It should be noted that, taking Xinjiang and other regions as an example, the water electrolysis hydrogen production unit 2 is coupled with the energy conversion unit 1 to fully utilize the electrical energy produced by the photovoltaic and / or wind power generation in the "sand and go barren" region with abundant reserves and low cost, and then drive the water electrolysis hydrogen production, thereby reducing the unit production cost of hydrogen.

[0056] The methane synthesis unit 3 is in communication with the water electrolysis hydrogen production unit 2, and the methane synthesis unit 3 is adapted to react hydrogen from the water electrolysis hydrogen production unit 2 with the incoming coke to obtain a mixed gas containing methane, so as to realize the transfer of the chemical energy of hydrogen to methane for storage. The methane synthesis unit 3 may, for example, include a fixed bed reactor or a fluidized bed reactor. The fixed bed reactor includes a shell which can be cylindrical, and the shell is filled with a catalyst such as nickel and / or alumina. The fluidized bed reactor can be provided with a gas distribution plate to make the incoming coke in a fluidized state, so that the hydrogen and the coke are more fully contacted. The reaction process of methane synthesis is as follows:

[0057] C (s) + 2H2→ CH4, wherein C (s) represents coke.

[0058] According to the embodiments of the present application, by the synergistic operation of the energy conversion unit 1, the water electrolysis hydrogen production unit 2 and the methane synthesis unit 3, a renewable energy power generation-green hydrogen production-methane storage system is formed, the supply of green electricity is flexibly adjusted by the water electrolysis hydrogen production unit 2, a buffer is provided for renewable energy, and the energy utilization rate is improved. By transferring the chemical energy of hydrogen to methane for storage, a stable energy carrier is formed.

[0059] Especially in the process of hydrogen storage and long-distance transportation, the chemical energy of hydrogen is converted into methane for storage, which can be transmitted by existing natural gas pipelines, helping to achieve long-distance, safe, large-scale and continuous transportation, improve the safety of hydrogen storage and transportation process, reduce costs while realizing clean and low-carbon utilization of high-carbon energy (coke). The rich renewable energy resources are converted into scarce natural gas resources, ensuring energy security.

[0060] In some embodiments, the hydrogen storage system further comprises: a coal pyrolysis unit 4. The coal pyrolysis unit 4 is in communication with the methane synthesis unit 3, and the coal pyrolysis unit 4 is suitable for providing coke for the methane synthesis unit 3. It can be understood that the western region of China has rich coal resources due to the remote distribution of energy resources. More coke is prepared by coal pyrolysis, and the main application field of coke is in the steel smelting industry. In recent years, due to the downward demand for steel and the low-carbon transformation of the metallurgical industry, the demand for coke, the product of coal pyrolysis, is relatively low. The present application combines green hydrogen production with coal pyrolysis process, and uses the main product coke prepared by coal pyrolysis as the medium for hydrogen storage and transmission. On the other hand, by consuming coke with green hydrogen, high-value natural gas is produced, while solving the problems of hydrogen storage and transportation and clean utilization of coal.

[0061] It can be understood that coal pyrolysis refers to the process of heating raw coal under the condition of air isolation.

[0062] In some embodiments, the coal pyrolysis unit 4 comprises: a coal pyrolysis furnace 41 and a combustion chamber 42. The coal pyrolysis furnace 41 is suitable for pyrolyzing raw coal to obtain pyrolysis products, including coke, coke oven gas, and tar. The coal pyrolysis furnace 41 comprises a furnace body, a feeding and discharging device, a heating and temperature measuring device. The furnace body can be built with high-temperature resistant alloy or refractory bricks, and the shape of the furnace body can be cylindrical or rectangular, which is not particularly limited in the present application. The inner wall of the coal pyrolysis furnace 41 is lined with heat insulation materials such as ceramic fiber as needed to reduce heat loss. According to different pyrolysis processes, it can be divided into fixed bed, fluidized bed, rotary kiln, etc., and the specific structure of the coal pyrolysis furnace 41 is not particularly limited in the present application. The feeding port of the coal pyrolysis furnace 41 can be provided with a sealing device to prevent air from entering the furnace, and the discharging port corresponds to the collection device of coke and tar. The outer part of the furnace body of the coal pyrolysis furnace 41 can be provided with a heating jacket or a heat conducting oil pipe arranged inside the furnace body, connected with the heat transfer medium (such as high-temperature flue gas or heat conducting oil) of the combustion chamber. The furnace body can also be provided with a thermocouple as needed for real-time monitoring of the pyrolysis temperature.

[0063] In some embodiments, the combustion chamber 42 is adapted to combust and release heat from coke oven gas and tar derived from pyrolysis products, and to transfer the released heat to the coal pyrolysis furnace 41. The combustion chamber 42 may be constructed of refractory materials (e.g., corundum bricks, silicon carbide), with a streamlined inner wall to optimize flue gas flow. A burner, such as a perforated gas nozzle, is installed within the combustion chamber 42 to facilitate uniform injection of coke oven gas and tar. A blower may also be installed at the air inlet of the combustion chamber 42 to provide the air required for combustion.

[0064] In some embodiments, the combustion chamber 42 and the coal pyrolysis furnace 41 are connected by a heat exchanger (not shown in the figure). The heat exchanger can be a tubular heat exchanger, a radiant wall, etc. The high-temperature flue gas generated in the combustion chamber 42 transfers heat to the furnace wall of the coal pyrolysis furnace 41 through radiation and convection. Alternatively, a heat transfer oil circulation pipe can be used as the heat transfer medium between the combustion chamber 42 and the coal pyrolysis furnace 41. This invention does not impose any particular limitation on this method.

[0065] In some embodiments, the coal pyrolysis unit 4 further includes a tail gas purification chamber 43. The tail gas purification chamber 43 is located downstream of the combustion chamber 42 and is suitable for recovering the gaseous products (flue gas) from the combustion chamber 42. The tail gas is discharged after being rendered harmless and carbon captured by the tail gas purification chamber 43, and the non-solid products that are not burned as fuel are collected as products after cooling and purification.

[0066] In some embodiments, the exhaust gas purification chamber 43 includes a scrubbing tower, a dust collector, and a desulfurization and denitrification device. The scrubbing tower can be a packed or plate type, suitable for removing tar mist and water-soluble gases. The dust collector is suitable for removing ash and other components from the flue gas. The desulfurization and denitrification device is suitable for removing SO2 and NO from the exhaust gas. x ...etc., so that the exhaust gas produced by pyrolysis meets the emission standards.

[0067] In some embodiments, the coal pyrolysis unit 4 further includes a drying chamber 44. The raw coal is dried in the drying chamber 44 to remove free and adsorbed moisture and to generate a small amount of low-boiling-point gas (carbon dioxide) to facilitate the subsequent pyrolysis process.

[0068] The drying chamber 44 can be made of materials such as high-temperature resistant stainless steel, and can be of the drum type, fluidized bed type, or airflow type. The heat source for the drying chamber 44 comes from the waste heat of the combustion chamber 42, such as high-temperature flue gas or a separately installed gas or oil heater, heated by a jacket, built-in tube bundle, or direct introduction of hot air. The drying chamber 44 also includes a feeder, such as a screw feeder or belt conveyor, equipped with a dispersant to prevent raw coal from caking. The discharge end of the drying chamber 44 is connected to screening equipment to separate the dried coal particles and fine powder. The drying chamber 44 is suitable for reducing the moisture content in raw coal, preventing moisture from vaporizing and consuming heat in the coal pyrolysis furnace 41, thereby improving pyrolysis efficiency.

[0069] In some embodiments, the coal pyrolysis unit 4 further comprises a tar storage tank 45 and a coke oven gas storage tank 46. The tar storage tank 45 is used to store the tar that is not combusted as fuel. The coke oven gas storage tank 46 is used to store the coke oven gas that is not combusted as fuel.

[0070] In some embodiments, a heat exchange unit 5 is arranged between the water electrolysis unit 2 and the methane synthesis unit 3, which is adapted to exchange heat between the mixed gas in the first temperature range and the hydrogen gas in the second temperature range from the water electrolysis unit 2, so that the heated hydrogen gas in the third temperature range after heat exchange is input into the methane synthesis unit 3. In this way, the heat is recovered and reused, the reaction efficiency of methane synthesis is ensured, and the reaction energy consumption is reduced.

[0071] It should be noted that the temperature in the third temperature range is higher than that in the second temperature range.

[0072] Further, the first temperature range of the mixed gas from the methane synthesis unit 3 can be 400-500℃; the second temperature range of the hydrogen gas from the water electrolysis unit 2 can be 40-80℃; and the temperature of the heated hydrogen gas in the third temperature range after heat exchange can be 200-300℃.

[0073] In some embodiments, the hydrogen storage system further comprises a preheating chamber 6, in which the hydrogen gas in the second temperature range from the water electrolysis unit 2 is located, and after being heated by the heat exchange unit 5, the hydrogen gas in the second temperature range is heated to the third temperature range.

[0074] In some embodiments, the hydrogen storage system further comprises a pressure swing adsorption unit 7. The pressure swing adsorption unit 7 is located downstream of the methane synthesis unit 3 and is adapted to separate methane from the mixed gas containing methane. The pressure swing adsorption unit 7 may, for example, comprise an adsorption stage and a desorption stage. In the adsorption stage, for example, under a pressure of 0.5-1 MPa, the adsorbent preferentially adsorbs gases with large molecular weights, while hydrogen molecules are small and can pass through the adsorbent. In the desorption stage, for example, the pressure is reduced to normal pressure, and the adsorbent releases the gas mainly containing methane. The methane gas treated by the pressure swing adsorption unit 7 meets the natural gas standard in GB / T38507-2020 and can be directly used for natural gas pipeline transportation.

[0075] It should be noted that the gas pressure at the outlet of the methane synthesis unit 3 is usually consistent with the pressure in the adsorption stage, and the pressure swing adsorption unit 7 can directly adsorb without additional compression.

[0076] In some embodiments, the hydrogen storage system further comprises a pulverizer (not shown in the figure). The pulverizer is used to granulate and pulverize the large chunks of coke produced by the coal pyrolysis, thereby increasing the contact area between the coke and the hydrogen gas and facilitating the reaction between the two.

[0077] It is understood that the hydrogen storage system of the present application further comprises necessary gas pipelines, valves and other connecting and control components, which are not described in detail as they are not the focus of the present application.

[0078] In one specific embodiment, the hydrogen storage process is as follows:

[0079] The solar energy and / or wind energy is converted into green electricity by the energy conversion unit 1, and the green electricity is used to drive the electrolysis of water to produce hydrogen unit 2, thereby producing hydrogen gas and byproduct oxygen.

[0080] The raw coal is dried in the drying chamber 44, and then pyrolyzed in the coal pyrolysis furnace 41 to produce pyrolysis products.

[0081] The coke oven gas and tar in the pyrolysis products enter the combustion chamber 42, and are combusted using the byproduct oxygen produced by the electrolysis process or air to provide heat to drive the pyrolysis reaction in the coal pyrolysis furnace 41. The flue gas after combustion is purified in the tail gas purification chamber 44 to remove harmful substances and then discharged. The tar not used for combustion is stored in the tar storage tank 45. The coke oven gas not used for combustion is stored in the coke oven gas storage tank 46.

[0082] The coke in the pyrolysis products and the hydrogen produced by the electrolysis of water react in the methane synthesis unit 3 to produce a mixed gas containing methane. The sensible heat of the product is used to preheat the hydrogen gas entering the methane synthesis unit 3. The mixed gas containing methane is separated in the pressure swing adsorption unit 7 to obtain methane gas, which is then stored and transported through the natural gas pipeline network.

[0083] According to another aspect of the present application, a hydrogen storage system is provided, Figure 2 The structure of the hydrogen storage system according to another embodiment of the present application is shown in the figure. As shown in the figure, Figure 2 The hydrogen storage system comprises an energy conversion unit 1 adapted to convert solar energy and / or wind energy into electrical energy; an electrolysis of water to produce hydrogen unit 2 adapted to use the electrical energy output by the energy conversion unit 1 to produce hydrogen gas by water electrolysis; a coke production unit 8 adapted to produce coke; and a methane synthesis unit 3 in communication with the electrolysis of water to produce hydrogen unit 2 and adapted to react the hydrogen gas from the electrolysis of water to produce hydrogen unit 2 with the coke from the coke production unit 8, and obtain a mixed gas containing methane, so as to transfer the chemical energy of the hydrogen gas to the methane for storage.

[0084] It can be understood that the coke in the coke production unit 8 herein can be prepared by a coal pyrolysis reaction, can be prepared by, for example, biomass, and can also be obtained from by-products of the petroleum industry, and the source of the coke is not particularly limited herein.

[0085] It should be noted that the transport distance between the water electrolysis hydrogen production unit 2 and the methane synthesis unit 3 is less than or equal to a preset distance threshold, which is 100 kilometers, and the transport distance of the two is set in the above range, which can realize the dispersed distribution between the water electrolysis hydrogen production unit 2 and the methane synthesis unit 3, and considering the safety and cost of hydrogen transport, and considering the utilization of by-product pure oxygen in the water electrolysis process. By setting this way, only the methane synthesis unit 3 needs to be built, and the energy conversion unit 1, the water electrolysis hydrogen production unit 2, the coke production unit 8 and the natural gas pipeline network only need to use the existing devices, thereby further reducing the cost.

[0086] In some embodiments, the coke produced by the coke production unit 8 can be transported to the vicinity of the methane synthesis unit 3 by a transportation device. Of course, the coke production unit 8 can also use an existing coking coal chemical plant.

[0087] It should be noted that the energy conversion unit 1, the water electrolysis hydrogen production unit 2 and the methane synthesis unit 3 herein are consistent with the foregoing, and will not be described here.

[0088] According to another aspect of the embodiments of the present application, a hydrogen storage method is provided, Figure 3 A flow chart of the hydrogen storage method according to the embodiments of the present application is shown in FIG. 1. Figure 3 As shown in the figure, the method comprises operations S301-S302.

[0089] In operation S301, solar energy and / or wind energy is converted into electric energy by means of the energy conversion unit 1, which drives the water electrolysis hydrogen production unit 2 to produce hydrogen.

[0090] According to the embodiments of the present application, solar energy generates renewable green electricity through the energy conversion unit 1 (photovoltaic cell), and wind energy generates renewable green electricity through the energy conversion unit 1 (wind power device), and the renewable green electricity is used to drive the water electrolysis hydrogen production unit 2 to produce hydrogen and by-product oxygen. The specific reaction process is as previously described and will not be described here.

[0091] In operation S302, the hydrogen from the water electrolysis hydrogen production unit 2 and the incoming coke are mixed and reacted in the methane synthesis unit 3 to produce a mixed gas containing methane, so as to transfer the chemical energy of the hydrogen to the methane for storage.

[0092] According to the embodiment of the present application, the coke can be directly or granulated and powdered, and then reacted with hydrogen to synthesize methane in the methane synthesis unit 3. Since the reaction process is a molecular weight reduction reaction, appropriately increasing the pressure is beneficial to promoting the reaction.

[0093] According to the embodiment of the present application, the coke is used as a storage and transport carrier of hydrogen, so that the safe, stable, long-distance and large-scale transportation of hydrogen is realized. In addition, the hydrogen is used as a gasification agent of coke to convert high-carbon fuel into methane, so that the clean and low-carbon utilization of high-carbon energy is realized. At the same time, the abundant renewable resources in Xinjiang and other regions are converted into the scarce natural gas resources, which is beneficial to relieving the application gap pressure of natural gas and ensuring the safety and stability of hydrogen transportation.

[0094] In some embodiments, the method for storing hydrogen further comprises: passing raw coal into the coal pyrolysis unit 4 for pyrolysis to prepare a mixture containing coke. The source of the coke can rely on the pyrolysis process of the coal pyrolysis unit 4, and the coke of the coal pyrolysis unit 4 can be granulated or powdered as needed to make the gas-solid contact of the coke and hydrogen more sufficient.

[0095] In some embodiments, the temperature of pyrolysis is 800-1100℃, and the pressure is 0.1-4MPa. It can be understood that the coal pyrolysis reaction is an endothermic reaction at high temperature, and the combustion reaction of coke oven gas and tar in the pyrolysis product can be used to provide reaction heat for the coal pyrolysis process as needed.

[0096] In some embodiments, the combustion of coke oven gas and tar in the combustion chamber 42 can use the byproduct oxygen of the water electrolysis unit 2 for pure oxygen combustion or use air for combustion, and a tail gas purification chamber 43 is selectively arranged downstream to collect the non-solid products that are not used as fuel after cooling and purification as products.

[0097] Alternatively, the temperature of pyrolysis can be, for example, 800℃, 900℃, 1000℃ or 1100℃, or a range consisting of any two of the aforementioned values.

[0098] Alternatively, the pressure of pyrolysis can be, for example, 0.1MPa, 1MPa, 2MPa, 3MPa or 4MPa, or a range consisting of any two of the aforementioned values.

[0099] In some embodiments, the reaction conditions of the mixing reaction in the methane synthesis unit 3 are: the reaction temperature is 500-700℃, and the reaction pressure is 0.1-4MPa. The synthesis of methane is an exothermic process, and the high-temperature environment required for the reaction can be maintained by the sensible heat of the coke obtained from the coal pyrolysis process and the heat of reaction of methane synthesis, or by burning hydrogen, coke or using concentrated solar energy for heat collection.

[0100] Optionally, the reaction temperature may be, for example, 500℃, 550℃, 600℃, 650℃ or 700℃, or a range consisting of any two of the aforementioned values.

[0101] Optionally, the reaction pressure may be, for example, 0.1MPa, 1MPa, 2MPa, 3MPa or 4MPa, or a range consisting of any two of the aforementioned values.

[0102] It should be noted that, in order to improve the yield of methane, the reaction pressure can be further adjusted to 2-4MPa as needed.

[0103] In addition, the methane-containing mixed gas obtained at the outlet of the methane synthesis unit 3, which contains unreacted hydrogen, is subjected to the action of the pressure swing adsorption unit 7 to obtain methane and hydrogen with high purity (more than 80%). The methane as a hydrogen storage product is transported through a natural gas pipeline, so that the hydrogen is transported remotely, safely, on a large scale and continuously. The unreacted hydrogen separated can be recycled back to the methane synthesis unit 3 to participate in the reaction again.

[0104] In some embodiments, the sensible heat carried by the methane-containing mixed gas at the outlet of the methane synthesis unit 3 can be used to preheat the hydrogen at the inlet of the methane synthesis unit 3, further improving the heat utilization efficiency.

[0105] In some embodiments, the pyrolysis includes drying, degassing, first pyrolysis, second pyrolysis and polycondensation in sequence. The drying is used to remove free and adsorbed water in the raw coal, and a small amount of low-boiling-point gas (such as CO2) is generated. The degassing is used to break the hydrogen bond, part of the oxygen-containing functional groups and other weak bonds in the raw coal, to generate CO2, CO, CH4 and a small amount of tar. The first pyrolysis is used to release a large amount of volatile matter in the raw coal to generate CH4, C2H6, H2, CO and the like, and the tar yield reaches a peak, and the residual solid gradually becomes carbon-rich to form semi-coke particles. The second pyrolysis is used to increase the proportion of H2 in the gas-phase product, and the tar yield decreases, and the semi-coke particle porosity increases. The polycondensation is used to make the semi-coke particle deeply carbonized to high-temperature coke, and the oxygen, nitrogen, sulfur and other components in the raw coal are nearly completely removed, and the gaseous product is mainly H2.

[0106] In some embodiments, the temperature of the drying is 10-200℃; the temperature of the degassing is 200-350℃; the temperature of the first pyrolysis is 350-550℃; the temperature of the second pyrolysis is 550-800℃; and the temperature of the polycondensation is >800℃. Such settings can help to improve the efficiency of coal pyrolysis and promote the generation of coke.

[0107] Figure 4 A process flow diagram of hydrogen storage according to an embodiment of the present application is shown. As shown in FIG. 1, the process flow diagram of hydrogen storage includes the following steps: Figure 1 and Figure 4As shown, the hydrogen storage system mainly includes: an energy conversion unit 1 for converting solar energy and wind energy into green electricity; an electrolytic water hydrogen production unit 2 for converting green electricity into green hydrogen; a drying chamber 44 for desulfurizing and denitrating raw coal and reducing ash by washing and selecting; a coal pyrolysis furnace 41 for producing coke, coke oven gas and tar from the dried coal; a combustion chamber 42 for burning part of the coke oven gas and tar to provide heat for the coal pyrolysis furnace 41; an exhaust gas purification chamber 43 for treating the flue gas discharged from the combustion chamber 42, purifying the tail gas and capturing carbon; a tar storage tank 45 for storing the tar that is not burned as fuel; a coke oven gas storage tank 46 for storing the coke oven gas that is not burned as fuel; a methane synthesis unit 3 for converting coke and green hydrogen into methane; a preheating chamber 6 for preheating the H2 raw material at the inlet of the methane synthesis unit 3; a heat exchange unit 5 for recovering the sensible heat of the H2 and CH4 mixed gas at the outlet of the methane synthesis unit 3; and a pressure swing adsorption unit 7 for separating and purifying the H2 and CH4 mixed gas at the outlet of the methane synthesis unit 3 to obtain high-purity CH4.

[0108] In the present embodiment, the energy conversion unit 1 converts solar energy and / or wind energy into green electricity, and the green electricity drives the downstream electrolytic water hydrogen production unit 2 to produce green hydrogen H2 and by-product O2.

[0109] After the raw coal is desulfurized and denitrated and the ash is reduced by washing and selecting in the drying chamber 44, the coal enters the coal pyrolysis furnace 41 to produce coke, coke oven gas and tar.

[0110] Part of the coke oven gas and tar (gaseous) enters the combustion chamber 42 and is combusted with pure oxygen (or assisted combustion with air) with the by-product O2 from the electrolytic water hydrogen production unit 2 to provide heat for the coal pyrolysis furnace 41. The combustion flue gas is purified and decarburized in the exhaust gas purification chamber 43 and then discharged into the atmosphere.

[0111] The tar and coke oven gas that are not burned as fuel are stored in the tar storage tank 45 and the coke oven gas storage tank 46, respectively, as by-products of the present hydrogen storage system.

[0112] The coke product produced in the coal pyrolysis furnace 41 and the H2 preheated in the preheating chamber 6 enter the methane synthesis unit 3 to synthesize methane.

[0113] The H2 and CH4 mixed gas (which can be understood as the aforementioned mixed gas containing methane) at the outlet of the methane synthesis unit 3 is recovered for sensible heat in the heat exchange unit 5 and is provided to the preheating chamber 6 to preheat the H2 at the inlet of the methane synthesis unit 3.

[0114] The cooled H2 and CH4 mixed gas enters the pressure swing adsorption unit 7 for separation and purification to obtain high-purity CH4 and H2.

[0115] The high-purity CH4 is transported to users through the natural gas pipeline network, and the separated H2 is mixed with the H2 at the outlet of the electrolytic water hydrogen production unit 2, preheated in the preheating chamber 6, and then enters the methane synthesis unit 3 again to participate in the reaction.

[0116] The present application realizes safe, stable, long-distance and large-scale storage and transportation of hydrogen by using the coke generated by coal pyrolysis as a storage and transportation carrier of hydrogen. The present application utilizes abundant coal resources and solar energy, wind energy and other resources to convert them into the scarce natural gas resource, which helps to alleviate the use pressure of natural gas. The present application uses the raw materials obtained by water electrolysis and coal pyrolysis respectively, and uses the existing natural gas pipeline for directional transmission to reduce the cost.

[0117] Example 1

[0118] The hydrogen storage system shown in Figure 1 was used. In the process of coal pyrolysis, the temperature was raised from 30℃ to 400℃ at a heating rate of 20℃ / min, and drying and degassing treatment was performed during the temperature rising process; the temperature was kept at 400℃ for 10min for the first pyrolysis treatment; the temperature was raised from 400℃ to 700℃ at a heating rate of 20℃ / min for the second pyrolysis treatment. After the temperature was stabilized at 700℃, 0.36g of coke was collected, and the mesh number was greater than 35 mesh.

[0119] After hydrogen was introduced at a flow rate of 20ml / min for 15min, the tail gas was collected and detected. Figure 5 The hydrogen storage system shown in Figure 5 was used. In the process of coal pyrolysis, the temperature was raised from 30℃ to 400℃ at a heating rate of 20℃ / min, and drying and degassing treatment was performed during the temperature rising process; the temperature was kept at 400℃ for 10min for the first pyrolysis treatment; the temperature was raised from 400℃ to 700℃ at a heating rate of 20℃ / min for the second pyrolysis treatment. After the temperature was stabilized at 700℃, 0.36g of coke was collected, and the mesh number was greater than 35 mesh. Figure 5 The hydrogen storage system shown in Figure 5 was used. In the process of coal pyrolysis, the temperature was raised from 30℃ to 400℃ at a heating rate of 20℃ / min, and drying and degassing treatment was performed during the temperature rising process; the temperature was kept at 400℃ for 10min for the first pyrolysis treatment; the temperature was raised from 400℃ to 700℃ at a heating rate of 20℃ / min for the second pyrolysis treatment. After the temperature was stabilized at 700℃, 0.36g of coke was collected, and the mesh number was greater than 35 mesh.

[0120] Further, the equilibrium conversion rate of the coke hydrogenation reaction was simulated and calculated by using the Aspen plus software (chemical process simulation software). Figure 6 The hydrogen storage system shown in Figure 5 was used. In the process of coal pyrolysis, the temperature was raised from 30℃ to 400℃ at a heating rate of 20℃ / min, and drying and degassing treatment was performed during the temperature rising process; the temperature was kept at 400℃ for 10min for the first pyrolysis treatment; the temperature was raised from 400℃ to 700℃ at a heating rate of 20℃ / min for the second pyrolysis treatment. After the temperature was stabilized at 700℃, 0.36g of coke was collected, and the mesh number was greater than 35 mesh. Figure 6 The hydrogen storage system shown in Figure 5 was used. In the process of coal pyrolysis, the temperature was raised from 30℃ to 400℃ at a heating rate of 20℃ / min, and drying and degassing treatment was performed during the temperature rising process; the temperature was kept at 400℃ for 10min for the first pyrolysis treatment; the temperature was raised from 400℃ to 700℃ at a heating rate of 20℃ / min for the second pyrolysis treatment. After the temperature was stabilized at 700℃, 0.36g of coke was collected, and the mesh number was greater than 35 mesh.

[0121] The above specific embodiments further illustrate the purpose, technical solutions and advantages of the present application. It should be understood that the above specific embodiments are only for the specific embodiments of the present application and are not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A hydrogen storage system, comprising: an energy conversion unit adapted to convert solar energy and / or wind energy into electric energy; a water electrolysis hydrogen production unit adapted to produce hydrogen by water electrolysis using the electric energy output by the energy conversion unit; a methane synthesis unit in communication with the water electrolysis hydrogen production unit and adapted to react hydrogen from the water electrolysis hydrogen production unit with coke introduced therein to obtain a mixed gas containing methane, so as to transfer chemical energy of the hydrogen to the methane for storage. 2.The hydrogen storage system of claim 1, further comprising: a coal pyrolysis unit in communication with the methane synthesis unit, the coal pyrolysis unit being adapted to provide the coke for the methane synthesis unit.

3. The hydrogen storage system of claim 2, wherein, The coal pyrolysis unit comprises: a coal pyrolysis furnace adapted to pyrolyze raw coal to obtain pyrolysis products including coke, coke oven gas and tar; a combustion chamber adapted to combust the coke oven gas and tar from the pyrolysis products to release heat and transfer the released heat to the coal pyrolysis furnace. 4.The hydrogen storage system of claim 3, wherein the coal pyrolysis unit further comprises: a tail gas purification chamber located downstream of the combustion chamber and adapted to recover gas products from the combustion chamber.

5. The hydrogen storage system of any one of claims 1-4, wherein, A heat exchange unit is provided between the water electrolysis hydrogen production unit and the methane synthesis unit and adapted to exchange heat between the mixed gas in a first temperature range and hydrogen in a second temperature range from the water electrolysis hydrogen production unit, so that the hydrogen in a third temperature range after heat exchange is heated and input to the methane synthesis unit. 6.The hydrogen storage system of any one of claims 1-4, further comprising: a pressure swing adsorption unit located downstream of the methane synthesis unit and adapted to separate methane from the mixed gas containing methane. 7.A hydrogen storage system, comprising: an energy conversion unit adapted to convert solar energy and / or wind energy into electric energy; a water electrolysis hydrogen production unit adapted to produce hydrogen by water electrolysis using the electric energy output by the energy conversion unit; a coke production unit adapted to produce coke; a methane synthesis unit in communication with the water electrolysis hydrogen production unit and adapted to react hydrogen from the water electrolysis hydrogen production unit with coke from the coke production unit to obtain a mixed gas containing methane, so as to transfer chemical energy of the hydrogen to the methane for storage; wherein a transport distance between the water electrolysis hydrogen production unit and the methane synthesis unit is less than or equal to a preset distance threshold. 8.A method for hydrogen storage, comprising: converting solar energy and / or wind energy into electric energy by means of an energy conversion unit to drive a water electrolysis hydrogen production unit to produce hydrogen; reacting hydrogen from the water electrolysis hydrogen production unit with coke introduced therein in a methane synthesis unit to obtain a mixed gas containing methane, so as to transfer chemical energy of the hydrogen to the methane for storage. 9.The method of claim 8, further comprising: pyrolyzing raw coal in a coal pyrolysis unit to obtain a mixture containing coke; wherein the pyrolysis temperature is 800-1100℃ and the pressure is 0.1-4MPa.

10. The method of claim 8, wherein, The mixed reaction of the methane synthesis unit is carried out at a reaction temperature of 500-700 DEG C and a reaction pressure of 0.1-4 MPa.

11. The method of claim 9, wherein, The pyrolysis comprises drying, degassing, first pyrolysis, second pyrolysis and polycondensation in sequence.

12. The method of claim 11, wherein, The temperature of the drying is 10-200 DEG C; the temperature of the degassing is 200-350 DEG C; the temperature of the first pyrolysis is 350-550 DEG C; the temperature of the second pyrolysis is 550-800 DEG C; and the temperature of the polycondensation is >800 DEG C.

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