Solid oxide fuel cell co-production system based on ammonia fuel

Abstract

The invention relates to a solid oxide fuel cell co-production system based on ammonia fuel, which comprises a solid oxide fuel cell, an aftercombustion chamber, a gas turbine and a waste heat boiler, an anode inlet of the solid oxide fuel cell is connected with an ammonia fuel inlet pipe, and a cathode inlet of the solid oxide fuel cell is connected with an air inlet pipe. A fuel compressor and a fuel preheater are arranged on the ammonia fuel inlet pipe, and an air compressor and an air preheater are arranged on the air inlet pipe; a cathode outlet and an anode outlet of the solid oxide fuel cell are connected to an inlet of the aftercombustion chamber, a flue gas outlet of the aftercombustion chamber is connected to the gas turbine, and an exhaust port of the gas turbine is sequentially connected with the fuel preheater, the air preheater and the waste heat boiler. The solid oxide fuel cell provided by the invention takes ammonia fuel as a core, is convenient to store and transport and high in operation flexibility, realizes a multi-energy co-production value, and has the characteristics of low cost, low pollution and high performance.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a solid oxide fuel cell co-production system based on ammonia fuel. Background Art

[0002] The solid oxide fuel cell (SOFC) co-production system realizes efficient power generation and waste heat utilization through high-temperature electrochemical reactions, and the current technology development has entered the stage of engineering verification. Traditional systems use hydrogen, natural gas or biogas as the mainstream fuels, and rely on external reforming devices to convert carbon-based fuels into hydrogen-rich gases, but they face multiple constraints: hydrogen storage and transportation require cryogenic cooling at -253°C or high pressure of 70 MPa, with high costs and poor safety; the natural gas reforming process generates 10-15% CO2 emissions, and the energy consumption of carbon capture accounts for 8% of the total system output; biogas requires a complex pretreatment unit due to large fluctuations in composition (CH4 content 40-70%). Technical optimization mainly focuses on three aspects: First, the upgrade of the stack materials, using scandium-doped zirconia electrolyte (ScSZ) to reduce the operating temperature from 1000°C to 750-850°C, and at the same time developing anti-carbon deposition anodes (such as Ni-GDC); second, the innovation of thermal management, using 800°C tail gas to drive a micro gas turbine or an organic Rankine cycle, and the demonstration project of Kyocera Corporation in Japan achieved a power generation efficiency of 68% and a heat supply efficiency of 17%; third, the simplification of system integration, improving the fuel utilization rate to 90% through anode off-gas recirculation (AOR), but catalyst sintering (Ni particle coarsening rate > 30% per thousand hours) and sealing material aging (leakage rate > 3% after 50,000 thermal cycles of glass-ceramic joints) are still the life bottlenecks.

[0003] In the context of limited fuel selection, ammonia fuel has become a breakthrough direction due to its unique physical and chemical properties. Ammonia (NH3), as a hydrogen energy carrier, has a volumetric hydrogen storage density of 108 kg-H2 / m³, which is 1.5 times that of liquid hydrogen, and can be liquefied at -33°C under normal pressure, and can directly utilize the existing LPG infrastructure for transportation. 120 ports around the world are already equipped with liquid ammonia loading and unloading capabilities. Technical breakthroughs are reflected in: low-temperature catalytic decomposition, the Fe-Co dual-atom catalyst reduces the ammonia cracking temperature from 800°C to 450°C, and the hydrogen production rate > 99%; direct electrochemical oxidation, the LaSrCoFeO3-δ anode achieves a power density of 0.18 W / cm² at 700°C, and the efficiency loss compared to traditional fuel systems is only 5%; emission control optimization, the reducing atmosphere of SOFC inhibits the generation of NOx, and combined with tail gas SCR denitrification, the emissions < 5 ppm. Compared with traditional fuels, the ammonia-SOFC co-production system does not require carbon capture equipment, the carbon emissions in the whole life cycle are reduced by 92%, and the fuel cost is only 1 / 3 of that of hydrogen. Although ammonia fuel has a high ignition energy and toxicity risk, by avoiding the combustion link through the electrochemical path, its energy density (18.6 MJ / kg) is comparable to that of methanol, and its safety and economy are more suitable for scenarios such as ships and islands, becoming a key fulcrum for the zero-carbon energy transition.

[0004] In summary, developing a combined heat and power system based on ammonia fuel for solid oxide fuel cells has important research value and significance. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a compact, low-cost, low-pollution, and high-performance combined heat and power system based on ammonia fuel for solid oxide fuel cells.

[0006] The present invention is implemented as follows: A combined heat and power system based on ammonia fuel for solid oxide fuel cells includes a solid oxide fuel cell, a post-combustion chamber, a gas turbine, and a waste heat boiler. The anode inlet of the solid oxide fuel cell is connected to an ammonia fuel inlet pipe, and the cathode inlet of the solid oxide fuel cell is connected to an air inlet pipe. A fuel compressor and a fuel preheater are provided on the ammonia fuel inlet pipe, and an air compressor and an air preheater are provided on the air inlet pipe. The cathode outlet and the anode outlet of the solid oxide fuel cell are both connected to the inlet of the post-combustion chamber. The flue gas outlet of the post-combustion chamber is connected to the gas turbine, and the exhaust port of the gas turbine is sequentially connected to the fuel preheater, the air preheater, and the waste heat boiler.

[0007] Further, it also includes a first heat exchanger, a second heat exchanger, a third heat exchanger, a steam turbine, and a circulation pump. The waste heat boiler, the steam turbine, the second heat exchanger, the third heat exchanger, and the circulation pump are sequentially connected to form a steam circulation pipeline.

[0008] Further, the tail gas outlet of the waste heat boiler is connected to the first heat exchanger.

[0009] Further, it also includes a lithium bromide absorption refrigeration unit that uses the second heat exchanger as a heat source.

[0010] Further, the lithium bromide absorption refrigeration unit includes a generator, a condenser, a first throttle valve, an evaporator, a second throttle valve, a solution heat exchanger, a mixer, an absorber, and a solution pump. The generator, the condenser, the first throttle valve, the evaporator, the mixer, the absorber, the solution pump, and the solution heat exchanger are sequentially connected to form a refrigeration cycle pipeline.

[0011] Further, the generator, the solution heat exchanger, the second throttle valve, and the mixer are also sequentially connected to form a lithium bromide solution diversion pipeline.

[0012] Compared with the prior art, the present invention has the following beneficial effects: The solid oxide fuel cell of the present invention takes ammonia fuel as the core, with convenient fuel storage and transportation, strong operation flexibility, realizing the value of combined heat and power production, and having the characteristics of low cost, low pollution, and high performance. It solves the problems of carbon deposition, efficiency, and emission bottlenecks in the combined heat and power system of solid oxide fuel cells, realizes system compactification, zero carbonization, and combined heat and power production, and provides an effective solution for shipping and off-grid power supply.

[0013] To make the objectives, technical solutions and advantages of the present invention more clearly understood, the following will further elaborate on the present invention through specific embodiments and related drawings. Description of the Drawings

[0014] Figure 1 It is a schematic diagram of the system structure of an embodiment of the present invention; Explanation of the reference numerals in the figure: 1 - Solid oxide fuel cell, 2 - Afterburner, 3 - Gas turbine, 4 - First heat exchanger, 5 - Steam turbine, 6 - Second heat exchanger, 7 - Third heat exchanger, 8 - Circulation pump, 9 - Waste heat boiler, 10 - Air compressor, 11 - Fuel compressor, 12 - Air preheater, 13 - Fuel preheater, 14 - Generator, 15 - Condenser, 16 - First throttle valve, 17 - Evaporator, 18 - Second throttle valve, 19 - Solution heat exchanger, 20 - Mixer, 21 - Absorber, 22 - Solution pump. Detailed Embodiments

[0015] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0016] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0017] Such as Figure 1As shown in the figure, a combined heat and power system based on ammonia fuel solid oxide fuel cell includes a solid oxide fuel cell 1, a post-combustion chamber 2, a gas turbine 3 and a waste heat boiler 9. The anode inlet of the solid oxide fuel cell 1 is connected with an ammonia fuel inlet pipe, and the cathode inlet of the solid oxide fuel cell is connected with an air inlet pipe. A fuel compressor 11 and a fuel preheater 13 are provided on the ammonia fuel inlet pipe, and an air compressor 10 and an air preheater 12 are provided on the air inlet pipe. The cathode outlet and the anode outlet of the solid oxide fuel cell are both connected to the inlet of the post-combustion chamber 2. The flue gas outlet of the post-combustion chamber 2 is connected to the gas turbine 3. The exhaust port of the gas turbine is connected to the fuel preheater 13, the air preheater 12 and the waste heat boiler 9 in sequence through an exhaust gas recovery pipeline. The air inlet pipe is connected to the inlet and outlet of the heated medium of the air preheater 12, and the ammonia fuel inlet pipe is connected to the inlet and outlet of the heated medium of the fuel preheater 13. The exhaust gas recovery pipeline is connected to the inlet and outlet of the heat medium of the air preheater 12 and the fuel preheater 13.

[0018] In this system, after the ammonia fuel is compressed to the operating pressure of the solid oxide fuel cell 1 by the fuel compressor 11, it enters the fuel preheater 13 for preheating, and then enters the SOFC as anode fuel. The air is pressurized and preheated by the air compressor 10 and the air preheater 12 and then enters the cathode of the SOFC as cathode gas. The preheated ammonia fuel first undergoes an ammonia decomposition reaction inside the SOFC to generate hydrogen and nitrogen. The generated hydrogen reacts electrochemically with the oxygen in the air inside the SOFC to generate direct current, which is then converted into alternating current by a DC-AC converter for output. The unreacted fuel and air enter the post-combustion chamber 2 for full combustion. The high-pressure gas with increased temperature after full combustion enters the gas turbine 3 for expansion work, converting the thermal energy of the high-pressure and high-temperature gas into mechanical energy and then driving the generator to output electric power outward. The turbine exhaust exchanges heat through the fuel preheater and the air preheater in sequence and then enters the waste heat boiler 9, releases the remaining heat and is discharged. Since the products of the ammonia fuel SOFC system are only nitrogen and water, it will not cause pollution to the environment.

[0019] In this embodiment, it further includes a first heat exchanger 4, a second heat exchanger 6, a third heat exchanger 7, a steam turbine 5 and a circulation pump 8. The waste heat boiler 9, the steam turbine 5, the second heat exchanger 6, the third heat exchanger 7 and the circulation pump 8 are connected in sequence to form a steam circulation pipeline. The steam circulation pipeline is connected to the inlet and outlet of the heat medium of the second heat exchanger 6 and the third heat exchanger 7. The water pressurized by the circulation pump 22 absorbs heat in the waste heat boiler 9 and is converted into high-pressure steam. Subsequently, the high-pressure steam enters the steam turbine 5 for work. The heat of the exhaust is recovered by the second heat exchanger and the third heat exchanger and serves as the heat source for the lithium bromide absorption refrigeration unit and domestic hot water respectively, outputting cold and heat. The cooled water enters the circulation pump for pressurization to prepare for the next steam cycle.

[0020] In this embodiment, the tail gas outlet of the waste heat boiler 9 is connected to the first heat exchanger 4.

[0021] In this embodiment, it further includes a lithium bromide absorption refrigeration unit that uses the second heat exchanger 6 as a heat source.

[0022] In this embodiment, the lithium bromide absorption refrigeration unit includes a generator 14, a condenser 15, a first throttle valve 16, an evaporator 17, a second throttle valve 18, a solution heat exchanger 19, a mixer 20, an absorber 21, and a solution pump 22; the generator 14, the condenser 15, the first throttle valve 16, the evaporator 17, the mixer 20, the absorber 21, the solution pump 22, and the solution heat exchanger 19 are connected in sequence to form a refrigeration cycle pipeline; the lithium bromide solution shunt pipeline is connected to the inlet and outlet of the hot medium of the solution heat exchanger 19.

[0023] In this embodiment, the generator 14, the solution heat exchanger 19, the second throttle valve 18, and the mixer 20 are also connected in sequence to form a lithium bromide solution shunt pipeline, and the lithium bromide solution shunt pipeline is connected to the inlet and outlet of the medium to be heated of the solution heat exchanger 19.

[0024] The operation process of the ammonia fuel solid oxide fuel cell combined production system of the invention starts with liquid ammonia being pressurized, heated, and then injected into the SOFC anode chamber. Ammonia cracking and electrochemical reactions are synchronously completed in the composite anode microchannels, outputting direct current electric energy and generating high-temperature tail gas; unreacted gases and excess oxygen at the cathode flow into the afterburner, and the discharged high-temperature gas drives a gas turbine to generate electricity. The exhaust gas of the gas turbine enters the waste heat boiler to generate superheated steam to drive a steam turbine to generate electricity. The boiler flue gas temperature is controlled below 120°C, and the heat recovery efficiency reaches 85%. During operation, a simplified control strategy is adopted. By adjusting the liquid ammonia flow rate to match the load demand of the steam turbine operation, 70% of the waste heat is used for district heating (outputting 90°C hot water) in winter, and 30% is used to drive the steam turbine; in summer, 55% of the heat is preferentially allocated to the refrigerator to produce 7°C chilled water, and the remaining 45% is used for power generation; in the transition season, a model predictive control algorithm is used to optimize the cold, heat, and electricity ratio in real time to ensure that the comprehensive energy utilization rate > 82% to meet the load demands of different occasions.

[0025] The invention solves the problems of carbon deposition, efficiency, and emission bottlenecks in the solid oxide fuel cell combined production system, realizes system compactification, zero carbonization, and multi-energy combined production, and provides an effective solution for shipping and off-grid power supply.

[0026] The ammonia solid oxide fuel cell combined production system of the invention takes ammonia fuel as the core and has the advantages of high efficiency, zero carbon, and multi-energy combined supply. Its technical advantages include: 1) Convenient fuel storage and transportation: The hydrogen storage density of liquid ammonia reaches 121 kg / m³, which is 1.5 times that of liquid hydrogen. Relying on a mature liquid ammonia storage and transportation system, it solves the problem of long-distance hydrogen transportation.

[0027] 2) Excellent energy efficiency: Through in-situ catalytic decomposition of ammonia at the anode (conversion rate > 99%) and cascaded utilization of the waste heat of the fuel cell stack (heat recovery rate > 85%), the comprehensive energy efficiency of the system breaks through 90%, which is more than 40% higher than that of traditional gas turbines.

[0028] 3) Strong operation flexibility: It supports multi-mode operation of pure ammonia and ammonia-hydrogen mixture, dynamically responds to load changes, and adapts to fluctuating scenarios such as off-grid and ships.

[0029] 4) Value of multi-energy co-production: It synchronously outputs electric energy (efficiency > 60%), domestic hot water and cooling capacity, meeting the energy coupling needs of industrial processes and living communities.

[0030] Its core applications include: 1) Shipping decarbonization. Replacing marine diesel engines to provide zero-carbon power for large ships, with a voyage of up to 10,000 nautical miles and a 30% reduction in fuel costs.

[0031] 2) Off-grid power supply. Providing integrated power-heat-cooling supply for remote islands and mining areas, getting rid of dependence on the power grid.

[0032] 3) Smart energy in industrial parks. Through waste heat-driven refrigeration or steam co-production, the comprehensive energy efficiency of the park is increased by 50%.

[0033] 4) Green hydrogen economic hub. Using off-peak electricity prices to electrolyze ammonia to smooth out the fluctuations of renewable energy and build a "wind-solar-ammonia-electricity" cross-seasonal energy storage network.

[0034] The process of the lithium bromide absorption refrigeration unit is as follows: First, after the lithium bromide aqueous solution is heated by a low-grade heat source from an external source, some water in the lithium bromide aqueous solution evaporates to form water vapor, and at the same time, the concentration of the lithium bromide aqueous solution becomes higher. The vaporized water vapor enters the condenser 15. In the condenser 15, the water vapor is condensed into high-pressure and low-temperature liquid water by the action of condensed water, releasing the condensation heat; the liquid water enters the evaporator 17 after being depressurized by the throttle valve 16. In the evaporator 17, the low-temperature and low-pressure liquid water rapidly expands and vaporizes, and at the same time, it absorbs a large amount of heat from the refrigerant water to form saturated water vapor. The cooled refrigerant water provides cooling capacity for the cold user; the low-temperature water vapor formed in the evaporator 17 then enters the absorber 21 and mixes with the concentrated lithium bromide solution flowing out of the generator 14; the high-concentration lithium bromide aqueous solution in the generator 14 passes through the solution heat exchanger 19, is heated for the dilute lithium bromide solution and then enters the absorber 21 through the throttle valve 18 to mix with the saturated water vapor at the evaporator outlet; in the absorber 21, the saturated water vapor mixes with the concentrated lithium bromide solution, and the concentration of the lithium bromide aqueous solution is further reduced. Then, it is heated by the solution heat exchanger 19 and enters the generator to prepare for the next refrigeration cycle.

[0035] For any of the technical solutions disclosed in the present invention above, unless otherwise stated, if it discloses a numerical range, then the disclosed numerical range is a preferred numerical range. Any person skilled in the art should understand that the preferred numerical range is only the numerical values with obvious technical effects or representativeness among many implementable numerical values. Since there are too many numerical values to enumerate, the present invention only discloses some numerical values to illustrate the technical solutions of the present invention, and moreover, the above-listed numerical values should not constitute a limitation on the protection scope of the present invention.

[0036] If the present invention discloses or involves components or structural members that are fixedly connected to each other, then, unless otherwise stated, the fixed connection can be understood as: a detachable fixed connection (for example, connected by bolts or screws), or it can also be understood as: a non-detachable fixed connection (for example, riveting, welding). Of course, the components fixedly connected to each other can also be replaced by an integral structure (for example, manufactured by an integral casting process) (except when it is obviously impossible to adopt the integral forming process).

[0037] In addition, for the terms used to represent the positional relationship or shape in any of the technical solutions disclosed in the present invention above, unless otherwise stated, their meanings include states or shapes that are approximate, similar, or close to them.

[0038] Any component provided by the present invention can either be assembled from multiple separate components or be a single component manufactured by an integral forming process.

[0039] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention in any other form. Any person skilled in the relevant art may use the technical content disclosed above to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A solid oxide fuel cell cogeneration system based on ammonia fuel, characterized in that: It includes a solid oxide fuel cell, an afterburner, a gas turbine and a waste heat boiler. The anode inlet of the solid oxide fuel cell is connected to an ammonia fuel inlet pipe, and the cathode inlet of the solid oxide fuel cell is connected to an air inlet pipe. The ammonia fuel inlet pipe is provided with a fuel compressor and a fuel preheater, and the air inlet pipe is provided with an air compressor and an air preheater. The cathode outlet and the anode outlet of the solid oxide fuel cell are both connected to the inlet of the afterburner, and the flue gas outlet of the afterburner is connected to the gas turbine. The exhaust port of the gas turbine is connected to the fuel preheater, the air preheater and the waste heat boiler in sequence.

2. The solid oxide fuel cell cogeneration system based on ammonia fuel according to claim 1, characterized in that: It also includes a first heat exchanger, a second heat exchanger, a third heat exchanger, a steam turbine and a circulating pump. The waste heat boiler, the steam turbine, the second heat exchanger, the third heat exchanger and the circulating pump are connected in sequence to form a steam circulation pipeline.

3. The solid oxide fuel cell cogeneration system based on ammonia fuel according to claim 2, characterized in that: The tail gas outlet of the waste heat boiler is connected to the first heat exchanger.

4. The solid oxide fuel cell cogeneration system based on ammonia fuel according to claim 1, characterized in that: It also includes a lithium bromide absorption refrigeration unit that uses a second heat exchanger to provide a heat source.

5. The solid oxide fuel cell cogeneration system based on ammonia fuel according to claim 5, characterized in that: The lithium bromide absorption refrigeration unit comprises a generator, a condenser, a first throttle valve, an evaporator, a second throttle valve, a solution heat exchanger, a mixer, an absorber and a solution pump; the generator, condenser, the first throttle valve, the evaporator, the mixer, the absorber, the solution pump and the solution heat exchanger are connected in sequence to form a refrigeration cycle pipeline.

6. The solid oxide fuel cell cogeneration system based on ammonia fuel according to claim 6, characterized in that: The generator, the solution heat exchanger, the second throttle valve and the mixer are also connected in sequence to form a lithium bromide solution diversion pipeline.

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