WO2024011780A1

WO2024011780A1 - Low-temperature carbon capture coupling cold energy and waste heat gradient utilization system for lng-powered vessel

Info

Publication number: WO2024011780A1
Application number: PCT/CN2022/126053
Authority: WO
Inventors: 姚寿广; 李辰
Original assignee: 江苏科技大学
Priority date: 2022-07-13
Filing date: 2022-10-19
Publication date: 2024-01-18
Also published as: CN115263466A

Abstract

A low-temperature carbon capture coupling cold energy and waste heat gradient utilization system for an LNG-powered vessel. The system comprises: an LNG evaporation side, wherein an LNG serves as a cold source of a first two-stage cascaded Rankine cycle, and after first-stage pressurization, first-stage heat exchange, second-stage pressurization, second-stage heat exchange and seawater temperature adjustment are performed, an NG is formed and then sent to an engine; an air side, wherein liquid oxygen is prepared by means of a low-temperature rectification method, cold energy of an air separation product is reused for air cooling and carbon capture, and the liquid oxygen is regasified and then sent to the engine; and a flue gas side, wherein after an exhaust-driven gas turbine does work on a flue gas discharged by a main engine, heat energy is provided for a second two-stage cascaded Rankine cycle, and then, after fourth-stage heat exchange and seawater cooling on the flue gas side are performed, water is separated out and then shunted, with one path being sent to the engine, and the other path being pressurized and then captured by means of low-temperature liquefaction. When a gas intake condition of a vessel is met, an oxygen-enriched combustion system for a main engine is constructed, and carbon dioxide in a discharged flue gas can be efficiently captured while cold energy and waste heat of a large vessel are fully recycled, thereby achieving the aim of energy conservation and emission reduction.

Description

Low temperature carbon capture coupled cold energy and waste heat cascade utilization system for LNG powered ships

Technical field

The invention relates to an energy utilization system for an LNG powered ship, in particular to a low-temperature carbon capture coupling cold energy and waste heat cascade utilization system for an LNG powered ship.

Background technique

The large amount of cold energy released during the vaporization process of LNG on existing LNG-powered ships is almost directly taken away by the seawater, resulting in a waste of energy and harm to the marine ecology. Secondly, the large amount of thermal energy and kinetic energy of the exhaust gas are not fully utilized. In addition, although LNG has significant emission reduction benefits as a ship power fuel, the amount of CO ₂ emitted by the entire shipping industry cannot be underestimated.

The Chinese patent with publication number CN113669175A proposes a low-temperature desublimation carbon capture system and method for marine natural gas engine exhaust. The system includes an LNG gas supply system, a marine main engine combustion system, a carbon enrichment system and a low-temperature desublimation carbon capture system. The collection system enriches more than 90% of the high-concentration carbon-containing tail gas through the alcohol amine method, and combines the cold energy in the LNG gasification process to achieve more than 95% of the CO ₂ capture and storage in the atmospheric tail gas. However, this system The use of chemical absorption method to enrich _CO2 cannot achieve zero carbon emissions, and the regeneration of the chemical adsorbent is difficult, resulting in a decrease in enrichment efficiency. At the same time, the entire system consumes a lot of energy and chemicals.

The Chinese patent with publication number CN113738467A proposes an integrated system for using liquefied natural gas to generate electricity with carbon capture. This system integrates LNG gasification, cold energy oxygen production, oxygen-enriched power generation and carbon capture, which can greatly reduce the cost of LNG gas. , the energy consumption in oxygen production and carbon capture links, LNG cold energy utilization rate is improved, power generation efficiency is improved, and the captured carbon dioxide is injected into underground salt water for storage, which can achieve zero-carbon emission power generation effect. However, this system is intended for land application scenarios. Its LNG flow rate is large enough to provide the cold energy required for the oxygen production and carbon capture processes. However, the LNG intake flow rate on ships is much smaller than the flue gas flow rate and cannot meet the needs of oxygen production and carbon capture. The demand for cooling capacity makes this system difficult to apply on ships.

Contents of the invention

In view of the above-mentioned deficiencies in the prior art, the task of the present invention is to provide a low-temperature carbon capture coupled cold energy and waste heat cascade utilization system for LNG-powered ships to reduce carbon emissions and energy consumption when the LNG cooling capacity of the ship is relatively small.

The technical solution of the present invention is as follows: a low-temperature carbon capture coupled cold energy and waste heat cascade utilization system for LNG-powered ships, including:

On the LNG evaporation side, the LNG coming out of the LNG storage tank undergoes first-stage pressurization, first-stage LNG heat exchange, second-stage pressurization, second-stage LNG heat exchange and seawater temperature adjustment to form NG and send it to the main engine;

On the flue gas side, the flue gas discharged by the host undergoes the first-stage flue gas expansion work, the first-stage flue gas heat exchange, the second-stage flue gas expansion work, the second-stage flue gas heat exchange, and the third-stage flue gas heat exchange. After cooling with sea water, the water is separated through the first flue gas water separator, and further divided into two paths, one is sent to the main engine, and the other path passes through the flue gas precooler, the second flue gas water separator, and the flue gas compressor in sequence. After the fourth-stage flue gas heat exchange and the fifth-stage flue gas heat exchange, the low-temperature liquefaction capture is completed and sent to the LCO ₂ storage tank;

On the air side, the air is sequentially subjected to multi-stage cooling and pressurization and two-stage rectification. The waste nitrogen formed after the air passes through the two-stage rectification is used to perform multi-stage cooling and pressurization of the air except for the final stage cooling. The front-stage cooling then absorbs heat energy through the third-stage flue gas heat exchanger and then performs work through the waste nitrogen turbine. The waste argon formed after the two-stage distillation of the air is mixed with the waste nitrogen coming out of the waste nitrogen turbine. Then, cold energy is provided to the flue gas precooler and carbon capture heat exchanger in sequence and then discharged. The liquid oxygen formed after the air undergoes the two-stage rectification is used to cool the air in the final stage and then cools the air in the carbon capture heat exchanger. The heater is regasified and sent to the host machine;

The first-stage organic Rankine cycle power generation unit, the circulation loop of the first-stage organic Rankine cycle power generation unit is that the first-stage circulating working fluid is pressurized and heated by the second-stage circulating working fluid in the first-stage circulating evaporator, And carry out a circuit in which the first-stage LNG heat exchanges and then pressurizes again after the expansion work;

A second-stage organic Rankine cycle power generation unit. The circulation loop of the second-stage organic Rankine cycle power generation unit heats and expands the flue gas from the flue gas compressor after the second-stage circulating working fluid is pressurized. After the work is done, the circuit sequentially passes through the first-stage circulating evaporator and the second-stage circulating seawater cooler to exchange heat and then re-pressurize;

The third-stage organic Rankine cycle power generation unit. The circulation loop of the third-stage organic Rankine cycle power generation unit is that the third-stage circulating working fluid is pressurized and then exchanges heat with the flue gas through the third-stage circulation preheater. The second-stage flue gas heat exchange is carried out, and after the expansion and work are performed, the heat is exchanged through the third-stage circulating seawater cooler and then re-pressurized; the fourth-stage transcritical Rankine cycle power generation unit, the fourth-stage transcritical Rankine cycle The circulation loop of the Ken cycle power generation unit is a fourth-stage transcritical Rankine cycle working fluid that is pressurized and then preheated by high-temperature cylinder liner cooling water, regenerated by the fourth-stage circulation regenerator, and then combined with the first-stage flue gas. It exchanges heat, performs expansion and work, and then passes through the fourth-stage circulating regenerator, the third-stage circulating preheater, and the fourth-stage circulating seawater cooler to exchange heat and then re-pressurize;

Among them, the first-stage LNG heat exchange is for LNG to provide cold energy to the first-stage organic Rankine cycle working fluid, and the second-stage LNG heat exchange is for LNG to provide cold energy to the carbon capture heat exchanger. The first-stage flue gas heat exchange is for the flue gas to provide thermal energy to the fourth-stage Rankine cycle working fluid. The second-stage flue gas heat exchange is for the flue gas to provide thermal energy to the third-stage Rankine cycle working fluid. The third-stage flue gas heat exchanger is The first-stage flue gas heat exchange is to provide thermal energy from the flue gas to the waste nitrogen after primary cooling of the air. The fourth-stage flue gas heat exchange is to provide the flue gas compressed by the flue gas compressor with thermal energy to the second-stage circulating working fluid. Release thermal energy. The fifth-stage flue gas heat exchange is that the flue gas releases thermal energy to the carbon capture heat exchanger. In the carbon capture heat exchanger, the second-stage pressurized LNG, The oxygen after final-stage cooling of the air and the waste nitrogen and waste argon after heat exchange in the flue gas precooler jointly absorb heat to the flue gas after heat exchange with the second-stage circulating working fluid.

Further, it includes a fifth-stage organic Rankine cycle power generation unit. The circulation loop of the fifth-stage organic Rankine cycle power generation unit is that the fifth-stage circulating working fluid is pressurized and then passes through the fifth-stage circulation regenerator to exchange heat. The high-temperature cylinder liner cooling water is heated, expands and performs work, and then sequentially passes through the fifth-stage circulation regenerator for heat exchange and the waste nitrogen and waste argon coming out of the carbon capture heat exchanger are cooled and then re-pressurized in the circuit.

Further, it includes a sixth-stage organic Rankine cycle power generation unit. The circulation loop of the sixth-stage organic Rankine cycle power generation unit is the flue gas after the sixth-stage circulating working fluid is pressurized and heat-exchanged by the second-stage flue gas. A circuit that heats, performs expansion and performs heat exchange through the sixth-stage seawater cooler and then re-pressurizes it; performs third-stage flue gas heat exchange on the flue gas heated by the supercharged sixth-stage circulating working fluid.

Further, the LNG evaporation side includes a sequentially connected LNG storage tank, a first-stage LNG booster pump, an LNG heat exchanger, a second-stage LNG booster pump, a carbon capture heat exchanger, a seawater thermostat and a ship. Host, the outlet of the first-stage LNG booster pump is connected to the cold source input end of the LNG heat exchanger, and the cold source output end of the LNG heat exchanger is connected to the input end of the second-stage LNG booster pump. , the output end of the second-stage LNG booster pump is connected to the first cold source input end of the carbon capture heat exchanger, and the first cold source output end of the carbon capture heat exchanger is connected to the seawater thermostat At the input end, the first-stage LNG heat exchange is performed in the LNG heat exchanger.

Further, the flue gas side includes a first-stage flue gas turbine, a first-stage flue gas heat exchanger, a second-stage flue gas turbine, a second-stage flue gas heat exchanger, and a fourth-stage flue gas heat exchanger, which are connected in sequence. Gas heat exchanger, third-stage flue gas heat exchanger, seawater cooler, first flue gas water separator, flue gas diverter, one branch of the flue gas diverter is directly connected to the ship's main engine, and the other branch includes The flue gas precooler, the second flue gas water separator, the flue gas compressor, the second stage circulation evaporator, the carbon capture heat exchanger and the LCO ₂ storage tank are connected in sequence. The first stage flue gas heat exchanger The device performs first-stage flue gas heat exchange, the second-stage flue gas heat exchanger performs second-stage flue gas heat exchange, and the fourth-stage flue gas heat exchanger performs heat exchange with the second-stage flue gas. The flue gas heats the pressurized sixth-stage circulating working fluid, the third-stage flue gas heat exchanger performs third-stage flue gas heat exchange, and the second-stage circulating evaporator performs fourth-stage flue gas heat exchange. The carbon capture heat exchanger performs fifth-stage flue gas heat exchange.

Further, the air side includes an air filter, a first-stage cooler, an air-water separator, a second-stage cooler, a first-stage compressor, a third-stage cooler, and a second-stage compressor connected in sequence. , a fourth-stage cooler, an air throttle valve, a first-stage distillation tower, and a second-stage distillation tower. The flow path of the waste nitrogen output from the upper tower of the first-stage distillation tower includes a third stage connected in sequence. Stage cooler, second stage cooler, first stage cooler, third stage flue gas heat exchanger, waste nitrogen turbine, waste nitrogen and waste argon collector, another one of the waste nitrogen and waste argon collector The input end is connected to the upper tower output end of the second-stage distillation tower. The waste nitrogen and waste argon flow path output by the waste nitrogen and waste argon collector includes a flue gas precooler and a carbon capture heat exchanger that are connected in sequence. device, the cold source output end of the flue gas precooler is connected to the third cold source input end of the carbon capture heat exchanger, and the flow path of the oxygen output from the lower tower of the second-stage distillation tower includes sequentially connected The fourth-stage cooler, oxygen throttle valve, carbon capture heat exchanger and ship main engine, the output end of the oxygen throttle valve is connected to the second cold source input end of the carbon capture heat exchanger, so The second cold source output end of the carbon capture heat exchanger is connected to the main engine of the ship.

Further, the working temperature range of the first-stage circulating working fluid in the first-stage organic Rankine cycle is -100 to 70°C, and the working temperature range of the second-stage circulating working fluid in the second-stage organic Rankine cycle is The temperature range is 25 to 150°C, the working temperature range of the third-stage circulating working fluid in the third-stage organic Rankine cycle is 25 to 115°C, and the fourth-stage of the fourth-stage transcritical Rankine cycle The working temperature range of the circulating working fluid is 25-261°C, the working temperature range of the fifth-stage circulating working fluid in the fifth-stage organic Rankine cycle is 0-85°C, and the working temperature range of the fifth-stage organic Rankine cycle is 0-85°C. The working temperature range of the sixth-stage circulating working fluid is 25~90℃.

Further, the first-stage circulating working fluid is R1150, the second-stage circulating working fluid is n-Pentane, the third-stage circulating working fluid is R600, and the fourth-stage circulating working fluid is CO ₂ , The fifth-stage circulating working fluid is R600, and the sixth-stage circulating working fluid is n-Pentane.

When the air intake conditions of the main engine are met, the present invention constructs the oxygen-rich combustion system of the main engine so that the components of the exhaust smoke are only H ₂ O, CO ₂ and a small amount of Ar, eliminating the complicated steps of separating CO ₂ in the existing technical solutions. It can efficiently capture CO ₂ in the exhaust smoke. At the same time, the present invention utilizes the waste heat and cold energy of the ship in a cascade to achieve the dual goals of energy saving and emission reduction. The advantages compared with the existing technology are:

1. For ship application scenarios, under the conditions of meeting the ship's air intake, based on the principle of "temperature matching, cascade utilization", a single-stage organic Rankine cycle, a transcritical Rankine cycle, and a two-stage organic Rankine cycle are reasonably constructed between hot and cold sources. The cascade Rankine cycle utilizes cascade cold energy and waste heat of ships.

2. Build an oxygen-rich combustion system around the main engine of the ship to obtain flue gas with high concentration of CO ₂ , eliminating the separation and purification steps in the existing technical methods, making it easier to capture; reusing the cold energy of the air separation product for air cooling, Flue gas cooling and carbon capture reduce the energy consumption of the entire ship.

Description of drawings

Figure 1 is a schematic structural diagram of a low-temperature carbon capture coupled cold energy and waste heat cascade utilization system for an LNG-powered ship according to an embodiment of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. After reading this description, those skilled in the art will make various equivalent modifications to this description. All fall within the scope defined by the appended claims of this application.

As shown in Figure 1, the low-temperature carbon capture coupled cold energy and waste heat cascade utilization system for LNG-powered ships involved in the embodiment of the present invention includes:

The LNG evaporation side includes the LNG storage tank 1, the first-stage LNG booster pump 2, the LNG heat exchanger 3, the second-stage LNG booster pump 4, the carbon capture heat exchanger 5, and seawater temperature regulation connected in sequence through pipelines. 6 and ship main engine 7, in which the outlet of the first-stage LNG booster pump 2 is connected to the cold source input end 301 of the LNG heat exchanger 3, and the cold source output end 302 of the LNG heat exchanger 3 is connected to the second-stage LNG booster pump. The inlet of the pump 4 and the outlet of the second-stage LNG booster pump 4 are connected to the first cold source input end 501 of the carbon capture heat exchanger 5, and the first cold source output end 502 of the carbon capture heat exchanger 5 is connected to the seawater regulator. The input terminal of thermostat 6.

The flue gas side includes the first-stage flue gas turbine 8, the first-stage flue gas heat exchanger 9, the second-stage flue gas turbine 10, the second-stage flue gas heat exchanger 11, and the fourth-stage flue gas heat exchanger 11, which are connected through pipelines in sequence. The first-stage flue gas heat exchanger 12, the third-stage flue gas heat exchanger 13, the seawater cooler 14, the first flue gas water separator 15, the flue gas diverter 16, and the branched outflow of the flue gas diverter 16 is directly connected to The main engine of the ship 7, the other path includes the flue gas precooler 17, the second flue gas water separator 18, the flue gas compressor 19, the second stage circulation evaporator 20, the carbon capture heat exchanger 5 and the LCO _2, which are connected in sequence. Storage tank 21, in which the outlet of the first-stage flue gas turbine 8 is connected to the heat source input end 903 of the first-stage flue gas heat exchanger 9, and the heat source output end 904 of the first-stage flue gas heat exchanger 9 is connected to the second-stage flue gas heat exchanger 9. The inlet of the flue gas turbine 10 and the outlet of the second-stage flue gas turbine 10 are connected to the heat source input end 1103 of the second-stage flue gas heat exchanger 11, and the heat source output end 1104 of the second-stage flue gas heat exchanger 11 is connected to the second-stage flue gas heat exchanger 11. The heat source input end 1203 of the fourth-stage flue gas heat exchanger 12 is connected, and the heat source output end 1204 of the fourth-stage flue gas heat exchanger 12 is connected with the heat source input end 1303 of the third-stage flue gas heat exchanger 13. The heat source output end 1304 of the first-stage flue gas heat exchanger 13 is connected to the input end of the seawater cooler 14, the gas output end of the first flue gas water separator 15 is connected to the input end of the flue gas diverter 16, and the output end of the flue gas diverter 16 One end is connected to the ship's main engine 7, and the other end is connected to the heat source input end 1703 of the flue gas precooler 17. The heat source output end 1704 of the flue gas precooler 17 is connected to the output end of the second flue gas water separator 18. The outlet of the gas compressor 19 is connected to the heat source input end 2003 of the second-stage circulation evaporator 20, and the heat source output end 2004 of the second-stage circulation evaporator 20 is connected to the heat source input end 507 of the carbon capture heat exchanger 5. The heat source output 507 of the carbon capture heat exchanger is connected to the LCO ₂ storage tank 21 .

The air side includes an air filter 22, a first-stage cooler 23, an air-water separator 24, a second-stage cooler 25, a first-stage compressor 26, a third-stage cooler 27, and a third-stage cooler 27 connected by pipelines in sequence. The second-stage compressor 28, the fourth-stage cooler 29, the air throttle valve 30, the first-stage distillation tower 31, the second-stage distillation tower 32, and the waste nitrogen output from the upper tower of the first-stage distillation tower 31 The flow path includes a third-stage cooler 27, a second-stage cooler 25, a first-stage cooler 23, a third-stage flue gas heat exchanger 13, a waste nitrogen turbine 33, a waste nitrogen and waste argon collector connected in sequence through pipelines. The other input end of the waste nitrogen and waste argon current collector 34 is connected to the upper tower output end of the second-stage distillation tower 32. The waste nitrogen and waste argon current collector 34 outputs the flow path of the waste nitrogen and waste argon. It includes a flue gas precooler 17, a carbon capture heat exchanger 5 and a fifth-stage circulation condenser 35 that are connected in sequence through pipelines. The flow path of oxygen output from the lower part of the second-stage distillation tower 32 includes a flow path that is connected in sequence through pipelines. The fourth stage cooler 29, oxygen throttle valve 36, carbon capture heat exchanger 5 and ship main engine 7. The output end of the air filter 22 is connected to the heat source input end 2303 of the first-stage cooler 23, and the heat source output end 2304 of the first-stage cooler 23 is connected to the input end of the air-water separator 24. The air-water separator 24 The gas output end is connected to the heat source input end 2503 of the second-stage cooler 25, the heat source output end 2504 of the second-stage cooler 25 is connected to the inlet of the first-stage compressor 26, and the outlet of the first-stage compressor 26 is connected to the The heat source input end 2703 of the third-stage cooler 27, the heat source output end 2704 of the third-stage cooler 27 are connected to the inlet of the second-stage compressor 28, and the outlet of the second-stage compressor 28 is connected to the fourth-stage cooler 29. The heat source input end 2903 and the heat source output end 2904 of the fourth stage cooler 29 are connected to the first stage rectification tower 31 through the air throttle valve 30, and the lower tower output end of the first stage rectification tower 31 is connected to the second stage rectification tower. Distillation tower 32, the tower output end of the first-stage distillation tower 31 is connected to the cold source input end 2701 of the third-stage cooler 27, and the cold source output end 2702 of the third-stage cooler 27 is connected to the second-stage cooler 25 The cold source input end 2501 of the second stage cooler 25 is connected to the cold source input end 2301 of the first stage cooler 23. The cold source output end 2302 of the first stage cooler 23 is connected to the cold source input end 2501 of the second stage cooler 25. The cold source input end 1301 of the third-stage flue gas heat exchanger 13 is connected, the cold source output end 1302 of the third-stage flue gas heat exchanger 13 is connected to the inlet of the waste nitrogen turbine 33, and the waste nitrogen and waste argon are collected. The output end of the device 34 is connected to the cold source input end 1701 of the flue gas precooler 17, and the cold source output end 1702 of the flue gas precooler 17 is connected to the third cold source input end 505 of the carbon capture heat exchanger 5. Connect, the third cold source output end 506 of the carbon capture heat exchanger 5 is connected to the cold source input end 3501 of the fifth stage circulation condenser 35, and the lower tower output end of the second stage rectification tower 32 is connected to the fourth stage The cold source input end 2901 of the cooler 29 is connected, and the cold source output end 2902 of the fourth-stage cooler 29 is connected to the second cold source input end 503 of the carbon capture heat exchanger 5 through the oxygen throttle valve 36. The second cold source output end 504 of the capture heat exchanger 5 is connected to the ship's main engine 7 .

The first-stage organic Rankine cycle power generation unit is composed of a circulation loop including a first-stage circulating working fluid pump 38, a first-stage circulating evaporator 39, a first-stage circulating turbine 37, and an LNG heat exchanger 3. The first-stage The outlet of the circulation turbine 37 is connected to the heat source input end 303 of the LNG heat exchanger 3, and the heat source output end 304 of the LNG heat exchanger 5 is connected to the inlet of the first-stage circulating working fluid pump 38. The first-stage circulating working fluid The outlet of the pump 38 is connected to the cold source input end 3901 of the first-stage circulation evaporator 39 , and the cold source output end 3902 of the first-stage circulation evaporator 39 is connected to the inlet of the first-stage circulation turbine 37 .

The second-stage organic Rankine cycle power generation unit consists of a second-stage circulating working fluid pump 42, a second-stage circulating evaporator 20, a second-stage circulating turbine 40, a first-stage circulating evaporator 39, and a second-stage circulating seawater cooling The outlet of the second-stage circulation turbine 40 is connected to the heat source input end 3903 of the first-stage circulation evaporator 39, and the heat source output end 3904 of the first-stage circulation evaporator 39 is connected to the heat source output end 3904 of the second-stage circulation evaporator 39. The input end of the seawater cooler 41 is connected, the outlet of the second-stage circulating working fluid pump 42 is connected with the cold source input end 2001 of the second-stage circulating evaporator 20, and the cold source output end 2002 of the second-stage circulating evaporator 20 It is connected with the inlet of the second stage circulation turbine 40.

The third-stage organic Rankine cycle power generation unit consists of a third-stage circulating working fluid pump 55, a third-stage circulating preheater 49, a second-stage flue gas heat exchanger 11, a third-stage circulating turbine 53, and a third-stage circulating working fluid pump 55. The seawater cooler 54 is connected to form a circulation loop. The outlet of the third-stage circulation turbine 53 is connected to the input end of the third-stage circulation seawater cooler 54. The output end of the third-stage circulation seawater cooler 54 is connected to the third-stage circulation seawater cooler 54. The inlet of the working fluid pump 55 is connected, the outlet of the third-stage circulating working fluid pump 55 is connected with the cold source input end 4901 of the third-stage circulating preheater 49, and the cold source output end of the third-stage circulating preheater 49 4902 is connected to the cold source input end 1101 of the second-stage flue gas heat exchanger 11, and the cold source output end 1102 of the second-stage flue gas heat exchanger 11 is connected to the inlet of the third-stage circulation turbine 53.

The fourth-stage transcritical Rankine cycle power generation unit consists of a fourth-stage circulating working fluid pump 51, a fourth-stage circulating preheater 52, a fourth-stage circulating regenerator 48, a first-stage flue gas heat exchanger 9, The fourth-stage circulation turbine 47, the third-stage circulation preheater 49 and the fourth-stage circulation seawater cooler 50 are connected to form a circulation loop. The outlet of the fourth-stage circulation turbine 47 and the heat source of the fourth-stage circulation regenerator 48 The input end 4803 is connected, the heat source output end 4804 of the fourth-stage circulation regenerator 48 is connected with the heat source input end 4903 of the third-stage circulation preheater 49, and the heat source output end 4904 of the third-stage circulation preheater 49 is connected with The input end of the fourth-stage circulating seawater cooler 50 is connected, the output end of the fourth-stage circulating seawater cooler 50 is connected with the inlet of the fourth-stage circulating working fluid pump 51, and the outlet of the fourth-stage circulating working fluid pump 51 is connected with The cold source input end 5201 of the fourth-stage circulation preheater 52 is connected, and the cold source output end 5202 of the fourth-stage circulation preheater 52 is connected with the cold source input end 4801 of the fourth-stage circulation regenerator 48. The cold source output end 4802 of the four-stage circulation regenerator 48 is connected to the cold source input end 901 of the first-stage flue gas heat exchanger 9, and the cold source output end 902 of the first-stage flue gas heat exchanger 9 is connected to the fourth-stage flue gas heat exchanger 9. The inlets of the stage circulation turbine 47 are connected.

The fifth-stage organic Rankine cycle power generation unit includes a fifth-stage circulating working fluid pump 45, a fifth-stage circulating regenerator 44, a fifth-stage circulating evaporator 46, a fifth-stage circulating turbine 43, and a fifth-stage circulating condensation unit. The outlet of the fifth-stage circulating turbine 43 is connected to the heat source input end 4403 of the fifth-stage circulating regenerator 44, and the heat source output end 4404 of the fifth-stage circulating regenerator 44 is connected to the fifth-stage circulating regenerator 44. The heat source input end 3503 of the first-stage circulation condenser 35 is connected, the heat source output end 3504 of the fifth-stage circulation condenser 35 is connected with the inlet of the fifth-stage circulating working fluid pump 45, and the outlet of the fifth-stage circulating working fluid pump 45 is connected with The cold source input end 4401 of the fifth-stage circulation regenerator 44 is connected, and the cold source output end 4402 of the fifth-stage circulation regenerator 44 is connected with the cold source input end 4601 of the fifth-stage circulation evaporator 46. The cold source output end 4602 of the first-stage circulation evaporator 46 is connected to the inlet of the fifth-stage circulation turbine 43 .

The sixth-stage organic Rankine cycle power generation unit is composed of a sixth-stage circulating working fluid pump 58, a fourth-stage flue gas heat exchanger 12, a sixth-stage circulating turbine 56, and a sixth-stage circulating seawater cooler 57. In the loop, the outlet of the sixth-stage circulating turbine 56 is connected to the inlet of the sixth-stage circulating seawater cooler 57, and the outlet of the sixth-stage circulating seawater cooler 57 is connected to the inlet of the sixth-stage circulating working fluid pump 58. The outlet of the six-stage circulating working fluid pump 58 is connected to the cold source input end 1201 of the fourth-stage flue gas heat exchanger 12, and the cold source output end 1202 of the fourth-stage flue gas heat exchanger 12 is connected to the sixth-stage circulating turbine. 56 entrances are connected.

Combined with the 296,600-ton VLCC-LNG power ship, the working process of each part of the low-temperature carbon capture coupling cold energy and waste heat cascade utilization system of the LNG power ship in this embodiment is further explained. The LNG components in the LNG storage tank are 95% methane, 3% ethane, and 2% propane. The air components are 78.1% nitrogen, 20.9% oxygen, 0.94% argon, 0.03% carbon dioxide, and 0.03% water vapor. The components of oxygen (not pure oxygen) flowing into the engine are 98.35% oxygen and 1.65% argon. Since the oxygen introduced in this example is not pure oxygen, in order to achieve zero carbon emissions in the system, the circulating _CO2 components are adjusted to 94.31% carbon dioxide, 2.82% argon, and 2.87% water vapor.

Process parameter description:

LNG process: LNG (3000kg/h, 600kPa, -162℃) comes out of the LNG storage tank 1, and is boosted to 15MPa (-154.3℃) by the first-stage LNG booster pump 2, and then is replaced by the LNG Heater 3 exchanges heat with the first-stage circulating working fluid (R1150, 150kPa, -51.43℃) to -91.08℃. Then it is boosted to 30Mpa (-75.82) by the second-stage LNG booster pump 4 for a second time, and then enters the low-temperature carbon capture heat exchanger 5 to exchange heat and raise the temperature to 0°C. At this time, the LNG can use cold

Less, the heat is directly transferred to the ship's main engine 7 through the seawater thermostat 6 to 15°C.

Flue gas flow: The flue gas (350°C, 500kPa, 196070kg/h) discharged by the ship's main engine 7 passes through the first-stage flue gas turbine 8 to do work (the turbine outlet pressure here is limited to 150kPa or more), and the flue gas after doing the work (150kPa , 266°C) in the first-stage flue gas heat exchanger 9 exchanges heat with the fourth-stage circulating working fluid (CO ₂ , 126.9°C) coming out of the fourth-stage circulating regenerator 48. The heat-exchanged flue gas ( 150kPa, 144.4℃) is expanded by the second-stage flue gas turbine 10 to 110kPa (123.6℃), and then in the second-stage flue gas heat exchanger 11, it is combined with the fifth-stage gas from the fifth-stage circulation preheater 49 The circulating working fluid (R600, 80℃) cools down to 94.07℃ through heat exchange. Then, the fourth-stage flue gas heat exchanger 12 provides heat to the sixth-stage Rankine cycle working fluid (n-Pentane, 25.16°C), cools it to 77.63°C, and then heats it with the third-stage flue gas heat exchanger 13. The waste nitrogen (623kPa, 8.114℃) exchanges heat to 73.08℃ and then passes through the seawater cooler 14 to 25℃. After that, most of the water is separated by the first flue gas water separator 15 and then divided into parts by the flue gas diverter 16. There are two streams, one stream is sent to the ship's main engine 7 as circulating flue gas, and the other stream captures carbon.

Capture process: The captured flue gas (9108kg/h, 110kPa, 25°C) flowing out from the flue gas diverter 16 is combined with the waste nitrogen coming out of the waste nitrogen and waste argon collector 34 in the flue gas precooler 17 (110kPa, -70.45℃) to cool down to -52℃ through heat exchange, and then separate the water through the second flue gas water separator 18. The captured flue gas (8995kg/h) obtained is pressurized to 1950kPa ( 202.9°C), and then cooled to 67.59°C through heat exchange with the second-stage circulating working fluid (25.75°C) through the second-stage circulation evaporator 20, and finally the captured flue gas passes through the carbon capture heat exchanger 5 and oxygen (-110.8 ℃), waste nitrogen (-50.19℃) and LNG (-75.82℃) exchange heat, and are liquefied at -36.5℃ and 1950kPa to complete the capture and send it to the LCO ₂ storage tank 21.

Air separation process: The air (25°C, 110kPa, 52250kg/h) is filtered with impurities through the air filter 22, and is mixed with the waste nitrogen (-87.94°C, 623kPa) heat exchange, after the temperature drops to -52°C, the water is separated through the air-water separator 24, and then in the second-stage cooler 25, it is mixed with the waste nitrogen (-175.9°C, 623kPa, steam) coming out of the third-stage cooler 27. The phase separation ratio is 0.7356) and is cooled to -162°C by heat exchange and then pressurized to 570kPa (-69.38°C) by the first-stage compressor 26, and then mixed with the liquid from the fourth-stage cooler 29 in the third-stage cooler 27. Waste nitrogen (-176.1℃, 623kPa, liquid phase fraction 1) is cooled to -162℃ by heat exchange. It is further pressurized to 1600kPa (-109.5°C) in the second-stage compressor 28, and then the air and the liquid oxygen (-182.7°C, 112kPa) discharged from the lower tower of the second-stage distillation tower 32 are cooled in the fourth stage. The heat exchanger in the device 29 cools down to -157°C, and then passes through the air throttle valve 30, the pressure drops to 1200kPa, and the temperature drops to -162°C. The air flowing out from the air throttle valve 30 enters the first-stage distillation tower 31 for separation. Liquid oxygen (625kPa, -161.7°C, O ₂ mole fraction 0.9546) flows out from the bottom, and waste nitrogen (623kPa, liquid phase separation) flows out from the top. rate 1, -176.1°C) as a cold source and sequentially enters the third-stage cooler 27, the second-stage cooler 25, the first-stage cooler 23 and the third-stage flue gas heat exchanger 13 to exchange heat and heat up to 27°C. Then it enters the waste nitrogen turbine 33 and expands to 110kPa (-68.04℃). The waste nitrogen after work is mixed with the waste argon discharged from the upper tower of the second-stage distillation tower 32 through the waste nitrogen and waste argon collector 34, and then exchanges heat with the captured flue gas (25°C) in the flue gas precooler 17 to increase the temperature. to -50.19°C, and then enters the low-temperature carbon capture heat exchanger 5 to provide cooling. The waste nitrogen (-17.89) that comes out is then used as the fifth-stage circulating working fluid (R600) in the fifth-stage circulation condenser 35 of the heat exchanger. , 8℃) provides cooling capacity and then discharges it. The liquid oxygen discharged from the lower tower of the first-stage distillation tower 31 enters the second-stage distillation tower 32 for further separation and purification. The waste argon (110kPa, -192°C) flowing out from the top passes through the waste nitrogen and waste argon collector 34 and waste nitrogen. After mixing, the oxygen flowing out from the bottom (112kPa, -182.3℃, O2 mole fraction 0.9835, liquid phase fraction 1) enters the fourth-stage cooler 29 as a cold source for heat exchange, and the temperature rises to -110.8℃, and then passes through the oxygen section The pressure of the flow valve 36 is reduced to 110 kPa, and then used as a cold source in the carbon capture heat exchanger 5 to heat up to 20°C and send it to the ship's main engine 7 .

First-stage organic Rankine cycle: The first-stage circulating working fluid (R1150, -51.43℃, 150kPa, 1210kg/h) after the first-stage circulating turbine 37 generates power and exhaust steam is mixed with LNG ( -154.3) After exchanging heat to -100°C, it is pressurized to 2000kPa (-98.69°C) by the first-stage circulating working fluid pump 38, and then mixed with the second-stage circulating working fluid (94.25°C) in the first-stage circulating evaporator 39 The heat exchanger increases the temperature to 66°C, and finally the first-stage circulation turbine 37 performs work, completing a cycle.

Second-stage organic Rankine cycle: the second-stage circulating working fluid (n-Pentane, 94.25°C, 110kPa, 2100kg/h) after the second-stage circulating turbine 40 generates power and exhaust steam is in the first-stage circulating evaporator 39 It exchanges heat with the first-stage circulating working fluid (-98.69°C) and cools it to 36.87°C, then exchanges heat to 25°C through the first-stage circulating seawater cooler 41, and then pressurizes it to 1400kPa (25.75) through the second-stage circulating working fluid pump 42. ℃), and then exchange heat with the captured flue gas (202.9°C) compressed by the flue gas compressor 19 in the second-stage circulation evaporator 20 to raise the temperature to 150°C, and finally work through the second-stage circulation turbine 40 to complete A cycle.

The third-stage organic Rankine cycle: the fifth-stage circulating working fluid (R600, 66.54°C, 250kPa, 15600kg/h) after the third-stage circulating turbine 53 generates power and exhaust steam, passes through the third-stage circulating seawater cooler 54 for heat exchange to 25°C, and then pressurized to 1500kPa (25.93°C) by the third-stage circulating working fluid pump 55, and then exchange heat with the fourth-stage circulating working fluid (90°C) in the third-stage circulating preheater 49 to raise the temperature to 80 ℃, and further exchanges heat with the flue gas (123.6 ℃) in the second-stage flue gas heat exchanger 11 to raise the temperature to 115 ℃, and finally performs work through the third-stage circulation turbine 53 to complete a cycle.

Fourth-stage transcritical Rankine cycle: The fourth-stage circulating working fluid (CO ₂ , 165.1°C, 6750kPa, 126000kg/h) after the fourth-stage cycle turbine 47 generates work and exhausts steam first circulates in the fourth-stage regenerator 48 to 90°C, and then exchange heat with the third-stage circulating working fluid (R600, 25.93°C) pressurized by the third-stage circulating working fluid pump 55 in the third-stage circulating preheater 49, and cool to After reaching 76.53°C, the heat is exchanged to 25°C through the fourth-stage circulating seawater cooler 50, and then pressurized to 20000kPa (53.7°C) through the fourth-stage circulating working fluid pump 51. Then the fourth-stage circulating working fluid first exchanges heat with the high-temperature jacket water cooling water (90°C) in the fourth-stage circulating preheater 52 to raise the temperature to 85°C, and then reheats it in the fourth-stage circulating regenerator 48 to 126.9°C. Finally, it exchanges heat with the flue gas (266°C) in the first-stage flue gas heat exchanger 9 and the temperature rises to 260.5°C. Then, the fourth-stage circulating turbine 47 performs work, completing a cycle.

The fifth-stage organic Rankine cycle: the fifth-stage circulating working fluid (R600, 27.95℃, 110kPa, 2190kg/h) after the fifth-stage circulating turbine 43 generates work and exhaust steam, exchanges heat through the fifth-stage circulating regenerator 44 After the temperature is cooled to 8°C, it is cooled to 0°C through heat exchange with waste nitrogen (-17.82) in the fifth-stage circulating condenser 35. Then it is pressurized to 1100kPa (0.63°C) through the fifth-stage circulating working fluid pump 45 and then enters the fifth-stage circulating working fluid pump 45. The first-stage circulation regenerator 44 reheats the heat to 15.26°C, and further exchanges heat with the high-temperature jacket water cooling water (90°C) in the fifth-stage circulation evaporator 46 to raise the temperature to 85°C, and finally generates work through the fifth-stage circulation turbine 43 , complete a cycle.

Sixth-stage organic Rankine cycle: The sixth-stage circulating working fluid (n-Pentane, 64.97℃, 110kPa, 6500kg/h) after the sixth-stage circulating turbine 56 generates power and exhaust steam passes through the sixth-stage circulating seawater cooler 57 After the heat is exchanged to 25°C, it is pressurized to 390kPa (25.16°C) by the sixth-stage circulating working fluid pump 58, and then it is heated to 88°C by exchanging heat with the flue gas (94.07°C) in the fourth-stage flue gas heat exchanger 12. Finally, the sixth stage cycle turbine 56 performs work, completing a cycle.

Claims

A low-temperature carbon capture coupling cold energy and waste heat cascade utilization system for LNG-powered ships, which is characterized by including:

On the LNG evaporation side, the LNG coming out of the LNG storage tank undergoes first-stage pressurization, first-stage LNG heat exchange, second-stage pressurization, second-stage LNG heat exchange and seawater temperature adjustment to form NG and send it to the main engine;

On the flue gas side, the flue gas discharged by the host undergoes the first-stage flue gas expansion work, the first-stage flue gas heat exchange, the second-stage flue gas expansion work, the second-stage flue gas heat exchange, and the third-stage flue gas heat exchange. After cooling with sea water, the water is separated through the first flue gas water separator, and further divided into two paths, one is sent to the main engine, and the other path passes through the flue gas precooler, the second flue gas water separator, and the flue gas compressor in sequence. After the fourth-stage flue gas heat exchange and the fifth-stage flue gas heat exchange, the low-temperature liquefaction capture is completed and sent to the LCO 2 storage tank;

The air side includes a flow path in which the air is sequentially subjected to multi-stage cooling and pressurization and two-stage rectification. The waste nitrogen formed after the air passes through the two-stage rectification is used to perform multi-stage cooling and pressurization of the air in addition to the final stage cooling. The front-stage cooling then absorbs heat energy through the third-stage flue gas heat exchanger and then performs work through the waste nitrogen turbine. The waste argon formed after the air undergoes the two-stage distillation is mixed with the waste nitrogen coming out of the waste nitrogen turbine. , and then provide cold energy to the flue gas precooler and carbon capture heat exchanger in sequence and then discharge the air. The liquid oxygen formed after the two-stage distillation of the air is used for the final cooling of the air before carbon capture. The heat exchanger regasifies and sends it to the main engine;

The first-stage organic Rankine cycle power generation unit, the circulation loop of the first-stage organic Rankine cycle power generation unit is that the first-stage circulating working fluid is pressurized and heated by the second-stage circulating working fluid in the first-stage circulating evaporator, And carry out a circuit in which the first-stage LNG heat exchanges and then pressurizes again after the expansion work;

A second-stage organic Rankine cycle power generation unit. The circulation loop of the second-stage organic Rankine cycle power generation unit heats and expands the flue gas from the flue gas compressor after the second-stage circulating working fluid is pressurized. After the work is done, the circuit sequentially passes through the first-stage circulating evaporator and the second-stage circulating seawater cooler to exchange heat and then re-pressurize;

The third-stage organic Rankine cycle power generation unit. The circulation loop of the third-stage organic Rankine cycle power generation unit is that the third-stage circulating working fluid is pressurized and then exchanges heat with the flue gas through the third-stage circulation preheater. The second-stage flue gas heat exchange is carried out, and after expansion and work are performed, the heat is exchanged through the third-stage circulating seawater cooler and then re-pressurized;

The fourth-stage transcritical Rankine cycle power generation unit, the circulation loop of the fourth-stage transcritical Rankine cycle power generation unit is that the working fluid of the fourth-stage transcritical Rankine cycle is pressurized and sequentially preheated by high-temperature cylinder liner cooling water, The fourth-stage circulating regenerator regenerates heat and exchanges heat with the flue gas in the first-stage flue gas. After expansion and work, it passes through the fourth-stage circulating regenerator, the third-stage circulating preheater and the fourth-stage circulating sea water. A circuit in which the cooler exchanges heat and then re-pressurizes it.

Among them, the first-stage LNG heat exchange is for LNG to provide cold energy to the first-stage organic Rankine cycle working fluid, and the second-stage LNG heat exchange is for LNG to provide cold energy to the carbon capture heat exchanger. The first-stage flue gas heat exchange is for the flue gas to provide thermal energy to the fourth-stage Rankine cycle working fluid. The second-stage flue gas heat exchange is for the flue gas to provide thermal energy to the third-stage Rankine cycle working fluid. The third-stage flue gas heat exchanger is The first-stage flue gas heat exchange is to provide thermal energy from the flue gas to the waste nitrogen after primary cooling of the air. The fourth-stage flue gas heat exchange is to provide the flue gas compressed by the flue gas compressor with thermal energy to the second-stage circulating working fluid. Release thermal energy. The fifth-stage flue gas heat exchange is that the flue gas releases thermal energy to the carbon capture heat exchanger. In the carbon capture heat exchanger, the second-stage pressurized LNG, The oxygen after final-stage cooling of the air and the waste nitrogen and waste argon after heat exchange in the flue gas precooler jointly absorb heat to the flue gas after heat exchange with the second-stage circulating working fluid.
The low-temperature carbon capture coupling cold energy and waste heat cascade utilization system for LNG powered ships according to claim 1, characterized in that it includes a fifth-stage organic Rankine cycle power generation unit, and the fifth-stage organic Rankine cycle power generation unit The circulation loop is that the fifth-stage circulating working fluid is pressurized and then passes through the fifth-stage circulating regenerator for heat exchange and is then heated by the high-temperature cylinder liner cooling water. After expansion and work, it sequentially passes through the fifth-stage circulating regenerator for heat exchange and A circuit in which waste nitrogen and argon coming out of the carbon capture heat exchanger are cooled and then re-pressurized.
The low-temperature carbon capture coupling cold energy and waste heat cascade utilization system for LNG powered ships according to claim 2, characterized in that it includes a sixth-stage organic Rankine cycle power generation unit, and the sixth-stage organic Rankine cycle power generation unit The circulation loop is a circuit in which the sixth-stage circulating working fluid is pressurized and heated by the flue gas after heat exchange with the second-stage flue gas, and after expansion and work, it is heat-exchanged through the sixth-stage seawater cooler and then re-pressurized; the supercharged The flue gas heated by the sixth-stage circulating working fluid is then subjected to the third-stage flue gas heat exchange.
The low-temperature carbon capture coupling cold energy and waste heat cascade utilization system of an LNG powered ship according to claim 1, characterized in that the LNG evaporation side includes a sequentially connected LNG storage tank, a first-stage LNG booster pump, an LNG exchanger heater, second-stage LNG booster pump, carbon capture heat exchanger, seawater thermostat and ship main engine, the outlet of the first-stage LNG booster pump is connected to the cold source input end of the LNG heat exchanger, The cold source output end of the LNG heat exchanger is connected to the input end of the second-stage LNG booster pump, and the output end of the second-stage LNG booster pump is connected to the first cold source of the carbon capture heat exchanger. The source input end, the first cold source output end of the carbon capture heat exchanger is connected to the input end of the seawater thermostat, and the first-stage LNG heat exchange is performed in the LNG heat exchanger.
The low-temperature carbon capture coupled cold energy and waste heat cascade utilization system for LNG powered ships according to claim 3, wherein the flue gas side includes a first-stage flue gas turbine, a first-stage flue gas exchanger, and a first-stage flue gas turbine connected in sequence. Heater, second-stage flue gas turbine, second-stage flue gas heat exchanger, fourth-stage flue gas heat exchanger, third-stage flue gas heat exchanger, seawater cooler, first flue gas water separator, Flue gas diverter, one branch of the flue gas diverter is directly connected to the ship's main engine, and the other path includes a flue gas precooler, a second flue gas water separator, a flue gas compressor, and a second-stage circulation connected in sequence Evaporator, carbon capture heat exchanger and LCO2 storage tank, the first-stage flue gas heat exchanger performs first-stage flue gas heat exchange, and the second-stage flue gas heat exchanger performs second-stage flue gas heat exchange Heat exchange, in the fourth-stage flue gas heat exchanger, the flue gas after heat exchange with the second-stage flue gas heats the pressurized sixth-stage circulating working fluid, and the third-stage flue gas heat exchanger performs the third-stage flue gas heat exchanger. Three-stage flue gas heat exchange, the second-stage circulation evaporator performs the fourth-stage flue gas heat exchange, and the carbon capture heat exchanger performs the fifth-stage flue gas heat exchange.
The low-temperature carbon capture coupled cold energy and waste heat cascade utilization system for LNG-powered ships according to claim 1, wherein the air side includes an air filter, a first-stage cooler, and an air-water separator connected in sequence. , second-stage cooler, first-stage compressor, third-stage cooler, fourth-stage cooler, air throttle valve, first-stage distillation tower, second-stage distillation tower, the first-stage distillation tower The flow path of waste nitrogen output from the upper tower of the distillation tower includes a third-stage cooler, a second-stage cooler, a first-stage cooler, a third-stage flue gas heat exchanger, a waste nitrogen turbine, and a waste nitrogen Waste nitrogen and waste argon current collector, the other input end of the waste nitrogen and waste argon current collector is connected to the upper tower output end of the second stage distillation tower, the waste nitrogen and waste argon waste output from the waste nitrogen and waste argon current collector The flow path includes a flue gas precooler and a carbon capture heat exchanger connected in sequence. The cold source output end of the flue gas precooler is connected to the third cold source input end of the carbon capture heat exchanger, so The flow path of the oxygen output from the lower tower of the second-stage distillation tower includes a fourth-stage cooler, an oxygen throttle valve, a carbon capture heat exchanger and a ship main engine connected in sequence. The output end of the oxygen throttle valve is connected to the The second cold source input end of the carbon capture heat exchanger is connected, and the second cold source output end of the carbon capture heat exchanger is connected to the ship's main engine.
The low-temperature carbon capture coupled cold energy and waste heat cascade utilization system for LNG powered ships according to claim 1, characterized in that the working temperature range of the first-stage circulating working fluid in the first-stage organic Rankine cycle is - 100-70℃, the working temperature range of the second-stage circulating working fluid in the second-stage organic Rankine cycle is 25-150℃, and the working temperature range of the third-stage circulating working fluid in the third-stage organic Rankine cycle is The working temperature range is 0~85℃, and the working temperature range of the fourth-stage circulating working fluid in the fourth-stage transcritical Rankine cycle is 25~261℃,
The low-temperature carbon capture coupling cold energy and waste heat cascade utilization system for LNG powered ships according to claim 3, characterized in that the working temperature range of the fifth-stage circulating working fluid in the fifth-stage organic Rankine cycle is 25 ~115°C, and the working temperature range of the sixth-stage circulating working fluid in the sixth-stage organic Rankine cycle is 25-90°C.
The low-temperature carbon capture coupled cold energy and waste heat cascade utilization system for LNG powered ships according to claim 7, characterized in that the first-stage circulating working fluid is R1150, and the second-stage circulating working fluid is n-Pentane , the third-stage circulating working fluid is R600, and the fourth-stage circulating working fluid is CO 2 ,
The low-temperature carbon capture coupled cold energy and waste heat cascade utilization system for LNG powered ships according to claim 8, characterized in that the fifth-stage circulating working fluid is R600, and the sixth-stage circulating working fluid is n-Pentane. .