Internal combustion engine
The three-stage exhaust gas cooling system in large marine engines uses LNG's cold energy to efficiently separate and store CO2, addressing CO2 emission reduction challenges while managing cold energy, thus reducing engine complexity and energy consumption.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- ヴィンゲーデー リミテッド
- Filing Date
- 2024-06-20
- Publication Date
- 2026-07-23
AI Technical Summary
Existing internal combustion engines, particularly large marine engines, face challenges in reducing CO2 emissions effectively while managing surplus cold energy from liquefied natural gas (LNG) without increasing complexity or energy consumption.
An internal combustion engine with a three-stage exhaust gas cooling system utilizing the cold energy of LNG to freeze-separate CO2, comprising a first stage using seawater, a second stage cooling to -100°C, and a third stage cooling to -106°C for CO2 separation, followed by decarbonized exhaust gas recirculation and storage.
Achieves significant reduction in CO2 emissions by freezing and separating CO2 from exhaust gases using only LNG's cold energy, reducing engine complexity and energy consumption, with flexible decarbonization rates and compact system design.
Smart Images
Figure 2026524600000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to an internal combustion engine having at least one cylinder, preferably a large marine engine having at least one cylinder with an inner diameter of at least 200 mm, and a method for operating the internal combustion engine.
[0002] The present invention relates to the technical field of combustion engines and the reduction of their emissions.
[0003] The present invention preferably relates to an internal combustion engine such as a large marine or ship engine, or a stationary engine having a cylinder with an inner diameter of at least 200 mm. The engine is preferably a two-stroke engine or a two-stroke cross-head engine. The engine can be a gas engine, a dual-fuel engine or a multi-fuel engine. The fuel can be a gas such as liquefied natural gas (LNG) or liquefied petroleum gas (LPG).
[0004] In particular, the present invention relates to a combustion engine using LNG as fuel.
Background Art
[0005] In such an engine, combustion of liquid and / or gaseous fuel is possible, and either self-ignition or forced ignition is possible.
[0006] The internal combustion engine can be a longitudinally scavenged two-stroke engine.
[0007] The engine speed is preferably less than 800 RPM, especially in the case of a four-stroke engine, more preferably less than 200 RPM, especially in the case of a two-stroke engine, which indicates the classification of a low-speed engine.
[0008] Large ships, especially cargo ships, are usually driven by internal combustion engines.
[0009] Exhaust gases from the combustion process must be purified to comply with existing regulations such as IMO Tier III.
[0010] The International Maritime Organization's (IMO) sulfur content regulations have prompted shipowners to find new alternative energy sources. Some ships use liquefied natural gas (LNG) as fuel and are called "LNG-powered vessels." LNG's main component is methane. The combustion of methane produces CO2 and water.
[0011] Therefore, LNG as a marine fuel can reduce harmful gases such as sulfide emissions. However, CO2 emissions still exist, and since CO2 is the main greenhouse gas, it has a significant impact on the environment. In 2018, the IMO formulated a preliminary strategy for reducing greenhouse gas emissions. This strategy plans to reduce carbon emissions from the international shipping industry and continue to move towards the goal of zero carbon.
[0012] LNG must be stored at low temperatures and vaporized before being supplied to the ship's main engine for combustion. During regasification, LNG releases 830 kJ / kg of residual cold energy. For example, it is known that CO2 can be liquefied using the cold energy of LNG from CN112833325A, CN217273515U, or CN110513194A, and then converted into dry ice.
[0013] CO2 recovery can not only solve the greenhouse effect caused by the release of excess CO2 into the environment when LNG is burned as fuel for ships, but also solve the problem of surplus cold energy in LNG-powered vessels by utilizing cold energy. Reducing the power consumption of refrigeration equipment in the dry ice process leads to cost reductions and achieves energy savings and emission reductions.
[0014] Known systems often utilize CO2 absorption and separation units, comprising an absorbent liquid, such as a mixture of an ionic liquid and an organic amine / alcohol solution. The separation unit requires additional space and increases the complexity of the engine design.
[0015] Furthermore, cryogenic carbon recovery processes are also known to be used, in which carbon is separated from exhaust gases by controlling the phase change through modulation of temperature and pressure, and in particular, CO2 solidification extraction is used. CO2 solidification extraction usually consumes a very large amount of energy. [Prior art documents] [Patent Documents]
[0016] [Patent Document 1] CN112833325A [Patent Document 2] CN217273515U [Patent Document 3] CN110513194A [Overview of the project] [Problems that the invention aims to solve]
[0017] Therefore, the object of the present invention is to prevent the drawbacks of the prior art and, in particular, to provide an internal combustion engine and a method for operating the engine, thereby achieving a reduction in CO2 emissions with reasonable effort. [Means for solving the problem]
[0018] This objective is achieved by the internal combustion engine and the method of operating the internal combustion engine described in the independent claim.
[0019] The internal combustion engine has at least one cylinder and is preferably an engine for large ships having at least one cylinder with an inner diameter of at least 200 mm. The internal combustion engine preferably comprises an LNG supply system having an LNG tank for accommodating LNG at a temperature below -150°C. The LNG tank may be suitable for accommodating pressurized LNG.
[0020] The internal combustion engine comprises an exhaust gas cooling system having a first cooling stage, a second cooling stage and a third cooling stage for continuously cooling the exhaust gas.
[0021] The first cooling stage may be configured to use water, such as seawater, as a cooling medium and may be configured to cool the exhaust gas to a temperature level corresponding to the temperature of the seawater (typically a temperature below 30°C). The first cooling stage may comprise at least one first-stage heat exchanger having an inlet and an outlet for guiding the water.
[0022] The first-stage heat exchanger may include a shell and tube, may use direct contact cooling, or may use indirect gas / liquid cooling.
[0023] Upstream of the first stage, the exhaust gas flow may be branched so that only a part of the exhaust gas guided from the cylinder to the exhaust gas cooling system.
[0024] The exhaust gas cooling system may comprise further devices upstream of the first cooling stage, such as an emissions reduction system such as SCR, or a waste heat recovery steam generator and / or duct firing alk, which may affect the exhaust gas temperature.
[0025] The exhaust gas cooling system comprises a second cooling stage arranged downstream of the first cooling stage for cooling the exhaust gas. The second cooling stage comprises at least one second-stage heat exchanger. The second cooling stage may be configured to cool the exhaust gas to a temperature below -100°C, preferably in the range of -110°C to -100°C.
[0026] The cooling temperature of the second cooling stage is determined by the onset of condensation (during the transition from the high-temperature side to the low-temperature side), which depends on the CO2 content in the exhaust gas.
[0027] The second-stage heat exchanger may include shell-and-tube components and may use direct contact cooling, or indirect gas / gas cooling or gas / liquid cooling.
[0028] The exhaust gas cooling system includes a third cooling stage located downstream of the second cooling stage for further cooling the exhaust gas. The third cooling stage may be configured to cool the exhaust gas to a temperature below -106°C, preferably in the range of -140°C to -106°C, more preferably in the range of -125°C to -106°C. In the third cooling stage, CO2 is separated by freezing from the exhaust gas, and the frozen CO2 is separated from the remaining exhaust gas.
[0029] The lower temperature limit is related to the CO2 concentration remaining in the residual exhaust gas.
[0030] Residual exhaust gas is the exhaust gas that leaves the third cooling stage, and it has a significantly reduced CO2 concentration compared to the exhaust gas that leaves the cylinder.
[0031] The third cooling stage comprises at least one third-stage heat exchanger having a first outlet for frozen CO2 and a second outlet for residual exhaust gas.
[0032] When an indirect heat exchanger is used, frozen CO2 may be produced in the form of solid ice, and when a direct contact cooler is used, frozen CO2 may be discharged as a slurry.
[0033] In a direct-contact cooler, the exhaust gas can be cooled by direct contact with a cooling fluid, typically a liquid mixture, such as a water-alcohol mixture or a water-glycol mixture, which does not freeze at the temperature of the third cooling stage. As a result, CO2 can be separated in the form of a solvent-based slurry that can be easily pumped and separated outside the heat exchanger. For separation, the slurry can be guided to a cyclone, or pure CO2 can be evaporated and recondensed.
[0034] Alternatively, CO2 can condense on the contact surface of the heat exchanger and be removed mechanically.
[0035] Frozen CO2 can be removed in batch processing; for example, a portion of the heat exchanger may be used for freezing CO2 while other portions are used to clean up the frozen CO2.
[0036] The outlet for frozen CO2 may be configured to discharge the frozen CO2 as a free-flowing / falling slurry and / or may be equipped with mechanical means for transporting the ice, such as a conveyor belt or a screw conveyor.
[0037] The frozen CO2 can be discharged continuously or in batch mode, and condensation and discharge can be performed alternately.
[0038] The third cooling stage is configured to decarbonize the exhaust gas by at least partially, for example, 25% to 30%. Typically, the partially decarbonized residual exhaust gas leaving the third cooling stage still has a certain carbon concentration.
[0039] The third-stage heat exchanger may include shell-and-tube components and may use direct contact cooling, or indirect gas / gas cooling or gas / liquid cooling.
[0040] At least one of the second-stage heat exchangers and / or at least one of the third-stage heat exchangers are configured to use the cold energy of LNG released from the LNG tank.
[0041] In this application, the use of gaseous or liquid cold energy means that a gas or liquid is heated by another gas or another liquid (and that other gas or another liquid is cooled) either directly or indirectly, for example, via a coolant, within the same heat exchanger.
[0042] LNG may be used directly as a cooling medium in the second-stage heat exchanger and / or the third-stage heat exchanger. Alternatively, an intermediate coolant may be used, which is cooled by LNG and then transferred to the second-stage heat exchanger and / or the third-stage heat exchanger.
[0043] The lower the target concentration, the greater the effort required to remove CO2.
[0044] Preferably, only the cold energy of LNG is used to further cool the exhaust gas precooled in the first cooling stage. No additional energy is consumed. By exclusively using only the cold energy of LNG, it is possible to freeze-separate only a portion of the CO2 in the exhaust gas. This method makes it possible to remove a considerable amount of CO2 from the exhaust gas very effectively.
[0045] Upstream of the third cooling stage, it is not necessary to separate CO2 from the exhaust gas. Since CO2 is frozen and separated in the third cooling stage before other components of the exhaust gas freeze, CO2 is automatically separated from the residual exhaust gas in the third cooling stage. The frozen CO2 can then be simply removed from the third cooling stage.
[0046] Based on the relationship between the latent heat of vaporization of LNG and the latent heat of condensation of CO2, theoretically, 1 kg of LNG can freeze and separate 0.86 kg of CO2, which is equivalent to about 30% of the CO2 produced from combustion.
[0047] As described above, the interconnected LNG supply system and exhaust gas cooling system provide an effective system for partial decarbonization.
[0048] Partially decarbonized exhaust gas is a mixture of N2, oxygen, argon, and residual CO2, and has a lower oxygen content than the oxygen content of air.
[0049] The remaining exhaust gas may be discharged into the environment or may be fully or partially recirculated into the engine air intake.
[0050] If necessary, the internal combustion engine may be provided with further stages, and the residual exhaust gas and / or exhaust gas branched upstream of the first cooling stage may be decarbonized, for example, by separating CO2 and / or by further cooling, which involves additional energy consumption, in order to completely decarbonize the exhaust gas.
[0051] The LNG supply system may include a low-temperature heat exchanger, which may be one of at least one third-stage heat exchangers and / or be in thermal contact with at least one of the at least one third-stage heat exchangers via a coolant.
[0052] LNG can be evaporated in a low-temperature heat exchanger. Typically, for storage, the LNG is compressed to a pressure corresponding to the saturation pressure at the coolant temperature, and the coolant temperature is lower than the condensation temperature of CO2, preferably 5°C to 30°C lower, and more preferably 10°C to 20°C lower.
[0053] In a low-temperature heat exchanger, LNG can be heated to its evaporation temperature and evaporated.
[0054] The LNG may be heated and / or evaporated on at least one cooling medium side of at least one third-stage heat exchanger, or on at least one side of at least one third-stage heat exchanger.
[0055] The LNG supply system may include a high-temperature heat exchanger, which is one of at least one second-stage heat exchangers and / or is in thermal contact with at least one of the at least one second-stage heat exchangers via a coolant.
[0056] In a high-temperature heat exchanger, LNG can be heated to a temperature of -40°C to 20°C, thereby allowing it to be supplied to a cylinder, preferably after compression.
[0057] The high-temperature heat exchanger may be positioned downstream of the low-temperature heat exchanger with respect to the flow direction of LNG from the storage tank to the cylinder.
[0058] The high-temperature heat exchanger may be positioned upstream of the low-temperature heat exchanger with respect to the direction of exhaust gas flow from the cylinder.
[0059] The presence of second and third cooling stages in the cooling system, as well as corresponding low-temperature and high-temperature heat exchangers in the LNG supply system, represents a two-stage system for partial decarbonization, allowing for a certain degree of flexibility in setting the decarbonization rate.
[0060] The LNG supply system may include a piping system having branching sections for selectively and directly connecting LNG tanks to low-temperature heat exchangers and / or high-temperature heat exchangers.
[0061] The piping system may include configurable valves. The internal combustion engine may include a control unit for configuring the valves and controlling the amount of LNG guided to the low-temperature heat exchanger and / or high-temperature heat exchanger.
[0062] The upper sublimation point may vary depending on the CO2 concentration and humidity of the exhaust gas. To thermally balance the first and second cooling stages, a portion of the LNG may be bypassed through the low-temperature heat exchanger and directed to the high-temperature heat exchanger. LNG released from the storage tank may be added and mixed with the gaseous LNG released from the low-temperature heat exchanger either upstream of the high-temperature heat exchanger or within the high-temperature heat exchanger.
[0063] The piping system allows setting the amount of cold energy supplied to the low-temperature heat exchanger and / or high-temperature heat exchanger.
[0064] The exhaust gas cooling system may include an exhaust piping system having bypasses for a first cooling stage, a second cooling stage, and / or a third cooling stage. The exhaust piping system may include configurable valves. The internal combustion engine may include a control unit for configuring the valves and controlling the amount of exhaust gas directed to the first cooling stage, the second cooling stage, and / or the third cooling stage, preferably the same control unit as described above. For example, if a storage tank for frozen CO2 is full, measures may be taken to prevent further condensation of CO2.
[0065] The second cooling stage may include at least one further heat exchanger configured to use the cold energy of frozen CO2 or pressurized liquid CO2 released from the third cooling stage.
[0066] Alternatively, at least one second-stage heat exchanger is configured to use the cold energy of LNG and frozen CO2 released from the third cooling stage.
[0067] The frozen CO2 can be heated to a temperature suitable for storage in the second cooling stage.
[0068] The exhaust gas cooling system may include a residual gas piping system that allows residual exhaust gases leaving the third cooling stage to be guided to the second cooling stage, thereby allowing the cooling energy from the residual exhaust gases leaving the third cooling stage to be used in the second cooling stage, in particular, before the residual exhaust gases are released into the environment.
[0069] The residual gas piping system may include at least one pipe for guiding the gas for the third cooling stage to the second cooling stage.
[0070] The residual gas piping system may include a configurable valve. The internal combustion engine may include a control unit for configuring the valve and, preferably, the same control unit as described above, for controlling the amount of residual gas guided to the second cooling stage.
[0071] The second cooling stage may include at least one additional heat exchanger configured to use the thermal energy of the residual exhaust gas released from the third cooling stage.
[0072] Alternatively, at least one second-stage heat exchanger is configured to use the cold energy of the LNG and residual gas released from the third cooling stage.
[0073] The exhaust gas cooling system may include a dehumidifying device. Preferably, at least one dehumidifying device is fluidly positioned between the first and second stages.
[0074] After cooling the exhaust gas in the first cooling stage, the exhaust gas typically consists of saturated vapor and water droplets at a concentration of 30 g / m³. 3 May contain moisture. Moisture should be reduced or removed before the exhaust gas is cooled to below 5°C. The presence of water or vapor in the exhaust gas is undesirable, as moisture can cause icing in the gas path.
[0075] The dehumidifying device may be configured to remove moisture from the exhaust gas discharged from the first stage and located upstream of the second cooling stage, thereby removing moisture before the exhaust gas is cooled to the freezing point of water.
[0076] The dehumidification device may be configured to remove moisture thermally in at least one heat exchanger, for example, by using the cold energy of decarbonized residual exhaust gas and / or gaseous LNG.
[0077] Dehumidification devices may be configured to remove moisture through specific refrigeration cycles for condensation and freeze-separation.
[0078] Dehumidifying devices may be configured to remove moisture by chemically drying exhaust gases.
[0079] The dehumidification device may include a direct-contact cooler equipped with antifreeze.
[0080] An internal combustion engine may be equipped with a branching device to divert exhaust gases away from the exhaust gas cooling system. This branching device may be part of an EGR (exhaust gas recirculation) system.
[0081] The branching device may include a T-connector and a valve, preferably a configurable valve, so that the amount of exhaust gas guided to the exhaust gas cooling system can be set by a control unit, preferably the same control unit as described above.
[0082] The amount of exhaust gas directed to the exhaust gas cooling system can be adjusted to the capacity of the system. For example, since only up to 30% of the total CO2 can be extracted, up to 30% of the total exhaust gas is directed to the exhaust gas cooling system.
[0083] An internal combustion engine may be equipped with an EGR (exhaust gas recirculation) system, which is preferably configured to branch the exhaust gas upstream of the first cooling stage, and more preferably is a low-pressure EGR system.
[0084] An EGR system can be configured to recirculate 0-60%, preferably 35-55%, of the exhaust gas back into the combustion cylinder. While the amount of exhaust gas to be decarbonized may be reduced, the CO2 concentration in the exhaust gas may be increased, thereby further improving the efficiency of the system for partial decarbonization.
[0085] Downstream of the cylinder, there can be three possible flows of exhaust gases. One may be returned to the air intake by EGR, another may be sent to the exhaust gas cooling system, and a third may simply be discharged into the environment.
[0086] An internal combustion engine may be equipped with a cryogenic CO2 storage tank, which is preferably configured to store CO2 released from the third cooling stage at a temperature close to the triple point.
[0087] Cryogenic CO2 storage tanks can be configured to provide pressures from 5.2 bar to 10 bar, as well as temperatures from -56°C to -40°C.
[0088] LNG tanks can be used to store frozen CO2 and / or reliquefied CO2, provided they are certified to be used at pressures up to 10 bar, for example, so-called Type C LNG tanks.
[0089] An LNG tank can release LNG while receiving CO2. An LNG tank may have separate compartments for storing LNG and CO2.
[0090] The exhaust gas cooling system, including the exhaust gas heat exchangers for the second and third cooling stages, is 40 m 3 Less than 30m, preferably 30m 3 It can occupy less than a certain volume.
[0091] Therefore, such an exhaust gas cooling system can be located inside the engine compartment and can be retrofitted to an existing combustion engine.
[0092] This objective can also be achieved by an internal combustion engine having at least one cylinder, preferably a large marine engine having at least one cylinder with a bore of at least 200 mm, preferably a method of operating the internal combustion engine as described above. The internal combustion engine is powered by LNG and includes an LNG tank for storing LNG at a temperature below -150°C.
[0093] This method includes a step of cooling the exhaust gas discharged from the cylinder in a first cooling stage, preferably to a temperature of 20°C to 30°C, and preferably using water, such as seawater, as the cooling medium.
[0094] Subsequently, the exhaust gas is cooled in a second cooling stage, which includes at least one second-stage heat exchanger, to a temperature preferably below -100°C, and more preferably in the range of -110°C to -100°C.
[0095] Subsequently, the exhaust gas is cooled in a third cooling stage comprising at least one third-stage heat exchanger, preferably to a temperature below -106°C, and more preferably in the range of -140°C to -106°C. In the third cooling stage, CO2 is separated from the exhaust gas by freezing, and the frozen CO2 is separated from the residual exhaust gas, where the CO2 concentration in the residual exhaust gas can be reduced by at least 25%, preferably at least 30%.
[0096] The residual exhaust gas may have a CO2 concentration (molar concentration) of less than 8%.
[0097] In the third cooling stage, the exhaust gas can be cooled from an upper limit condensation temperature corresponding to the CO2 temperature at the initial partial pressure to a lower limit condensation temperature. The CO2 capture rate depends on the proportion of exhaust gas guided through the exhaust gas cooling system, the initial CO2 concentration of the exhaust gas as it leaves the cylinder, and the temperature of the third cooling stage.
[0098] At least one of the second-stage heat exchangers and / or at least one of the first-stage heat exchangers utilize the cold energy of LNG released from the LNG tank.
[0099] In the third cooling stage, not all CO2 is frozen and separated; this method uses only the cold energy of LNG, thus consuming only a small amount of energy.
[0100] Preferably, in order to reduce the size of the heat exchanger, only a portion of the exhaust gas may be guided to pass through the exhaust gas cooling system, while the other portion may be recirculated or not be cooled at all.
[0101] The proportion of exhaust gases guided through the exhaust gas cooling system and the size of the exhaust gas cooling system can be adapted to achieve a predetermined residual CO2 concentration.
[0102] The higher the exhaust gas flow rate, the higher the residual CO2 concentration. To further reduce the CO2 in the residual gas, deeper cooling and / or additional cooling may be provided.
[0103] Preferably, the LNG is guided to pass through at least one of at least one second-stage heat exchangers and / or at least one of at least one third-stage heat exchangers. Additionally or alternatively, a coolant may be guided to pass through at least one of at least one second-stage heat exchangers and / or at least one of at least one third-stage heat exchangers, the coolant being in thermal contact with the LNG being discharged from the LNG tank.
[0104] Frozen CO2 released from the third cooling stage may be guided to pass through at least one of the at least one second-stage heat exchangers and / or may come into thermal contact with a coolant guided to pass through at least one of the at least one second-stage heat exchangers.
[0105] Frozen CO2 can be used to pre-cool the exhaust gas in the second cooling stage.
[0106] During this process, the frozen CO2 is prepared for storage and heated to a temperature suitable for storage.
[0107] The frozen CO2 released from the third cooling stage and / or, when used as a coolant, the frozen CO2 released from the second cooling stage can be compressed to a pressure exceeding 5.1 bar, which is the pressure at the triple point.
[0108] Frozen CO2 can be heated and melted, for example, by heat extracted from exhaust gas in a second cooling stage. The resulting liquid CO2 can then be heated to a temperature close to the triple point of -56°C and stored in a cryogenic CO2 storage unit.
[0109] The residual exhaust gases leaving the third cooling stage can be directed to the second cooling stage.
[0110] Therefore, the thermal energy of the residual exhaust gas as it heats up to ambient temperature can be used to pre-cool the exhaust gas in the second cooling stage.
[0111] The exhaust gas can be dehumidified, particularly upstream of the second cooling stage and / or downstream of the first cooling stage.
[0112] At least a portion of the exhaust gas leaving the cylinder may be recirculated, for example, 0-60%, preferably 35-55%, may be recirculated. The recirculated exhaust gas may be diverted upstream of the first cooling stage, and more preferably downstream of the turbocharger turbine.
[0113] In the following, the present invention will be further illustrated with reference to the following drawings. [Brief explanation of the drawing]
[0114] [Figure 1] A schematic diagram of an example of an internal combustion engine is shown. [Modes for carrying out the invention]
[0115] Figure 1 shows a schematic diagram of an example of an internal combustion engine 1.
[0116] The internal combustion engine 1 preferably includes an LNG supply system 10 having an LNG tank 11 for storing LNG, a low-temperature heat exchanger 13, and a high-temperature heat exchanger 12, at a temperature of less than -150°C.
[0117] The internal combustion engine 1 is equipped with an exhaust gas cooling system 20 having a first cooling stage 21, a second cooling stage 22, and a third cooling stage 23.
[0118] The exhaust gases leaving cylinder 2 pass through the turbine 41 of turbocharger 42. Downstream of turbine 41, a portion of the exhaust gases can be recirculated to the air inlet of cylinder 2 by an EGR system 40. The EGR system may be equipped with a cooler.
[0119] Upstream of the first cooling stage 21, the internal combustion engine 1 may be equipped with further devices 43, such as a selective catalytic reduction device, a waste heat recovery steam generator and / or a duct firing device, which typically reduce the temperature of the exhaust gas.
[0120] A portion of the exhaust gas may also be released into the environment without being guided to the exhaust gas cooling system 20 (not shown).
[0121] The rest of the exhaust gas is guided to a first cooling stage 21, which is configured to use water, such as seawater, as a cooling medium.
[0122] Downstream of the first cooling stage 21, the exhaust gas is dehumidified by the dehumidification device 27.
[0123] Subsequently, the exhaust gas is guided to a second cooling stage 22 to cool it, preferably to a temperature below -100°C.
[0124] In the second cooling stage 22, the exhaust gas is split, with the first portion directed towards the second stage heat exchanger 32 and the second portion towards a further heat exchanger 34.
[0125] In this example, the second-stage heat exchanger 32 is the high-temperature heat exchanger 12 of the LNG supply system 10, where the LNG is heated from -40°C to 20°C. Alternatively, the second-stage heat exchanger 32 may be in thermal contact with the high-temperature heat exchanger 12 via a coolant.
[0126] Additionally, the LNG released from the LNG tank 11 can also be directly guided to the second-stage heat exchanger 32 via the piping system 14. The cooling temperature of the second-stage heat exchanger 32 can be controlled by setting the ratio of LNG from the LNG tank 11 to the preheated LNG released from the high-temperature heat exchanger 12.
[0127] Valves (not shown) in the piping system 14 may be configured by a control unit (not shown) to control the cooling temperature.
[0128] Additionally, the cooling energy of the residual exhaust gas released from the third cooling stage 23 may be used in the second cooling stage 22. The residual exhaust gas released from the third cooling stage 23 may be discharged into the environment, or, preferably, guided through the piping system 28 to the second cooling stage 22, particularly the second stage heat exchanger 32, as an additional coolant. The residual exhaust gas may be discharged into the environment after passing through the second cooling stage 22.
[0129] In the further heat exchanger 34, the cold energy of frozen CO2 released from the third cooling stage 23 is used.
[0130] The exhaust gases leaving the second-stage heat exchanger 32 and the further heat exchanger 34 are merged and then cooled in the third cooling stage 23, preferably to a temperature below -106°C, for example, in the range of -140°C to -125°C. CO2 is separated from the exhaust gas by freezing, and the frozen CO2 is separated from the remaining exhaust gas.
[0131] The third cooling stage 23 includes a third-stage heat exchanger 33, which in this example is a low-temperature heat exchanger 13 of the LNG supply system, where the LNG is evaporated.
[0132] Alternatively, the third-stage heat exchanger 33 may be in thermal contact with the low-temperature heat exchanger 13 via a coolant.
[0133] The third cooling stage 23 includes a first outlet 24 for frozen CO2 and a second outlet 25 for residual exhaust gas.
[0134] The cryogenic CO2 released from the third cooling stage 23 and used in further heat exchangers is stored in a storage tank 30, which is preferably configured to store the CO2 at a temperature close to the triple point.
[0135] The second-stage heat exchanger 32 and the third-stage heat exchanger 33 can utilize the cold energy of LNG released from the LNG tank.
[0136] Alternatively, the frozen CO2 released from the third cooling stage 23 can be guided directly through the second stage heat exchanger 32 (not shown), eliminating the need for a further heat exchanger 34.
Claims
1. Preferably a large marine engine having at least one cylinder having an inner diameter of at least 200 mm, an internal combustion engine (1) having at least one cylinder (2), - Preferably at a temperature of less than -150°C, an LNG supply system (10) having an LNG tank (11) for storing LNG, - Exhaust gas cooling system (20) and It has, The exhaust gas cooling system (20) is - A first cooling stage (21) for cooling exhaust gas, preferably adapted to use water, for example seawater, as a cooling medium, - A second cooling stage (22) located downstream of the first cooling stage (21) for cooling the exhaust gas to a temperature preferably below -100°C, the second cooling stage (22) having at least one second-stage heat exchanger (32), - Preferably a third cooling stage (23) located downstream of the second cooling stage (22) for further cooling the exhaust gas to a temperature of less than -106°C, wherein the third cooling stage (23) cools the exhaust gas from CO ２ To freeze the frozen CO ２ It is adapted to separate the CO2 from the residual exhaust gas and has at least one third-stage heat exchanger (33), and has frozen CO2. ２ A third cooling stage (23) has a first outlet (24) for the exhaust gas and a second outlet (25) for the residual exhaust gas. It has, An internal combustion engine in which at least one of the at least one second-stage heat exchanger (32) and / or at least one of the at least one third-stage heat exchanger (33) is preferably adapted to use the cold energy of LNG discharged from the LNG tank.
2. The internal combustion engine according to claim 1, wherein the LNG supply system (10) has a low-temperature heat exchanger (13), the low-temperature heat exchanger (13) is one of the at least one third-stage heat exchanger (33), or is in thermal contact with at least one of the at least one third-stage heat exchanger (33) via a coolant.
3. An internal combustion engine according to claim 1 or 2, wherein the LNG supply system (10) has a high-temperature heat exchanger (12), the high-temperature heat exchanger being one of the at least one second-stage heat exchanger (32), or being in thermal contact with at least one of the at least one second-stage heat exchanger (32) via a coolant.
4. The internal combustion engine according to claims 2 and 3, wherein the LNG supply system (10) has a piping system (14) with branching sections for selectively and directly connecting the LNG tank (11) to the low-temperature heat exchanger (13) and / or the high-temperature heat exchanger (12).
5. The second cooling stage (22) receives frozen CO2 released from the third cooling stage (23). ２ An internal combustion engine according to any one of claims 1 to 4, having at least one further heat exchanger (34) adapted to use the cold energy of the internal combustion engine.
6. The internal combustion engine according to any one of claims 1 to 5, wherein the exhaust gas cooling system (20) preferably has a dehumidifying device (27) fluidly arranged between the first stage and the second stage.
7. The internal combustion engine according to any one of claims 1 to 6, wherein the exhaust gas cooling system (20) includes a residual gas piping system (28) that allows residual exhaust gas that has left the third cooling stage (23) to be guided into the second cooling stage (22), so that the cooling energy from the residual exhaust gas that has left the third cooling stage (23) can be used in the second cooling stage (22).
8. The aforementioned internal combustion engine is A branching device for branching the exhaust gas so that it is not guided into the exhaust gas cooling system (20), and / or Preferably an EGR system (40) adapted to branch the exhaust gas upstream of the first cooling stage (21), more preferably a low-pressure EGR system. An internal combustion engine according to any one of claims 1 to 7, having the following:
9. Preferably, CO released from the third cooling stage (23) at a temperature close to the triple point. ２ Cryogenic CO2 adapted for storage ２ An internal combustion engine according to any one of claims 1 to 8, comprising a storage tank (30).
10. Preferably a method for operating an internal combustion engine having at least one cylinder (2), which is a large marine engine having at least one cylinder (2) having an inner diameter of at least 200 mm, as described in any one of claims 1 to 9, wherein the internal combustion engine is driven by LNG and has an LNG tank (11) for storing LNG at a temperature of less than -150°C, and the method is - A step of cooling the exhaust gas discharged from the cylinder (2) in a first cooling stage (21), preferably to a temperature of 20°C to 30°C, preferably using seawater as a cooling medium, - Subsequently, the exhaust gas is cooled to a temperature preferably below -100°C in a second cooling stage (22) having at least one second-stage heat exchanger (32), - Then, cooling the exhaust gas in a third cooling stage (23) having at least one third-stage heat exchanger (33) to a temperature preferably below -106°C, wherein CO ２ is frozen out from the exhaust gas, and the frozen CO ２ is separated from the remaining exhaust gas, which preferably has a CO ２ concentration (molar concentration) of less than 8%, and the step Includes, A method wherein at least one of the at least one second-stage heat exchanger (32) and / or at least one of the at least one first-stage heat exchanger (33) uses the cold energy of LNG released from the LNG tank (11).
11. The LNG is guided through at least one of the at least one second-stage heat exchanger (32) and / or at least one of the at least one third-stage heat exchanger (33), and / or The method according to claim 10, wherein the coolant is guided through at least one of the at least one second-stage heat exchanger (32) and / or at least one of the at least one third-stage heat exchanger (33), and the coolant is in thermal contact with the LNG discharged from the LNG tank (11).
12. Frozen CO released from the third cooling stage (23) ２ The method according to claim 10 or 11, wherein the coolant is guided through at least one of the at least one second-stage heat exchanger (32) and / or is in thermal contact with the coolant guided through at least one of the at least one second-stage heat exchanger (32).
13. The method according to any one of claims 10 to 12, wherein the exhaust gas is dehumidified, particularly upstream of the second cooling stage (22) and / or downstream of the first cooling stage (21).
14. The method according to any one of claims 10 to 13, wherein the residual exhaust gas that has left the third cooling stage (23) is guided into the second cooling stage (22).
15. The method according to any one of claims 10 to 14, wherein the exhaust gas is recirculated and preferably branched upstream of the first cooling stage (21), and more preferably branched downstream of the turbine (41) of the turbocharger (42).