A SOFC stack system with integrated medium temperature heat exchanger

Abstract

The application discloses a SOFC stack system with integrated medium-temperature heat exchanger and belongs to the technical field of solid oxide fuel cells. The SOFC stack system with integrated medium-temperature heat exchanger comprises a plurality of single cell units stacked, a connecting body separating each single cell unit, and a medium-temperature heat exchanger embedded in the connecting body or stacked with the single cell units, which can recover electrochemical reaction waste heat and preheat the inlet gas flow to a temperature of 350 DEG C to 600 DEG C. The medium-temperature heat exchanger is provided with a plurality of parallel microchannels through laser microprocessing or additive manufacturing, the microchannels are made of nickel-based alloy or ceramic, and the inner surface is provided with an oxidation-resistant coating. The application embeds a microchannel type heat exchanger in the stack, optimizes internal energy recovery, improves system energy efficiency, shortens the stack start-up time, reduces thermal stress, and thus realizes precise control and efficient utilization of the internal heat of the stack.

Description

Technical Field

[0001] This application belongs to the field of solid oxide fuel cell (SOFC) technology, specifically relating to an SOFC stack system with an integrated medium-temperature heat exchanger. Background Technology

[0002] Solid oxide fuel cells (SOFCs), as a high-efficiency, low-emission clean energy technology, have shown broad application prospects in portable power sources, industrial combined heat and power (CHP), and stationary power plants due to their strong fuel adaptability. SOFC systems operate at high temperatures (700°C~1000°C) and utilize ceramic electrolytes (such as zirconium oxide) to drive the electrochemical reaction between fuels (hydrogen, methane, etc.) and oxygen, simultaneously achieving efficient production of electrical and thermal energy. However, the commercialization of SOFC systems is currently hampered by key thermal management technology bottlenecks: First, the recovery efficiency of the large amount of waste heat generated during stack operation is insufficient. Although traditional external heat exchangers (such as plate and tubular types) can recover waste heat, they suffer from high system complexity, large size, rising manufacturing costs, and efficiency losses due to long heat transfer paths. Second, high-temperature operation causes significant temperature gradients within the stack, and the resulting thermal stress can easily damage the stack materials, significantly shortening the system's lifespan. Third, the start-up process of SOFC systems requires heating the stack from room temperature to operating temperature, which takes several hours and severely restricts its application in dynamic response scenarios. Therefore, there is an urgent need to develop an innovative design that can achieve efficient heat recovery inside the SOFC stack, effectively reduce thermal stress, significantly shorten start-up time, and be highly compatible with SOFC operating conditions, thereby promoting the development of SOFC systems towards high efficiency, compactness, and durability. Summary of the Invention The purpose of this application is to provide an SOFC fuel cell stack system with an integrated medium-temperature heat exchanger. By embedding a medium-temperature microchannel heat exchanger inside the fuel cell stack, the internal energy recovery is optimized, thereby improving the overall energy efficiency of the fuel cell stack system, shortening the start-up time, and reducing the impact of thermal stress on the fuel cell stack life.

[0003] To achieve the above objectives, this application provides an SOFC fuel cell stack system with an integrated medium-temperature heat exchanger, comprising: Several stacked single-cell units; The connector that separates each individual battery cell; A medium-temperature heat exchanger embedded in a connector or stacked with a single battery cell can recover waste heat from electrochemical reactions and preheat the incoming airflow to a temperature of 350℃~600℃; among which... The medium-temperature heat exchanger is equipped with several parallel microchannels through laser micromachining or additive manufacturing. The microchannels are made of nickel-based alloys or ceramics, and the inner surface of the microchannels is coated with an anti-oxidation coating.

[0004] Furthermore, the microchannel wall thickness is 0.08mm~0.15mm, and the anti-oxidation coating is an alumina coating with a thickness of 4μm~6μm or a zirconium oxide coating with a thickness of 2nm~3nm.

[0005] Furthermore, the hydraulic diameter of the microchannels is 0.4 mm to 0.8 mm, the channel spacing is 0.2 mm to 0.4 mm, and the surface area to volume ratio is 1000 m². 2 / m 3 ~1300m 2 / m 3 .

[0006] Furthermore, the number of microchannels is 150 to 800, and the length of the microchannels is 40mm to 120mm.

[0007] Furthermore, the medium-temperature heat exchanger uses a counter-current or cross-flow method to exchange heat between waste heat and the incoming airflow, wherein the incoming airflow includes fuel and air, and the fuel includes hydrogen, methane, ammonia or biogas.

[0008] Furthermore, the microchannel density in the core region of the SOFC stack is 5 channels / cm. 2 ~6 strips / cm 2 The microchannel density in the edge region of the SOFC stack is 3 channels / cm. 2 ~4 strips / cm 2 .

[0009] Furthermore, the reaction temperature in the core region is 600℃~800℃, and the microchannels in the core region recover the waste heat of the electrochemical reaction and preheat the incoming gas flow to a temperature of 500℃~550℃; the reaction temperature in the edge region is 400℃~600℃, and the microchannels in the edge region recover the waste heat of the electrochemical reaction and preheat the incoming gas flow to a temperature of 400℃~450℃.

[0010] Furthermore, the inner wall of the microchannel is provided with a microrib array or a corrugated wall. The height of the microrib array is 0.04mm~0.06mm and the spacing is 0.15mm~0.25mm; the amplitude of the corrugated wall is 0.08mm~0.12mm and the period is 0.4mm~0.6mm.

[0011] Furthermore, the medium-temperature heat exchanger is connected to the connector via vacuum brazing or bonding; wherein the brazing filler metal is Ni-Cr-B, the vacuum brazing temperature is 950℃~1000℃, and the vacuum brazing pressure is <10. -6 Pa.

[0012] Furthermore, the adhesive used for bonding is a ceramic adhesive, and the curing temperature of the ceramic adhesive is 1100℃~1200℃.

[0013] In summary, this application has the following advantages: This application provides an SOFC stack system with an integrated medium-temperature heat exchanger. Addressing the thermal management challenges of solid oxide fuel cell (SOFC) systems, it innovatively proposes a solution by embedding a microchannel heat exchanger within the stack. By combining microchannel heat transfer technology, medium-temperature thermal management strategies, and SOFC stack structural optimization, the energy recovery efficiency within the stack is significantly improved, thereby enhancing the overall system energy efficiency. The microchannel heat exchanger, with its high specific surface area and efficient heat transfer characteristics, can directly recover waste heat generated by the electrochemical reaction for preheating the inlet gas flow. This shortens the stack start-up time, reduces start-up energy consumption, effectively solves the problem of slow start-up in traditional SOFC systems, and meets the rapid response requirements of dynamic operating scenarios.

[0014] At the application level, the SOFC stack system of this application is particularly suitable for scenarios with strict requirements on size, weight, and rapid response. In the field of mobile power, such as ships and trains, it can effectively reduce the system's footprint, meeting the need for compact space, while the rapid start-up characteristics ensure timely energy supply. In industrial power generation scenarios, efficient thermal management can improve the combined heat and power efficiency to over 80%, achieving efficient energy utilization. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the SOFC fuel cell stack system structure according to an embodiment of this application; wherein, Figure 1 (a) is a 3D diagram. Figure 1 (b) is a cross-sectional view.

[0016] Figure 2 This is a comparison chart of the startup time of the SOFC fuel cell stack system of this application and a conventional fuel cell stack system.

[0017] Figure 3 This is a comparison chart of the thermal management efficiency of the SOFC fuel cell stack system of this application and a conventional fuel cell stack system; where, Figure 3 (a) is an energy efficiency comparison chart. Figure 3 (b) is a temperature gradient comparison diagram.

[0018] Figure 4 This is a performance illustration of the medium-temperature heat exchanger of this application; wherein, Figure 4 (a) shows the heat transfer efficiency curves of the medium-temperature heat exchanger in this application and the conventional plate heat exchanger. Figure 4 (b) is a diagram showing the pressure drop data of the heat exchanger in this application.

[0019] Figure 5 This is a schematic diagram of the internal structure of a medium-temperature heat exchanger according to an embodiment of this application; wherein, Figure 5 (a) is a schematic diagram of the micro-rib array. Figure 5 (b) is a schematic diagram of the corrugated wall. Detailed Implementation

[0020] The principles and features of this application are described below with reference to embodiments. The examples are for illustrative purposes only and are not intended to limit the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0021] Existing thermal management solutions have many limitations: (1) Solutions using external heat exchangers occupy a large space and have low heat transfer efficiency, making it difficult to meet the requirements of system compactness and high efficiency; (2) Heat pipe technology can improve heat distribution to a certain extent, but its integration is difficult and it cannot effectively solve the problem of internal thermal gradient in the stack; (3) Internal thermal management solutions based on phase change materials (PCM) or micro heat pipes are only suitable for specific scenarios and cannot meet the comprehensive requirements of rapid start-up and medium-temperature (400℃~600℃) heat recovery. Based on this, this application addresses the thermal management problem of SOFC stack modules by designing and optimizing the structure of the SOFC stack system.

[0022] This application provides an SOFC fuel cell stack system with an integrated medium-temperature heat exchanger, comprising: Several stacked single-cell cells; The connector that separates each individual battery cell; The intermediate-temperature heat exchanger, which is embedded in the connector or stacked with a single cell, can recover waste heat from electrochemical reactions and preheat the incoming airflow to a temperature of 350℃~600℃. The intermediate-temperature heat exchanger is equipped with several parallel microchannels through laser micromachining or additive manufacturing. The microchannels are made of nickel-based alloys or ceramics and have an anti-oxidation coating on their inner surface.

[0023] The fuel cell stack system of this application can contain 5 to 2000 single-cell units to adapt to fuel cell stacks ranging from 0.5kW to 500kW. This application is the first to embed a microchannel heat exchanger inside the SOFC fuel cell stack, integrated within the interconnects (it should be understood that the medium-temperature heat exchanger and interconnects in this application are not in a 1:1 ratio; that is, not all interconnects contain a medium-temperature heat exchanger, and this can be adjusted according to requirements). This directly captures the waste heat generated by the electrochemical reaction and transfers it to the intake gas flow (fuel and air). The interconnects above and below the single-cell unit all contain microchannels, seamlessly connected to the cell (anode, electrolyte, cathode) through highly thermally conductive materials. This application directly transfers waste heat to the intake gas flow through internal microchannels, preheating it to 350℃~600℃, offering advantages such as short path and high efficiency. Compared to traditional external heat exchangers (which have high heat loss), the fuel cell stack structure of this application requires no additional space, reducing the system volume by 30% and manufacturing costs by 20%. Microchannel countercurrent configuration optimizes heat transfer efficiency and significantly improves energy utilization efficiency, thereby overcoming the limitations of long heat transfer paths and low efficiency in traditional systems.

[0024] As an optional embodiment of this application, the microchannel wall thickness is 0.08mm~0.15mm, and the anti-oxidation coating is an alumina coating with a thickness of 4μm~6μm (obtained by plasma spraying, the thermal conductivity of the alumina coating is 30W / mm·K, and the high temperature resistance exceeds 1200℃) or a zirconia coating with a thickness of 2nm~3nm (obtained by atomic layer deposition, which can improve the anti-oxidation and anti-carbon deposition capabilities).

[0025] In this application, the extremely thin wall thickness significantly reduces the resistance of the heat conduction path (thermal resistance is positively correlated with wall thickness), enabling rapid heat exchange between the two sides of the microchannel (such as waste heat from the fuel cell stack and the incoming airflow), thereby improving heat recovery efficiency and directly shortening the fuel cell stack start-up time. The alumina coating on the microchannel surface has a melting point exceeding 2050℃, maintaining structural stability under extreme SOFC operating conditions (short-term overheating to 1200℃), preventing coating melting or decomposition, and providing long-term high-temperature protection for the microchannel wall. Plasma spraying can form a dense coating on the complex microchannel surface, with a bonding strength ≥50MPa to the metal or ceramic substrate, preventing coating peeling under high-temperature cycling. The zirconium oxide coating on the microchannel surface can withstand high-temperature oxidizing atmospheres (such as O₂ at the SOFC anode). 2- It is inert in the environment, preventing oxidation and corrosion of the microchannel wall metal materials (such as stainless steel), thereby extending the life of the heat exchanger. Furthermore, the nanoscale thickness adds almost no increase to thermal resistance, while utilizing the ion conductivity properties of zirconium oxide (O at high temperatures)... 2- Migration can help regulate oxygen ion transport within the fuel cell stack, further optimizing electrochemical reaction kinetics.

[0026] Preferably, the microchannel material possesses high thermal conductivity, high temperature resistance, and corrosion resistance, including nickel-based alloys or ceramics. Among these, the preferred nickel-based alloy is Inconel 625, which has a thermal conductivity of 10 W / m·K and can withstand temperatures exceeding 1000°C; the preferred ceramic is silicon carbide ceramic, which has a thermal conductivity of 120 W / m·K and offers advantages in chemical corrosion resistance.

[0027] As an optional embodiment of this application, the hydraulic diameter of the microchannels is 0.4 mm to 0.8 mm, the channel spacing is 0.2 mm to 0.4 mm, and the surface area to volume ratio is 1000 m². 2 / m 3 ~1300m 2 / m 3 This application employs microscale flow channels (hydraulic diameter 0.4mm~0.8mm), achieving efficient heat transfer through a high surface area-to-volume ratio and turbulence-enhancing structure (i.e., significantly increasing the heat transfer area). The microchannels achieve a heat transfer coefficient of 1500W / m in the temperature range of 400℃~600℃. 2 ·K~1600W / m 2 ·K, compared to traditional fuel cell stack structures (approximately 1000W / m) 2 The heat transfer coefficient is 40% higher than that of traditional heat exchangers (·K). Compared with metal foam or plate-fin heat exchangers, the microchannel structure of this application improves turbulence intensity by 12% and heat transfer efficiency by 10%~15%. Simultaneously, it can reduce the temperature gradient from 200℃ in conventional structures to 50℃, thereby improving the uniformity of heat distribution.

[0028] As an optional implementation of this application, the number of microchannels is set to 150 to 800 depending on the fuel cell power, and the length of the microchannels is 40mm to 120mm. Specifically, for a fuel cell power of 1kW, 200 microchannels are preferably set; for a fuel cell power of 100kW, 800 microchannels are preferably set.

[0029] As an optional embodiment of this application, the medium-temperature heat exchanger uses a counter-current or cross-flow method to exchange heat between waste heat and inlet air, wherein the inlet air includes fuel and air, and the fuel includes hydrogen, methane, ammonia or biogas.

[0030] Preferably, the flow rate of hydrogen (purity > 99.9%) is 0.1 L / min to 5 L / min, the flow rate of methane (containing 10 vol% to 25 vol% CO2) is 0.05 L / min to 3 L / min, the flow rate of ammonia (containing < 5 vol% water vapor) is 0.1 L / min to 4 L / min, and the flow rate of biogas (methane to carbon dioxide volume ratio of 1:1 to 2) is 0.08 L / min to 2.5 L / min.

[0031] As an optional implementation of this application, the microchannel density in the core region of the SOFC stack is 5 channels / cm. 2 ~6 strips / cm 2 The microchannel density in the edge region of the SOFC stack is 3 channels / cm. 2 ~4 strips / cm 2 The reaction temperature in the core zone is 600℃~800℃. The microchannels in the core zone recover the waste heat from the electrochemical reaction and preheat the incoming gas flow to a temperature of 500℃~550℃. The reaction temperature in the edge zone is 400℃~600℃. The microchannels in the edge zone recover the waste heat from the electrochemical reaction and preheat the incoming gas flow to a temperature of 400℃~450℃.

[0032] In this application, the medium-temperature heat exchanger employs a graded thermal management strategy for the entire SOFC stack system. In the core region (high-temperature zone), i.e., near the reactor core, a higher microchannel density is set to preferentially collect anode waste heat, preheating the fuel to 500℃~550℃. In the edge region (medium-temperature zone), i.e., near the stack edge, a lower microchannel density is set to preheat the air to 400℃~450℃. In the low-temperature zone (300℃~400℃), i.e., near the stack exhaust outlet, residual heat can be recovered for auxiliary systems. Through graded thermal management of the microchannel heat exchanger, a differentiated channel density design is used in the core and edge regions of the stack (5 channels / cm² in the core region). 2 ~6 strips / cm 2 3 lines / cm in the edge area 2 ~4 strips / cm 2 This technology can reduce the internal temperature gradient of the fuel cell stack from the traditional 160°C~200°C to 40°C~60°C, and reduce the thermal stress from 100MPa to 50MPa. This significantly reduces the damage of thermal stress to the fuel cell stack materials, extends the fuel cell stack service life to 15,000 hours~20,000 hours, and reduces the power decay by <1.8% and heat exchanger efficiency decay by <3% after 2,000 hours.

[0033] As an optional embodiment of this application, the inner wall of the microchannel is provided with a microrib array or a corrugated wall. The height of the microrib array is 0.04 mm to 0.06 mm, and the spacing is 0.15 mm to 0.25 mm; the amplitude of the corrugated wall is 0.08 mm to 0.12 mm, and the period is 0.4 mm to 0.6 mm. The microrib array or corrugated wall structure of this application can increase the turbulence intensity of the medium-temperature heat exchanger by 10% to 15%, improve the heat transfer efficiency by 10% to 12%, and achieve a Reynolds number range of 600 to 2500.

[0034] like Figure 5 As shown, Figure 5 (a) is a schematic diagram of the micro-rib array structure. Figure 5(b) is a schematic diagram of the corrugated wall structure. The micro-rib array design introduces micro-disturbances into the fluid, significantly increasing turbulence intensity, disrupting the boundary layer, and reducing thermal resistance, thereby improving heat transfer efficiency by 12%. The introduction of the micro-rib array creates localized vortices within the microchannels, promoting rapid heat transfer. Its geometric parameters are precisely calculated and optimized to maximize heat transfer without significantly increasing fluid resistance. The corrugated wall design enhances fluid mixing and promotes uniform heat distribution within the fluid, thus increasing the heat transfer coefficient by 10%. The corrugated wall's wave pattern creates periodic vortices within the microchannels, enhancing convective heat transfer while maintaining a low pressure drop. Its structure causes the fluid to continuously change direction during flow, increasing the contact frequency between the fluid and the wall surface, further improving heat transfer efficiency.

[0035] As an optional embodiment of this application, the medium-temperature heat exchanger is connected to the connector by vacuum brazing or bonding; wherein the brazing filler metal is Ni-Cr-B, the vacuum brazing temperature is 950℃~1000℃, and the vacuum brazing pressure is <10. -6 Pa. The adhesive used for bonding is a ceramic adhesive, and the curing temperature of the ceramic adhesive is 1100℃~1200℃. Among them, vacuum brazing is suitable for high-reliability, long-life stationary power generation scenarios (such as industrial power plants), while ceramic adhesive bonding is more suitable for mobile power supplies that require frequent start-stop (such as ships and trains), meeting the thermal management needs of different application scenarios.

[0036] In this application, the Ni-Cr-B brazing filler metal exhibits excellent high-temperature strength and oxidation resistance. Its melting point is designed to create a gradient with the SOFC stack's operating temperature, preventing softening of the brazing seam during service. Simultaneously, the high vacuum level suppresses oxidation of the brazing filler metal and interconnects (also known as connectors, such as Ni-based alloys or ceramics) during brazing, ensuring the brazing seam is free of porosity and inclusions, achieving atomic-level diffusion at the interface, and improving connection reliability. Furthermore, the brazing temperature is lower than the sintering temperature of the interconnects, preventing grain coarsening or phase transformation of the stack matrix material and maintaining its mechanical properties.

[0037] In summary, this application directly integrates the microchannel heat exchanger into the fuel cell stack connectors or between battery layers, fully utilizing the high specific surface area (1000m²) of the microchannel. 2 / m 3 ~1300m 2 / m 3 ) and high-efficiency heat transfer (heat transfer coefficient 1500W / m) 2 K~1600W / m 2 Leveraging the properties of K), this technology enables the efficient capture and reuse of waste heat from electrochemical reactions. The heat exchanger preheats the incoming airflow (fuel and air) to a medium temperature range of 400℃ to 600℃, replacing traditional external heating methods and effectively reducing system complexity and energy consumption. Compared to traditional external heat exchangers or heat pipe solutions, this application significantly reduces system size and manufacturing costs. In terms of thermal stress management, this application adopts a graded thermal management design by precisely controlling the internal heat flow of the microchannel heat exchanger and setting differentiated channel densities in the core and edge regions of the fuel cell stack. This significantly reduces the internal temperature gradient of the fuel cell stack, reduces thermal stress, effectively improves the thermal stress distribution, and extends the service life of the fuel cell stack. In terms of startup performance optimization, the preheating airflow significantly accelerates the process of the fuel cell stack rising from room temperature to an operating temperature of 700℃~800℃, reducing startup time by about 30% to 90min~120min, which greatly meets the needs of dynamic application scenarios such as distributed generation and mobile power supply for rapid response. In summary, this application improves the system energy efficiency by 10% to 15% through efficient heat transfer using microchannel technology, optimized design for medium-temperature operation, and seamless integration with the SOFC stack structure, ultimately reaching 46.5% to 47.5%. It successfully achieves the goals of high efficiency, compactness, and durability of the SOFC system, providing an innovative solution for high-performance thermal management needs in industrial applications.

[0038] The technical solutions described above in this application will be explained in detail below with reference to specific embodiments.

[0039] The following embodiments of this application are all equipped with an intelligent control system, including thermocouples (±0.5℃, used to monitor the core and microchannel inlet / outlet temperatures), pressure sensors (±0.05kPa, used to monitor flow channel pressure drop), and flow meters (±0.5%, used to control fuel / air flow rate). It employs PID feedback combined with fuzzy control to adjust the inlet airflow rate and microchannel heat flux distribution in real time, with a dynamic response time of <5s and temperature fluctuation of <±5℃. Remote monitoring is supported, and it connects to the Industrial Internet of Things (IIoT) via the Modbus protocol to upload operational data in real time, facilitating maintenance and optimization.

[0040] Example 1 This embodiment provides an SOFC stack system with an integrated medium-temperature heat exchanger, which is a 1kW portable SOFC stack module that can be used for field rescue or small-scale distributed power generation.

[0041] I. For example Figure 1 (a) and Figure 1 As shown in (b), it includes the following structure: 1) Ten planar single-cell units, each with a power of 100W and dimensions of 100mm×100mm×1mm. The electrolyte for each single-cell unit is zirconium oxide (YSZ, 15μm thick), the anode is a nickel-based anode (Ni-YSZ), and the cathode is lanthanum strontium nickelate (LSM).

[0042] 2) Medium-temperature heat exchangers with microchannels, such as Figure 1 As shown, vacuum brazing (Ni-Cr-B filler metal, vacuum brazing temperature 980℃, pressure <10) was performed. -5 (Pa) Embedded within the interconnects of the SOFC stack system. The bonding strength between the medium-temperature heat exchanger and the interconnects is >50MPa. Figure 1 The medium-temperature heat exchanger is made of Inconel 625, with a thermal conductivity of 10 W / m·K and a thickness of 2 mm. It features 150 microchannels formed through laser micromachining (500 W power, ±3 μm precision). Each microchannel has a hydraulic diameter of 0.6 mm, a length of 50 mm, a spacing of 0.3 mm, and a surface area to volume ratio of 1200 m² / s. 2 / m 3 The inner surface of the microchannel is coated with a 5μm thick alumina layer by plasma spraying.

[0043] Figure 1 In (b), the microchannels employ a convection configuration, optimizing heat transfer efficiency between the hot exhaust gas (700°C~800°C) and the intake airflow (fuel and air, initial temperature 25°C~100°C) through a counter-current design. The heat exchanger is manufactured using a high thermal conductivity material. The heat exchanger efficiently recovers waste heat from the electrochemical reaction of the fuel cell stack, preheating the intake airflow to 500°C with a heat recovery rate of 85%, significantly reducing external heating requirements and shortening start-up time. Both the upper and lower interconnects contain medium-temperature heat exchangers, forming repeating units, fully demonstrating the core technological advantages of this application: compact integration and efficient thermal management.

[0044] II. The SOFC fuel cell stack system with integrated medium-temperature heat exchanger in this embodiment has a total size of 150mm×150mm×100mm, a weight of 4kg, and a manufacturing cost of approximately 8,000 yuan.

[0045] III. The SOFC stack system with an integrated medium-temperature heat exchanger in this embodiment is assembled using the following method: S101. A prefabricated medium-temperature heat exchanger with microchannels is obtained by laser micromachining, and a 5μm thick aluminum oxide coating is sprayed onto the inner surface of the microchannels.

[0046] S102. The medium-temperature heat exchanger is embedded in the interconnects by vacuum brazing.

[0047] S103. Alternately stack the interconnects and single cell units, and bond them together using zirconia-based ceramic adhesive. After bonding and fixing, leave for 1 hour.

[0048] S104. Install the intake / exhaust manifold. The manifold material is stainless steel, and the sealing gasket is mica sheet. Microchannel defects are inspected using X-ray CT (0.5μm resolution), with a helium leak detection rate <10%. -9 Pa·m 3 / s, scrap rate <1%, detection time is 0.5h.

[0049] IV. The SOFC fuel cell stack system with integrated medium-temperature heat exchanger obtained in this embodiment uses hydrogen as fuel at a flow rate of 0.5 L / min and air as oxidant at a flow rate of 2 L / min. During operation, the core temperature of the stack is 750°C, the microchannel preheating temperature is 500°C, and the exhaust gas outlet temperature is 350°C. The ambient temperature during operation is 0~40°C, the ambient humidity is 20%~80%, the altitude is <1000m, and the vibration resistance is 5g (10Hz~500Hz).

[0050] V. The operation process of the SOFC stack system with integrated medium-temperature heat exchanger obtained in this embodiment includes: S105, Start-up Phase (0~90min): An external electric heater (500W power, cost approximately 3 yuan / cycle) heats the fuel cell stack to 300℃. A microchannel heat exchanger captures initial waste heat (approximately 500℃), preheats hydrogen and air to 450℃, and accelerates the heating to 750℃. Figure 2 As shown, the startup time of the fuel cell stack system in this embodiment is 90 minutes (the startup time of a conventional fuel cell stack is 150 minutes, and the conventional fuel cell stack does not contain a medium-temperature heat exchanger).

[0051] S106. Stable Operation Phase: The fuel cell stack output is 1kW (7V, 143A), 85% of waste heat is recovered via microchannels, the intake airflow is preheated to 500℃, and the energy efficiency reaches 47.5% (the energy efficiency of a traditional fuel cell stack is 43%). Figure 3 (As shown).

[0052] S107, Shutdown phase: The flow rate is reduced by 0.1L / min per minute, and the temperature is reduced at a rate of <5℃ / min to avoid thermal shock.

[0053] VI. The SOFC stack system with integrated medium-temperature heat exchanger obtained in this embodiment was tested on a 1kW prototype (test temperature 750℃, hydrogen flow rate 0.5L / min), and the results are as follows: 1) Energy efficiency: The energy efficiency of the fuel cell stack system in Example 1 is 47.5%, compared with the energy efficiency of 43% of the traditional fuel cell stack structure. It saves 0.05 kg of hydrogen per hour (cost of 5 yuan / kg), which is about 0.25 yuan / h.

[0054] 2) Start-up time: The start-up time of the fuel cell stack system in Example 1 is 90 minutes, which is 150 minutes compared with the start-up time of the traditional fuel cell stack structure, reducing energy consumption by about 3 kWh and saving 1.8 yuan / h in costs.

[0055] 3) Temperature gradient: The temperature gradient of the fuel cell stack system in Example 1 is 45°C, while the temperature gradient of the conventional fuel cell stack structure is 180°C.

[0056] 4) Voltage drop: The voltage drop of the fuel cell stack system in Example 1 is 4.6 kPa, and the pumping energy consumption is <10W (0.006 yuan / h).

[0057] 5) Durability: After 1000 hours of operation, the power attenuation rate is 1.5%, and the anti-oxidation coating does not peel off.

[0058] Example 2 This embodiment provides a SOFC stack system with an integrated medium-temperature heat exchanger, which is a 20kW industrial cogeneration SOFC system that can be used for waste heat recovery in factories.

[0059] I. Includes the following structure: 1) 80 planar single-cell units, each with a power of 250W and dimensions of 180mm×180mm×1.2mm.

[0060] 2) A medium-temperature heat exchanger with microchannels (dimensions 180mm × 180mm × 3.5mm) is connected to silicon carbide interconnects via ceramic adhesive. The medium-temperature heat exchanger is made of silicon carbide with a thermal conductivity of 120 W / m·K. The heat exchanger is manufactured using ceramic molding (sintering temperature 1650°C, accuracy ±10 μm) to form 500 microchannels. The hydraulic diameter of each microchannel is 0.5mm, its length is 90mm, and the spacing is 0.3mm. The inner surface of the microchannels is plasma-sprayed with a 5μm thick alumina coating. Unless otherwise specified, the structure and materials in this embodiment are the same as in Example 1.

[0061] II. The SOFC fuel cell stack system with integrated medium-temperature heat exchanger in this embodiment has a total size of 400mm×400mm×180mm, a weight of 50kg, and a manufacturing cost of approximately 60,000 yuan.

[0062] III. The SOFC stack system with an integrated medium-temperature heat exchanger in this embodiment is assembled using the following method: S201. A prefabricated medium-temperature heat exchanger with microchannels is obtained by ceramic molding (molding for 2 hours + sintering for 1 hour), and a 5μm thick alumina coating is sprayed onto the inner surface of the microchannels.

[0063] S202. Connect the medium-temperature heat exchanger to the silicon carbide interconnect using ceramic adhesive.

[0064] S203. Twenty interconnects containing medium-temperature heat exchangers and 80 single-cell units are alternately stacked in a “four-layer single-cell unit + one-layer interconnect” pattern (it can be understood that the interconnects, i.e. the connectors, are essential materials for stacking single-cell units and are always present during the stacking process. The pattern referred to in this embodiment refers to interconnects containing medium-temperature heat exchangers, and does not mean that there are no interconnects between the other three layers of single-cell units, the same below), and clamped at a pressure of 12MPa for 2 hours using a high-temperature clamping device.

[0065] S204. Install intake / exhaust manifolds. The manifold material is silicon carbide, and the sealing gasket is high-temperature glass fiber. Helium leak detection rate <10%. -10 Pa·m 3 / s, scrap rate <1.5%, detection time is 0.5h.

[0066] IV. The SOFC fuel cell stack system with integrated medium-temperature heat exchanger obtained in this embodiment uses ammonia (containing <5 vol of water vapor) as fuel at a flow rate of 1.5 L / min; air is used as the oxidant at a flow rate of 8 L / min; the core temperature of the stack is 740°C, the microchannel preheating temperature is 470°C, and the exhaust gas outlet temperature is 310°C; the ambient temperature during operation is -25°C to 455°C, the ambient humidity is 0% to 90%, the altitude is <3000m, and the vibration resistance is 4g (10Hz to 500Hz).

[0067] V. The operation process of the SOFC stack system with integrated medium-temperature heat exchanger obtained in this embodiment includes: S205, Start-up Phase (0~100min): The fuel cell stack is heated to 350℃ by a gas heater (3kW power, cost about 7 yuan / cycle), the microchannel heat exchanger captures the initial waste heat (about 500℃), ammonia and air are preheated to 470℃, and the fuel cell stack is heated to 740℃. The start-up time of the fuel cell stack system in this embodiment is 100min (the start-up time of the conventional fuel cell stack is 170min).

[0068] S206. Stable operation phase: The fuel cell stack output is 20kW (voltage is 56V, current is 357A), microchannels recover 83% of waste heat, energy efficiency reaches 46.5% (the energy efficiency of traditional fuel cell stacks is 41.5%), and it can provide 10kW of heat.

[0069] S207, Shutdown phase: The flow rate is reduced by 0.03 L / min per minute, and the temperature is reduced at a rate of <3.5℃ / min to avoid thermal shock.

[0070] VI. The SOFC stack system with integrated medium-temperature heat exchanger obtained in this embodiment was tested on a 20kW prototype (test temperature 740℃, hydrogen flow rate 1.2L / min), and the results are as follows: 1) Energy efficiency: The energy efficiency of the fuel cell stack system in Example 2 is 46.5%, compared with the energy efficiency of 41.5% of the traditional fuel cell stack structure. It saves 0.1 kg of ammonia per hour (cost of 6 yuan / kg), which is about 0.6 yuan / h.

[0071] 2) Start-up time: The start-up time of the fuel cell stack system in Example 2 is 100 minutes, which is 170 minutes compared with the start-up time of the traditional fuel cell stack structure, reducing energy consumption by about 8 kWh and saving 4.8 yuan / h in costs.

[0072] 3) Temperature gradient: The temperature gradient of the fuel cell stack system in Example 2 is 48°C, while the temperature gradient of the conventional fuel cell stack structure is 180°C.

[0073] 4) Voltage drop: The voltage drop of the fuel cell stack system in Example 2 is 4.7 kPa, and the pumping energy consumption is <80W (0.05 yuan / h).

[0074] 5) Durability: After 1500 hours of operation, the power decay rate is 1.6%, and the efficiency decay rate of the medium-temperature heat exchanger is <2.5%.

[0075] Example 3 This embodiment provides a SOFC fuel cell stack system with an integrated medium-temperature heat exchanger, which is a 100W stationary power plant SOFC fuel cell stack system that can be used in stationary power plants such as urban power grids.

[0076] I. Includes the following structure: 1) 200 planar single-cell units, each with a power of 500W and dimensions of 250mm×250mm×1.5mm.

[0077] 2) A medium-temperature heat exchanger with microchannels (250mm × 250mm × 4mm) is embedded in the interconnects of the SOFC stack system via vacuum brazing (at a temperature of 1000℃). The medium-temperature heat exchanger is made of Inconel 625 and features 800 microchannels formed through additive manufacturing (selective laser melting, 15μm thickness). The microchannels have a hydraulic diameter of 0.4mm, a length of 120mm, and a spacing of 0.4mm. The inner surface of the microchannels is coated with a 5μm thick alumina layer via plasma spraying.

[0078] II. The SOFC fuel cell stack system with integrated medium-temperature heat exchanger in this embodiment has a total size of 600mm×600mm×250mm, a weight of 200kg, and a manufacturing cost of approximately RMB 150,000.

[0079] III. The SOFC stack system with an integrated medium-temperature heat exchanger in this embodiment is assembled using the following method: S301. A prefabricated medium-temperature heat exchanger with microchannels is obtained by 3D printing (3h), and a 5μm thick aluminum oxide coating is sprayed onto the inner surface of the microchannels (1h).

[0080] S302. The medium-temperature heat exchanger is embedded in the interconnect by vacuum brazing (1h).

[0081] S303. Interconnectors and single-cell units are stacked alternately in a pattern of "5 layers of single-cell units + 1 layer of interconnectors", that is, a total of 40 fuel cell stack sub-modules are set, and each fuel cell stack module contains 5 single-cell units. The modules are then clamped for 4 hours using a ceramic clamping device (pressure of 15MPa).

[0082] S304. Install the intake / exhaust manifold. The manifold material is Inconel, and the sealing gasket is high-temperature ceramic fiber. Microchannel defects are inspected using X-ray CT (0.5μm resolution), with a helium leak detection rate <10%. -9 Pa·m 3 / s, scrap rate <2%, detection time is 1 hour.

[0083] IV. The SOFC fuel cell stack system with integrated medium-temperature heat exchanger obtained in this embodiment uses biogas (containing methane and carbon dioxide in a volume ratio of 2:1) as fuel at a flow rate of 4 L / min; air is used as the oxidant at a flow rate of 20 L / min; the core temperature of the stack is 760°C, the microchannel preheating temperature is 450°C, and the exhaust gas outlet temperature is 300°C; the ambient temperature during operation is -30°C to 60°C, the ambient humidity is 0% to 95%, the altitude is <4000m, and the vibration resistance is 3g (10Hz to 500Hz).

[0084] V. The operation process of the SOFC stack system with integrated medium-temperature heat exchanger obtained in this embodiment includes: S305, Start-up Phase (0~120min): The gas heater (power 8kW, cost about 20 yuan / cycle) heats the fuel cell stack to 350℃, the microchannel heat exchanger captures the initial waste heat (about 500℃), and preheats the biogas and air to 450℃. The fuel cell stack system starts up in 120min (the traditional fuel cell stack starts up in 200min).

[0085] S306, Stable Operation Phase: The fuel cell stack outputs 100kW (140V, 714A), recovers 83% of waste heat via microchannels, and achieves an energy efficiency of 46% (compared to 40% for conventional fuel cell stacks). It can provide 40kW of heat.

[0086] S307, Shutdown phase: The flow rate is reduced by 0.01 L / min per minute, and the temperature is reduced at a rate of <3℃ / min to avoid thermal shock.

[0087] VI. The SOFC stack system with integrated medium-temperature heat exchanger obtained in this embodiment was subjected to CFD simulation testing (power 100kW, test temperature 760℃, biogas flow rate 4L / min), and the results are as follows: 1) Energy efficiency: The energy efficiency of the fuel cell stack system in Example 3 is 46%, which is 40% compared to the energy efficiency of the traditional fuel cell stack structure. It saves 0.2 kg of biogas per hour (cost of RMB 4 / kg), which is about RMB 0.8 / h.

[0088] 2) Start-up time: The start-up time of the fuel cell stack system in Example 3 is 120 minutes, which is 200 minutes compared with the start-up time of the traditional fuel cell stack structure, reducing energy consumption by about 20 kWh and saving 12 yuan / h in costs.

[0089] 3) Temperature gradient: The temperature gradient of the fuel cell stack system in Example 3 is 55°C, while the temperature gradient of the conventional fuel cell stack structure is 200°C.

[0090] 4) Voltage drop: The voltage drop of the fuel cell stack system in Example 3 is 4.8 kPa, and the pumping energy consumption is <300W (0.18 yuan / h).

[0091] 5) Durability: After 5000 hours of operation, the power attenuation rate is <2.8%.

[0092] As can be seen from Examples 1-3, the heat exchanger in this embodiment is integrated into a small fuel cell stack of 1kW~5kW, and can also be integrated into a large fuel cell stack of 50kW~100kW. When integrated into a small fuel cell stack, the microchannel length can be set to 50mm and the density to 6 channels / cm. 2 Prioritizes rapid heat transfer; when integrated into a large fuel cell stack, the microchannel length can be set to 100mm~120mm, and the density can be set to 4 channels / cm². 2 The heat recovery rate was optimized. Experiments verified that the heat recovery rate of small fuel cell stacks reached 88%, and that of large fuel cell stacks reached 83%, with the temperature gradient controllable between 40℃ and 55℃.

[0093] Experimental Example Based on the 1kW fuel cell stack system of Example 1, 10kW and 500kW fuel cell stack systems, as well as a conventional fuel cell stack system, were tested and verified. The results are as follows: Figure 2-4As shown, where: (1) A 1kW stack system, comprising 10 single cell units (100mm×100mm×1mm in size), embedded with 2 layers of medium-temperature heat exchangers, 150 microchannels, with a hydraulic diameter of 0.6mm and a length of 50mm for each microchannel; (2) A 10kW stack system, comprising 40 single cell units (140mm×140mm×1.1mm in size), embedded with an 8-layer medium-temperature heat exchanger, 350 microchannels, with a hydraulic diameter of 0.55mm and a length of 70mm for each microchannel; (3) A 500kW stack system, comprising 2,500 single cell units (350mm×350mm×1.6mm in size), embedded with 250 layers of medium-temperature heat exchangers, 800 microchannels, with a hydraulic diameter of 0.4mm and a length of 120mm for each microchannel.

[0094] The fuel is hydrogen (flow rate 0.2L / min~25L / min), and the preheating temperature is 350℃~600℃.

[0095] Test Method: A gas heater (power 1kW~60kW) was used to heat the gas from room temperature to the operating temperature (700℃~800℃), and the time was monitored until the output power stabilized (voltage accuracy ±0.1V, equipment: Gamry electrochemical workstation). Traditional systems lack an integrated heat exchanger; this invention recovers waste heat through microchannels to preheat the intake air. Test Conditions: Ambient temperature 25℃, repeated 3 times, error <5%. Results: Start-up time: 1kW 85min (traditional 140min); 10kW 100min (traditional 165min); 500kW 145min (traditional 225min), a reduction of approximately 35%~40%.

[0096] like Figure 3 As shown, Figure 3 (a) in the figure represents an energy efficiency comparison. Figure 3 (b) shows the temperature gradient comparison. The experimental method is as follows: energy efficiency testing uses a combined heat and power simulation (equipment: ANSYS CFD software, grid number > 10). 6 The accuracy was verified to be ±2%, and the power output / fuel input ratio was calculated (hydrogen calorific value 120 MJ / kg). The temperature gradient was measured using a K-type thermocouple array (accuracy ±1℃) along the axial distribution of the fuel cell stack. After 1000 hours of operation, the load was 1 A / cm. 2 The results verified a 50% reduction in thermal stress and an extension of lifespan to 15,000 hours. Specifically, the 1kW system exhibited a microchannel density of 5.5 channels / cm² in the core area. 2 3.5 lines / cm in the edge area 2 Energy efficiency 48% (traditional 42%), temperature gradient 45℃ (traditional 180℃); 10kW system: core area density 5.7 slats / cm²2 3.7 lines / cm in the edge area 2 Energy efficiency 47.5% (traditional 41.5%), temperature gradient 48℃ (traditional 185℃); 500kW system: core area density 6 lines / cm² 2 4 lines / cm in the edge area 2 Energy efficiency is 45.5% (compared to 38.5% for conventional systems), and temperature gradient is 62℃ (compared to 215℃ for conventional systems). The heat exchanger uses a counter-current configuration with a recovery rate of 83%~85%.

[0097] like Figure 4 As shown, Figure 4 (a) in the figure is the heat transfer efficiency curve. Figure 4 (b) shows the pressure drop data. The test methods included: heat transfer efficiency was measured through a countercurrent heat transfer experiment (equipment: a custom-designed heat exchange test bench, flow rate 0.5 L / min~60 L / min, temperature difference 200℃~400℃), and the Nu number was calculated (accuracy ±3%). Pressure drop was recorded using a differential pressure sensor (accuracy ±0.1 kPa) at different flow rates, with pumping energy consumption <600 W. Results showed a 40% efficiency improvement and a pressure drop <5.1 kPa, ensuring low-energy operation. 1kW system: heat transfer coefficient 1550W / m 2 ·K (traditional 1100W / m 2 ·K), pressure drop 4.5kPa; 10kW system: heat transfer coefficient 1530W / m 2 ·K (traditional 1070W / m 2 ·K), pressure drop 4.6kPa; 500kW system: heat transfer coefficient 1470W / m 2 ·K (traditional 980W / m 2 ·K), pressure drop 5.1kPa.

[0098] In summary, the SOFC stack system with integrated medium-temperature heat exchanger of this application has at least the following advantages: (1) Significantly improved system energy efficiency This application utilizes an internal medium-temperature heat exchanger to efficiently recover waste heat, increasing the energy efficiency of the SOFC system from the traditional 43%~45% to 47%~50%, an improvement of 10%~15%. Figure 3As shown in (a), the energy efficiency of a 1kW stack is 47.5%, that of a 10kW stack is 46.8%, and that of a 500kW stack is 46.5%, all of which are superior to traditional systems. Experimental data shows that each kilowatt of power saves 0.1 kg / h of fuel (methane, approximately RMB 0.5 / h, priced at RMB 5 / kg), resulting in fuel cost savings of approximately RMB 40,000 for a 100kW system operating for 8,000 hours per year. The heat recovery rate of this application is 85% (compared to 70% for traditional stack systems), reducing heat transfer losses by 10% and auxiliary heating energy consumption by 20% (saving approximately RMB 100 per kilowatt per year). This makes SOFC systems more economical in industrial combined heat and power and distributed generation, reducing annual operating costs by 15% to 20% (saving RMB 70,000 to RMB 100,000 for a 100kW system).

[0099] (2) Significantly reduced startup time Medium-temperature heat exchangers reduce start-up time from 150-180 minutes to 90-120 minutes by preheating the inlet airflow with waste heat, a reduction of 30%. Figure 2 As shown. Figure 2 The startup time comparison chart shows that the startup time for a 1kW fuel cell stack is 90 minutes (compared to 150 minutes for a traditional fuel cell stack under the same conditions), the startup time for a 10kW fuel cell stack is 110 minutes (compared to 170 minutes for a traditional fuel cell stack under the same conditions), and the startup time for a 500kW fuel cell stack is 120 minutes (compared to 180 minutes for a traditional fuel cell stack under the same conditions). Traditional systems consume 5kWh~20kWh of energy during startup (RMB 30 / start~120 / start), while the fuel cell stack system in this application reduces this to 2kWh~15kWh (RMB 12 / start~90 / start), saving RMB 18~30 per startup. A 100kW system can be started once daily, resulting in annual startup cost savings of approximately RMB 6000~10000. This improves the response speed of SOFC systems in emergency power generation and mobile power (ships, trains), increasing scenario adaptability by 50%.

[0100] (3) The compact design reduces the system size and cost. Embedded microchannel medium-temperature heat exchangers (such as...) Figure 1 This eliminates the need for external components and reduces the size of the fuel cell stack system by 30% (e.g., a 1kW fuel cell stack system from 0.05m). 3 Reduced to 0.035m 3 The weight was reduced by 20% (from 50kg to 40kg). Figure 1The cross-sectional diagram illustrates the compact integration of the microchannel and the fuel cell stack. Manufacturing costs are reduced by 40% through additive manufacturing, with the cost per module decreasing from RMB 1,000-1,500 to RMB 250-400. The total cost of a 100kW system is reduced from RMB 2 million to RMB 1.4 million, and the payback period is shortened from 5 years to 3-4 years. This application also reduces site rental costs (e.g., approximately RMB 5,000 / year for a 100kW system) and transportation costs (reduced by 20%, approximately RMB 10,000), making it suitable for space-constrained scenarios such as urban distributed energy stations and significantly enhancing market competitiveness.

[0101] (4) Enhanced the durability and reliability of the fuel cell stack system This application reduces thermal stress by 50% (from 100 MPa to 50 MPa) by lowering the temperature gradient (40°C~60°C in this application, compared to 180°C~200°C in conventional fuel cell stack systems), extending the lifespan from 5000~8000 hours to 15000~20000 hours. Figure 3 As shown in (b), the temperature gradient curve verifies that the maximum temperature difference of the stack system in this application is 50°C. The durability test (2000 hours, 760°C) shows a power decay of 1.8%, and the microchannel coating shows no peeling. The maintenance frequency is reduced from once a year to once every two years, and the maintenance cost of a 100kW system is reduced from RMB 50,000 / year to RMB 25,000 / year, saving 50%. Furthermore, the medium-temperature heat exchanger can be quickly replaced (<2 hours, costing approximately RMB 500 / time), further improving reliability and making it suitable for industrial power plants and combined heat and power (CHP) scenarios.

[0102] (5) It has environmental benefits and fuel flexibility. This application utilizes efficient heat recovery to reduce fuel consumption, thereby reducing CO2 emissions by approximately 15% (0.1 kg reduction per kW·h, 8000 kg reduction per year for a 100kW system, and approximately 20,000 RMB in carbon trading revenue). The system is compatible with various fuels such as hydrogen, methane, ammonia, and biogas. Figure 2 It was also verified that the energy efficiency of the ammonia gas condition was improved by 10.5%, and the energy efficiency of the biogas condition was improved by 11%. The medium-temperature preheating optimized the reforming efficiency by 5%~10%, and the energy consumption of the reformer was reduced by about 200 yuan / year / kW. Figure 4 This demonstrates a 40% improvement in heat transfer coefficient and a low pressure drop (<5 kPa), ensuring the efficient operation of the fuel cell stack system described in this application. Furthermore, the fuel flexibility of this application supports the integration of renewable energy and contributes to carbon neutrality, thereby increasing green energy market coverage.

[0103] (6) It has wide applicability to various application scenarios The medium-temperature heat exchanger and single-cell unit of this application adopt a modular design, which can support the use of fuel cell stack systems with a power range of 0.5kW to 500kW, and can be applied to portable power supplies, industrial combined heat and power, and stationary power plants. Figure 2 and Figure 3 The performance advantages across multiple power scenarios were verified, and stability was confirmed through environmental testing (-30°C to 60°C, humidity 0~95%). A 100kW system generates 800,000 kWh annually (electricity price 0.8 yuan / kWh), generating revenue of 640,000 yuan, with comprehensive costs of approximately 400,000 yuan, resulting in an annual net profit of 240,000 yuan. Compared to traditional systems, scenario adaptability is improved by 50%, market coverage reaches 85%, significantly enhancing commercial value.

[0104] While specific embodiments of this application have been described in detail, this should not be construed as limiting the scope of protection of this application. Various modifications and variations that can be made by those skilled in the art without inventive effort within the scope described in the claims still fall within the scope of protection of this application.

Claims

1. A SOFC fuel cell stack system with an integrated medium-temperature heat exchanger, characterized in that, include: Several stacked single-cell cells; A connector separating each of the individual battery cells; An intermediate-temperature heat exchanger embedded in the connector or stacked with the single-cell unit can recover waste heat from the electrochemical reaction and preheat the incoming airflow to a temperature of 350°C to 600°C; wherein... The medium-temperature heat exchanger is equipped with several parallel microchannels through laser micromachining or additive manufacturing. The microchannels are made of nickel-based alloys or ceramics, and the inner surface of the microchannels is coated with an anti-oxidation coating.

2. The SOFC stack system with integrated medium-temperature heat exchanger according to claim 1, characterized in that, The microchannel wall thickness is 0.08mm~0.15mm, and the anti-oxidation coating is an alumina coating with a thickness of 4μm~6μm or a zirconium oxide coating with a thickness of 2nm~3nm.

3. The SOFC stack system with integrated medium-temperature heat exchanger according to claim 1, characterized in that, The microchannels have a hydraulic diameter of 0.4 mm to 0.8 mm, a channel spacing of 0.2 mm to 0.4 mm, and a surface area to volume ratio of 1000 m². 2 / m 3 ~1300m 2 / m 3 .

4. The SOFC stack system with integrated medium-temperature heat exchanger according to claim 1, characterized in that, The number of microchannels is 150 to 800, and the length of the microchannels is 40 mm to 120 mm.

5. The SOFC stack system with integrated medium-temperature heat exchanger according to claim 1, characterized in that, The medium-temperature heat exchanger uses a counter-current or cross-flow method to exchange heat between waste heat and incoming airflow. The incoming airflow includes fuel and air, and the fuel includes hydrogen, methane, ammonia, or biogas.

6. The SOFC stack system with integrated medium-temperature heat exchanger according to claim 1, characterized in that, The microchannel density in the core region of the SOFC stack is 5 channels / cm. 2 ~6 strips / cm 2 The microchannel density in the edge region of the SOFC stack is 3 channels / cm. 2 ~4 strips / cm 2 .

7. The SOFC stack system with integrated medium-temperature heat exchanger according to claim 6, characterized in that, The reaction temperature in the core area is 600℃~800℃, and the microchannels in the core area recover waste heat from the electrochemical reaction and preheat the incoming gas flow to a temperature of 500℃~550℃. The reaction temperature in the edge region is 400℃~600℃, and the microchannels in the edge region recover waste heat from the electrochemical reaction and preheat the incoming gas flow to a temperature of 400℃~450℃.

8. The SOFC stack system with integrated medium-temperature heat exchanger according to claim 1, characterized in that, The inner wall of the microchannel is provided with a microrib array or a corrugated wall. The height of the microrib array is 0.04mm~0.06mm and the spacing is 0.15mm~0.25mm. The amplitude of the corrugated wall is 0.08mm~0.12mm and the period is 0.4mm~0.6mm.

9. The SOFC stack system with integrated medium-temperature heat exchanger according to claim 1, characterized in that, The medium-temperature heat exchanger is connected to the connector by vacuum brazing or bonding; wherein the brazing filler metal is Ni-Cr-B, the vacuum brazing temperature is 950℃~1000℃, and the vacuum brazing pressure is <10. -6 Pa.

10. The SOFC stack system with integrated medium-temperature heat exchanger according to claim 9, characterized in that, The adhesive used for bonding is a ceramic adhesive, and the curing temperature of the ceramic adhesive is 1100℃~1200℃.

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