Solar-driven stepwise conversion method and device for natural gas

Abstract

The present disclosure relates to the field of preparation of clean fuels and chemical raw materials ,and provides a solar-driven stepwise conversion method and device for natural gas. The method comprises: step S1: concentrating solar energy into high-temperature thermal energy, using the high-temperature thermal energy to heat methane so that the methane undergoes a cracking reaction at a preset temperature under the action of a catalyst to generate a first mixed gas containing hydrogen and methane and a carbon product, wherein the carbon product is supported on the catalyst; and step S2: after the cracking reaction lasts for a preset duration, subjecting water vapor and the carbon product to a decarbonization reaction at the preset temperature to generate a second mixed gas comprising water vapor, hydrogen, and carbon dioxide.

Description

Solar-driven stepwise conversion method and apparatus for natural gas Technical Field

[0001] This disclosure relates to the field of clean fuel and chemical feedstock preparation, and in particular to a solar-driven stepwise conversion method and apparatus for natural gas. Background Technology

[0002] Renewable energy supply and clean fuel production are important ways to solve energy and environmental problems such as energy shortages and global warming. With the introduction of the goals of "carbon peaking and carbon neutrality", there has been a positive push for exploring new paths to energy conservation, emission reduction, and sustainable development.

[0003] Natural gas reforming technology, CH4 + 2H2O → 4H2 + CO2, can convert H2O into high-value H2 fuel or chemical feedstock. Due to the abundance of natural gas resources, H2 production via natural gas has become a major hydrogen production technology route.

[0004] However, due to the presence of side reactions, the above method generates solid carbon during natural gas reforming, which adsorbs onto the catalyst surface. Under high-temperature conditions, this unremoved solid carbon rapidly cokes and adheres to the active sites of the catalyst, making it difficult for it to directly contact the reactants, thus reducing catalytic performance or even deactivating it, thereby affecting reaction efficiency. Summary of the Invention

[0005] In view of this, in order to at least partially solve at least one of the aforementioned technical problems, this disclosure provides a solar-driven stepwise conversion method and apparatus for natural gas.

[0006] According to one aspect of this disclosure, a solar-driven stepwise conversion method for natural gas is provided, characterized in that the method comprises:

[0007] Step S1: Solar energy is concentrated into high-temperature thermal energy, and the high-temperature thermal energy is used to heat methane, so that the methane undergoes a cracking reaction under the action of a preset temperature and a catalyst to generate a first mixed gas containing hydrogen and methane and carbon products, wherein the carbon products are supported on the catalyst.

[0008] Step S2: After the above-mentioned cracking reaction continues for a preset time, water vapor and the above-mentioned carbon products undergo a carbon elimination reaction at the preset temperature to generate a second mixed gas containing water vapor, hydrogen and carbon dioxide.

[0009] According to embodiments of this disclosure, the preset temperature includes 650°C to 800°C.

[0010] According to embodiments of this disclosure, the above-mentioned method of concentrating solar energy into high-temperature thermal energy and using the high-temperature thermal energy for heating, causing the methane to undergo a cracking reaction under a preset temperature and the action of a catalyst, includes:

[0011] Concentrating solar collectors are used to concentrate solar energy into high-temperature heat.

[0012] After heating the reactor to a preset temperature using the aforementioned high-temperature thermal energy, the aforementioned methane is introduced into the reactor, causing the methane to undergo a cracking reaction under the action of the aforementioned catalyst in the reactor.

[0013] The aforementioned concentrating solar collector includes at least one of the following: a tower-type concentrating solar collector, a butterfly-type concentrating solar collector, and a concentrating solar simulator.

[0014] According to embodiments of this disclosure, the process of reacting water vapor with the carbon products at the preset temperature after the pyrolysis reaction has continued for a preset duration includes:

[0015] After the above-mentioned cracking reaction has continued for a preset time, the feeding of the above-mentioned methane into the above-mentioned reactor shall be stopped;

[0016] While maintaining the preset temperature in the reactor, steam is introduced into the reactor to allow the steam to react with the carbon products in a carbon removal reaction.

[0017] According to embodiments of this disclosure, the above method further includes:

[0018] The first mixed gas or the second mixed gas is cooled to obtain a cooled first mixed gas or a cooled second mixed gas.

[0019] The first mixed gas after cooling was subjected to gas separation treatment to obtain separated hydrogen and separated methane.

[0020] The cooled second mixed gas was subjected to gas separation treatment to obtain separated hydrogen and separated carbon dioxide.

[0021] According to embodiments of this disclosure, prior to the cooling treatment of the first mixed gas or the second mixed gas, the method further includes:

[0022] Waste heat recovery treatment is performed on the first mixed gas or the second mixed gas.

[0023] According to another aspect of this disclosure, a solar-driven natural gas step conversion apparatus is provided, characterized in that the apparatus comprises:

[0024] A solar thermal collector unit is used to collect solar energy to generate high-temperature thermal energy, and to use the high-temperature thermal energy to heat the reaction unit.

[0025] The reaction unit is used to cause methane to undergo a cracking reaction at a preset temperature and under the action of a catalyst to generate a first mixed gas containing hydrogen and methane and carbon products, or to cause water vapor and the carbon products to undergo a carbon elimination reaction at the preset temperature after the cracking reaction has continued for a preset time to generate a second mixed gas containing water vapor, hydrogen and carbon dioxide.

[0026] Storage unit, used to store the gas generated by the above reaction unit.

[0027] According to embodiments of this disclosure, the above-described apparatus further includes:

[0028] The waste heat recovery unit is used to recover the waste heat of the first mixed gas or the second mixed gas and to preheat the methane or the water vapor.

[0029] According to embodiments of this disclosure, the above-described apparatus further includes:

[0030] A cooling unit is used to cool the first mixed gas or the second mixed gas to obtain a cooled first mixed gas or a cooled second mixed gas.

[0031] The first gas separation unit is used to perform gas separation processing on the cooled first mixed gas to obtain separated hydrogen and separated methane.

[0032] The second gas separation unit is used to perform gas separation processing on the cooled second mixed gas to obtain separated hydrogen and separated carbon dioxide.

[0033] According to embodiments of this disclosure, the above-described apparatus further includes:

[0034] A filtration unit is provided at the outlet of the reaction unit for purifying the first mixed gas or the second mixed gas generated by the reaction unit.

[0035] According to embodiments of this disclosure, by decoupling the natural gas reforming process into a stepwise process of methane cracking reaction and decarbonization reaction, and by controlling the switching timing of the two reactions and regulating the water vapor flow rate and duration in the decarbonization reaction, it is possible to achieve complete elimination of carbon deposits and regeneration of the catalyst.

[0036] By decoupling the natural gas reforming process into a stepwise process of methane cracking and decarbonization, the reaction temperature can be reduced from 800℃~950℃ to 650℃~800℃. Simultaneously, the reaction temperature ranges of the methane catalytic cracking and decarbonization reactions are the same, and the close temperature of the two reactions allows for isothermal reactions, avoiding sensible heat loss during the switching between the two reactions.

[0037] Producing H2 through solar-driven natural gas reforming not only stores and utilizes discontinuous, unstable, and low-energy-density solar energy in the form of stable and high-density chemical energy, but also transforms H2O into high-value H2 products.

[0038] By using methane and steam as raw materials to produce hydrogen, the pressure only needs to be increased to the CH4 or CO2 adsorption pressure level during the H2 separation and purification process. High-purity H2 is produced by separating CH4 or CO2, avoiding high hydrogen adsorption pressure and reducing separation energy consumption. Attached Figure Description

[0039] The above and other objects, features and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0040] Figure 1 is a flowchart of a solar-driven stepwise natural gas conversion method according to an embodiment of the present disclosure;

[0041] Figure 2 is a schematic diagram of a solar-driven stepwise natural gas conversion method according to an embodiment of the present disclosure;

[0042] Figure 3 is a structural diagram of a solar-driven natural gas step conversion device according to an embodiment of the present disclosure;

[0043] Figure 4 is a structural diagram of a solar-driven natural gas step conversion apparatus according to another embodiment of the present disclosure. Detailed Implementation

[0044] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0045] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The term "comprising" as used herein indicates the presence of features, steps, or operations, but does not exclude the presence or addition of one or more other features.

[0046] When using expressions such as "at least one of A, B, and C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, and C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.). Similarly, when using expressions such as "at least one of A, B, or C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.).

[0047] Renewable energy supply and clean fuel production are important ways to solve energy and environmental problems such as energy shortages and global warming. With the successive proposals of the goals of "carbon peaking and carbon neutrality", researchers are actively exploring new routes for energy conservation, emission reduction and sustainable development.

[0048] Solar-powered natural gas reforming (CH4 + 2H2O → 4H2 + CO2) utilizes thermochemical reactions to store discontinuous, unstable, and low-energy-density solar energy in a stable, high-density chemical energy form. Simultaneously, it can convert H2O into high-value H2 fuel or chemical feedstock, making it a hot technology in the energy and chemical industries. Due to the abundance of natural gas resources, H2 production from natural gas has become a major hydrogen production technology route.

[0049] However, problems such as catalyst deactivation, low energy efficiency, and high energy consumption for product separation have hindered the further development and application of this technology. First, due to the presence of side reactions, solid carbon is generated during natural gas reforming and adsorbed onto the catalyst surface. Under high temperatures, this unremoved solid carbon rapidly cokes and adheres to the active sites of the catalyst, making it difficult for it to directly contact the reactants, thus reducing catalytic performance or even causing deactivation. Second, the high natural gas reforming temperature (800℃~1000℃) and the mismatch between the reaction rate and solar heat flow result in significant radiation and heat loss from the solar reactor, leading to a decrease in energy conversion efficiency. Furthermore, using separation technologies such as pressure swing adsorption at the reactor outlet to separate mixed gases such as methane (CH4, the main component of natural gas, accounting for >90%), CO2, and H2 requires substantial separation power consumption, further reducing energy conversion efficiency.

[0050] In order to at least partially solve at least one of the aforementioned technical problems, this disclosure provides a solar-driven stepwise conversion method for natural gas.

[0051] Figure 1 is a flowchart of a solar-driven stepwise conversion method for natural gas according to an embodiment of the present disclosure.

[0052] As shown in Figure 1, the natural gas step conversion method of this embodiment includes steps S1 and S2.

[0053] In step S1, solar energy is concentrated into high-temperature thermal energy, which is used to heat methane, causing the methane to undergo a cracking reaction under a preset temperature and the action of a catalyst, generating a first mixed gas containing hydrogen and methane and carbon products. The carbon products are supported on the catalyst.

[0054] In step S2, after the above-mentioned pyrolysis reaction continues for a preset time, water vapor and the above-mentioned carbon products undergo a carbon elimination reaction at the above-mentioned preset temperature to generate a second mixed gas containing water vapor, hydrogen and carbon dioxide.

[0055] According to embodiments of this disclosure, the catalyst may be particulate or porous.

[0056] According to an embodiment of this disclosure, step S2 is performed after step S1. After step S2 removes carbon deposits, step S1 can be repeated, and so on.

[0057] According to embodiments of this disclosure, by decoupling the natural gas reforming process into a stepwise process of methane cracking reaction and decarbonization reaction, and by controlling the switching timing of the two reactions and regulating the water vapor flow rate and duration in the decarbonization reaction, it is possible to achieve complete elimination of carbon deposits and regeneration of the catalyst.

[0058] According to embodiments of this disclosure, by decoupling the natural gas reforming process into a stepwise process of methane cracking and carbon removal, the reaction temperature ranges of the methane catalytic cracking and carbon removal reactions are the same, and the temperatures of the two reactions are close, which can achieve isothermal reactions and avoid sensible heat loss when switching between the two reactions.

[0059] According to embodiments of this disclosure, the methane catalytic cracking reaction is a gas-solid reaction, in which the H2 produced is automatically separated from the solid carbon, enabling the direct production of hydrogen-rich fuels.

[0060] According to embodiments of this disclosure, H2 is produced by solar-driven natural gas reforming, which not only stores and utilizes discontinuous, unstable, and low-energy-density solar energy in the form of stable and high-density chemical energy, but also converts H2O into high-value H2 products.

[0061] The natural gas stepwise conversion method provided in this disclosure can continuously transfer and clean carbon deposits on the catalyst surface during the solar thermochemical reaction process, and release catalyst active sites in a timely manner, which will effectively improve catalyst life and enhance the operational stability of solar natural gas reforming.

[0062] According to the embodiments of this disclosure, the H2 generated in steps S1 and S2 can be used as a solar energy carrier for storage and transportation, realizing the stable utilization of solar energy across time and space; it can also be used as a chemical raw material to meet the needs of downstream chemical processes.

[0063] According to embodiments of this disclosure, the preset temperature includes 650°C to 800°C.

[0064] According to embodiments of this disclosure, the preset temperature can be 650°C, 700°C, 750°C, 800°C, etc.

[0065] The related natural gas reforming technology, CH4 + 2H2O → 4H2 + CO2, typically involves reforming at temperatures between 800°C and 1000°C. This disclosure decouples the natural gas reforming process into a stepwise process of methane cracking and carbon removal, changing the reaction pathway and reducing the reaction temperature from 800°C–1000°C to 650°C–800°C. Furthermore, the target product is precipitated in stages during the material conversion process, thus decoupling the composition ratio of the mixed products. In addition, the reaction temperature ranges for the methane catalytic cracking and carbon removal reactions are the same, and the close proximity of the two reactions allows for isothermal reactions, avoiding sensible heat loss during the switching between the two reactions.

[0066] According to embodiments of this disclosure, the above-mentioned method of concentrating solar energy into high-temperature thermal energy and using the high-temperature thermal energy to heat the methane to cause a cracking reaction under the action of a preset temperature and a catalyst includes: using a concentrating solar collector to concentrate solar energy into high-temperature thermal energy; using the high-temperature thermal energy to heat the reactor to a preset temperature, and then introducing the methane into the reactor so that the methane undergoes a cracking reaction under the action of the catalyst in the reactor.

[0067] According to embodiments of this disclosure, the above-mentioned concentrating solar collector may include at least one of the following: a tower-type concentrating solar collector, a butterfly-type concentrating solar collector, and a concentrating solar simulator.

[0068] It should be noted that both steps S1 and S2 are performed under concentrated solar energy irradiation conditions.

[0069] According to an embodiment of this disclosure, the process of reacting water vapor with the carbon products at the preset temperature after the pyrolysis reaction has continued for a preset duration includes: stopping the introduction of methane into the reactor after the pyrolysis reaction has continued for a preset duration; and introducing water vapor into the reactor while maintaining the preset temperature, so that the water vapor reacts with the carbon products in a carbon removal reaction.

[0070] Figure 2 is a schematic diagram of a solar-driven stepwise conversion method for natural gas according to an embodiment of the present disclosure.

[0071] As shown in Figure 2, the natural gas stepwise conversion method according to an embodiment of this disclosure may specifically include:

[0072] In step 1, a catalyst is filled into the reactor. After heating the reactor to 650℃~800℃ using a concentrating solar collector, methane gas is introduced into the reactor. The methane comes into full contact with the catalyst and undergoes a cracking reaction to generate hydrogen gas. The reaction equation is as follows: CH4→C(s)+2H2. The carbon products remain on the catalyst surface and gradually accumulate as the reaction proceeds.

[0073] After the above-mentioned cracking reaction has continued for a preset time, the feeding of methane into the reactor is stopped.

[0074] In step 2, the reactor is heated using a concentrating solar collector to maintain the reactor at 650℃~800℃. Then, steam is introduced into the reactor, using the carbon products generated by the pyrolysis reaction as reactants. The steam reacts with the carbon products to reduce H2O to H2. The reaction equation is as follows: 2H2O+C→2H2+CO2. As the carbon reduction reaction proceeds, the solid carbon accumulated on the catalyst gradually decreases until the H2O(g) inlet stops or the solid carbon is completely eliminated, thus achieving catalyst regeneration.

[0075] After the carbon removal reaction has continued for the preset time, stop introducing steam into the reactor. Switch back to methane gas and repeat steps 1 and 2.

[0076] According to embodiments of this disclosure, the solar-powered natural gas reforming process is decoupled into a stepwise process of catalytic methane cracking and carbon removal reaction. By controlling the switching timing of the two reactions and regulating the H2O flow rate and duration of the carbon removal reaction, the complete elimination of carbon deposition and the complete regeneration of the catalyst can be achieved, effectively solving the problem of continuous accumulation of solid carbon in the traditional solar-powered natural gas reforming process, which ultimately leads to catalyst deactivation.

[0077] According to embodiments of this disclosure, the method further includes: cooling the first mixed gas or the second mixed gas to obtain a cooled first mixed gas or a cooled second mixed gas; performing gas separation treatment on the cooled first mixed gas to obtain separated hydrogen and separated methane; and performing gas separation treatment on the cooled second mixed gas to obtain separated hydrogen and separated carbon dioxide.

[0078] According to embodiments of this disclosure, the first mixed gas is cooled to obtain a cooled first mixed gas. The cooled first mixed gas can be directly collected as H2-rich fuel gas, or the cooled first mixed gas can be subjected to gas separation treatment to remove unreacted methane, output high-purity H2 and collect it.

[0079] According to embodiments of this disclosure, the second mixed gas is cooled to obtain a cooled second mixed gas. The cooled second mixed gas can be directly collected as H2-rich fuel gas, or the cooled second mixed gas can be subjected to gas separation treatment to remove the generated carbon dioxide, output high-purity H2 and collect it.

[0080] According to embodiments of this disclosure, high-purity H2 is produced using methane and H2O as raw materials through the method provided herein. The advantage over traditional solar-powered natural gas reforming lies in the fact that traditional technologies require pressurizing the cooled gaseous product mixture (H2, CO2, and CH4) to a high hydrogen adsorption pressure to achieve H2 separation and purification, resulting in high energy consumption. This disclosure decouples the CH4 reaction from the CO2 generation reaction. For H2 separation and purification after step S1, only the pressure needs to be increased to the CH4 adsorption pressure level; high-purity H2 can be produced by separating CH4, avoiding the need for a high H2 adsorption pressure. For H2 separation and purification after step S2, after cooling the outlet product to remove water vapor, only the pressure needs to be increased to the CO2 adsorption pressure level; high-purity H2 can be produced by separating CO2, reducing the high H2 separation energy consumption of traditional solar-powered natural gas wet reforming technology and improving energy efficiency.

[0081] According to embodiments of this disclosure, before cooling the first mixed gas or the second mixed gas as described above, the method further includes: performing waste heat recovery treatment on the first mixed gas or the second mixed gas.

[0082] According to another aspect of this disclosure, a solar-driven natural gas step conversion apparatus is provided, the apparatus comprising:

[0083] A solar thermal collector unit is used to collect solar energy to generate high-temperature thermal energy, and to use the high-temperature thermal energy to heat the reaction unit.

[0084] The reaction unit is used to cause methane to undergo a cracking reaction at a preset temperature and under the action of a catalyst to generate a first mixed gas containing hydrogen and methane and carbon products, or to cause water vapor and the carbon products to undergo a carbon elimination reaction at the preset temperature after the cracking reaction has continued for a preset time to generate a second mixed gas containing water vapor, hydrogen and carbon dioxide.

[0085] Storage unit, used to store the gas generated by the above reaction unit.

[0086] According to embodiments of this disclosure, the solar thermal collector unit may employ a solar thermal collector device, such as a tower concentrating solar collector, a butterfly concentrating solar collector, or a concentrating solar simulator.

[0087] According to embodiments of this disclosure, the reaction unit may include a cavity-type solar reactor for the catalytic methane cracking reaction in step S1 and the carbon removal reaction in step S2, and a catalyst bed for receiving concentrated solar heat flow during the catalytic reaction. The reactor further includes a quartz window for receiving solar energy.

[0088] According to embodiments of this disclosure, the storage unit may include a hydrogen storage tank for storing hydrogen, a carbon dioxide storage tank for storing carbon dioxide, a first hydrogen-rich storage tank for storing hydrogen-rich gas containing hydrogen and methane, and a second hydrogen-rich storage tank for storing hydrogen and carbon dioxide.

[0089] According to embodiments of this disclosure, the above-described apparatus may further include necessary gas pipelines, valves, and other connecting and control components.

[0090] According to an embodiment of this disclosure, the apparatus further includes a filter unit disposed at the outlet of the reaction unit for purifying the first mixed gas or the second mixed gas generated by the reaction unit.

[0091] According to embodiments of this disclosure, the filtration unit may employ a filter, which may be located at the outlet of the cavity-type solar reactor for purifying gaseous products.

[0092] According to embodiments of this disclosure, the above-mentioned apparatus may further include a cooling unit for cooling the first mixed gas or the second mixed gas to obtain a cooled first mixed gas or a cooled second mixed gas.

[0093] According to embodiments of this disclosure, the cooling unit may employ a cooler for cooling gaseous products.

[0094] According to embodiments of this disclosure, the apparatus further includes: a waste heat recovery unit for recovering the waste heat of the first mixed gas or the second mixed gas, and for preheating the methane or the water vapor.

[0095] According to embodiments of this disclosure, the waste heat recovery unit may employ a heat exchanger to recover the sensible heat of the gaseous products and heat them before the methane and H2O feed.

[0096] According to embodiments of this disclosure, the above-described apparatus further includes:

[0097] The first gas separation unit is used to perform gas separation processing on the cooled first mixed gas to obtain separated hydrogen and separated methane.

[0098] The second gas separation unit is used to perform gas separation processing on the cooled second mixed gas to obtain separated hydrogen and separated carbon dioxide.

[0099] The first gas separation unit is used to purify the gas exiting the solar reactor in step S1 (a mixture of CH4 and H2) to produce high-purity H2. The second gas separation unit is used to purify the gas exiting the solar reactor in step S2 (a mixture of CO2 and H2) to produce high-purity H2 and CO2.

[0100] According to embodiments of this disclosure, the steps for implementing a solar-driven natural gas step-by-step conversion method using the aforementioned solar-driven natural gas step-by-step conversion device are as follows:

[0101] Step 1: Solar energy is generated into high-temperature heat through a concentrating solar collector, and enters the reactor cavity through the quartz window to heat the catalyst bed to the required reaction temperature.

[0102] Step 2: CH4 feedstock enters the solar reactor and undergoes a cracking reaction (CH4→C) under the action of a catalyst. (s) +2H2), the generated H2 and unreacted methane leave the solar reactor through a filter;

[0103] Step 3: The hydrogen-rich mixture, after being cooled by the heat exchanger and cooler, selectively passes through the first gas separation unit and is output from the system;

[0104] Step 4: After a period of catalytic methane cracking reaction, stop feeding methane into the reactor and switch to H2O. (g) Air intake;

[0105] Step 5: Solid carbon and H2O retained on the catalyst surface during the methane cracking reaction (g) Carbon removal reaction occurs (2H2O + C) (s) →2H2+CO2), the mixture of H2, H2O and CO2 leaves the solar reactor through a filter;

[0106] Step 6: After cooling by heat exchanger and cooler, water vapor in the gas mixture is removed, and the remaining gas components (H2 and CO2) selectively pass through the second gas separation unit and are output from the system;

[0107] Step 7: As the carbon removal reaction proceeds, the solid carbon on the catalyst surface gradually decreases until it is completely consumed or H2O is stopped. (g) Intake air to complete one operation. Repeat step 1 by introducing CH4 again to achieve continuous and stable product output.

[0108] To make the objectives, technical solutions, and advantages of this disclosure clearer and more explicit, the following detailed description of this disclosure is provided with reference to the accompanying drawings and embodiments. It should be understood that the embodiments specifically described herein are for illustrative purposes only and are not intended to limit this disclosure.

[0109] Example 1

[0110] This embodiment provides a solar-powered natural gas step-by-step conversion device. Figure 3 is a structural diagram of a solar-powered natural gas step-by-step conversion device according to an embodiment of this disclosure.

[0111] As shown in Figure 3, the apparatus of this embodiment includes:

[0112] Concentrating solar thermal collector 301 is used to concentrate solar energy to form high-temperature thermal energy.

[0113] A cavity-type solar reactor 302 is used for methane cracking and carbon removal reactions. The cavity-type solar reactor 302 is equipped with a quartz window 303 and a catalyst bed 304. The quartz window 303 transmits concentrated solar thermal energy into the cavity of the solar reactor 302. The catalyst bed 304, located inside the reactor 302, receives the concentrated solar heat flow to catalyze the methane cracking reaction.

[0114] Filter 305 is installed at the outlet of solar reactor 302 to purify gaseous products.

[0115] Heat exchanger 306 is used to recover the sensible heat of gaseous products to preheat CH4 or H2O feed.

[0116] Cooler 307 is used to cool gaseous products.

[0117] Gas storage tank 308 is used to collect H2-rich fuel containing methane.

[0118] Gas storage tank 309 is used to collect H2-rich fuel containing carbon dioxide.

[0119] In this embodiment, the concentrating solar collector 301 gathers solar energy to form high-temperature radiant heat, which is injected into the cavity solar reactor 302 through the quartz window 303 to heat the catalyst bed 304 to 650°C to 800°C and continuously provide radiant heat to the solar reactor.

[0120] In CH4 cracking mode, CH4 is preheated by heat exchanger 306 and enters cavity-type solar reactor 302, where it undergoes a cracking reaction under the action of a catalyst. The resulting solid carbon products are retained in the catalyst, while the gaseous products H2 and unreacted CH4 (H2-rich fuel gas) are purified by filter 305 and then enter heat exchanger 306 to recover sensible heat. After waste heat recovery, the H2-rich fuel gas is cooled in cooler 307 and then stored as fuel in H2-rich fuel storage tank 308.

[0121] After running in the CH4 cracking mode for a period of time, the CH4 feed is stopped and replaced with H2O feed, switching to the carbon removal mode.

[0122] In the carbon removal mode, H2O is preheated in heat exchanger 306 to form water vapor, which then enters the cavity-type solar reactor 302 and reacts with solid carbon generated on the catalyst surface from CH4 cracking. The resulting CO2 and H2 products (H2-rich fuel gas) are purified by filter 305 and then enter heat exchanger 306 to recover sensible heat. After waste heat recovery, the H2-rich fuel gas is cooled in cooler 307 and stored as fuel in storage tank 309.

[0123] In decarbonization mode, the solid carbon on the catalyst surface gradually decreases as the reaction proceeds until it is completely consumed or the H2O feed stops, thus completing one operation. CH4 is then introduced again to repeat the CH4 cracking mode, achieving continuous and stable solar-rich H2 fuel production.

[0124] Example 2

[0125] This embodiment provides another solar-driven natural gas step-by-step conversion device. Figure 4 is a structural diagram of a solar-driven natural gas step-by-step conversion device according to another embodiment of this disclosure.

[0126] As shown in Figure 4, the apparatus of this embodiment includes:

[0127] Concentrating solar thermal collector 401 is used to concentrate solar energy to form high-temperature thermal energy.

[0128] A cavity-type solar reactor 402 is used for methane cracking and carbon removal reactions. The cavity-type solar reactor 402 is equipped with a quartz window 403 and a catalyst bed 404. The quartz window 403 allows concentrated solar thermal energy to pass through and enter the cavity of the solar reactor 402. The catalyst bed 404, located inside the reactor 402, receives the concentrated solar heat flow to catalyze the methane cracking reaction.

[0129] Filter 405 is installed at the outlet of solar reactor 402 to purify gaseous products.

[0130] Heat exchanger 406 is used to recover the sensible heat of gaseous products to preheat CH4 or H2O feed.

[0131] Cooler 407 is used to cool gaseous products.

[0132] Separation unit 408 is used to separate H2 and CH4 during the catalytic methane cracking stage.

[0133] Gas storage tank 409 is used to collect high-purity H2 fuel.

[0134] Separation device 410 is used to separate H2 and CO2 during the carbon removal reaction stage.

[0135] Gas storage tank 411, for carbon dioxide.

[0136] In this embodiment, the concentrating solar collector 401 gathers solar energy to form high-temperature radiant heat, which is injected into the cavity solar reactor 402 through the quartz window 403 to heat the catalyst bed 404 to 650°C to 800°C and continuously provide radiant heat to the solar reactor.

[0137] In CH4 cracking mode, CH4 is preheated by heat exchanger 406 and enters cavity solar reactor 402, where it undergoes a cracking reaction under the action of a catalyst. The resulting solid carbon products are retained in the catalyst, while the gaseous product H2 and unreacted CH4 are purified together by filter 405 and then enter heat exchanger 406 to recover sensible heat. The mixed gas after waste heat recovery is cooled in cooler 407 and enters gas separation device 408. The separated high-purity hydrogen is stored as a product in gas storage tank 409, while the separated CH4 is recycled back into the system.

[0138] After running in the CH4 cracking mode for a period of time, the CH4 feed is stopped and replaced with H2O steam feed, switching to the carbon removal mode.

[0139] In decarbonization mode, H2O is preheated in heat exchanger 406 to form water vapor, which then enters the cavity-type solar reactor 402 to react with solid carbon generated on the catalyst surface in CH4 decomposition mode. The resulting H2 and CO2 products, along with unreacted H2O vapor, are purified by filter 405 and then enter heat exchanger 406 to recover sensible heat. The mixed gas after waste heat recovery is cooled in cooler 407 to remove H2O vapor before entering gas separation device 410. The separated high-purity H2 and CO2 are stored in storage tanks 409 and 411, respectively.

[0140] In decarbonization mode, the solid carbon on the catalyst surface gradually decreases as the reaction proceeds until it is completely consumed or the H2O intake stops, thus completing one operation. CH4 is then introduced again to repeat the CH4 cracking mode, achieving continuous and stable solar-rich H2 fuel production.

[0141] The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of this disclosure. It should be understood that the above descriptions are merely specific embodiments of this disclosure and are not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A solar-driven natural gas staged reforming process, characterized in that, The method comprises: Step S1: concentrating solar energy into high-temperature heat energy, heating methane by using the high-temperature heat energy, and making the methane undergo a cracking reaction under the action of a catalyst at a preset temperature to generate a first mixed gas containing hydrogen and methane and a carbon product, wherein the carbon product is loaded on the catalyst; Step S2: after the cracking reaction lasts for a preset time length, making water vapor undergo a carbon removal reaction with the carbon product at the preset temperature to generate a second mixed gas containing water vapor, hydrogen, and carbon dioxide.

2. The method of claim 1, wherein, The preset temperature comprises 650-800°C.

3. The method of claim 1, wherein, The step of concentrating solar energy into high-temperature heat energy and heating by using the high-temperature heat energy to make the methane undergo a cracking reaction under the action of a catalyst at a preset temperature comprises: Concentrating solar energy into high-temperature heat energy by using a concentrating heat collecting device; After heating a reactor to a preset temperature by using the high-temperature heat energy, introducing the methane into the reactor, and making the methane undergo a cracking reaction under the action of the catalyst in the reactor; The concentrating heat collecting device comprises at least one of a tower type concentrating solar heat collector, a butterfly type concentrating solar heat collector, and a concentrating solar simulator.

4. The method of claim 3, wherein, The step of, after the cracking reaction lasts for a preset time length, making water vapor undergo a carbon removal reaction with the carbon product at the preset temperature comprises: After the cracking reaction lasts for a preset time length, stopping the introduction of the methane into the reactor; In the case that the temperature of the reactor remains at the preset temperature, introducing the water vapor into the reactor, and making the water vapor undergo a carbon removal reaction with the carbon product.

5. The method of claim 1, wherein, The method further comprises: Cooling the first mixed gas or the second mixed gas to obtain cooled first mixed gas or cooled second mixed gas; Separating the cooled first mixed gas to obtain separated hydrogen and separated methane; Separating the cooled second mixed gas to obtain separated hydrogen and separated carbon dioxide.

6. The method according to claim 5, wherein, before the step of cooling the first mixed gas or the second mixed gas, the method further comprises: Recovering waste heat of the first mixed gas or the second mixed gas. The device comprises:

7. A solar-driven natural gas staged-reforming apparatus, characterized in that, A solar heat collecting unit configured to concentrate solar energy into high-temperature heat energy and heat a reaction unit by using the high-temperature heat energy; A reaction unit configured to make methane undergo a cracking reaction under the action of a catalyst at a preset temperature to generate a first mixed gas containing hydrogen and methane and a carbon product, or configured to, after the cracking reaction lasts for a preset time length, make water vapor undergo a carbon removal reaction with the carbon product at the preset temperature to generate a second mixed gas containing water vapor, hydrogen, and carbon dioxide; A storage unit configured to store the gas generated by the reaction unit. The device further comprises:

8. The apparatus of claim 7, wherein, A waste heat recovering unit configured to recover waste heat of the first mixed gas or the second mixed gas and configured to preheat the methane or the water vapor. The device further comprises:

9. The apparatus of claim 7, wherein, ​ a cooling unit configured to cool the first mixed gas or the second mixed gas to obtain cooled first mixed gas or cooled second mixed gas; a first gas separation unit configured to separate the cooled first mixed gas to obtain separated hydrogen and separated methane; a second gas separation unit configured to separate the cooled second mixed gas to obtain separated hydrogen and separated carbon dioxide.

10. The apparatus of claim 7, wherein, The device further comprises: a filtering unit arranged at an outlet of the reaction unit and configured to purify the first mixed gas or the second mixed gas generated by the reaction unit.

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