LNG-powered ship energy integrated utilization system based on oxygen-enriched combustion carbon capture

Abstract

This invention discloses an LNG-powered ship energy comprehensive utilization system based on oxygen-enriched combustion carbon capture, comprising an air separation oxygen production subsystem, a cold energy and waste heat utilization subsystem, and a cryogenic carbon capture subsystem. The air separation oxygen production subsystem is based on a low-pressure full reflux process, integrating a multi-stage pressurized intercooler to utilize the cold energy from air separation products and the cold energy released from the distillation column reboiler for air precooling and deep cooling. The cold energy and waste heat utilization subsystem uses LNG as a cold source and flue gas as a heat source, coupled with the energy utilization of waste nitrogen, recovering ship energy through a combination of exhaust gas turbines and Rankine cycles. The cryogenic carbon capture subsystem utilizes the cold energy from LNG, cryogenic oxygen, and waste nitrogen to precool, pressurize, and liquefy part of the flue gas, with the remaining flue gas being used as working gas and fed into the main engine. This invention, based on the oxygen-enriched combustion carbon capture method, produces high-purity oxygen using a simplified and energy-saving air separation process, and efficiently recovers and utilizes ship energy, achieving zero carbon emissions while saving electricity costs and improving navigation efficiency.

Description

Technical Field

[0001] This invention relates to an energy comprehensive utilization system for LNG-powered ships, and more particularly to an LNG-powered ship cold energy and waste heat utilization system based on oxygen-enriched combustion carbon capture. Background Technology

[0002] LNG, as a ship power fuel, can reduce nitrogen oxide emissions by up to 90%, sulfur oxide and particulate matter emissions by nearly 100%, and CO2 emissions by nearly 30% compared to traditional fuel oil or heavy oil. Its significant emission reduction advantages have made LNG-powered ships highly sought after, and the total number of LNG-powered ships is currently growing exponentially.

[0003] Currently, LNG-powered ships typically use cylinder liner cooling water or seawater to vaporize LNG, resulting in a significant waste of LNG vaporization cooling energy. Furthermore, the ships rely on exhaust gas boilers to recover waste heat, a system that is not only complex and large but also has low thermal efficiency. In addition, with increasing emphasis on the energy crisis and environmental protection, and increasingly stringent emission regulations, there is a growing expectation for ships to achieve zero carbon emissions. Applying carbon capture technology to LNG-powered ships has become a research hotspot and a major technological challenge.

[0004] Carbon capture technologies can be mainly divided into three categories: pre-combustion carbon capture, post-combustion carbon capture, and oxy-fuel combustion carbon capture. Pre-combustion carbon capture requires modification of the entire power system, and the fuel conversion process before combustion is extremely complex and costly, making it unsuitable for ships. Post-combustion carbon capture has the least impact on the power system, but several limitations hinder its application on ships. For example, chemical absorption methods, such as amine absorption, suffer from high energy consumption and corrosiveness, leading to high investment and maintenance costs. Physical adsorption and membrane separation methods are generally inefficient when CO2 content in flue gas is low. Oxy-fuel combustion carbon capture, by burning fuel in a high-concentration oxygen environment, produces a high CO2 concentration in the exhaust gas, facilitating CO2 separation and capture. However, the preparation of high-concentration oxygen is energy-intensive and requires large equipment footprint, hindering its widespread application on LNG-powered ships.

[0005] Chinese patent CN115388408A discloses a zero-NOx carbon fixation dual-fuel marine propulsion system utilizing LNG cold energy, including a cryogenic air separation system, a chemical looping combustion system, and an exhaust gas treatment system. This system utilizes LNG cold energy to produce oxygen-enriched air and perform cryogenic carbon capture of carbon dioxide, reducing the energy consumption of air separation and carbon capture. During the operation of an LNG-powered ship, the LNG supply flow rate depends on the main engine power. Based on the chemical looping combustion reaction of methane, the mass flow rate of carbon dioxide is approximately three times that of methane, and the mass flow rate of oxygen is four times that of methane. Although the air separation system recovers the cold energy from the product nitrogen and liquid oxygen, considering the significant heat transfer losses and the large difference in flow rates between the cold and heat sources, it is impractical to rely solely on the cold energy released from the LNG supplied by the main engine to capture carbon dioxide and simultaneously produce high-concentration oxygen. If additional LNG is needed to compensate for the cold energy required for system operation, the volume of the vaporized LNG would be too large to be stored on board, resulting in waste.

[0006] Chinese patent CN114961899A discloses a comprehensive waste heat and cold energy utilization system for LNG-powered ships with carbon capture functionality. This system includes an air separation module, a flue gas waste heat utilization module, and a cryogenic carbon capture module. The air separation module utilizes the cold energy from the sub-products to pre-cool and deep-cool the air, and uses the remaining low-grade cold energy to capture carbon dioxide. Simultaneously, the system comprehensively matches the temperature ranges of the ship's cold energy and waste heat, enabling tiered energy recovery and utilization. Considering the low vaporization temperature of LNG, an organic working fluid is used to improve the heat transfer range of the carbon capture heat exchanger, preventing carbon dioxide from freezing and clogging pipes under extremely low temperature conditions, thus achieving energy conservation and emission reduction goals. However, this waste heat recovery system is designed for high-temperature, high-pressure main engine exhaust and is not suitable for main engines with lower exhaust temperatures and pressures. Furthermore, the air separation system uses medium-pressure oxygen production, producing liquid oxygen, liquid nitrogen, and liquid argon. Although the air separation system recovers the cold energy from the sub-products, the overall energy consumption of the air separation system remains high. Summary of the Invention

[0007] In view of the above-mentioned defects in the prior art, the present invention aims to provide an LNG-powered ship energy comprehensive utilization system based on oxygen-enriched combustion carbon capture, which aims to improve the problem that the existing oxygen production technology has high energy consumption and is difficult to implement on ships, and to provide an effective energy utilization solution for the operating conditions of low main engine exhaust temperature and pressure, so as to achieve energy conservation and emission reduction.

[0008] The technical solution of this invention is as follows: A comprehensive energy utilization system for LNG-powered ships based on oxygen-enriched combustion carbon capture, comprising:

[0009] The air separation oxygen production subsystem includes a multi-stage pressurized intercooler, a first-stage distillation column, and a second-stage distillation column. Air is pre-cooled before entering the multi-stage pressurized intercooler for intercooling and pressurization, followed by deep cooling, and then sequentially enters the first-stage and second-stage distillation columns for two-stage distillation. The waste nitrogen discharged from the first-stage distillation column provides cooling energy for the deep cooling, intercooling pressurization, and pre-cooling of the air. The reboiler of the first-stage distillation column provides cooling load for the intercooling pressurization of the air. The liquid oxygen discharged from the second-stage distillation column provides cooling energy for the deep cooling of the air and then enters the low-temperature carbon capture subsystem. The reboiler of the second-stage distillation column provides cooling load for the deep cooling of the air. The waste argon discharged from the second-stage distillation column is combined with the waste nitrogen that provides cooling energy for the pre-cooling of the air and then enters the low-temperature carbon capture subsystem.

[0010] The cold energy and waste heat utilization subsystem includes a Rankine cycle power generation unit. The Rankine cycle power generation unit uses LNG as a cold source and the flue gas after it has been powered by the exhaust gas turbine as a heat source to generate electricity in a cycle. A portion of the flue gas after it has been used as a heat source flows into the low temperature carbon capture subsystem for carbon capture. Another portion of the flue gas after it has been used as a heat source enters the main unit as a working medium.

[0011] The cryogenic carbon capture subsystem includes a flow path in which flue gas flowing into the subsystem sequentially passes through precooling, pressurization and intercooling, and carbon capture heat exchange to form LCO2. The combined flow of waste argon and waste nitrogen sequentially provides cooling energy for the precooling and carbon capture heat exchange of the flue gas. The LNG provides cooling energy for the Rankine cycle power generation unit and then sequentially provides cooling energy for the carbon capture heat exchange and pressurization and intercooling of the flue gas before being sent to the main unit. The liquid oxygen flowing into the cryogenic carbon capture subsystem provides cooling energy for the carbon capture heat exchange of the flue gas before being sent to the main unit.

[0012] Furthermore, the air separation oxygen production subsystem includes an air expander, a waste nitrogen expander, a first-stage heat exchanger, and a second-stage heat exchanger. The air, after being intercooled and pressurized, is deeply cooled by the first-stage heat exchanger, then performs work on the air expander, and finally undergoes deep cooling by the second-stage heat exchanger. The liquid oxygen discharged from the second-stage distillation column provides cooling energy for the deep cooling of the air in the second-stage heat exchanger. The waste nitrogen discharged from the first-stage distillation column provides cooling energy for the deep cooling of the air in the first-stage heat exchanger. After providing cooling energy for the pre-cooling of the air, the waste nitrogen performs work on the waste nitrogen expander and then merges with the waste argon discharged from the second-stage distillation column.

[0013] Furthermore, the air separation oxygen production subsystem includes a first-stage air compressor, a second-stage air compressor, a third-stage air compressor, a first-stage cooler, and a second-stage cooler. The output terminals of the first-stage air compressor, the second-stage air compressor, and the third-stage air compressor are respectively connected to the second heat source input terminal, the third heat source input terminal, and the fourth heat source input terminal of the multi-stage pressurized intercooler. The input terminals of the first-stage air compressor, the second-stage air compressor, and the third-stage air compressor are respectively connected to the first heat source output terminal, the second heat source output terminal, and the third heat source output terminal of the multi-stage pressurized intercooler. The pre-cooled air is input through the first heat source input terminal of the multi-stage pressurized intercooler. The fourth heat source output terminal of the multi-stage pressurized intercooler is connected to the first-stage heat exchanger. The second-stage cooler is cyclically connected to the multi-stage pressurized intercooler. The reboiler of the first-stage distillation column provides a cooling load for the second-stage cooler. The first-stage cooler is connected between the air expander and the second-stage heat exchanger. The reboiler of the second-stage distillation column provides a cooling load for the air deeply cooled in the first-stage cooler.

[0014] Furthermore, the Rankine cycle power generation unit includes a three-stage cascaded first-stage Rankine cycle power generation unit, a second-stage Rankine cycle power generation unit, and a third-stage Rankine cycle power generation unit. The flue gas after being powered by the exhaust gas turbine serves as the heat source for the first-stage Rankine cycle power generation unit, and LNG serves as the cold source for the third-stage Rankine cycle power generation unit. The first-stage circulating working fluid after being powered by expansion in the first-stage Rankine cycle power generation unit serves as the heat source for the second-stage Rankine cycle power generation unit, and the second-stage circulating working fluid after being powered by expansion in the second-stage Rankine cycle power generation unit serves as the heat source for the third-stage Rankine cycle power generation unit.

[0015] Furthermore, in the first-stage Rankine cycle power generation unit, the first-stage working fluid is first heated by high-temperature cylinder liner cooling water and then heated by the flue gas after it has done work through the exhaust gas turbine before expanding and doing work; in the third-stage Rankine cycle power generation unit, the third-stage working fluid is first heated by the second-stage working fluid after it has expanded and done work, and then heated by high-temperature cylinder liner cooling water before expanding and doing work.

[0016] Furthermore, the combined flow of waste nitrogen and waste argon, which provides cooling energy for the carbon capture heat exchange, provides cooling energy for the second-stage circulating working fluid after it expands and does work, before being discharged.

[0017] Furthermore, the operating temperature range of the first-stage working fluid in the first-stage Rankine cycle power generation unit is 25~300℃, the operating temperature range of the second-stage working fluid in the second-stage Rankine cycle power generation unit is -50~100℃, and the operating temperature range of the third-stage working fluid in the third-stage Rankine cycle power generation unit is -100~80℃.

[0018] Furthermore, the first-stage Rankine cycle power generation unit adopts a transcritical Rankine cycle, the second-stage Rankine cycle power generation unit and the third-stage Rankine cycle power generation unit adopt an organic Rankine cycle, the first-stage working fluid in the first-stage Rankine cycle power generation unit is CO2, the second-stage working fluid in the second-stage Rankine cycle power generation unit is R1270, and the third-stage working fluid in the third-stage Rankine cycle power generation unit is R1150.

[0019] Furthermore, the working temperature range of the refrigeration cycle working fluid for heat transfer between the multi-stage pressurized intercooler and the second-stage cooler is -140~-162℃, and the refrigeration cycle working fluid in the air separation oxygen production subsystem is CH4.

[0020] Furthermore, the cryogenic carbon capture subsystem includes a first-stage flue gas compressor, a flue gas intercooler, and a second-stage flue gas compressor connected in sequence. The pre-cooled flue gas is connected to the first-stage flue gas compressor, and the flue gas pressurized by the second-stage flue gas compressor undergoes carbon capture heat exchange. The LNG after carbon capture heat exchange is pressurized and intercooled by the flue gas intercooler to provide cold energy for the flue gas before being sent to the main unit.

[0021] This invention addresses the problems of high energy consumption and complex processes in existing air separation oxygen production technologies. Combining this with the actual air separation requirements of ships, a simplified and energy-efficient air separation oxygen production system is designed. Simultaneously, it incorporates a full-ship cold energy and waste heat utilization design for the low exhaust gas temperature of the main engine. The air separation oxygen production subsystem is based on a low-pressure full reflux process, integrating a multi-stage air pressurization intercooler heat exchanger. Based on the heat exchange temperature gradient, it recovers the cold energy from the air separation products and the cold energy released from the reboiler in the distillation column for front-end air pre-cooling and deep cooling. The cold energy and waste heat utilization subsystem uses the LNG side as a cold source and the flue gas side as a heat source, coupling the energy utilization of cylinder liner water and waste nitrogen. It recovers ship energy through a combination of exhaust gas turbines and a three-stage cascaded Rankine cycle. The cryogenic carbon capture subsystem utilizes the cold energy from LNG, cryogenic oxygen, and waste nitrogen to pre-cool and dehydrate a portion of the diverted flue gas, pressurize and intercool it, and capture it at cryogenic liquefaction. The remaining portion is used as the working medium to enter the main engine.

[0022] The advantages of this invention compared to the prior art are:

[0023] 1. Targeting marine applications, only high-purity oxygen needs to be produced. A low-pressure full reflux process is adopted. Based on the heat exchange range of air, the cold energy of low-temperature nitrogen, low-temperature argon and liquid oxygen, as well as the cold load released by the reboiler of the two-stage distillation column, are reused for front-end cooling of the air separation unit. Furthermore, the integration of the intercooler heat exchanger can greatly reduce the energy consumption of the air separation unit and reduce the size of the device.

[0024] 2. Based on the temperature and pressure of the ship's exhaust gas and the LNG pressurization requirements, a three-stage cascaded Rankine cycle is constructed, using the flue gas side as the heat source and the LNG side as the cold source. This includes one transcritical Rankine cycle and two organic Rankine cycles, and incorporates the utilization of high-temperature cylinder liner cooling water. This energy utilization system not only solves the problem of the original system's complexity and size by replacing the boiler, but also better matches the temperature range of the heat and cold sources, reduces heat loss during heat transfer, and efficiently recovers and utilizes the ship's energy.

[0025] 3. By adopting the oxygen-enriched combustion carbon capture method, on the one hand, the efficiency of the main engine can be improved and the fuel consumption can be reduced, and on the other hand, the exhaust gas with a high concentration of carbon dioxide is obtained, which eliminates the complicated steps of exhaust gas after-treatment and makes it easier to achieve zero carbon emissions. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the LNG-powered ship energy comprehensive utilization system based on oxygen-enriched combustion carbon capture, according to an embodiment of the present invention. Detailed Implementation

[0027] The present invention will be further described below with reference to embodiments. It should be understood that these embodiments are only for illustrating the present invention and are not intended to limit the scope of the present invention. After reading this description, any modifications of this description in various equivalent forms by those skilled in the art will fall within the scope defined by the appended claims.

[0028] Please combine Figure 1 As shown, the LNG-powered ship energy comprehensive utilization system based on oxygen-enriched combustion carbon capture involved in the embodiments of the present invention includes:

[0029] The air separation oxygen production subsystem includes, in sequence, an air filter 1, an air precooler 2, a first steam-water separator 3, a multi-stage pressurization system with intercooling (including an intercooled heat exchanger 4, a first-stage air compressor 5, a second-stage air compressor 6, and a third-stage air compressor 7), a first-stage heat exchanger 8, an air expander 9, a first-stage cooler 10, a second-stage heat exchanger 11, a first-stage distillation column 12, and a second-stage distillation column 13. The multi-stage pressurization system with intercooling includes an integrated intercooled heat exchanger 4 as its core, and a second-stage cooler 14 and a first-stage air compressor 5 connected to it. The first air compressor 5, the second air compressor 6, and the third air compressor 7 are connected to the first heat source input terminal 401 of the first air-water separator 3. The output terminals of the first air compressor 5, the second air compressor 6, and the third air compressor 7 are respectively connected to the second heat source input terminal 403, the third heat source input terminal 405, and the fourth heat source input terminal 407 of the indirect heat exchanger 4. The input terminals of the first air compressor 5, the second air compressor 6, and the third air compressor 7 are respectively connected to the first heat source output terminal 402, the second air source output terminal 403, the third heat source input terminal 405, and the fourth heat source input terminal 407 of the indirect heat exchanger 4. The heat source output terminal 404, the third heat source output terminal 406, and the fourth heat source output terminal 408 of the intercooled heat exchanger 4 are connected to the heat source input terminal 801 of the first-stage heat exchanger 8. The first cold source input terminal 409 of the intercooled heat exchanger 4 is connected to the cold source output terminal 804 of the first-stage heat exchanger 8. The first cold source output terminal 410 of the intercooled heat exchanger 4 is connected to the cold source input terminal 203 of the air precooler 2. The second cold source input terminal 411 and the second cold source output terminal 412 of the intercooled heat exchanger 4 are respectively connected to the output terminal and the input terminal of the second-stage cooler 14. The upper column of the first-stage distillation column 12... The cold source input terminal 803 of the first-stage heat exchanger 8 is connected to the first-stage distillation column 12. The lower column of the first-stage distillation column 12 is connected to the second-stage distillation column 13. The lower column of the second-stage distillation column 13 is connected to the cold source input terminal 1103 of the second-stage heat exchanger 11. The air separation oxygen production subsystem also includes a waste nitrogen expander 15 and a waste nitrogen and waste argon collector 16. The input terminal of the waste nitrogen expander 15 is connected to the cold source output terminal 204 of the air precooler 2. The first input terminal 1601 and the second input terminal 1602 of the waste nitrogen and waste argon collector 16 are respectively connected to the output terminal of the waste nitrogen expander 15 and the upper column of the second-stage distillation column 13.

[0030] The LNG side of the cold energy and waste heat utilization subsystem includes an LNG storage tank 17, a first-stage LNG booster pump 18, a third-stage circulating condenser 19, and a second-stage LNG booster pump 20 connected in sequence. The output end of the first-stage LNG booster pump 18 is connected to the cold source input end 1903 of the third-stage circulating condenser 19, and the cold source output end 1904 of the third-stage circulating condenser 19 is connected to the input end of the second-stage LNG booster pump 20. The flue gas side of the cold energy and waste heat utilization subsystem includes an exhaust gas turbine 33, a first-stage circulating evaporator 31, a first-stage circulating preheater 30, a seawater cooler 34, a first and third steam-water separator 35, and a flue gas diversion system connected in sequence. The output end of the exhaust gas turbine 33 is connected to the heat source input end 3101 of the first-stage circulating evaporator 31. The heat source output end 3102 of the first-stage circulating evaporator 31 is connected to the second heat source input end 3003 of the first-stage circulating preheater 30. The second heat source output end 3004 of the first-stage circulating preheater 30 is connected to the input end 3601 of the seawater cooler 34. The gas phase output end of the first and third steam-water separators 35 is connected to the input end 3601 of the flue gas distributor 36. The first output end 3602 of the flue gas distributor 36 distributes the circulating working medium, and the second output end 3603 of the flue gas distributor 36 distributes the captured flue gas. The first-stage Rankine cycle generator... The electrical unit includes a first-stage circulating working fluid pump 29, a first-stage circulating preheater 30, a first-stage circulating evaporator 31, a first-stage circulating expander 32, a second-stage circulating evaporator 26, and a seawater cooler 28 connected in sequence. The output terminal of the first-stage circulating working fluid pump 29 is connected to the cold source input terminal 3005 of the first-stage circulating preheater 30. The cold source output terminal 3006 of the first-stage circulating preheater 30 is connected to the cold source input terminal 3103 of the first-stage circulating evaporator 31. The first-stage circulating expander 32 is connected between the cold source output terminal 3104 of the first-stage circulating evaporator 31 and the heat source input terminal 2601 of the second-stage circulating evaporator 26. A seawater cooler 28 is connected between the heat source output terminal 2602 of the generator 26 and the input terminal of the first-stage circulating working fluid pump 29; the second-stage Rankine cycle power generation unit includes a second-stage circulating working fluid pump 25, a second-stage circulating evaporator 26, a second-stage circulating expander 27, and a second-stage circulating condenser 22 connected in sequence. The second-stage circulating expander 27 is connected between the cold source output terminal 2604 of the second-stage circulating evaporator 26 and the heat source input terminal 2201 of the second-stage circulating condenser 22, and the second-stage circulating working fluid pump 25 is connected between the heat source output terminal 2202 of the second-stage circulating condenser 22 and the cold source input terminal 2603 of the second-stage circulating evaporator 26.The third-stage Rankine cycle power generation unit includes a third-stage circulating working fluid pump 21, a second-stage circulating condenser 22, a third-stage circulating evaporator 23, a third-stage circulating expander 24, and a third-stage circulating condenser 19 connected in sequence. The third-stage circulating working fluid pump 21 is connected between the heat source output terminal 1902 of the third-stage circulating condenser 19 and the second cold source input terminal 2205 of the second-stage circulating condenser 22. The second cold source output terminal 2206 of the second-stage circulating condenser 22 is connected to the cold source input terminal 2303 of the third-stage circulating evaporator 23. The third-stage circulating expander 24 is connected between the cold source output terminal 2304 of the third-stage circulating evaporator 23 and the heat source input terminal 1901 of the third-stage circulating condenser 19.

[0031] The low-temperature carbon capture subsystem includes, in sequence, a flue gas precooler 37, a first and second steam-water separator 38, a first-stage flue gas compressor 39, a flue gas intercooler 40, a second-stage flue gas compressor 41, a carbon capture heat exchanger 42, and an LCO2 storage tank 43. The heat source input terminal 3701 of the flue gas precooler 37 is connected to the second output terminal 3603 of the flue gas distributor 36, and the heat source output terminal 3702 of the flue gas precooler 37 is connected to the first and second steam-water separators. The gas phase output terminals of the first and second gas-water separators 38 and the heat source input terminal 4001 of the flue gas intercooler 40 are connected to the first-stage flue gas compressor 39. The heat source output terminal 4002 of the flue gas intercooler 40 and the heat source input terminal 4201 of the carbon capture heat exchanger 42 are connected to the second-stage flue gas compressor 41. The heat source output terminal 4202 of the carbon capture heat exchanger 42 is connected to the LCO2 storage tank 43. The flow path on the cold fluid side is that the cold source of the flue gas precooler 37 is... Input terminal 3703 is connected to output terminal 1603 of waste nitrogen and waste argon collector 16 of air separation oxygen production subsystem. The first cold source input terminal 4203, second cold source input terminal 4205, and third cold source input terminal 4207 of carbon capture heat exchanger 42 are respectively connected to the cold source output terminal 1104 of the second-stage heat exchanger 11 of air separation oxygen production subsystem, the output terminal of the second-stage LNG booster pump 20 of cold energy and waste heat utilization subsystem, and the cold source output terminal 3704 of flue gas precooler 37. The second cold source output terminal 4206 of the carbon capture heat exchanger 42 is connected to the cold source input terminal 4003 of the flue gas intercooler 40. The NG flowing out of the cold source output terminal 4004 of the flue gas intercooler 40 is sent to the main unit. The third cold source output terminal 4208 of the carbon capture heat exchanger 42 is connected to the first cold source input terminal 2203 of the second-stage circulating condenser 22. The waste nitrogen that has completed the cold energy reuse is discharged through the first cold source output terminal 2204 of the second-stage circulating condenser 22.

[0032] Using a 210,000-ton Newcastlemax dual-fuel bulk carrier as an example, this embodiment further illustrates the working process of each component in the LNG-powered ship energy utilization system based on oxygen-enriched combustion carbon capture. The LNG in LNG storage tank 17 consists of 95% methane, 3% ethane, and 2% propane. The air composition is 78.1% nitrogen, 20.9% oxygen, 0.94% argon, 0.03% carbon dioxide, and 0.03% water vapor. Considering the oxygen production requirements and energy consumption, the oxygen (not pure oxygen) introduced into the engine has a composition of 98.35% oxygen and 1.65% argon. Since the oxygen introduced in this example is not pure oxygen, to achieve zero carbon emissions, the circulating CO2 composition is adjusted to 94.31% carbon dioxide, 2.82% argon, and 2.87% water vapor.

[0033] Process parameter description:

[0034] Air flow: Air (25℃, 110kPa, 38558kg / h) is filtered by air filter 1 to remove impurities. In air precooler 2, it exchanges heat with waste nitrogen (-112.5℃, 554kPa) from intercooled heat exchanger 4 to precool to -52℃. Then, it passes through first gas-liquid separator 3 to remove the liquid phase. Next, it passes through a multi-stage pressurization system with intercooling, which is divided into three stages of pressurization (280kPa-600kPa-1000kPa, cooled to -158℃ after each pressurization). Then, it passes through first-stage heat exchanger 8 to exchange heat with low-temperature nitrogen (-177.4℃, 554kPa) from first-stage distillation column 12 to cool to -164.5℃. Finally, it is expanded and cooled by air expander 9. Subsequently, the air (-172.5℃, 600kPa, gas fraction 0.9506) is further cooled to -173.9℃ (gas fraction 0.4432) by the first-stage cooler 10 and the second-stage heat exchanger 11. The air then enters the first-stage distillation column 12, where nitrogen (-177.4℃, 554kPa) flows out from the upper column, and liquid oxygen (-163.3℃, ​​557kPa, purity 95.6%) flows out from the lower column. This enters the second-stage distillation column 13, where argon (-188.6℃, 105kPa) flows out from the upper column, and liquid oxygen (-182.4℃, 110kPa, purity 98.3%) flows out from the lower column. This then enters the second-stage heat exchanger 11 to provide some cooling energy for the air's deep cooling before entering the carbon capture subsystem. After being heated to 25℃ by the carbon capture heat exchanger 42, it is sent to the engine. Nitrogen gas exiting the first-stage distillation column 12 flows sequentially through the first-stage heat exchanger 8, the intercooler heat exchanger 4, and the air precooler 2 to provide cooling energy for the air separation front-end, raising its temperature to -16.41℃. It then enters the waste nitrogen expander 15 and expands to 105 kPa (-100.6℃). Subsequently, it merges with argon gas exiting the second-stage distillation column 13 via the waste nitrogen and waste argon collector 16 and enters the carbon capture subsystem. After heat exchange in the flue gas precooler 37 and the carbon capture heat exchanger 42, its temperature rises to -64.7℃. It then enters the cold energy and waste heat utilization subsystem, where it undergoes heat exchange in the second-stage circulating condenser 22 to provide the required cooling energy for the condensation of the second-stage circulating working fluid R1270 in the second-stage Rankine cycle power generation unit, raising its temperature to -16.43℃ before being discharged. The reboiler of the second-stage distillation column 13 (temperature -182.4℃) provides a cooling load of 543.9kW to the first-stage cooler 10, and the reboiler of the first-stage distillation column 12 (temperature -163.3℃) provides a cooling load of 1884kW to the second-stage cooler 14. In the refrigeration cycle, the working medium CH4 flowing into the second-stage cooler 14 has a temperature of -150℃, and the working medium CH4 flowing out of the second-stage cooler 14 has a temperature of -162℃.

[0035] LNG process: LNG (-162℃, 600kPa, 2084kg / h) is discharged from storage tank 17, pressurized to 15MPa (-154.3℃) for the first time by the first-stage LNG booster pump 18, and then heat-exchanged by the third-stage circulating condenser 19 to provide the cold energy required for condensation of the third-stage circulating working fluid R1150 in the third-stage Rankine cycle power generation unit, and heated to -90℃. Then, the LNG is pressurized for the second time by the second-stage LNG booster pump 20 to the inlet pressure of 30MPa (-74.53℃), and then enters the carbon capture subsystem to be heated to 0℃ by the carbon capture heat exchanger 42, and then heated to 45℃ and 30MPa by the flue gas intercooler 40.

[0036] Flue gas flow: The flue gas discharged from the main unit (212℃, 200kPa, 167198kg / h) first enters the exhaust gas turbine 33 to generate electricity. Then, the flue gas (165.5℃, 110kPa) exchanges heat with the first-stage circulating evaporator 31 and the first-stage circulating preheater 30 to provide heat for the first-stage circulating working fluid CO2 of the first-stage Rankine cycle power generation unit. The flue gas is cooled to 52℃. At this time, there is little usable waste heat. It is cooled to 25℃ by the seawater cooler 34 and the liquid phase is removed by the first and third steam-water separators 35. Then, the flue gas is divided into two streams by the distributor 36. One stream is used as the circulating working medium, and the other stream is used as the capture flue gas. The flue gas to be captured (25℃, 110kPa, 6151kg / h) is first cooled to -52℃ by the flue gas precooler 37 and the liquid phase is removed by the first and second steam-water separators 38. Then, it is pressurized in two stages with NG as the cold source to obtain flue gas at 1200kPa (87.89℃). Finally, it is liquefied by heat exchange in the carbon capture heat exchanger 42 and sent to the LCO2 storage tank 43 to complete the capture.

[0037] The first-stage transcritical CO2 Rankine cycle: After the exhaust steam from the first-stage circulating expander 32 has been used for power generation, the first-stage circulating working fluid (CO2, 88.45℃, 6700kPa, 90000kg / h) first exchanges heat with the second-stage circulating working fluid R1270 (-45.87℃) in the second-stage circulating evaporator 26, cooling it to 70.04℃. Then, it exchanges heat with the seawater cooler 28 to 25℃, and then is pressurized to 15.5MPa by the first-stage circulating working fluid pump 29. After that, it exchanges heat with the high-temperature cylinder liner cooling water (85℃) and the main engine exhaust gas in the first-stage circulating preheater 30 and the first-stage circulating evaporator 31 to 160℃. Finally, it is used for power generation by the first-stage circulating expander 32 to complete one cycle.

[0038] The second-stage organic Rankine cycle: The second-stage circulating working fluid (R1270, -8.567℃, 450kPa, 4300kg / h) after the exhaust steam from the second-stage circulating expander 27 is first condensed to -48℃ by heat exchange with the third-stage circulating working fluid (R1150, -94.37℃) and low-temperature waste nitrogen (-64.7℃) in the second-stage circulating condenser 22. Then, it is pressurized to 3800kPa by the second-stage circulating working fluid pump 21. After that, it exchanges heat with the exhaust steam (88.45℃) of the first-stage circulating working fluid in the second-stage circulating evaporator 26, and is heated to 82℃. Finally, it is condensed to complete one cycle by work done by the second-stage circulating expander 27.

[0039] The third-stage organic Rankine cycle: The third-stage working fluid (R1150, -52.33℃, 160kPa, 872.7kg / h) after the exhaust gas from the third-stage circulating expander 24 first exchanges heat with LNG (-154.3℃) in the third-stage circulating condenser 19 and condenses to -96℃. Then, it is pressurized to 2400kPa by the third-stage circulating working fluid pump 21. Subsequently, it provides the cold energy required for the condensation of the second-stage circulating working fluid R1270 through the second-stage circulating condenser 22, raising its temperature to -15℃. Then, it exchanges heat with high-temperature cylinder liner cooling water (85℃) in the third-stage circulating evaporator 23 and lowers its temperature to 80℃. Finally, it is powered by the third-stage circulating expander 24, completing one cycle.

Claims

1. An LNG powered ship energy comprehensive utilization system based on oxygen-enriched combustion carbon capture, characterized in that, The system comprises: an air separation subsystem comprising a multi-stage booster intercooler, a first rectification tower and a second rectification tower, air is pre-cooled and then enters the multi-stage booster intercooler for intercooling and boosting, and then is deep-cooled and sequentially enters the first rectification tower and the second rectification tower for two-stage rectification, waste nitrogen discharged from the first rectification tower provides cold energy for deep cooling, intercooling and boosting and pre-cooling of the air, a reboiler of the first rectification tower provides cold load for intercooling of the air, liquid oxygen discharged from the second rectification tower provides cold energy for deep cooling of the air and then enters a low-temperature carbon capture subsystem, a reboiler of the second rectification tower provides cold load for deep cooling of the air, and waste argon discharged from the second rectification tower is combined with waste nitrogen that has provided cold energy for pre-cooling of the air and then enters the low-temperature carbon capture subsystem; a cold energy and waste heat utilization subsystem comprising a Rankine cycle power generation unit, the Rankine cycle power generation unit uses LNG as a cold source and flue gas after work done by a waste gas turbine as a heat source to generate power, a part of the flue gas after heat release as a heat source flows into the low-temperature carbon capture subsystem for carbon capture, and another part of the flue gas after heat release as a heat source enters a main engine as a working medium; the Rankine cycle power generation unit comprises a first-stage Rankine cycle power generation unit, a second-stage Rankine cycle power generation unit and a third-stage Rankine cycle power generation unit in cascade, the flue gas after work done by the waste gas turbine is a heat source of the first-stage Rankine cycle power generation unit, LNG is a cold source of the third-stage Rankine cycle power generation unit, a first-stage cycle working medium after expansion and work done in the first-stage Rankine cycle power generation unit is a heat source of the second-stage Rankine cycle power generation unit, a second-stage cycle working medium after expansion and work done in the second-stage Rankine cycle power generation unit is a heat source of the third-stage Rankine cycle power generation unit, in the first-stage Rankine cycle power generation unit, the first-stage cycle working medium is heated by high-temperature cylinder jacket cooling water first and then by the flue gas after work done by the waste gas turbine and then is expanded and worked; in the third-stage Rankine cycle power generation unit, a third-stage cycle working medium is heated by the second-stage cycle working medium after expansion and work done first and then by high-temperature cylinder jacket cooling water and then is expanded and worked; the low-temperature carbon capture subsystem comprises a flow path of the flue gas flowing into the low-temperature carbon capture subsystem, the flue gas sequentially undergoes pre-cooling, intercooling and carbon capture heat exchange to form LCO2, the combination of the waste argon and the waste nitrogen sequentially provides cold energy for pre-cooling and carbon capture heat exchange of the flue gas, LNG provides cold energy for the Rankine cycle power generation unit and then sequentially provides cold energy for carbon capture heat exchange and intercooling of the flue gas and then is sent to a main engine, liquid oxygen flowing into the low-temperature carbon capture subsystem provides cold energy for carbon capture heat exchange of the flue gas and then is sent to the main engine, and the combination of the waste nitrogen and the waste argon after providing cold energy for the carbon capture heat exchange provides cold energy for the second-stage cycle working medium after expansion and work done and then is discharged.

2. The LNG powered ship energy integrated system based on oxy-combustion carbon capture of claim 1, characterized in that, The air separation and oxygen production subsystem comprises an air expander, a waste nitrogen expander, a first-stage heat exchanger and a second-stage heat exchanger, the air pressurized by intercooling is deep-cooled by the first-stage heat exchanger, and then is deep-cooled by the second-stage heat exchanger after work done by the air expander, the liquid oxygen discharged from the second-stage rectifying tower provides cold energy for the deep cooling of the air in the second-stage heat exchanger, the waste nitrogen discharged from the first-stage rectifying tower provides cold energy for the deep cooling of the air in the first-stage heat exchanger, and the waste nitrogen after cold energy provided for the pre-cooling of the air is combined with the waste argon discharged from the second-stage rectifying tower after work done by the waste nitrogen expander.

3. The LNG powered ship energy integrated system based on oxy-combustion carbon capture of claim 2, characterized in that, The air separation and oxygen production subsystem comprises a first-stage air compressor, a second-stage air compressor, a third-stage air compressor, a first-stage cooler and a second-stage cooler, the output ends of the first-stage air compressor, the second-stage air compressor and the third-stage air compressor are connected to the second heat source input end, the third heat source input end and the fourth heat source input end of the multi-stage pressurized intercooler respectively, the input ends of the first-stage air compressor, the second-stage air compressor and the third-stage air compressor are connected to the first heat source output end, the second heat source output end and the third heat source output end of the multi-stage pressurized intercooler respectively, the air after pre-cooling is input from the first heat source input end of the multi-stage pressurized intercooler, the fourth heat source output end of the multi-stage pressurized intercooler is connected to the first-stage heat exchanger, the second-stage cooler is connected to the multi-stage pressurized intercooler in circulation, the reboiler of the first-stage rectifying tower provides cold load for the second-stage cooler, the first-stage cooler is connected between the air expander and the second-stage heat exchanger, and the reboiler of the second-stage rectifying tower provides cold load for the air deep-cooled in the first-stage cooler.

4. The LNG powered ship energy integrated system based on oxy-combustion carbon capture of claim 1, characterized in that, The working temperature range of the first-stage circulating working medium in the first-stage Rankine cycle power generation unit is 25-300℃, the working temperature range of the second-stage circulating working medium in the second-stage Rankine cycle power generation unit is -50-100℃, and the working temperature range of the third-stage circulating working medium in the third-stage Rankine cycle power generation unit is -100-80℃.

5. The LNG powered ship energy integrated system based on oxy-combustion carbon capture of claim 4, characterized in that, The first-stage Rankine cycle power generation unit adopts a transcritical Rankine cycle, the second-stage Rankine cycle power generation unit and the third-stage Rankine cycle power generation unit adopt an organic Rankine cycle, the first-stage circulating working medium in the first-stage Rankine cycle power generation unit is CO2, the second-stage circulating working medium in the second-stage Rankine cycle power generation unit is R1270, and the third-stage circulating working medium in the third-stage Rankine cycle power generation unit is R1150.

6. The LNG powered ship energy integrated system based on oxy-combustion carbon capture of claim 3, wherein, The working temperature range of the refrigeration circulating working medium performing heat transfer between the multi-stage pressurized intercooler and the second-stage cooler is -140--162℃, and the refrigeration circulating working medium in the air separation and oxygen production subsystem is CH4.

7. The LNG powered ship energy integrated system based on oxy-combustion carbon capture of claim 1, wherein, The low-temperature carbon capture subsystem comprises a first-stage flue gas compressor, a flue gas intercooler and a second-stage flue gas compressor connected in sequence, the pre-cooled flue gas is connected to the first-stage flue gas compressor, the flue gas pressurized by the second-stage flue gas compressor is subjected to carbon capture heat exchange, and the LNG after the carbon capture heat exchange provides cold energy for the flue gas in the flue gas intercooler to perform pressurized intercooling and then is sent into the main engine.

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