A thermoelectric-assisted solar thermochemical reduction of carbon dioxide to fuel device

Abstract

A thermoelectric-assisted solar thermochemical reduction of carbon dioxide to fuel device belongs to the field of solar thermochemistry. Existing thermochemical reduction systems have the problem of low energy utilization efficiency. The solar dish concentrator irradiates the converged solar energy through the quartz window onto the foam ceramic in the reaction chamber; the thermoelectric module is placed on the outer wall of the reactor, the hot end of the thermoelectric module is connected to the cathode of the electrolytic cell through an electrode wire, and the cold end of the thermoelectric module is connected to the anode of the electrolytic cell through another electrode wire; an H2 outlet is opened at the top of the electrolytic cell and near the cathode side of the electrolytic cell, an O2 outlet is opened at the top of the electrolytic cell and near the anode side of the electrolytic cell, a CO2 inlet and a CO outlet are respectively opened on the reactor, and the CO2 inlet and the H2 outlet are connected through an air pipeline. It is used to improve the energy conversion efficiency of the fuel.

Description

Technical Field

[0001] The present invention relates to a device for reducing carbon dioxide to fuel, belonging to the field of solar thermochemistry. Background Art

[0002] Facing the problems of excessive carbon emissions and global energy depletion, the thermochemical reduction of CO 2 to fuel driven by high-flux concentrated solar energy is a reliable way with great potential for future development. The C=O double bond in the CO 2 molecule is very strong (bond energy is 750 kJ / mol), and it is very difficult to achieve the efficient conversion of CO 2 by conventional technical routes. In the technical classification of the solar thermochemistry field, only the solar thermal decomposition process and the two-step solar thermochemical cycle process can directly crack CO 4 into CO without an additional hydrogen source (such as CH 2 ). Among them, the solar thermal decomposition process requires too high a reaction temperature (at least 2000 °C), which can only be achieved under harsh experimental conditions, so there is no relevant report on successful application; the two-step thermochemical cycle process relies on the redox reaction of a variable-valence metal-based catalyst, and can produce O 2 and CO respectively in the reduction stage and the oxidation stage without an additional gas separation step. At present, there are already some laboratory-scale technology demonstrations, but the actual operating efficiency of the reported related systems has not exceeded 6%.

[0003] Currently, the key to restricting the energy conversion efficiency of the two-step thermochemical cycle system still lies in the too high reaction temperature. Although compared with the solar direct thermal decomposition of CO 2 system, the required reaction temperature of this reaction process has been reduced, but a stable thermal environment of about 1300 °C or more is still required under atmospheric pressure, which leads to two most direct factors restricting the system energy efficiency: (1) There are a large number of irreversible heat losses on the surface of the high-temperature reaction device; (2) Serious catalyst sintering problems. The above two factors directly affect the overall thermal efficiency and chemical reaction rate of the system, and further limit the final solar-fuel conversion efficiency.

[0004] The oxidation step of the two-step thermochemical cycle system is an exothermic reaction (Equation 2), and too high a reaction temperature is actually not conducive to the reaction. Therefore, the reaction process under this system is actually a non-isothermal process. After the high-temperature reduction step, it is necessary to deliberately reduce the reaction temperature, resulting in a large amount of irreversible heat loss and energy dissipation. Therefore, the reaction temperature of the whole process fundamentally depends on the cracking temperature of the catalytic material in the reduction stage (Equation 1). Comparatively speaking, the catalytic material with iron-based oxygen carriers as the main active component can exhibit relatively high reaction activity at a relatively low reduction temperature, which is beneficial to reducing the reaction temperature requirement under this system from the basic properties of the catalytic material. At the same time, if a certain reducing atmosphere is formed in the reaction area, the oxygen evolution process of the catalytic material during the reduction stage can be accelerated, thereby further reducing the required reaction temperature from the reaction conditions, reducing irreversible heat loss and alleviating the sintering problem of the catalyst. In addition, from the perspective of heat recovery, if the waste heat on the surface of the high-temperature reaction device is utilized, the energy utilization efficiency of the whole system can be further improved, increasing the conversion rate and fuel output.

[0005] The reaction expression of the two-step solar thermochemical cycle (M represents a metal element, δ is the stoichiometric number of CO 2 , and x is a positive integer):

[0006] Reduction step: MO x →MO x-δ +0.5δO 2 (Equation 1) Oxidation step: MO x-δ +δCO 2 →MO x +δCO (Equation 2) Overall reaction: CO 2 →0.5O 2 +CO (Equation 3)

[0007] Therefore, the existing thermochemical reduction system has the problem of low energy utilization efficiency. Summary of the Invention

[0008] The purpose of the present invention is to solve the problem of low energy utilization efficiency existing in the existing methods for producing syngas, and a thermoelectric-assisted solar thermochemical reduction of carbon dioxide to fuel device is proposed.

[0009] A thermoelectric-assisted solar thermochemical reduction of carbon dioxide to fuel device, the device includes a solar dish concentrator, a quartz window, a gas pipeline, an electrolytic cell, electrode wires, a thermoelectric module and a reactor;

[0010] The foam ceramic is a ceramic body with a porous foam structure, and the surface of the foam ceramic is coated with a catalyst;

[0011] The ceramic foam is disposed inside the reactor. One end of the reactor is open, and a quartz window covers the opening of the reactor. The solar dish concentrator is located outside the quartz window and faces the quartz window. The solar dish concentrator is used to irradiate the converged sunlight through the quartz window onto the ceramic foam inside the reactor.

[0012] The thermoelectric module is placed on the outer wall of the reactor, and the electrolytic cell is placed on the thermoelectric module. The hot end of the thermoelectric module is connected to the cathode of the electrolytic cell through an electrode wire, and the cold end of the thermoelectric module is connected to the anode of the electrolytic cell through another electrode wire.

[0013] An H 2 outlet is opened at the top of the electrolytic cell and near the cathode side of the electrolytic cell, and an O 2 outlet is opened at the top of the electrolytic cell and near the anode side of the electrolytic cell. A CO 2 inlet and a CO outlet are respectively opened on the reactor. The CO 2 inlet and the H 2 outlet are connected through a gas pipeline.

[0014] Preferably, the device further includes a pneumatic valve.

[0015] The pneumatic valve is disposed on the gas pipeline. The pneumatic valve is used to control the opening or closing of the H 2 outlet.

[0016] Preferably, the device further includes a stainless steel outer shell and an alumina thermal insulation ceramic.

[0017] The outer wall of the reactor is of a two-layer structure, and the two layers are, from the inside to the outside, the alumina thermal insulation ceramic and the stainless steel outer shell in sequence.

[0018] Preferably, the device further includes a fixing member.

[0019] The quartz window is fixed to the stainless steel outer shell through the fixing member.

[0020] Preferably, the fixing member includes a flange with a water-cooling channel and a fastening bolt.

[0021] The flange with a water-cooling channel is disposed at the edge of the upper surface of the quartz window. The fastening bolt passes through the flange with a water-cooling channel and is fixed to the stainless steel outer shell, clamping the quartz window between the flange with a water-cooling channel and the stainless steel outer shell.

[0022] The ceramic foam is silicon carbide ceramic foam.

[0023] The catalyst is an iron-based catalyst.

[0024] The beneficial effects of the present invention are:

[0025] A fuel production device for thermoelectric-assisted solar thermochemical reduction of carbon dioxide proposed in this application. The core of its technology is: (1) Install a thermoelectric module and an electrolytic cell on the surface of the reactor, use the outer shell of the reaction device as the hot end of the thermoelectric module, and the electrolytic cell as the cold end, and use the electricity generated by the waste heat on the surface of the reactor to carry out the process of electrolyzing water to produce hydrogen, improving the energy utilization rate of the system and fuel output; (2) Use the hydrogen produced in the electrolysis process as an auxiliary gas, introduce it into the reactor to form a reducing atmosphere and greatly reduce the reaction temperature of the two-step thermochemical cycle system, and then transform the traditional non-isothermal cycle process into an isothermal cycle process, while improving the thermal efficiency of the reaction device and alleviating the high-temperature deactivation phenomenon of the catalytic material.

[0026] The advantages of the above technical solution are as follows: on the one hand, it effectively utilizes the waste heat on the surface of the high-temperature reaction device, increasing the overall energy utilization efficiency; on the other hand, the hydrogen generated by using waste heat to generate electricity is used as an auxiliary reducing gas, reducing the overall irreversible heat loss of the system by reducing the reaction temperature and effectively alleviating the high-temperature sintering problem of the catalytic material, ultimately improving the energy conversion efficiency of solar energy to fuel. Brief Description of the Drawings

[0027] Figure 1 It is a schematic diagram of the principle of a fuel production device for thermoelectric-assisted solar thermochemical reduction of carbon dioxide. Detailed Embodiments

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0029] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0030] Next, the present invention will be further described in conjunction with the drawings and specific embodiments, but it is not a limitation of the present invention.

[0031] Embodiment 1:

[0032] Combined Figure 1 To illustrate this embodiment, a fuel production device for thermoelectric-assisted solar thermochemical reduction of carbon dioxide, the device includes a solar dish concentrator 1, a quartz window 3, a gas pipeline 4, an electrolytic cell 6, electrode wires 7, a thermoelectric module 8 and a reactor;

[0033] The foam ceramic 11 is a ceramic body with a porous foam structure, and the surface of the foam ceramic 11 is coated with a catalyst;

[0034] The ceramic foam 11 is disposed inside the reactor. One end of the reactor is open, and the quartz window pane 3 covers the opening of the reactor. The solar dish concentrator 1 is located outside the quartz window pane 3 and is placed facing the quartz window pane 3. The solar dish concentrator 1 is used to irradiate the converged sunlight through the quartz window pane 3 onto the ceramic foam 11 inside the reactor.

[0035] The thermoelectric module 8 is placed on the outer wall of the reactor, and the electrolytic cell 6 is placed on the thermoelectric module 8. The hot end of the thermoelectric module 8 is connected to the cathode of the electrolytic cell 6 through an electrode wire 7, and the cold end of the thermoelectric module 8 is connected to the anode of the electrolytic cell 6 through another electrode wire 7.

[0036] An H 2 outlet is opened at the top of the electrolytic cell 6 and near the cathode side of the electrolytic cell 6, and an O 2 outlet is opened at the top of the electrolytic cell 6 and near the anode side of the electrolytic cell 6. A CO 2 inlet and a CO outlet are respectively opened on the reactor. The CO 2 inlet and the H 2 outlet are connected through a gas pipeline 4.

[0037] In this embodiment, after the sunlight irradiates the ceramic foam, the ceramic foam absorbs the sunlight to generate heat, and this heat will be transferred to the outer wall of the reactor. The thermoelectric module converts the heat on the outer wall of the reactor into electrical energy and supplies it to the electrolytic cell.

[0038] The core of this application is to realize an additional hydrogen production function through the utilization of the waste heat on the surface of the device, and to use part of the hydrogen source to reduce the high-temperature thermochemical reaction temperature and improve the chemical conversion efficiency. The design purpose of this device is to overcome the deficiencies of the previous high-temperature thermochemical method for cracking CO 2 in the process of fuel production, such as high reaction temperature, low energy efficiency, need for additional hydrogen source, and inability to directly separate gas products.

[0039] Operating principle: The energy source of the entire reaction device is provided by solar energy. The solar radiation energy forms a high-flux heat flux after being concentrated by the dish concentrator 1, passes through the quartz window pane 3 and irradiates onto the silicon carbide ceramic foam 11 coated with an iron-based catalyst on the surface, forming a high-temperature environment (about 1000 °C) and driving a strongly endothermic redox reaction. The quartz window pane 3 is fixed and cooled by the flange 2 with a water-cooling channel to prevent damage caused by heat stress concentration. In the reaction zone, the reason for using silicon carbide ceramic foam is that it has good thermal conductivity and a relatively high specific surface area, which can create the best reaction conditions for the gas-solid two-phase exchange and catalytic reaction processes. The iron-based catalyst coated on the surface of the silicon carbide ceramic is the key active component for the two-step thermochemical cycle reaction, and it still has good CO 2Catalytic activity. The entire reaction area where the foam ceramic is located is wrapped by the alumina thermal insulation ceramic 10, and the external is supported by a stainless steel shell 9. Although the alumina thermal insulation ceramic 10 has a strong heat insulation effect, the high temperature in the reaction area will still conduct to the outside, making the temperature of the stainless steel shell 9 maintain above 100 °C. Under this condition, the thermoelectric module 8 takes this surface as the hot end and the bottom of the electrolytic cell 6 as the cold end, and generates electricity based on the Seebeck effect. The generated electricity is connected to the electrolytic cell 6 through the electrode wire 7 to electrolyze water and obtain H 2 and O 2 products. After being transported through the gas pipeline 4 and controlled by the pneumatic valve 5, part of the H 2 product is used as auxiliary gas and mixed with the raw material gas CO 2 and then sent into the high-temperature reaction zone, where a two-step thermochemical cycle reaction occurs under the action of the iron-based catalyst and a large amount of CO gas is produced.

[0040] In addition, Table 1 analyzes the two-step thermochemical cycle reaction mechanism (the set simulation conditions are: 8×φ6 cylindrical cavity, constant inlet flow rate of 1 L / min, argon carrier gas, ambient temperature of 25 °C, gas pressure of 1 atm, and the catalyst is Fe 3 O 4 / FeO cycle working fluid pair), and gives the change of the reaction degree of the iron-based catalyst when adding different contents of H 2 auxiliary gas during the reduction stage to prove the promoting effect of H 2 on reducing the reaction temperature and improving the catalytic efficiency. Under normal circumstances, the cracking temperature of the Fe 3 O 4 catalytic material is about 1500 °C, so the catalytic reaction degrees in the pure argon atmosphere in the table are all 0. When adding H 2 auxiliary gas, even if only 1% of H 2 is added to the raw material gas, there is still a 2% reaction degree at a reaction temperature of 900 K. And with the increase of the reaction temperature and the content of H 2 auxiliary gas, the catalytic reaction degree increases significantly. At a reaction temperature of 1200 K, adding 10% of H 2 auxiliary gas to the raw material gas can achieve a reaction degree of nearly 95%. That is to say, 95% of the iron-based catalyst in the reduction step is in the excited reduction state, which means that a large amount of CO 2 can be catalytically converted by the catalyst in the subsequent oxidation step. This proves that H 2 auxiliary gas can reduce the reaction temperature in the reduction step and improve the CO 2It has a significant promoting effect on the conversion rate. At the same time, a reduction temperature of around 1200K can already change the traditional non-isothermal cycle into an isothermal cycle, thereby reducing the irreversible loss during the heat transfer process. The results of the above calculation examples largely confirm the feasibility of the technical solution.

[0041] Table 1 Promotion effect of hydrogen on the cracking reaction during the reduction stage: Catalytic reaction degree (%) at different ratios and temperatures

[0042]

[0043] In a preferred embodiment, the device further includes a pneumatic valve 5;

[0044] The pneumatic valve 5 is arranged on the gas pipeline 4; the pneumatic valve 5 is used to control the opening or closing of the H 2 outlet.

[0045] In a preferred embodiment, the device further includes a stainless steel outer shell 9 and an alumina thermal insulation ceramic 10;

[0046] The outer wall of the reactor is a two-layer structure, and the two layers are, from the inside to the outside, the alumina thermal insulation ceramic 10 and the stainless steel outer shell 9 in sequence.

[0047] In a preferred embodiment, the device further includes a fixing member;

[0048] The quartz window pane 3 is fixed to the stainless steel outer shell 9 through the fixing member.

[0049] In a preferred embodiment, the fixing member includes a flange 2 with a water-cooling channel and fastening bolts;

[0050] The flange 2 with a water-cooling channel is arranged at the edge of the upper surface of the quartz window pane 3, and the fastening bolts pass through the flange 2 with a water-cooling channel and are fixed to the stainless steel outer shell 9, clamping the quartz window pane 3 between the flange 2 with a water-cooling channel and the stainless steel outer shell 9.

[0051] In a preferred embodiment, the foam ceramic 11 is a silicon carbide foam ceramic; the catalyst is an iron-based catalyst.

[0052] In this embodiment, the silicon carbide foam ceramic is a ceramic body with a porous foam structure presented after being fired with silicon carbide powder.

[0053] Although the present invention has been described herein with reference to particular embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. Accordingly, it should be understood that numerous modifications may be made to the exemplary embodiments, and other arrangements may be devised, without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the different dependent claims and the features described herein may be combined in a manner different from that described in the original claims. It should also be understood that the features described in connection with a separate embodiment may be used in other described embodiments.

Claims

1. A thermoelectric-assisted solar thermochemical reduction of carbon dioxide to fuel device, characterized in that, the device includes a solar dish concentrator (1), a quartz window pane (3), a gas pipeline (4), an electrolytic cell (6), electrode wires (7), a thermoelectric module (8) and a reactor; The foam ceramic (11) is a ceramic body with a porous foam structure, and the surface of the foam ceramic (11) is coated with a catalyst; The foam ceramic (11) is arranged in the reactor, one end of the reactor is open, the quartz window pane (3) covers the opening of the reactor, the solar dish concentrator (1) is located outside the quartz window pane (3) and is placed facing the quartz window pane (3); the solar dish concentrator (1) is used to irradiate the converged sunlight through the quartz window pane (3) onto the foam ceramic (11) in the reactor; The thermoelectric module (8) is placed on the outer wall of the reactor, the electrolytic cell (6) is placed on the thermoelectric module (8), the hot end of the thermoelectric module (8) is connected to the cathode of the electrolytic cell (6) through an electrode wire (7), and the cold end of the thermoelectric module (8) is connected to the anode of the electrolytic cell (6) through another electrode wire (7); An H outlet is provided at the top of the electrolytic cell (6) and near the cathode side of the electrolytic cell (6). 2 An O outlet is provided at the top of the electrolytic cell (6) and near the anode side of the electrolytic cell (6). 2 A CO inlet and a CO outlet are respectively provided on the reactor. The CO inlet and the H outlet are connected through the gas pipeline (4). 2 2 2 ​​​ The device further includes a pneumatic valve (5); The pneumatic valve (5) is arranged on the pneumatic pipeline (4); the pneumatic valve (5) is used to control the opening or closing of the H 2 outlet; The catalyst is Fe 3 O 4 .

2. The thermoelectric-assisted solar thermochemical reduction of carbon dioxide to fuel device according to claim 1, characterized in that, the device further includes a stainless steel outer shell (9) and an alumina thermal insulation ceramic (10); The outer wall of the reactor is a two-layer structure, and the two-layer structure is, from the inside to the outside, the alumina thermal insulation ceramic (10) and the stainless steel outer shell (9).

3. The thermoelectric-assisted solar thermochemical reduction of carbon dioxide to fuel device according to claim 1, characterized in that, the device further includes a fixing member; The quartz window pane (3) is fixed to the stainless steel outer shell (9) through the fixing member.

4. The thermoelectric-assisted solar thermochemical reduction of carbon dioxide to fuel device according to claim 3, characterized in that, The fixing member includes a flange (2) with a water cooling channel and a fastening bolt; The flange (2) with a water cooling channel is arranged at the edge of the upper surface of the quartz window pane (3), and the fastening bolt passes through the flange (2) with a water cooling channel and is fixed to the stainless steel outer shell (9), clamping the quartz window pane (3) between the flange (2) with a water cooling channel and the stainless steel outer shell (9).

5. The thermoelectric-assisted solar thermochemical reduction of carbon dioxide to fuel device according to claim 1, characterized in that, the foam ceramic (11) is a silicon carbide foam ceramic.

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