WO2021159874A1 - Microwave heating-based thermochemical hydrogen production system, hydrogen production method therefor and use thereof - Google Patents

Abstract

Provided are a microwave heating-based thermochemical hydrogen production system, a hydrogen production method therefor and use thereof. The hydrogen production system is as follows: the inlet of a preheater (3) is in communication with a carrier gas storage device (1), and a flow controller (2) is provided therebetween; the outlet of the preheater (3) is respectively in communication with the inlet of a steam generator (13) and one end of the second-three-way valve (5) via the first-three-way valve (4); the other two ends of the second-three-way valve (5) are respectively in communication with the outlet of the superheater (14) and the inlet of a reactor (7); the reactor (7) is provided in a microwave generation device (6); the outlet of the steam generator (13) is in communication with the inlet of the superheater (14) via a pipeline; the outlet of the reactor (7), a condenser (9), a drying device (10) and a collection device (12) are successively communicated; and a chromatograph (11) is provided on a communication pipeline between the drying device (10) and the collection device (12). Microwave pyrolysis of metal oxides has the characteristics of low energy consumption and fast temperature rise, so that the cost of experiments can be reduced, the cycle of repeated experiments is reduced, and the effective energy utilization rate is greatly improved.

Description

A thermochemical hydrogen production system based on microwave heating and its hydrogen production method and application Technical field

The invention belongs to the technical field of thermochemical hydrogen production, and in particular relates to a thermochemical hydrogen production system based on microwave heating and a hydrogen production method and application thereof.

Background technique

The information disclosed in the background of the present invention is only intended to increase the understanding of the general background of the present invention, and is not necessarily regarded as an admission or in any form suggesting that the information constitutes the prior art known to those of ordinary skill in the art.

Since the 21st century, countries around the world have paid great attention to the issue of carbon dioxide emissions and global warming. People's development and utilization of energy are gradually converted to natural gas, hydrogen and other gas fuels. As the most ideal renewable energy carrier, hydrogen energy has the advantages of abundant resources, renewable, environmental protection and high efficiency. The current hydrogen production technologies are diverse, including treatment processes such as chemical, biological, electrolysis, and photolysis. The world's main liquid hydrogen production method is hydrogen production by natural gas steam reforming. At the beginning of the 21st century, Kodama and Steinfeld proposed a new type of hydrogen production technology-chemical chain steam reforming hydrogen production and synthesis gas technology. This technology combines the advantages of partial oxidation of lattice oxygen to produce synthesis gas and water splitting to produce hydrogen. The obtained hydrogen has high purity and the _{ratio of synthesis gas (H 2} /CO=2) is appropriate. For example, patent document CN110407171A discloses a thermochemical hydrogen production reaction performance evaluation system and method based on a solar concentrator simulator, which is characterized by gaseous methane, ethane, oxygen and their mixtures, or liquid methanol, ethanol, Water and its mixture are used as raw materials. The temperature of 200℃-1000℃ provided by the solar concentrator is used to react in the microchannel reactor filled with catalyst to generate hydrogen, carbon monoxide and carbon dioxide. The product is purged by inert gas and cooled by the condenser. After the reaction is over, it is collected and analyzed and tested.

At present, hydrogen production by water splitting, especially the two-step thermochemical water splitting hydrogen production has been given extensive consideration. Thermal chemical water splitting refers to a method that combines chemical reactions to decompose water at a temperature lower than that of direct thermal decomposition. Specifically, in the process of thermochemical water splitting reaction, oxides of different oxidation states undergo redox reactions to decompose water into hydrogen and oxygen. For example, metal oxides with high oxidation states are pyrolyzed into metal oxides with low oxidation states at high temperatures. With oxygen (thermal reduction reaction, the temperature is about 1500°C), the low oxidation state metal oxide reacts with water to produce hydrogen and oxidized to the high oxidation state metal oxide (hydrolysis reaction, the temperature is about 800°C). In such a thermochemical water splitting process, it is very important to reduce the temperature required for the reaction, especially to reduce the temperature required for the pyrolysis of high oxidation state metal oxides. The catalyst is very important in the thermochemical hydrogen production reaction. An effective catalyst can greatly reduce the reaction temperature of the thermochemical reaction and improve the reaction efficiency. It has been proven that doped metal oxides such as ceria and nickel ferrite can be effectively used for thermochemical water splitting.

However, the inventor believes that in the process of evaluating the hydrogen production performance of the catalyst, the economic cost of using a solar concentrator as a heat source is too high, and the temperature required for high-temperature pyrolysis of metal oxides is often as high as about 1500°C. The length of the process is 30-60 minutes, and the lengthy heating time leads to an experiment cycle of about 1.5-2h. The catalyst is prone to sintering deactivation at such a high temperature for a long time, so in terms of experiment cycle, experiment cost and energy efficiency, etc. There are still many problems.

Summary of the invention

In view of the above-mentioned problems in the prior art, the present invention aims to provide a thermochemical hydrogen production system and method based on microwave heating, and to provide a preparation and application of a microwave absorbing material. Compared with solar simulators and traditional heat treatment methods, By microwave pyrolysis of metal oxides, the heating time is short, the power consumption is low, the experiment cost is small, the repeated experiment cycle is reduced, the effective energy utilization rate is greatly improved, and the accurate analysis of the product can effectively evaluate the preparation of the catalyst. Hydrogen performance.

The first objective of the present invention is to provide a thermochemical hydrogen production system based on microwave heating.

The second objective of the present invention is to provide the thermochemical hydrogen production method based on microwave heating.

The third object of the present invention is to provide the application of the thermochemical hydrogen production system based on microwave heating and the hydrogen production method thereof.

In order to achieve the above-mentioned purpose of the invention, the present invention discloses the following technical solutions:

First of all, the present invention discloses a thermochemical hydrogen production system based on microwave heating, including: carrier gas storage device, preheater, microwave generating device, reactor, condenser, drying device, chromatograph, collecting device, steam generating And superheater. Wherein: the inlet of the preheater is in communication with the carrier gas storage device, and a flow controller is arranged between the two. The outlet of the preheater is respectively communicated with the inlet of the steam generator and one end of the second three-way valve through the first three-way valve, and the other two ports of the second three-way valve are respectively connected with the outlet and reaction of the superheater. The inlet of the reactor is connected, and the reactor is arranged in the microwave generating device. The outlet of the steam generator is communicated with the inlet of the superheater through a pipeline, the outlet of the reactor, the condenser, the drying device, and the collecting device are communicated in sequence, and the chromatograph is arranged in the communicating pipe between the drying device and the collecting device superior.

As a further technical solution, the carrier gas in the carrier gas storage device is an inert gas, such as Ar gas. In addition, nitrogen can also be used as a carrier gas.

As a further technical solution, the material of the reactor is high temperature resistant quartz.

As a further technical solution, the microwaves generated by the microwave generating device input microwave radiation into the reaction cavity through a waveguide, the reactor is placed in the reaction cavity, and a catalyst is placed in the reactor.

As a further technical solution, both the preheater and superheater are electrically heated, and the main function of the preheater is to preheat the carrier gas from the carrier gas storage device, reduce the temperature drop caused by gas-liquid mixing, and ensure The carrier gas can entrain a certain amount of water vapor, and the main function of the superheater is to heat the water vapor to the superheat temperature to ensure that the hydrolysis reaction can reach the reaction temperature (usually at 800°C).

As a further technical solution, the steam generator is a device for heating water through a water bath or an oil bath, and the water vapor generated by the steam generator is carried by a carrier gas into the superheater.

As a further technical solution, the drying device adopts a water removal device, whose main function is to remove water in the product.

As a further technical solution, the water removal device is a container filled with color-changing silica gel, and the gaseous product is driven by the carrier gas to enter the water removal device to achieve dehydration.

As a further technical solution, the connecting pipe between the reactor inlet and the superheater outlet is provided with insulation materials.

As a further technical solution, the condenser has a jacketed structure, and the pumping device can realize condensate circulation. The condenser also includes a trap for storing liquid water condensed from the gaseous product.

As a further technical solution, the chromatograph is used to detect the generated mixed gas composition.

As a further technical solution, it also includes a resistance furnace, which is used to heat the reactor in the hydrolysis reaction, so that the catalyst therein reacts with water to generate hydrogen and oxidize it to a high oxidation state metal oxide. The invention can effectively explore the hydrogen production performance of the catalyst through the combined use of the microwave generating device and the traditional heating equipment.

Further, when using the absorbing catalyst for hydrogen production, the microwave generating device is used to heat the absorbing catalyst in a protective atmosphere to realize the conversion of the high oxidation state metal oxide supported on the absorbing catalyst to the low oxidation state metal oxide The low oxidation state metal oxide can further undergo a hydrolysis reaction with water vapor under heating conditions to be oxidized into a high oxidation state metal oxide and generate hydrogen gas. The high oxidation state metal oxide repeats the above-mentioned transition to a low oxidation state metal oxide. Steps of transformation.

Further, when a microwave generator is used to heat the absorbing catalyst under a protective atmosphere to convert the supported high-oxidation state metal oxides into low-oxidation state metal oxides, the heating power is 500-900W, and the heating time is 3- 5min. This time is significantly reduced compared to the 0.5-1h time required by solar simulators or traditional heating tools, thereby reducing the cycle time and experiment costs.

Further, when a microwave generating device is used to heat the low-oxidation state metal oxide in a protective atmosphere, the heating power is 500-900W when the hydrolysis reaction occurs with water vapor.

Furthermore, when a microwave generator is used to produce hydrogen by thermochemical water splitting, the continuous regeneration of hydrogen can be realized by performing oxidation and reduction reactions under microwave and other power conditions.

Furthermore, when a microwave generator is used for thermochemical water splitting to produce hydrogen, the oxidation and reduction reactions are carried out under the condition of microwave variable power, that is, the oxidation reaction is carried out at a higher power, and the hydrolysis reaction is carried out at a lower power, which can realize the continuous hydrogen regeneration.

As a further technical solution, the catalyst is a metal oxide supported on a porous absorbing substrate, or a metal oxide doped with a strong absorbing substance, or pressed into a metal oxide with a porous structure. The metal oxides include, but are not limited to, iron-based oxides, cerium-based oxides, and perovskite-based oxides, and the absorbing matrix includes, but is not limited to, porous silicon carbide ceramic foam.

Secondly, the present invention discloses the thermochemical hydrogen production method based on microwave heating, and the specific steps are as follows:

(1) Put the catalyst into the reactor, and place the reactor in the reaction chamber of the microwave generator to ensure the tightness of the connecting pipeline, open all the valves of the three-way valve, open the carrier gas and set the carrier gas flow to the system Purge each part;

(2) Adjust the state of the three-way valve to form only the carrier gas storage device → flow controller → preheater → reactor passage, turn on the preheater/steam generator/superheater, and wait for the preheater/steam generator/ The superheater reaches the preset temperature;

(3) Set the heating power and heating time of the microwave generator. After the preheater/steam generator/superheater reaches the preset temperature, run the microwave generator for thermal reduction reaction;

(4) After the thermal reduction reaction is over, adjust the state of the three-way valve to form a carrier gas storage device→flow controller→preheater-steam generator-superheater-reactor path, set the microwave heating power and heating time and run Microwave generator for hydrolysis reaction;

(5) The cooled and dried gaseous products are detected and analyzed in a chromatograph.

Furthermore, the present invention discloses the thermochemical hydrogen production method based on microwave combined with conventional heating equipment, and the specific steps are as follows:

(1) Put the catalyst into the reactor, and place the reactor in the reaction chamber of the microwave generator to ensure the tightness of the connecting pipeline, open all the valves of the three-way valve, open the carrier gas and set the carrier gas flow to the system Purge each part;

(2) Adjust the state of the three-way valve to form only the carrier gas storage device → flow controller → preheater → reactor path, turn on the preheater/superheater, and wait for the preheater/superheater to reach the preset temperature;

(3) Set the heating power and heating time of the microwave generator. After the preheater/superheater reaches the preset temperature, run the microwave generator for thermal reduction reaction;

(4) After the thermal reduction reaction is over, transfer the reactor and its connecting pipes to the resistance furnace, turn on the steam generator/resistance furnace, and wait for the steam generator/resistance furnace to reach the preset temperature;

(5) When the steam generator/resistance furnace reaches the preset temperature, adjust the state of the three-way valve to form a carrier gas storage device→flow controller→preheater-steam generator-superheater-reactor path to carry out the hydrolysis reaction ；

(6) The cooled and dried gaseous products are detected and analyzed in a chromatograph.

Finally, the present invention discloses the application of the thermochemical hydrogen production system based on microwave heating in the energy field.

Compared with the prior art, the present invention has achieved the following beneficial effects:

(1) The present invention uses microwave pyrolysis of metal oxides, which has the characteristics of low energy consumption and fast heating: when using solar simulators or traditional heating tools to perform the reduction step, it usually needs to be heated for 0.5-1h to have obvious thermal reduction. When the microwave acts on the material with strong absorbing properties, it can dissipate the electromagnetic wave in a short time and the temperature rises rapidly. It only takes 3-5min to complete the thermal reduction step. Therefore, the hydrogen production device involved in the present invention utilizes the hot spot effect of microwave heating to effectively solve the problem of long heat treatment time in the thermochemical cycle hydrogen production process.

(2) The present invention uses microwave heating to perform oxidation and reduction reactions. Compared with traditional heating equipment and solar simulators, the present invention not only greatly reduces the cycle period, but also reduces radiation heat loss and heat dissipation loss, and while generating a large amount of hydrogen, it improves In order to improve the energy utilization rate, when silicon carbide is used as the absorbing substrate in the present invention, it is found that not only the metal oxide can be heated by its own microwave heating effect, but also the sharp discharge phenomenon of the catalyst under the microwave field can strengthen the water decomposition reaction process. On the one hand, it can directly produce high-temperature hot spot effects. On the other hand, plasma will be generated locally, which is reflected in the plasma effect. It will also be accompanied by a photocatalytic reaction, creating a locally enhanced reaction environment.

(3) In view of the impact of the discharge phenomenon on the catalyst performance evaluation, the present invention uses the combined use of microwave generators and traditional heating equipment, that is, using traditional heating equipment to heat the reactor for the hydrolysis reaction, and can simulate solar heating to explore the hydrogen production performance of the catalyst. , Not only reduces the cycle time, but also reduces the cost of experimentation.

(4) Compared with the complexity and difficulty of the solar simulator in experimental cost, equipment adjustment and temperature control, the present invention uses the microwave generator as the heat source to be simple and efficient. Industrial microwave equipment and ordinary household microwave ovens can be used for experimental exploration.

(5) In general, directly prepared powdered metal oxides that can be used for thermochemical hydrogen production are weak absorbing materials, which are difficult to heat to the temperature to achieve the thermal reduction reaction in a microwave field, and have poor cycle stability and are easy to be Entrained out. The invention directly presses the metal oxide on a strong wave absorbing material or doped with a strong wave absorbing material to form a porous structure, which can meet the requirements of the thermal reduction reaction, and has better high temperature resistance characteristics and cycle stability.

Description of the drawings

The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention, and do not constitute an improper limitation of the present invention.

Fig. 1 is a schematic structural diagram of a thermochemical hydrogen production system based on microwave heating in the first embodiment of the present invention.

2 is a microstructure diagram of a porous silicon carbide ceramic foam (left picture) and a silicon carbide ceramic foam loaded with high oxidation state metal oxides (right picture) in a second embodiment of the present invention.

Fig. 3 is a diagram of the hydrogen production rate of thermochemical hydrogen production under the microwave power of 900W in the second embodiment of the present invention (left picture) and the hydrogen production obtained by 5 cycles (right picture).

Fig. 4 is a graph showing changes in hydrogen and oxygen concentration of thermochemical hydrogen production under 700W microwave power in the third embodiment of the present invention and the hydrogen production obtained from 5 cycles.

Figure 5 shows the changes in the hydrogen and oxygen concentrations of thermochemical hydrogen production under 500W microwave power in the fourth embodiment of the present invention and the hydrogen production obtained from 5 cycles.

Fig. 6 is a scanning electron microscope image of the fresh catalyst and the catalyst under 700W microwave power after 3 cycles in the fifth embodiment of the present invention.

The signs in the above drawings respectively represent: 1-carrier gas storage device, 2-flow controller, 3-preheater, 4-first three-way valve, 5-second three-way valve, 6-microwave generating device, 7 -Reactor, 9- Condenser, 10- Drying device, 11- Chromatograph, 12- Collecting device, 13- Steam generator, 14- Superheater, 15- Resistance furnace, 16- Water trap.

Detailed ways

It should be noted that the following detailed descriptions are all illustrative and are intended to provide further descriptions of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

It should be noted that the terms used here are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should also be understood that when the terms "comprising" and/or "including" are used in this specification, they indicate There are features, steps, operations, devices, components, and/or combinations thereof.

For the convenience of description, if the words "up", "down", "left" and "right" appear in the present invention, they only indicate that they are consistent with the up, down, left, and right directions of the drawings themselves, and do not limit the structure, but only It is for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the pointed device or element needs to have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention.

Term explanation part: The terms "installed", "connected", "connected", "fixed" and other terms in the present invention should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or a whole; It can be a mechanical connection, an electrical connection, a direct connection, or an indirect connection through an intermediate medium, an internal connection between two components, or an interaction relationship between two components. For those of ordinary skill in the art The specific meaning of the above terms in the present invention can be understood according to the specific situation.

As described in the background art, the existing use of solar concentrating simulators as a heat source to produce hydrogen has problems such as experimental cycle, experimental cost, and energy efficiency. Therefore, the present invention proposes a thermochemical hydrogen production system based on microwave heating, a wave absorbing catalyst, and a preparation method and use method thereof; the present invention will now be further described with reference to the accompanying drawings and specific embodiments.

The first embodiment , referring to Figure 1, illustrates a thermochemical hydrogen production device based on microwave heating designed in the present invention, including a carrier gas storage device 1, a flow controller 2, a preheater 3, a first three-way valve 4, The second three-way valve 5, the microwave generating device 6, the reactor 7, the condenser 9, the drying device 10, the chromatograph 11, the collecting device 12, the steam generator 13, the superheater 14, the resistance furnace 15 and the equipment used to connect The piping system.

Wherein, the inlet of the preheater 3 is in communication with the carrier gas storage device 1, and a flow controller 2 is arranged between the two. The carrier gas storage device 1 is used to store nitrogen, inert gas, etc. The main function of the carrier gas is to carry the water vapor generated by the steam generator 13.

The outlet of the preheater 3 is respectively communicated with the inlet of the steam generator 13 and one end of the second three-way valve 5 through the first three-way valve 4, and the other two ports of the second three-way valve 5 are respectively connected to the superheater The outlet of the vessel 14 communicates with the inlet of the reactor 7, and the outlet of the steam generator 13 communicates with the inlet of the superheater 14 via a pipe. Both the preheater 3 and the superheater 14 adopt electric heating. The preheater 3 preheats the carrier gas from the carrier gas storage device and enters the steam generator 13 through the first three-way valve. The main function of the superheater 14 is to heat the water vapor to the superheating temperature.

The reactor 7 is arranged in the microwave generating device 6. The microwave generated by the microwave generating device 6 inputs microwave radiation into the reaction chamber through a waveguide. The reactor 7 is placed in the reaction chamber. When hydrogen is prepared, a catalyst needs to be placed in the reactor.

The outlet of the reactor 7, the condenser 9, the drying device 10, and the collecting device 12 are sequentially connected through a pipeline, and the chromatograph 11 is arranged on the connecting pipeline between the drying device 10 and the collecting device 12. The chromatograph is used to detect the components of the generated mixed gas, and through accurate analysis of the product, the effective evaluation of the hydrogen production performance of the catalyst is realized.

The high oxidation state metal oxide undergoes thermal reduction reaction under the high temperature provided by the high microwave generator and the protective atmosphere provided by the carrier gas storage device 1 (at this time, only the carrier gas storage device 1 → flow controller 2 → preheater 3 → The reactor 7 has a passage), and is pyrolyzed into low-oxidation state metal oxides and oxygen. The oxygen passes through the condenser 9 and the drying device 10 in sequence, and then enters the collection device 12 for collection. Then the low-oxidation state metal oxide is continuously hydrolyzed with superheated steam at a lower temperature to produce hydrogen and oxidized to high-oxidation state metal oxide (at this time, a carrier gas storage device 1 → flow controller 2 → preheating is formed 3-steam generator 13-superheater 14-reactor 7 (passage).

It is understandable that on the basis of the first embodiment, technical solutions including but not limited to the following can also be derived to solve different technical problems and achieve different purposes of the invention. Specific examples are as follows:

In the second embodiment , the condenser has a jacketed structure, and the jacket is provided with a water inlet and a water outlet, and the circulation of condensate in the jacket can be realized by a pumping device. The lower end of the condenser also contains a trap for storing liquid water condensed from the gaseous product. Since the oxygen/hydrogen from the reactor is produced at high temperature during the reaction process, it is necessary to cool down these gases before collecting them to ensure the safety of gas storage; in addition, there will be part of unreacted hydrogen in hydrogen. Therefore, it needs to be removed by condensation to ensure the purity of the collected hydrogen.

In the third embodiment , the drying device 10 adopts a dewatering device. The dewatering device is a container containing color-changing silica gel. The gaseous product is driven by the carrier gas to enter the dewatering device to achieve dehydration. Since the superheated water vapor is required to react with the low oxidation state metal oxide in the hydrolysis reaction of hydrogen production, the obtained hydrogen contains unreacted water vapor. In order to ensure the purity of the collected hydrogen, it needs to be condensed after condensation. A drying device is further used to ensure hydrogen drying.

In the fourth embodiment , the reactor is made of quartz. Since the reactor is a place for thermal reduction reaction, the reactor needs to be able to withstand the temperature environment required for the reaction, and the high temperature resistance of quartz can well meet the above conditions. .

In the fifth embodiment , the connecting pipe between the reactor inlet and the superheater outlet is provided with insulation materials. It can prevent the pipe connecting the inlet of the reactor and the outlet of the superheater from consuming heat energy unnecessarily; the heat-insulating material adopts quartz heat-insulating cotton.

In the sixth embodiment , the hydrogen production device further includes a resistance furnace 15 for heating the reactor 7 during the hydrolysis reaction. The high oxidation state metal oxide undergoes a thermal reduction reaction at the high temperature provided by the high microwave generator, and is pyrolyzed into low oxidation state metal oxide and oxygen. The oxygen gas passes through the condenser 9, the drying device 10, and then enters the collection device 12 for collection. . Then, the loaded low-oxidation state metal oxide is placed in the resistance furnace 15 to react with water at a relatively low temperature to generate hydrogen gas and oxidize to the high-oxidation state metal oxide (hydrolysis reaction).

The seventh embodiment , the preparation of a wave absorbing catalyst, includes the following steps:

(1) Weigh the precursor compounds of the redox active material: Mg(NO ₃ ) ₂ ·6H ₂ O, Ni(NO ₃ ) ₂ ·6H ₂ O, Co(NO ₃ ) ₂ ·6H ₂ O, Fe(NO _{3) 3} · 9H ₂ O, according to which four metal cation equimolar (both 0.01 mol) was weighed. Then, the weighed precursor compound of the redox active substance is dissolved in 4 times its mass in ionized water, and stirred with a glass rod for 300 revolutions to form an aqueous suspension solution.

(2) Add ethylenediaminetetraacetic acid (EDTA) and citric acid to the aqueous suspension solution of step (1) and stir evenly with a glass rod; the ethylenediaminetetraacetic acid (EDTA) and citric acid respectively account for moles of metal cations 60% and 75% of the total.

(3) Adjust the pH value of the aqueous suspension solution prepared in step (2) to 11 with a 1 mol/L NaOH solution, and the solution turns dark brown for use.

(4) Put the dark brown solution obtained in step (3) into a 90°C water bath, stir to evaporate the water until the solution turns into a colloid.

(5) Weigh and record the mass of the porous silicon carbide ceramic foam (shown on the left in Figure 2), put it into the colloidal solution obtained in step (4) and coat it evenly; then place the porous silicon carbide ceramic foam Electric heating constant temperature drying oven, set the drying temperature between 150 ℃, and dry overnight.

(6) The porous silicon carbide ceramic foam obtained after drying in step (5) is placed in a quartz reactor, and then the reactor is placed in the reaction chamber of a microwave generator for calcination to convert the precursor compound of the redox active substance into Corresponding metal oxide (catalyst): The power of the microwave generator is set to 900W, the calcination time is 30min, and 300ml/min nitrogen gas is continuously introduced into the reactor during the calcination process.

(8) After the reactor is cooled to normal temperature, take out the silicon carbide ceramic foam supporting the catalyst, weigh and calculate the load, and obtain the absorbing catalyst ( _{silicon carbide ceramic foam supporting (FeCoMgNi)O x} ), as shown in Figure 2 As shown in the right figure, it can be seen that the silicon carbide ceramic foam is loaded with black high oxidation state metal oxide (FeCoMgNi)O _x .

Furthermore, in the present invention, a thermochemical hydrogen production experiment based on microwave heating was carried out through the hydrogen production device illustrated in the above-mentioned embodiments, and the details are as follows.

The eighth embodiment , a thermochemical hydrogen production method based on microwave heating, includes the following steps:

(1) The catalyst prepared in the seventh embodiment ( _{the silicon carbide ceramic foam supporting about 2g (FeCoMgNi)O x} ) is placed in the reactor 7, and the reactor is placed in the microwave generating device 6, and a preheater is set. The temperature of 3 is 50°C, the temperature of steam generator 13 is set to 80°C, the temperature of superheater is set to 200°C, the first three-way valve 4 and the second three-way valve 5 are opened to form a carrier gas storage device 1 → flow control Reactor 2→Preheater 3→Reactor 7 has a path, ready to perform thermal reduction reaction.

(2) When the temperature of the preheater 3, the steam generator 13 and the superheater reach the above preset value, open the gas outlet valve of the carrier gas storage device 1, set the flow rate of the flow controller 2 to 300ml/min, and use nitrogen to purge the reaction System for 5 minutes, exhaust the air in the reaction system, and fill the reaction system with nitrogen.

Power (3) is provided a microwave generator 6 is 900W, the heating time 3min, in a protective atmosphere provided by a nitrogen gas, a high oxidation state of the metal oxide supported on the silicon carbide ceramic foam (FeCoMgNi) O _x thermal reduction reaction, and heat It is decomposed into low-oxidation state metal oxides and oxygen. The oxygen passes through the cooling device 9, and the water drying device 10 is collected by the collection device 12; the chromatograph 11 detects the composition of the mixed gas.

(4) After the thermal reduction reaction is over, set the microwave power to 900W and the heating time to 20min, adjust the first three-way valve 4 and the second three-way valve 5 to form a carrier gas storage device 1 → flow controller 2 → preheating Reactor 3-steam generator 13-superheater 14-reactor 7 pass, operate the microwave generating device for hydrolysis reaction, the hydrogen and unreacted water vapor produced by the reaction pass through the cooling device 9, and the drying device 10 is collected by the collection device 12 , The chromatograph 11 detects the components of the mixed gas.

(5) Repeat steps (1)-(4) to summarize the data obtained from 5 cycles. Specifically, the circulation process is realized by the cyclic conversion of high oxidation state metal oxides and low oxidation state metal oxides in the reactor, that is, the high oxidation state metal oxides produced by the hydrolysis reaction are pyrolyzed at a high temperature. After it is a low oxidation state metal oxide and oxygen, the low oxidation state metal oxide continues to undergo a hydrolysis reaction, and each completion of a continuous hydrogen generation process is recorded as a cycle.

The ninth embodiment , a thermochemical hydrogen production method based on microwave heating, is the same as the eighth embodiment, the difference is: step (3) set the power of the microwave generator to 700W, step (4) after the thermal reduction reaction is over, set The microwave power is 700W, and the heating time is 30min.

The tenth embodiment is a thermochemical hydrogen production method based on microwave heating. Same as the eighth embodiment, step (3) set the power of the microwave generator to 500W, and step (4) after the thermal reduction reaction is over, set the microwave power to 500W, heating time is 30min.

Fig. 3 is the change data of hydrogen and oxygen concentration and the obtained hydrogen production data of the five thermochemical cycles of water splitting to produce hydrogen under the condition of 900W in the eighth embodiment. It can be seen that under this condition, hydrogen production can be continued for about 20 minutes, with a peak output of 27.3 ± 1.5 ml/g, and after 5 cycles, the output is stable at about 15 ml/g.

Furthermore, by adjusting the microwave power to 700W (as shown in Figure 4) and 500W (as shown in Figure 5), the hydrolysis process can be continued for 30 minutes, and the peak hydrogen production is 122±5ml/g and 67.7±4ml/g, respectively , Much higher than the output of 900W. After 5 cycles under 700W conditions, the hydrogen production stabilized at about 40ml/g, and during the second cycle of the maximum production, there was a strong discharge phenomenon, which strengthened the decomposition of water, making hydrogen production and sustained The time has been significantly improved. After 5 cycles under 500W conditions, the hydrogen production is stable at about 33ml/g, after 5 cycles (120min), about 315ml of hydrogen can be produced per gram of catalyst.

As shown in Fig. 6, the left picture shows the catalyst supported on the silicon carbide ceramic foam that has not been used in the eighth embodiment. It can be seen that the catalyst is loose and has small particles. After three cycles under 700W conditions, the catalyst still retains the state of small particles, and there is no obvious sintering phenomenon, and the hydrogen production activity of the catalyst in the fourth cycle is still high (as shown in Figure 4).

The eleventh embodiment , a thermochemical hydrogen production method based on microwave heating, is the same as the eighth embodiment, the difference is: in step (4), after the thermal reduction reaction is completed, the reactor 7 and the connected pipeline are transferred to the resistor Furnace 15, the resistance furnace is set to operate at 800°C, that is, in this embodiment, a resistance furnace is used instead of microwave heating as a heat source to heat the low oxidation state metal oxides generated in the reactor with water vapor for hydrolysis reaction to produce hydrogen.

The twelfth embodiment , a thermochemical hydrogen production method based on microwave heating, is the same as the eleventh embodiment, except that steps (1)-(5) are repeated, and step (3) sets the power of the microwave generator to 700W .

The thirteenth embodiment , a thermochemical hydrogen production method based on microwave heating, is the same as the eleventh embodiment, except that steps (1)-(5) are repeated, and the power of the microwave generator is set to 500W in step (3).

In addition, it can also be seen from the above-mentioned embodiments that when the hydrogen production device and method of the present invention are used, the thermal reduction time only needs 3-5 min (as in step (3) of the eighth embodiment). Moreover, the hydrogen production is high under the power conditions such as microwave, the catalyst has good activity and durability, the system balance time is short, the operation is stable, and the output data error is small. Compared with the solar concentrating simulator and the traditional heating equipment, the running time is long and the cost is high, the hydrogen production device and method of the present invention have more prominent technical advantages.

In the above description, many specific details are set forth in order to fully understand the present invention. However, the above description is only a preferred embodiment of the present invention. The present invention can be implemented in many other ways different from those described herein, so the present invention is not limited by the specific implementation disclosed above. At the same time, any person skilled in the art can use the methods and technical content disclosed above to make many possible changes and modifications to the technical solution of the present invention without departing from the scope of the technical solution of the present invention, or modify it into an equivalent implementation of equivalent changes. example. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims (10)

1. A thermochemical hydrogen production system based on microwave heating, which is characterized in that it comprises:

   The inlet of the preheater is connected with the carrier gas storage device and a flow controller is set between the two;

   The outlet of the preheater is respectively communicated with the inlet of the steam generator and one port of the second three-way valve through the first three-way valve; the other two ports of the second three-way valve are respectively communicated with the outlet of the superheater and the reactor inlet;

   The reactor is arranged in the microwave generating device; the outlet of the steam generator is connected with the inlet of the superheater through a pipe;

   The outlet of the reactor, the condenser, the drying device, and the collecting device are connected in sequence;

   The chromatograph is arranged on the connecting pipe between the drying device and the collecting device.
2. The thermochemical hydrogen production system based on microwave heating according to claim 1, wherein the carrier gas in the carrier gas storage device is an inert gas or nitrogen;

   Alternatively, the material of the reactor is high temperature resistant quartz;

   Alternatively, the microwaves generated by the microwave generating device input microwave radiation into the reaction cavity through a waveguide, and the reactor is placed in the reaction cavity;

   Alternatively, both the preheater and the superheater are electrically heated;

   Alternatively, the steam generator is a device that heats water through a water bath or an oil bath.
3. The thermochemical hydrogen production system based on microwave heating according to claim 1, wherein the drying device adopts a water removal device; preferably, the water removal device is a container containing color-changing silica gel;

   Alternatively, the connecting pipe between the reactor inlet and the superheater outlet is provided with insulation materials;

   Alternatively, the condenser has a jacketed structure and can be pumped to realize condensate circulation; preferably, the condenser further includes a trap.
4. The thermochemical hydrogen production system based on microwave heating according to any one of claims 1 to 3, further comprising a resistance furnace for heating the reactor in the hydrolysis reaction.
5. A method of thermochemical hydrogen production based on microwave heating, characterized in that it is executed by the thermochemical hydrogen production device according to any one of claims 1-3, and the specific steps are as follows:

   (1) Put the catalyst into the reactor, and place the reactor in the reaction chamber of the microwave generator to ensure the tightness of the connecting pipeline, open all the valves of the three-way valve, open the carrier gas and set the carrier gas flow to the system Purge each part;

   (2) Adjust the state of the three-way valve to form only the carrier gas storage device → flow controller → preheater → reactor passage, turn on the preheater/steam generator/superheater, and wait for the preheater/steam generator/ The superheater reaches the preset temperature;

   (3) Set the heating power and heating time of the microwave generator. After the preheater/steam generator/superheater reaches the preset temperature, run the microwave generator for thermal reduction reaction;

   (4) After the thermal reduction reaction is over, adjust the state of the three-way valve to form a carrier gas storage device→flow controller→preheater-steam generator-superheater-reactor path, set the microwave heating power and heating time and run Microwave generator for hydrolysis reaction;

   (5) The cooled and dried gaseous products are detected and analyzed in a chromatograph.
6. A method of thermochemical hydrogen production based on microwave heating, characterized in that it is executed by the thermochemical hydrogen production device of claim 4, and the specific steps are as follows:

   (1) Put the catalyst into the reactor, and place the reactor in the reaction chamber of the microwave generator to ensure the tightness of the connecting pipeline, open all the valves of the three-way valve, open the carrier gas and set the carrier gas flow rate to the system Purge each part;

   (2) Adjust the state of the three-way valve to form only the carrier gas storage device → flow controller → preheater → reactor path, turn on the preheater/superheater, and wait for the preheater/superheater to reach the preset temperature;

   (3) Set the heating power and heating time of the microwave generator. After the preheater/superheater reaches the preset temperature, run the microwave generator for thermal reduction reaction;

   (4) After the thermal reduction reaction is over, transfer the reactor and its connecting pipes to the resistance furnace, turn on the steam generator/resistance furnace, and wait for the steam generator/resistance furnace to reach the preset temperature;

   (5) When the steam generator/resistance furnace reaches the preset temperature, adjust the state of the three-way valve to form a carrier gas storage device→flow controller→preheater-steam generator-superheater-reactor path to carry out the hydrolysis reaction ；

   (6) The cooled and dried gaseous products are detected and analyzed in a chromatograph.
7. The thermochemical hydrogen production method based on microwave heating according to claim 5, characterized in that, when a microwave generator is used for thermochemical water splitting to produce hydrogen, oxidation and reduction reactions are carried out under microwave power conditions to achieve continuous hydrogen production. regeneration.
8. The method of thermochemical hydrogen production based on microwave heating according to claim 5, characterized in that, when a microwave generator is used for thermochemical water splitting to produce hydrogen, oxidation and reduction reactions are carried out under microwave power-changing conditions, that is, the oxidation reaction is The hydrolysis reaction is carried out at a higher power, and the hydrolysis reaction is carried out at a lower power to realize the continuous regeneration of hydrogen.
9. The thermochemical hydrogen production method based on microwave heating according to any one of claims 5-8, wherein the catalyst is a metal oxide supported on a porous absorbing substrate, or is doped with a strong absorbing material Metal oxide, or pressed into a metal oxide having a porous structure; preferably, the metal oxide includes iron-based oxides, cerium-based oxides, and perovskite-based oxides; preferably, the absorbing matrix Includes porous silicon carbide ceramic foam.
10. The application of the thermochemical hydrogen production system based on microwave heating according to any one of claims 1 to 4 and/or the application of the thermochemical hydrogen production method based on microwave heating according to any one of claims 5-9 in the energy field.

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