Low-temperature direct ammonia fuel cell system

Abstract

The present invention belongs to the field of fuel cell systems, specifically a low-temperature direct ammonia fuel cell system. The system mainly includes a fuel tank, an anode fuel feed subsystem, a cathode fuel feed subsystem, an exhaust gas processor and a fuel cell stack. The fuel tank is a closed fuel tank, which contains one of liquid ammonia, ammonia gas, an ammonia solution or an ammonia-alkali mixture, and is connected to the anode fuel subsystem through a pipeline. The anode fuel subsystem mainly includes a metering pump, a mixer, a fuel heating pipeline and a gas-liquid separator; the cathode fuel feed subsystem mainly includes a compressor, a humidifier, and an expander; the exhaust gas processor has a built-in solid absorbent. The system of the present invention simplifies the system structure, effectively humidifies, improves the utilization rate of ammonia fuel, enhances the performance of the fuel cell, and can operate under a certain operating pressure.

Description

Technical Field

[0001] The present invention belongs to the field of fuel cell systems, and specifically provides a low-temperature direct ammonia fuel cell system in a fuel cell system. Background Art

[0002] A fuel cell is a device that converts chemical energy into electrical energy. Fuel cells can be categorized into various types based on their reaction principles, including proton exchange membrane fuel cells, alkaline anion membrane fuel cells, solid oxide fuel cells, and molten carbonate fuel cells. Among alkaline anion membrane fuel cells, low-temperature direct ammonia fuel cells (DAMFCs), which use liquid ammonia or ammonia gas as fuel, offer advantages such as fast startup and environmental friendliness, making them a promising new fuel cell technology. Currently, battery-powered power systems suffer from short operating times, long charging times, and poor safety. Hydrogen fuel cell-powered power systems are also beginning to enter the market, but the storage and transportation of hydrogen restrict their widespread application. In contrast, DAMFCs overcome the shortcomings of both batteries and hydrogen fuel cells, offering advantages in lightweight applications such as drones, bicycles, uninterruptible power supplies, and mobile power supplies.

[0003] Although low-temperature fuel cells have many advantages, they also have problems such as slow ammonia oxidation kinetics, low ammonia fuel utilization, and easy cathode flooding. Therefore, research on low-temperature fuel cells is still needed to obtain an ammonia fuel cell system that solves the above technical problems. This is of great significance to the development of low-temperature fuel cells. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a low-temperature direct ammonia fuel cell system with a reasonable design and rapid heating. Two low-temperature direct ammonia fuel cell system designs are provided for different anode feed fuels. The main components used in the system include a fuel tank, an anode fuel feed subsystem, a cathode fuel feed subsystem, an exhaust gas processor and a stack. The fuel tank is completely sealed, and a high-concentration ammonia fuel is stored in the tank, which can be at least one of liquid ammonia, ammonia gas, an ammonia solution or other ammonia-alkali mixture. The fuel tank is connected to the anode fuel feed subsystem through a pipeline, and the anode fuel feed subsystem is connected to the anode inlet of the low-temperature direct ammonia fuel cell stack, and the anode outlet of the stack is connected to the anode fuel subsystem to form a loop. Air is connected to the cathode inlet of the stack through the cathode fuel feed subsystem, and the cathode outlet of the stack is connected to the cathode fuel cell subsystem to form a loop. The anode and cathode exhaust gases are respectively connected to the exhaust processor, and are discharged into the atmosphere after being treated by the exhaust processor.

[0005] The present invention specifically adopts the following technical solutions:

[0006] The present invention provides a low-temperature direct ammonia fuel cell system, which includes a fuel tank, an anode fuel feeding subsystem, a cathode fuel feeding subsystem, an exhaust gas processor and a fuel cell stack;

[0007] The anode fuel feeding subsystem includes a mixer, a fuel heating pipeline, an air condenser, and a gas-liquid separator; the fuel tank is connected to the mixer and the fuel heating pipeline in sequence, the fuel heating pipeline is connected to the anode inlet of the stack, the anode outlet of the stack is connected to the air condenser and the gas-liquid separator in sequence, the liquid output end of the gas-liquid separator is connected to the mixer, and the gas output end of the gas-liquid separator is connected to the back pressure regulator and the exhaust gas processor in sequence;

[0008] The cathode fuel feed subsystem includes a compressor, a humidifier, and an expander connected in sequence; the humidifier is connected to the cathode inlet of the fuel cell stack, and the cathode outlet of the fuel cell stack is connected in sequence to the expander and the tail gas processor; the tail gas processor is a completely enclosed structure, and a solid adsorbent is loaded inside to treat incompletely reacted ammonia fuel;

[0009] The fuel cell stack is a low-temperature direct ammonia fuel cell stack, and its structure is a bipolar plate fuel cell stack;

[0010] The fuel tank is used to directly store high-concentration ammonia fuel; the high-concentration ammonia fuel is at least one of liquid ammonia, ammonia gas, ammonia solution or ammonia-alkali mixture.

[0011] In the above technical solution, further, when the ammonia fuel is ammonia gas, the system also includes a heat exchanger, the low-temperature heat pipe inlet end of the heat exchanger is connected to the fuel tank, the high-temperature heat pipe inlet end is connected to the air condenser, the low-temperature heat pipe outlet end of the heat exchanger is connected to the mixer, and the high-temperature heat pipe outlet end is connected to the gas-liquid separator.

[0012] In the above technical solution, further, a pressure reducing valve is provided on the pipeline between the fuel tank and the heat exchanger; and a circulating pump is provided on the pipeline between the gas-liquid separator and the mixer.

[0013] In the above technical solution, further, a metering pump is provided on the pipeline between the fuel tank and the mixer, and the metering pump is one of a peristaltic pump, a gear pump, a centrifugal pump, a screw pump, a pneumatic diaphragm pump, and a spiral pump.

[0014] In the above technical solution, further, the fuel tank is a closed structure; when liquid ammonia or ammonia gas is used as fuel, the fuel tank is made of stainless steel or aluminum, and the design pressure is ≥1MPa; when ammonia solution or ammonia-alkali mixture is used as fuel, the fuel tank is made of polyethylene, polypropylene, polyethylene terephthalate or aluminum, and is stored at room temperature and pressure.

[0015] In the above technical solution, further, the fuel heating pipeline is a stainless steel pipeline, a tetrafluoroethylene pipeline, a polyvinylidene fluoride pipeline, a polyethylene pipeline, or a polypropylene pipeline; the heating method uses a heating tape or a heating rod placed outside the fuel heating pipeline for heating.

[0016] In the above technical solution, further, the mixer is one of a propeller stirrer, a turbine stirrer, a paddle stirrer, and a ribbon stirrer.

[0017] In the above technical solution, further, the compressor is one of piston type, screw type, scroll type, centrifugal type, axial flow type, and jet type; the expander is one of piston type and turbine type;

[0018] The humidifier is a humidification tank or a membrane humidifier.

[0019] In the above technical solution, further, the exhaust gas processor is internally loaded with a solid absorbent, and the solid absorbent is one of superphosphate, Prussian blue, silica gel, and activated carbon.

[0020] In the above technical solution, further, the low-temperature direct ammonia fuel cell stack is a bipolar plate type stack, and the bipolar plate material is composite graphite or metal.

[0021] Beneficial effects

[0022] (1) The low-temperature direct ammonia fuel cell system provided by the present invention adds a condenser and a heat exchange device after the outlet of the anode side stack, uses the heat exchange device and the ammonia raw material to cool the unreacted ammonia fuel discharged from the anode, and condenses it into liquid for recovery. The product nitrogen and liquid ammonia fuel are separated in the gas-liquid separator device, and the unreacted ammonia fuel is mixed with the introduced ammonia raw material through a mixer and then introduced into the stack, thereby solving the problem that the high-concentration ammonia fuel system has a high energy density but a low ammonia fuel utilization rate, thereby improving the ammonia fuel utilization rate.

[0023] (2) The system provided by the present invention increases the operating pressure on the cathode side by using a combination of a compressor and an expander on the cathode side, which is beneficial to the mass transfer of oxygen, improves the oxygen reduction kinetics, and solves the problem of cathode flooding caused by ammonia fuel penetrating into the cathode, which is not conducive to oxygen mass transfer; by arranging a pressure regulating valve at the tail end of the anode side, the operating pressure on the anode side is increased, which is beneficial for the ammonia fuel to reach the catalyst surface and improves the ammonia oxidation kinetics.

[0024] (3) The system provided by the present invention avoids the cooling effect caused by the low-temperature liquid ammonia fuel entering the fuel cell stack by heating the anode feed line, thereby increasing the operating temperature of the fuel cell stack, ensuring a low overpotential in the anode ammonia oxidation kinetic process, and improving the performance of the fuel cell.

[0025] (4) In the system provided by the present invention, the water discharged from the cathode of the fuel cell stack can be used as humidification water for the membrane humidifier; the unreacted air discharged from the cathode outlet passes through the air expander and enters the tail exhaust device, and the gas separated from the gas-liquid separator enters the tail exhaust device after being decompressed, thereby making full use of the functions of each component and simplifying the system structure to a certain extent.

[0026] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the following preferred embodiments are specifically cited and illustrated in detail as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the structure of a low-temperature direct ammonia fuel cell system using liquid ammonia as the anode feed fuel in Example 1;

[0028] Figure 2 Schematic diagram of the structure of a low-temperature direct ammonia fuel cell system using ammonia water or ammonia-alkali mixed solution as the anode feed fuel in Example 2;

[0029] In the figure, 1. air, 2. air compressor, 3. air expander, 4. membrane humidifier, 5. fuel stack cathode, 6. fuel stack anode, 7. exhaust water, 8. fuel tank, 9. pressure reducing valve, 10. heat exchanger, 11. gas-liquid separator, 12. circulation pump, 13. mixer, 14. fuel heating pipeline, 15. air condenser, 16. back pressure regulator, 17. exhaust gas processor, 18. exhaust gas, 19. water, 20. metering pump. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0031] Example 1

[0032] A low-temperature direct ammonia fuel cell system comprises a fuel tank 8, an anode fuel feeding subsystem, a cathode fuel feeding subsystem, an exhaust gas processor 17 and a fuel cell stack; liquid ammonia is stored in the fuel tank.

[0033] The anode fuel feeding subsystem includes a heat exchanger 10, a mixer 13, a fuel heating pipeline 14, an air condenser 15, and a gas-liquid separator 11; the fuel tank is connected to the low-temperature heat pipe inlet of the heat exchanger through a pipeline, the low-temperature heat pipe outlet of the heat exchanger is connected to the mixer, the mixer is connected to the fuel heating pipeline, the fuel heating pipeline is connected to the anode inlet of the stack, the anode outlet of the stack is connected to the air condenser through a pipeline, the air condenser is connected to the high-temperature heat pipe inlet of the heat exchanger, the high-temperature heat pipe outlet is connected to the gas-liquid separator, the liquid output end of the gas-liquid separator is connected to the mixer, and the gas output end of the gas-liquid separator is connected to the back pressure regulator 16 and the exhaust gas processor 17 in sequence through a pipeline; a pressure reducing valve 9 is set on the pipeline between the fuel tank 8 and the heat exchanger 10; a circulation pump 12 is set on the pipeline of the gas-liquid separator and the mixer.

[0034] The cathode fuel feed subsystem includes an air compressor 2, a humidifier 4, and an expander 3, which are connected in sequence through pipelines; the humidifier is connected to the cathode inlet of the fuel cell stack, and the cathode outlet of the fuel cell stack is connected in sequence to the expander and the exhaust gas processor; the exhaust gas processor is a completely enclosed structure, and a solid adsorbent is loaded inside to treat incompletely reacted ammonia fuel.

[0035] The stack is a low-temperature direct ammonia fuel cell stack, constructed with bipolar plates made of composite graphite or metal. On the cathode side, air 1 is passed through an air compressor 2 and then connected to a membrane humidifier 4. After humidification, the air is then connected to the stack's cathode inlet. Unreacted air and water in the stack (diffused from the anode) flow out of the stack's cathode outlet, pass through the membrane humidifier 4, and are then connected to an air expander 3. This is then connected to an exhaust gas processor 17 and discharged into the atmosphere. The exhaust consists of discharged water 7 and exhaust gas 18.

[0036] On the anode side, compressed liquid ammonia is placed in the fuel tank 8, and is reduced to a certain pressure by the pressure reducing valve 9, becoming liquid ammonia or ammonia gas. It is passed into the heat exchanger 10 for preheating and then connected to the mixer 13. After being evenly mixed with the unreacted ammonia fuel at the anode in the mixer, it is connected to the anode inlet of the stack through the fuel heating pipeline 14. The unreacted ammonia fuel flows out of the anode outlet of the stack and is connected to the air condenser 15. After cooling, it is passed into the heat exchanger 10 and heat exchanged with the ammonia fuel again, and then connected to the gas-liquid separator 11. The liquid coming out of the gas-liquid separator 11 is connected to the circulation pump 12 and then passed into the mixer 13 to be mixed with the ammonia fuel and enter the stack for reaction again. The gas coming out of the gas-liquid separator 11 is connected to the back pressure regulator 16, and after being reduced in pressure, it is passed into the exhaust gas processor 17 to absorb the unreacted ammonia fuel. The exhaust gas processor discharges water 7 and gas 18.

[0037] In this embodiment, the fuel heating pipeline 14 is heated by a heating tape, but other heating methods may also be used to heat the anode fuel.

[0038] In this embodiment, the exhaust gas processor 17 is built with a solid adsorbent, and one of superphosphate, Prussian blue, silica gel, and activated carbon can be used. In this embodiment, superphosphate is used to achieve absorption of ammonia and water.

[0039] In this embodiment, the mixer is a propeller stirrer, the expander is a piston expander, and the air compressor is a piston air compressor.

[0040] Example 2

[0041] A low-temperature direct ammonia fuel cell system includes a fuel tank 8, an anode fuel feeding subsystem, a cathode fuel feeding subsystem, an exhaust gas processor 17 and a fuel cell stack; the fuel tank directly stores ammonia water or an ammonia-alkali mixture.

[0042] The anode fuel feeding subsystem includes a mixer 13, a fuel heating pipeline 14, an air condenser 15, and a gas-liquid separator 11; the fuel tank is connected to the mixer and the fuel heating pipeline in sequence through pipelines, the fuel heating pipeline is connected to the anode inlet of the stack, the anode outlet of the stack is connected to the air condenser and the gas-liquid separator in sequence through pipelines, the liquid output end of the gas-liquid separator is connected to the mixer, and the gas output end of the gas-liquid separator is connected to the back pressure regulator 16 and the exhaust gas processor in sequence through pipelines; a metering pump 20 is set on the pipeline between the fuel tank and the mixer.

[0043] The cathode fuel feed subsystem includes an air compressor 2, a humidifier 4, and an air expander 3, which are connected in sequence. The humidifier is connected to the cathode inlet of the stack, and the cathode outlet of the stack is connected in sequence to the expander and the tail gas processor. The tail gas processor is a completely enclosed structure and is loaded with a solid adsorbent to treat incompletely reacted ammonia fuel.

[0044] The fuel cell stack is a low-temperature direct ammonia fuel cell stack, and its structure is a bipolar plate fuel cell stack.

[0045] On the cathode side, air 1 passes into the air compressor 2 and is then connected to the membrane humidifier 4. After humidifying the air, it is connected to the cathode inlet of the fuel cell stack. The unreacted air and water in the fuel cell stack (diffused from the anode) flow out from the cathode outlet of the fuel cell stack, pass through the membrane humidifier 4, and are then connected to the air expander 3. After the gas is decompressed, it is connected to the exhaust gas processor 17, which absorbs the unreacted ammonia and is discharged into the atmosphere. The discharges include discharged water 7 and discharged gas 18.

[0046] On the anode side, ammonia water or ammonia-alkali mixture is placed in the fuel tank 8, connected to the mixer 13 through the metering pump 20, and after being evenly mixed, it is connected to the anode inlet of the stack through the heating pipe 14. The unreacted ammonia fuel flows out from the anode outlet of the stack and is cooled through the air condenser 15 and connected to the gas-liquid separator 11. The liquid coming out of the gas-liquid separator 11 is connected to the mixer 13 and mixed with the ammonia fuel to enter the stack again for reaction. The gas coming out of the gas-liquid separator 11 is connected to the back pressure regulator 16, and the gas is depressurized and passed into the exhaust gas processor 17 to absorb the unreacted ammonia fuel.

[0047] In this embodiment, the fuel heating pipeline 14 is heated by a heating tape, but other heating methods may also be used to heat the anode fuel.

[0048] In this embodiment, the exhaust gas processor 17 is built with a solid adsorbent, which can use one of superphosphate, Prussian blue, silica gel, and activated carbon to absorb ammonia and water. In this embodiment, the metering pump is a peristaltic pump.

[0049] Anyone skilled in the art will be able to utilize the above-disclosed technical content to make many possible changes and modifications to the technical solution of the present invention, or to modify it into equivalent embodiments with equivalent changes, without departing from the scope of the technical solution of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention that do not depart from the content of the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A low-temperature direct ammonia fuel cell system, characterized in that: The system includes a fuel tank, an anode fuel feeding subsystem, a cathode fuel feeding subsystem, an exhaust gas processor, a fuel cell stack and a heat exchanger; The anode fuel feeding subsystem includes a mixer, a fuel heating pipeline, an air condenser, and a gas-liquid separator; the fuel tank is connected to the mixer and the fuel heating pipeline in sequence, the fuel heating pipeline is connected to the anode inlet of the stack, the anode outlet of the stack is connected to the air condenser and the gas-liquid separator in sequence, the liquid output end of the gas-liquid separator is connected to the mixer, and the gas output end of the gas-liquid separator is connected to the back pressure regulator and the exhaust gas processor in sequence; The cathode fuel feed subsystem includes a compressor, a humidifier, and an expander connected in sequence; the humidifier is connected to the cathode inlet of the fuel cell stack, and the cathode outlet of the fuel cell stack is connected in sequence to the expander and the exhaust gas processor. The humidifier is a humidification tank or a membrane humidifier; the exhaust gas processor is a completely enclosed structure, and a solid adsorbent is loaded inside to treat incompletely reacted ammonia fuel; The fuel cell stack is a low-temperature direct ammonia fuel cell stack, which has a bipolar plate fuel cell stack structure, and the bipolar plate material is composite graphite or metal; The fuel tank is used to directly store high-concentration ammonia fuel; the high-concentration ammonia fuel is at least one of liquid ammonia and ammonia gas; The low-temperature heat pipe inlet end of the heat exchanger is connected to the fuel tank, the high-temperature heat pipe inlet end is connected to the air condenser, the low-temperature heat pipe outlet end of the heat exchanger is connected to the mixer, and the high-temperature heat pipe outlet end is connected to the gas-liquid separator; A pressure reducing valve is provided on the pipeline between the fuel tank and the heat exchanger; and a circulating pump is provided on the pipeline between the gas-liquid separator and the mixer.

2. A low-temperature direct ammonia fuel cell system, characterized in that: The system includes a fuel tank, an anode fuel feeding subsystem, a cathode fuel feeding subsystem, an exhaust gas processor, and a fuel cell stack; The anode fuel feeding subsystem includes a mixer, a fuel heating pipeline, an air condenser, and a gas-liquid separator; the fuel tank is connected to the mixer and the fuel heating pipeline in sequence, the fuel heating pipeline is connected to the anode inlet of the stack, the anode outlet of the stack is connected to the air condenser and the gas-liquid separator in sequence, the liquid output end of the gas-liquid separator is connected to the mixer, and the gas output end of the gas-liquid separator is connected to the back pressure regulator and the exhaust gas processor in sequence; The cathode fuel feed subsystem includes a compressor, a humidifier, and an expander connected in sequence; the humidifier is connected to the cathode inlet of the fuel cell stack, and the cathode outlet of the fuel cell stack is connected in sequence to the expander and the exhaust gas processor. The humidifier is a humidification tank or a membrane humidifier; the exhaust gas processor is a completely enclosed structure, and a solid adsorbent is loaded inside to treat incompletely reacted ammonia fuel; The fuel cell stack is a low-temperature direct ammonia fuel cell stack, which has a bipolar plate fuel cell stack structure, and the bipolar plate material is composite graphite or metal; The fuel tank is used to directly store high-concentration ammonia fuel; the high-concentration ammonia fuel is at least one of an ammonia solution or an ammonia-alkali mixture; A metering pump is provided on the pipeline between the fuel tank and the mixer, and the metering pump is one of a peristaltic pump, a gear pump, a centrifugal pump, a screw pump, a pneumatic diaphragm pump, and a spiral pump.

3. The low-temperature direct ammonia fuel cell system according to claim 1 or 2, characterized in that: The fuel tank is a closed structure; when liquid ammonia or ammonia gas is used as fuel, the fuel tank is made of stainless steel or aluminum, and the design pressure is ≥1MPa; when ammonia solution or ammonia-alkali mixture is used as fuel, the fuel tank is made of polyethylene, polypropylene, polyethylene terephthalate or aluminum, and is stored at room temperature and pressure.

4. The low-temperature direct ammonia fuel cell system according to claim 1 or 2, characterized in that: The fuel heating pipeline is a stainless steel pipeline, a tetrafluoroethylene pipeline, a polyvinylidene fluoride pipeline, a polyethylene pipeline, or a polypropylene pipeline; The heating method uses a heating tape or heating rod placed outside the fuel heating pipeline for heating.

5. The low-temperature direct ammonia fuel cell system according to claim 1 or 2, characterized in that: The mixer is one of a propeller stirrer, a turbine stirrer, a paddle stirrer, and a ribbon stirrer.

6. The low-temperature direct ammonia fuel cell system according to claim 1 or 2, characterized in that: The compressor is one of piston type, screw type, scroll type, centrifugal type, axial flow type and jet type; the expander is one of piston type and turbine type.

7. The low-temperature direct ammonia fuel cell system according to claim 1 or 2, characterized in that: The tail gas processor is internally loaded with a solid absorbent, and the solid absorbent is one of superphosphate, Prussian blue, silica gel, and activated carbon.

8. The low-temperature direct ammonia fuel cell system according to claim 1 or 2, characterized in that: The metal is a stainless steel plate, a stainless steel plate with a coating or a titanium plate, and the coating is a mixed coating of one or more of carbon, chromium, nickel, gold and silver.

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