A main engine exhaust gas carbon collection system and a control method thereof, and a dual-fuel LNG ship

Abstract

This invention discloses a main engine exhaust carbon collection system and its control method, as well as a dual-fuel LNG ship. By setting a carbon recovery pipeline on the main engine exhaust pipe and integrating the carbon recovery pipeline with the gas supply system of the ship's main engine, CO2 in the main engine exhaust gas is recovered through physical phase change. This can ensure the purity of dry ice preparation and effectively remove CO2 from the main engine exhaust gas emitted into the atmosphere, thereby reducing direct CO2 emissions.

Description

Technical Field

[0001] This invention relates to the field of shipbuilding technology, and in particular to a main engine exhaust carbon collection system and its control method, and a dual-fuel LNG carrier. Background Technology

[0002] In recent years, green development has become the theme of the shipbuilding industry, with carbon neutrality and zero-carbon goals attracting significant attention. While hydrogen energy, as the cleanest energy source, meets future development requirements, its high manufacturing cost and immature safety technologies prevent it from becoming the mainstream energy source. Currently, the main energy sources for ships are fuel oil and the newer LNG, both of which contain large amounts of carbon. Combustion of these fuels produces significant amounts of CO2 and other carbon oxides, exacerbating the greenhouse effect. While desulfurization and denitrification technologies exist for treating ship main engine exhaust, carbon treatment or collection technologies are lacking. Therefore, it is necessary to design a carbon collection system for ship main engine exhaust. Summary of the Invention

[0003] In view of this, the present invention provides a main engine exhaust carbon collection system and control method thereof, and a dual-fuel LNG ship, for collecting CO2 from the exhaust gas of the main engine of a dual-fuel LNG ship.

[0004] A main engine exhaust carbon collection system includes a first heat exchange device and a second heat exchange device. The cold-side inlet and outlet of the first heat exchange device and the second heat exchange device are both connected to the gas supply pipeline of the main engine gas supply system, and the hot-side inlet and outlet are both connected to the carbon recovery condensation pipeline.

[0005] The LNG drawn from the cargo tank by the main engine gas supply system first passes through a second heat exchange device, then through a first heat exchange device, and finally enters the main engine for combustion.

[0006] The carbon recovery condensation pipeline is connected to the main unit's exhaust pipe so that the high-temperature exhaust gas discharged from the main unit first passes through the first heat exchange device, where it exchanges heat with LNG to condense and liquefy the gas components in the exhaust gas with boiling points higher than CO2. Then it passes through the second heat exchange device, where it exchanges heat with LNG again to sublimate the CO2 in the exhaust gas into dry ice. Finally, it is discharged to the outside atmosphere through the carbon recovery condensation pipeline.

[0007] Preferably, the end of the main unit exhaust pipe is also connected to a proportional distributor. The first outlet of the proportional distributor is connected to the inlet of the carbon recovery condenser pipe, and the second outlet is connected to an exhaust branch pipe. The outlet of the exhaust branch pipe merges into the end of the carbon recovery condenser pipe. The proportional distributor is used to distribute the high-temperature exhaust gas discharged from the main unit so that part of the exhaust gas flows into the carbon recovery condenser pipe and the other part of the exhaust gas flows into the exhaust branch pipe.

[0008] Preferably, it also includes a mixer, the outlet of the exhaust branch pipe is connected to the first inlet of the mixer, the outlet of the carbon recovery condensation pipe is connected to the second inlet of the mixer, and the outlet of the mixer is connected to a tail gas discharge pipe.

[0009] Preferably, the carbon recovery condenser pipeline is equipped with a first temperature sensor for detecting the exhaust gas temperature T1 before entering the first heat exchanger, a second temperature sensor for detecting the exhaust gas temperature T2 discharged from the first heat exchanger, and a third temperature sensor for detecting the exhaust gas temperature T3 discharged from the second heat exchanger.

[0010] A fourth temperature sensor is installed on the exhaust pipe to detect the final exhaust gas temperature T4. The first, second, third and fourth temperature sensors are all electrically connected to the controller.

[0011] Preferably, the exhaust gas temperature T2 discharged from the first heat exchange device is controlled between -60°C and -70°C, and the exhaust gas temperature T3 discharged from the second heat exchange device is controlled between -90°C and -100°C.

[0012] Preferably, the main unit's gas supply system includes a cryogenic pump, a first gas supply pipe, a second gas supply pipe, a third gas supply pipe, a fourth gas supply pipe, a fifth gas supply pipe, a first control valve, and a second control valve.

[0013] A cryogenic pump is installed on the first gas supply pipe. One end of the first gas supply pipe extends to the lower part of the LNG cargo tank, and the other end is connected to the cold side inlet of the second heat exchange device. One end of the second gas supply pipe is connected to the cold side outlet of the second heat exchange device, and the other end is connected to the cold side inlet of the first heat exchange device. A first control valve is installed on the second gas supply pipe. One end of the third gas supply pipe is connected to the cold side outlet of the first heat exchange device, and the other end is connected to the first valve port of the second control valve. The second valve port of the second control valve is connected to the fuel inlet of the main engine through the fourth gas supply pipe. The third valve port of the second control valve is connected to the fifth gas supply pipe, and the end of the fifth gas supply pipe extends to the upper part of the LNG cargo tank.

[0014] Preferably, the first control valve is provided with a bypass pipe, which is connected to the first valve port of the second control valve.

[0015] Preferably, a fan is also provided on the carbon recovery condenser pipeline, and the fan is located downstream of the second heat exchange device.

[0016] A control method for a main engine exhaust carbon collection system specifically includes the following steps:

[0017] The LNG in the liquid cargo tank is supplied to the main engine for combustion via the main engine gas supply system.

[0018] Part of the exhaust gas emitted during the combustion of the main engine flows into the carbon recovery and condensation pipe, and the other part flows into the exhaust branch pipe.

[0019] The high-temperature exhaust gas flowing into the carbon recovery condenser pipeline first passes through the first heat exchange device, where it exchanges heat with LNG to condense and liquefy the gas components in the exhaust gas with boiling points higher than CO2. Then it passes through the second heat exchange device, where it exchanges heat with LNG again to sublimate the CO2 in the exhaust gas into dry ice. Finally, the exhaust gas discharged from the second heat exchange device flows into the mixer through the carbon recovery condenser pipeline, where it mixes with the high-temperature exhaust gas in the exhaust branch pipe, and is then discharged to the outside atmosphere from the exhaust gas discharge pipe.

[0020] During carbon recovery, the fourth temperature sensor detects the final exhaust gas temperature T4 released into the atmosphere in real time to control the valve opening of the proportional distributor to adjust the exhaust gas distribution ratio flowing into the carbon recovery condensate pipe and the exhaust branch pipe. The second temperature sensor detects the exhaust gas temperature T2 discharged from the first heat exchange device in real time to control the valve opening of the first control valve to keep the exhaust gas temperature T2 between -60℃ and -70℃. The third temperature sensor detects the exhaust gas temperature T3 discharged from the second heat exchange device in real time to control the cryogenic pump to keep the exhaust gas temperature T3 between -90℃ and -100℃.

[0021] A dual-fuel LNG carrier that uses the method described above to collect CO2 from the exhaust gas of the dual-fuel main engine.

[0022] A dual-fuel LNG carrier includes the aforementioned main engine exhaust carbon collection system.

[0023] The beneficial effects of this invention are:

[0024] 1. This invention integrates a carbon recovery pipeline into the main engine exhaust pipe and the gas supply system of the ship's main engine, using a physical phase change method to recover CO2 from the main engine exhaust gas. This ensures the purity of dry ice preparation and effectively removes CO2 from the main engine exhaust gas emitted into the atmosphere, reducing direct CO2 emissions.

[0025] 2. This invention can achieve automatic control of exhaust gas CO2 collection by setting the temperature at each key point and adjusting the program according to the specific design.

[0026] 3. This invention uses a proportional distributor installed at the outlet of the main unit's exhaust pipe to distribute the high-temperature exhaust gas discharged from the main unit to the carbon recovery condensation pipe and the exhaust branch pipe in a proportional manner. The high-temperature exhaust gas flowing into the carbon recovery condensation pipe undergoes two heat exchange treatments, namely gas condensation and CO2 sublimation into dry ice, and becomes low-temperature exhaust gas. This low-temperature exhaust gas mixes with the high-temperature exhaust gas in the exhaust branch pipe before being discharged into the atmosphere. This ensures that the temperature of the mixed exhaust gas discharged into the atmosphere is higher than the freezing point, preventing water vapor from the high-temperature exhaust gas from freezing at the end of the pipe and preventing water vapor in the air from freezing at the end of the pipe. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the carbon collection system for the main engine exhaust gas in Embodiment 1.

[0029] Figure 2 This is a schematic diagram of the carbon collection system for the main engine exhaust gas in Example 2.

[0030] Figure 3 This is a schematic diagram of the carbon collection system for the main engine exhaust gas in Example 3.

[0031] Figure 4 This is a schematic diagram of the carbon collection system for the main engine exhaust gas in Example 4.

[0032] The meanings of the labels in the diagram are as follows:

[0033] 1 is the main unit, 2 is the proportional distributor, 3 is the first heat exchanger, 4 is the second heat exchanger, 5 is the fan, 6 is the controller, 7 is the liquid cargo tank, 8 is the cryogenic pump, 9 is the first control valve, 10 is the second control valve, 11 is the mixer, 12 is the carbon recovery condensate pipeline, 13 is the main unit exhaust pipe, 14 is the exhaust branch pipe, 15 is the tail gas discharge pipe, 16 is the first gas supply pipe, 17 is the second gas supply pipe, 18 is the third gas supply pipe, 19 is the fourth gas supply pipe, 20 is the fifth gas supply pipe, 21 is the bypass pipe, T1-T4 are temperature signals, and L1 is the main unit operation signal. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below with reference to specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0035] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0036] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various information, such information should not be limited to these terms and should not be construed as indicating or implying relative importance. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0037] To better understand the technical solution of the present invention, the present invention will be described in detail below with reference to the accompanying drawings.

[0038] Example 1: The present invention provides a carbon collection system for main engine exhaust gas, including a first heat exchange device 3 and a second heat exchange device 4. The cold side inlet and outlet of the first heat exchange device 3 and the second heat exchange device 4 are both connected to the gas supply pipeline of the main engine gas supply system, and the hot side inlet and outlet are both connected to the carbon recovery condensation pipeline 12.

[0039] The LNG extracted from the liquid cargo tank 7 by the main engine gas supply system first passes through the second heat exchange device 4, then through the first heat exchange device 3, and finally enters the main engine 1 for combustion.

[0040] Specifically, the main engine gas supply system includes a cryogenic pump 8, a first gas supply pipe 16, a second gas supply pipe 17, a third gas supply pipe 18, a fourth gas supply pipe 19, a fifth gas supply pipe 20, a first control valve 9, and a second control valve 10. The cryogenic pump 8 is installed on the first gas supply pipe 16. One end of the first gas supply pipe 16 extends to the lower part of the LNG cargo tank 7, and the other end is connected to the cold side inlet of the second heat exchange device 4. One end of the second gas supply pipe 17 is connected to the cold side outlet of the second heat exchange device 4, and the other end is connected to the cold side inlet of the first heat exchange device 3. The first control valve 9 is installed on the second gas supply pipe 17. One end of the third gas supply pipe 18 is connected to the cold side outlet of the first heat exchange device 3, and the other end is connected to the first valve port of the second control valve 10. The second valve port of the second control valve 10 is connected to the fuel inlet of the main engine 1 through the fourth gas supply pipe 19. The third valve port of the second control valve 10 is connected to the fifth gas supply pipe 20, and the end of the fifth gas supply pipe 20 extends to the upper part of the LNG cargo tank 7.

[0041] The carbon recovery condenser pipe 12 is connected to the main unit exhaust pipe 13 so that the high-temperature exhaust gas discharged from the main unit first passes through the first heat exchange device 3, where it exchanges heat with LNG to condense and liquefy the gas components in the exhaust gas with boiling points higher than CO2. Then it passes through the second heat exchange device 4, where it exchanges heat with LNG again to sublimate the CO2 in the exhaust gas into dry ice. Finally, it is discharged to the outside atmosphere through the carbon recovery condenser pipe 12.

[0042] The cargo tank 7 is the cargo tank of the LNG ship, which stores cryogenic liquid LNG at -163℃. After the cryogenic pump 8 extracts the LNG, it is transported to the cold side inlet of the second heat exchange device 4 through the first gas supply pipe 16. It exchanges heat with the exhaust gas in the second heat exchange device 4 to make the CO2 in the exhaust gas sublimate into dry ice and then flows into the second gas supply pipe 17. It is then transported to the cold side inlet of the first heat exchange device 3 through the second gas supply pipe 17. It exchanges heat with the exhaust gas in the first heat exchange device 3 to condense and liquefy the gas components in the exhaust gas with boiling points higher than the boiling point of CO2 and then flows into the third gas supply pipe 18. It then flows into the second control valve 10 through the third gas supply pipe 18. The second control valve 10 delivers an appropriate amount of LNG to the dual-fuel main engine through the fourth gas supply pipe 19 for combustion to drive the ship, according to the combustion requirements of the dual-fuel main engine of the LNG ship. The remaining excess LNG is returned to the upper part of the cargo tank 7 through the fifth gas supply pipe 20, forming a closed loop of fuel supply for the dual-fuel main engine.

[0043] After excess LNG is returned to the upper part of the cargo tank 7 through the fifth gas supply pipe 20, the temperature inside the cargo tank 7 is regulated by the cryogenic equipment or spray equipment on the LNG ship.

[0044] Preferably, the first control valve 9 is provided with a bypass pipe 21, which is connected to the first valve port of the second control valve 10. When LNG flows out from the cold side outlet of the second heat exchange device 4 and into the second gas supply pipe 17, if the gas components in the condensate liquefaction tail gas of the first heat exchange device 3 with boiling points higher than CO2 do not require so much LNG, an appropriate amount of LNG can be delivered to the cold side inlet of the first heat exchange device 3 by controlling the valve opening of the first control valve 9. The remaining excess LNG flows into the second control valve 10 from the bypass pipe 21.

[0045] The exhaust gas discharged from the main unit 1 is exchanged with the low-temperature LNG in the first heat exchange device 3 and the second heat exchange device 4 in sequence, and then discharged into the atmosphere from the end of the carbon recovery condensation pipeline 12. The temperature of the exhaust gas flowing into the first heat exchange device 3 is higher than the temperature of the exhaust gas flowing into the second heat exchange device 4, and the temperature of the LNG flowing into the first heat exchange device 3 is higher than the temperature of the LNG flowing into the second heat exchange device 4.

[0046] The carbon recovery condensation pipeline 12 is equipped with a first temperature sensor for detecting the exhaust gas temperature T1 before entering the first heat exchanger 3, a second temperature sensor for detecting the exhaust gas temperature T2 discharged from the first heat exchanger 3, and a third temperature sensor for detecting the exhaust gas temperature T3 discharged from the second heat exchanger 4. The first temperature sensor is located on the pipeline upstream of the first heat exchanger 3, the second temperature sensor is located on the pipeline between the first heat exchanger 3 and the second heat exchanger 4 (i.e., installed on the pipeline downstream of the first heat exchanger 3), and the third temperature sensor is located on the pipeline downstream of the second heat exchanger 4.

[0047] Since the boiling point of CO2 is -78.5℃, in order to ensure that CO2 is fully sublimated and to reduce the amount of LNG used, the temperature T3 of the exhaust gas discharged from the second heat exchange device 4 is controlled between -90℃ and -100℃, which is lower than the boiling point of CO2. In order to obtain relatively pure dry ice, the temperature T2 of the exhaust gas discharged from the first heat exchange device 3 is controlled between -60℃ and -70℃, which is higher than and close to the boiling point of CO2, so that all gas components in the exhaust gas with boiling points higher than the boiling point of CO2 can be condensed and liquefied and separated from the exhaust gas.

[0048] This invention also provides a control method for a main engine exhaust carbon collection system, specifically including the following steps:

[0049] S1, the LNG in the liquid cargo tank 7 is supplied to the main engine 1 for combustion through the main engine gas supply system;

[0050] S2, after the main unit 1 discharges high-temperature exhaust gas, the high-temperature exhaust gas enters the carbon recovery condensation pipe 12 from the main unit exhaust pipe 13, and first enters the first heat exchange device 3. The high-temperature exhaust gas and low-temperature LNG exchange heat in the first heat exchange device 3 to remove all gas components in the exhaust gas with boiling points higher than CO2 boiling points that can be completely condensed and liquefied (such as a large amount of water vapor condensing into ice), so as to separate these gas components from the exhaust gas. The high-temperature exhaust gas becomes a higher-temperature exhaust gas (between -60℃ and -70℃). At this time, the LNG that exchanges heat with the high-temperature exhaust gas in the first heat exchange device 3 is the LNG that has undergone the initial heat exchange in the second heat exchange device 4 and has been heated to a higher temperature (but this temperature is still much lower than the temperature of the high-temperature exhaust gas).

[0051] Then, the higher-temperature exhaust gas discharged from the first heat exchange device 3 enters the second heat exchange device 4. At this time, CO2 accounts for a large proportion of the higher-temperature exhaust gas. In the second heat exchange device 4, the higher-temperature exhaust gas (between -60℃ and -70℃) exchanges heat with LNG at -163℃. The exhaust gas temperature drops to below the boiling point of CO2, -78.5℃. CO2 sublimates into dry ice and is separated from the low-temperature exhaust gas. The remaining gas is discharged from the end of the carbon recovery condensation pipe 12.

[0052] During the process of gas condensation and CO2 sublimation into dry ice, the controller 6 collects the operating signal L1 of the main engine 1 in real time, including the load, and controls the valve opening of the second control valve 10 according to the combustion requirements of the dual-fuel main engine of the LNG ship. The controller 6 delivers an appropriate amount of LNG to the dual-fuel main engine through the fourth gas supply pipe 19 for combustion to drive the ship.

[0053] Meanwhile, the first temperature sensor detects the exhaust gas temperature T1 before it enters the first heat exchange device 3 in real time, and transmits the detected temperature T1 to the controller 6. The controller 6 uses temperature T1 and temperature T2 to determine whether the inlet and outlet temperatures of the first heat exchange device 3 meet the requirements.

[0054] The second temperature sensor detects the exhaust gas temperature T2 discharged from the first heat exchange device 3 in real time and transmits the detected temperature T2 to the controller 6. The controller controls the valve opening of the first control valve 9 to control the exhaust gas temperature T2 between -60℃ and 70℃.

[0055] The third temperature sensor detects the exhaust gas temperature T3 discharged from the second heat exchange device 4 in real time and transmits the detected temperature T3 to the controller 6. The controller 6 controls the cryogenic pump 8 to control the exhaust gas temperature T3 between -90℃ and -100℃.

[0056] In this embodiment, the first heat exchange device 3 is a de-icing cooler 3, which may be composed of multiple heat exchangers. The second heat exchange device is a decarbonizing cooler 4, and the second control valve 10 is a three-way valve.

[0057] Example 2: The main unit exhaust carbon collection system given in this example is basically the same as that in Example 1. The specific difference is that the end of the main unit exhaust pipe 13 is also connected to a proportional distributor 2. The first outlet of the proportional distributor is connected to the inlet of the carbon recovery condensation pipe 12, and the second outlet is connected to the exhaust branch pipe 14. The outlet of the exhaust branch pipe 14 merges into the end of the carbon recovery condensation pipe 12. The proportional distributor is used to distribute the high-temperature exhaust gas discharged from the main unit 1 so that part of the exhaust gas flows into the carbon recovery condensation pipe 12 and the other part of the exhaust gas flows into the exhaust branch pipe 14.

[0058] A fourth temperature sensor is installed at the end of the carbon recovery condensation pipe 12. The fourth temperature sensor is used to detect the exhaust gas temperature T4 that is finally emitted into the atmosphere.

[0059] The fourth temperature sensor transmits the detected final exhaust gas temperature T4 to the controller 6. The controller 6 controls the valve opening of the proportional distributor 2 to proportionally distribute the high-temperature exhaust gas discharged from the main unit 1 to the carbon recovery condenser pipe 12 and the exhaust branch pipe 14. The high-temperature exhaust gas flowing into the carbon recovery condenser pipe 12 becomes low-temperature exhaust gas after two heat exchange treatments of gas condensation and CO2 sublimation into dry ice. It mixes with the high-temperature exhaust gas in the exhaust branch pipe 14 before being discharged into the atmosphere. This ensures that the temperature of the mixed exhaust gas discharged into the atmosphere is higher than the freezing point, preventing water vapor from the high-temperature exhaust gas from freezing at the end of the pipe and preventing water vapor in the air from freezing at the end of the pipe.

[0060] Preferably, to prevent icing at the end of the carbon recovery condensation pipe 12, the final exhaust gas temperature T4 released into the atmosphere should be at least 25°C higher than normal temperature, and the minimum T4 should not be lower than 0°C.

[0061] This embodiment also provides a control method for a main engine exhaust carbon collection system, which specifically includes the following steps:

[0062] S1, the LNG in the liquid cargo tank 7 is supplied to the main engine 1 for combustion through the main engine gas supply system;

[0063] S2, after the main unit 1 discharges high-temperature exhaust gas, the high-temperature exhaust gas enters the carbon recovery condensation pipe 12 from the main unit exhaust pipe 13, and first enters the first heat exchange device 3. The high-temperature exhaust gas and low-temperature LNG exchange heat in the first heat exchange device 3 to remove all gas components in the exhaust gas with boiling points higher than CO2 boiling points that can be completely condensed and liquefied (such as a large amount of water vapor condensing into ice), so as to separate these gas components from the exhaust gas. The high-temperature exhaust gas becomes a higher-temperature exhaust gas (between -60℃ and -70℃). At this time, the LNG that exchanges heat with the high-temperature exhaust gas in the first heat exchange device 3 is the LNG that has undergone the initial heat exchange in the second heat exchange device 4 and has been heated to a higher temperature (but this temperature is still much lower than the temperature of the high-temperature exhaust gas).

[0064] Then, the higher-temperature exhaust gas discharged from the first heat exchange device 3 enters the second heat exchange device 4. At this time, CO2 accounts for a large proportion of the higher-temperature exhaust gas. In the second heat exchange device 4, the higher-temperature exhaust gas (between -60℃ and -70℃) exchanges heat with LNG at -163℃. The exhaust gas temperature drops to below the boiling point of CO2, -78.5℃. CO2 sublimates into dry ice and is separated from the low-temperature exhaust gas. The remaining gas is discharged from the end of the carbon recovery condensation pipe 12.

[0065] During the process of gas condensation and CO2 sublimation into dry ice, the controller 6 collects the operating signal L1 of the main engine 1 in real time, including the load, and controls the valve opening of the second control valve 10 according to the combustion requirements of the dual-fuel main engine of the LNG ship. The controller 6 delivers an appropriate amount of LNG to the dual-fuel main engine through the fourth gas supply pipe 19 for combustion to drive the ship.

[0066] Meanwhile, the first temperature sensor detects the exhaust gas temperature T1 before it enters the first heat exchange device 3 in real time, and transmits the detected temperature T1 to the controller 6. The controller 6 uses temperature T1 and temperature T2 to determine whether the inlet and outlet temperatures of the first heat exchange device 3 meet the requirements.

[0067] The second temperature sensor detects the exhaust gas temperature T2 discharged from the first heat exchange device 3 in real time and transmits the detected temperature T2 to the controller 6. The controller controls the valve opening of the first control valve 9 to control the exhaust gas temperature T2 between -60℃ and -70℃.

[0068] The third temperature sensor detects the exhaust gas temperature T3 of the second heat exchange device 4 in real time and transmits the detected temperature T3 to the controller 6. The controller 6 controls the cryogenic pump 8 to control the exhaust gas temperature T3 between -90℃ and -100℃.

[0069] The fourth temperature sensor detects the final exhaust gas temperature T4 released into the atmosphere in real time and transmits the detected temperature T4 to the controller 6. The controller 6 controls the valve opening of the proportional distributor 2 to adjust the exhaust gas distribution ratio in the carbon recovery condensation pipe 12 and the exhaust branch pipe 14 so that the final exhaust gas temperature T4 released into the atmosphere is greater than the ambient temperature by 25°C and the minimum limit of T4 is not lower than 0°C.

[0070] Other specific implementation methods are the same as in Example 1, and will not be described in detail here.

[0071] Example 3: The main exhaust carbon collection system given in this example is basically the same as that in Example 2. The specific difference is that a mixer 11 is added on the basis of Example 2.

[0072] The outlet of the exhaust branch pipe 14 is connected to the first inlet of the mixer 11, the outlet of the carbon recovery condensation pipe 12 is connected to the second inlet of the mixer 11, and the outlet of the mixer 11 is connected to the exhaust pipe 15.

[0073] A fourth temperature sensor is installed at the end of the exhaust pipe 15 to detect the final exhaust gas temperature T4 that is emitted into the atmosphere.

[0074] The fourth temperature sensor transmits the detected final exhaust gas temperature T4 to the controller 6. The controller 6 controls the valve opening of the proportional distributor 2 to proportionally distribute the high-temperature exhaust gas discharged from the main unit 1 to the carbon recovery condenser pipe 12 and the exhaust branch pipe 14. The high-temperature exhaust gas flowing into the carbon recovery condenser pipe 12 becomes low-temperature exhaust gas after two heat exchange treatments of gas condensation and CO2 sublimation into dry ice. It is then mixed with the high-temperature exhaust gas in the exhaust branch pipe 14 in the mixer 11 and then discharged into the atmosphere through the exhaust gas discharge pipe 15. This ensures that the temperature of the mixed exhaust gas discharged into the atmosphere is higher than the freezing point, preventing water vapor from the high-temperature exhaust gas from freezing at the end of the pipe and preventing water vapor in the air from freezing at the end of the pipe.

[0075] Preferably, to prevent icing at the end of the carbon recovery condensation pipe 12, the final exhaust gas temperature T4 released into the atmosphere should be at least 25°C higher than normal temperature, and the minimum T4 should not be lower than 0°C.

[0076] The mixer 11 is a pipeline fluid mixer that enables two or more fluids to be fully mixed in a very short time or within a pipeline length. The high-temperature exhaust gas flowing through the exhaust branch pipe 14 and the low-temperature exhaust gas flowing through the carbon recovery condensation pipe 12 are fully mixed by the mixer 11, so that the mixed exhaust gas is above the freezing point, preventing water vapor from the high-temperature exhaust gas from freezing in the exhaust pipe and preventing water vapor in the air from freezing at the end of the exhaust main pipe.

[0077] Other specific implementation methods of the main unit exhaust carbon collection system are the same as those in Examples 1 and 2, and will not be described in detail here.

[0078] The control method of the main unit exhaust carbon collection system in this embodiment is basically the same as that in Embodiment 2, and will not be described in detail here.

[0079] Example 4: The carbon collection system for the main engine exhaust gas given in this example is basically the same as that in Example 1, 2 or 3. The specific difference is that a fan 5 is added on the basis of Example 1, 2 or 3.

[0080] like Figure 4 As shown, the fan 5 is installed in the carbon recovery condensation pipeline 12, and the fan 5 is located downstream of the second heat exchange device 4.

[0081] Due to the influence of multiple heat exchangers and pipelines on the exhaust gas emitted by the main unit 1, a large amount of pressure loss is generated in the low-temperature exhaust gas flowing out from the second heat exchange device 3. In order to ensure that the low-temperature exhaust gas can flow smoothly to the end of the carbon recovery condenser pipeline 12, a power fan is added to the carbon recovery condenser pipeline 12. The low-temperature exhaust gas passes through the power fan and continues to flow to the end of the pipeline for direct discharge, or is discharged after mixing with the high-temperature exhaust gas in the exhaust branch pipe 14, or is discharged after mixing with the high-temperature exhaust gas in the exhaust branch pipe 14 in the mixer 11.

[0082] Other specific implementation methods of the main unit exhaust carbon collection system are the same as those in Embodiment 1, 2 or 3, and will not be described in detail here.

[0083] This embodiment also provides a control method for a main engine exhaust carbon collection system, which specifically includes the following steps:

[0084] The LNG in the liquid cargo tank 7 is supplied to the main engine 1 for combustion through the main engine gas supply system;

[0085] Part of the exhaust gas emitted by the main unit 1 during combustion flows into the carbon recovery and condensation pipe 12, and the other part flows into the exhaust branch pipe 14;

[0086] The high-temperature exhaust gas flowing into the carbon recovery condenser pipe 12 first passes through the first heat exchange device 3, where it exchanges heat with LNG to condense and liquefy the gas components in the exhaust gas with boiling points higher than CO2. Then it passes through the second heat exchange device 4, where it exchanges heat with LNG again to sublimate the CO2 in the exhaust gas into dry ice. Finally, the exhaust gas discharged from the second heat exchange device 4 is pressurized by the fan 5 of the carbon recovery condenser pipe 12 and flows into the mixer 11. In the mixer 11, it mixes with the high-temperature exhaust gas in the exhaust branch pipe 14 and is then discharged to the outside atmosphere from the exhaust gas discharge pipe 14.

[0087] During carbon recovery, the fourth temperature sensor detects the final exhaust gas temperature T4 released into the atmosphere in real time to control the valve opening of the proportional distributor 2 to adjust the exhaust gas distribution ratio flowing into the carbon recovery condenser pipe 12 and the exhaust branch pipe 14. The second temperature sensor detects the exhaust gas temperature T2 discharged from the first heat exchange device 3 in real time to control the valve opening of the first control valve 9 to keep the exhaust gas temperature T2 between -60℃ and -70℃. The third temperature sensor detects the exhaust gas temperature T3 discharged from the second heat exchange device 4 in real time to control the cryogenic pump 8 to keep the exhaust gas temperature T3 between -90℃ and -100℃.

[0088] The present invention also provides a dual-fuel LNG carrier that uses the method described in the above embodiments to collect CO2 from the exhaust gas of the dual-fuel main engine.

[0089] The present invention also provides a dual-fuel LNG carrier equipped with the main engine exhaust carbon collection system described in the above embodiments.

[0090] It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A carbon collection system for main engine exhaust gas, characterized in that, It includes a first heat exchange device (3) and a second heat exchange device (4). The cold-side inlet and outlet of the first heat exchange device (3) and the second heat exchange device (4) are both connected to the gas supply pipeline of the main unit gas supply system, and the hot-side inlet and outlet are both connected to the carbon recovery condensation pipeline (12). The LNG drawn from the cargo tank (7) by the main engine gas supply system first passes through the second heat exchange device (4), then through the first heat exchange device (3), and finally enters the main engine (1) for combustion. The carbon recovery condenser pipe (12) is connected to the main exhaust pipe (13) so that the high-temperature exhaust gas discharged from the main unit first passes through the first heat exchange device (3), and exchanges heat with LNG in the first heat exchange device (3) to condense the gas components in the exhaust gas with boiling points higher than CO2 boiling points. Then it passes through the second heat exchange device (4), and exchanges heat with LNG again in the second heat exchange device (4) to make the CO2 in the exhaust gas sublimate into dry ice. Finally, it is discharged to the outside atmosphere through the carbon recovery condenser pipe (12). The end of the main exhaust pipe (13) is also connected to a proportional distributor (2). The first outlet of the proportional distributor (2) is connected to the inlet of the carbon recovery condenser pipe (12), and the second outlet is connected to an exhaust branch pipe (14). The outlet of the exhaust branch pipe (14) flows into the end of the carbon recovery condenser pipe (12). The proportional distributor is used to distribute the high-temperature exhaust gas discharged by the main unit (1) so that a part of the exhaust gas flows into the carbon recovery condenser pipe (12) and another part of the exhaust gas flows into the exhaust branch pipe (14). It also includes a mixer (11), the outlet of the exhaust branch pipe (14) is connected to the first inlet of the mixer (11), the outlet of the carbon recovery condensation pipe (12) is connected to the second inlet of the mixer (11), and the outlet of the mixer (11) is connected to the exhaust gas discharge pipe (15).

2. The main engine exhaust carbon collection system according to claim 1, characterized in that, The carbon recovery condensation pipeline (12) is equipped with a first temperature sensor for detecting the exhaust gas temperature T1 before entering the first heat exchange device (3), a second temperature sensor for detecting the exhaust gas temperature T2 discharged from the first heat exchange device (3), and a third temperature sensor for detecting the exhaust gas temperature T3 discharged from the second heat exchange device (4). A fourth temperature sensor is installed on the exhaust pipe (15) to detect the exhaust gas temperature T4 that is finally emitted into the atmosphere. The first, second, third and fourth temperature sensors are all electrically connected to the controller (6).

3. The main engine exhaust carbon collection system according to claim 2, characterized in that, The exhaust gas temperature T2 discharged by the first heat exchange device (3) is controlled between -60℃ and -70℃, and the exhaust gas temperature T3 discharged by the second heat exchange device (4) is controlled between -90℃ and -100℃.

4. The main engine exhaust carbon collection system according to claim 1, characterized in that, The main gas supply system includes a cryogenic pump (8), a first gas supply pipe (16), a second gas supply pipe (17), a third gas supply pipe (18), a fourth gas supply pipe (19), a fifth gas supply pipe (20), a first control valve (9), and a second control valve (10). The cryogenic pump (8) is installed on the first gas supply pipe (16). One end of the first gas supply pipe (16) extends to the lower part of the liquid cargo tank (7) and the other end is connected to the cold side inlet of the second heat exchange device (4). One end of the second gas supply pipe (17) is connected to the cold side outlet of the second heat exchange device (4) and the other end is connected to the cold side inlet of the first heat exchange device (3). The first control valve (9) is installed on the second gas supply pipe (17). One end of the third gas supply pipe (18) is connected to the cold side outlet of the first heat exchange device (3) and the other end is connected to the first valve port of the second control valve (10). The second valve port of the second control valve (10) is connected to the fuel inlet of the main engine (1) through the fourth gas supply pipe (19). The third valve port of the second control valve (10) is connected to the fifth gas supply pipe (20). The end of the fifth gas supply pipe (20) extends to the upper part of the LNG liquid cargo tank (7).

5. The main engine exhaust carbon collection system according to claim 4, characterized in that, The first control valve (9) is provided with a bypass pipe (21), which is connected to the first valve port of the second control valve (10).

6. The main engine exhaust carbon collection system according to claim 1, characterized in that, A fan (5) is also installed on the carbon recovery condensation pipeline (12), and the fan (5) is located downstream of the second heat exchange device (4).

7. A control method for a main engine exhaust carbon collection system according to any one of claims 1-6, characterized in that, Specifically, the following steps are included: The LNG in the liquid cargo tank (7) is supplied to the main engine (1) for combustion through the main engine gas supply system; Part of the exhaust gas emitted by the main unit (1) during combustion flows into the carbon recovery condenser pipe (12), and the other part flows into the exhaust branch pipe (14). The high-temperature exhaust gas flowing into the carbon recovery condenser pipe (12) first passes through the first heat exchange device (3), where it exchanges heat with LNG to condense and liquefy the gas components in the exhaust gas with boiling points higher than CO2. Then it passes through the second heat exchange device (4), where it exchanges heat with LNG again to sublimate the CO2 in the exhaust gas into dry ice. Finally, the exhaust gas discharged from the second heat exchange device (4) flows into the mixer (11) through the carbon recovery condenser pipe (12), where it mixes with the high-temperature exhaust gas in the exhaust branch pipe (14) and is then discharged to the outside atmosphere from the exhaust gas discharge pipe (15). During carbon recovery, the fourth temperature sensor detects the final exhaust gas temperature T4 released into the atmosphere in real time to control the valve opening of the proportional distributor (2) to adjust the exhaust gas distribution ratio in the carbon recovery condenser pipe (12) and the exhaust branch pipe (14). The second temperature sensor detects the exhaust gas temperature T2 discharged from the first heat exchange device (3) in real time to control the valve opening of the first control valve (9) to control the exhaust gas temperature T2 between -60℃ and -70℃. The third temperature sensor detects the exhaust gas temperature T3 discharged from the second heat exchange device (4) in real time to control the cryogenic pump (8) to control the exhaust gas temperature T3 between -90℃ and -100℃.

8. A dual-fuel LNG carrier, characterized in that, CO2 in the exhaust gas from a dual-fuel main engine is collected using the method described in claim 7.

9. A dual-fuel LNG carrier, characterized in that, Includes the main engine exhaust carbon collection system according to any one of claims 1-6.

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