Main engine tail gas carbon collection system, control method thereof and dual-fuel LNG ship

Abstract

The invention discloses a main engine tail gas carbon collection system, a control method thereof and a dual-fuel LNG ship, a carbon recovery pipeline is arranged on a main engine exhaust pipeline, the carbon recovery pipeline and a fuel gas supply system of a ship main engine are fused, and CO2 in main engine tail gas is recovered in a physical phase change mode, so that the purity of prepared dry ice can be guaranteed, and the carbon recovery efficiency is improved. CO2 in the main engine tail gas discharged into the atmosphere can be effectively removed, and direct emission of CO2 is reduced.

Description

Technical Field

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

[0002] In recent years, green development has become the theme song of the shipping industry, and carbon neutrality and zero-carbon goals have attracted the attention of industry insiders. As the cleanest energy, hydrogen energy, although it meets the requirements of future development, has high manufacturing costs and its safety technology is not mature enough, which makes hydrogen energy still not the mainstream energy source at present. At present, the mainstream energy of ships is still fuel oil and new LNG. This energy contains a large amount of carbon elements. After the main engine is burned, a large amount of carbon oxides such as CO2 will be produced, which will aggravate the greenhouse effect. There are desulfurization and denitrification technologies for the treatment of ship main engine exhaust, but there is no carbon treatment or collection technology. Therefore, it is necessary to design a ship main engine exhaust carbon collection system. Summary of the invention

[0003] In view of this, the present invention provides an engine exhaust carbon collection system and a control method thereof, and a dual-fuel LNG ship, which are used to collect CO2 in the engine exhaust gas of the dual-fuel LNG ship.

[0004] A main engine tail gas carbon collection system comprises a first heat exchange device and a second heat exchange device, wherein 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 of the first heat exchange device and the second heat exchange device are both connected to the carbon recovery condensation pipeline.

[0005] The LNG drawn from the liquid cargo tank by the main engine gas supply system 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 condensation pipeline is connected to the main engine exhaust pipe so that the high-temperature exhaust gas discharged from the main engine first passes through the first heat exchange device, performs heat exchange with LNG in the first heat exchange device to condense and liquefy the gas components in the exhaust gas with a boiling point higher than the boiling point of CO2, then passes through the second heat exchange device, performs heat exchange with LNG again in the second heat exchange device to condense the CO2 in the exhaust gas into dry ice, and finally is discharged to the outside atmosphere through the carbon recovery condensation pipeline.

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

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

[0009] Preferably, the carbon recovery condensation pipeline is provided with 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.

[0010] The exhaust pipe is provided with a fourth temperature sensor for detecting the exhaust temperature T4 finally discharged into the atmosphere. 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 between -60°C and -70°C, and the temperature T3 of the exhaust gas discharged from the second heat exchange device is controlled between -90°C and -100°C.

[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] A 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 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 arranged 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 liquid cargo tank.

[0014] Preferably, a bypass pipe is provided 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 also provided on the carbon recovery condensation pipeline, and the fan is arranged downstream of the second heat exchange device.

[0016] A control method for a main engine tail gas carbon collection system comprises the following steps:

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

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

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

[0020] During the carbon recovery process, the fourth temperature sensor detects the exhaust gas temperature T4 finally discharged into the atmosphere in real time to control the valve opening of the proportional diverter to adjust the exhaust gas distribution ratio flowing to the carbon recovery condensation pipeline 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 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 in real time to control the low-temperature pump to control the exhaust gas temperature T3 between -90℃ and -100℃.

[0021] A dual-fuel LNG ship uses the method to collect CO2 in the exhaust gas emitted by the dual-fuel main engine.

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

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

[0024] 1. The present invention arranges a carbon recovery pipeline on the main engine exhaust pipeline, integrates the carbon recovery pipeline with the gas supply system of the ship's main engine, and utilizes physical phase change to achieve the recovery of CO2 in the main engine exhaust gas, thereby ensuring the purity of dry ice preparation, effectively removing CO2 in the main engine exhaust gas discharged into the atmosphere, and reducing direct CO2 emissions.

[0025] 2. The present invention can realize automatic control of tail gas CO2 collection by setting the temperature of each key point and adjusting the program according to a specific design.

[0026] 3. The present invention arranges a proportional diverter at the outlet of the main engine exhaust pipe to distribute the high-temperature exhaust gas discharged from the main engine to the carbon recovery condensation pipeline and the exhaust branch pipe in proportion. Part of the high-temperature exhaust gas flowing into the carbon recovery condensation pipeline is converted into low-temperature exhaust gas after two heat exchange treatments of gas condensation and CO2 sublimation into dry ice, and is mixed with the high-temperature exhaust gas in the exhaust branch pipe before being discharged into the atmosphere. In this way, the temperature of the mixed exhaust gas discharged into the atmosphere can be made higher than the freezing point, thereby preventing the water vapor from the high-temperature exhaust gas from freezing at the end of the pipeline and preventing the water vapor in the air from freezing when it encounters cold at the end of the pipeline. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 It is a structural schematic diagram of the main engine tail gas carbon collection system in Example 1.

[0029] Figure 2 It is a structural schematic diagram of the main engine tail gas carbon collection system in Example 2.

[0030] Figure 3 It is a structural schematic diagram of the main engine tail gas carbon collection system in Example 3.

[0031] Figure 4 It is a structural schematic diagram of the main engine tail gas carbon collection system in Example 4.

[0032] The meanings of the numbers in the figure are:

[0033] 1 is the main engine, 2 is the proportional diverter, 3 is the first heat exchange device, 4 is the second heat exchange device, 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 condensation pipeline, 13 is the main engine exhaust pipe, 14 is the exhaust branch pipe, 15 is the exhaust gas exhaust 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 engine operation signal. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is described below by the specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

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

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

[0037] In order to better understand the technical solution of the present invention, the present invention is described in detail below with reference to the accompanying drawings.

[0038] In embodiment 1, the present invention provides a main engine exhaust carbon collection system, comprising a first heat exchange device 3 and a second heat exchange device 4, wherein 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 passes 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 arranged 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 end inlet of the second heat exchange device 4, one end of the second 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 gas supply pipe 17, one end of the third 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 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 liquid cargo tank 7.

[0041] The carbon recovery condensation pipeline 12 is connected to the main engine exhaust pipe 13 so that the high-temperature exhaust gas discharged from the main engine first passes through the first heat exchange device 3, performs heat exchange with 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 the boiling point of CO2, then passes through the second heat exchange device 4, performs heat exchange with LNG again in the second heat exchange device 4 to condense the CO2 in the exhaust gas into dry ice, and finally is discharged to the outside atmosphere through the carbon recovery condensation pipeline 12.

[0042] The liquid cargo tank 7 is the cargo tank of the LNG ship, which stores low-temperature liquid LNG at -163°C. The low-temperature pump 8 extracts the LNG and transports it to the cold side inlet of the second heat exchange device 4 through the first gas supply pipe 16, performs heat exchange with the exhaust gas in the second heat exchange device 4 to condense CO2 in the exhaust gas into dry ice, and then flows into the second gas supply pipe 17, and is transported to the cold side inlet of the first heat exchange device 3 through the second gas supply pipe 17, performs heat exchange with the exhaust gas in the first heat exchange device 3 to condense and liquefy the gas components in the exhaust gas with a boiling point higher than the boiling point of CO2, and then flows into the third gas supply pipe 18, and then flows into the second control valve 10 through the third gas supply pipe 18. The second control valve 10 transports an appropriate amount of LNG to the dual-fuel main engine through the fourth gas supply pipe 19 for combustion 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 gas supply pipe 20, forming a closed-loop cycle of the fuel supply of the dual-fuel main engine.

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

[0044] Preferably, a bypass pipe 21 is provided on the first control valve 9, and the bypass pipe 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 flows into the second gas supply pipe 17, if the gas component with a boiling point higher than the boiling point of CO2 in the condensed and liquefied tail gas of the first heat exchange device 3 does not need so much LNG, the valve opening of the first control valve 9 can be controlled to transport an appropriate amount of LNG to the cold side inlet of the first heat exchange device 3, and the remaining excess LNG flows into the second control valve 10 from the bypass pipe 21.

[0045] The exhaust gas discharged from the main engine 1 is heat exchanged with the low-temperature LNG in the first heat exchange device 3 and the second heat exchange device 4 in turn, 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 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 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. The first temperature sensor is arranged on the pipeline upstream of the first heat exchange device 3, the second temperature sensor is arranged on the pipeline between the first heat exchange device 3 and the second heat exchange device 4 (that is, installed on the pipeline downstream of the first heat exchange device 3), and the third temperature sensor is arranged on the pipeline downstream of the second heat exchange device 4.

[0047] Since the boiling point of CO2 is -78.5°C, in order to fully condense CO2 and reduce the use of LNG, the temperature T3 of the exhaust gas discharged from the second heat exchange device 4 is controlled between -90°C and -100°C, 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°C and -70°C, which is higher than and close to the boiling point of CO2, so that all gas components in the exhaust gas with a boiling point higher than the boiling point of CO2 can be completely condensed and liquefied and separated from the exhaust gas.

[0048] The present invention also provides a control method for a main engine tail gas carbon collection system, which specifically comprises the following steps:

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

[0050] S2, after the main engine 1 discharges high-temperature tail gas, the high-temperature tail gas enters the carbon recovery condensation pipeline 12 from the main engine exhaust pipe 13, and first enters the first heat exchange device 3, and the high-temperature tail gas and the low-temperature LNG are heat exchanged in the first heat exchange device 3, and all gas components with boiling points higher than the boiling point of CO2 in the tail gas can be condensed and liquefied (such as a large amount of water vapor condenses into ice), so as to separate these gas components from the tail gas, and the high-temperature tail gas becomes a relatively high-temperature tail gas (between -60°C and -70°C). At this time, the LNG heat exchanged with the high-temperature tail gas in the first heat exchange device 3 is the LNG after the temperature has been raised after the initial heat exchange in the second heat exchange device 4 (but the temperature is still much lower than the temperature of the high-temperature tail gas);

[0051] Then, the relatively high temperature tail gas discharged from the first heat exchange device 3 enters the second heat exchange device 4 again. At this time, the proportion of CO2 in the relatively high temperature tail gas is very large. In the second heat exchange device 4, the relatively high temperature tail gas (between -60°C and -70°C) is heat exchanged with the -163°C LNG, and the tail gas temperature is reduced to below the boiling point of CO2 -78.5°C. CO2 is condensed into dry ice and separated from the low temperature tail gas. The remaining gas is discharged from the end of the carbon recovery condensation pipeline 12;

[0052] In the process of gas condensation and CO2 condensation into dry ice, the controller 6 collects the operation signal L1 of the main engine 1 in real time, including the 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 delivers a proper amount of LNG to the dual-fuel main engine through the fourth gas supply pipe 19 in proportion for combustion to drive the ship;

[0053] At the same time, the first temperature sensor detects the exhaust gas temperature T1 before entering the first heat exchange device 3 in real time, and transmits the detected temperature T1 to the controller 6. The controller 6 determines whether the inlet and outlet temperatures of the first heat exchange device 3 meet the requirements based on the temperature T1 and the temperature T2;

[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, and the controller controls the valve opening of the first control valve 9 to control the exhaust gas temperature T2 between -60°C and 70°C;

[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°C and -100°C.

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

[0057] Embodiment 2. The main engine exhaust carbon collection system provided in this embodiment is basically the same as that in Embodiment 1, with the specific difference being that a proportional diverter 2 is also connected to the end of the main engine exhaust pipe 13, a first outlet of the proportional diverter is connected to the inlet of the carbon recovery condensation pipeline 12, and a second outlet is connected to an exhaust branch pipe 14, and an outlet of the exhaust branch pipe 14 merges into the end of the carbon recovery condensation pipeline 12. The proportional diverter is used to distribute the high-temperature exhaust gas discharged from the main engine 1 so that a part of the exhaust gas flows into the carbon recovery condensation pipeline 12 and another part of the exhaust gas flows into the exhaust branch pipe 14.

[0058] A fourth temperature sensor is provided at the end of the carbon recovery condensation pipeline 12 , and the fourth temperature sensor is used to detect the temperature T4 of the exhaust gas finally discharged into the atmosphere.

[0059] The fourth temperature sensor transmits the detected exhaust gas temperature T4 that is finally discharged into the atmosphere to the controller 6. The controller 6 controls the valve opening of the proportional diverter 2 to distribute the high-temperature exhaust gas discharged from the main engine 1 to the carbon recovery condensation pipeline 12 and the exhaust branch pipe 14 in proportion. Part of the high-temperature exhaust gas flowing into the carbon recovery condensation pipeline 12 is converted into low-temperature exhaust gas after two heat exchange treatments of gas condensation and CO2 sublimation into dry ice. It is mixed with the high-temperature exhaust gas in the exhaust branch pipe 14 and then discharged into the atmosphere. In this way, the temperature of the mixed exhaust gas discharged into the atmosphere can be made higher than the freezing point, thereby preventing the water vapor from the high-temperature exhaust gas from freezing at the end of the pipeline and preventing the water vapor in the air from freezing when it encounters cold at the end of the pipeline.

[0060] Preferably, in order to prevent the end of the carbon recovery condensation pipeline 12 from freezing, the exhaust gas temperature T4 finally discharged into the atmosphere should be greater than the normal temperature of 25°C, and the minimum lower limit of T4 should not be lower than 0°C.

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

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

[0063] S2, after the main engine 1 discharges high-temperature tail gas, the high-temperature tail gas enters the carbon recovery condensation pipeline 12 from the main engine exhaust pipe 13, and first enters the first heat exchange device 3, and the high-temperature tail gas and the low-temperature LNG are heat exchanged in the first heat exchange device 3, and all gas components with boiling points higher than the boiling point of CO2 in the tail gas can be condensed and liquefied (such as a large amount of water vapor condenses into ice), so as to separate these gas components from the tail gas, and the high-temperature tail gas becomes a relatively high-temperature tail gas (between -60°C and -70°C). At this time, the LNG heat exchanged with the high-temperature tail gas in the first heat exchange device 3 is the LNG after the temperature has been raised after the initial heat exchange in the second heat exchange device 4 (but the temperature is still much lower than the temperature of the high-temperature tail gas);

[0064] Then, the relatively high temperature tail gas discharged from the first heat exchange device 3 enters the second heat exchange device 4 again. At this time, the proportion of CO2 in the relatively high temperature tail gas is very large. In the second heat exchange device 4, the relatively high temperature tail gas (between -60°C and -70°C) is heat exchanged with the -163°C LNG, and the tail gas temperature is reduced to below the boiling point of CO2 -78.5°C. CO2 is condensed into dry ice and separated from the low temperature tail gas. The remaining gas is discharged from the end of the carbon recovery condensation pipeline 12;

[0065] In the process of gas condensation and CO2 condensation into dry ice, the controller 6 collects the operation signal L1 of the main engine 1 in real time, including the 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 delivers a proper amount of LNG to the dual-fuel main engine through the fourth gas supply pipe 19 in proportion for combustion to drive the ship;

[0066] At the same time, the first temperature sensor detects the exhaust gas temperature T1 before entering the first heat exchange device 3 in real time, and transmits the detected temperature T1 to the controller 6. The controller 6 determines whether the inlet and outlet temperatures of the first heat exchange device 3 meet the requirements based on the temperature T1 and the temperature T2;

[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, and the controller controls the valve opening of the first control valve 9 to control the exhaust gas temperature T2 between -60°C and -70°C;

[0068] 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, and the controller 6 controls the cryogenic pump 8 to control the exhaust gas temperature T3 between -90°C and -100°C;

[0069] The fourth temperature sensor detects the exhaust gas temperature T4 finally discharged 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 diverter 2 to adjust the exhaust gas distribution ratio flowing to the carbon recovery condensation pipeline 12 and the exhaust branch pipe 14 so that the exhaust gas temperature T4 finally discharged into the atmosphere is greater than the normal temperature of 25°C, and the lowest lower limit of T4 is not lower than 0°C.

[0070] Other specific implementations are the same as those in the first embodiment and will not be described in detail here.

[0071] Embodiment 3: The main engine tail gas carbon collection system provided in this embodiment is basically the same as that in Embodiment 2, and the specific difference is that a mixer 11 is added on the basis of Embodiment 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 pipeline 12 is connected to the second inlet of the mixer 11 , and the outlet of the mixer 11 is connected to the exhaust gas exhaust pipe 15 .

[0073] A fourth temperature sensor is disposed at the end of the exhaust gas exhaust pipe 15 , and the fourth temperature sensor is used to detect the temperature T4 of the exhaust gas finally discharged into the atmosphere.

[0074] The fourth temperature sensor transmits the detected exhaust gas temperature T4 that is finally discharged into the atmosphere to the controller 6. The controller 6 controls the valve opening of the proportional diverter 2 to distribute the high-temperature exhaust gas discharged from the main engine 1 to the carbon recovery condensation pipeline 12 and the exhaust branch pipe 14 in proportion. Part of the high-temperature exhaust gas flowing into the carbon recovery condensation pipeline 12 is converted into low-temperature exhaust gas after two heat exchange treatments of gas condensation and CO2 sublimation into dry ice. It is 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 exhaust pipe 15. In this way, the temperature of the mixed exhaust gas discharged into the atmosphere can be made higher than the freezing point, thereby preventing the water vapor from the high-temperature exhaust gas from freezing at the end of the pipeline and preventing the water vapor in the air from freezing when it encounters cold at the end of the pipeline.

[0075] Preferably, in order to prevent the end of the carbon recovery condensation pipeline 12 from freezing, the exhaust gas temperature T4 finally discharged into the atmosphere should be greater than the normal temperature of 25°C, and the minimum lower limit of T4 should not be lower than 0°C.

[0076] 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 exhaust gas flowing through the exhaust branch pipe 14 and the low-temperature exhaust gas flowing through the carbon recovery condensation pipeline 12 are fully mixed through the mixer 11, so that the mixed exhaust gas is above the freezing point, preventing the water vapor from the high-temperature exhaust 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.

[0077] Other specific implementations of the main engine exhaust carbon collection system are the same as those in Embodiments 1 and 2 and will not be described in detail here.

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

[0079] Embodiment 4: The main engine tail gas carbon collection system provided in this embodiment is basically the same as that of Embodiment 1, 2 or 3, and the specific difference is that a fan 5 is added on the basis of Embodiment 1, 2 or 3.

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

[0081] Since the exhaust gas discharged from the main engine 1 passes through multiple heat exchangers and pipelines, the low-temperature exhaust gas flowing out from the second heat exchange device 3 generates a large amount of pressure loss. In order to allow the low-temperature exhaust gas to flow smoothly to the end of the carbon recovery condensation pipeline 12, a power fan is added to the carbon recovery condensation pipeline 12. The low-temperature exhaust gas passes through the power fan and continues to flow to the end of the pipeline 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.

[0082] Other specific implementations of the main engine 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 the host exhaust carbon collection system, which specifically includes the following steps:

[0084] The LNG in the 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 engine 1 during combustion and work flows into the carbon recovery condensation pipeline 12, and the other part flows into the exhaust branch pipe 14;

[0086] The high-temperature tail gas flowing into the carbon recovery condensation pipeline 12 first passes through the first heat exchange device 3, and performs heat exchange with LNG in the first heat exchange device 3 to condense and liquefy the gas components in the tail gas with a boiling point higher than that of CO2, and then passes through the second heat exchange device 4, and performs heat exchange with LNG again in the second heat exchange device 4 to condense CO2 in the tail gas into dry ice. Finally, the tail gas discharged from the second heat exchange device 4 is pressurized by the fan 5 of the carbon recovery condensation pipeline 12 and then flows into the mixer 11, where it is mixed with the high-temperature tail gas in the exhaust branch pipe 14, and then discharged to the outside atmosphere from the tail gas exhaust pipe 14;

[0087] During the carbon recovery process, the fourth temperature sensor detects the exhaust gas temperature T4 finally discharged into the atmosphere in real time to control the valve opening of the proportional diverter 2 to adjust the exhaust gas distribution ratio flowing to the carbon recovery condensation 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 between -60°C and -70°C. 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 between -90°C and -100°C.

[0088] The present invention 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.

[0089] The present invention also provides a dual-fuel LNG ship, on which the main engine tail gas carbon collection system described in the above embodiment is provided.

[0090] It should be clear that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A main engine tail gas carbon collection system, characterized in that: The invention comprises a first heat exchange device (3) and a second heat exchange device (4), wherein 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). 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 passes through the first heat exchange device (3), and finally enters the main engine (1) for combustion. The carbon recovery condensation pipeline (12) is connected to the main engine exhaust pipe (13) so that the high-temperature exhaust gas discharged from the main engine first passes through the first heat exchange device (3), performs heat exchange with 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 the boiling point of CO2, then passes through the second heat exchange device (4), performs heat exchange with LNG again in the second heat exchange device (4) to condense CO2 in the exhaust gas into dry ice, and finally is discharged to the outside atmosphere through the carbon recovery condensation pipeline (12).

2. The main engine tail gas carbon collection system according to claim 1, characterized in that: The end of the main engine exhaust pipe (13) is also connected to a proportional diverter (2), a first outlet of the proportional diverter (2) is connected to the inlet of the carbon recovery condensation pipeline (12), and a second outlet is connected to an exhaust branch pipe (14), and the outlet of the exhaust branch pipe (14) merges into the end of the carbon recovery condensation pipeline (12). The proportional diverter is used to distribute the high-temperature exhaust gas discharged from the main engine (1) so that a part of the exhaust gas flows into the carbon recovery condensation pipeline (12) and another part of the exhaust gas flows into the exhaust branch pipe (14).

3. The main engine tail gas carbon collection system according to claim 2, characterized in that: It also includes a mixer (11), wherein 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 pipeline (12) is connected to the second inlet of the mixer (11), and the outlet of the mixer (11) is connected to the exhaust gas exhaust pipe (15).

4. The main engine tail gas carbon collection system according to claim 3, characterized in that: The carbon recovery condensation pipeline (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). 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 (15), 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 (6).

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

6. The main engine tail gas carbon collection system according to claim 1 or 3, characterized in that: The main engine gas supply system comprises 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), A cryogenic pump (8) is arranged on a 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); a first control valve (9) is arranged 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 a fourth gas supply pipe (19); the third valve port of the second control valve (10) is connected to a fifth gas supply pipe (20), and the end of the fifth gas supply pipe (20) extends to the upper part of the LNG liquid cargo tank (7).

7. The main engine tail gas carbon collection system according to claim 6, 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).

8. The main engine tail gas carbon collection system according to claim 1, characterized in that: The carbon recovery condensation pipeline (12) is also provided with a fan (5), and the fan (5) is arranged downstream of the second heat exchange device (4).

9. A control method for the main engine tail gas carbon collection system according to any one of claims 1 to 8, characterized in that: The specific steps include: The LNG in the liquid cargo tank (7) is supplied to the main engine (1) through the main engine fuel gas supply system for combustion; Part of the exhaust gas discharged from the main engine (1) during combustion flows into the carbon recovery condensation pipeline (12), and the other part flows into the exhaust branch pipe (14); The high-temperature exhaust gas flowing into the carbon recovery condensation pipeline (12) first passes through the first heat exchange device (3), and then exchanges heat with 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. The high-temperature exhaust gas then passes through the second heat exchange device (4), and then exchanges heat with LNG again in the second heat exchange device (4) to condense 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 condensation pipeline (12), and then 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); During the carbon recovery process, the fourth temperature sensor detects in real time the exhaust gas temperature T4 finally discharged into the atmosphere to control the valve opening of the proportional diverter (2) to adjust the exhaust gas distribution ratio flowing into the carbon recovery condensation pipeline (12) and the exhaust branch pipe (14); the second temperature sensor detects in real time the exhaust gas temperature T2 discharged from the first heat exchange device (3) to control the valve opening of the first control valve (9) to control the exhaust gas temperature T2 between -60°C and -70°C; the third temperature sensor detects in real time the exhaust gas temperature T3 discharged from the second heat exchange device (4) to control the low-temperature pump (8) to control the exhaust gas temperature T3 between -90°C and -100°C.

10. A dual-fuel LNG ship, characterized in that: The method described in claim 9 is used to collect CO2 in the exhaust gas emitted by a dual-fuel main engine.

11. A dual-fuel LNG ship, characterized in that: A main engine tail gas carbon collection system comprising any one of claims 1-8.

Images