A series power supply system and method for LOHC and hydrogen internal combustion engine

Abstract

This invention discloses a series-connected LOHC (Locally Optimized Harness) and hydrogen internal combustion engine energy supply system and method, comprising a LOHC dehydrogenation reaction system, a LOHC preheating system, a hydrogen internal combustion engine power generation and energy storage system, and an exhaust gas waste heat recovery system. The LOHC preheating system, LOHC dehydrogenation reaction system, and hydrogen internal combustion engine power generation and energy storage system are connected in series to complete system energy conversion. The LOHC preheating system and exhaust gas waste heat recovery system provide the energy required for the LOHC dehydrogenation reaction system, while the hydrogen internal combustion engine power generation and energy storage system provides external energy output and auxiliary heating to the LOHC dehydrogenation reaction system. This invention features two-stage LOHC preheating, internal combustion engine coolant waste heat recovery, two-stage internal combustion engine exhaust gas waste heat recovery, and electric heating-assisted start-up, maximizing energy utilization and the stability of LOHC dehydrogenation.

Description

Technical Field

[0001] This invention relates to the field of hydrogen energy technology, specifically to a series energy supply system and method of LOHC and hydrogen internal combustion engine. Background Technology

[0002] Currently, in hydrogen applications in the mobile sector, on-board hydrogen storage cylinders at 70 MPa contain only about 39g of hydrogen per liter. China primarily uses 35 MPa hydrogen storage cylinders, which weigh only about 20-22g per liter and pose safety hazards such as leakage and explosion. In contrast, organic liquid hydrogen storage (LOHC) offers advantages such as high hydrogen storage density and safety, thus possessing immense potential for development and research.

[0003] Organic liquid hydrogen storage technology mainly utilizes unsaturated liquid organic compounds (such as toluene, naphthalene, ethylcarbazole, etc.) as hydrogen storage agents and corresponding saturated compounds (such as methylcyclohexane, decahydronaphthalene, dodecahydroethylcarbazole, etc.) as hydrogen carriers to undergo reversible hydrogenation and dehydrogenation reactions with hydrogen gas to achieve hydrogen storage and release. Organic liquid hydrogen storage has the following characteristics: (1) the reaction process is reversible and the hydrogen storage density is high; (2) the hydrogen carrier is safe and convenient to store and transport, and is suitable for long-distance transportation; (3) existing infrastructure such as gasoline pipelines and gas stations can be utilized. At the same time, organic liquid hydrogen storage also has problems that need to be solved: the dehydrogenation reaction needs to be carried out at low pressure and high temperature, the reaction efficiency is low, and side reactions are prone to occur.

[0004] The dehydrogenation reaction of LOHC (liquid organic hydrogen carrier) requires harsh conditions, including high-temperature catalysis and significant energy consumption. Stable heat is also essential to ensure product purity and yield. When LOHC is used as a fuel source in conjunction with a hydrogen internal combustion engine, unstable dehydrogenation reaction rates can affect the fuel supply to the engine. Furthermore, if the heat generated by the hydrogen internal combustion engine is used to maintain the dehydrogenation reaction temperature, system stability can be severely compromised. Therefore, it is crucial to ensure stable operation of all components after system startup.

[0005] When a hydrogen internal combustion engine is operating, hydrogen reacts with oxygen in the air to produce an exhaust temperature that can reach 500 degrees Celsius. Additionally, the engine typically cools itself using a coolant, which dissipates heat through heat exchange with the air. The heat loss from direct exhaust emissions and coolant cooling accounts for approximately 50% of the energy released by fuel combustion in a hydrogen internal combustion engine. Failure to utilize this heat would result in a significant waste of resources.

[0006] In summary, existing high-pressure gaseous hydrogen storage cylinders pose significant safety risks. LOHC technology, which enables high-density and safe hydrogen storage, requires a stable heat source during operation. Existing LOHC systems combined with internal combustion engines typically suffer from insufficiently stable heat sources, leading to low dehydrogenation efficiency. Furthermore, existing systems have low utilization rates of engine coolant and exhaust waste heat, resulting in low system efficiency. Summary of the Invention

[0007] To overcome the above technical problems, the present invention aims to provide a series energy supply system and method for LOHC and hydrogen internal combustion engine, which features two-stage preheating of LOHC, waste heat recovery of internal combustion engine coolant, two-stage waste heat recovery of internal combustion engine exhaust gas, and electric heating assisted start, thereby maximizing energy utilization and the stability of LOHC dehydrogenation.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A series-connected LOHC and hydrogen internal combustion engine energy supply system includes an LOHC dehydrogenation reaction system, an LOHC preheating system, a hydrogen internal combustion engine power generation and energy storage system, and an exhaust gas waste heat recovery system.

[0010] The LOHC preheating system, LOHC dehydrogenation reaction system, and hydrogen internal combustion engine power generation and energy storage system are connected in series to complete the system energy conversion. The LOHC preheating system and the exhaust gas waste heat recovery system provide the energy required for the LOHC dehydrogenation reaction system, while the hydrogen internal combustion engine power generation and energy storage system outputs energy to the outside and provides auxiliary heating to the LOHC dehydrogenation reaction system.

[0011] The LOHC dehydrogenation reaction system includes an oil tank, heat exchanger one, heat exchanger two, and a dehydrogenation reactor connected in series. The LOHC dehydrogenation reaction system converts LOHC preheated by the LOHC preheating system into dehydrogenated LOHC and hydrogen through a dehydrogenation reaction.

[0012] The LOHC preheating system includes a heat exchanger, the liquid phase inlet of which is connected to the oil tank outlet, the liquid phase outlet of which is connected to one of the inlets of a heat exchanger, and the outlet of the heat exchanger connected to the dehydrogenation reactor.

[0013] The hydrogen generated in the dehydrogenation reactor is connected to the gas phase inlet of heat exchanger 2 through the gas phase outlet of the dehydrogenation reactor. The gas phase outlet of heat exchanger 2 is connected to the fuel inlet of the hydrogen internal combustion engine. The LOHC that has been reacted in the dehydrogenation reactor is connected to another inlet of heat exchanger 2 through the liquid phase outlet of the dehydrogenation reactor. The corresponding outlet of heat exchanger 2 is connected to the inlet of the LOHC section that has been dehydrogenated and stored in the fuel tank.

[0014] The LOHC preheating system is used to preheat the LOHC in two stages, recovering heat from the hydrogen internal combustion engine coolant, the dehydrogenated LOHC, and hydrogen.

[0015] The hydrogen internal combustion engine power generation and energy storage system includes a hydrogen internal combustion engine, a generator, and a battery. The hydrogen internal combustion engine drives the generator to generate electrical energy and stores the energy in the battery for energy output.

[0016] The hydrogen internal combustion engine power generation and energy storage system is used to convert the energy from hydrogen combustion into electrical energy for output or storage, and at the same time heats the LOHC dehydrogenation reactor during startup.

[0017] The exhaust gas waste heat recovery system performs secondary recovery and utilization of heat in the exhaust gas of the hydrogen internal combustion engine. The exhaust gas of the hydrogen internal combustion engine enters the dehydrogenation reactor through the exhaust gas pipeline, where it releases heat. The exhaust gas from the dehydrogenation reactor then enters the organic Rankine cycle through the exhaust gas pipeline for secondary utilization. The organic working fluid enters the evaporator after passing through the working fluid pump, where it exchanges heat with the exhaust gas entering the evaporator. After absorbing heat, the organic working fluid enters the expander to generate mechanical energy, which drives the generator to generate electricity and stores the electrical energy in the battery. The organic working fluid is condensed in the condenser and then re-enters the working fluid pump for circulation.

[0018] The exhaust gas waste heat recovery system performs two-stage waste heat recovery on the hydrogen internal combustion engine exhaust gas through heat exchange and organic Rankine cycle.

[0019] A method for operating a series-connected LOHC and hydrogen internal combustion engine energy supply system includes the following steps;

[0020] The dehydrogenation reactor, hydrogen internal combustion engine and generator are connected in series. The dehydrogenation reactor is supplied with undehydrogenated LOHC through the fuel tank. The generated hydrogen is supplied to the hydrogen internal combustion engine to drive the generator, and the obtained electrical energy is stored in the battery 7 as an energy reserve.

[0021] The undehydrogenated LOHC in the oil tank is preheated in two stages by heat exchanger one and heat exchanger two before entering the dehydrogenation reactor.

[0022] The undehydrogenated LOHC first exchanges heat with the coolant in the hydrogen internal combustion engine in heat exchanger one to complete the first stage of preheating.

[0023] After primary preheating, the LOHC undergoes heat exchange in heat exchanger two with the dehydrogenated LOHC and hydrogen that have completed their reaction in the dehydrogenation reactor, completing secondary preheating. Subsequently, the LOHC enters the dehydrogenation reactor, and the dehydrogenated LOHC that has completed heat exchange in heat exchanger two returns to the fuel tank. The hydrogen that has completed heat exchange in heat exchanger two enters the hydrogen internal combustion engine.

[0024] The exhaust gas produced by the hydrogen internal combustion engine is not directly emitted, but is instead recovered and utilized through two stages of waste heat recovery.

[0025] The first-stage waste heat recovery is used to heat the dehydrogenation reactor, providing heat for the dehydrogenation reaction and meeting the temperature required for the dehydrogenation reaction.

[0026] The second stage of waste heat recovery utilizes the remaining heat to drive a generator to generate electricity, while simultaneously storing the electrical energy in a battery.

[0027] The first-stage waste heat recovery directly uses the dehydrogenation reactor to absorb the heat in the tail gas. The water vapor generated by the reaction is passed into the dehydrogenation reactor for heat exchange, completing the first-stage utilization. Since the tail gas produced by hydrogen combustion is almost entirely composed of water vapor, and the dehydrogenation reaction temperature is high, the tail gas after the first heat exchange is still almost entirely composed of water vapor. Therefore, after the first-stage waste heat recovery, it enters the evaporator through the tail gas channel.

[0028] After the first stage of waste heat recovery, the second stage of waste heat recovery and power generation is carried out through an organic Rankine cycle. In the second stage of waste heat recovery, water vapor is condensed into liquid water. The organic working fluid enters the evaporator through the working fluid pump and exchanges heat with the exhaust gas entering the evaporator. After absorbing heat, it enters the expander to generate mechanical energy, which drives the generator to generate electricity and stores the electrical energy in the battery. After the organic working fluid is condensed in the condenser, it enters the working fluid pump again for circulation, completing the second stage of waste heat recovery and utilization.

[0029] Regardless of the operating conditions required for energy output, the energy is provided by the battery, which is independent of the reaction and combustion rates of the LOHC dehydrogenation reaction system and the hydrogen internal combustion engine, and can meet different energy output needs.

[0030] When the battery has sufficient charge, the front-end power generation system is shut down. When high power or long-term energy output is required, or when the battery charge is less than the set amount, the front-end power generation system is started. At the same time, the battery 7 heats the dehydrogenation reactor through electric heating to meet the temperature conditions required for the dehydrogenation reaction. When the dehydrogenation reaction rate stabilizes, the electric heating is stopped to achieve stable system operation.

[0031] The beneficial effects of this invention are:

[0032] This invention ensures that the LOHC dehydrogenation reaction can proceed continuously and stably through series connection and waste heat recovery, and that the hydrogen internal combustion engine can operate continuously and stably to generate electricity for energy storage and output.

[0033] This system and method employs a two-stage preheating process for the LOHC (Loose-of-House Hybrid Engine) and a two-stage waste heat recovery process for the hydrogen internal combustion engine exhaust. Previously, 10-20% of the hydrogen needed for the LOHC dehydrogenation reaction was consumed; now, this is achieved through waste heat utilization. Especially during the cold start phase when no waste heat is available, electrical energy from the battery can be used to supplement the heating. Therefore, this system and method can effectively reduce hydrogen waste and improve energy efficiency across all operating conditions. Attached image description:

[0034] Figure 1 This is a schematic diagram of the system flow of the present invention. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to the embodiments.

[0036] like Figure 1 As shown: The LOHC dehydrogenation reaction system realizes the LOHC dehydrogenation reaction by connecting oil tank 1, heat exchanger 2, heat exchanger 3 and dehydrogenation reactor 4 in series.

[0037] The oil tank 1 contains LOHC that has not been dehydrogenated and LOHC that has been dehydrogenated. The outlet of the oil tank 1 is connected to the liquid phase inlet of heat exchanger 2. The liquid phase outlet of heat exchanger 2 is connected to one of the inlets of heat exchanger 3. The outlet of heat exchanger 3 is connected to dehydrogenation reactor 4, forming the LOHC feeding process.

[0038] This step completes the LOHC feeding process and enables LOHC preheating. The LOHC preheating system includes two stages of preheating:

[0039] The first stage of preheating of the LOHC is completed in heat exchanger 2, where the hydrogen internal combustion engine coolant exchanges heat with the unreacted LOHC at room temperature, increasing the temperature of the LOHC when it enters heat exchanger 3. Subsequently, the LOHC enters heat exchanger 3. The hydrogen produced in the dehydrogenation reactor 4 is connected to the gas phase inlet of heat exchanger 3 through the gas phase outlet of dehydrogenation reactor 4. The gas phase outlet of heat exchanger 3 is connected to the fuel inlet of the hydrogen internal combustion engine 5. The LOHC that has completed the reaction in dehydrogenation reactor 4 is connected to another inlet of heat exchanger 3 through the liquid phase outlet of dehydrogenation reactor 4. The corresponding outlet of heat exchanger 3 is connected to the inlet of the dehydrogenated LOHC section stored in fuel tank 1. This step performs two stages of preheating of the LOHC, bringing it closer to the temperature required for the dehydrogenation reaction. This allows for the utilization of the waste heat from the hydrogen internal combustion engine coolant, the dehydrogenated LOHC, and the hydrogen, improving energy efficiency.

[0040] In heat exchanger 2, the LOHC absorbs the waste heat from the coolant of the hydrogen internal combustion engine 5, causing its temperature to rise by several tens of degrees. In heat exchanger 3, it exchanges heat with the LOHC after the dehydrogenation reaction and the hydrogen produced by the dehydrogenation reaction. Since the reaction temperature in the dehydrogenation reactor 4 is relatively high, the product temperature can be considered to be approximately the same as its temperature. The temperature of the LOHC rises significantly after passing through heat exchanger 3. Heat exchanger 2 and heat exchanger 3 respectively complete the primary and secondary preheating of the LOHC, making it easier for subsequent reactions to reach the required temperature conditions.

[0041] The hydrogen internal combustion engine power generation and energy storage system generates electricity by driving the generator 6 through the hydrogen internal combustion engine 5 and stores the energy in the battery 7 for energy output.

[0042] The exhaust gas waste heat recovery system performs secondary recovery and utilization of the heat in the exhaust gas of the hydrogen internal combustion engine 5. The exhaust gas first enters the dehydrogenation reactor 4 through the exhaust gas pipeline, where it releases heat. This heat is used to heat the dehydrogenation reaction. Since the exhaust gas temperature of the hydrogen internal combustion engine 5 is relatively high, typically reaching 500 degrees Celsius, and the temperature required for the LOHC dehydrogenation reaction is generally around 200 degrees Celsius, the system can meet the temperature requirements for the dehydrogenation reaction. Furthermore, the temperature of the dehydrogenation reactor 4 is still higher than the boiling point of water vapor, so the exhaust gas after the first-stage waste heat recovery is still in a gaseous state.

[0043] Subsequently, the exhaust gas enters the organic Rankine cycle through the exhaust gas pipeline for secondary utilization. The organic working fluid enters the evaporator 10 after passing through the working fluid pump 9, where it exchanges heat with the exhaust gas entering the evaporator 10. After absorbing heat, the organic working fluid enters the expander 11 to generate mechanical energy, which drives the generator 8 to generate electricity and stores the electrical energy in the battery 7. After the organic working fluid is condensed in the condenser 12, it re-enters the working fluid pump 9 for circulation, completing the second stage of waste heat recovery and utilization of the exhaust gas.

[0044] When the battery has sufficient charge, only the battery needs to be activated for energy output. When a large load or long-term energy output is required, or when the battery charge is too low (generally, a minimum charge setting needs to be made according to the specific situation), the battery heats the LOHC dehydrogenation reactor through electric heating, and at the same time, the entire system is activated for stable energy conversion and power output.

Claims

1. A series-connected LOHC and hydrogen internal combustion engine energy supply system, characterized in that, This includes an LOHC dehydrogenation reaction system, an LOHC preheating system, a hydrogen internal combustion engine power generation and energy storage system, and a waste heat recovery system. The LOHC preheating system, LOHC dehydrogenation reaction system, and hydrogen internal combustion engine power generation and energy storage system are connected in series to complete the system energy conversion. The LOHC preheating system and exhaust gas waste heat recovery system provide the energy required for the LOHC dehydrogenation reaction system, and the hydrogen internal combustion engine power generation and energy storage system outputs energy to the outside and provides auxiliary heating to the LOHC dehydrogenation reaction system. The LOHC preheating system includes heat exchanger one (2), the liquid phase inlet of heat exchanger one (2) is connected to the outlet of oil tank (1), the liquid phase outlet of heat exchanger one (2) is connected to one of the inlets of heat exchanger two (3), and the outlet corresponding to heat exchanger two (3) is connected to dehydrogenation reactor (4). The hydrogen generated in the dehydrogenation reactor (4) is connected to the gas phase inlet of the heat exchanger (3) through the gas phase outlet of the dehydrogenation reactor (4). The gas phase outlet of the heat exchanger (3) is connected to the fuel inlet of the hydrogen internal combustion engine (5). The LOHC that has been reacted in the dehydrogenation reactor (4) is connected to the other inlet of the heat exchanger (3) through the liquid phase outlet of the dehydrogenation reactor (4). The corresponding outlet of the heat exchanger (3) is connected to the inlet of the oil tank (1) where the dehydrogenated LOHC is stored. The LOHC preheating system is used to preheat the LOHC in two stages and recover the heat from the hydrogen internal combustion engine (5) coolant, the dehydrogenated LOHC, and hydrogen.

2. The LOHC and hydrogen internal combustion engine series power supply system according to claim 1, characterized in that, The LOHC dehydrogenation reaction system includes an oil tank (1), a heat exchanger one (2), a heat exchanger two (3), and a dehydrogenation reactor (4) connected in series. The LOHC dehydrogenation reaction system converts LOHC preheated by the LOHC preheating system into dehydrogenated LOHC and hydrogen through a dehydrogenation reaction.

3. The LOHC and hydrogen internal combustion engine series power supply system according to claim 1, characterized in that, The hydrogen internal combustion engine power generation and energy storage system includes a hydrogen internal combustion engine (5), a generator (6) and a battery (7). The hydrogen internal combustion engine (5) drives the generator (6) to generate electrical energy and stores the energy in the battery (7) for energy output. The hydrogen internal combustion engine power generation and energy storage system is used to convert the energy from hydrogen combustion into electrical energy for output or storage, and at the same time heats the LOHC dehydrogenation reactor during startup.

4. The LOHC and hydrogen internal combustion engine series power supply system according to claim 1, characterized in that, The exhaust gas waste heat recovery system performs secondary recovery and utilization of the heat in the exhaust gas of the hydrogen internal combustion engine (5). The exhaust gas of the hydrogen internal combustion engine (5) enters the dehydrogenation reactor (4) through the exhaust gas pipeline. Heat is released in the dehydrogenation reactor. The exhaust gas of the dehydrogenation reactor (4) enters the organic Rankine cycle through the exhaust gas pipeline for secondary utilization. The organic working fluid enters the evaporator (10) after passing through the working fluid pump (9) and exchanges heat with the exhaust gas entering the evaporator (10). After absorbing heat, the organic working fluid enters the expander (11) to generate mechanical energy, which drives the generator (8) to generate electricity and stores the electrical energy in the battery (7). After the organic working fluid is condensed in the condenser (12), it re-enters the working fluid pump (9) for circulation. The exhaust gas waste heat recovery system performs two-stage waste heat recovery on the hydrogen internal combustion engine exhaust gas through heat exchange and organic Rankine cycle.

5. The operating method of a LOHC and hydrogen internal combustion engine series energy supply system according to any one of claims 1-4, characterized in that, Includes the following steps; The dehydrogenation reactor (4), hydrogen internal combustion engine (5) and generator (6) are connected in series. The dehydrogenation reactor (4) is supplied with undehydrogenated LOHC through the oil tank (1). The generated hydrogen is supplied to the hydrogen internal combustion engine (5) to drive the generator (6), and the obtained electrical energy is stored in the battery (7) as an energy reserve. The undehydrogenated LOHC in the oil tank (1) is preheated in two stages by heat exchanger one (2) and heat exchanger two (3) before entering the dehydrogenation reactor (4). The undehydrogenated LOHC first exchanges heat with the coolant in the hydrogen internal combustion engine (5) in heat exchanger 1 (2) to complete the first stage of preheating; After primary preheating, the LOHC undergoes heat exchange in heat exchanger 2 (3) with the dehydrogenated LOHC and hydrogen that have finished reacting in the dehydrogenation reactor (4) to complete secondary preheating. Subsequently, the LOHC enters the dehydrogenation reactor (4), and the dehydrogenated LOHC that has completed heat exchange in heat exchanger 2 (3) returns to the oil tank (1). The hydrogen that has completed heat exchange in heat exchanger 2 (3) enters the hydrogen internal combustion engine (5). The exhaust gas produced by the combustion of the hydrogen internal combustion engine (5) is not directly emitted, but is recovered and utilized through two stages of waste heat recovery; The first-stage waste heat recovery is used to heat the dehydrogenation reactor (4) to provide heat for the dehydrogenation reaction and meet the temperature required for the dehydrogenation reaction. The second stage of waste heat recovery utilizes the remaining heat to drive generator 1 (6) to generate electricity, and at the same time stores the electrical energy in the battery (7); The first-stage waste heat recovery directly uses the dehydrogenation reactor (4) to absorb the heat in the tail gas. The water vapor generated by the reaction is passed into the dehydrogenation reactor (4) for heat exchange, thus completing the first-stage utilization. Since the tail gas produced by hydrogen combustion is almost composed of water vapor, and the dehydrogenation reaction temperature is high, the tail gas after the first heat exchange is still almost composed of water vapor. Therefore, after the first-stage waste heat recovery, it enters the evaporator (10) through the tail gas channel. After the first stage of waste heat recovery, the second stage of waste heat recovery and power generation is carried out through organic Rankine cycle. During the second stage of waste heat recovery, water vapor will be condensed into liquid water. The organic working fluid enters the evaporator (10) through the working fluid pump (9) and exchanges heat with the tail gas entering the evaporator (10). After absorbing heat, it enters the expander (11) to generate mechanical energy, which drives the generator (8) to generate electricity and store the electrical energy in the battery (7). After the organic working fluid is condensed in the condenser (12), it enters the working fluid pump (9) again for circulation, completing the second stage of waste heat recovery and utilization of the tail gas.

6. The operating method of a LOHC and hydrogen internal combustion engine series power supply system according to claim 5, characterized in that, When the battery (7) has sufficient power, the front-end power generation system is turned off. When high power or long-term energy output is required, and when the battery (7) has less power than the set amount, the front-end power generation system is started. At the same time, the battery (7) heats the dehydrogenation reactor (4) through electric heating to meet the temperature conditions required for the dehydrogenation reaction. When the dehydrogenation reaction rate is stable, the electric heating is stopped to achieve stable operation of the system.

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