1. A methanation system for solar thermochemical cycle hydrogen production, characterized in that the system comprises:

thermochemical cycle hydrogen production module: water and cerium oxide are used as raw materials to realize thermochemical cycle hydrogen production, and high-temperature hydrogen and high-temperature oxygen are generated;

the high-temperature gas waste heat recovery module comprises: receiving high-temperature hydrogen and high-temperature oxygen generated by the thermochemical cycle hydrogen production module to generate electricity;

a biological methane module: industrial waste gas and low-temperature hydrogen subjected to waste heat recovery are used as input, and a high-temperature gas waste heat recovery module is used for generating electricity to provide a voltage environment to generate methane gas.

2. The methanation system for solar thermochemical cycle hydrogen production according to claim 1, wherein the thermochemical cycle hydrogen production module comprises:

reduction reactor (1): the method is used for carrying out a high-temperature reduction reaction process of cerium oxide to generate low-valence cerium oxide and high-temperature oxygen;

oxidation reactor (2): the method is used for carrying out a low-temperature reduction reaction process of low-valence cerium oxide to generate cerium oxide and high-temperature hydrogen;

solar heat collector (3): used for absorbing solar energy to provide a high-temperature environment for the reduction reactor (1);

water tank (6): for providing a water source for the oxidation reactor (2);

a heat circulation loop: the device comprises a first heat storage bottle (4) connected with a reduction reactor (1), a second heat storage bottle (5) connected with an oxidation reactor (2), a connecting pipeline, a valve, a circulating pump and a circulating loop medium.

3. The methanation system for solar thermochemical cycle hydrogen production according to claim 2, wherein the medium of the circulation loop is argon.

4. The methanation system for solar thermochemical cycle hydrogen production according to claim 2, characterized in that the thermochemical cycle hydrogen production module further comprises a high temperature oxygen heat exchanger (10), a high temperature hydrogen heat exchanger (15), and an oxygen cylinder (12) connected to the high temperature oxygen heat exchanger (10) through a valve and a circulation pump.

5. The methanation system for solar thermochemical cycle hydrogen production according to claim 4, characterized in that the high-temperature gas waste heat recovery module is composed of a heat engine (13) and a generator (14) which are connected with each other, the heat engine (13) respectively receives high-temperature water vapor mediums of the high-temperature oxygen heat exchanger (10) and the high-temperature hydrogen heat exchanger (15) and then pushes a rotor of the generator (14) to rotate to complete a power generation process, one part of electric energy generated by the generator (14) is incorporated into a power grid, and the other part of electric energy provides a voltage environment for the biomethane module.

6. The methanation system for solar thermochemical cycle hydrogen production according to claim 5, characterized in that the biomethane module comprises a biomethane tank (17), a carbon dioxide capture device (18) and a gas purification tower (19), wherein the carbon dioxide capture device (18) is used for capturing high-concentration carbon dioxide in industrial waste gas and inputting the carbon dioxide into the biomethane tank (17), low-temperature hydrogen generated by the high-temperature hydrogen heat exchanger (15) is input into the biomethane tank (17) through a valve and a circulating pump, and after activated sludge in the biomethane tank (17) reacts in a growth environment provided by electric energy of a generator (14) to generate methane gas doped with a small amount of hydrogen and carbon dioxide, the methane gas is purified by the gas purification tower (19) and then introduced into a gas pipeline for use.

7. Methanation process using a methanation system for solar thermochemical cycle hydrogen production according to any of claims 1 to 6, characterized in that it comprises the following steps:

1) cerium oxide oxygen carrier at high temperature T_HWhen the cerium oxide is reduced in the reduction reactor (1), oxygen is released to generate low-valence cerium oxide CeO_2-δ-αThen enters an oxidation reactor (2) at a low temperature T_LLower and H₂O is oxidized and releases hydrogen to generate cerium oxide CeO_2-δReturning to the reduction reactor (1) for circulating reaction;

in the oxidation-reduction circulation reaction process, sunlight concentrates heat through a solar heat collector (3) to provide a high-temperature environment for a reduction reactor (1), and a water tank (6) provides water for the oxidation reactor through a circulating pump;

2) after the reduction reaction is finished, the unused heat enters the oxidation reactor (2) in a first circulation direction to provide a low-temperature environment for the oxidation reaction process;

3) after the oxidation reaction is finished, the unused heat enters the reduction reactor (1) along a second circulation direction, and a high-temperature environment is provided for the reduction reaction process by combining the heat of the solar heat collector (3);

4) after the high-temperature oxygen generated by the reduction reaction in the reduction reactor (1) and the high-temperature hydrogen generated by the oxidation reaction in the oxidation reactor (2) respectively pass through the high-temperature oxygen heat exchanger (10) and the high-temperature hydrogen heat exchanger (15) to generate water vapor to push the rotating wheel of the heat engine (13) to rotate so as to drive the rotor of the generator (14) to rotate for generating electricity, the low-temperature oxygen is input into the oxygen cylinder (12) through a valve and a circulating pump to be stored, and the low-temperature hydrogen is conveyed into the biological methane tank (17);

5) the biological methane tank (17) takes low-temperature hydrogen and carbon dioxide captured by the carbon dioxide capture device (18) as input, a generator (14) provides a voltage environment, the hydrogen and the carbon dioxide react to generate methane gas under the action of the domesticated activated sludge microorganisms, and the generated methane gas is introduced into a gas purification tower (19) to be purified and then is introduced into a gas pipeline through a circulating pump to be supplied to users for use.

8. Methanation method according to claim 7, characterized in that in step 2), the first circulation direction is in particular:

opening a valve between the reduction reactor (1) and the first heat storage bottle (4) to enable the medium with the residual heat of the reduction reaction to enter the first heat storage bottle (4), then opening the valve between the first heat storage bottle (4) and the second heat storage bottle (5) to enable the heat of the first heat storage bottle (4) to enter the second heat storage bottle (5), and finally opening the valve between the second heat storage bottle (5) and the oxidation reactor (2) to enable the heat to enter the oxidation reactor (2).

9. Methanation method according to claim 7, characterized in that in step 3), the second circulation direction is in particular:

and opening a valve between the oxidation reactor (2) and the second heat storage bottle (5) to enable the medium with the residual heat of the oxidation reaction to enter the second heat storage bottle (5), then opening a valve between the first heat storage bottle (4) and the second heat storage bottle (5) to enable the heat of the second heat storage bottle (5) to enter the first heat storage bottle (4), and finally opening a valve between the first heat storage bottle (4) and the reduction reactor (1) to enable the heat to enter the reduction reactor (1).

10. Methanation process according to claim 7, characterized in that in step 5) the chemical process for the generation of methane in the biological methane tank (17) is represented by:

Background

To cope with climate change, China will provide targets for carbon peak reaching 2030 and carbon neutralization 2060 in 75 th United nations in 9 months in 2020. As the biggest developing countries and carbon-emitting countries in the world, the method is in the stage of rapid development of industrialization and urbanization, the economic growth is fast, the energy demand is large, the energy system mainly using coal and the high-carbon industrial structure enable the total carbon emission amount and the intensity of China to be 'double high', the carbon peak reaching is realized in less than 10 years, the carbon neutralization is realized in about 30 years, and the task is very difficult. The development and use of a large amount of fossil energy are the root of the problem of carbon emission, the promotion of clean substitution and electric energy substitution is accelerated, and the complete escape of the dependence of fossil energy is a fundamental way to realize carbon peak reaching and carbon neutralization in China, so that a system and a method for utilizing and developing clean energy are urgently needed to be established.

In the research of sustainable clean hydrogen energy preparation technology, the solar energy is utilized to decompose H₂The method for producing hydrogen by O mainly comprises three main methods of electrolysis, photolysis and pyrolysis, electrolysis and pyrolysis can be utilized in the prior art, the photovoltaic water electrolysis hydrogen production technology is relatively wide in application but relatively high in cost, compared with the photovoltaic water electrolysis hydrogen production technology, the cost reduction of the solar thermochemical cycle hydrogen production mainly drives the cost of a reactor to be reduced day by day, and the cost reduction speed is higher under the drive of a policy, so that people have higher and higher attention to the solar thermochemical cycle hydrogen production.

The system for producing hydrogen by decomposing water through thermochemical cycle comprises a metal oxide system thermochemical cycle, a sulfur-containing system, a sulfuric acid decomposition method, a metal-halide system and the like, wherein the method for producing hydrogen by decomposing water through two steps of thermochemical cycle of the metal oxide system has simple steps, avoids the problem of gas separation and has high process efficiency, and most of metal oxides adopt ZnO. But has problems that: after the ZnO is reduced, if the generated oxygen is not separated in time, the oxygen is oxidized again to generate ZnO, and in addition, the generated ZnO covers the surface of Zn in the reduction reaction, so the reaction rate is influenced, and the generation of hydrogen is hindered. The main irreversible losses are secondary radiation losses and quench losses.

In response to the disadvantages of this system, Kanekoet prepares cerium oxide (CeO) by a combustion process₂)－MO_XA fluorite-structured solid solution composite oxide. At 1573-1773K, reduction reaction is carried out, then thermochemical decomposition water hydrogen production process is carried out at 1173K, cerium oxide oxygen carrier is firstly at high temperature T_HWhen the process is carried out, reduction reaction is carried out to release oxygen, lower oxygen partial pressure can be obtained by adopting modes of inert gas blowing or vacuum pump and the like,

then at a temperature T_LWhen the reduced cerium oxide is mixed with H₂O undergoes an oxidation reaction, in the course of which H is released₂Then, there are:

the composite oxide has better hydrogen production performance, avoids using a quenching device, and has lower decomposition temperature. Compared with zinc oxide, cerium dioxide has better absorption capacity for solar radiation, but one main aspect of the solar fuel conversion efficiency which cannot be improved is that heat recovery is not carried out, the oxidation temperature and the reduction temperature are both between 1100k and 1700k, a large amount of heat is carried by gas generated after reaction, and a large number of projects are applied to directly passing high-temperature gas through a condenser to achieve the purpose of cooling, so that a large amount of energy is wasted.

In the currently relevant patent research, chinese patent CN201680033307.9 "treatment system for heat regeneration and method for its operation" solves the problem that treatment units should be operated at different temperatures and the heat obtained in case of cooling is regenerated, which can achieve reduced heat loss and thus improved efficiency, but this solution fails to separate the generated gas and does not embody intermittent heating of thermochemical cycle hydrogen production.

Chinese patent CN202011134841.3 "a method and system for hydrogen production and electricity production by two-step thermochemical cycle decomposition of water" proposes a method for hydrogen production by two-step solar thermochemical cycle using zinc oxide as a carrier, and the obtained hydrogen is recycled and sent to a fuel cell for electricity generation, thereby realizing the recycling of oxygen and hydrogen and the conversion of solar energy to electric energy. According to the scheme, zinc oxide is used as a carrier, and oxygen generated after the zinc oxide is reduced is oxidized again to generate the zinc oxide if the oxygen is not separated in time. There are some irreversible losses such as secondary radiation losses and quench losses.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a methanation system and a methanation method for solar thermochemical cycle hydrogen production.

The purpose of the invention can be realized by the following technical scheme:

a methanation system for solar thermochemical cycle hydrogen production, the system comprising:

thermochemical cycle hydrogen production module: water and cerium oxide are used as raw materials to realize thermochemical cycle hydrogen production, and high-temperature hydrogen and high-temperature oxygen are generated;

the high-temperature gas waste heat recovery module comprises: receiving high-temperature hydrogen and high-temperature oxygen generated by the thermochemical cycle hydrogen production module to generate electricity;

a biological methane module: industrial waste gas and low-temperature hydrogen subjected to waste heat recovery are used as input, and a high-temperature gas waste heat recovery module is used for generating electricity to provide a voltage environment to generate methane gas.

The thermochemical cycle hydrogen production module comprises:

a reduction reactor: the method is used for carrying out a high-temperature reduction reaction process of cerium oxide to generate low-valence cerium oxide and high-temperature oxygen;

an oxidation reactor: the method is used for carrying out a low-temperature reduction reaction process of low-valence cerium oxide to generate cerium oxide and high-temperature hydrogen;

sunlight heat collector: the device is used for absorbing solar energy to provide a high-temperature environment for the reduction reactor;

a water tank: to provide a source of water for the oxidation reactor;

a heat circulation loop: the device comprises a first heat storage bottle connected with a reduction reactor, a second heat storage bottle connected with an oxidation reactor, a connecting pipeline, a valve, a circulating pump and a circulating loop medium.

The medium of the circulating loop is argon.

The thermochemical cycle hydrogen production module further comprises a high-temperature oxygen heat exchanger, a high-temperature hydrogen heat exchanger and an oxygen bottle connected with the high-temperature oxygen heat exchanger through a valve and a circulating pump.

The high-temperature gas waste heat recovery module is composed of a heat engine and a generator which are connected with each other, the heat engine respectively receives high-temperature water vapor media of the high-temperature oxygen heat exchanger and the high-temperature hydrogen heat exchanger and then pushes a generator rotor to rotate to complete the power generation process, one part of electric energy generated by the generator is merged into a power grid, and the other part of the electric energy provides a voltage environment for the biomethane module.

The biological methane module comprises a biological methane tank, a carbon dioxide capture device and a gas purification tower, wherein the carbon dioxide capture device is used for capturing high-concentration carbon dioxide in industrial waste gas and inputting the carbon dioxide into the biological methane tank, low-temperature hydrogen generated by the high-temperature hydrogen heat exchanger is input into the biological methane tank through a valve and a circulating pump, and activated sludge in the biological methane tank reacts in a growth environment provided by electric energy of a generator to generate methane gas doped with a small amount of hydrogen and carbon dioxide, and then the methane gas is purified by the gas purification tower and then introduced into a gas pipeline for users to use.

A methanation method for solar thermochemical cycle hydrogen production comprises the following steps:

1) cerium oxide oxygen carrier at high temperature T_HWhile a reduction reaction takes place in the reduction reactor and oxygen is releasedTo form low-valence cerium oxide CeO_2-δ-αThen enters an oxidation reactor at a low temperature T_LLower and H₂O is oxidized and releases hydrogen to generate cerium oxide CeO_2-δReturning to the reduction reactor for circulating reaction;

in the oxidation-reduction circulation reaction process, sunlight passes through a solar heat collector to concentrate heat to provide a high-temperature environment for a reduction reactor, and a water tank passes through a circulating pump to provide water for the oxidation reactor;

2) after the reduction reaction is finished, the unused heat enters the oxidation reactor in a first circulation direction to provide a low-temperature environment for the oxidation reaction process;

3) after the oxidation reaction is finished, the unused heat enters the reduction reactor according to a second circulation direction, and a high-temperature environment is provided for the reduction reaction process by combining the heat of the solar heat collector;

4) after the high-temperature oxygen generated by the reduction reactor through the reduction reaction and the high-temperature hydrogen generated by the oxidation reactor through the oxidation reaction respectively pass through the high-temperature oxygen heat exchanger and the high-temperature hydrogen heat exchanger to generate steam to push the heat engine runner to rotate so as to drive the generator rotor to rotate for power generation, the low-temperature oxygen is input into the oxygen bottle through the valve and the circulating pump to be stored, and the low-temperature hydrogen is conveyed into the biomethane tank;

5) the biological methane tank takes low-temperature hydrogen and carbon dioxide captured by the carbon dioxide capture device as input, a generator provides a voltage environment, hydrogen and carbon dioxide react to generate methane gas under the action of domesticated activated sludge microorganisms, and the generated methane gas is introduced into a gas purification tower, purified and then introduced into a gas pipeline through a circulating pump for use by users.

In the step 2), the first circulation direction is specifically as follows:

opening a valve between the reduction reactor and the first heat storage bottle to enable the medium with the residual heat of the reduction reaction to enter the first heat storage bottle, then opening the valve between the first heat storage bottle and the second heat storage bottle to enable the heat of the first heat storage bottle to enter the second heat storage bottle, and finally opening the valve between the second heat storage bottle and the oxidation reactor to enable the heat to enter the oxidation reactor.

In the step 3), the second circulation direction specifically is as follows:

and opening a valve between the oxidation reactor and the second heat storage bottle to enable the medium with the residual heat of the oxidation reaction to enter the second heat storage bottle, then opening the valve between the first heat storage bottle and the second heat storage bottle to enable the heat of the second heat storage bottle to enter the first heat storage bottle, and finally opening the valve between the first heat storage bottle and the reduction reactor to enable the heat to enter the reduction reactor.

In the step 5), the chemical process of generating methane by the biological methane pool is represented as:

compared with the prior art, the invention has the following advantages:

firstly, the invention adopts cerium dioxide carrier with better solar radiation adsorption capacity, solar energy provides heat source, two-step solar thermochemical cycle generates oxygen and low-valence cerium dioxide in the reduction reaction process, and generates hydrogen and cerium dioxide in the oxidation reaction process, the cycle process can directly obtain high-purity hydrogen and oxygen, the occurrence of the common hydrogen and oxygen mixed gas at present is avoided, the process of gas separation is not needed, and the economical efficiency can be improved.

The invention adopts a treatment system for regenerating the heat of the reactors at different temperatures, stores the residual heat through the first heat storage bottle and the second heat storage bottle, realizes the intermittent heating of the reactors through the linkage between the valves, and repeatedly returns according to the two heat flow directions of the first circulation direction and the second circulation direction, thereby reducing the energy consumption and greatly improving the circulation heat efficiency of the thermochemical circulation hydrogen production system.

Thirdly, the solar thermochemical cycle hydrogen production is coupled with the biological methanation system, hydrogen generated by the solar thermochemical cycle is introduced into the biological methanation system, and the high-quality methane gas is generated in the biological methane tank by the hydrogen and carbon dioxide with the assistance of waste heat recovery power generation by combining a carbon dioxide capture device;

the methanation system for solar thermochemical cycle hydrogen production is simple in process, mature in technology, easy to produce, convenient to operate and good in economic benefit, and has certain competitive potential with traditional solar hydrogen production or conversion from solar energy to chemical energy.

Drawings

FIG. 1 is a schematic diagram of a methanation system for solar thermochemical cycle hydrogen production.

FIG. 2 is a schematic diagram of a methanation process for solar thermochemical cycle hydrogen production.

The notation in the figure is:

1. a reduction reactor, 2, an oxidation reactor, 3, a solar heat collector, 4, a first heat storage bottle, 5, a second heat storage bottle, 6, a water tank, 7, a circulating pump, 8, a circulating pump, 9, a circulating pump, 10, a high-temperature oxygen heat exchanger, 11, a circulating pump, 12, an oxygen bottle, 13, a heat engine, 14, a generator, 15, a high-temperature hydrogen heat exchanger, 16, a circulating pump, 17, a biological methane tank, 18, a carbon dioxide catching device, 19, a gas purification tower, 20 and a circulating pump,and (4) a valve.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.

The invention provides a methanation system and a methanation method for solar thermochemical cycle hydrogen production, which not only provide a solar thermochemical cycle hydrogen production method with reusable heat, but also provide a comprehensive methanation system for solar thermochemical cycle hydrogen production, high-temperature gas waste heat recovery and biological methanation.

The solar thermochemical cycle hydrogen production method capable of recycling heat provided by the invention comprises the following specific steps:

(1) the cerium oxide oxygen carrier is firstly treated at high temperature T_H(1573) carrying out reduction reaction in a reduction reactor, and releasing oxygen in the process to generate low-valence cerium oxide CeO_2-δ-αThen enters an oxidation reactor and then is at a temperature T_L(1173K) Then, the reduced cerium suboxide is mixed with H₂O undergoes an oxidation reaction, in the course of which H is released₂Formed cerium oxide CeO_2-δEntering a reduction reactor;

(2) sunlight is concentrated by the solar heat collector to provide heat energy for the reduction reactor, and the water tank provides water for the oxidation reactor by the circulating pump;

(3) as shown in figure 2, the unused heat after the reduction reaction enters the oxidation reactor according to the first circulation direction to provide T for the reaction process_LAnd (3) temperature. The first cycle direction comprises the following specific steps: opening the valves, closing the rest valves, and allowing the residual heat of the reduction reaction to enter a first heat storage bottle; closing the valve, opening the valve, and allowing the heat of the first heat storage bottle to enter the second heat storage bottle; the valve is closed, (c) the valve is opened, and the heat of the second heat storage bottle enters the oxidation reactor.

(4) The unused heat after the oxidation reaction enters the reduction reactor according to a second circulation direction to provide T for the reaction process_HAnd (3) temperature. The second circulation direction comprises the following specific steps: opening the valve and closing the rest valves, and allowing the residual heat of the oxidation reaction to enter a second heat storage bottle; closing the valve and opening the valve, so that the heat in the second heat storage bottle enters the second heat storage bottle; and closing the valve, opening the valve and introducing the heat of the first heat storage bottle into the reduction reactor. It is stated that the heat in the second circulation direction is not sufficient to provide the T required for the reduction reaction_HThe residual heat is supplemented by the solar energy after passing through the heat collector, and the two circulation directions are carried out repeatedly, so that the heat can be regenerated, and the circulation heat efficiency is greatly improved.

(5) The heat transfer medium is usually argon gas in the heat regeneration process, and the physical and chemical properties are very stable, so that the method is suitable for heat transfer under the condition of higher temperature.

The methanation system for solar thermochemical cycle hydrogen production provided by the invention comprises: the system comprises a thermochemical cycle hydrogen production module, a high-temperature gas waste heat recovery module and a biological methane module, wherein the modules are specifically introduced as follows:

thermochemical circulation hydrogen manufacturing module links to each other with high-temperature gas waste heat recovery module, biological methane module, and thermochemical circulation hydrogen manufacturing module generates high-temperature hydrogen, oxygen, and high-temperature hydrogen, oxygen not only can reach the cooling effect through the waste heat recovery module, and through waste heat power generation moreover, low temperature oxygen gets into the oxygen cylinder through the circulating pump and preserves, and low temperature hydrogen gets into biological methane module afterwards through the circulating pump.

The thermochemical cycle hydrogen production module comprises a solar heat collector, a reduction reactor, an oxidation reactor, a water tank and a heat storage bottle and is used for generating hydrogen and oxygen. The solar heat collector concentrates solar heat and provides heat for the reduction reactor to generate oxygen and low-valence cerium oxide. The heat which is not utilized in the reduction process provides heat energy for the oxidation reactor through the heat storage bottle, the valve and the circulating pump, the low-valence cerium oxide and the water generate cerium oxide and hydrogen in the oxidation reactor, the residual heat which is not utilized returns to the reduction reactor again through the heat storage bottle, the valve and the circulating pump, and the insufficient heat is supplemented by solar energy.

The high-temperature gas waste heat recovery module comprises a heat exchanger, a heat engine (steam engine) and a generator and is used for recovering heat energy in high-temperature gas generated by thermochemical circulation. The heat energy is recovered through the heat exchanger, medium water in the heat exchanger is changed into steam through heat exchange, the steam drives the heat engine rotating wheel to rotate, then the heat engine rotating wheel drives the rotor of the generator to rotate for power generation, and therefore the recovered heat energy is converted into electric energy. One part of the electric energy is used for providing the environment required by the biological methane pool reaction, and the other part of the electric energy is connected into a power grid for storage.

The biological methane module comprises a biological methane tank, a carbon dioxide capture device and a gas purification tower and is used for generating high-quality methane gas, and the principle is as follows:

high-temperature hydrogen is recycled into low-temperature hydrogen through waste heat, and enters one end of the biological methane tank through the circulating pump, and meanwhile, industrial CO generated by a factory₂After passing through a carbon dioxide capture device, CO with higher purity₂And entering the other end of the biological methane tank. Under the effect of the domesticated sludge microorganisms, the waste heat recovery module provides a required voltage environment, hydrogen and carbon dioxide react to generate methane gas, and a small amount of hydrogen and carbon dioxide are doped due to reversible reaction, the gas generated in the methane tank is introduced into a gas purification tower to purify methane gas with higher concentration, and the methane gas is directly introduced into a gas pipeline after passing through a circulating pump.

According to the invention, through the methane system for solar thermochemical cycle hydrogen production with renewable heat, the methane gas at the right end of the system is finally derived from unstable and discontinuous solar energy, the hydrogen is produced by replacing photovoltaic power generation, the investment cost is reduced, the carbon emission is reduced, the problem that the hydrogen is difficult to store and transport is solved, and the high-quality methane gas is produced for the biological methane tank. Solar thermochemical cycle hydrogen production is at the left end, high-temperature gas waste heat utilization is assisted, and biomethane is at the right end, so that the solar hydrogen production methanation system is high in heat efficiency, good in economic benefit, energy-saving and environment-friendly.

Compared with the traditional method and system, the method and system provided by the invention have the advantage that the heat efficiency is improved by 25-30%. Meanwhile, on the premise of realizing the aim of 'double carbon' in China, the win-win situation of generating the methane gas by the hydrogen and the carbon dioxide is achieved, a path is provided for realizing 'carbon neutralization' in 2060 years, the whole methanation system for the solar thermochemical cycle hydrogen production has the advantages of simple process operation, energy conservation, consumption reduction, lower investment cost and operation cost, mature application technical field of the methane gas friendly to the environment and great development potential.

Examples

In order to make the objects, technical solutions and advantages of the present invention more apparent, the following detailed working conditions of the present invention are further described with reference to the accompanying drawings.

As shown in fig. 1, the methanation system for solar thermochemical cycle hydrogen production provided by the invention comprises a thermochemical cycle hydrogen production module, a high-temperature gas waste heat recovery module and a biomethane module.

The thermochemical cycle hydrogen production module comprises: a reduction reactor 1; an oxidation reactor 2; a sunlight heat collector 3; a first heat storage bottle 4; a second heat storage bottle 5; a water tank 6; the valve (III) is (III), (IV) is (III); circulating pumps 7, 8, 9 and 11, a high-temperature oxygen heat exchanger 10 and a high-temperature hydrogen heat exchanger 15.

Adding the cerium oxide into a reduction reactor, and absorbing solar energy by the reduction reactor to provide a high-temperature environment so as to decompose the cerium oxide into low-valence cerium oxide and oxygen. The temperature of oxygen is reduced after heat exchange with medium water through a heat exchanger, the oxygen enters an oxygen gas storage cylinder under the action of a circulating pump, low-valence cerium oxide enters an oxidation reactor through a pipeline, and the low-valence cerium oxide and water vapor are oxidized at a low temperature to generate cerium oxide and hydrogen. And the cerium oxide returns to the oxygen carrier in the reduction reactor through a pipeline for the next reduction reaction, and the hydrogen enters the biological methane tank after exchanging heat with the medium water through the heat exchanger.

The unused heat after the reduction reaction enters the oxidation reactor according to a first circulation direction to provide T for the reaction process_LAnd (3) temperature. The unused heat after the oxidation reaction enters the reduction reactor according to a second circulation direction to provide T for the reaction process_HAnd (3) temperature. Insufficient heat is supplemented by sunlight after heat accumulation, the heat is regenerated through the heat treatment, the circulating heat efficiency is greatly improved, and meanwhile, the gap heating in the oxidation-reduction reaction process is reflected through the linkage of the switch of the valve.

The high-temperature gas waste heat recovery module comprises: a heat engine 13 and an electric generator 14;

after the high-temperature oxygen and hydrogen exchange heat with medium water through the heat exchanger, liquid water is changed into steam to push the heat engine runner to rotate, the rotating mechanical energy pushes the rotor of the generator to rotate to complete the power generation process, one part of the electric energy of the generator is used for providing a growing environment of activated sludge in the biochemical methane tank, and the other part of the electric energy is introduced into a power grid to be stored.

The biomethane module comprises: valve gateCirculation pumps 16, 20; a biological methane tank 17; a carbon dioxide capturing device 18 and a gas purification tower 19;

as shown in fig. 1, the high-temperature hydrogen is changed into low-temperature hydrogen after heat exchange and temperature reduction through the heat exchanger, and the hydrogen enters the inlet side of the methane tank under the action of the circulating pump. Meanwhile, the industrial waste gas is treated by a carbon dioxide capture device to leave carbon dioxide with higher concentration. The higher concentration carbon dioxide enters the other end inlet side of the methane tank. Under the effect of the domesticated activated sludge microorganisms, the generator of the waste heat recovery module provides a required voltage environment, hydrogen and carbon dioxide react to generate methane gas, a small amount of hydrogen and carbon dioxide are doped in the methane tank due to reversible reaction, the gas generated in the methane tank is introduced into a gas purification tower, the methane gas with higher concentration is purified by doping a suitable medium, and the methane gas is introduced into a gas pipeline through a circulating pump to be used by users.

In the thermochemical cycle, cerium oxide is used as a carrier, concentrated solar energy is used as a source of high-temperature process heat, water and cerium oxide are used as raw materials, and the specific steps are shown in figure 2:

adding the cerium oxide into a reduction reactor, and absorbing solar energy by the reduction reactor to provide a high-temperature environment so as to decompose the cerium oxide into low-valence cerium oxide and oxygen. Oxygen enters an oxygen gas storage bottle, low-valence cerium oxide enters an oxidation reactor through a pipeline, and the low-valence cerium oxide and water vapor are oxidized at low temperature to generate cerium oxide and hydrogen. And returning the cerium oxide to the oxygen carrier in the reduction reactor through a pipeline for carrying out the next reduction reaction, and introducing hydrogen into the subsequent treatment.

The unused heat after the reduction reaction enters the oxidation reactor according to a first circulation direction to provide T for the reaction process_LAnd (3) temperature. First cycleThe method comprises the following specific steps: opening the valves, closing the rest valves, and allowing the residual heat of the reduction reaction to enter a first heat storage bottle; closing the valve, opening the valve, and allowing the heat of the first heat storage bottle to enter the second heat storage bottle; the valve is closed, (c) the valve is opened, and the heat of the second heat storage bottle enters the oxidation reactor. The unused heat after the oxidation reaction enters the reduction reactor according to a second circulation direction to provide T for the reaction process_HAnd (3) temperature. The second circulation direction comprises the following specific steps: opening the valve and closing the rest valves, and allowing the residual heat of the oxidation reaction to enter a second heat storage bottle; closing the valve and opening the valve, so that the heat in the second heat storage bottle enters the second heat storage bottle; and closing the valve, opening the valve and introducing the heat of the first heat storage bottle into the reduction reactor. Insufficient heat is supplemented by sunlight after heat accumulation, the heat is regenerated through the heat treatment, the circulating heat efficiency is greatly improved, and meanwhile, the gap heating in the oxidation-reduction reaction process is reflected through the linkage of the switch of the valve.

Based on the purpose of energy conservation, the invention provides a heat regeneration system for thermochemical cycle hydrogen production while gas can be separated, so that heat regeneration between two different temperatures is realized, a high-temperature gas waste heat recovery technology is applied, high-temperature gas exchanges heat through a heat exchanger, temperature reduction is realized, meanwhile, waste heat power generation can be used for providing required electric energy for a methanation system, and after unstable solar energy is converted into stable hydrogen, the transportation and storage cost of the hydrogen is higher, and meanwhile, the safety of the hydrogen is lower, so that the problem that chemical energy conversion by the current solar energy is needed to be solved urgently is solved. Based on the national condition that the aim of 'double carbon' is to be realized in China, the invention combines the carbon dioxide capture technology to generate high-quality, stable and mature methane gas by hydrogen and carbon dioxide under the action of the domesticated sludge.