Solid oxide electrolytic reactor and system for producing hydrogen by coupling electrolyzed water with combustible gas

Abstract

The invention discloses a solid oxide electrolysis reactor and system for producing hydrogen by coupling electrolytic water with combustible gas, the solid oxide electrolysis reactor comprises an anode end plate, an intermediate plate assembly and a cathode end plate which are connected in sequence, the intermediate plate assembly comprises a plurality of repetitive units, and the repetitive units are connected through connecting plates; the repeating unit comprises an electrolytic tank, the electrolytic tank comprises an anode, an electrolyte and a cathode, water vapor or a water vapor and hydrogen mixed gas is introduced into the cathode to generate an electrolyzed water reduction reaction to obtain hydrogen, and a combustible gas, water vapor and / or carbon dioxide mixed gas is introduced into the anode to generate hydrogen; and the combustible gas and oxygen ions which are generated by electrolyzing water at the cathode and are transmitted to the anode are subjected to deep oxidation reaction to obtain carbon dioxide. The cathode product gas is high-purity hydrogen or high-purity hydrogen obtained after condensation, the anode product gas is mixed gas of water vapor and carbon dioxide or mixed gas mainly comprising water vapor and carbon dioxide, and self-enriched high-concentration carbon dioxide can be obtained after condensation.

Description

Technical Field

[0001] The invention relates to a method and device for producing hydrogen by electrolyzing water, and in particular to a solid oxide electrolysis stack and system for producing hydrogen by electrolyzing water coupled with combustible gas. Background Art

[0002] At present, hydrogen is mainly obtained through the reforming of fuels such as coal and natural gas, and a large amount of carbon dioxide is emitted during the production process. Water electrolysis is the main method of producing green hydrogen. It uses electricity generated by clean energy such as solar energy and wind energy to electrolyze water to produce hydrogen. It can not only achieve sustainable production of hydrogen, but also promote the large-scale consumption of intermittent renewable energy. Alkaline electrolysis (ALK) and proton exchange membrane electrolysis (PEM) are relatively mature water electrolysis technologies. The operating temperature does not exceed 90°C, and the electrolysis power consumption per kilogram of hydrogen is 54kWh and 52kWh respectively.

[0003] Solid oxide electrolysis cell (SOEC) is an emerging high-temperature water electrolysis hydrogen production technology, most of which use oxygen ion conductive oxides (such as yttria stabilized zirconia, etc.) as electrolyte membranes. First, water vapor is decomposed into hydrogen and oxygen ions under the catalytic action of an external electric field and the cathode, namely:

[0004] 4 H2O (c) + 8 e - → 4 H2 (c) + 4 O 2- (c) (1)

[0005] Driven by an external electric field, oxygen ions are transported from the cathode side of the electrolyte diaphragm to the anode side, that is:

[0006] 4 O 2- (c) → 4 O 2- (a) (2)

[0007] Oxygen ions couple with each other under the catalytic action of the anode to generate oxygen, namely:

[0008] 4 O 2- (a) → 2 O2 (a) + 8 e - (3)

[0009] The overall reaction of SOEC water electrolysis is:

[0010] 4 H2O (c) → 4 H2 (c) + 2 O2 (a) (4)

[0011] The working temperature of SOEC is generally 500-850℃. High temperature operation reduces the electrolysis power consumption to 37.5-46kWh per kilogram of hydrogen. At present, electricity costs account for 70% of the cost of hydrogen production by water electrolysis. The high cost leads to a very low proportion of hydrogen production by water electrolysis in the global hydrogen supply (about 4%). This urgently requires the development of high-efficiency, low-cost and long-life hydrogen production technology by water electrolysis.

[0012] CN107180985A introduces low-concentration coalbed methane containing CH4 into the anode side of SOEC, and CN107868962A introduces a mixture of carbon powder, catalyst and molten salt into the anode side of SOEC, so that the oxygen ions generated by electrolysis and transmitted to the anode side react with hydrocarbon fuel or solid carbon to generate synthesis gas or carbon monoxide, thereby reducing the power consumption of the electrolysis process. However, the hydrocarbon fuel (such as CH4) input at the anode inlet is easy to crack and carbonize at high temperature, that is:

[0013] CH4 → 2 H2 + C (5)

[0014] Carbon monoxide in the anode reaction product will also undergo Boudouard disproportionation reaction to produce solid carbon, namely:

[0015] 2 CO → CO2 + C (6)

[0016] These solid carbons will be deposited in the porous anode, destroying the microstructure of the anode, causing the performance of the electrolytic cell to deteriorate or even completely fail. Summary of the invention

[0017] Purpose of the invention: In order to overcome the deficiencies in the prior art, the purpose of the present invention is to provide a solid oxide electrolysis stack for producing hydrogen by electrolysis of water coupled with combustible gas with good stability and high reliability. Another purpose of the present invention is to provide a system for producing synthetic fuel by electrolysis of water coupled with combustible gas, which reduces energy consumption and avoids high-temperature cracking and carbon deposition of hydrocarbon fuels.

[0018] Technical solution: The solid oxide electrolysis stack for producing hydrogen by electrolyzing water coupled with combustible gas described in the present invention comprises an anode end plate, an intermediate plate assembly and a cathode end plate connected in sequence, wherein the intermediate plate assembly comprises a plurality of repeating units, and the repeating units are connected by a connecting plate; the repeating unit comprises an electrolytic cell, wherein the electrolytic cell comprises an anode, an electrolyte and a cathode, water vapor or a water vapor and hydrogen mixture is introduced into the cathode, and a water electrolysis reduction reaction occurs to obtain hydrogen, and a mixture of combustible gas, water vapor and / or carbon dioxide is introduced into the anode, and a deep oxidation reaction occurs between the combustible gas and oxygen ions generated by the electrolysis of water at the cathode and transmitted to the anode to obtain carbon dioxide.

[0019] Furthermore, the repeating unit also includes an anode seal, an anode current collector, a middle frame, a cathode current collector and a cathode seal, the anode seal and the electrolytic cell, the middle frame, the connecting plate or the anode end plate form an anode chamber, the anode current collector is arranged in the anode chamber, the cathode seal and the electrolytic cell, the middle frame, the connecting plate or the cathode end plate form a cathode chamber, the cathode current collector is arranged in the cathode chamber, and the anode chamber and the cathode chamber are isolated from each other.

[0020] Furthermore, the anode seal, the middle frame and the cathode seal are all hollow frames.

[0021] Furthermore, an anode raw gas inlet is arranged on one side of the cathode end plate and the middle plate assembly, and a cathode raw gas inlet is arranged on the other side; an anode product gas outlet is arranged on one side of the anode end plate and the middle plate assembly, and a cathode product gas outlet is arranged on the other side; the anode raw gas inlet is connected to the anode product gas outlet through the anode chamber, and the cathode raw gas inlet is connected to the cathode product gas outlet through the cathode chamber.

[0022] Furthermore, the anode current collector and the cathode current collector are both made of nickel foam, nickel felt, nickel mesh, copper foam, copper felt, copper mesh, stainless steel mesh, porous (La 1-x Sr x )TiO 3–δ or porous La 2-x Sr x Fe 2-y-z Ni y Mo z O 6-δ Made of high porosity and good electronic conductivity.

[0023] Furthermore, the anode end plate, the middle frame, the connecting plate and the cathode end plate are all made of 430L, 441, 446, Crofer, (La 1- x Sr x )TiO 3–δ or La 2-x Sr x Fe 2-y-z Ni y Mo z O 6-δ The thermal expansion coefficient is close to that of the electrolytic cell.

[0024] Furthermore, the surface of the connecting plate is covered with a conductive protective coating, which is composed of Ni, Fe, Co, FeNi3, (La 1-x Sr x )(Cr 1-y Fe y ) 3–δ , (La 1-x Sr x )(Cr1-y Mn y ) 3–δ , (La 1-x Sr x )TiO 3–δ or La 2-x Sr x Fe 2-y- z Ni y Mo z O 6-δ Made.

[0025] Further, the operating temperature of the solid oxide electrolytic stack is 300-1000°C, and the average operating voltage of the repeating unit is 0.1-2.0 V. Preferably, the operating temperature of the solid oxide electrolytic stack is 500-700°C, and the average operating voltage of the repeating unit is 0.3-1.3 V.

[0026] Furthermore, the combustible gas is one or more of methane, ethane, propane, methanol, ethanol, biomass gasification gas, hydrogen, and carbon monoxide.

[0027] Furthermore, the anode current collector is filled in the anode chamber, the top surface of the anode current collector is in close contact with the bottom surface of the anode end plate or the bottom surface of the connecting plate, and the bottom surface of the anode current collector is in close contact with the anode of the electrolytic cell; the cathode current collector is filled in the cathode chamber, the top surface of the cathode current collector is in close contact with the cathode of the electrolytic cell, and the bottom surface of the cathode current collector is in close contact with the top surface of the cathode end plate or the top surface of the connecting plate.

[0028] The system for synthesizing fuel by coupling water electrolysis with combustible gas described in the present invention comprises a raw material supply control module, a solid oxide electrolysis module, a process gas storage and pressurization module, a fuel synthesis module and a control module. The solid oxide electrolysis module comprises one or more of the above-mentioned solid oxide electrolysis stacks, ejectors, heat exchangers, heaters and condensers; the raw material supply control module is used to control the composition and flow rate of cathode raw gas composed of hydrogen and water vapor and anode raw gas composed of combustible gas, carbon dioxide and water vapor. The cathode raw gas and the anode raw gas enter the solid oxide electrolysis module and enter the solid after being fully preheated. The cathode product gas and the anode product gas are cooled and enter the hydrogen storage tank and the synthesis gas storage tank in the process gas storage and pressurization module respectively, and then enter the fuel synthesis module after being pressurized, and are converted into synthetic fuel in the synthetic fuel reactor. After cooling, gas-liquid separation and purification, the synthetic fuel is obtained; the synthetic fuel is one or more of methanol, ethanol, methane, ethane, propane, gasoline and diesel.

[0029] Working principle: Figure 1 As shown, water vapor or a mixture of water vapor and hydrogen mainly composed of water vapor is introduced into the cathode of the electrolytic cell, and a water electrolysis reduction reaction occurs, and the cathode product gas is condensed to obtain high-purity hydrogen; the anode of the electrolytic cell is introduced into a mixture of combustible gas (taking methane as an example), water vapor and / or carbon dioxide, and methane is deeply oxidized with oxygen ions generated by the electrolysis of water at the cathode and transmitted to the anode to generate water vapor and / or carbon dioxide, and the anode product gas is condensed to obtain self-enriched high-concentration carbon dioxide. .

[0030] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0031] 1. The cathode product gas is high-purity hydrogen or high-purity hydrogen can be obtained after condensation. The anode product gas is a mixture of water vapor and carbon dioxide or a mixture mainly composed of water vapor and carbon dioxide. After condensation, self-enriched high-concentration carbon dioxide can be obtained;

[0032] 2. Using combustible gas to consume oxygen ions produced by water electrolysis allows the electrolytic cell to operate at a lower operating voltage, thereby reducing the power consumption of hydrogen production by water electrolysis;

[0033] 3. Since the anode raw gas contains sufficient water vapor and / or carbon dioxide, and the combustible gases such as hydrocarbon fuels undergo deep oxidation reactions, high-temperature cracking and carbon deposition of hydrocarbon fuels can be effectively avoided, thereby enhancing the operating stability and reliability of the electrolytic stack. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a schematic diagram of the principle of the electrolytic cell 211 of the present invention;

[0035] Figure 2 is a schematic structural diagram of an electrolytic stack of the present invention;

[0036] Figure 3 It is a schematic diagram of the packaging structure of the repeating unit 21 of the present invention;

[0037] Figure 4 This is a physical picture of the electrolytic stack of Example 1 of the present invention;

[0038] Figure 5 is the current-voltage curve of the electrolytic stack of Example 1 of the present invention at 600° C.;

[0039] Figure 6 It is a schematic diagram of the structure of the system for synthesizing fuel by coupling electrolysis of water with combustible gas according to the present invention. DETAILED DESCRIPTION

[0040] Example 1

[0041] like Figure 2 The solid oxide electrolytic stack includes an anode terminal plate 1, an intermediate plate assembly 2 and a cathode terminal plate 3. The anode terminal plate 1 is the top surface of the electrolytic stack, the cathode terminal plate 3 is the bottom surface of the electrolytic stack, and the intermediate plate assembly 2 includes a plurality of repeating units 21, and each repeating unit 210 is connected by a connecting plate 22. The cathode terminal plate 3, the repeating unit 21 and the connecting plate 22 are each provided with at least one anode raw material gas inlet 6 on one side, and at least one cathode raw material gas inlet 7 on the other side. The anode terminal plate 1, the repeating unit 21 and the connecting plate 22 are each provided with at least one anode product gas outlet 8 on one side, and at least one cathode product gas outlet 9 on the other side. The anode raw material gas inlet 6 is connected to the anode product gas outlet 8 through the anode chamber 4, and the cathode raw material gas inlet 7 is connected to the cathode product gas outlet 9 through the cathode chamber 5.

[0042] The cathode raw gas 10 is water vapor or a mixture of water vapor and hydrogen, which enters the cathode chamber 5 of the electrolytic stack through the cathode raw gas inlet 7, undergoes a water electrolysis reduction reaction on the cathode 2113 of the electrolytic cell 211, generates a cathode product gas 12 consisting of hydrogen or mainly hydrogen, and leaves the electrolytic stack from the cathode product gas outlet 9. The anode raw gas 11 is a mixture of methane, water vapor, carbon dioxide, etc., which enters the anode chamber 4 of the electrolytic stack through the anode raw gas inlet 6, and undergoes a partial oxidation reaction with oxygen ions generated by the cathode water electrolysis reduction reaction and transmitted to the anode under the catalytic action of the anode 2111 of the electrolytic cell 211, generating an anode product gas 13 consisting of mainly carbon dioxide, and leaves the electrolytic stack from the anode product gas outlet 8.

[0043] The anode end plate 1, the middle frame 214, the connecting plate 22 and the cathode end plate 3 are high temperature alloy 446 with a thermal expansion coefficient close to that of the electrolytic cell 211. The surfaces of the anode end plate 1, the connecting plate 22 and the cathode end plate 3 are covered with a conductive protective coating FeNi3 alloy. The anode current collector 213 and the cathode current collector 215 are metal foam nickel with high porosity and good electronic conductivity. The anode seal 212 and the cathode seal 216 are high temperature sealing glass with high resistivity.

[0044] like Figure 3As shown, the repeating unit 21 includes an anode seal 212, an anode current collector 213, an electrolytic cell 211, a middle frame 214, a cathode current collector 215 and a cathode seal 216 which are packaged in sequence. Among them, the anode seal 212, the middle frame 214 and the cathode seal 216 are all hollow frames, and the anode seal 212, the anode seal 212, the electrolytic cell 211, the anode current collector 213, the cathode current collector 215 and the middle frame 214 are sealed on the connecting plate 22. The anode seal 212 is surrounded by the middle frame 214, the electrolytic cell 211, the connecting plate 22 or the anode end plate 1 to form an anode chamber 4, and the cathode seal 216 is surrounded by the middle frame 214, the electrolytic cell 211, the connecting plate 10 or the cathode end plate 3 to form a cathode chamber 5, and the anode chamber 4 and the cathode chamber 5 are isolated from each other. The anode current collector 213 is filled in the anode chamber 4, the top surface of the anode current collector 213 is in close contact with the bottom surface of the anode terminal plate 1 or the bottom surface of the connecting plate 22, and the bottom surface of the anode current collector 213 is in close contact with the anode 2111 of the electrolytic cell 211. The cathode current collector 215 is filled in the cathode chamber 5, the top surface of the cathode current collector 215 is in close contact with the cathode 2113 of the electrolytic cell 211, and the bottom surface of the cathode current collector 215 is in close contact with the top surface of the cathode terminal plate 2 or the top surface of the connecting plate 22.

[0045] like Figure 4 As shown, the solid oxide electrolysis stack includes 30 electrolysis cells 211 . Figure 5 This is the current-voltage curve of the electrolytic stack at 600°C. The electrolysis voltage at 60A is 13V, and the hydrogen production rate is 0.75Nm 3 / h, the corresponding power consumption for hydrogen production is 1.04kWh / Nm 3 H2 or 11.65kWh / kg H2. The electrolysis voltage of the electrolytic stack at 40A is 8.34V, and the hydrogen production rate is 0.50Nm 3 / h, the corresponding power consumption for hydrogen production is 0.67kWh / Nm 3 H2 or 7.47kWh / kg H2. It can be seen that the actual power consumption of hydrogen production by the electrolytic stack is much lower than the power consumption of hydrogen production by the current traditional water electrolysis technology (37.5-54kWh / kg H2).

[0046] Example 2

[0047] The system for synthesizing fuel by coupling water electrolysis with combustible gas comprises a raw material supply control module, a solid oxide electrolysis module, a process gas storage and pressurization module, a fuel synthesis module, and a control module, etc. The solid oxide electrolysis module includes but is not limited to one or more solid oxide electrolysis stacks, ejectors, heat exchangers, heaters, condensers, etc. described in Example 1, and the fuel synthesis module includes but is not limited to synthetic fuel reactors, heat exchangers, gas-liquid separators, circulating gas compressors, synthetic fuel purification units, etc. The raw material supply control module is used to control the composition and flow of cathode raw gas composed of hydrogen and water vapor and anode raw gas 11 composed of combustible gas, carbon dioxide, and water vapor. The cathode raw gas 12 and the anode raw gas 11 enter the solid oxide electrolysis module, enter the solid oxide electrolysis stack 200 after being fully preheated, and are synchronously and respectively converted into cathode product gas 12 with hydrogen as the main component and water vapor as the secondary component and anode product gas 13 with carbon monoxide, carbon dioxide, and water vapor as the main components and hydrogen as the secondary component. The cathode product gas 12 and the anode product gas 13 generated by the solid oxide electrolysis module enter the hydrogen storage tank and the synthesis gas storage tank respectively and enter the synthetic fuel module through the compressor B and the compressor A respectively, thereby generating synthetic fuel.

Claims

1. A solid oxide electrolysis stack for producing hydrogen by electrolyzing water coupled with combustible gas, characterized in that: The invention comprises an anode terminal plate (1), an intermediate plate assembly (2) and a cathode terminal plate (3) connected in sequence, wherein the intermediate plate assembly (2) comprises a plurality of repeating units (21), and the repeating units (21) are connected via a connecting plate (22); the repeating unit (21) comprises an electrolytic cell (211), and the electrolytic cell (211) comprises an anode (2111), an electrolyte (2112) and a cathode (2113); water vapor or a water vapor and hydrogen mixture is introduced into the cathode (2113) to generate a water electrolysis reduction reaction to obtain hydrogen; a mixture of combustible gas, water vapor and / or carbon dioxide is introduced into the anode (2111), and the combustible gas and oxygen ions generated by the electrolysis of water by the cathode (2113) and transmitted to the anode (2111) undergo a deep oxidation reaction to obtain carbon dioxide.

2. A solid oxide electrolysis stack for producing hydrogen by electrolysis of water coupled with combustible gas according to claim 1, characterized in that: The repeating unit (21) further comprises an anode seal (212), an anode current collector (213), a middle frame (214), a cathode current collector (215) and a cathode seal (216); the anode seal (212) and the electrolytic cell (211), the middle frame (214), the connecting plate (22) or the anode end plate (1) form an anode chamber (4); the anode current collector (213) is arranged in the anode chamber (4); the cathode seal (216) and the electrolytic cell (211), the middle frame (214), the connecting plate (22) or the cathode end plate (3) form a cathode chamber (5); the cathode current collector (215) is arranged in the cathode chamber (5); and the anode chamber (4) and the cathode chamber (5) are isolated from each other.

3. The solid oxide electrolysis stack for producing hydrogen by electrolysis of water coupled with combustible gas according to claim 2, characterized in that: The anode seal (212), the middle frame (214) and the cathode seal (216) are all hollow frames.

4. The solid oxide electrolysis stack for producing hydrogen by electrolysis of water coupled with deep oxidation of combustible gas according to claim 2, characterized in that: An anode raw gas inlet (6) is provided on one side of the cathode end plate (3) and the intermediate plate assembly (2), and a cathode raw gas inlet (7) is provided on the other side; an anode product gas outlet (8) is provided on one side of the anode end plate (3) and the intermediate plate assembly (2), and a cathode product gas outlet (9) is provided on the other side; the anode raw gas inlet (6) is connected to the anode product gas outlet (8) through the anode chamber (4), and the cathode raw gas inlet (7) is connected to the cathode product gas outlet (9) through the cathode chamber (5).

5. The solid oxide electrolysis stack for producing hydrogen by electrolysis of water coupled with combustible gas according to claim 2, characterized in that: The anode current collector (213) and the cathode current collector (215) are both made of foam nickel, nickel felt, nickel mesh, foam copper, copper felt, copper mesh, stainless steel mesh, porous (La 1-x Sr x )TiO 3–δ or porous La 2-x Sr x Fe 2-y-z Ni y Mo z O 6-δ Made.

6. The solid oxide electrolysis stack for producing hydrogen by electrolysis of water coupled with combustible gas according to claim 2, characterized in that: The anode end plate (3), the middle frame (214), the connecting plate (22) and the cathode end plate (3) are all made of 430L, 441, 446, Crofer, (La 1-x Sr x )TiO 3–δ or La 2-x Sr x Fe 2-y-z Ni y Mo z O 6-δ Made.

7. The solid oxide electrolysis stack for producing hydrogen by electrolysis of water coupled with combustible gas according to claim 1, characterized in that: The surface of the connecting plate (22) is covered with a conductive protective coating, wherein the conductive protective coating is composed of Ni, Fe, Co, FeNi3, (La 1-x Sr x )(Cr 1-y Fe y ) 3–δ , (La 1-x Sr x )(Cr 1-y Mn y ) 3–δ , (La 1-x Sr x )TiO 3–δ or La 2-x Sr x Fe 2-y- z Ni y Mo z O 6-δ Made.

8. The solid oxide electrolysis stack for producing hydrogen by electrolysis of water coupled with combustible gas according to claim 1, characterized in that: Its operating temperature is 300-1000° C., and the average operating voltage of the repeating unit (21) is 0.1-2.0V.

9. The solid oxide electrolysis stack for producing hydrogen by electrolysis of water coupled with combustible gas according to claim 1, characterized in that: The combustible gas is one or more of methane, ethane, propane, methanol, ethanol, biomass gasification gas, hydrogen, and carbon monoxide.

10. A system for synthesizing fuel by electrolyzing water and coupling combustible gas, characterized in that: The invention comprises a raw material supply control module, a solid oxide electrolysis module, a process gas storage and pressurization module, a fuel synthesis module and a control module, wherein the solid oxide electrolysis module comprises one or more solid oxide electrolysis stacks, ejectors, heat exchangers, heaters and condensers as described in any one of claims 1 to 9; the raw material supply control module is used to control the composition and flow of cathode raw gas (10) composed of hydrogen and water vapor and anode raw gas (11) composed of combustible gas, carbon dioxide and water vapor, wherein the cathode raw gas (10) and the anode raw gas (11) enter the solid oxide electrolysis module and enter the solid oxide electrolysis stack after being fully preheated, and ... preheated, and the cathode raw gas (10) and the anode raw gas (11) enter the solid oxide electrolysis module and enter the solid oxide electrolysis stack after being preheated, and the cathode raw gas (10) and the anode The cathode product gas (12) and the anode product gas (13) are respectively converted into a cathode product gas (12) with hydrogen as the main component and water vapor as the secondary component and an anode product gas (13) with carbon monoxide, carbon dioxide and water vapor as the main components and hydrogen as the secondary component. After cooling, the cathode product gas (12) and the anode product gas (13) enter the hydrogen storage tank and the synthesis gas storage tank in the process gas storage and pressurization module respectively, and then enter the fuel synthesis module after being pressurized, and are converted into synthetic fuel in the synthetic fuel reactor. After cooling, gas-liquid separation and purification, synthetic fuel is obtained; the synthetic fuel is one or more of methanol, ethanol, methane, ethane, propane, gasoline and diesel.

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