Ammonia-diesel dual fuel cycle system with exhaust gas waste heat cracking

Abstract

The present application relates to a kind of exhaust gas waste heat cracking ammonia diesel dual fuel cycle system, including main engine module, ammonia supply module, ammonia preheating and supply module, diesel supply module and flue gas bypass adjustment mechanism.Ammonia cracking module is integrated in the inside of gas turbine exhaust diffuser, using high-temperature exhaust as heat source to drive ammonia cracking reaction, and the high-temperature mixed gas produced by cracking is sent into combustion chamber as main fuel, and diesel is used as auxiliary fuel.Flue gas bypass adjustment mechanism dynamically adjusts flue gas flow according to load demand.The beneficial effects of the present application are: through direct cracking with exhaust heat and dual fuel collaborative control, efficient use of ammonia fuel and full-condition adaptability are realized in the limited layout space of ship, with the advantages of compact structure, low carbon emission, rapid response, safety and reliability, etc.

Description

Technical Field

[0001] This invention belongs to the field of marine power system technology, specifically relating to an ammonia-diesel dual-fuel cycle system for exhaust gas waste heat decomposition. Background Technology

[0002] Marine propulsion systems have long relied on diesel or heavy oil as fuel. With the International Maritime Organization imposing increasingly stringent restrictions on carbon and nitrogen oxide emissions from ships, and with the ever-increasing demands for lower exhaust temperatures and longer range, the search for low-carbon, efficient, and compact new marine propulsion solutions has become a research hotspot in this field. Ammonia, as a carbon-free fuel, possesses significant advantages such as high energy density, safe storage and transportation, and relatively low cost, and is therefore considered one of the ideal alternative fuels for future marine propulsion.

[0003] However, the direct application of ammonia to marine gas turbines still presents numerous technical challenges. Ammonia has a slow flame propagation speed, which can easily lead to unstable combustion; its high ignition energy makes starting difficult; and the combustion products include a large amount of nitrogen oxides, with unburned ammonia leaks posing a toxic risk. To address these shortcomings, pre-cracking ammonia into a mixture of hydrogen and nitrogen is an effective solution. This mixture can significantly improve combustion characteristics, while the high flame propagation speed of hydrogen can enhance the part-load performance of the gas turbine.

[0004] However, due to the significant differences between ship propulsion systems and land-based power plants, and the extremely limited cabin space on existing ships, it is difficult to arrange complex waste heat boilers and steam circulation systems; ships require rapid start-up and load response capabilities; there are strict industry standards for ship propulsion in terms of system reliability, anti-sway, and shock resistance; fuel storage space is limited, and it is necessary to maximize fuel utilization.

[0005] Therefore, it is essential to provide an ammonia-diesel dual-fuel cycle system for exhaust gas waste heat cracking to solve the above-mentioned technical problems. Summary of the Invention

[0006] This invention provides an ammonia-diesel dual-fuel cycle system for exhaust gas waste heat cracking, which aims to solve the problems of high carbon emissions, poor stability of direct combustion of ammonia fuel, difficulty in starting up, and difficulty in arranging complex waste heat utilization equipment due to limited space in ship cabins.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A dual-fuel cycle system for ammonia and diesel fuel based on exhaust gas waste heat cracking is provided, comprising a gas turbine, a main engine module, an ammonia supply module, an ammonia preheating and supply module, a diesel fuel supply module, and a flue gas bypass regulating mechanism. The main engine module constitutes the body of the gas turbine 1, including a combustion chamber, an air supply module connected to the combustion chamber, and a power supply module connected to the combustion chamber. The ammonia supply module includes an ammonia cracking module integrated inside the exhaust diffuser section of the gas turbine, and the ammonia cracking module is connected to the combustion chamber. The ammonia preheating and supply module... The module includes a liquid ammonia storage tank and an ammonia preheater connected to the liquid ammonia storage tank. The ammonia preheater is connected to the ammonia cracking module. The diesel supply module is connected to the combustion chamber. The flue gas bypass regulating mechanism includes a bypass flue and a regulating baffle disposed on the flue gas side of the ammonia cracking module. The flue gas bypass regulating mechanism is configured to: dynamically adjust according to load demand and cracking rate setpoint; under low load conditions, control the regulating baffle to partially open, allowing some high-temperature flue gas to be discharged through the bypass flue; under high load conditions, control the regulating baffle to close, allowing all flue gas to pass through the ammonia cracking module.

[0008] Preferably, the length of the pyrolysis gas delivery pipeline is controlled within the shortest range to reduce heat loss. After the pyrolysis module is integrated with the gas turbine exhaust diffusion section, the overall volume is reduced by more than 60% compared with the traditional diesel engine power system. The ammonia pyrolysis module, ammonia preheater and connecting pipelines are all designed to be impact-resistant and vibration-resistant to meet the requirements of ship environmental adaptability. The control system is deeply integrated with the ship's integrated control system and has one-button start, automatic mode switching, fault diagnosis and redundancy backup functions. In addition, the liquid ammonia storage tank adopts a double-wall structure and is located in a safe area above the ship's deck. It is equipped with a leak detection and emergency sprinkler system, and the liquid ammonia storage area is physically isolated from the engine room. This makes the safety design more comprehensive. The physical isolation between the liquid ammonia storage and the engine room, the double-walled tank, the leak detection, the emergency sprinkler and other multiple protective measures comply with the regulations for the management of dangerous goods on ships and ensure the safety of the crew and equipment.

[0009] Furthermore, the air supply module includes a compressor, the air outlet of which is connected to the combustion chamber.

[0010] Preferably, the compressor and turbine are coaxially arranged, and the power output shaft of the turbine drives the compressor on one hand and the power system through the reduction gearbox on the other hand, so as to realize the integration of propulsion and power supply.

[0011] Furthermore, the power supply module includes a turbine connected to the output end of the combustion chamber and a reduction gearbox connected to the output end of the turbine, the output end of which is connected to a power system.

[0012] Furthermore, an ammonia pump is connected between the liquid ammonia storage tank and the ammonia preheater.

[0013] Preferably, the ammonia pump is used to pressurize liquid ammonia and send it into the ammonia preheater.

[0014] Furthermore, the ammonia cracking module adopts a compact plate-fin heat exchanger structure, and the inner wall of the ammonia flow channel and the surface of the heat exchange fins of the plate-fin heat exchanger are loaded with a nickel-based catalyst coating for ammonia cracking.

[0015] Preferably, the inner wall of the ammonia flow channel and the surface of the heat exchange fins of the plate-fin heat exchanger are coated with a nickel-based catalyst for ammonia cracking. This coating uses microporous alumina as a carrier and has a thickness of 80 μm to 120 μm. During the operation of the ship's main engine, when ammonia flows through the nickel-based catalyst coating, it absorbs heat transferred from adjacent exhaust gas channels, resulting in a highly efficient catalytic cracking reaction within a temperature range of 450°C to 550°C.

[0016] Furthermore, the heat source acquisition end of the ammonia preheater is located at the high-temperature exhaust gas of the gas turbine.

[0017] Preferably, the heat source collection end of the ammonia preheater is located at the high-temperature exhaust gas of the gas turbine, so as to preheat the ammonia to 350°C to 400°C before sending it into the pyrolysis module.

[0018] Furthermore, the diesel supply module includes a diesel storage tank and a diesel pump connected in sequence, with the output end of the diesel pump connected to the combustion chamber.

[0019] Furthermore, a first nozzle and a second nozzle are connected to the combustion chamber. The first nozzle is connected to the ammonia cracking module, and the second nozzle is connected to the output end of the diesel pump.

[0020] Preferably, the first nozzle is connected to the ammonia cracking module for injecting ammonia cracked gas; the second nozzle is connected to the output end of the diesel pump for injecting diesel fuel. The combustion chamber adopts a dual-fuel nozzle design, using ammonia cracked gas as the main fuel and diesel fuel as the auxiliary fuel.

[0021] Furthermore, it also includes a nitrogen purging module, which includes a nitrogen tank and a nitrogen pump connected to the nitrogen tank, and the nitrogen pump is connected to the combustion chamber.

[0022] Preferably, in the event of an emergency shutdown, the nitrogen purging module is activated to replace the residual combustible gas in the pyrolysis module before it is discharged through the chimney.

[0023] Furthermore, it also includes a chimney, which is connected to the ammonia preheater and the ammonia cracking module respectively.

[0024] Preferably, the chimney is connected to both an ammonia preheater and an ammonia cracking module to discharge the exhaust gas after heat exchange.

[0025] The advantages of this invention compared to the prior art are: 1. The ammonia cracking module is integrated inside the exhaust diffuser section of the gas turbine, eliminating the need for a complex waste heat boiler and steam circulation system. It directly cracks ammonia through exhaust waste heat and reinjects it into combustion, significantly reducing the overall volume and footprint of the power system and significantly reducing its weight. This makes it suitable for the limited space of ships, and the overall structure is compact and adaptable to the space constraints of ships. 2. Deep utilization of ammonia cracking and exhaust gas direct heating: The high-temperature exhaust gas discharged from the gas turbine directly drives the endothermic cracking reaction, realizing the in-situ conversion of waste heat into chemical energy. The overall thermal efficiency of the system is significantly improved compared with the traditional diesel engine power system. 3. The dual-fuel design ensures the ship's maneuverability. Cracking gas is used as the main fuel to reduce carbon emissions, while diesel is used as an auxiliary fuel to ensure rapid start-up, acceleration, and power response speed under maneuvering conditions. 4. It has strong adaptability to all working conditions and load changes. The flue gas bypass regulation and dual fuel ratio coordinated control can achieve stable operation within the load range of 30% to 100%, meeting the diverse working conditions such as ship cruising, high-speed maneuvering, and standby. 5. Ammonia fuel combustion produces no carbon emissions, meeting the requirements for future zero-carbon navigation; gas turbines have lower vibration and noise compared to diesel engines, and the exhaust temperature is reduced after heat absorption by the pyrolysis module, balancing low carbon emissions with high thermal efficiency. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of an ammonia-diesel dual-fuel cycle system for exhaust gas waste heat cracking provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the internal combustion chamber of an ammonia-diesel dual-fuel cycle system for exhaust gas waste heat cracking, provided in an embodiment of the present invention. Figure 3 This is a schematic diagram of the ammonia cracking module in an ammonia-diesel dual-fuel cycle system for waste heat cracking of exhaust gas, provided in an embodiment of the present invention.

[0027] Explanation of reference numerals in the attached figures: 1. Gas turbine; 2. Main unit module; 21. Combustion chamber; 211. First nozzle; 212. Second nozzle; 22. Air supply module; 23. Power supply module; 231. Turbine; 232. Reduction gearbox; 233. Power system; 24. Air compressor; 3. Ammonia supply module; 31. Ammonia cracking module; 311. Ammonia inlet; 312. Ammonia cracked gas outlet; 313. High-temperature tail gas inlet; 314. High-temperature tail gas outlet; 4. Ammonia preheating and supply module; 41. Liquid ammonia storage tank; 42. Ammonia preheater; 43. Ammonia pump; 5. Diesel supply module; 51. Diesel storage tank; 52. Diesel pump; 6. Flue gas bypass regulating mechanism; 61. Bypass flue; 62. Regulating baffle; 7. Nitrogen purging module; 71. Nitrogen tank; 72. Nitrogen pump; 8. Chimney. Detailed Implementation

[0028] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0029] See Figure 1 As shown, this invention discloses an ammonia-diesel dual-fuel cycle system for exhaust gas waste heat cracking, including a gas turbine 1, a main engine module 2, an ammonia supply module 3, an ammonia preheating and supply module 4, a diesel supply module 5, and a flue gas bypass regulating mechanism 6. The main engine module 2 constitutes the body of the gas turbine 1, including a combustion chamber 21, an air supply module 22 connected to the combustion chamber 21, and a power supply module 23 connected to the combustion chamber 21. The ammonia supply module 3 includes an ammonia cracking module 31 integrated inside the exhaust diffuser section of the gas turbine 1, and the ammonia cracking module 31 is connected to the combustion chamber 21. The ammonia preheating and supply module 4 includes a liquid ammonia storage tank. 41 and an ammonia preheater 42 connected to the liquid ammonia storage tank 41, the ammonia preheater 42 being connected to the ammonia cracking module 31; the diesel supply module 5 being connected to the combustion chamber 21; the flue gas bypass regulating mechanism 6 including a bypass flue 61 and a regulating baffle 62 disposed on the flue gas side of the ammonia cracking module 31, the flue gas bypass regulating mechanism 6 being configured to: dynamically adjust according to load demand and cracking rate set value; under low load conditions, control the regulating baffle 62 to partially open, allowing some high-temperature flue gas to be discharged through the bypass flue 61; under high load conditions, control the regulating baffle 62 to close, allowing all flue gas to pass through the ammonia cracking module 31.

[0030] In this embodiment, the high-temperature exhaust gas generated by the gas turbine 1 is simultaneously used as the heat source for ammonia preheating and ammonia cracking. The ammonia preheater 42 inside the ammonia preheating and supply module 4 collects the waste heat from the exhaust gas of the gas turbine 1 to preheat the liquid ammonia. The ammonia cracking module 31, integrated into the exhaust diffusion section of the gas turbine 1, utilizes the high-temperature flue gas to complete the ammonia cracking reaction. No additional electric heating or fuel oil heating auxiliary heat sources are required throughout the process. On the one hand, the waste heat of the gas turbine 1 is fully recovered, reducing the ship's auxiliary power energy consumption and lowering the ship's self-sustaining energy consumption; on the other hand, the waste heat from the exhaust gas is used to complete fuel pretreatment, significantly reducing the energy consumption for ammonia fuel activation, optimizing the overall thermal efficiency of the main engine module 2 and the gas turbine 1, and adapting to the energy consumption requirements of long-distance voyages.

[0031] In the above embodiments, to ensure the high efficiency and stability of the ammonia cracking module under complex ship operating conditions, the specific formulation of the nickel-based catalyst used in the ammonia cracking module 31 is as follows: Carrier: Selected with a specific surface area of ​​150 m² 2 / g~220 m 2 / g of γ-alumina microspheres were used as catalyst supports to provide sufficient specific surface area for loading active metals.

[0032] Active components and loading: Nickel nitrate is used as the active precursor. After impregnation, drying and calcination, the mass percentage (loading) of nickel (Ni) in the final catalyst is controlled between 15wt% and 25wt%.

[0033] Additives: In order to further suppress the sintering growth of nickel grains in high-temperature exhaust gas and improve the catalyst’s resistance to sulfur poisoning, lanthanum oxide with a mass percentage of 2wt% to 5wt% was also introduced into the above support as an additive.

[0034] Activity temperature window: Under this specific formulation, the above nickel-based catalyst exhibits excellent ammonia cracking activity, and can achieve efficient cracking of ammonia (cracking rate can reach more than 99%) within the temperature range of 450℃~550℃.

[0035] In some embodiments, the air supply module 22 includes a compressor 24, the air outlet of which is connected to the combustion chamber 21.

[0036] In this embodiment, air G enters through the inlet of compressor 24; compressor 24 is added to main module 2, and the outlet of compressor 24 is directly connected to combustion chamber 21, which can continuously supply high-pressure compressed air to combustion chamber 21, providing sufficient pressurized combustion source for ammonia and diesel fuel combustion. Firstly, it can optimize the inlet pressure and flow rate of combustion chamber 21, improve the fuel-air mixing effect, enhance the combustion efficiency of ammonia and diesel fuel, reduce incomplete combustion losses, and improve the working efficiency of gas turbine 1; secondly, the high-pressure stable air supply can avoid the problem of intake fluctuations caused by shipboard turbulence and operating condition switching, stabilize the internal combustion state of combustion chamber 21, prevent flameout and combustion oscillation faults, and further improve the operational reliability of main module 2; thirdly, integrating compressor 24 inside main module 2 results in high integration, eliminating the need for additional external pressurization equipment, simplifying the intake pipeline structure, and saving installation space in the ship's upper compartments.

[0037] In some embodiments, the power supply module 23 includes a turbine 231 connected to the output end of the combustion chamber 21 and a reduction gearbox 232 connected to the output end of the turbine 231, and the output end of the reduction gearbox 232 is connected to the power system 233.

[0038] In this embodiment, the power supply module 23 is sequentially equipped with a turbine 231, a reduction gearbox 232, and a power system 233. The high-temperature and high-pressure gas generated by combustion in the combustion chamber 21 directly acts on the turbine 231, efficiently converting the gas thermal energy into rotational mechanical energy, completing power extraction, shortening the power transmission path, reducing energy loss during transmission, and improving the energy utilization efficiency of the main engine module 2. The gas drives the turbine 231 to output high-speed power, which is then reduced in speed and increased in torque by the reduction gearbox 232 to match the rated operating speed of the marine power system 233. This solves the problem that the turbine 231's output speed is too high and cannot directly drive the ship's power equipment, avoiding overload damage to the power system 233 due to speed mismatch. In addition, the split structure of the step-by-step transmission can buffer the power impact generated by the switching of operating conditions, reduce transmission vibration, and reduce the noise of the ship's power operation. At the same time, each component is independent, which facilitates fault disassembly and repair, reducing the difficulty of operation and maintenance of marine power equipment.

[0039] In some embodiments, an ammonia pump 43 is connected between the liquid ammonia storage tank 41 and the ammonia preheater 42.

[0040] In this embodiment, an ammonia pump 43 is added between the liquid ammonia storage tank 41 and the ammonia preheater 42. The ammonia pump 43 provides the power for transporting liquid ammonia, overcoming pipeline resistance and the back pressure inside the ammonia preheater 42 and the ammonia cracking module 31. This ensures a stable and continuous supply of liquid ammonia from the liquid ammonia storage tank 41 to the ammonia preheater 42, avoiding problems such as ammonia fuel supply interruption or fluctuations due to insufficient supply pressure. At the same time, the ammonia pump 43 can precisely control the liquid ammonia transport flow rate, matching the ammonia supply in real time with the operating load of the gas turbine 1. This prevents ammonia escape due to excessive supply and avoids power output attenuation caused by insufficient supply, ensuring stable ammonia fuel supply and further improving the operational stability of the dual-fuel power system.

[0041] In some embodiments, the ammonia cracking module 31 adopts a compact plate-fin heat exchanger structure, and the inner wall of the ammonia flow channel and the surface of the heat exchange fins of the plate-fin heat exchanger are loaded with a nickel-based catalyst coating for ammonia cracking.

[0042] In this embodiment, the ammonia cracking module 31 adopts a compact plate-fin heat exchanger structure. Compared with the traditional tubular heat exchanger structure, the heat exchange fins significantly increase the heat exchange contact area between flue gas and liquid ammonia, enhance heat transfer efficiency, accelerate the ammonia endothermic cracking rate, improve the cracking efficiency of the ammonia cracking module 31, and ensure sufficient ammonia fuel supply under variable load conditions. This structure is compact and highly integrated, suitable for the limited installation space of the gas turbine 1 exhaust diffuser section, reducing the equipment's footprint and the overall weight of the ship's power equipment. Simultaneously, the plate-fin structure has excellent pressure resistance, able to withstand shipboard vibrations and high-temperature flue gas impacts, and exhibits strong resistance to deformation and fatigue, making it suitable for harsh marine operating conditions. This reduces leakage failures in the ammonia cracking module 31, improves equipment operational reliability, and its high degree of modularity facilitates later maintenance and repair.

[0043] In some embodiments, the heat source acquisition end of the ammonia preheater 42 is located at the high-temperature exhaust gas of the gas turbine 1.

[0044] In this embodiment, the heat source acquisition end of the ammonia preheater 42 is arranged at the high-temperature exhaust gas of the gas turbine 1, which can directly recover and utilize the high-temperature waste heat discharged from the gas turbine 1 without the need for additional auxiliary heating devices such as electric heating or fuel oil heating, thereby reducing the ship's auxiliary energy consumption and improving the waste heat utilization rate of the gas turbine 1. By preheating the liquid ammonia with the high-temperature exhaust gas, the heat exchange load after the liquid ammonia is sent into the ammonia cracking module 31 is reduced, the ammonia heating and cracking time is shortened, and the cracking efficiency of the ammonia cracking module 31 is improved. At the same time, it can reduce external energy consumption, optimize the overall fuel economy of the marine power system, reduce carbon emissions from ship navigation, realize waste heat recycling, and meet the needs of energy-saving operation of ships.

[0045] In some embodiments, the diesel supply module 5 includes a diesel storage tank 51 and a diesel pump 52 connected in sequence, and the output end of the diesel pump 52 is connected to the combustion chamber 21.

[0046] In this embodiment, the diesel supply module 5 is sequentially equipped with interconnected diesel storage tanks 51 and diesel pumps 52. The diesel storage tanks 51 centrally store diesel fuel, ensuring sufficient reserves for marine diesel. The diesel pumps 52 provide stable delivery pressure, overcoming pipeline resistance and smoothly delivering diesel to the combustion chamber 21. Compared to a simple fuel supply structure, this design allows for precise control of diesel fuel flow and pressure, avoiding fuel pulsation and interruptions, and ensuring stable diesel fuel supply. Furthermore, the diesel fuel supply path is independently configured, without interfering with the ammonia fuel supply path. This facilitates independent adjustment of the fuel supply status during operating condition switching, improves the response speed of ammonia-diesel dual-fuel switching, strengthens the power backup capability under extreme conditions, and ensures stable operation of the gas turbine 1.

[0047] See Figures 1 to 2 As shown, in some embodiments, a first nozzle 211 and a second nozzle 212 are connected inside the combustion chamber 21. The first nozzle 211 is connected to the ammonia cracking module 31, and the second nozzle 212 is connected to the output end of the diesel pump 52.

[0048] In this embodiment, a first nozzle 211 and a second nozzle 212 are respectively installed inside the combustion chamber 21 to achieve separate injection of ammonia fuel and diesel fuel. The first nozzle 211 is connected to the ammonia cracking module 31 to specifically deliver cracked ammonia fuel, and the second nozzle 212 is connected to the output end of the diesel pump 52 to specifically deliver diesel fuel. The two fuel injections are independent of each other, completely avoiding the mixing of ammonia and diesel fuel in the pre-pipeline, preventing fuel cross-contamination and pipeline backflow, and avoiding combustion deterioration caused by fuel ratio disorder. Using dedicated nozzles to atomize and inject the two fuels separately can improve the fuel atomization effect, increase the fuel-air contact area, optimize the combustion conditions inside the combustion chamber 21, and improve fuel combustion efficiency. At the same time, the dual-nozzle independent injection structure can independently control the injection sequence and injection flow of the two fuels, accelerate the switching rate between ammonia and diesel fuel, reduce power fluctuations during the switching process, and further improve the stability of the gas turbine 1 under different operating conditions.

[0049] In some embodiments, a nitrogen purging module 7 is further included, the nitrogen purging module 7 including a nitrogen tank 71 and a nitrogen pump 72 connected to the nitrogen tank 71, the nitrogen pump 72 being connected to the combustion chamber 21.

[0050] In this embodiment, a nitrogen purging module 7 is added. A nitrogen tank 71 stores high-pressure nitrogen, which is pressurized by a connected nitrogen pump 72 and then delivered to the combustion chamber 21. Inert nitrogen is used to complete the purging of the pipelines and chambers. During start-up and shutdown, fuel mode switching, and maintenance shutdowns, residual ammonia in the combustion chamber 21 and ammonia fuel delivery pipeline can be purged, preventing corrosion and carbon buildup caused by residual ammonia accumulation, and eliminating the safety hazards of ammonia leakage and combustion explosion. Furthermore, the nitrogen pump 72 can controllably adjust the purging gas flow rate, ensuring a stable and controllable purging operation. It can remove residual impurities from the diesel supply branch, prevent nozzle blockage, and ensure smooth injection from the first nozzle 211 and the second nozzle 212, effectively improving system operational safety and extending the service life of the combustion chamber 21 and fuel pipelines.

[0051] In some embodiments, a chimney 8 is also included, which is connected to the ammonia preheater 42 and the ammonia cracking module 31 respectively.

[0052] In this embodiment, a chimney 8 is added, which is connected to both the ammonia preheater 42 and the ammonia cracking module 31. This centrally collects and discharges the high-temperature flue gas after heat exchange, regulates the system's exhaust flow path, balances the exhaust pressure of the two heat exchange devices, and prevents turbulent flow and pressure interference between the ammonia preheater 42 and the ammonia cracking module 31, thus stabilizing heat exchange conditions. Centralized exhaust optimizes the overall exhaust back pressure of the gas turbine 1, reduces exhaust resistance, lowers exhaust energy consumption, and improves power output efficiency. Simultaneously, it prevents exhaust gas backflow and backflow, avoids high-temperature exhaust gas backflow damaging heat exchange components, reduces the accumulation of ammonia escape gas and combustion exhaust gas inside the ship's cabins, optimizes the ship's cabin environment, and the centralized exhaust structure reduces exhaust temperature, improving the ship's thermal efficiency during navigation.

[0053] Example 2: This invention discloses an ammonia-diesel dual-fuel cycle system for exhaust gas waste heat cracking, including a gas turbine 1, a main engine module 2, an ammonia supply module 3, an ammonia preheating and supply module 4, a diesel supply module 5, and a flue gas bypass regulating mechanism 6. The main engine module 2 includes a combustion chamber 21, an air supply module 22 connected to the combustion chamber 21, and a power supply module 23 connected to the combustion chamber 21. Specifically, the main engine module 2 also includes a compressor 24, the outlet of which is connected to the combustion chamber 21. The compressor 24 and the turbine 231 are coaxially arranged, and air is compressed by the compressor 24 and then sent into the combustion chamber 21. The power supply module 23 includes a turbine 231 and a reduction gearbox 232. The turbine 231 is connected to the output end of the combustion chamber 21, and the output end of the reduction gearbox 232 is connected to the power system 233, realizing the integration of propulsion and power supply. The ammonia supply module 3 includes an ammonia cracking module 31 integrated inside the exhaust diffuser section of the gas turbine 1. The ammonia cracking module 31 employs a compact plate-fin heat exchanger structure. High-temperature exhaust gas flows through the shell side of the cracking module, while ammonia flows through the tube side. The cracking module is filled with a high-performance nickel-based catalyst. Ammonia is cracked into a mixture of hydrogen and nitrogen within a temperature range of 450°C to 550°C. The ammonia cracking module 31 is connected to the combustion chamber 21, and the high-temperature mixture generated by the cracking is fed into the combustion chamber 21 through a first nozzle 211. The ammonia preheating and supply module 4 includes a liquid ammonia storage tank 41 and an ammonia preheater 42 connected to the liquid ammonia storage tank 41. An ammonia pump 43 connects the liquid ammonia storage tank 41 and the ammonia preheater 42. The heat source collection end of the ammonia preheater 42 is located at the high-temperature exhaust gas of the gas turbine 1. The liquid ammonia is pressurized by the ammonia pump 43 and preheated to 350°C to 400°C before being sent to the ammonia cracking module 31 for cracking reaction. The ammonia preheater 42 is connected to the ammonia cracking module 31, and the exhaust gas after heat exchange is discharged through the chimney 8. The diesel supply module 5 includes a diesel storage tank 51 and a diesel pump 52 connected in sequence. The output end of the diesel pump 52 is connected to the combustion chamber 21. A first nozzle 211 and a second nozzle 212 are connected inside the combustion chamber 21. The first nozzle 211 is connected to the ammonia cracking module 31 and is used to inject ammonia cracked gas; the second nozzle 212 is connected to the output end of the diesel pump 52 and is used to inject diesel fuel. The combustion chamber 21 adopts a dual-fuel nozzle design, using ammonia cracked gas as the main fuel and diesel fuel as the auxiliary fuel. The flue gas bypass regulating mechanism 6 includes a bypass flue 61 and a regulating baffle 62 located on the flue gas side of the ammonia cracking module 31. It is dynamically adjusted by the ship's integrated control system according to load demand and the cracking rate setpoint. Under low-load conditions, the regulating baffle 62 is partially opened, allowing some high-temperature flue gas to be directly discharged to the chimney 8 via the bypass flue 61, reducing the cracking rate to maintain combustion stability. Under high-load conditions, the regulating baffle 62 is fully opened, allowing all flue gas to pass through the ammonia cracking module 31, maximizing ammonia fuel utilization.

[0054] The invention also includes a nitrogen purging module 7, comprising a nitrogen tank 71 and a nitrogen pump 72 connected to the nitrogen tank 71, the nitrogen pump 72 being connected to the combustion chamber 21. In the event of an emergency shutdown, the dual fuel supply is simultaneously cut off and the nitrogen purging module 7 is activated to replace the residual combustible gas in the pyrolysis module 31 before discharging it through the chimney 8, preventing the accumulation of combustible gas and potential safety accidents.

[0055] In specific implementation of this invention: In normal working mode: Air is compressed by compressor 24 and enters combustion chamber 21, where it mixes and burns with cracked gas from ammonia cracking module 31 and a small amount of diesel fuel. The resulting high-temperature flue gas drives turbine 231 to perform work. Turbine 231 drives power system 233 via reduction gearbox 232, enabling ship propulsion and power supply. The high-temperature exhaust gas from turbine 231 enters ammonia cracking module 31, providing a heat source for the ammonia cracking reaction. The exhaust gas after heat exchange is discharged through chimney 8.

[0056] Liquid ammonia is pressurized by ammonia pump 43 and then enters ammonia preheater 42. The heat source for preheater 42 is taken from the high-temperature exhaust gas of the gas turbine, preheating the ammonia to approximately 400°C. The preheated ammonia enters cracking module 31, where it undergoes endothermic cracking under the action of a nickel-based catalyst to produce a mixture of hydrogen and nitrogen. This high-temperature cracked gas is directly fed into combustion chamber 21 through first nozzle 211 as the main fuel, co-fueling combustion with a small amount of diesel.

[0057] Startup and Low Load Mode: When the ship starts, diesel fuel is drawn from diesel storage tank 51 by diesel pump 52, and combustion chamber 21 operates in pure diesel mode. Turbine 231 drives compressor 24 and generator to establish circulation. After the temperature of cracking module 31 rises above 450°C, the control system gradually starts ammonia pump 43 to introduce ammonia cracked gas and simultaneously reduces diesel supply until normal operation is achieved. This process is completed automatically by the control system, achieving seamless switching of fuel mode and avoiding the technical problem of difficult pure ammonia start-up.

[0058] Acceleration and Maneuver Modes: When the vessel needs to accelerate rapidly or perform maneuvers, the control system instantly increases the fuel supply of diesel pump 52 according to the throttle command, utilizing the high reactivity of diesel fuel to quickly boost power output. Simultaneously, the control system adjusts the opening of the regulating damper 62 to increase the flue gas flow through the cracking module 31, thereby increasing the production of cracked gas and achieving a rapid, coordinated response from both fuels. This design effectively compensates for the response delay of ammonia cracked gas during rapid changes in operating conditions, ensuring that the transient performance of the power system meets the high maneuverability requirements of the vessel.

[0059] Flue gas bypass regulation: The bypass flue duct 61 and regulating baffle 62 on the flue gas side of the pyrolysis module 31 constitute a flue gas bypass regulation mechanism. Under low-load conditions, some high-temperature flue gas is directly bypassed to the chimney 8, reducing the flue gas flow rate entering the pyrolysis module 31, thereby reducing the pyrolysis rate and maintaining the combustion stability of the combustion chamber. Under high-load conditions, the regulating baffle 62 closes the bypass flue duct 61, and the flue gas passes through the pyrolysis module 31 in its entirety, maximizing the utilization rate of ammonia fuel. This regulation mechanism works in conjunction with dual-fuel proportional control to ensure stable system operation within the 30% to 100% load range.

[0060] Safe shutdown mode: During normal shutdown, the control system first cuts off the ammonia pump 43, and the system switches to pure diesel mode. After the temperature of the pyrolysis module 31 drops to a safe range, the diesel supply is then cut off. In case of emergency shutdown, the dual fuel supply is cut off simultaneously, and the nitrogen purging module 7 is activated to replace the residual combustible gas in the pyrolysis module 31 with gas that is discharged through the chimney 8, preventing the accumulation of combustible gas and potential safety accidents.

[0061] Security Protection Mode: The liquid ammonia storage tank 41 is located in a separate compartment above deck, featuring a double-walled structure and equipped with an ammonia leak detector, an automatic sprinkler system, and an independent ventilation system. The liquid ammonia storage area is physically isolated from the engine room. In the event of an ammonia leak, the control system automatically shuts down the ammonia pump 43, activates the sprinkler dilution system, and issues an alarm signal to notify the crew to take further action. The ammonia cracking module 31, the ammonia preheater 42, and the connecting pipelines are all designed to withstand impact and vibration, meeting the ship's operational requirements in harsh sea conditions.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A dual-fuel cycle system for ammonia and diesel fuel based on waste heat cracking of exhaust gas, characterized in that, include: Gas turbine (1); The main unit module (2) constitutes the body of the gas turbine (1), including a combustion chamber (21), an air supply module (22) connected to the combustion chamber (21), and a power supply module (23) connected to the combustion chamber (21). The ammonia supply module (3) includes an ammonia cracking module (31) integrated inside the exhaust diffusion section of the gas turbine (1), and the ammonia cracking module (31) is connected to the combustion chamber (21); The ammonia preheating and supply module (4) includes a liquid ammonia storage tank (41) and an ammonia preheater (42) connected to the liquid ammonia storage tank (41). The ammonia preheater (42) is connected to the ammonia cracking module (31). A diesel supply module (5) is connected to the combustion chamber (21); The flue gas bypass regulating mechanism (6) includes a bypass flue (61) and a regulating baffle (62) disposed on the flue gas side of the ammonia cracking module (31). The flue gas bypass regulating mechanism (6) is configured to: dynamically adjust according to load demand and cracking rate set value; under low load conditions, control the regulating baffle (62) to partially open, so that some high-temperature flue gas is discharged through the bypass flue (61); under high load conditions, control the regulating baffle (62) to close, so that the flue gas passes through the ammonia cracking module (31) in full.

2. The ammonia-diesel dual-fuel cycle system for waste heat decomposition of exhaust gas according to claim 1, characterized in that, The air supply module (22) includes a compressor (24), the air outlet of which is connected to the combustion chamber (21).

3. The ammonia-diesel dual-fuel cycle system for waste heat decomposition of exhaust gas according to claim 1, characterized in that, The power supply module (23) includes a turbine (231) connected to the output end of the combustion chamber (21) and a reduction gearbox (232) connected to the output end of the turbine (231). The output end of the reduction gearbox (232) is connected to a power system (233).

4. The ammonia-diesel dual-fuel cycle system for waste heat decomposition of exhaust gas according to claim 1, characterized in that, An ammonia pump (43) is connected between the liquid ammonia storage tank (41) and the ammonia preheater (42).

5. The ammonia-diesel dual-fuel cycle system for waste heat cracking of exhaust gas according to claim 1, characterized in that, The ammonia cracking module (31) adopts a compact plate-fin heat exchanger structure, and the inner wall of the ammonia flow channel and the surface of the heat exchange fins of the plate-fin heat exchanger are loaded with a nickel-based catalyst coating for ammonia cracking.

6. The ammonia-diesel dual-fuel cycle system for waste heat decomposition of exhaust gas according to claim 1, characterized in that, The heat source collection end of the ammonia preheater (42) is located at the high-temperature exhaust gas of the gas turbine (1).

7. The ammonia-diesel dual-fuel cycle system for waste heat cracking of exhaust gas according to claim 1, characterized in that, The diesel supply module (5) includes a diesel storage tank (51) and a diesel pump (52) connected in sequence, and the output end of the diesel pump (52) is connected to the combustion chamber (21).

8. The ammonia-diesel dual-fuel cycle system for waste heat cracking of exhaust gas according to claim 7, characterized in that, The combustion chamber (21) is connected to a first nozzle (211) and a second nozzle (212). The first nozzle (211) is connected to the ammonia cracking module (31), and the second nozzle (212) is connected to the output end of the diesel pump (52).

9. The ammonia-diesel dual-fuel cycle system for waste heat cracking of exhaust gas according to claim 1, characterized in that, It also includes a nitrogen purging module (7), which includes a nitrogen tank (71) and a nitrogen pump (72) connected to the nitrogen tank (71), and the nitrogen pump (72) is connected to the combustion chamber (21).

10. The ammonia-diesel dual-fuel cycle system for waste heat cracking of exhaust gas according to claim 1, characterized in that, It also includes a chimney (8), which is connected to the ammonia preheater (42) and the ammonia cracking module (31) respectively.

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