SOEC system utilizing air electrode gas heat

Abstract

The present invention relates to the field of water electrolysis hydrogen production, and discloses an SOEC system using air electrode gas heat, the system comprises a water vapor generation device, an SOEC system, and a hydrogen separation device for separating hydrogen from a fuel electrode side product of the SOEC system, the air electrode tail gas of the SOEC system is used for preheating raw material air used in the SOEC system, and the raw material air is used for preheating raw material air used in the SOEC system. The steam generating device comprises a steam generator, a tail gas channel in the steam generator is located below the liquid level in the working state, a steam outlet of the steam generator is connected with a raw material mixing device, and a hydrogen inlet is formed in the raw material mixing device. The molar ratio of the water vapor to the hydrogen mixture in the raw material mixing device is not less than 50%, and the mixture is introduced into a fuel electrode of the SOEC system through a raw material outlet. By reasonably controlling the gas flow rate of the air side and controlling the mixing ratio of the water vapor and the hydrogen, the energy is saved while the stable hydrogen output rate is kept.

Description

Technical Field

[0001] This invention relates to an energy-saving SOEC system. Background Technology

[0002] The widespread use of limited fossil fuels has caused environmental problems. From both economic and ecological perspectives, clean and renewable energy sources such as wind and solar power should be promoted. However, due to intermittency and location limitations, renewable energy should be stored in more stable carriers. Hydrogen is considered a promising energy carrier and a future environmentally friendly fuel. Solid oxide electrolyzer cells (SOECs) can produce hydrogen through steam cracking, representing a promising and efficient method for large-scale hydrogen production.

[0003] In current SOEC high-temperature water electrolysis for hydrogen production, the handling of the exhaust gas at the air electrode is a challenging issue. During electrolysis, H2O is continuously electrolyzed into H2 and O2, with a molar ratio of 2:1. Oxygen is constantly generated on the air electrode side of the SOEC system, and this generated oxygen must be continuously removed; otherwise, the reaction rate on this side will decrease. To maintain the oxygen partial pressure in the air, fresh air needs to be continuously introduced. However, the continuous introduction of fresh gas necessitates constant heating, consuming more heat and leading to decreased system thermal efficiency and increased electrolysis energy consumption. Therefore, it is crucial to rationally handle the exhaust gas generated on the air electrode side and effectively utilize its high-temperature value.

[0004] Meanwhile, the introduction of water vapor during electrolysis is a heat-intensive process. The enthalpy of water vaporization means that the formation of water vapor requires a large amount of heat, and the heat generated solely from hydrogen production is insufficient to meet the conditions for water vapor formation and production. On the air electrode side, the total amount of oxygen increases, and the total enthalpy of the exhaust gas also increases. Therefore, optimization of the existing SOEC high-temperature water electrolysis hydrogen production system is considered to reduce overall energy consumption.

[0005] Furthermore, in SOFC devices, the gas on the air electrode side typically needs to remove heat from the SOEC system under high current conditions, and excessive air is usually introduced into the SOEC system to increase the reaction rate. However, in the control strategy of the SOEC system, in order to improve electrolysis efficiency and reduce energy consumption in the electrolysis process, a more reasonable control of the gas flow rate on the air side is considered to ensure that the gas reaction rate is matched with the energy consumption control target. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an SOEC system that utilizes the heat of the air electrode gas. This system can use the heat of the exhaust gas from the air electrode to complete the vaporization of liquid water or preheat the air, thereby reducing the overall energy consumption of the system and achieving the goal of overall energy saving.

[0007] The technical solution adopted by this invention to solve its technical problem is: an SOEC system utilizing the heat of air-electrode gas, the SOEC system including a steam generator and an SOEC system, and a hydrogen separation device for separating hydrogen from the fuel-electrode side products of the SOEC system. The SOEC system utilizes the exhaust gas from the air-electrode tail gas to preheat the feed air used in the SOEC system, or utilizes the exhaust gas from the air-electrode tail gas of the SOEC system to exchange heat with liquid water in the steam generator. The steam generator includes a steam generator equipped with a liquid water supply pipe. In operation, the exhaust gas channel within the steam generator is located below the liquid surface. The steam outlet of the steam generator is connected to a feed mixing device, which has a hydrogen inlet. The steam and hydrogen mixture in the feed mixing device has a molar ratio of not less than 50% for the steam. The mixture is introduced into the fuel electrode of the SOEC system through the feed outlet.

[0008] Furthermore, to ensure the gas reaction rate and control energy consumption, the air intake rate of the air electrode is 2 to 10 times that of the oxygen generation rate of the air electrode.

[0009] Furthermore, taking the hydrogen inlet rate P of the raw material mixing device as the standard, the corresponding air inlet rate, oxygen generation rate, and fuel inlet rate are controlled according to the following ratios: the air inlet rate of the air electrode ranges from 0.667P to 3.33P, the oxygen generation rate ranges from 0.333P to 0.667P, the fuel inlet rate ranges from 0.333P to 1P, all in mol / s, and the hydrogen inlet rate P = 5 to 10 mol / s. This enables the system to operate stably with high electrolysis efficiency and makes comprehensive use of the heat in the system.

[0010] Furthermore, the hydrogen in the hydrogen inlet originates from the pipeline between the fuel polar-side product outlet of the SOEC system and the hydrogen separation unit.

[0011] Furthermore, in the raw material mixing device, the water vapor and hydrogen mixture has a molar ratio of 70-80% water vapor and 20-30% H2, which can maintain a high electrolysis efficiency.

[0012] In addition, the hydrogen separation device includes a cooling device and a drying device connected to each other. The fuel polar product enters the hot end inlet of the cooling device, and the fuel polar product at the cold end outlet of the cooling device is connected to the inlet of the drying device through a pipe. The drying device uses calcium oxide or concentrated sulfuric acid as a desiccant.

[0013] The core contributions of this invention to the prior art are twofold: first, it points out the crucial role of strictly controlling the gas flow rate on the air side in ensuring the gas reaction rate and controlling energy consumption; second, it indicates that the control of air flow rate needs to be calibrated based on electrolysis current, SOEC system temperature range control, and power consumption control to ensure high electrolysis efficiency while reasonably controlling the ratio of air to fuel gas water vapor content and maintaining the core temperature of the electrolyzer.

[0014] The beneficial effects of this invention are: it makes full use of the heat contained in the exhaust gas of the air electrode, which can effectively save energy; and the heat of the fuel electrode products can also be fully utilized, reducing the difficulty of cooling and separating the products; the structure is simple and easy to implement; by reasonably controlling the gas flow rate on the air side and controlling the mixing ratio of water vapor and hydrogen, energy is saved while maintaining a stable hydrogen production rate. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the exhaust gas heat recycling device of Embodiments 1 and 2 of the present invention.

[0016] Figure 2 yes Figure 1 A schematic diagram of the cross-sectional shape of one of the shell structures that can be used in the device shown.

[0017] Figure 3 This is a schematic diagram of the steam generator and the raw material mixing device in this invention.

[0018] Figure 4 This is a schematic diagram of the hydrogen separation device used in Embodiments 1 and 2 of the present invention.

[0019] The markings in the diagram are as follows: 1-Inlet, 2-Outlet, 3-Tail gas inlet, 4-Tail gas outlet, 5-Flow channel, 6-Liquid water supply pipe, 7-Hydrogen inlet, 8-Raw material outlet, 9-Tail gas flow channel, 10-Flow channel inlet end, 11-Steam generator, 12-Raw material mixing device, 13-Mixed gas inlet, 14-Coolant outlet, 15-Coolant inlet, 16-Hydrogen outlet, 17-Drying device, 18-Cooling device, 19-Connecting pipe. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] refer to Figures 1-4This invention discloses a SOEC system utilizing the heat of air-electrode gas. The SOEC system includes a steam generator and an SOEC system, as well as a hydrogen separation device for separating hydrogen from the fuel-electrode products of the SOEC system. The air-electrode exhaust gas of the SOEC system exchanges heat with liquid water in the steam generator. The steam generator includes a steam generator 11 with a liquid water supply pipe 6. In operation, the exhaust gas channel within the steam generator 11 is below the liquid surface. The steam outlet of the steam generator 11 is connected to a raw material mixing device 12, which has a hydrogen inlet 7. In the raw material mixing device 12, the steam and hydrogen mixture has a molar ratio of not less than 50% for steam. The mixture is introduced into the fuel electrode of the SOEC system through the raw material outlet 8. The steam generator can utilize the waste heat of the air-electrode exhaust gas for water vaporization. The heat contained in the exhaust gas (air + O2) is recycled. The heat recycling device includes an exhaust gas inlet 3, an exhaust gas outlet 4, an inlet 1 for introducing gas, and an outlet 2 for extracting gas. The inlet and outlet can be located on either side of the recycling system and their positions can be randomly distributed. The gas flow channel 5 can be arranged in an S-shape or other shapes in the heat recycling device to achieve a sufficiently large contact area and a heat balance without excessive heat loss during heat exchange.

[0022] All pipes in the heat recycling device can be made of GH3030 nickel alloy high-temperature resistant steel or other high-temperature resistant steel. Pipes exposed to the external environment should be covered with insulation material, while pipes inside the heat recycling device may not be covered with insulation material to achieve good thermal conductivity.

[0023] refer to Figure 3 The exhaust gas channel 9 for heat recycling in the steam generator can also be laid out in an S-shape or other shapes, and sufficient heat exchange occurs below the water surface. When the liquid water in the steam generator 11 is insufficient, it can be supplemented through the liquid water replenishment pipe 6. The steam generated in the steam generator enters the raw material mixing device 12 through the flow channel to mix with hydrogen and be preheated, and finally enters the SOEC system cathode through the outlet gas channel.

[0024] refer to Figure 4The hydrogen separation device used in the SOEC system utilizing air-to-gas heat of the present invention includes a cooling device 18 and a drying device 17 connected to each other. The fuel-to-gas product enters the hot end inlet of the cooling device 18, and the cold end outlet of the cooling device 18 is connected to the inlet of the drying device 17 via a connecting pipe 19. The drying device 17 uses calcium oxide or concentrated sulfuric acid as a desiccant. The cooling device 18 can be a condenser or other gas cooling equipment, mainly used to condense water vapor. The coolant used in the cooling device 18 can be liquid water.

[0025] refer to Figure 1 and Figure 2 The SOEC system utilizing the heat of air electrode gas operates as follows: First, the air to be introduced enters the heat recycling device through the gas inlet 1. Then, the produced exhaust gas flows into the device through the exhaust gas inlet 3, preheating the air in the flow channel 5. The exhaust gas flows out through the exhaust gas outlet 4, and the hot air flows out through the outlet 2. Then, it enters the subsequent heating device for further heating. The heat provided by the subsequent heating device per unit time is adjustable so that the temperature of the air entering the air electrode does not adversely affect the electrolysis efficiency.

[0026] refer to Figure 3 The operation process of the steam generator is as follows: First, the exhaust gas from the air electrode enters the steam generator 11 from the inlet 10 of the flow channel. This flow channel is below the liquid surface in the steam generator 11, and uses heat to heat the water to generate steam. The cooled exhaust gas is discharged from the exhaust flow channel 9, and the generated steam enters the raw material mixing device 12 from the upper flow channel of the steam generator. Then, hydrogen flows into the raw material mixing device 12 from the hydrogen inlet 7, where it is mixed in proportion and flows into the SOEC system fuel electrode from the raw material outlet 8 for electrolysis. When the liquid water in the steam generator 11 is insufficient, it is replenished through the liquid water replenishment pipe 6. By controlling the air flow rate, it is possible to prevent the air velocity from being too low, causing heat accumulation in the electrolyzer and preventing the utilization of heat, which would lead to an increase in the core temperature of the electrolyzer. On the other hand, it is also necessary to prevent the air velocity from being too high, causing the core temperature of the SOEC system to drop. Therefore, by combining the adjustment of the air velocity with the heat input of the subsequent heating device, the core temperature of the SOEC system can be kept stable.

[0027] refer to Figure 4The operation process of the hydrogen separation unit is as follows: A small portion of the product generated at the fuel electrode can be diverted to the raw material mixing device 12, mixed with water vapor, and then flowed back to the fuel electrode. Most of the product generated at the fuel electrode flows into the cooling device 18 from the mixed gas inlet 13. At the same time, coolant flows in from the lower coolant inlet 15 and flows out from the coolant outlet 14 to cool the product. The cooled product is water-containing hydrogen. The cooled product flows into the drying device 17 through the pipe 19. After being dried by the desiccant, it flows out from the hydrogen outlet 16 and is stored. The tail gas generated at the air electrode enters the steam generator or the preheating device.

[0028] This invention, from a cost-reduction perspective, employs a heat recycling device to reuse the heat from the exhaust gas. It offers advantages such as simple equipment, controllable process, low cost, and suitability for large-scale production. The above technical solution addresses the problems of exhaust gas treatment in SOEC air electrodes and the source of heat for water vaporization. This method is simple and effective, fully utilizing waste heat to heat the intake gas, reducing energy consumption for hydrogen production through water electrolysis, thereby lowering costs and improving economic efficiency. This SOEC system has the following advantages: (1) This invention uses common industrial equipment and utilizes the enthalpy generated by the air electrode, which is an effective energy-saving system; (2) This invention makes full use of the heat of the fuel electrode products, reducing the difficulty of cooling and separating the products; (3) The system designed in this invention has the characteristics of energy saving, strong operability and simple equipment.

[0029] According to the inventor's experiments, the air intake rate in the SOEC system is controlled within the range of 10–50 mol / s, the fuel intake rate is controlled within the range of 5–20 mol / s, the hydrogen intake rate in the raw material mixing device is controlled within the range of 5–10 mol / s, the hydrogen intake rate is adjusted according to the fuel intake rate and the mixing ratio of water vapor and hydrogen, and the oxygen generation rate is controlled within the range of 5–10 mol / s, which should be less than the air intake rate.

[0030] Example 1: like Figures 1-4 As shown in the SOEC system utilizing the heat of the air electrode gas, the exhaust gas from the air electrode is a mixture of air and oxygen produced by electrolysis. Assuming the core temperature of the SOEC electrolyzer is 700°C, and the enthalpy is entirely provided by the oxygen produced by electrolysis, the mixture of water vapor and hydrogen in the raw material mixing unit contains 80% water vapor and 20% H2 by molar ratio.

[0031] The specific heat capacity of oxygen is C1 = 0.918 J / (g ℃), or C1 = 29.376 J / (mol ℃).

[0032] The specific heat capacity of air is C2 = 1 J / (g ℃), which is C2 = 29 J / (mol ℃).

[0033] The air inlet velocity of the SOEC system is controlled using a gas mass flow meter. For example, if the air inlet velocity v = 10 mol / s, the exhaust gas inlet velocity of exhaust duct 9 is equal to the air inlet velocity of the SOEC system, and the fuel inlet velocity v2 = 12 mol / s. Exhaust duct 9 is laid out in a serpentine pattern below the working liquid level in the steam generator. The exhaust duct 9 is made of high-temperature resistant stainless steel and uses a circular tube. The outer wall of the duct is in direct contact with the liquid water to be heated for heat exchange, with a heat exchange efficiency η = 90%. The residence time of the exhaust gas in the steam generator 11 must not be less than 30 seconds.

[0034] The control gas ratio on the fuel electrode side is 80% H₂O + 20% H₂. The measured fuel electrode side products are 4% H₂O + 96% H₂. The calculated battery electrolysis efficiency η₁ = 95%. The rate of oxygen generation on the air electrode side is v₁ = 4.56 mol / s. In the heat recycling device, the exhaust gas temperature at exhaust gas inlet 3 is T₁ = 700℃, and the exhaust gas temperature at exhaust gas outlet 4 is T₂ = 100℃. Therefore, the effective heat exchange energy generated by the exhaust gas in the heat recycling device is Q = C₁ * v₁ * (T₁ - T₂) = 80.4 KJ / s. Calculations show that the temperature of the air to be introduced can be increased by ΔT1=Q*η / (v* C2)=249.4℃, which can save a lot of the heat required for heating the intake air and improve the energy utilization efficiency of the entire system.

[0035] The fuel product first passes through cooling device 18 to condense water vapor. Since the initial water vapor content is relatively high, a significant portion of the water still needs to be removed, which can be achieved using concentrated sulfuric acid or similar methods for drying. The hydrogen gas discharged from drying device 17 is stored in a hydrogen storage tank.

[0036] Example 2: The apparatus in this embodiment is the same as in Embodiment 1. The air electrode exhaust gas is a mixture of air and oxygen produced by electrolysis. It is assumed that the core temperature of the SOEC system electrolyzer is 700℃, and the enthalpy is entirely provided by the oxygen produced by electrolysis. The specific heat capacity of liquid water is C3 = 4.2 J / (g℃), i.e., C3 = 75.6 J / (mol℃), and the enthalpy of vaporization of water at 100℃ is ΔH = 40.63 KJ / mol. The gas mass flow meter is used to control the fuel electrode inlet velocity of the SOEC system to v2 = 15 mol / s, and the air electrode inlet velocity to 10 mol / s.

[0037] The molar ratio of the feed gas on the fuel electrode side is controlled at 70% H2O + 30% H2, the battery electrolysis efficiency η2 = 98%, and the heat exchange efficiency of all heat pipes η = 90%. Calculations show that the water vapor inlet velocity on the fuel electrode side is 10.5 mol / s, and the hydrogen inlet velocity is 4.5 mol / s. Therefore, the hydrogen inlet velocity in the mixing device must not be lower than 4.5 mol / s. The product on the fuel electrode side is 1.4% H2O + 98.6% H2, and the oxygen generation rate on the air electrode side is v3 = 5.145 mol / s.

[0038] The air and exhaust gas introduced into the steam generator have an inlet temperature of T1=700℃ and an outlet temperature of T2=100℃. The effective heat exchange energy that the exhaust gas can generate in the device is Q1= C1* v3*(T1- T2)*η=81.6 KJ / second. The residence time of the exhaust gas in the steam generator 11 shall not be less than 30s, so Q2=Q1*t≥2448KJ.

[0039] Calculations show that the water vapor evaporation rate must not be lower than v4 = 10.5 mol / s. The heat required per second for water to evaporate from room temperature (assuming room temperature is 25℃) is Q3 = [C3 * (100℃ - room temperature) + ΔH] * v4 * 1 = 486.15 KJ. Since Q2 > Q3, the heat exchanged by the exhaust gas through the heat exchanger is sufficient to evaporate the water and raise the temperature to a certain extent.

[0040] At this point, the gas still retains some preheated heat, which can be used to heat the air. Calculations show that the air can be heated to 350°C within 10 seconds.

[0041] Based on the calculations in the previous step, after liquid water evaporates into gaseous water vapor, its temperature in the subsequent heat exchanger can be further increased to 450℃, reaching the temperature requirement for entering the SOEC system. This step can save a lot of heating energy and further reduce the power consumption required for SOEC water electrolysis to produce hydrogen.

[0042] The fuel-derived products first pass through cooling device 18 to condense water vapor. Since most of the water has been converted into hydrogen, only a small portion of the water needs to be removed, which can be done using calcium sulfate, a solid desiccant. The hydrogen discharged from drying device 17 is stored in a hydrogen storage tank.

[0043] Example 3: The apparatus in this embodiment is the same as in Embodiment 1. The air electrode exhaust gas is a mixture of air and oxygen produced by electrolysis. It is assumed that the core temperature of the SOEC system electrolyzer is 700℃, and the enthalpy is entirely provided by the oxygen produced by electrolysis. The specific heat capacity of liquid water is C3 = 4.2 J / (g ℃), i.e., C3 = 75.6 J / (mol ℃), and the enthalpy of vaporization of water at 100℃ is ΔH = 40.63 KJ / mol. The gas mass flow meter controls the fuel electrode inlet velocity of the SOEC system to v5 = 20 mol / s, and the air electrode inlet velocity to be 20 mol / s.

[0044] The molar ratio of the feed gas on the fuel electrode side is controlled at 50% H₂O + 50% H₂, the battery electrolysis efficiency η₃ = 80%, and the heat exchange efficiency of all heat pipes η = 90%. Calculations show that the steam inlet velocity on the fuel electrode side is 10 mol / s, the hydrogen inlet velocity is 10 mol / s, and the hydrogen inlet velocity in the mixing device must not be lower than 10 mol / s. The product on the fuel electrode side is 10% H₂O + 90% H₂, and the oxygen generation rate on the air electrode side is v₆ = 4 mol / s.

[0045] The air and exhaust gas introduced into the steam generator have an inlet temperature of T1=700℃ and an outlet temperature of T2=100℃. The effective heat exchange energy that the exhaust gas can generate in the device is Q4= C1* v6*(T1- T2)*η=70.5 KJ / second. The residence time of the exhaust gas in the steam generator 11 shall not be less than 30s, so Q5=Q4*t≥2115KJ.

[0046] Calculations show that the evaporation rate of water vapor must not be less than v7 = 10 mol / s. The heat required for water to evaporate from room temperature (25℃) per second is Q6 = [C3 * (100℃ - room temperature) + ΔH] * v7 * 1 = 463 KJ. Since Q5 > Q6, the heat exchanged by the exhaust gas through the heat exchanger is sufficient to evaporate the water and raise the temperature to a certain extent.

[0047] At this point, the gas still retains some preheated heat, which can be used to heat the air. Calculations show that the air can be heated to 320°C within 10 seconds.

[0048] Based on the calculations in the previous step, after liquid water evaporates into gaseous water vapor, its temperature in the subsequent heat exchanger can be further increased to 380℃. Although further heating is still required to reach the temperature requirement for entering the SOEC system, a large amount of heating energy can be saved, further reducing the power consumption required for SOEC water electrolysis to produce hydrogen.

[0049] The fuel-derived products first pass through cooling device 18 to condense water vapor. Since most of the water has been converted into hydrogen, only a small portion of the water needs to be removed, which can be done using calcium sulfate, a solid desiccant. The hydrogen discharged from drying device 17 is stored in a hydrogen storage tank.

[0050] Example 4: The apparatus in this embodiment is the same as in Embodiment 1. The air electrode exhaust gas is a mixture of air and oxygen produced by electrolysis. It is assumed that the core temperature of the SOEC system electrolyzer is 700℃, and the enthalpy is entirely provided by the oxygen produced by electrolysis. The specific heat capacity of liquid water is C3 = 4.2 J / (g℃), i.e., C3 = 75.6 J / (mol℃), and the enthalpy of vaporization of water at 100℃ is ΔH = 40.63 KJ / mol. The gas mass flow meter controls the fuel electrode inlet velocity of the SOEC system to v8 = 10 mol / s, and the air electrode inlet velocity to 10 mol / s.

[0051] The molar ratio of the feed gas on the fuel electrode side is controlled at 90% H₂O + 10% H₂, the battery electrolysis efficiency η₄ = 85%, and the heat exchange efficiency of all heat pipes η = 90%. Calculations show that the steam inlet velocity on the fuel electrode side is 9 mol / s, and the hydrogen inlet velocity is 1 mol / s. Therefore, the hydrogen inlet velocity in the mixing device must not be less than 1 mol / s. The product on the fuel electrode side is 13.5% H₂O + 86.5% H₂, and the oxygen generation rate on the air electrode side is v₉ = 3.825 mol / s.

[0052] The air and exhaust gas introduced into the steam generator have an inlet temperature of T1=700℃ and an outlet temperature of T2=100℃. The effective heat exchange energy that the exhaust gas can generate in the device is Q7= C1* v9*(T1- T2)*η=60.7 KJ / second. The residence time of the exhaust gas in the steam generator 11 shall not be less than 30s, so Q8=Q7*t≥1821KJ.

[0053] Calculations show that the evaporation rate of water vapor must not be less than v10 = 9 mol / s. The heat required per second for water to evaporate from room temperature (25℃) is Q9 = [C3 * (100℃ - room temperature) + ΔH] * v10 * 1 = 416.7 KJ. Since Q8 > Q9, the heat exchanged by the exhaust gas through the heat exchanger is sufficient to evaporate the water and raise the temperature to a certain extent.

[0054] At this point, the gas still retains some preheat, which can be used to heat the air. Calculations show that the air can be heated to 300°C within 10 seconds.

[0055] Based on the calculations in the previous step, after the liquid water evaporates into gaseous water vapor, its temperature in the subsequent heat exchanger can be further increased to 450℃, reaching the temperature requirement for entering the SOEC system. This can save a lot of heating energy and further reduce the power consumption required for SOEC water electrolysis to produce hydrogen.

[0056] The fuel-derived products first pass through cooling device 18 to condense water vapor. Since most of the water has been converted into hydrogen, only a small portion of the water needs to be removed, which can be done using calcium sulfate, a solid desiccant. The hydrogen discharged from drying device 17 is stored in a hydrogen storage tank.

[0057] Example 5: The apparatus in this embodiment is the same as in Embodiment 1. The air electrode exhaust gas is a mixture of air and oxygen produced by electrolysis. It is assumed that the core temperature of the SOEC system electrolyzer is 700℃, and the enthalpy is entirely provided by the oxygen produced by electrolysis. The specific heat capacity of liquid water is C3 = 4.2 J / (g℃), i.e., C3 = 75.6 J / (mol℃), and the enthalpy of vaporization of water at 100℃ is ΔH = 40.63 KJ / mol. The gas mass flow meter controls the fuel electrode inlet velocity of the SOEC system to be v11 = 20 mol / s, and the air electrode inlet velocity to be 50 mol / s.

[0058] The molar ratio of the feed gas on the fuel electrode side is controlled at 60% H₂O + 40% H₂, the battery electrolysis efficiency η₅ = 70%, and the heat exchange efficiency of all heat pipes η = 90%. Calculations show that the steam inlet velocity on the fuel electrode side is 12 mol / s, and the hydrogen inlet velocity is 8 mol / s. Therefore, the hydrogen inlet velocity in the mixing device must not be lower than 8 mol / s. The product on the fuel electrode side is 18% H₂O + 82% H₂, and the oxygen generation rate on the air electrode side is v₁₂ = 4.2 mol / s.

[0059] The air and exhaust gas introduced into the steam generator have an inlet temperature of T1=700℃ and an outlet temperature of T2=100℃. The effective heat exchange energy that the exhaust gas can generate in the device is Q10= C1* v12*(T1- T2)*η=66.6KJ / second. The residence time of the exhaust gas in the steam generator 11 shall not be less than t=30s. Therefore, Q11=Q10*t≥1998KJ.

[0060] Calculations show that the water vapor evaporation rate must not be less than v13 = 12 mol / s. The heat required for water to evaporate from room temperature per second is Q12 = [C3 * (100℃ - room temperature) + ΔH] * v13 * 1 = 555.6 KJ. Since Q11 > Q12, the heat exchanged by the exhaust gas through the heat exchanger is sufficient to evaporate the water and raise the temperature to a certain extent.

[0061] At this point, the gas still retains some preheated heat, which can be used to heat the air. Calculations show that the air can be heated to 200°C within 10 seconds.

[0062] Based on the calculations in the previous step, after the liquid water evaporates into gaseous water vapor, its temperature in the subsequent heat exchanger can be further increased to 450℃, reaching the temperature requirement for entering the SOEC system. This can save a lot of heating energy and further reduce the power consumption required for SOEC water electrolysis to produce hydrogen.

[0063] The fuel-derived products first pass through cooling device 18 to condense water vapor. Since most of the water has been converted into hydrogen, only a small portion of the water needs to be removed, which can be done using calcium sulfate, a solid desiccant. The hydrogen discharged from drying device 17 is stored in a hydrogen storage tank.

Claims

1. A SOEC system utilizing the heat of an air-polar gas, the SOEC system comprising a steam generator and an SOEC system, and a hydrogen separation device for separating hydrogen from the fuel-polar products of the SOEC system, characterized in that: The air electrode tail gas of the SOEC system is used to preheat the raw material air used in SOEC, or the air electrode tail gas of the SOEC system is used to exchange heat with liquid water in a steam generator. The steam generator includes a steam generator (11) with a liquid water supply pipe (6). In the working state, the tail gas channel in the steam generator (11) is located below the liquid surface. The steam outlet of the steam generator (11) is connected to the raw material mixing device (12). The raw material mixing device (12) is provided with a hydrogen inlet (7). The steam and hydrogen mixture in the raw material mixing device (12) has a molar ratio of not less than 50% for steam. The mixture is introduced into the fuel electrode of the SOEC system through the raw material outlet (8).

2. The SOEC system utilizing the heat of air-polarized gas as described in claim 1, characterized in that: The air intake rate at the air pole is 2 to 10 times the oxygen generation rate at the air pole.

3. The SOEC system utilizing the heat of air-polarized gas as described in claim 2, characterized in that: [The system is designed to...] Using the hydrogen inlet rate P of the raw material mixing device (12) as the standard, the air inlet rate, oxygen generation rate and fuel inlet rate of the corresponding air pole are controlled according to the following ratios: the air inlet rate of the air pole ranges from 0.667P to 3.33P, the oxygen generation rate ranges from 0.333P to 0.667P, and the fuel inlet rate ranges from 0.333P to 1P. The units are all mol / s, and P = 5 to 10 mol / s.

4. The SOEC system utilizing the heat of air-polarized gas as described in claim 1, characterized in that: The hydrogen inlet (7) is supplied by the pipeline between the fuel polar-side product outlet of the SOEC system and the hydrogen separation unit.

5. The SOEC system utilizing the heat of air-polarized gas as described in any one of claims 1 to 4, characterized in that: in In the raw material mixing device (12), the water vapor and hydrogen mixture has a molar ratio of 70-80% water vapor and 20-30% H2.

6. The SOEC system utilizing the heat of air-polarized gas as described in any one of claims 1 to 4, characterized in that: The hydrogen separation device includes a cooling device (18) and a drying device (17) connected to each other. The fuel polar product enters the hot end inlet of the cooling device (18), and the fuel polar product is connected to the cold end outlet of the cooling device (18) and the inlet of the drying device (17) through a pipe (19). The drying device (17) uses calcium oxide or concentrated sulfuric acid as a desiccant.

Images