Direct carbon solid oxide flame battery for producing hydrogen by electrolyzing water at low cost

Abstract

The invention belongs to the technical field of solar energy, and particularly relates to a low-cost direct carbon solid oxide flame cell for producing hydrogen by electrolyzing water, and the direct carbon solid oxide flame cell is of an anode support type and comprises a cathode side, an electrolyte layer and an anode side; and the electrolyte layer is made of yttria-stabilized zirconia. The electrolytic cell and the fuel cell are coupled, and a water vapor concentration cell is formed between the cathode and the anode of the cell, so that the dependence of the solid oxide electrolytic cell on water electrolysis hydrogen production on external electric energy can be remarkably reduced, and the stability of water electrolysis hydrogen production is improved; rich-combustion flames are used as anode fuel gas, and the anode gas does not need to consume an external heat source for preheating; anode tail gas forms a carbon monoxide, carbon dioxide and water vapor mixture which is easy to separate for downstream fuel production; the battery operation efficiency can be effectively improved, and the water electrolysis hydrogen production cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of batteries, and in particular relates to a direct carbon solid oxide flame battery for producing hydrogen by electrolyzing water at low cost. Background Art

[0002] Hydrogen production by water electrolysis is the key to achieving energy transformation with hydrogen as the medium, and is also the main way to produce hydrogen on a large scale in the future. Solid oxide electrolyzers have attracted widespread attention in recent years due to their high hydrogen production efficiency and ability to generate a large amount of waste heat that can be utilized. However, the current solid oxide electrolyzers for hydrogen production by water electrolysis still have problems such as high hydrogen production costs, unstable renewable energy supply, and the need for a large amount of external heat sources to maintain the positive and negative electrodes of the electrolyzers. Summary of the invention

[0003] The object of the present invention is to provide a direct carbon solid oxide flame cell for producing hydrogen by electrolyzing water at low cost, so as to solve the problems existing in the background technology.

[0004] To achieve the above object, the present invention provides the following technical solution: a direct carbon solid oxide flame cell for low-cost water electrolysis to produce hydrogen, the direct carbon solid oxide flame cell is an anode-supported type, which includes a cathode side, an electrolyte layer and an anode side; the electrolyte layer material is yttria-stabilized zirconium oxide;

[0005] The anode side includes an anode layer, a variable-volume anode fuel chamber, and a spring, wherein the spring is connected to the bottom of the variable-volume anode fuel chamber, and the anode layer material is nickel-yttria-stabilized zirconia;

[0006] The variable-volume anode fuel chamber includes an anode fuel inlet and an anode tail gas outlet; the cathode side includes a cathode layer, a cathode gas diffusion layer and a cathode gas flow channel, the bottom of the cathode gas flow channel is connected to the upper part of the cathode gas diffusion layer, the bottom of the cathode gas diffusion layer is connected to the cathode layer, and the cathode layer material is lanthanum strontium manganese ore-yttria stabilized zirconia.

[0007] Preferably, the cathode side is used as a solid oxide electrolysis cell, and water electrolysis reaction occurs by continuously introducing water vapor into the cathode gas flow channel; the generated hydrogen and unreacted water vapor are discharged on the cathode side, and oxygen ions pass through the electrolyte layer to reach the anode side.

[0008] Preferably, the anode side is used as a direct carbon solid oxide flame cell. In a variable-volume anode fuel chamber, carbon dioxide gas and activated carbon solids generate carbon monoxide through a chemical reaction; carbon monoxide and oxygen ions generate carbon dioxide through an electrochemical reaction and provide part of the electrical energy for the cathode electrolysis of water; in order to maintain the pressure balance between the positive and negative electrodes of the cell, part of the carbon monoxide, carbon dioxide and water vapor mixed gas produced at the anode is discharged from the anode tail gas outlet.

[0009] Preferably, the battery includes two states: normal operation state and shutdown and charging state:

[0010] In the shutdown and charging state, first stop the supply of water vapor on the cathode side; open the anode fuel inlet, and the rich flame produced by the combustion of hydrocarbon fuel and the activated carbon mix near the anode fuel inlet and enter the anode fuel chamber with variable volume until the spring is compressed to the shortest, stop feeding, and close the anode fuel inlet. In the normal operation state, by continuously supplying water vapor with a temperature of not less than 600°C to the cathode gas flow channel, the battery cathode performs a water electrolysis reaction:

[0011] H 2 O+2e - =H 2 +O 2-

[0012] On the anode side, activated carbon containing 5 wt% iron is used as fuel and mixed with a rich flame in a variable volume anode fuel chamber to cause electrochemical oxidation of carbon monoxide and reverse Boudouard reaction. The anode reaction equation is as follows:

[0013] CO+O 2- =CO 2 +2e -

[0014] CO 2 +C=2CO

[0015] According to the above reaction formula, under normal operation of the battery, 2 mol of carbon dioxide is generated for every 1 mol of activated carbon fuel consumed. In order to maintain the pressure balance between the positive and negative electrodes of the battery, part of the anode gas is discharged from the anode tail gas outlet during operation.

[0016] Preferably, the rich flame refers to a flame produced by combustion when the oxidant provided is less than the chemical equivalent value, and the rich equivalent ratio φ is defined by the following formula:

[0017]

[0018] Preferably, the activated carbon fuel and the rich flame are mixed before entering the variable volume anode fuel chamber.

[0019] The beneficial effects of the present invention are as follows: the present invention introduces a carbon-hydrogen fuel-rich flame into the anode side of the battery, which can not only react with the anode solid carbon fuel to further produce carbon monoxide required for the electrochemical reaction but also serve as a battery startup heat source, without the need for an additional heat source to preheat the anode fuel gas; the electrochemical oxidation of carbon monoxide at the anode and the difference in water vapor concentration between the anode and the cathode are used to provide part of the electrical energy required for the cathode to generate electricity, thereby reducing dependence on external power supply and improving the stability of water electrolysis; compared with existing flame fuel cells, by installing a spring at the bottom of the anode fuel chamber, the activated carbon fuel can be more fully utilized, and the loading method is simpler; the battery anode tail gas separates nitrogen and carbon monoxide / carbon dioxide, which is easy for downstream fuel production; the battery operating efficiency can be effectively improved and the cost of water electrolysis can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of the present invention;

[0021] In the figure: 1. cathode gas flow channel; 2. cathode gas diffusion layer; 3. cathode layer; 4. electrolyte layer 5. anode layer; 6. anode fuel chamber with variable volume; 7. anode fuel inlet; 8. anode exhaust gas outlet; 9. spring; 10. activated carbon; 11. hydrocarbon fuel; 12. activated carbon conveyor belt. DETAILED DESCRIPTION

[0022] The specific implementation of the present invention is described in detail below with reference to the accompanying drawings and preferred embodiments.

[0023] like Figure 1 As shown, a low-cost direct carbon solid oxide flame battery for electrolyzing water to produce hydrogen, the battery is a Ni-YSZ (nickel-yttria-stabilized zirconia) / YSZ (yttria-stabilized zirconia) / LSM-YSZ (lanthanum strontium manganese ore-yttria-stabilized zirconia) anode supported battery, the battery operating temperature is 700-900°C, and the operating pressure is about 1.01atm;

[0024] The battery consists of a cathode side, an electrolyte layer 4 and an anode side;

[0025] The cathode side of the battery includes a cathode gas flow channel 1, a cathode gas diffusion layer 2 and a cathode layer 3; the anode side of the battery includes an anode layer 5, a variable-volume anode fuel chamber 6, an anode fuel inlet 7 and an anode tail gas outlet 8. The anode side is used as a direct carbon solid oxide flame battery. In the variable-volume anode fuel chamber, carbon dioxide gas and activated carbon solids generate carbon monoxide through chemical reactions; carbon monoxide and oxygen ions generate carbon dioxide through electrochemical reactions and provide part of the electrical energy for the cathode to electrolyze water; in order to maintain the pressure balance between the positive and negative electrodes of the battery, part of the carbon monoxide, carbon dioxide and water vapor mixed gas generated at the anode is discharged from the anode tail gas outlet.

[0026] The volume of the variable-volume anode fuel chamber 6 is adjusted by a spring 9 installed at the bottom as the activated carbon mass changes. As the activated carbon solids are continuously consumed, the spring below the anode combustion chamber gradually extends; when the spring extends to the maximum length, the battery needs to be shut down for refueling. When the battery is shut down for refueling, first stop the supply of cathode water vapor; open the anode fuel inlet on the anode side, start the activated carbon conveyor belt 12, and continue to pass the activated carbon fuel and rich flame until the spring is compressed to the shortest, and then close the anode fuel inlet.

[0027] The battery has two states: normal operation state and shutdown and charging state:

[0028] In the shutdown and feeding state, first stop the supply of water vapor on the cathode side; open the anode fuel inlet 7, and the rich flame produced by the combustion of the hydrocarbon fuel 11 and the activated carbon 10 mix near the anode fuel inlet 7 and enter the variable-volume anode fuel chamber 6 until the spring is compressed to the shortest, stop feeding, and close the anode fuel inlet 7.

[0029] Under normal operation, by continuously supplying water vapor with a temperature not less than 600°C to the cathode gas flow channel 1, the battery cathode undergoes water electrolysis reaction:

[0030] H 2 O+2e - =H 2 +O 2-

[0031] On the anode side, activated carbon containing 5 wt% iron is used as fuel and mixed with a rich flame in a variable volume anode fuel chamber 6 to cause electrochemical oxidation of carbon monoxide and reverse Boudouard reaction. The anode reaction formula is as follows:

[0032] CO+O 2- =CO 2 +2e -

[0033] CO 2 +C=2CO

[0034] According to the above reaction formula, under normal operation of the battery, 2 mol of carbon dioxide is generated for every 1 mol of activated carbon fuel consumed. In order to maintain the pressure balance between the positive and negative electrodes of the battery, part of the anode gas is discharged from the anode tail gas outlet 8 during operation.

[0035] Under normal operation, as the activated carbon is continuously consumed, the volume of the anode fuel chamber gradually decreases until the spring is stretched to its longest length and the battery needs to be shut down for refueling.

[0036] The rich flame produced by the combustion of hydrocarbon fuels mainly consists of carbon monoxide, carbon dioxide and water. The rich flame has three functions: directly serving as a starting heat source for solid oxide fuel cells, forming a water vapor concentration difference between the cathode and anode of the cell, and providing raw gas carbon monoxide for the electrochemical reaction at the anode of the cell.

[0037] The reverse Boudouard reaction was promoted by adding 5wt% iron to the activated carbon fuel, thus improving the battery operation efficiency.

[0038] The rich flame refers to the flame produced when the oxidant provided is less than the chemical equivalent value, and the rich equivalent ratio φ is defined by the following formula:

[0039]

[0041] m fuel and m air They are fuel and air flow rates, respectively. The subscript act represents the actual flow rate, and static represents the flow rate calculated based on the stoichiometric ratio.

[0042] The rich flame produced by the combustion of the hydrocarbon fuel is mainly composed of carbon monoxide, carbon dioxide and water vapor. In order to provide more electrical energy to the electrolysis of water as much as possible, it is necessary to increase the water vapor concentration difference between the positive and negative electrodes and increase the carbon monoxide content; in order to ensure that the anode side of the battery can be maintained within the normal operating temperature range during operation, it is necessary to control the flame temperature not to be too low. Therefore, selecting a hydrocarbon fuel with a higher carbon content and appropriately increasing the rich fuel equivalent ratio will help improve the battery operation efficiency while ensuring stable and safe operation of the battery. For example, when methane is selected as the fuel, it is more appropriate to control the rich fuel equivalent ratio within the range of 1.1 to 1.5.

[0043] The 5 wt% iron acts as a reverse Boudouard reaction catalyst to promote carbon monoxide production; when the battery is operated for a long enough period of thousands of hours, the catalyst deactivation requires disassembly of the variable-volume anode fuel chamber to replace the catalyst.

[0044] The present invention utilizes the electrochemical oxidation of carbon monoxide on the anode side and the difference in water vapor concentration between the positive and negative electrodes of the battery to provide part of the electric energy required for the electrolysis of water, and realizes the production of green hydrogen by consuming relatively low-cost hydrocarbon fuels; utilizes a fuel-rich flame as the anode fuel gas, and the anode gas does not need to be preheated by consuming an external heat source; and the anode tail gas forms a mixture of carbon monoxide, carbon dioxide and water vapor, which is easy to separate for downstream fuel production; effectively improves the battery operating efficiency and reduces the cost of hydrogen production by electrolysis of water.

[0045] It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A direct carbon solid oxide flame cell for low-cost water electrolysis to produce hydrogen, characterized by: The direct carbon solid oxide flame cell is an anode-supported type, which includes a cathode side, an electrolyte layer and an anode side; the electrolyte layer material is yttria-stabilized zirconia; The anode side includes an anode layer, a variable-volume anode fuel chamber, and a spring, wherein the spring is connected to the bottom of the variable-volume anode fuel chamber, and the anode layer material is nickel-yttria-stabilized zirconia; The variable-volume anode fuel chamber includes an anode fuel inlet and an anode tail gas outlet; the cathode side includes a cathode layer, a cathode gas diffusion layer and a cathode gas flow channel, the bottom of the cathode gas flow channel is connected to the upper part of the cathode gas diffusion layer, the bottom of the cathode gas diffusion layer is connected to the cathode layer, and the cathode layer material is lanthanum strontium manganese ore-yttria stabilized zirconia.

2. The direct carbon solid oxide flame cell for low-cost water electrolysis to produce hydrogen according to claim 1, characterized in that: The cathode side is used as a solid oxide electrolytic cell, and water electrolysis reaction occurs by continuously introducing water vapor into the cathode gas flow channel; the generated hydrogen and unreacted water vapor are discharged on the cathode side, and oxygen ions pass through the electrolyte layer to reach the anode side.

3. The direct carbon solid oxide flame cell for low-cost water electrolysis to produce hydrogen according to claim 2, characterized in that: The anode side is used as a direct carbon solid oxide flame battery. In the variable-volume anode fuel chamber, carbon dioxide gas and activated carbon solid generate carbon monoxide through chemical reaction; carbon monoxide and oxygen ions generate carbon dioxide through electrochemical reaction and provide part of the electrical energy for the cathode electrolysis of water; in order to maintain the pressure balance between the positive and negative electrodes of the battery, part of the carbon monoxide, carbon dioxide and water vapor mixed gas generated at the anode is discharged from the anode tail gas outlet.

4. The direct carbon solid oxide flame cell for low-cost water electrolysis to produce hydrogen according to claim 1, characterized in that: The battery has two states: normal operation state and shutdown and charging state: In the shutdown and charging state, first stop the supply of water vapor on the cathode side; open the anode fuel inlet, and the rich flame produced by the combustion of hydrocarbon fuel and the activated carbon mix near the anode fuel inlet and enter the anode fuel chamber with variable volume until the spring is compressed to the shortest, stop feeding, and close the anode fuel inlet. In the normal operation state, by continuously supplying water vapor with a temperature of not less than 600°C to the cathode gas flow channel, the battery cathode performs a water electrolysis reaction: <h2 style=";text-align:left;direction:ltr">H2O+2e<h2 style=";text-align:left;direction:ltr"> - <h2 style=";text-align:left;direction:ltr"> (H2+O)<h2 style=";text-align:left;direction:ltr"> 2- On the anode side, activated carbon containing 5 wt% iron is used as fuel and mixed with a rich flame in a variable volume anode fuel chamber to cause electrochemical oxidation of carbon monoxide and reverse Boudouard reaction. The anode reaction equation is as follows: WHAT + ABOUT 2- =CO2+2e - CO2+C=2CO According to the above reaction formula, under normal operation of the battery, 2 mol of carbon dioxide is generated for every 1 mol of activated carbon fuel consumed. In order to maintain the pressure balance between the positive and negative electrodes of the battery, part of the anode gas is discharged from the anode tail gas outlet during operation.

5. The direct carbon solid oxide flame cell for low-cost water electrolysis to produce hydrogen according to claim 4, characterized in that: The rich flame refers to the flame produced when the oxidant provided is less than the chemical equivalent value, and the rich equivalent ratio φ is defined by the following formula: .

6. The direct carbon solid oxide flame cell for low-cost water electrolysis to produce hydrogen according to claim 4, characterized in that: The activated carbon fuel and the rich flame are mixed before entering the variable volume anode fuel chamber.

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