A full near zero emission ammonia fuelled ship hybrid system coupled with a ship end nitrogen production and fresh water production

Abstract

The application discloses a kind of coupling ship end nitrogen preparation and full near-zero emission ammonia fuel ship hybrid power system of fresh water preparation, including liquid ammonia supply and cleavage unit, SOFC / GT main power unit, shipborne membrane separation nitrogen preparation unit, waste heat gradient recovery unit;Liquid ammonia supply and cleavage unit are used to convert into cleavage fuel gas containing H2 And N2 after liquid ammonia is heated by the heat provided by waste heat gradient recovery unit, and the cleavage fuel gas is delivered to SOFC anode;SOFC / GT main power unit includes SOFC, afterburning chamber and gas turbine, SOFC anode tail gas enters afterburning chamber, and afterburning is carried out with oxygen-rich gas generated by shipborne membrane separation nitrogen preparation unit as oxidant;Afterburning chamber exhaust gas is mixed with SOFC cathode nitrogen-rich tail gas after being heated by ammonia cleavage heat supply, and enters gas turbine and expands to work;Waste heat gradient recovery unit carries out gradient recovery power generation to the heat of gas turbine tail gas.The application can realize power output, cogeneration, low NOx control.

Description

Technical Field

[0001] This invention relates to a marine hybrid power system, and more particularly to a near-zero emission ammonia-fueled marine hybrid power system that couples on-board nitrogen and desalination. Background Technology

[0002] Existing ammonia-fueled marine propulsion systems have the following problems:

[0003] First, ammonia fuel systems require large amounts of inert gas for purging, replacement, and positive pressure protection during startup, shutdown, maintenance, and accident isolation. Fuel tanks, valve boxes, double-walled pipe jackets, and some cargo holds or systems also require inerting and low-oxygen protection. Existing shipboard nitrogen generation systems mostly use membrane separation or pressure swing adsorption (PSA) to produce N2 unidirectionally from compressed air, often resulting in underutilization of the oxygen-enriched side gas.

[0004] Secondly, the exhaust gas from the ammonia cracking-SOFC / GT system mainly consists of H2O, N2, and a small amount of O2. Traditional treatment methods typically involve directly discharging this exhaust gas after recovering waste heat, failing to fully utilize the N2 and water vapor resources within it. Furthermore, the low-temperature wet exhaust gas, after being processed through supercritical carbon dioxide and organic Rankine cycles, still possesses a certain amount of sensible heat and latent heat of water vapor condensation. Direct discharge of this gas not only results in the loss of low-temperature waste heat but also weakens the energy self-sufficiency of low-temperature heating scenarios such as domestic hot water, cabin heating, and ammonia safety water preheating. In addition, the residual H2 in the SOFC anode exhaust gas needs to be completely burned in the afterburner. Directly supplying the afterburner with ordinary air would introduce a large amount of N2 into the high-temperature combustion zone, increasing the risk of thermal NOx formation; using pure oxygen combustion would increase the burden on the ship's oxygen storage or production systems. Summary of the Invention

[0005] Addressing the issue that existing ammonia-fueled marine propulsion systems suffer from relatively independent new energy hybrid power systems, onboard nitrogen generation systems, and heating systems, as well as significant nitrogen intake in the high-temperature zone of the ammonia afterburning process, this invention aims to provide a near-zero emission ammonia-fueled marine hybrid power system that couples onboard nitrogen and desalination processes to achieve power output, combined heat and power generation, and low NOx emissions. x control.

[0006] The technical solution of the present invention is as follows: a near-zero emission ammonia fuel ship hybrid power system coupled with ship-end nitrogen and desalination, including a liquid ammonia supply and cracking unit, an SOFC / GT main power unit, a shipboard membrane separation nitrogen generation unit, and a waste heat cascade recovery unit;

[0007] The liquid ammonia supply and cracking unit is used to heat the liquid ammonia with heat provided by the waste heat recovery unit, convert it into cracked fuel gas containing H2 and N2, and then transport the cracked fuel gas to the SOFC anode.

[0008] The SOFC / GT main power unit includes an SOFC, an afterburner, and a gas turbine. The exhaust gas from the SOFC anode and the oxygen-enriched gas generated by the shipboard membrane separation nitrogen generation unit are delivered to the afterburner for combustion. The exhaust gas from the afterburner is ammonia cracking for heating and then enters the gas turbine together with the SOFC cathode exhaust gas to do work.

[0009] The waste heat cascade recovery unit is used to recover waste heat from the afterburner exhaust and gas turbine exhaust in sequence according to the tail gas temperature, and to use the waste heat for ammonia cracking heating, supercritical CO2 cycle power generation and organic Rankine cycle power generation.

[0010] Furthermore, the liquid ammonia supply and cracking unit includes a liquid ammonia pump, a first heat exchanger, a second heat exchanger, a first heater, and a cracker. The waste heat recovery unit includes a supercritical CO2 cycle power generation system. The supercritical CO2 cycle power generation system uses the exhaust gas from the gas turbine as a heat source. After being pressurized by the liquid ammonia pump, the liquid ammonia absorbs the heat of the circulating working fluid of the supercritical CO2 cycle power generation system in the first heat exchanger, then absorbs the sensible heat of the cracked fuel gas discharged from the cracker in the second heat exchanger, and finally enters the cracker for cracking after passing through the first heater. The liquid ammonia sequentially absorbs the waste heat of the supercritical CO2 cycle and the sensible heat of the cracked gas, achieving staged preheating and reducing external heating energy consumption.

[0011] Furthermore, the supercritical CO2 cycle power generation system includes a third heat exchanger, a CO2 turbine, a first splitter, a cooler, a first CO2 compressor, a second CO2 compressor, and a second mixer. The exhaust gas from the gas turbine enters the third heat exchanger as the heat source for the supercritical CO2 cycle. The exhaust gas from the CO2 turbine is split into two paths by the first splitter. One path passes through the first heat exchanger for heat exchange and then enters the first CO2 compressor for pressurization via the cooler. The other path directly enters the second CO2 compressor for pressurization. The circulating working fluid after being pressurized by the first and second CO2 compressors is mixed by the second mixer and then enters the third heat exchanger for heat absorption. By employing a split-flow recompression supercritical CO2 cycle, compression power consumption is reduced. Simultaneously, the circulating working fluid is used to preheat liquid ammonia, achieving waste heat recovery and ammonia vaporization heat coupling.

[0012] Furthermore, the waste heat recovery unit includes an organic Rankine cycle power generation system. This system comprises a fourth heat exchanger, a turbine, a condenser, and a working fluid pump. The pressurized organic working fluid from the working fluid pump exchanges heat with the exhaust gas from the gas turbine after passing through the supercritical CO2 cycle power generation system in the fourth heat exchanger. The fluid then passes through the turbine and condenser before returning to the working fluid pump, forming a cycle. Utilizing the waste heat from the low-to-medium grade exhaust gas after the supercritical CO2 cycle drives the organic Rankine cycle power generation, further recovering waste heat and improving the overall power generation efficiency of the system.

[0013] Furthermore, the shipborne membrane separation nitrogen generation unit includes a second air compressor, an aftercooler dewatering unit, an air preprocessor, and a membrane separation nitrogen generator connected in sequence, with the nitrogen-rich gas from the membrane separation nitrogen generator connected to the ship's N2 main pipe.

[0014] Furthermore, the oxygen-enriched gas from the membrane separation nitrogen generator is heated by a second heater and then introduced into the afterburner, serving as the oxidant for afterburning the SOFC anode tail gas.

[0015] Furthermore, the system includes a dryer where a portion of the low-temperature wet exhaust gas, after waste heat recovery in a cascade manner, is condensed, dehydrated, and dried to form nitrogen-rich inert gas. This nitrogen-rich inert gas is then combined with the nitrogen-rich gas generated by the membrane nitrogen generator and connected to the ship's N2 main pipeline. The nitrogen recovered from the exhaust gas is dried and mixed with the nitrogen-rich gas from the membrane nitrogen generator, increasing the nitrogen supply at the ship's end, reducing the load on the membrane nitrogen generator, and achieving closed-loop utilization of nitrogen resources.

[0016] Furthermore, the system includes a condensate separator connected before the dryer. A portion of the low-temperature, wet exhaust gas, after waste heat recovery, enters the condensate separator for condensation and dehydration. The condensate obtained from the exhaust gas is further treated and used as a usable freshwater resource for the ship. By condensing and recovering water vapor from the exhaust gas, and then treating it as freshwater for the ship, the system improves the ship's self-sufficiency in water supply and reduces the need for freshwater replenishment.

[0017] Furthermore, it includes a second distributor connected before the condensate separator. The low-temperature wet exhaust gas after waste heat recovery enters the second distributor. The exhaust gas from the gas turbine is split in the second distributor, with part of the exhaust gas used for heating and the other part entering the condensate separator.

[0018] Furthermore, the ratio of the exhaust gas diverted by the second distributor for heating to the exhaust gas entering the condensate dehydrator is 5:1 to 1:1. This balances the needs for low-temperature heating, exhaust gas N2 recovery, and condensation for desalination, reducing the scale and operating costs of the treatment system.

[0019] Compared with the prior art, the advantages of the technical solution of the present invention are as follows:

[0020] (1) This invention aims at near-zero emissions from ammonia-fueled ships, utilizing the carbon-free and sulfur-free characteristics of ammonia fuel to reduce CO2 and SO2 emissions at the ship's end. x Zero emissions, and NO reduction through oxygen-enriched afterburning. x This potential generates a systemic foundation for near-zero emission operation of ocean-going vessels.

[0021] (2) The present invention constructs an ammonia fuel cogeneration hybrid power system with liquid ammonia cracking-SOFC / GT as the main power source, supercritical carbon dioxide cycle and organic Rankine cycle as the bottom cycle, and terminal low temperature heating as a supplement, so as to realize the coordinated operation of power output, gas turbine power generation, waste heat power generation and low temperature heating.

[0022] (3) The present invention adopts the energy utilization method of "temperature matching and step-by-step utilization", which uses the high temperature heat of the afterburner for ammonia cracking heating, the medium and high grade waste heat for supercritical carbon dioxide cycle power generation, the medium and low grade waste heat for organic Rankine cycle power generation, and the terminal low temperature wet tail gas for low temperature heating, tail gas N2 recovery and condensation desalination, thereby improving the comprehensive utilization efficiency of fuel.

[0023] (4) The present invention adopts a gas organization method of oxygen-enriched afterburning and nitrogen-enriched aftermixing. The oxygen-enriched gas generated by the shipborne membrane separation nitrogen generation unit is used for anode tail gas afterburning. At the same time, the nitrogen-enriched tail gas of the solid oxide fuel cell cathode bypasses the afterburning chamber and is mixed into the gas turbine inlet downstream of the afterburning chamber, thereby reducing the amount of nitrogen entering the high-temperature reaction zone of the afterburning chamber and maintaining the working fluid flow rate of the gas turbine.

[0024] (5) The present invention expands the shipborne membrane separation nitrogen generation unit from a single N2 supply device to a dual product utilization unit of oxygen-enriched gas and nitrogen-enriched gas. The oxygen-enriched gas is used for afterburning, and the nitrogen-enriched gas is connected to the ship's N2 main pipe or N2 buffer storage component, and together with the nitrogen-enriched inert gas recovered from the exhaust gas, it forms a closed-loop N2 supply system at the ship's end.

[0025] (6) This invention integrates exhaust gas N2 recovery, exhaust gas condensation for desalination and terminal low-temperature heating into an exhaust gas resource utilization path, so that the gas phase nitrogen-rich inert gas can be used for ship purging, inerting, positive pressure protection and emergency replacement, the liquid phase condensate can be treated and used for ship technical water, domestic miscellaneous water or ammonia safety water, and the low-temperature heat can be used for domestic hot water, cabin heating or technical heat, thereby improving the self-sufficiency of nitrogen, water and heat supply of ocean-going ammonia fuel ships.

[0026] (7) This invention provides a multi-stage heat-mass synergistic utilization path from fuel conversion, main power output, waste heat power generation, low temperature heating to exhaust gas resource utilization through high-temperature exhaust gas from the afterburner, ammonia cracking reaction heat, gas turbine expansion work, supercritical carbon dioxide cycle power generation, organic Rankine cycle power generation, exhaust gas end low temperature heating, and exhaust gas N2 / water resource treatment. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the near-zero emission ammonia-fueled ship hybrid power system coupled with onboard nitrogen and desalination in an embodiment of the present invention. Detailed Implementation

[0028] The present invention will be further described below with reference to embodiments, but these are not intended to limit the scope of the invention.

[0029] Please combine Figure 1 As shown in the embodiment of the present invention, the near-zero emission ammonia-fueled marine hybrid power system with coupled onboard nitrogen and desalination includes a liquid ammonia pump 1, a first heat exchanger 2, a second heat exchanger 3, a first heater 4, a pyrolyzer 5, a solid oxide fuel cell 6, an inverter 7, a first air compressor 8, an afterburner 9, a second heater 10, a first mixer 11, a gas turbine 12, a third heat exchanger 13, a CO2 turbine 14, a first distributor 15, a cooler 16, a first CO2 compressor 17, a second CO2 compressor 18, a second mixer 19, a fourth heat exchanger 20, a turbine 21, a condenser 22, a working fluid pump 23, a second distributor 24, a condensate dehydrator 25, a dryer 26, a third mixer 27, a second air compressor 28, an aftercooler dehydrator 29, an air pre-processor 30, and a membrane separation nitrogen generator 31.

[0030] The second air compressor 28, the aftercooler 29, the air pre-processor 30, and the membrane separation nitrogen generator 31 constitute the shipboard membrane separation nitrogen generation unit. Air is pressurized by the second air compressor 28 and then enters the aftercooler 29 to cool and separate the condensate produced during compression. It then enters the air pre-processor 30 to remove droplets, oil mist, particulate matter, and residual moisture from the air. The pre-treated compressed air enters the membrane separation nitrogen generator 31, where membrane separation produces two products: oxygen-rich and nitrogen-rich gas. The oxygen-rich gas enters the afterburner 9 via the second heater 10, while the nitrogen-rich gas is connected to the third mixer 27 or the ship's N2 main pipe, thus enabling the utilization of both oxygen-rich and nitrogen-rich products from the shipboard membrane separation nitrogen generation unit.

[0031] The connections of the aforementioned components constitute a liquid ammonia supply and cracking unit, an SOFC / GT main power unit, a shipboard membrane separation nitrogen generation unit, an oxygen-enriched afterburning and nitrogen-enriched aftermixing gas organization unit, a waste heat cascade recovery unit, a cryogenic heating utilization unit, a tail gas N2 recovery and storage unit, and a tail gas condensation desalination unit. The entire system operates along the path of "liquid ammonia pressurization and vaporization—ammonia cracking for hydrogen supply—SOFC power generation—anode tail gas oxygen-enriched afterburning—cathode nitrogen-enriched tail gas aftermixing—gas turbine expansion for power generation—SCO2 / ORC cascade waste heat power generation—tail gas terminal cryogenic heating—tail gas N2 recovery—tail gas condensation desalination," thus forming a multi-functional coupled marine hybrid power system integrating power, heat, electricity, nitrogen, and water.

[0032] The liquid ammonia supply and cracking unit includes a liquid ammonia pump 1, a first heat exchanger 2, a second heat exchanger 3, a first heater 4, and a cracker 5. Liquid ammonia is supplied from a cryogenic liquid ammonia storage tank, first entering the liquid ammonia pump 1 and being pressurized to the required system pressure, then entering the first heat exchanger 2. In the first heat exchanger 2, the liquid ammonia absorbs heat released from the supercritical CO2 circulation branch, completing vaporization and initial preheating. Subsequently, the gaseous ammonia enters the second heat exchanger 3, where it exchanges heat with the high-temperature 5:1 H2 / N2 cracked gas at the outlet of the cracker 5 and is further heated. The ammonia, heated by the second heat exchanger 3, enters the first heater 4 for reheating, and then enters the cracker 5 to undergo an ammonia cracking reaction, generating cracked fuel gas mainly composed of H2 and N2. The high-temperature cracked fuel gas at the outlet of the cracker 5 returns to the second heat exchanger 3 to release sensible heat, and then enters the anode side of the SOFC 6 to participate in the electrochemical reaction.

[0033] The SOFC / GT main power unit includes SOFC6, inverter 7, first air compressor 8, afterburner 9, second heater 10, first mixer 11, and gas turbine 12. Air is compressed by the first air compressor 8 and enters the cathode side of SOFC6, where oxygen participates in the electrochemical reaction. The nitrogen-rich exhaust gas discharged from the cathode side bypasses the afterburner 9 and serves as part of the inlet working fluid for the subsequent gas turbine 12. The H2 / N2 cracked fuel gas generated by the pyrolyzer 5 enters the anode side of SOFC6, where H2 reacts electrochemically with oxygen ions conducted from the cathode side to the anode side via the electrolyte, producing direct current. N2, as an inert accompanying component, is discharged with the anode stream.

[0034] The anode exhaust gas from the SOFC6 anode enters the aftercombustion chamber 9 without N2 separation. Since the anode exhaust gas contains unreacted H2 and N2 introduced from ammonia cracking, this portion of N2 enters the aftercombustion chamber 9 along with the residual combustible components. The oxygen-enriched gas produced by the membrane separator nitrogen generator 31 is heated by the second heater 10 and then enters the aftercombustion chamber 9 as an aftercombustion oxidant, ensuring the complete oxidation of the residual combustible components in the anode exhaust gas. Compared to directly using ordinary air as the aftercombustion oxidant, using the oxygen-enriched gas produced by the membrane separator nitrogen generator 31 reduces the amount of N2 entering the high-temperature reaction zone of the aftercombustion chamber 9, thereby reducing the amount of thermal NO during aftercombustion. x Its generation potential.

[0035] The high-temperature gas exiting the afterburner 9 enters the first mixer 11 and mixes with the nitrogen-rich exhaust gas discharged from the SOFC 6 cathode, forming the working fluid at the inlet of the gas turbine 12. The first heater 4 can utilize the system's high-temperature waste heat, the gas turbine exhaust gas waste heat, or an external heat source to supplement the heat of the ammonia working fluid before it enters the cracker 5. Thus, while reducing the amount of nitrogen entering the high-temperature reaction zone of the afterburner 9, the system maintains the inlet working fluid flow of the gas turbine 12 through the aftermixing of the nitrogen-rich exhaust gas from the cathode. The mixed high-temperature gas enters the gas turbine 12, expands, and performs work, constituting the main power output of the SOFC / GT.

[0036] The waste heat recovery unit includes a supercritical CO2 cycle power generation system and an organic Rankine cycle power generation system. The supercritical CO2 cycle power generation system includes a third heat exchanger 13, a CO2 turbine 14, a first distributor 15, a cooler 16, a first CO2 compressor 17, a second CO2 compressor 18, and a second mixer 19. The high-temperature exhaust gas from the gas turbine 12 first enters the third heat exchanger 13, serving as a high-grade heat source for the supercritical CO2 cycle. The CO2 working fluid, after being compressed by the first CO2 compressor 17 and the second CO2 compressor 18 respectively, merges in the second mixer 19 and then enters the third heat exchanger 13 to absorb heat from the exhaust gas from the gas turbine 12. The heated, high-temperature, high-pressure CO2 enters the CO2 turbine 14 for expansion and work. The working fluid exiting the CO2 turbine 14 enters the first distributor 15, with a portion flowing to the first heat exchanger 2 for liquid ammonia vaporization and preheating, then cooled by the cooler 16 before entering the first CO2 compressor 17; the other portion enters the second CO2 compressor 18 to form a recompression branch. Therefore, the supercritical CO2 cycle not only recovers the medium and high grade waste heat from the exhaust gas of the gas turbine 12, but also forms a thermal coupling with the liquid ammonia gasification preheating process.

[0037] The organic Rankine cycle power generation system includes a fourth heat exchanger 20, a turbine 21, a condenser 22, and a working fluid pump 23. After releasing some high-temperature heat in the third heat exchanger 13, the exhaust gas from the gas turbine 12 continues into the fourth heat exchanger 20, serving as a medium-to-low-grade heat source for the organic Rankine cycle. The organic working fluid, pressurized by the working fluid pump 23, enters the fourth heat exchanger 20 to absorb heat and vaporize, then enters the turbine 21 to expand and perform work. The working fluid exiting the turbine 21 enters the condenser 22 and condenses into a liquid state, then returns to the working fluid pump 23, completing the closed-loop organic Rankine cycle. This cycle is used to further recover the remaining medium-to-low-grade waste heat after the supercritical CO2 cycle.

[0038] This cycle, together with the supercritical CO2 cycle, constitutes the bottom cycle power generation unit, enabling the main power system to be expanded from a single SOFC / GT power generation system to a SOFC / GT-SCO2 / ORC composite power generation system.

[0039] The exhaust gas N2 recovery and storage unit and the exhaust gas condensation and desalination unit include a condenser 25, a dryer 26, a third mixer 27, and corresponding water treatment components and a branch line for ship water storage. The exhaust gas from the gas turbine 12 sequentially passes through the third heat exchanger 13 and the fourth heat exchanger 20 for staged waste heat recovery before entering the second distributor 24. The second distributor 24 divides the exhaust gas into low-temperature heating branch exhaust gas and resource recovery branch exhaust gas. The exhaust gas is further cooled by the low-temperature heating utilization unit and discharged from the exhaust gas outlet, while the resource recovery exhaust gas enters the condenser 25. The condenser 25 condenses and separates the water vapor in the low-temperature wet exhaust gas. The resulting liquid condensate is treated and then enters the ship water storage branch line, while the resulting gas phase enters the dryer 26 for deep dehydration to form nitrogen-rich inert gas.

[0040] In this embodiment, the preferred exhaust gas resource recovery ratio is 25%. This ratio does not mean that the remaining exhaust gas is directly wasted, but rather it is determined after comprehensively considering the ship's inert gas requirements, condensation desalination requirements, water treatment costs, water storage space, and low-temperature heating utilization. If all exhaust gas were sent to the exhaust gas N2 recovery and storage unit and the exhaust gas condensation desalination unit, the output of condensate and nitrogen-rich inert gas would be significantly higher than the daily requirements of most target ship types, while also increasing the scale and operating costs of condensation dewatering, filtration, activated carbon adsorption, pH adjustment, disinfection, water storage, and gas storage systems. Therefore, in this embodiment, 25% of the exhaust gas is used for N2 recovery and condensation desalination, and the remaining 75% is used for low-temperature heating utilization. In actual ship applications, this ratio can be adjusted according to inert gas requirements, fresh water requirements, and low-temperature heat load. Generally, the ratio of exhaust gas used for low-temperature heating utilization to that used for N2 recovery and condensation desalination is 5:1 to 1:1.

[0041] In this embodiment, the resource-recovered exhaust gas entering the condensate dehydrator 25 releases latent heat and sensible heat during the condensation and dehydration process. This heat can be recovered through the cooling water circuit or heat exchanger and used as a source of low-temperature heating for the ship. Simultaneously, the exhaust gas discharged from the second distributor 24 is further cooled to 25–35°C or near the return water temperature for low-temperature heat users before discharge, and the released low-temperature heat is used for domestic hot water, cabin heating, ammonia safety water preheating, equipment cleaning water heating, or other low-temperature technology heating. Therefore, the exhaust gas end-of-pipe cooling process is not only used for exhaust gas N2 recovery and condensation for desalination, but also serves as a low-temperature heating link in the cogeneration system.

[0042] The condensate obtained by the condenser 25 can be treated through processes such as demisting, filtration, pH adjustment, activated carbon adsorption, disinfection, or mineralization before being used as technical water for ships, domestic waste water, ammonia leak absorption water, wet scrubber makeup water, water supply for water curtain systems, equipment cleaning water, or cooling makeup water. Thus, water vapor in the exhaust gas is no longer directly emitted as a component of the waste gas, but is transformed into usable freshwater resources for ships through condensation desalination and water treatment. It should be noted that in this embodiment, desalination refers to the production and treatment of exhaust gas condensate, and is not limited to seawater desalination.

[0043] The gas phase exiting dryer 26 is nitrogen-rich inert gas. This nitrogen-rich inert gas undergoes oxygen content, dew point, and necessary NO testing. x After monitoring NH3 and H2 and confirming that the preset inerting gas requirements are met, the gas enters the third mixer 27. The third mixer 27 also receives nitrogen-rich gas produced by the membrane separator nitrogen generator 31. The two are mixed and output as ship inerting gas, which is then connected to the ship's N2 main pipeline or N2 buffer storage components. Ship inerting gas can be used for ammonia fuel system purging, pyrolysis and pipeline replacement, fuel tank inerting, valve box positive pressure protection, cargo hold inerting, instrument protection, or emergency replacement, realizing the transformation of exhaust N2 from an emission component into a functional resource for the ship.

[0044] In this embodiment, both the oxygen-enriched and nitrogen-enriched gases generated by the membrane separation nitrogen generator 31 are utilized in situ. The oxygen-enriched gas enters the afterburner 9 via the second heater 10 for oxygen-enriched afterburning of the anode tail gas; the nitrogen-enriched gas enters the third mixer 27 and is mixed with the nitrogen-enriched inert gas recovered by the tail gas N2 recovery and storage unit before being supplied to the ship's N2 main pipeline. Thus, the shipborne membrane separation nitrogen generator unit and the tail gas N2 recovery and storage unit together constitute a closed-loop N2 supply system, transforming the nitrogen supply of the ship's ammonia fuel system from the traditional "one-way production - one-way consumption" to a closed-loop management mode of "membrane nitrogen generation and supply - tail gas N2 recovery - ship's N2 main pipeline supply".

[0045] As can be seen from the above connections, this invention integrates liquid ammonia cracking, SOFC power generation, oxygen-enriched afterburning, nitrogen-enriched aftermixing, gas turbine expansion for power generation, supercritical CO2 cycle power generation, organic Rankine cycle power generation, tail gas end-of-pipe low-temperature heating, tail gas N2 recovery, and tail gas condensation for desalination into a single system. High-temperature heat is preferentially used for ammonia cracking and gas turbine power generation; medium- and high-grade waste heat is used for the supercritical CO2 cycle; medium- and low-grade waste heat is used for the organic Rankine cycle; and the end-of-pipe low-temperature wet tail gas is used for low-temperature heating, N2 recovery, and condensation for desalination, thus forming an integrated resource coupling system for ammonia-fueled ships with hybrid power, nitrogen supply, water supply, and heating, oriented towards near-zero emissions.

[0046] The following is a simulation example of a near-zero emission ammonia-fueled marine hybrid power system coupled with onboard nitrogen production and desalination, used to verify the feasibility of the invention in terms of main power output, waste heat cascade power generation, cryogenic heating, N2 closed-loop supply and desalination via exhaust gas condensation.

[0047] Table 1 System Initial Conditions

[0048]

[0049] Based on the initial system conditions in Table 1, a system simulation was performed, and the results are shown in Table 2.

[0050] Table 2 Main Simulation Results of the System

[0051]

[0052] To further illustrate the technical effects of the oxygen-enriched afterburning-nitrogen-enriched aftermixing gas organization method in this invention, a comparative example was set up without the oxygen-enriched afterburning-nitrogen-enriched aftermixing optimization, under the same conditions of liquid ammonia inlet flow rate, total air inlet flow rate, SOFC operating temperature and pressure, circulating working fluid, and main equipment efficiency. The comparative example still used liquid ammonia cracking, SOFC / GT, and waste heat circulation structure, but did not employ SOFC anode and cathode tail gas separation. The SOFC cathode nitrogen-enriched tail gas did not bypass the afterburner and be mixed into the GT inlet as in this invention; instead, it directly entered the afterburner as an afterburning oxidant. The main simulation results of the examples and comparative examples are shown in Table 3.

[0053] Table 3. Main simulation results of the systems in the examples and comparative examples.

[0054]

[0055] As shown in Table 3, under the same liquid ammonia inlet flow rate and SOFC operating conditions, the SOFC output power of the embodiment and the comparative example is basically the same, indicating that the two schemes are comparable in terms of the main power generation capacity of the fuel cell. After adopting the oxygen-enriched afterburning-nitrogen-enriched aftermixed gas organization mode, the gas turbine output power of the embodiment increased from about 5086 kW in the comparative example to about 5564.1 kW, the supercritical CO2 cycle power generation increased from about 978 kW to about 1046.6 kW, the organic Rankine cycle power generation increased from about 85 kW to about 200.1 kW, and the total system power generation increased from about 17586.9 kW to about 18248.7 kW.

[0056] Meanwhile, the total compression and pump power consumption of the embodiment is approximately 2466.4 kW, lower than the approximately 2891 kW of the comparative example. Therefore, the net power generation of the embodiment system is approximately 15782.3 kW, while the net power generation of the comparative example system is approximately 14695.9 kW. Calculated using the lower heating value of liquid ammonia, the net power generation efficiency of the embodiment is approximately 74.7%, while the net power generation efficiency of the comparative example is approximately 69.6%, representing an improvement of approximately 5.1 percentage points. These results indicate that the use of an oxygen-enriched afterburning-nitrogen-enriched aftermixing method can not only optimize the gas organization in the afterburner but also improve the overall output of the gas turbine and bottom cycle, and reduce the proportion of power consumption by auxiliary equipment.

[0057] Looking at the composition of the afterburner outlet, in the comparative example, a large amount of N2 enters the high-temperature reaction zone of the afterburner, with an N2 flow rate of approximately 967.66 kmol / h at the outlet. However, in this embodiment, the nitrogen-rich exhaust gas from the SOFC cathode bypasses the afterburner and mixes with the afterburner exhaust gas downstream, reducing the N2 flow rate at the outlet to approximately 155.75 kmol / h. This is due to the thermal NO... x NOx formation is closely related to N2 concentration, O2 concentration, and residence time in the high-temperature zone. The examples significantly reduced the chance of N2 participating in NOx formation in the high-temperature zone of the afterburner. (Based on NO...) x Converted to NO2 equivalent, the NO in the example x The emission intensity is approximately 7.6 × 10⁻⁶. -9 The NO content in the aftercombustion chamber is approximately 0.0509 g / kWh, compared to approximately 0.0509 g / kWh in the comparative example. This indicates that the present invention can significantly reduce NO in the aftercombustion chamber while ensuring complete combustion of residual combustible components in the anode exhaust gas. x Generation potential.

[0058] This embodiment also possesses shipboard nitrogen and desalination capabilities and exhaust gas resource recovery capabilities not found in the comparative example. After being processed by a gas turbine, supercritical CO2 cycle, and organic Rankine cycle, the low-temperature wet exhaust gas still contains a significant amount of H2O and N2. Introducing 25% of the low-temperature wet exhaust gas into the resource recovery branch yields approximately 35.6 t / d of theoretical condensate. Considering losses from demisting, filtration, pH adjustment, activated carbon adsorption, disinfection, and storage, approximately 33 t / d of usable freshwater can still be obtained. The gas phase is dried to form nitrogen-rich inert gas, which is then combined with the nitrogen-rich gas produced by the membrane separator nitrogen generator 31 in the third mixer 27, ultimately yielding approximately 7003 Nm³. 3 The system produces a nitrogen-rich inert gas per hour, with an N2 volume fraction of approximately 96.11% and an O2 volume fraction of approximately 3.89%. This mixture can be connected to the ship's N2 main pipeline for ammonia fuel system purging, fuel tank inerting, valve box positive pressure protection, cargo hold inerting, instrument protection, or emergency replacement. Fresh water can be supplied to the ship's water storage branch line for technical water, domestic miscellaneous water, ammonia safety water, equipment cleaning water, or cooling water makeup.

[0059] The cogeneration efficiency of this embodiment is calculated as the ratio of the sum of the system's net power generation and usable heat supply to the lower heating value of the fuel input. The liquid ammonia inlet flow rate is 240 kmol / h, and based on the lower heating value of NH3, the fuel input power is approximately 21,120 kW; the net power generation of the system in this embodiment is approximately 15,782.3 kW. If the low-temperature heat released during the exhaust gas terminal cooling process is considered as usable ship heating, including the heat released during the condensation, dehydration, and desalination of 25% of the resource-recovered exhaust gas, and the heat released during the further cooling of 75% of the exhaust gas to 25–35°C or near the return water temperature of low-temperature heat users, then the theoretical heat supply at the exhaust gas terminal is approximately 4,774 kW. Taking the effective utilization coefficient of low-temperature heat as 0.5, the effective low-temperature heat supply is approximately 2,387 kW. Therefore, the cogeneration efficiency of this embodiment is approximately 86.0%. Thus, this system not only enables both main power generation and waste heat power generation, but also enhances the resource self-sufficiency of ocean-going vessels through low-temperature heating, N2 recovery, and desalination. Considering that the condensate also needs to undergo filtration, pH adjustment, activated carbon adsorption, disinfection and storage, and that all treatments may result in redundant production of technical water and inert gas, this embodiment adopts a diversion scheme of 25% exhaust gas resource utilization and 75% exhaust gas low-temperature heating, and the exhaust gas resource utilization ratio can be adjusted according to the needs of the ship.

[0060] Therefore, this invention enables the coordinated operation of ammonia cracking for hydrogen supply, high-efficiency SOFC power generation, oxygen-enriched afterburning, nitrogen-enriched aftermixing, gas turbine expansion for power generation, waste heat cascade power generation, low-temperature heating utilization, exhaust gas N2 recovery, and exhaust gas condensation for desalination in an ammonia-fueled SOFC / GT hybrid power system. Compared to a comparative example without this gas organization method and exhaust gas resource utilization pathway, this invention improves the system's net power generation efficiency and reduces NO in the afterburner. x The system generates potential and converts N2 and H2O from exhaust gas into ship inert gas and usable freshwater resources, respectively. It is suitable for medium to large-sized chemical tankers, liquid ammonia carriers, LPG carriers, oil tankers, and ammonia-fueled ships with high requirements for inerting, technical water, and cryogenic heating, oriented towards ocean voyages. Under current simulation conditions, the system's ship-side CO2 and SO2 emissions are... x Zero emissions, NO x With near-zero emissions, it has the potential for near-zero emission operation and good engineering application value.

Claims

1. A near-zero emission ammonia-fueled marine hybrid power system coupled with onboard nitrogen and desalination production, characterized in that, This includes a liquid ammonia supply and cracking unit, an SOFC / GT main power unit, a shipboard membrane separation nitrogen generation unit, and a waste heat cascade recovery unit. The liquid ammonia supply and cracking unit is used to heat the liquid ammonia with heat provided by the waste heat recovery unit, convert it into cracked fuel gas containing H2 and N2, and then transport the cracked fuel gas to the SOFC anode. The SOFC / GT main power unit includes an SOFC, an afterburner, and a gas turbine. The exhaust gas from the SOFC anode and the oxygen-enriched gas generated by the shipboard membrane separation nitrogen generation unit are delivered to the afterburner for combustion. The exhaust gas from the afterburner is ammonia cracking for heating and then enters the gas turbine together with the SOFC cathode exhaust gas to do work. The waste heat cascade recovery unit is used to recover waste heat from the afterburner exhaust and gas turbine exhaust in sequence according to the tail gas temperature, and to use the waste heat for ammonia cracking heating, supercritical CO2 cycle power generation and organic Rankine cycle power generation.

2. The near-zero emission ammonia-fueled marine hybrid power system with coupled end-of-ship nitrogen and desalination as described in claim 1, characterized in that, The liquid ammonia supply and cracking unit includes a liquid ammonia pump, a first heat exchanger, a second heat exchanger, a first heater, and a cracker. The waste heat cascade recovery unit includes a supercritical CO2 cycle power generation system. After being pressurized by the liquid ammonia pump, the liquid ammonia absorbs the heat of the circulating working fluid of the supercritical CO2 cycle power generation system in the first heat exchanger, absorbs the sensible heat of the cracked fuel gas discharged from the cracker in the second heat exchanger, and then enters the cracker for cracking after passing through the first heater.

3. The near-zero emission ammonia-fueled marine hybrid power system with coupled end-of-ship nitrogen and desalination as described in claim 2, characterized in that, The supercritical CO2 cycle power generation system includes a third heat exchanger, a CO2 turbine, a first distributor, a cooler, a first CO2 compressor, a second CO2 compressor, and a second mixer. The exhaust gas from the gas turbine releases heat to the supercritical CO2 cycle working fluid in the third heat exchanger. The supercritical CO2 cycle working fluid, after absorbing heat, enters the CO2 turbine to expand and perform work. The exhaust gas from the CO2 turbine is divided into two paths by the first distributor. One path passes through the first heat exchanger for heat exchange and then enters the first CO2 compressor for pressurization through the cooler. The other path directly enters the second CO2 compressor for pressurization. The cycle working fluids pressurized by the first and second CO2 compressors are mixed by the second mixer and then enter the third heat exchanger to absorb heat.

4. The near-zero emission ammonia-fueled marine hybrid power system coupled with onboard nitrogen and desalination as described in claim 2, characterized in that, The waste heat recovery unit includes an organic Rankine cycle power generation system, which includes a fourth heat exchanger, a turbine, a condenser, and a working fluid pump. The pressurized organic working fluid is exchanged for heat with the exhaust gas from the gas turbine after passing through the supercritical CO2 cycle power generation system in the fourth heat exchanger, and then returns to the working fluid pump after passing through the turbine and condenser to form a cycle.

5. The near-zero emission ammonia-fueled marine hybrid power system with coupled end-of-ship nitrogen and desalination as described in claim 1, characterized in that, The shipborne membrane separation nitrogen generation unit includes a second air compressor, an aftercooler dewatering unit, an air preprocessor, and a membrane separation nitrogen generator connected in sequence. The nitrogen-rich gas from the membrane separation nitrogen generator is connected to the ship's N2 main pipe.

6. The near-zero emission ammonia-fueled marine hybrid power system with coupled end-of-ship nitrogen and desalination as described in claim 5, characterized in that, The oxygen-enriched gas from the membrane separation nitrogen generator is heated by a second heater and then introduced into the afterburner, serving as the oxidant for afterburning the SOFC anode tail gas.

7. The near-zero emission ammonia-fueled marine hybrid power system with coupled end-of-ship nitrogen and desalination as described in claim 5, characterized in that, The system includes a dryer, where a portion of the low-temperature wet exhaust gas, after waste heat recovery in stages, is condensed, dehydrated, and dried to form a nitrogen-rich inert gas. This nitrogen-rich inert gas is then combined with the nitrogen-rich gas generated by the membrane separator nitrogen generator and connected to the ship's N2 main pipeline.

8. The near-zero emission ammonia-fueled marine hybrid power system coupled with onboard nitrogen and desalination as described in claim 7, characterized in that, It includes a condensate separator connected before the dryer. A portion of the low-temperature wet exhaust gas after waste heat recovery enters the condensate separator for condensation and dehydration. The exhaust gas condensate obtained by the condensate separator is further treated and used as a freshwater resource for the ship.

9. The near-zero emission ammonia-fueled marine hybrid power system with coupled end-of-ship nitrogen and desalination as described in claim 8, characterized in that, It includes a second distributor connected before the condensate precipitator. The low-temperature wet exhaust gas after waste heat recovery enters the second distributor. The exhaust gas of the gas turbine is separated in the second distributor, with part of the exhaust gas used for heating and the other part of the exhaust gas entering the condensate precipitator.

10. The near-zero emission ammonia-fueled marine hybrid power system coupled with onboard nitrogen and desalination as described in claim 9, characterized in that, The ratio of the exhaust gas diverted by the second distributor for heating to the exhaust gas entering the condensate dewatering unit is 5:1 to 1:1.

Images