System for carbon capture from main-engine exhaust gas, control method for system, and dual-fuel LNG vessel

Abstract

A system for carbon capture from main-engine exhaust gas, a control method for the system, and a dual-fuel LNG vessel. The system comprises a first heat exchange device (3) and a second heat exchange device (4). LNG extracted from a liquid cargo tank (7) by a main-engine fuel gas supply system sequentially passes through the second heat exchange device (4) and the first heat exchange device (3), and finally enters a main engine (1) for combustion; and high-temperature exhaust gas discharged from the main engine sequentially passes through the first heat exchange device (3) and the second heat exchange device (4), and finally passes through carbon recovery condensation piping (12) to be discharged to the outside atmosphere. The present system can reduce the direct emission of CO2, and can ensure the purity of recovered dry ice.

Description

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

[0001] The present application relates to the technical field of shipbuilding, and in particular to a main engine tail gas carbon collection system and control method thereof, and a dual-fuel LNG ship. BACKGROUND

[0002] In recent years, green development has become the theme song of the shipbuilding industry, and carbon neutralization and zero carbon goals have attracted the attention of industry insiders. As the cleanest energy source, hydrogen energy meets the requirements of future development, but its manufacturing cost is high, and the safety technology is not mature enough, which makes hydrogen energy still cannot be used as the mainstream energy at present. The mainstream energy of the current ship is still fuel and new LNG. This kind of energy contains a large amount of carbon elements, and the main engine will produce a large amount of CO2 and other carbon oxides after combustion, which will aggravate the greenhouse effect. There is no carbon treatment or collection technology for the desulfurization and denitrification technology for the treatment of the main engine tail gas of the ship. Therefore, it is necessary to design a main engine tail gas carbon collection system for the ship. SUMMARY

[0003] Therefore, the present application provides a main engine tail gas carbon collection system and control method thereof, and a dual-fuel LNG ship to collect CO2 in the main engine tail gas of the dual-fuel LNG ship.

[0004] A main engine tail gas carbon collection system, comprising 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 connected to the gas supply pipeline of the main engine gas supply system, and the hot side inlet and outlet are connected to the carbon recovery condensing pipeline,

[0005] The LNG extracted from the liquid cargo tank first passes through the second heat exchange device, then passes through the first heat exchange device, and finally enters the main engine for combustion,

[0006] The carbon recovery condensing pipeline is connected to the main engine exhaust pipe to make the high-temperature exhaust gas discharged by the main engine first pass through the first heat exchange device, and then pass through the second heat exchange device to condense and liquefy the gas components with a boiling point higher than that of CO2 in the exhaust gas.

[0007] Preferably, the end of the main engine exhaust pipe is also connected to a proportional flow divider, the first outlet of the proportional flow divider is connected to the inlet of the carbon recovery condensing pipeline, the second outlet is connected to an exhaust branch pipe, the outlet of the exhaust branch pipe is connected to the end of the carbon recovery condensing pipeline, and the proportional flow divider is used to distribute the high-temperature exhaust gas discharged by the main engine to make part of the exhaust gas flow into the carbon recovery condensing pipeline and the other part of the exhaust gas flow into the exhaust branch pipe.

[0008] Preferably, a mixer is further included, the outlet of the exhaust branch pipe is connected to a first inlet of the mixer, the outlet of the carbon recovery condensing pipeline is connected to a second inlet of the mixer, and an exhaust gas discharge pipe is connected to an outlet of the mixer.

[0009] Preferably, a first temperature sensor for detecting the temperature T1 of the exhaust gas before entering the first heat exchange device, a second temperature sensor for detecting the temperature T2 of the exhaust gas discharged from the first heat exchange device, and a third temperature sensor for detecting the temperature T3 of the exhaust gas discharged from the second heat exchange device are arranged on the carbon recovery condensing pipeline,

[0010] A fourth temperature sensor for detecting the temperature T4 of the exhaust gas finally discharged into the atmosphere is arranged on the exhaust gas discharge pipe, and the first temperature sensor, the second temperature sensor, the third temperature sensor, and the fourth temperature sensor are all electrically connected to the controller.

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

[0012] Preferably, the main engine 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] The cryogenic pump is arranged on the first gas supply pipe, one end of the first gas supply pipe extends to the lower part of the liquid cargo tank, and the other end is connected to the cold side end inlet of the second heat exchange device, one end of the second gas supply pipe is connected to the cold side end outlet of the second heat exchange device, and the other end is connected to the cold side end inlet of the first heat exchange device, the first control valve is arranged on the second gas supply pipe, one end of the third gas supply pipe is connected to the cold side end 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 liquid cargo tank.

[0014] Preferably, a bypass pipe is arranged on the first control valve, and the bypass pipe is connected to the first valve port of the second control valve.

[0015] Preferably, a fan is further arranged on the carbon recovery condensing pipeline, and the fan is arranged downstream of the second heat exchange device.

[0016] A control method of a main engine exhaust gas carbon collection system, specifically comprising the following steps:

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

[0018] The tail gas discharged by the main engine combustion does work, part of which flows into the carbon recovery condensing pipeline, and the other part flows into the exhaust branch pipe;

[0019] The high-temperature tail gas flowing into the carbon recovery condensing pipeline first passes through the first heat exchange device, exchanges heat with the LNG in the first heat exchange device to condense the gas components in the liquefied tail gas with a boiling point higher than that of CO2, and then passes through the second heat exchange device, exchanges heat with the LNG again in the second heat exchange device to make the CO2 in the tail gas sublimate into dry ice, and finally the tail gas discharged from the second heat exchange device flows into the mixer through the carbon recovery condensing pipeline, mixes with the high-temperature tail gas in the exhaust branch pipe, and then is discharged to the outside atmosphere through the tail gas discharge pipe;

[0020] In the carbon recovery process, the fourth temperature sensor detects the tail gas temperature T4 discharged to the atmosphere in real time to control the valve opening degree of the proportional flow divider to adjust the distribution ratio of the tail gas flowing into the carbon recovery condensing pipeline and the exhaust branch pipe, the second temperature sensor detects the tail gas temperature T2 discharged from the first heat exchange device in real time to control the valve opening degree of the first control valve to control the tail gas temperature T2 to be between-60℃ and-70℃, and the third temperature sensor detects the tail gas temperature T3 discharged from the second heat exchange device in real time to control the low-temperature pump to control the tail gas temperature T3 to be between-90℃ and-100℃.

[0021] A dual-fuel LNG ship collects CO2 in the tail gas discharged by the dual-fuel main engine by using the method.

[0022] A dual-fuel LNG ship includes the main engine tail gas carbon collection system.

[0023] The beneficial effects of the present application are:

[0024] 1、The present application sets up a carbon recovery pipeline on the main engine exhaust pipeline, and integrates the carbon recovery pipeline with the gas supply system of the ship main engine, realizes the recovery of CO2 in the main engine tail gas by using the physical phase change method, can ensure the purity of dry ice preparation, can effectively remove CO2 in the main engine tail gas discharged to the atmosphere, and reduce the direct discharge of CO2.

[0025] 2、The present application can realize automatic control of CO2 collection in the tail gas through temperature setting at each key point and according to the specific design adjustment program.

[0026] 3、The application sets a proportional flow divider at the outlet of the main engine exhaust pipe, and distributes the high-temperature exhaust gas discharged by the main engine to the carbon recovery condensing pipeline and the exhaust branch pipe in proportion, and the part of the high-temperature exhaust gas flowing into the carbon recovery condensing pipeline becomes low-temperature exhaust gas after twice heat exchange treatment of gas condensation and CO2 desublimation into dry ice, and then is mixed with the high-temperature exhaust gas in the exhaust branch pipe and discharged into the atmosphere, so that the temperature of the mixed exhaust gas discharged into the atmosphere is higher than the freezing point, preventing the water vapor in the high-temperature exhaust gas from freezing at the end of the pipeline, and preventing the water vapor in the air from freezing at the end of the pipeline. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0028] Fig. 1 is a structural schematic diagram of a main engine exhaust gas carbon collection system in embodiment one.

[0029] Fig. 2 is a structural schematic diagram of a main engine exhaust gas carbon collection system in embodiment two.

[0030] Fig. 3 is a structural schematic diagram of a main engine exhaust gas carbon collection system in embodiment three.

[0031] Fig. 4 is a structural schematic diagram of a main engine exhaust gas carbon collection system in embodiment four.

[0032] The meanings of the reference numerals in the drawings are as follows: 1 is a main engine, 2 is a proportional flow divider, 3 is a first heat exchange device, 4 is a second heat exchange device, 5 is a fan, 6 is a controller, 7 is a liquid cargo tank, 8 is a low-temperature pump, 9 is a first control valve, 10 is a second control valve, 11 is a mixer, 12 is a carbon recovery condensing pipeline, 13 is a main engine exhaust pipe, 14 is an exhaust branch pipe, 15 is an exhaust gas discharge pipe, 16 is a first gas supply pipe, 17 is a second gas supply pipe, 18 is a third gas supply pipe, 19 is a fourth gas supply pipe, 20 is a fifth gas supply pipe, 21 is a bypass pipe, T1-T4 are temperature signals, and L1 is a main engine operation signal. DETAILED DESCRIPTION

[0033] In order to make the objects, technical solutions and advantages of the present application more clear, the present application will be described in detail through specific embodiments shown in the drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present application. In addition, in the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present application.

[0034] The terminology used in the present disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used in the present disclosure and the appended claims, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0035] It should be understood that, although the terms first, second, third, etc. can be used herein to describe various information, but these information should not be limited to these terms, and cannot be understood as indicating or implying relative importance. These terms are only used to distinguish one type of information from another type of information. For example, without departing from the scope of the present disclosure, the first information can also be referred to as the second information, and similarly, the second information can also be referred to as the first information. Depending on the context, the word "if" as used herein can be interpreted as "when" or "in response to determining" or "in response to ascertaining".

[0036] In order to better understand the technical solutions of the present application, the present application will be described in detail below in combination with the drawings.

[0037] In the embodiment, the host exhaust gas carbon collection system comprises 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 connected to the gas supply pipeline of the host gas supply system, and the hot side inlet and outlet are connected to the carbon recovery condensing pipeline 12.

[0038] The LNG drawn from the liquid cargo tank 7 is first passed through the second heat exchange device 4, then passed through the first heat exchange device 3, and finally burned in the host 1.

[0039] Specifically, the main engine fuel supply system comprises a cryogenic pump 8, a first fuel supply pipe 16, a second fuel supply pipe 17, a third fuel supply pipe 18, a fourth fuel supply pipe 19, a fifth fuel supply pipe 20, a first control valve 9 and a second control valve 10, the cryogenic pump 8 is arranged on the first fuel supply pipe 16, one end of the first fuel 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 fuel 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 arranged on the second fuel supply pipe 17, one end of the third fuel 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 fuel supply pipe 19, the third valve port of the second control valve 10 is connected with the fifth fuel supply pipe 20, and the end of the fifth fuel supply pipe 20 extends to the upper part of the LNG liquid cargo tank 7.

[0040] The carbon recovery condensing pipe 12 is connected with the main engine exhaust pipe 13 to make the high-temperature exhaust gas discharged from the main engine first pass through the first heat exchange device 3, exchange heat with the LNG in the first heat exchange device 3 to condense the gas components with boiling points higher than the boiling point of CO2 in the liquefied exhaust gas, then pass through the second heat exchange device 4, and exchange heat with the LNG in the second heat exchange device 4 again to make the CO2 in the exhaust gas sublimate into dry ice, and finally be discharged to the outside atmosphere through the carbon recovery condensing pipe 12.

[0041] The liquid cargo tank 7 is the cargo tank of the LNG ship, which stores the low-temperature liquid LNG at -163℃ inside, the cryogenic pump 8 pumps out the LNG and delivers it to the cold side inlet of the second heat exchange device 4 through the first fuel supply pipe 16, 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 fuel supply pipe 17, exchanges heat with the exhaust gas in the first heat exchange device 3 to condense the gas components with boiling points higher than the boiling point of CO2 in the liquefied exhaust gas, and then flows into the third fuel supply pipe 18, and then flows into the second control valve 10 through the third fuel supply pipe 18, the second control valve 10 proportionally delivers the appropriate amount of LNG to the dual-fuel main engine through the fourth fuel supply pipe 19 according to the combustion demand of the dual-fuel main engine of the LNG ship to drive the ship, and the remaining excess LNG is returned to the upper part of the liquid cargo tank 7 through the fifth fuel supply pipe 20 to form a closed loop cycle of the dual-fuel main engine fuel supply.

[0042] After the excess LNG is returned to the upper part of the liquid cargo tank 7 through the fifth fuel supply pipe 20, the temperature inside the liquid cargo tank 7 is adjusted by the cryogenic equipment or the spraying equipment on the LNG ship.

[0043] Preferably, the first control valve 9 is provided with a bypass pipe 21, which is connected with the first valve port of the second control valve 10. When the LNG flows from the cold side end outlet of the second heat exchange device 4 into the second gas supply pipe 17, if the gas components with boiling points higher than that of CO2 in the liquefied exhaust gas condensed by the first heat exchange device 3 do not need so much LNG, the first control valve 9 can be controlled to deliver appropriate amount of LNG to the cold side end inlet of the first heat exchange device 3, and the remaining LNG flows into the second control valve 10 through the bypass pipe 21.

[0044] The exhaust gas discharged from the main engine 1 is sequentially subjected to heat exchange with the low-temperature LNG in the first heat exchange device 3 and the second heat exchange device 4, and then discharged into the atmosphere from the end of the carbon recovery condensing pipe 12. The temperature of the exhaust gas flowing into the first heat exchange device 3 is higher than that 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 that of the LNG flowing into the second heat exchange device 4.

[0045] The carbon recovery condensing pipe 12 is provided with a first temperature sensor for detecting the temperature T1 of the exhaust gas before entering the first heat exchange device 3, a second temperature sensor for detecting the temperature T2 of the exhaust gas discharged from the first heat exchange device 3, and a third temperature sensor for detecting the temperature T3 of the exhaust gas discharged from the second heat exchange device 4. The first temperature sensor is arranged on the pipe upstream of the first heat exchange device 3, the second temperature sensor is arranged on the pipe between the first heat exchange device 3 and the second heat exchange device 4 (i.e. arranged on the pipe downstream of the first heat exchange device 3), and the third temperature sensor is arranged on the pipe downstream of the second heat exchange device 4.

[0046] Since the boiling point of CO2 is -78.5℃, in order to make the CO2 fully sublimate and reduce the amount of LNG used, the temperature T3 of the exhaust gas discharged from the second heat exchange device 4 is controlled to be 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 to be between -60℃ and -70℃, which is higher than and close to the boiling point of CO2, so that all the gas components with boiling points higher than that of CO2 in the exhaust gas can be completely condensed and liquefied and separated from the exhaust gas.

[0047] The application also provides a control method of the main engine exhaust gas carbon collection system, which specifically comprises the following steps:

[0048] 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;

[0049] S2, when the host 1 exhaust high temperature, high temperature exhaust from the host exhaust pipe 13 into the carbon recovery condensing pipeline 12, and first into the first heat exchange device 3, high temperature exhaust and low temperature LNG in the first heat exchange device 3 heat exchange, remove all the gas components in the exhaust gas whose boiling point is higher than the boiling point of CO2 can be fully condensed (such as a large amount of water vapor condensation into ice), in order to separate these gas components from the exhaust gas, high temperature exhaust into higher temperature exhaust (-60℃-70℃ between), at this time in the first heat exchange device 3 with high temperature exhaust heat exchange LNG is in the second heat exchange device 4 has been carried out the initial heat exchange of temperature increased LNG (but the temperature is still far below the temperature of high temperature exhaust) ;

[0050] Then, from the first heat exchange device 3 discharged higher temperature exhaust into the second heat exchange device 4, at this time the proportion of CO2 in the higher temperature exhaust is very large, in the second heat exchange device 4, higher temperature exhaust (-60℃-70℃ between) and -163℃ LNG heat exchange, exhaust temperature is reduced to the boiling point of CO2-78.5℃ below, CO2 sublimate into dry ice, separated from the low temperature exhaust, the remaining gas from the end of the carbon recovery condensing pipeline 12 exhaust;

[0051] In the above process of gas condensation and CO2 sublimate into dry ice, the controller 6 real-time acquisition host 1 running signal L1, including load, according to the combustion demand of LNG ship dual fuel host control second control valve 10 valve opening, according to the proportion of appropriate amount of LNG through the fourth gas supply pipe 19 to the dual fuel host for combustion, in order to drive the ship;

[0052] At the same time, the first temperature sensor real-time detection exhaust temperature T1 before entering the first heat exchange device 3, and the detected temperature T1 is transmitted to the controller 6, the controller 6 by temperature T1 and temperature T2 to determine whether the first heat exchange device 3 import and export temperature meet the requirements;

[0053] The second temperature sensor real-time detection exhaust temperature T2 discharged from the first heat exchange device 3, and the detected temperature T2 is transmitted to the controller 6, the controller control first control valve 9 valve opening to control the exhaust temperature T2-60℃-70℃ between;

[0054] The third temperature sensor real-time detection exhaust temperature T3 discharged from the second heat exchange device 4, and the detected temperature T3 is transmitted to the controller 6, the controller 6 control low temperature pump 8 to control the exhaust temperature T3-90℃-100℃ between.

[0055] In the embodiment, the first heat exchange device 3 is the ice cooler 3, the first heat exchange device 3 can be composed of a plurality of heat exchangers, the second heat exchange device is the carbon cooler 4, and the second control valve 10 is a three way valve.

[0056] In the second embodiment, the host engine exhaust gas carbon collection system is basically the same as that in the first embodiment, but the difference is that the end of the host engine exhaust pipe 13 is also connected with a proportional flow divider 2, the first outlet of the proportional flow divider is connected with the inlet of the carbon recovery condensing pipeline 12, the second outlet is connected with an exhaust branch pipe 14, the outlet of the exhaust branch pipe 14 is merged into the end of the carbon recovery condensing pipeline 12, and the proportional flow divider is used to distribute the high-temperature exhaust gas discharged from the host engine 1 so that part of the exhaust gas flows into the carbon recovery condensing pipeline 12 and the other part of the exhaust gas flows into the exhaust branch pipe 14.

[0057] The end of the carbon recovery condensing pipeline 12 is provided with a fourth temperature sensor, which is used to detect the temperature T4 of the exhaust gas finally discharged into the atmosphere.

[0058] The fourth temperature sensor transmits the detected temperature T4 of the exhaust gas finally discharged into the atmosphere to the controller 6, and the controller 6 controls the valve opening degree of the proportional flow divider 2 to proportionally distribute the high-temperature exhaust gas discharged from the host engine 1 to the carbon recovery condensing pipeline 12 and the exhaust branch pipe 14. The part of the high-temperature exhaust gas flowing into the carbon recovery condensing pipeline 12 is changed into low-temperature exhaust gas after two heat exchange treatments of gas condensation and CO2 desublimation into dry ice, and is mixed with the high-temperature exhaust gas in the exhaust branch pipe 14 before being discharged into the atmosphere. In this way, the temperature of the mixed exhaust gas discharged into the atmosphere is higher than the freezing point, which prevents the water vapor in the high-temperature exhaust gas from icing at the end of the pipeline, and prevents the water vapor in the air from icing at the end of the pipeline.

[0059] Preferably, to prevent the end of the carbon recovery condensing pipeline 12 from icing, the temperature T4 of the exhaust gas finally discharged into the atmosphere is best greater than the normal temperature 25℃, and the minimum lower limit of T4 is not less than 0℃.

[0060] The second embodiment also provides a control method of the host engine exhaust gas carbon collection system, which specifically includes the following steps:

[0061] S1, the LNG in the liquid cargo tank 7 is supplied to the host engine 1 for combustion through the host engine gas supply system;

[0062] S2, after the host engine 1 discharges high-temperature exhaust gas, the high-temperature exhaust gas enters the carbon recovery condensing pipeline 12 from the host engine exhaust pipe 13 and first enters the first heat exchange device 3. The high-temperature exhaust gas is heat-exchanged with the low-temperature LNG in the first heat exchange device 3, all the gas components in the exhaust gas with a boiling point higher than the boiling point of CO2 can be completely condensed and liquefied (such as a large amount of water vapor condensed into ice) to separate these gas components from the exhaust gas, and the high-temperature exhaust gas is changed into higher-temperature exhaust gas (between -60℃ and -70℃). At this time, the LNG heat-exchanged with the high-temperature exhaust gas in the first heat exchange device 3 is the LNG with a temperature increased after the first heat exchange in the second heat exchange device 4 (but the temperature is still much lower than the temperature of the high-temperature exhaust gas).

[0063] Then, the higher temperature tail gas discharged from the first heat exchange device 3 enters the second heat exchange device 4, at this time, the proportion of CO2 in the higher temperature tail gas is very large, in the second heat exchange device 4, the higher temperature tail gas (-60℃ to -70℃) exchanges heat with LNG at -163℃, the temperature of the tail gas is reduced to below the boiling point of CO2 (-78.5℃), and the CO2 sublimates into dry ice, which is separated from the low temperature tail gas, and the remaining gas is discharged from the end of the carbon recovery condensing pipeline 12;

[0064] In the process of gas condensation and CO2 sublimation into dry ice, the controller 6 collects the running signals L1 of the main engine 1 in real time, including load, etc., controls the valve opening of the second control valve 10 according to the combustion demand of the LNG ship dual-fuel main engine, and proportionally sends an appropriate amount of LNG to the dual-fuel main engine through the fourth gas supply pipeline 19 for combustion to drive the ship;

[0065] At the same time, the first temperature sensor detects the temperature T1 of the tail gas before entering the first heat exchange device 3 in real time, and transmits the detected temperature T1 to the controller 6, and the controller 6 judges whether the inlet and outlet temperatures of the first heat exchange device 3 meet the requirements through the temperatures T1 and T2;

[0066] The second temperature sensor detects the temperature T2 of the tail gas discharged from the first heat exchange device 3 in real time, and transmits the detected temperature T2 to the controller 6, and the controller controls the valve opening of the first control valve 9 to control the temperature T2 of the tail gas to be between -60℃ and -70℃;

[0067] The third temperature sensor detects the temperature T3 of the tail gas discharged from the second heat exchange device 4 in real time, and transmits the detected temperature T3 to the controller 6, and the controller 6 controls the low temperature pump 8 to control the temperature T3 of the tail gas to be between -90℃ and -100℃;

[0068] The fourth temperature sensor detects the temperature T4 of the tail gas finally discharged into the atmosphere in real time, and transmits the detected temperature T4 to the controller 6, and the controller 6 controls the valve opening of the proportional flow divider 2 to adjust the distribution ratio of the tail gas flowing into the carbon recovery condensing pipeline 12 and the exhaust branch pipe 14, so that the temperature T4 of the tail gas finally discharged into the atmosphere is greater than the normal temperature 25℃, and the minimum lower limit of T4 is not less than 0℃.

[0069] Other specific embodiments and examples are the same as example one, and will not be described in detail here.

[0070] In example three, the main engine tail gas carbon collection system is basically the same as that in example two, and the specific difference is that a mixer 11 is added based on example two.

[0071] The outlet of the exhaust branch pipe 14 is connected with the first inlet of the mixer 11, the outlet of the carbon recovery condensing pipeline 12 is connected with the second inlet of the mixer 11, and the outlet of the mixer 11 is connected with the tail gas exhaust pipe 15.

[0072] The tail end of the tail gas exhaust pipe 15 is provided with a fourth temperature sensor for detecting the temperature T4 of the tail gas finally discharged into the atmosphere.

[0073] The fourth temperature sensor transmits the detected temperature T4 of the tail gas finally discharged into the atmosphere to the controller 6, which controls the valve opening of the proportional flow divider 2 to proportionally distribute the high-temperature tail gas discharged from the main engine 1 to the carbon recovery condensing pipeline 12 and the exhaust branch pipe 14. The part of the high-temperature tail gas flowing into the carbon recovery condensing pipeline 12 is changed into low-temperature tail gas after two heat exchange processes of gas condensation and CO2 desublimation into dry ice, and then mixed with the high-temperature tail gas in the exhaust branch pipe 14 in the mixer 11, and then discharged into the atmosphere through the tail gas exhaust pipe 15. In this way, the temperature of the mixed tail gas discharged into the atmosphere is higher than the freezing point, preventing the water vapor in the high-temperature tail gas from freezing at the end of the pipeline, and preventing the water vapor in the air from freezing at the end of the pipeline.

[0074] Preferably, to prevent the end of the carbon recovery condensing pipeline 12 from freezing, the temperature T4 of the tail gas finally discharged into the atmosphere is preferably greater than the normal temperature of 25℃, and the minimum lower limit of T4 is not less than 0℃.

[0075] The mixer 11 is a pipeline fluid mixer that can fully mix two or more fluids in a very short time or pipeline length. The high-temperature tail gas flowing through the exhaust branch pipe 14 and the low-temperature tail gas flowing through the carbon recovery condensing pipeline 12 are fully mixed by the mixer 11, so that the mixed tail gas is higher than the freezing point, preventing the water vapor in the high-temperature tail gas from freezing in the exhaust pipe, and preventing the water vapor in the air from freezing at the end of the exhaust main pipe.

[0076] The other specific embodiments of the main engine tail gas carbon collection system are the same as those of Embodiments One and Two, and will not be described in detail here.

[0077] The control method of the main engine tail gas carbon collection system in this embodiment is basically the same as that of Embodiment Two, and will not be described in detail here.

[0078] In this embodiment, the main engine tail gas carbon collection system is basically the same as that of Embodiments One or Two or Three, and the specific difference is that a fan 5 is added based on Embodiments One or Two or Three.

[0079] As shown in FIG. 4, the fan 5 is arranged in the carbon recovery condensing pipeline 12, and the fan 5 is arranged downstream of the second heat exchange device 4.

[0080] Due to the influence of the exhaust gas discharged by the main engine 1 flowing through multiple heat exchangers and pipelines, a large amount of pressure loss is generated in the low-temperature exhaust gas flowing out of the second heat exchange device 3. In order to enable the low-temperature exhaust gas to smoothly flow to the pipeline end of the carbon recovery condensing pipeline 12, a power fan is added in the carbon recovery condensing pipeline 12. The low-temperature exhaust gas passes through the power fan and continues to flow to the pipeline end to be directly discharged or mixed with the high-temperature exhaust gas in the exhaust branch pipe 14 and then discharged or mixed with the high-temperature exhaust gas in the exhaust branch pipe 14 in the mixer 11 and then discharged.

[0081] The other specific embodiments of the main engine exhaust gas carbon collection system are the same as those of the first or second or third embodiment, and will not be described in detail here.

[0082] The embodiment also provides a control method of the main engine exhaust gas carbon collection system, which specifically comprises the following steps:

[0083] The LNG in the liquid cargo tank 7 is supplied to the main engine 1 for combustion through the main engine gas supply system;

[0084] The exhaust gas discharged by the main engine 1 flows into the carbon recovery condensing pipeline 12 and the exhaust branch pipe 14;

[0085] The high-temperature exhaust gas flowing into the carbon recovery condensing pipeline 12 first passes through the first heat exchange device 3, exchanges heat with the LNG in the first heat exchange device 3 to condense and liquefy the gas components in the exhaust gas with a boiling point higher than that of CO2, and then passes through the second heat exchange device 4 to exchange heat with the LNG again in the second heat exchange device 4 to make the CO2 in the exhaust gas sublimate 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 condensing pipeline 12 and flows into the mixer 11, where it is mixed with the high-temperature exhaust gas in the exhaust branch pipe 14, and then discharged to the outside atmosphere through the exhaust gas discharge pipe 14;

[0086] In the carbon recovery process, the fourth temperature sensor detects the temperature T4 of the exhaust gas finally discharged to the atmosphere in real time to control the valve opening degree of the proportional flow divider 2 to adjust the distribution ratio of the exhaust gas flowing into the carbon recovery condensing pipeline 12 and the exhaust branch pipe 14. The second temperature sensor detects the temperature T2 of the exhaust gas discharged from the first heat exchange device 3 in real time to control the valve opening degree of the first control valve 9 to control the temperature T2 of the exhaust gas to be between -60℃ and -70℃. The third temperature sensor detects the temperature T3 of the exhaust gas discharged from the second heat exchange device 4 in real time to control the low-temperature pump 8 to control the temperature T3 of the exhaust gas to be between -90℃ and -100℃.

[0087] The application also provides a dual-fuel LNG ship, which collects CO2 in the exhaust gas discharged by the dual-fuel main engine by using the method described in the above embodiment.

[0088] The application also provides a dual-fuel LNG ship, wherein the ship is provided with the main engine tail gas carbon collection system described in the above embodiments.

[0089] It should be noted that the embodiments described are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

Claims

1. A host tail gas carbon collection system characterized by, The first heat exchange device (3) and the second heat exchange device (4) are connected to the gas supply pipeline of the main engine gas supply system at the cold side and connected to the carbon recovery condensing pipeline (12) at the hot side, The LNG extracted from the liquid cargo tank (7) is first passed through the second heat exchange device (4), then passed through the first heat exchange device (3), and finally burned in the main engine (1). The carbon recovery condensing pipeline (12) is connected to the main engine exhaust pipe (13) to make the high-temperature exhaust gas discharged by the main engine first pass through the first heat exchange device (3), exchange heat with the LNG in the first heat exchange device (3) to condense and liquefy the gas components in the exhaust gas with a boiling point higher than that of CO2, then pass through the second heat exchange device (4) to exchange heat with the LNG again to make the CO2 in the exhaust gas sublimate into dry ice, and finally be discharged to the outside atmosphere through the carbon recovery condensing pipeline (12).

2. The host tail gas carbon capture system of claim 1, wherein, The end of the main engine exhaust pipe (13) is also connected to a proportional flow divider (2), the first outlet of the proportional flow divider (2) is connected to the inlet of the carbon recovery condensing pipeline (12), and the second outlet is connected to an exhaust branch pipe (14), the outlet of the exhaust branch pipe (14) is connected to the end of the carbon recovery condensing pipeline (12), and the proportional flow divider is used to distribute the high-temperature exhaust gas discharged by the main engine (1) to make part of the exhaust gas flow into the carbon recovery condensing pipeline (12) and the other part flow into the exhaust branch pipe (14).

3. The host tail gas carbon capture system of claim 2, wherein, 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 condensing pipeline (12) is connected to the second inlet of the mixer (11), and the outlet of the mixer (11) is connected to an exhaust gas discharge pipe (15).

4. The host tail gas carbon capture system of claim 3, wherein, The carbon recovery condensing pipeline (12) is provided 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 by the first heat exchange device (3), and a third temperature sensor for detecting the exhaust gas temperature T3 discharged by the second heat exchange device (4), The exhaust gas discharge pipe (15) is provided with a fourth temperature sensor for detecting the exhaust gas temperature T4 finally discharged to the atmosphere, and the first, second, third and fourth temperature sensors are electrically connected to the controller (6).

5. The host tail gas carbon capture system of claim 4, wherein, 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℃.

6. The host tail gas carbon capture system of claim 1 or 3, wherein, The main engine gas supply system includes a low-temperature 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 low temperature pump (8) is arranged on the first fuel gas supply pipe (16), one end of the first fuel 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 end inlet of the second heat exchange device (4), one end of the second fuel gas supply pipe (17) is connected to the cold side end outlet of the second heat exchange device (4), and the other end is connected to the cold side end inlet of the first heat exchange device (3), the first control valve (9) is arranged on the second fuel gas supply pipe (17), one end of the third fuel gas supply pipe (18) is connected to the cold side end 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 fuel gas supply pipe (19), the third valve port of the second control valve (10) is connected with the fifth fuel gas supply pipe (20), and the tail end of the fifth fuel gas supply pipe (20) extends to the upper part of the LNG liquid cargo tank (7).

7. The host tail gas carbon capture system of claim 6, wherein, The first control valve (9) is provided with a bypass pipe (21) connected to the first valve port of the second control valve (10).

8. The host tail gas carbon capture system of claim 1, wherein, The carbon recovery condensing pipeline (12) is also provided with a fan (5) arranged downstream of the second heat exchange device (4).

9. A control method of a host tail gas carbon capture system according to any one of claims 1 to 8, characterized by, Specifically comprising the following steps: The LNG in the liquid cargo tank (7) is supplied to the main engine (1) for combustion through the main engine fuel gas supply system; The exhaust gas discharged by the main engine (1) after combustion and work flows into the carbon recovery condensing pipeline (12) and the exhaust branch pipe (14); The high-temperature exhaust gas flowing into the carbon recovery condensing pipeline (12) first passes through the first heat exchange device (3), exchanges heat with the LNG in the first heat exchange device (3) to condense the gas components with a boiling point higher than that of CO2 in the liquefied exhaust gas, then passes through the second heat exchange device (4), and exchanges heat with the LNG again in the second heat exchange device (4) to make the CO2 in the exhaust gas sublimate into dry ice, and finally the exhaust gas discharged from the second heat exchange device (4) flows into the mixer (11) through the carbon recovery condensing pipeline (12), mixes with the high-temperature exhaust gas in the exhaust branch pipe (14) in the mixer (11), and then is discharged to the outside atmosphere from the exhaust gas discharge pipe (14); In the carbon recovery process, the fourth temperature sensor detects the exhaust gas temperature T4 discharged to the atmosphere in real time to control the valve opening of the proportional flow divider (2) to adjust the distribution ratio of the exhaust gas flowing into the carbon recovery condensing pipeline (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 to be between-60℃ and-70℃, and the third temperature sensor detects the exhaust gas temperature T3 discharged from the second heat exchange device (4) in real time to control the low temperature pump (8) to control the exhaust gas temperature T3 to be between-90℃ and-100℃.

10. A dual fuel LNG carrier, characterized in that Collecting CO2 in the exhaust gas of the dual-fuel main engine by the method of claim 9.

11. A dual fuel LNG carrier, characterized in that The main engine exhaust gas carbon collection system of any one of claims 1-8. The low temperature pump (8) is arranged on the first fuel gas supply pipe (16), one end of the first fuel 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 end inlet of the second heat exchange device (4), one end of the second fuel gas supply pipe (17) is connected to the cold side end outlet of the second heat exchange device (4), and the other end is connected to the cold side end inlet of the first heat exchange device (3), the first control valve (9) is arranged on the second fuel gas supply pipe (17), one end of the third fuel gas supply pipe (18) is connected to the cold side end 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 fuel gas supply pipe (19), the third valve port of the second control valve (10) is connected with the fifth fuel gas supply pipe (20), and the tail end of the fifth fuel gas supply pipe (20) extends to the upper part of the LNG liquid cargo tank (7). The first control valve (9) is provided with a bypass pipe (21) connected to the first valve port of the second control valve (10). The carbon recovery condensing pipeline (12) is also provided with a fan (5) arranged downstream of the second heat exchange device (4). Specifically comprising the following steps: The LNG in the liquid cargo tank (7) is supplied to the main engine (1) for combustion through the main engine fuel gas supply system; The exhaust gas discharged by the main engine (1) after combustion and work flows into the carbon recovery condensing pipeline (12) and the exhaust branch pipe (14); The high-temperature exhaust gas flowing into the carbon recovery condensing pipeline (12) first passes through the first heat exchange device (3), exchanges heat with the LNG in the first heat exchange device (3) to condense the gas components with a boiling point higher than that of CO2 in the liquefied exhaust gas, then passes through the second heat exchange device (4), and exchanges heat with the LNG again in the second heat exchange device (4) to make the CO2 in the exhaust gas sublimate into dry ice, and finally the exhaust gas discharged from the second heat exchange device (4) flows into the mixer (11) through the carbon recovery condensing pipeline (12), mixes with the high-temperature exhaust gas in the exhaust branch pipe (14) in the mixer (11), and then is discharged to the outside atmosphere from the exhaust gas discharge pipe (14); In the carbon recovery process, the fourth temperature sensor detects the exhaust gas temperature T4 discharged to the atmosphere in real time to control the valve opening of the proportional flow divider (2) to adjust the distribution ratio of the exhaust gas flowing into the carbon recovery condensing pipeline (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 to be between-60℃ and-70℃, and the third temperature sensor detects the exhaust gas temperature T3 discharged from the second heat exchange device (4) in real time to control the low temperature pump (8) to control the exhaust gas temperature T3 to be between-90℃ and-100℃. Collecting CO2 in the exhaust gas of the dual-fuel main engine by the method of claim 9. The main engine exhaust gas carbon collection system of any one of claims 1-8.

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