An ammonia hydrogen production system based on thermoelectric coupling

Abstract

The present invention discloses an ammonia hydrogen production system based on thermoelectric coupling, which includes a thermoelectric power generation device, an ammonia reactor and a cooling water tank. The present invention designs a thermoelectric power generation device based on the temperature difference between the liquid ammonia and the exhaust gas of the internal combustion engine. The liquid ammonia flows into the thermoelectric power generation device and completes gasification, then flows through the preheater to be heated by high-temperature cooling water, then flows through the heater to be heated again, and finally flows into the reactor to undergo a decomposition reaction. The decomposed mixed gas is adjusted by the fuel supply system and sprayed into the cylinder of the internal combustion engine to complete combustion; the internal combustion engine flue gas first flows into the thermoelectric power generation device, then heats the ammonia and provides heat for the ammonia decomposition reaction. The ammonia hydrogen production system uses waste heat to provide heat for ammonia vaporization and ammonia decomposition, and uses the temperature difference between the high temperature of the flue gas and the low temperature of the liquid ammonia to generate electricity. It has high energy utilization efficiency and can achieve precise control of the reactor temperature; the designed thermoelectric power generation device has a large overall heat exchange capacity and high power generation efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of waste heat utilization of power devices such as internal combustion engines, and in particular to an ammonia-hydrogen production system based on thermoelectric coupling. Background Art

[0002] Ammonia, as a zero-carbon fuel and chemically stable hydrogen carrier, has been extensively researched in the internal combustion engine field. However, the vaporization of liquid ammonia and the decomposition of ammonia to produce hydrogen require significant heat consumption. Currently, on-board ammonia-to-hydrogen systems primarily utilize the internal combustion engine's cooling water and exhaust waste heat to provide heat for liquid ammonia vaporization and decomposition. However, the stability of the internal combustion engine's waste heat is poor, and the temperature control precision within the ammonia decomposition reactor is low, making the extent of the ammonia decomposition reaction difficult to control. Consequently, the hydrogen content of the ammonia-hydrogen mixture after the reaction may not meet the engine's intake requirements.

[0003] To address the difficulty in controlling the ammonia decomposition reaction temperature due to unstable waste heat, existing technologies often use additional electric heating and gas heating to compensate for the waste heat. However, additional gas heating consumes additional fuel, and additional electric heating consumes mechanical energy from the internal combustion engine to generate electricity. These compensation methods reduce the thermal efficiency of the internal combustion engine.

[0004] At the same time, the flue gas temperature of the ammonia internal combustion engine is relatively high and contains a large amount of waste heat; the vaporization of liquid ammonia absorbs a large amount of heat, resulting in the temperature of the vaporization chamber often being lower than the ambient temperature, and there is a large temperature difference between the two. Summary of the Invention

[0005] The purpose of the present invention is to provide an ammonia-hydrogen production system based on thermoelectric coupling, which can effectively solve problems such as unstable waste heat of internal combustion engines and achieve precise control of the ammonia decomposition reaction temperature.

[0006] To achieve the above object, the present invention provides the following solution: The present invention provides a thermoelectric coupled ammonia hydrogen production system, comprising

[0007] A thermoelectric power generation device comprising a vaporization chamber, a power generation device, and a flue gas chamber. Liquid ammonia in a liquid ammonia tank is regulated by a flow control valve and communicates with an inclined liquid ammonia nozzle in the vaporization chamber. The vaporized ammonia flows out of the vaporization chamber through an exhaust port, then flows through a preheater for heating and is heated again in the heater before flowing into an ammonia reactor. Flue gas from an internal combustion engine first flows into the flue gas chamber, where the flue gas discharged from the flue gas chamber is used to heat the ammonia and provide heat for the ammonia decomposition reaction in the ammonia reactor. The power generation device comprises an insulating ceramic sheet, a conductive metal sheet, and a PN semiconductor. An insulating ceramic sheet is provided in close contact with the bottom of the vaporization chamber and the top of the flue gas chamber. A plurality of conductive metal sheets are spaced apart on the insulating ceramic sheet. A PN semiconductor is installed between two adjacent conductive metal sheets that are offset vertically. The conductive metal sheet is connected to a battery via a wire.

[0008] An ammonia reactor, wherein the heater and the ammonia reactor are arranged in the exhaust pipe of the internal combustion engine, and a temperature controller, an electric heater and a temperature sensor are attached to the interior of the ammonia reactor. The mixed gas decomposed in the ammonia reactor is mixed by the fuel supply system and then sprayed into the cylinder of the internal combustion engine to complete combustion; and

[0009] The cooling water tank stores the cooling water of the internal combustion engine. During the operation of the internal combustion engine, the cooling water in the cooling water tank flows into the internal combustion engine, absorbs heat and heats up, then flows into the preheater to provide heat for heating the ammonia gas, and finally flows back to the cooling water tank.

[0010] Preferably, the vaporization chamber is arranged at the top of the power generation equipment, and the liquid ammonia nozzles in the vaporization chamber are arranged obliquely from top to bottom. The inclination angle of the liquid ammonia nozzles needs to be corrected according to the nozzle diameter; the exhaust port diameter of the vaporization chamber is larger than the diameter of the liquid ammonia nozzles.

[0011] Preferably, the flue gas chamber is arranged at the bottom of the power generation equipment, and a plurality of rows of triangular needle ribs are arranged at equal intervals on the top of the flue gas chamber, and a plurality of guide ribs are arranged at equal intervals on the bottom of the flue gas chamber, and the inclination direction of the guide ribs is consistent with the flow direction of the flue gas; the overall flow direction of the flue gas in the flue gas chamber is opposite to the flow direction of the ammonia in the gasification chamber.

[0012] Preferably, the inclination angle and length of the guide ribs are set according to the flow intensity and heat transfer coefficient of the flue gas in the flue gas chamber; the cross section of the triangular needle ribs is triangular, and the bottom side of the triangular needle ribs is set perpendicular to the flue gas flow direction.

[0013] Preferably, the height of the smoke outlet of the smoke chamber is higher than the height of the smoke inlet.

[0014] Preferably, the outer structure of the ammonia reactor is elliptical, the interior of the ammonia reactor is a honeycomb carrier structure, and the catalyst is attached to the honeycomb carrier structure.

[0015] Preferably, the ammonia decomposition reaction occurring in the ammonia reactor is:

[0016] Preferably, the preheater is a heat pipe gas-liquid heat exchanger; and the heater is a fin heat exchanger.

[0017] Compared with the prior art, the present invention has achieved the following beneficial technical effects:

[0018] The ammonia hydrogen production system based on thermoelectric coupling in the present invention is suitable for ammonia hydrogen production in multiple scenarios such as trucks and ships using ammonia fuel. The system includes a thermoelectric power generation device, an ammonia reactor and a cooling water tank. The present invention designs a thermoelectric power generation device based on the temperature difference between the liquid ammonia and the exhaust gas of the internal combustion engine. Liquid ammonia flows into the thermoelectric power generation device and completes gasification, then flows through the preheater to be heated by high-temperature cooling water, then flows through the heater to be heated again, and finally flows into the reactor to undergo a decomposition reaction. The decomposed mixed gas is adjusted by the fuel supply system and sprayed into the cylinder of the internal combustion engine to complete combustion; the internal combustion engine flue gas first flows into the thermoelectric power generation device, then heats the ammonia and provides heat for the ammonia decomposition reaction. The ammonia hydrogen production system uses waste heat to provide heat for ammonia vaporization and ammonia decomposition, and uses the temperature difference between the high temperature of the flue gas and the low temperature of the liquid ammonia to generate electricity. It has high energy utilization efficiency and can achieve precise control of the reactor temperature; the designed thermoelectric power generation device has a large overall heat exchange capacity and high power generation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 Schematic diagram of the overall structure of the ammonia-to-hydrogen system based on thermoelectric coupling in an embodiment of the present invention;

[0021] Figure 2 This is the overall structural principle diagram of the thermoelectric power generation equipment;

[0022] Figure 3 This is the arrangement diagram of the triangular pin fins and guide fins in the flue gas chamber;

[0023] Among them, 1. Liquid ammonia tank; 2. Temperature difference power generation equipment; 21. Flue gas chamber; 22. Guide fins; 23. Triangular needle fins; 24. Insulating ceramic sheet; 25. PN semiconductor; 26. Conductive metal sheet; 27. Vaporization chamber; 28. Liquid ammonia nozzle; 3. Preheater; 4. Heater; 5. Ammonia reactor; 6. Fuel supply system; 7. Internal combustion engine; 101. Exhaust pipe; 201. Cooling water tank; 301. Battery. DETAILED DESCRIPTION

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0025] The purpose of the present invention is to provide an ammonia hydrogen production system based on thermoelectric coupling. In order to achieve precise control of the ammonia decomposition temperature, a thermoelectric power generation device is used to generate electricity by the temperature difference between liquid ammonia and high-temperature flue gas, and the device is applied to a vehicle / ship-mounted ammonia hydrogen production system; the thermoelectric power generation device mainly uses thermoelectric semiconductors, and the power generation principle follows the Seebeck effect. Its structural form is conducive to accelerating the gasification of liquid ammonia and enhancing the heat exchange of high-temperature flue gas, increasing the temperature difference on both sides of the power generation equipment, and improving the power generation efficiency; the ammonia hydrogen production system using this thermoelectric power generation device can effectively solve problems such as unstable waste heat of internal combustion engines and achieve precise control of the ammonia decomposition reaction temperature.

[0026] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] like Figure 1-Figure 3 As shown, the present invention provides an ammonia hydrogen production system based on thermoelectric coupling, which mainly includes a liquid ammonia tank 1, a thermoelectric power generation device 2, a flow control valve, a preheater 3, a heater 4, an ammonia reactor 5, a fuel supply system 6, an internal combustion engine 7, a cooling water tank 201, a battery 301 and connecting pipelines. The heater 4 and the ammonia reactor 5 are arranged in the exhaust pipe 101 of the flue gas of the internal combustion engine 7. The ammonia reactor 5 is equipped with a thermostat, an electric heater 4 and a temperature sensor. The structure of the thermoelectric power generation device 2 is shown in the attached figure. Figure 2 As shown in FIG, it mainly includes a smoke chamber 21 with guide fins 22 and needle fins, an insulating ceramic sheet 24, a PN semiconductor 25, a conductive metal sheet 26, and an ammonia gasification chamber 27 with ammonia nozzles. Figure 1 As shown, ammonia is usually stored in a high-pressure liquid ammonia tank 1 (>0.8MPa) in liquid form. When the ammonia hydrogen production system is in operation, the liquid ammonia flows into the thermoelectric power generation device 2 through the flow control valve and completes gasification. It then flows through the preheater 3 to be heated by high-temperature cooling water, and then flows through the heater 4 to be heated again. Finally, it flows into the reactor to undergo a decomposition reaction. The specific reaction formula is: The decomposed gas mixture (ammonia, hydrogen, and nitrogen) is blended by fuel supply system 6 and injected into the cylinders of internal combustion engine 7 for combustion. Cooling water for internal combustion engine 7 is stored in cooling water tank 201. During operation, the cooling water flows into internal combustion engine 7, absorbs heat, and then flows into preheater 3 to provide heat for the ammonia before returning to cooling water tank 201. The flue gas from internal combustion engine 7 first flows into thermoelectric generator 2, where it heats the ammonia and provides heat for the ammonia decomposition reaction.

[0028] Specifically, compared with the conventional internal combustion engine 7 waste heat thermoelectric power generation equipment 2, the present invention improves the power generation equipment suitable for liquid ammonia and high-temperature flue gas temperature differential power generation, and the structural details of the improved thermoelectric power generation equipment 2 are now described in detail.

[0029] The main structure of the thermoelectric power generation equipment 2 is shown in the attached figure. Figure 2 As shown. The overall structure, from top to bottom, consists of a vaporization chamber 27, an insulating ceramic sheet 24, a conductive metal, a PN semiconductor 25, a conductive metal, an insulating ceramic sheet 24, and a flue gas chamber 21. The vaporization chamber 27 is located at the top of the power generation equipment. The liquid ammonia nozzles 28 within the vaporization chamber 27 are arranged obliquely from top to bottom and have a relatively small diameter. After flowing out of the liquid ammonia tank 1, the liquid ammonia flows through the liquid ammonia nozzles 28 and accelerates, striking the lower wall of the vaporization chamber 27 at a high speed. Upon impacting the wall, the liquid ammonia breaks up, rapidly vaporizes, expands in volume, and increases in flow rate. This creates relatively strong turbulence within the vaporization chamber 27, further enhancing heat exchange. The turbulence also helps improve the temperature uniformity of the vaporization chamber 27 and increases the overall temperature difference of the thermoelectric power generation equipment 2. The vaporized ammonia flows out of the vaporization chamber 27 through the exhaust port. The diameter and angle of the liquid ammonia nozzle 28 are key factors influencing the performance of the vaporizer 27. An excessively large nozzle diameter results in a low velocity for the liquid ammonia flowing into the vaporizer 27, preventing the collision with the wall from breaking up the liquid ammonia and reducing the vaporization velocity. An excessively small nozzle diameter causes the liquid ammonia to rapidly atomize at the nozzle, causing it to accumulate at the inlet and resulting in uneven temperature distribution across the equipment. Furthermore, the nozzle angle should be adjusted to match the nozzle diameter (liquid ammonia velocity) to ensure uniform adhesion of the liquid ammonia to the lower wall of the vaporizer 27. When designing the vaporizer 27, research should be conducted on ammonia flow and vaporization characteristics under varying nozzle diameters and angles to optimize design parameters.

[0030] The flue gas chamber 21 is arranged at the bottom of the power generation equipment, and its three-dimensional structure diagram is shown in the attached figure. Figure 3 As shown, the top is triangular pin ribs 23 and the bottom is guide ribs 22. The inclination direction of the guide ribs 22 is consistent with the direction of flue gas flow. Flue gas flows into the flue gas chamber 21 from the inlet, and forms a tumble under the action of the guide ribs 22, flushing the triangular pin ribs 23 at the top of the flue gas chamber 21, releasing heat, and finally flowing out from the flue gas outlet. The overall flow direction of the flue gas should be opposite to the flow direction of ammonia gas to increase the average temperature difference of the temperature difference heat exchange equipment. The main function of the guide ribs 22 is to enhance the turbulence intensity of the flue gas chamber 21 and inhibit flue gas backflow. The angle and length of the guide ribs 22 are key to the design of the flue gas chamber 21. Too small an inclination angle may result in low flow intensity in the flue gas chamber 21, while too large an inclination angle will increase the flue gas flow pressure loss. Too short a guide rib 22 may slow down the flue gas flow rate, resulting in a low convective heat transfer coefficient of the equipment. Too long a guide rib 22 may reduce the residence time of the flue gas in the flue gas chamber 21, reducing the total heat exchange capacity of the flue gas. Therefore, when designing the gasification chamber 27, it is important to study the flue gas flow and heat transfer characteristics under different guide fin 22 angles and lengths to optimize the design parameters. Furthermore, the triangular pin fins 23 at the top of the flue gas chamber 21 increase the flue gas heat transfer area, and optimizing their number and length is also crucial.

[0031] The insulating ceramic sheet 24, which is in close contact with the gasification chamber 27 and the flue gas chamber 21, has excellent thermal conductivity. Heat / cold energy passes through the insulating ceramic sheet 24 and the conductive metal sheet 26, acting on both ends of the PN semiconductor 25, generating a potential difference. This electrical energy is then transferred from the conductive metal sheet 26 to the battery 301, providing energy for the electrical heating within the ammonia reactor 5.

[0032] In one embodiment, the height of the smoke outlet of the smoke chamber 21 should be higher than the height of the smoke inlet to reduce the pressure loss of smoke flow; the shape of the pin ribs on the top of the smoke chamber 21 is preferably triangular pin ribs 23 along the flow direction.

[0033] In one embodiment, the length of the top pin ribs of the smoke chamber 21 can be designed to be trapezoidal to optimize the overall quality of the equipment.

[0034] In one embodiment, the outlet diameter of the vaporization chamber 27 is preferably larger than the diameter of the liquid ammonia nozzle 28 to reduce ammonia flow loss.

[0035] In one embodiment, copper should not be used in the components of the thermoelectric power generation equipment 2 and the ammonia-hydrogen production system that come into contact with ammonia; when designing the thermoelectric power generation equipment 2, parameters of the guide fins 22 of the flue gas chamber 21 and the liquid ammonia nozzles 28 of the gasification chamber 27 need to be optimized.

[0036] In one embodiment, the thermoelectric power generation material is preferably a medium-temperature thermoelectric power generation material such as PbTe, and the insulating ceramic sheet 24 can be made of high thermal conductivity and high insulation DBC ceramic.

[0037] In one embodiment, during heat exchange optimization and energy balance calculation, it is allowed to replace the order of the ammonia reactor 5 and the heater 4 in the exhaust pipe 101 as appropriate, that is, the ammonia reactor 5 is placed upstream of the exhaust pipe 101 (the heater 4 is placed downstream) or the ammonia reactor 5 is placed downstream of the exhaust pipe 101 (the heater 4 is placed upstream).

[0038] In one embodiment, the ammonia reactor 5 has an elliptical outer structure and a honeycomb carrier structure inside, and is equipped with an electric heater 4 and a temperature sensor, and the catalyst is attached to the honeycomb carrier; the ammonia reactor 5 has an electric heater 4 and a temperature sensor inside, and its temperature is controlled by a thermostat.

[0039] In one embodiment, the preheater 3 is a heat pipe gas-liquid heat exchanger; the heater 4 is a finned heat exchanger to minimize the exhaust gas pressure loss and increase the heat exchange area.

[0040] The advantages of the ammonia-to-hydrogen system based on thermoelectric coupling in the present invention are as follows:

[0041] 1. The ammonia-to-hydrogen system proposed in the present invention uses waste heat to provide heat for ammonia vaporization and decomposition, and uses the temperature difference between the high temperature of flue gas and the low temperature of liquid ammonia to generate electricity. It has high energy utilization efficiency and can achieve precise control of the reactor temperature.

[0042] 2. The present invention improves the vaporization chamber 27 and flue gas chamber 21 in the thermoelectric power generation device 2. Built-in liquid ammonia nozzles 28 in the vaporization chamber 27 accelerate the vaporization of liquid ammonia, while guide fins 22 in the flue gas chamber 21 increase the flue gas heat exchange rate. This results in a high overall heat exchange capacity for the thermoelectric module and a high degree of device integration.

[0043] 3. Compared with the existing internal combustion engine 7 waste heat temperature difference power generation technology, the liquid ammonia and flue gas temperature difference power generation equipment 2 proposed by the present invention has a large temperature difference, high power generation efficiency (>15%), a thermoelectric figure of merit greater than 3, and high application value.

[0044] 4. The PN junction in the thermoelectric power generation device 2 has a relatively large thermal conductivity. Compared with liquid nitrogen vaporization at room temperature, the liquid ammonia vaporization solution presented in the present invention has a faster vaporization speed and can increase the ammonia temperature to a certain extent.

[0045] It should be noted that it is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, from all perspectives, the embodiments should be regarded as illustrative and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the foregoing description. It is intended that all changes that fall within the meaning and range of equivalents of the claims be included in the present invention, and any reference signs in the claims should not be construed as limiting the claims to which they relate.

[0046] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A thermoelectric coupled ammonia-to-hydrogen system, characterized by: include A thermoelectric power generation device comprising a vaporization chamber, a power generation device, and a flue gas chamber. Liquid ammonia in a liquid ammonia tank is regulated by a flow control valve and communicates with an inclined liquid ammonia nozzle in the vaporization chamber. The vaporized ammonia flows out of the vaporization chamber through an exhaust port, then flows through a preheater for heating and is heated again in the heater before flowing into an ammonia reactor. Flue gas from an internal combustion engine first flows into the flue gas chamber, where the flue gas discharged from the flue gas chamber is used to heat the ammonia and provide heat for the ammonia decomposition reaction in the ammonia reactor. The power generation device comprises an insulating ceramic sheet, a conductive metal sheet, and a PN semiconductor. An insulating ceramic sheet is provided in close contact with the bottom of the vaporization chamber and the top of the flue gas chamber. A plurality of conductive metal sheets are spaced apart on the insulating ceramic sheet. A PN semiconductor is installed between two adjacent conductive metal sheets that are offset vertically. The conductive metal sheet is connected to a battery via a wire. An ammonia reactor, wherein the heater and the ammonia reactor are arranged in the exhaust pipe of the internal combustion engine, and a temperature controller, an electric heater and a temperature sensor are attached to the interior of the ammonia reactor. The mixed gas decomposed in the ammonia reactor is mixed by the fuel supply system and then sprayed into the cylinder of the internal combustion engine to complete combustion; and The cooling water tank stores the cooling water of the internal combustion engine. During the operation of the internal combustion engine, the cooling water in the cooling water tank flows into the internal combustion engine, absorbs heat and heats up, then flows into the preheater to provide heat for heating the ammonia gas, and finally flows back to the cooling water tank.

2. The thermoelectric coupled ammonia-to-hydrogen system according to claim 1, characterized in that: The vaporization chamber is arranged on the top of the power generation equipment, and the liquid ammonia nozzles in the vaporization chamber are arranged obliquely from top to bottom. The inclination angle of the liquid ammonia nozzles needs to be corrected according to the nozzle diameter; the exhaust port diameter of the vaporization chamber is larger than the diameter of the liquid ammonia nozzles.

3. The thermoelectric coupled ammonia-to-hydrogen system according to claim 1, characterized in that: The flue gas chamber is arranged at the bottom of the power generation equipment. A plurality of rows of triangular needle ribs are arranged at equal intervals on the top of the flue gas chamber. A plurality of guide ribs are arranged at equal intervals on the bottom of the flue gas chamber. The inclination direction of the guide ribs is consistent with the flow direction of the flue gas. The overall flow direction of the flue gas in the flue gas chamber is opposite to the flow direction of the ammonia in the gasification chamber.

4. The thermoelectric coupled ammonia-to-hydrogen system according to claim 3, characterized in that: The inclination angle and length of the guide ribs are set according to the flow intensity and heat transfer coefficient of the flue gas in the flue gas chamber; the cross section of the triangular needle ribs is triangular, and the bottom side of the triangular needle ribs is set perpendicular to the flue gas flow direction.

5. The thermoelectric coupled ammonia-to-hydrogen system according to claim 1, characterized in that: The height of the smoke outlet of the smoke chamber is higher than the height of the smoke inlet.

6. The thermoelectric coupled ammonia-to-hydrogen system according to claim 1, characterized in that: The outer structure of the ammonia reactor is elliptical, the interior of the ammonia reactor is a honeycomb carrier structure, and the catalyst is attached to the honeycomb carrier structure.

7. The thermoelectric coupled ammonia-to-hydrogen system according to claim 1, characterized in that: The ammonia decomposition reaction occurring in the ammonia reactor is:

8. The thermoelectric coupled ammonia-to-hydrogen system according to claim 1, characterized in that: The preheater is a heat pipe type gas-liquid heat exchanger; the heater is a fin type heat exchanger.

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