Methods for carbon dioxide capture and a large two-stroke uniflow scavenged internal combustion engine

Abstract

To separate and recover carbon dioxide from exhaust gas in a large 2-stroke turbocharging type uniflow scavenging internal combustion engine.SOLUTION: A method for recovering carbon dioxide includes: supplying carbon-based fuel to a combustion chamber; burning the carbon-based fuel in the combustion chamber to generate combustion gas containing carbon dioxide; recirculating part of the combustion gas and discharging the other part as exhaust gas; supplying pressurized scavenging gas containing at least 40 mass% of, preferably 40-55 mass% of recirculation combustion gas to the combustion chamber; separating carbon dioxide from exhaust gas in a carbon dioxide separation process; and storing the separated carbon dioxide in a storage unit (80).SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The subject matter disclosed herein relates to large two-stroke internal combustion engines, in particular large two-stroke uniflow scavenged internal combustion engines of the crosshead type operating on carbon-based fuels (gaseous or liquid fuels), and to a method of operating this type of engine to reduce carbon dioxide emissions.

[0002] Large two-stroke uniflow scavenging internal combustion engines with crosshead are used, for example, in the propulsion systems of large ships and as prime movers in power plants. These large two-stroke diesel engines are huge in size. Not only because of their huge size, they have a different structure than other internal combustion engines. For example, the exhaust valves can weigh up to 400 kg and the pistons can have diameters of up to 100 cm. The maximum pressure in the combustion chamber during operation is typically several hundred bar. The forces resulting from such high pressure levels and piston sizes are enormous.

[0003] Large two-stroke turbocharged internal combustion engines are operated on liquid fuels (e.g. fuel oil, marine diesel, heavy fuel oil, ethanol, dimethyl ether (DME)) or gas fuels (e.g. natural gas (LNG), petroleum gas (LPG), methanol or ethane).

[0004] An engine that runs on gaseous fuel may operate according to the Otto cycle, in which gaseous fuel is admitted through a fuel valve located near the longitudinal centre of the cylinder liner or in the cylinder cover. In this type of engine, the gaseous fuel is admitted into the cylinder during the piston's upward stroke (from bottom dead centre to top dead centre), well before the exhaust valve closes. The engine compresses a mixture of gaseous fuel and scavenging air in the combustion chamber and ignites the compressed mixture at or near top dead centre (TDC) by a timed ignition means (such as liquid fuel injection).

[0005] Liquid fuelled engines and high pressure injected gas fuelled engines inject gas or liquid fuel when the piston is close to TDC, i.e. when the compression pressure in the combustion chamber is at or near maximum, i.e. these engines operate on the Diesel cycle, i.e. compression ignition.

[0006] The liquid and gaseous fuels used in known large two-stroke turbocharged uniflow scavenged internal combustion engines generally contain carbon, i.e. they are carbon-based fuels, and their combustion produces carbon dioxide, which is emitted into the atmosphere. Carbon dioxide emissions are generally considered to be detrimental to the environment and should be minimized or avoided.

[0007] KR20180072552 discloses a large two-stroke turbocharged uniflow scavenged internal combustion engine with multiple cylinders, each of which has a scavenging port, a scavenging valve, an exhaust gas chamber connected to the cylinder via an individual exhaust valve, a turbocharger, an exhaust gas conduit connecting the outlet of the exhaust gas chamber to the turbine of the turbocharger, a compressor of the turbocharger driven by the turbine, and a scavenging conduit connecting the outlet of the compressor to the inlet of the scavenging chamber. The scavenging conduit 11 has a scavenging cooler, and the scavenging chamber is connected to the cylinder via an individual scavenging port. The engine further comprises an exhaust gas recirculation conduit for recirculating a part of the exhaust gas to the cylinder, the recirculation conduit having a blower or compressor for forcing the recirculated exhaust gas back to the cylinder, a cylinder bypass pipe for transporting a part of the hot scavenging air from the scavenging conduit upstream of the scavenging cooler to the turbine of the turbocharger to bypass the cylinder, and a boiler. The engine is configured to transport at least a first portion of the exhaust gas from the cylinder through a boiler.

[0008] It is an object to provide an engine and method which overcomes or at least mitigates the above mentioned problems.

[0009] These and other objects are achieved by the features of the independent claims. Further specific implementations will become apparent from the dependent claims, the description and the drawings.

[0010] According to the first aspect, there is provided a crosshead type large two-stroke turbocharged uniflow scavenging internal combustion engine as follows. This engine has: a plurality of combustion chambers each defined by a cylinder liner, a piston configured to reciprocate within the cylinder liner, and a cylinder cover; a scavenging port for introducing scavenging gas into the combustion chamber, the scavenging port being disposed in the cylinder liner; an exhaust gas outlet disposed in the cylinder cover and controlled by an exhaust valve; a fuel system configured to supply a carbon-based fuel to the combustion chamber; Equipped with The combustion chamber is configured to combust the carbon-based fuel and generate combustion gases including carbon dioxide; The combustion chamber is connected to a scavenging air receiver through the scavenging port and to a combustion gas receiver through the exhaust gas outlet, The engine further includes an exhaust gas recirculation system configured to recirculate a portion of the combustion gases discharged from the combustion chamber to the scavenging receiver; the exhaust gas recirculation system includes a blower for assisting the flow of combustion gases to the scavenge air receiver; The engine further includes an exhaust system configured to exhaust another portion of the combustion gases generated from the combustion chamber as exhaust gases; the exhaust system includes a turbine of a turbocharging system, the turbine being driven by exhaust gases; The engine further comprises an air intake system having a compressor of the turbocharging system, the compressor being configured to supply pressurized scavenging air to the scavenging air receiver; the exhaust system includes a carbon dioxide separator and a carbon dioxide storage system connected to an outlet of the carbon dioxide separator; The carbon dioxide separation device is configured to receive the exhaust gas, separate at least a portion of the carbon dioxide in the exhaust gas from the exhaust gas, preferably by solidifying and / or liquefying the carbon dioxide, and transport the separated carbon dioxide to the carbon dioxide storage unit.

[0011] Operating an engine with combustion gas recirculation increases the concentration of carbon dioxide in the exhaust gas, allowing for more effective separation of the carbon dioxide from the exhaust gas, and by separating the carbon dioxide from the exhaust gas and storing the carbon dioxide, the amount of carbon dioxide emitted by the engine can be reduced.

[0012] In one example of an implementation of the first approach, the engine includes a control unit configured to adjust the mass ratio of recirculated combustion gas in the scavenging gas to at least 40%, preferably between 40% and 55%.

[0013] In one example of an implementation form of the first approach, the control unit is configured to control a rotation speed of the blower to adjust a ratio of recirculated combustion gas in the scavenging gas.

[0014] In one example of an implementation of the first approach, the engine has a combustion gas-water cooler, preferably a combustion gas-seawater cooler, preferably located upstream of a position where the flow of combustion gas from the engine is split into a recirculated portion and another portion that is exhausted.

[0015] In one implementation of the first aspect, the engine includes a combustion gas-cooling medium heat exchanger and a cooling arrangement configured to circulate a cooling medium through the combustion gas-cooling medium heat exchanger, the combustion gas-cooling medium heat exchanger being preferably located downstream of a location where a flow of combustion gases from the engine is split into a recirculated portion and another portion that is exhausted.

[0016] In one example of an implementation of the first aspect, the combustion gas-coolant heat exchanger is connected to the cooling facility.

[0017] In one example of an implementation of the first aspect, the engine includes a cooler downstream of the turbine that cools the exhaust gas to solidify carbon dioxide in the exhaust gas.

[0018] In one example of an implementation form of the first aspect, the cooler is connected to the cooling equipment.

[0019] In one example of an implementation form of the first approach, the control unit is configured to control the operation of the engine so that the temperature of the exhaust gas when it reaches atmospheric pressure downstream of the turbine is -82°C or lower, thereby solidifying carbon dioxide in the exhaust gas.

[0020] In one implementation of the first approach, the turbine is mechanically coupled to drive the compressor, which is preferably assisted by an electric drive motor. There are operating conditions where the turbine does not provide enough energy to operate the compressor to provide sufficient expansion of the exhaust gases, and therefore sufficient cooling. In these operating conditions, additional energy must be added to the turbocharging system by the electric drive motor.

[0021] In one example of an implementation of the first approach, the compressor is driven by an electric drive motor and the turbine drives an electric generator or alternator. In this setup of the turbocharging system, additional energy that may be required by the turbocharging system can be provided by either the electric drive motor driving the compressor, or from an external power source, which may be in the form of an electric generator or alternator driven by the engine, or by a generator set associated with the engine.

[0022] In one example implementation of the first approach, the engine operates according to an Otto cycle, and gas fuel is introduced into the combustion chamber through a fuel valve as the piston strokes from bottom dead center (BDC) to top dead center (TDC).

[0023] In one example implementation of the first approach, the engine operates on a diesel cycle and gas or liquid fuel is injected into the combustion chamber from a fuel valve as the piston approaches top dead center (TDC).

[0024] According to a second aspect, there is provided a method of operating a large two-stroke turbocharged uniflow scavenged internal combustion engine having multiple combustion chambers, the method comprising: providing a carbon-based fuel to the combustion chamber; combusting the carbon-based fuel in the combustion chamber to generate combustion gases comprising carbon dioxide; recirculating a portion of the combustion gas and discharging another portion of the combustion gas as exhaust gas; supplying a pressurized scavenging gas to the combustion chamber, the scavenging gas comprising at least 40% by mass, preferably 40 to 55% by mass, of recirculated combustion gas; Separating carbon dioxide from the flue gas in a carbon dioxide separation process; storing the separated carbon dioxide in a storage unit; Includes.

[0025] Operating the engine with a high combustion gas recirculation ratio can increase the concentration of carbon dioxide in the exhaust gas and facilitate separation of the carbon dioxide from the exhaust gas, and by separating the carbon dioxide from the exhaust gas and storing the carbon dioxide, emissions of carbon dioxide from the engine can be avoided or at least reduced.

[0026] In one implementation of the second approach, the method includes solidifying (freezing) at least a portion of the carbon dioxide in the flue gas. Freezing the carbon dioxide allows it to be relatively easily separated from other components in the flue gas. Storing the carbon dioxide in a solidified form can be done in a container that does not take up much space and does not need to be pressurized.

[0027] In one example implementation of the second approach, the method includes subjecting the exhaust gas to one or more cooling and expansion processes, thereby solidifying and / or liquefying the carbon dioxide downstream of the turbine.

[0028] In one example implementation of the second aspect, the method includes storing carbon dioxide in liquid or solid form in a storage unit.

[0029] In one example implementation of the second aspect, the method includes controlling a speed of a blower in an exhaust gas recirculation system to adjust the proportion of recirculated combustion gases in the pressurized scavenging gas.

[0030] In one example implementation of the second approach, at least a portion of the expansion process occurs in a turbine.

[0031] In one implementation of the second aspect, the engine has a combustion gas-water cooler, preferably an exhaust gas-sea water cooler, preferably located upstream of a location where a flow of combustion gases from the engine is split into a recirculated portion and another exhausted portion, and the method includes cooling the combustion gases in the combustion gas-water cooler, preferably to a temperature of 40° C. or less, more preferably 31° C. or less.

[0032] In one example of an implementation form of the second approach, the engine comprises an exhaust gas-cooling medium heat exchanger and a cooling equipment, the cooling equipment being configured to circulate a cooling medium through the exhaust gas-cooling medium heat exchanger to a temperature preferably below -10°C, more preferably below -15°C.

[0033] In one example of an implementation of the second approach, solidified water (ice) in the exhaust gas is separated from the exhaust gas by a method such as gravity separation or centrifugation, and is stored or discarded.

[0034] In one example of an implementation form of the second approach, the engine is provided with a cooler downstream of the turbine that further cools the exhaust gas (preferably to a temperature of -80°C or below at atmospheric pressure) to solidify carbon dioxide in the exhaust gas.

[0035] In one example implementation of the second approach, the method includes compressing air in a compressor and mixing combustion gases with the compressed air to obtain a scavenging gas.

[0036] In one example implementation of the second aspect, the method includes compressing the recirculated combustion gases with a blower compressor prior to mixing the combustion gases with compressed air.

[0037] These and other aspects will be apparent from the examples described below. [Brief description of the drawings]

[0038] Various aspects, embodiments, and implementations will be described in detail below with reference to exemplary embodiments illustrated in the drawings. [Figure 1] FIG. 1 is a front view of a large two-stroke diesel engine according to an exemplary embodiment. [Diagram 2] FIG. 2 is a side view of the large two-stroke engine of FIG. [Diagram 3] 2 is a schematic representation of the large two-stroke engine of FIG. 1 according to an embodiment. [Figure 4] 2 is a schematic representation of the large two-stroke engine of FIG. 1 according to another embodiment. [Diagram 5] 2 is a schematic representation of the large two-stroke engine of FIG. 1 according to yet another embodiment. Detailed explanation

[0039] In the following detailed description, the internal combustion engine will be described with reference to an example crosshead type large low-speed two-stroke turbocharged internal combustion engine. Figures 1-3 depict an example of a turbocharged large low-speed two-stroke diesel engine. The engine has a crankshaft 8 and a crosshead 9. Figure 1 is a front view and Figure 2 is a side view. Figure 3 is a schematic representation of the turbocharged large low-speed two-stroke diesel engine of Figures 1 and 2 according to an embodiment, together with its intake and exhaust systems. In this example, the engine has four cylinders in series. A turbocharged large low-speed two-stroke internal combustion engine may have 4 to 14 cylinders arranged in series. The cylinders have cylinder liners carried by an engine frame 11. Such an engine may also be used, for example, as a main engine for a ship or as a stationary engine for driving a generator in a power plant. The total power output of the engine may be, for example, 1000 kW to 110000 kW.

[0040] The engine in this embodiment is a two-stroke uniflow scavenging engine, and scavenging ports 18 are provided in the lower region of the cylinder liner 1. A central exhaust valve 4 is arranged in the cylinder cover 22 at the top of the cylinder liner 1. Scavenging gas is led from the scavenging receiver 2 to the scavenging ports 18 of each cylinder liner 1 when the piston is below the scavenging ports 18. Gas fuel (e.g., methanol, petroleum gas or LPG, natural gas LNG, or ethane) is introduced from the gas fuel valve 30 (gas introduction valve) under the control of the electronic control unit 60 during the piston's upward movement (from BDC to TDC) before the piston passes the fuel valve 30, and / or liquid fuel (e.g., fuel oil) is injected at high pressure (preferably 300 bar or more) from the liquid fuel valve 50 when the piston 10 is at or near TDC. In the former case, the gas fuel is introduced at a relatively low pressure, less than 30 bar, preferably 25 bar, more preferably less than 20 bar. The fuel valves 30 are preferably arranged so as to be equally spaced around the circumference of the cylinder liner. Also, preferably, they are arranged near the center of the cylinder liner in the longitudinal direction. The gas fuel is introduced when the compression pressure is relatively low. In other words, the pressure is much lower than the compression pressure when the piston reaches TDC, so that the gas fuel can be introduced at a relatively low pressure.

[0041] The piston 10 in the cylinder liner 1 compresses the mixture of gaseous fuel and scavenging gas (or scavenging gas in case of operation with only liquid fuel injection at TDC) and ignition is induced at or near TDC by the injection of high pressure liquid fuel from a liquid fuel valve 50, preferably located in the cylinder cover 22. In the case of only liquid fuel injection at or near TDC, ignition is induced by the compression. Combustion then occurs, producing combustion gases including carbon dioxide.

[0042] When the exhaust valve 4 is opened, the combustion gases enter the combustion gas receiver 3 through a combustion gas duct associated with the cylinder 1 and flow onwards via a combustion gas conduit 19 which includes a combustion gas-water cooler 65, which operates with sea water if the engine is installed on a ship. The activity of the combustion gas-water cooler 65 is controlled by the control unit 40 so as to cool the combustion gases from a temperature of 425 to 475°C at the inlet of the combustion gas-water cooler 65 to a temperature of less than 40°C, preferably less than 35, most preferably less than 31°C at the outlet of the combustion gas-water cooler 65. At a location downstream of the combustion gases, preferably to the water cooler 65, the flow of the combustion gases is split into a portion which flows to a combustion gas recirculation system 60 and another portion which flows to an exhaust system. As will be further explained below, the combustion gas recirculation system 60 connects to a scavenging system. The combustion gas recirculation system 60 has a conduit connecting to the scavenging system and may have a (preferably water-operated) scrubber 70 for cleaning the combustion gases. The combustion gas recirculation system 60 also has a blower 75 for forcing the combustion gases through the combustion gas system 60 to the scavenging system. The blower 75 is preferably driven by an electric drive motor 76. The operation of the blower 75 is controlled by the controller 40. In some embodiments, the controller 40 adjusts the operation of the blower 75 to adjust the combustion gas ratio (mass ratio) in the scavenging gases. In some embodiments, the controller 40 is configured to adjust the combustion gas ratio (mass ratio) in the scavenging gases to be 40% or more, preferably 45% or more, and most preferably 40 to 55%. The combustion gas ratio is the mass of the combustion gases as a percentage of the total gas mass induced to the engine.

[0043] The exhaust system comprises an exhaust conduit 63. The exhaust conduit 63 comprises an exhaust gas-cooling medium heat exchanger 66 and is connected to the turbine 6 of the turbocharger 5. The exhaust gas-cooling medium heat exchanger 66 is connected to a cooling facility 68. The cooling facility 60 is configured to circulate the cooling medium through the combustion gas-cooling medium heat exchanger 68 and to cool the exhaust gas to a temperature of -10°C or less, more preferably -15°C or less, at the outlet of the cooling medium heat exchanger 66. Thus, the water in the exhaust gas is solidified (to ice or snow), separated by gravity or centrifugation, and removed through a drain 64. The cooling medium (refrigerant) may have a temperature in the range of -20 to -30°C at the cooling medium inlet of the cooling medium heat exchanger 66. Suitable cooling media (refrigerants) are, for example, ammonia, propane, isobutane, carbon dioxide, and other known cooling media for industrial cooling facilities. The operation of the cooling medium heat exchanger 66 is controlled by the control unit 40 so that the temperature of the exhaust gas at the outlet of the cooling medium heat exchanger 66 becomes a desired temperature.

[0044] From the outlet of the cooling medium heat exchanger 66, the exhaust gas flows to the inlet of the turbine 6. At the outlet of the turbine 6, the temperature of the exhaust gas has been reduced by expansion in the turbine 6 to below -80°C (preferably below -82°C) at ambient pressure. Under these conditions, the carbon dioxide in the exhaust gas solidifies (freezes). The solidified carbon dioxide is separated, for example by a gravity or centrifugal separation process. The separated solid carbon dioxide is stored in a storage unit 80. The remaining exhaust gas, which contains no or only a small amount of carbon dioxide, is discharged into the atmosphere through the outlet 21.

[0045] In this embodiment, the engine has a cooler 69 downstream of the turbine 6 to further cool the exhaust gas in order to solidify the carbon dioxide therein. The cooler 69 cools the exhaust gas to a temperature preferably below -80°C at atmospheric pressure. In this embodiment, the solid carbon dioxide is separated within the cooler 69, at the exit of the cooler 69, or immediately downstream of the cooler 69, for example by a gravity or centrifugal process. The separated solid carbon dioxide is stored in a carbon dioxide unit 80. The carbon dioxide stored in the carbon dioxide storage unit 80 can then be stored in a more permanent means for storing separated carbon dioxide.

[0046] The turbine 6 drives the compressor 7 via a shaft. The compressor 9 is supplied with outside air through an air intake 12. When the turbine 6 does not provide enough power to drive the compressor 7, the turbocharger 5 is assisted by an electric drive motor 77.

[0047] The compressor 7 sends the compressed scavenging air to a scavenging pipe 13 connected to the scavenging air receiver 2. The scavenging air in the scavenging pipe 13 passes through an intercooler 14 for cooling the scavenging air.

[0048] Either upstream (as shown) or downstream (not shown) of the intercooler 14, the combustion gas recirculation system 60 is connected to the scavenging conduit 13. The recirculated combustion gas is mixed with the scavenging air at this location to form the scavenging gas. The control unit 40 is configured so that the scavenging gas contains 40-55% by mass of the combustion gas.

[0049] The cooled scavenging air or gas passes through an auxiliary blower 16 driven by an electric motor 17. The auxiliary blower 16 compresses the scavenging flow when the compressor 7 of the turbocharger 5 cannot provide sufficient pressure for the scavenging receiver 2, i.e. when the engine is at low or partial load. At high engine loads, the turbocharger compressor 7 can provide sufficiently compressed scavenging air and the auxiliary blower 16 is bypassed by a check valve 15.

[0050] The control unit 40 (electronic control unit) may be comprised of a number of interconnected electronic units, each of which may comprise a processor and other hardware for performing the functions of the control unit. The control unit 40 generally controls the operation of the engine, for example, controlling gas fuel introduction (amount and timing), liquid fuel injection (amount and timing), exhaust valve 4 opening and closing (timing and lift), recirculated combustion gas ratio, and operation of various coolers. The control unit 40 receives various signals from sensors indicating the operating conditions of the engine. These signals may include signals representing the engine load, engine speed, blower speed, scavenging air temperature, combustion gas temperature at various locations, and exhaust gas temperature at various locations. They may also include signals representing the pressure of the scavenging air system, the pressure in the combustion chamber, the pressure in the exhaust gas system, and the pressure in the combustion gas recirculation system. The engine is preferably equipped with a variable timing exhaust valve actuation system that allows individual control of exhaust valve timing for each combustion chamber. The control unit 40 is connected to the fuel valve 30, the liquid fuel valve 50, the exhaust valve actuator, the angular position sensor, and the pressure sensor via signal lines or wireless connections. The angular position sensor detects the angle of the crankshaft and produces a signal representative of the position of the crankshaft. A pressure sensor is preferably located in the cylinder cover 22, or alternatively in the cylinder liner 1, and produces a signal representative of the pressure in the combustion chamber.

[0051] Depending on the size of the engine, the cylinder liner 1 is made in a variety of sizes, with typical sizes having a cylinder bore diameter of 250 mm to 1000 mm and a corresponding overall length of 1000 mm to 4500 mm.

[0052] The cylinder liner 1 is placed on a cylinder frame 23, and a cylinder cover 22 is installed on the cylinder liner 1. The cylinder liner 1 and the cylinder cover 22 are arranged so that gas does not leak between them. The piston 10 is configured to reciprocate between bottom dead center (BDC) and top dead center (TDC). These two positions are 180 degrees apart in terms of the rotation angle of the crankshaft 8. The cylinder liner 1 is provided with a number of cylinder lubrication holes distributed in the circumferential direction. These cylinder lubrication holes are connected to a cylinder lubrication line. The cylinder lubrication line supplies cylinder lubricating oil when the piston 10 passes through the cylinder lubrication hole 25. The piston ring (not shown) of the piston 10 then distributes the cylinder lubricating oil over the entire running surface (inner surface) of the cylinder liner.

[0053] A plurality of liquid fuel valves 50, preferably three or four per cylinder, are mounted on the cylinder cover 22 and connected to a liquid fuel supply source (not shown). The liquid fuel valves 50 are preferably arranged around the exhaust valves 4, particularly around a central outlet (opening) of the cylinder cover 22 (controlled by the exhaust valve 4). The injection timing and amount of liquid fuel are controlled by the control unit 40. The liquid fuel valve 50 is only used to inject a small amount of ignition fluid (pilot) when the engine is operated in a gas fuel mode. When the engine is operated in a liquid fuel mode, the liquid fuel valve 50 injects an amount of liquid fuel necessary to operate the engine at the engine load actually used. The cylinder cover 22 may be provided with a pre-chamber (not shown). Also, a tip of the liquid fuel valve 50, typically a tip provided with a nozzle having one or more nozzle holes, is arranged so that pilot oil (ignition fluid) is injected into the pre-chamber and atomized. The pre-chamber assists in reliable ignition. In some embodiments, the vestibule is a dual vestibule, ie, two vestibules in series.

[0054] The fuel valve 30 is mounted on the cylinder liner 1 (or the cylinder cover 22). The fuel valve 30 has a nozzle located substantially flush with the inner surface of the cylinder liner 1. The rear end of the fuel valve 30 protrudes from the outer wall of the cylinder liner 1. Usually, one or two, sometimes even three or four fuel valves 30 are arranged in each cylinder liner 1, distributed in the circumferential direction of the cylinder liner 1 (preferably distributed at equal intervals in the circumferential direction). In this embodiment, the fuel valve 30 is arranged exactly in the center of the cylinder liner 1 in the longitudinal direction. The fuel valve 30 is connected to a pressurized source of gaseous fuel 40 (e.g., methanol, LPG, LNG, ethane or ammonia). That is, when the fuel valve 30 is supplied, the fuel is in a gaseous phase. Since the gaseous fuel is introduced during the stroke from BDC to TDC of the piston 10, the pressure of the gaseous fuel supply source only needs to be higher than the pressure present in the cylinder liner 1. Typically, a pressure of less than 20 bar is sufficient for the gas fuel to be delivered to the fuel valve 30. The fuel valve 30 is connected to a control unit 40. The control unit 40 determines when the fuel valve 30 opens and closes, and for how long the valve is open.

[0055] In some embodiments, the liquid fuel for ignition is heavy fuel oil, marine diesel, heavy fuel oil, ethanol, or dimethyl ether (DME).

[0056] The gas mode of operation may be one of several operating modes of the engine. Other modes may include a liquid fuel mode of operation in which all of the fuel required for the operation of the engine is supplied in liquid form through the liquid fuel valve 50. In the gas fuel mode of operation, the engine is primarily fueled by gas fuel, which is introduced at relatively low pressure during the piston stroke from BDC to TDC. That is, the major portion of the energy supplied to the engine is provided by such gas fuel. On the other hand, in comparison to the gas fuel, liquid fuel is used in smaller amounts and contributes relatively little to the amount of energy supplied to the engine. The purpose of the liquid fuel is to ignite at a predetermined time. That is, the liquid fuel acts as an ignition fluid.

[0057] In this manner, the engine of the present embodiment can be a dual fuel engine having a mode in which it operates solely on liquid fuel and a mode in which it operates almost exclusively on gas fuel.

[0058] The operation of the engine includes: supplying a carbon-based fuel (liquid and / or gaseous fuel) to a combustion chamber; combusting the carbon-based fuel in the combustion chamber to generate combustion gases containing carbon dioxide; recirculating a portion of the combustion gases and discharging another portion of the combustion gases as exhaust gas; supplying a pressurized scavenging gas to the combustion chamber, the scavenging gas containing at least 40% by mass, preferably 40 to 55% by mass, of the recirculated combustion gas; separating carbon dioxide from the exhaust gas in a carbon dioxide separation process; and storing the separated carbon dioxide in a storage unit 80; Includes.

[0059] In the process, the exhaust gas undergoes a cooling and expansion process, and the carbon dioxide in the exhaust gas is solidified (frozen) at the outlet of the turbine 6 or in a cooler 69 downstream of the turbine 6. The frozen carbon dioxide is separated, for example by a gravity separation process or a centrifugation process, and then stored in a solid state in a storage unit 80. In some embodiments, the storage unit 80 is a thermally insulated, non-pressurized vessel or tank.

[0060] The control unit 40 controls the speed of the blower 75 of the exhaust gas recirculation system 60 to adjust the proportion of recirculated combustion gas in the pressurized scavenging gas, preferably to a proportion of 40% by mass, in order to increase the concentration of carbon dioxide in the combustion gas. In some embodiments, the control unit 40 is configured to adjust the recirculated combustion gas ratio such that the carbon dioxide concentration in the combustion gas is at least doubled compared to operation without combustion gas recirculation.

[0061] At least a part of the expansion process of the exhaust gas is carried out in the turbine 6. This expansion process significantly reduces the temperature and pressure of the exhaust gas, preferably to a temperature of -82°C or less at atmospheric pressure, thereby solidifying the carbon dioxide in the exhaust gas.

[0062] Figure 4 shows another embodiment of the engine. In this embodiment, features and functions similar to those already described or illustrated are numbered with the same reference numerals as previously used. The engine and its operation in this embodiment is substantially similar to the previous embodiment, and therefore only the differences from the previous embodiment will be described in detail.

[0063] In this embodiment, the compressor 7 is driven by an electric drive motor 78. The turbine 6 drives an electric generator or alternator 79. In this set-up of the turbocharging system, additional energy that may be required by the turbocharging system is provided by the electric drive motor 78 which drives the compressor 7. Here, the electric drive motor 78 is powered by an electrical power source, which may be in the form of an electric generator or alternator driven by the engine. The electric drive motor 78 may also be powered by a power generation system on board the engine.

[0064] In this embodiment, the engine is shown as a compression ignition engine (operating according to the diesel principle) in which carbon-based fuel (gaseous or liquid) is injected at high pressure when the piston 10 is at or near TDC. The engine shown does not require a pre-chamber in the cylinder liner 10 nor a fuel admission valve 30. However, the engine according to this embodiment can also be operated according to the Otto principle with gaseous fuel being admitted during the stroke of the piston 10 from BDC to TDC.

[0065] In this embodiment, the control unit 40 is configured to operate the engine such that the conditions (i.e. pressure and temperature) at the outlet of the turbine 6 solidify the carbon dioxide in the exhaust gas and separate the solidified carbon dioxide at the outlet of the turbine 6 by gravity separation or centrifugation process and store it in the carbon dioxide storage unit 80.

[0066] Figure 5 shows another embodiment of the engine. In this embodiment, features and functions similar to those already described or illustrated are numbered with the same reference numerals as previously used. The engine and its operation in this embodiment is substantially similar to the previous embodiment, and therefore only the differences from the previous embodiment will be described in detail.

[0067] In this embodiment the engine is shown as a gas-injected engine operating according to the Otto principle, but it should be understood that this embodiment could equally well function with a high pressure fuel injected engine operating according to the Diesel principle.

[0068] In this embodiment, no measures are taken to lower the temperature of the exhaust gas at the outlet of the turbine 6 below normal. Therefore, a combustion gas-water cooler is not required, and an exhaust gas-cooling medium cooler connected to a cooling facility is also not required. Therefore, the temperature of the exhaust gas remains the same as in the past, in the temperature range of 180°C to 250°C.

[0069] Downstream of the turbine 6 , a carbon dioxide separation unit 88 separates carbon dioxide from the exhaust gas and stores the separated carbon dioxide in a carbon dioxide container 80 .

[0070] In this embodiment, the carbon dioxide separation unit 88 dries the exhaust gas, compresses the exhaust gas, and then performs an expansion process that subjects the exhaust gas to one or more cooling loops to liquefy or solidify the carbon dioxide in the exhaust gas, and then separates the liquid or solid exhaust carbon dioxide for storage in the liquid or solid carbon dioxide storage unit 80.

[0071] In another embodiment (not shown in the drawings), the carbon dioxide separation unit 88 separates the carbon dioxide from the flue gas using a carbon dioxide absorber (e.g., using an absorbing solvent). The carbon dioxide separation unit 88 is operatively connected to a regenerator, e.g., an amine regenerator. The regenerator may use steam to strip the carbon dioxide from the absorbing solvent.

[0072] Various ways of understanding and implementation of the invention have been described with several examples. The above embodiments can be combined in various ways. In addition, by studying the specification, drawings, and claims of this application, a person skilled in the art will understand and be able to embody many variations in addition to the described examples in carrying out the invention described in the claims. The words "comprise", "have", and "include" in the claims do not exclude the presence of elements or steps not described. Even if the number of elements described in the claims is not explicitly stated as being multiple, the presence of the elements is not excluded. The functions of several elements described in the claims may be performed by a single processor, controller, or other unit. Even if several items are described in separate dependent claims, this does not exclude them from being combined and may be advantageously combined. The signs used in the claims should not be interpreted as limiting the scope of the invention.

Claims

1. A crosshead type large two-stroke turbocharged uniflow scavenging internal combustion engine, a plurality of combustion chambers each defined by a cylinder liner, a piston configured to reciprocate within the cylinder liner, and a cylinder cover; a scavenging port for introducing scavenging gas into the combustion chamber, the scavenging port being disposed in the cylinder liner; an exhaust outlet disposed in the cylinder cover and controlled by an exhaust valve; a fuel system configured to supply a carbon-based fuel to the combustion chamber; Equipped with The combustion chamber is configured to combust the carbon-based fuel and generate combustion gases including carbon dioxide; The combustion chamber is connected to a scavenging air receiver via the scavenging port and is connected to a combustion gas receiver via the exhaust outlet, The engine further includes an exhaust gas recirculation system configured to recirculate a portion of the combustion gases discharged from the combustion chamber to the scavenging receiver; the exhaust gas recirculation system includes a blower for assisting the flow of combustion gases to the scavenge air receiver; The engine further comprises a control unit configured to control a mass ratio of recirculated combustion gas in the scavenging gas to at least 45% to increase a carbon dioxide concentration in the exhaust gas; The engine further includes an exhaust system configured to exhaust another portion of the combustion gases generated from the combustion chamber as exhaust gases; the exhaust system includes a turbine of a turbocharging system, the turbine being driven by exhaust gases; The engine further comprises an air intake system having a compressor of the turbocharging system, the compressor being configured to supply pressurized scavenging air to the scavenging air receiver; The exhaust system includes a carbon dioxide separator and a carbon dioxide storage unit connected to an outlet of the carbon dioxide separator; the carbon dioxide separation device is configured to receive the flue gas and separate at least a portion of the carbon dioxide in the flue gas from the flue gas, preferably by liquefying and / or solidifying the carbon dioxide, and deliver the separated carbon dioxide to the carbon dioxide storage unit; institution.

2. 10. The engine of claim 1, further comprising a control configured to adjust a mass proportion of recirculated combustion gas in the scavenging gas to between 45% and 55%.

3. The engine of claim 2 , wherein the control unit is configured to control a rotation speed of the blower to adjust a proportion of recirculated combustion gas in the scavenging gas.

4. The engine according to claim 2 , wherein the control unit is configured to control operation of the engine so that the temperature of the exhaust gas is −82° C. or lower when the exhaust gas reaches atmospheric pressure downstream of the turbine.

5. 2. An engine according to claim 1, comprising a combustion gas-water cooler, preferably a combustion gas-sea water cooler, preferably located upstream of a location where the flow of combustion gases from the engine is split into a recirculated portion and another portion which is exhausted.

6. 6. An engine according to any preceding claim, comprising a combustion gas-cooling medium heat exchanger and a cooling arrangement arranged to circulate a cooling medium through the combustion gas-cooling medium heat exchanger, the combustion gas-cooling medium heat exchanger preferably being arranged downstream of a position at which a flow of combustion gases from the engine is divided into a recirculated portion and another portion which is exhausted.

7. An engine according to any one of claims 1 to 5, comprising, downstream of the turbine, a cooler for cooling the exhaust gas in order to liquefy and / or solidify the carbon dioxide therein.

8. An engine according to any preceding claim, wherein the turbine is mechanically coupled to drive the compressor, preferably assisted by an electric drive motor.

9. 6. An engine according to any preceding claim, wherein the compressor is driven by an electric drive motor and the turbine drives an electric generator or alternator.

10. 1. A method of operating a large two-stroke turbocharged uniflow scavenged internal combustion engine having multiple combustion chambers, comprising the steps of: supplying a carbon-based fuel to the combustion chamber; combusting the carbon-based fuel in the combustion chamber to generate combustion gases comprising carbon dioxide; recirculating a portion of the combustion gas and discharging another portion of the combustion gas as exhaust gas; supplying a pressurized scavenging gas to the combustion chamber; controlling said mass ratio such that said pressurized scavenging gas comprises at least 45% by mass, preferably 45% to 55% by mass of recirculated combustion gas to increase the carbon dioxide concentration in the exhaust gas; separating carbon dioxide from the flue gas in a carbon dioxide separation process; storing the separated carbon dioxide in a storage unit; A method comprising:

11. 11. The method of claim 10, comprising subjecting the exhaust gas to one or more cooling and expansion processes, thereby liquefying and / or solidifying carbon dioxide downstream of a turbine of a turbocharging system of the engine.

12. The method of claim 11 , wherein at least a portion of the expansion process occurs in the turbine.

13. 12. The method according to claim 11, wherein the engine comprises a cooler downstream of the turbine for further cooling the exhaust gas in order to liquefy and / or solidify the carbon dioxide therein, preferably to a temperature of -80°C or lower at atmospheric pressure.

14. 14. The method of any of claims 10 to 13, comprising storing carbon dioxide in liquid or solid form in the storage unit.

15. 14. A method according to any one of claims 10 to 13, comprising controlling the speed of a blower in an exhaust gas recirculation system to adjust the proportion of recirculated combustion gas in the pressurized scavenging gas.

16. A method according to any of claims 10 to 13, wherein the engine has a combustion gas-water cooler, preferably an exhaust gas-sea water cooler, preferably located upstream of a location where a flow of combustion gases from the engine is divided into a recirculated portion and another portion which is exhausted, the method comprising cooling the combustion gases in the combustion gas-water cooler, preferably to a temperature of 40°C or less, more preferably 31°C or less.

17. A method according to any of claims 10 to 13, wherein the engine is provided with a combustion gas-cooling medium heat exchanger, preferably downstream of a position where a flow of combustion gases from the engine is divided into a recirculated portion and another portion which is exhausted, and further comprising cooling equipment, the cooling equipment being arranged to circulate a cooling medium through an exhaust gas-cooling medium heat exchanger and to cool the exhaust gases, preferably to below -10°C, more preferably to below -15°C.

18. A crosshead type large two-stroke turbocharged uniflow scavenging internal combustion engine, a plurality of combustion chambers each defined by a cylinder liner, a piston configured to reciprocate within the cylinder liner, and a cylinder cover; a scavenging port for introducing scavenging gas into the combustion chamber, the scavenging port being disposed in the cylinder liner; an exhaust outlet disposed in the cylinder cover and controlled by an exhaust valve; a fuel system configured to supply a carbon-based fuel to the combustion chamber; Equipped with The combustion chamber is configured to combust the carbon-based fuel and generate combustion gases including carbon dioxide; The combustion chamber is connected to a scavenging air receiver via the scavenging port and is connected to a combustion gas receiver via the exhaust outlet, The engine further includes an exhaust gas recirculation system configured to recirculate a portion of the combustion gases discharged from the combustion chamber to the scavenging receiver; the exhaust gas recirculation system includes a blower for assisting the flow of combustion gases to the scavenge air receiver; The engine further includes an exhaust system configured to exhaust another portion of the combustion gases generated from the combustion chamber as exhaust gases; the exhaust system includes a turbine of a turbocharging system, the turbine being driven by exhaust gases; The engine further comprises an air intake system having a compressor of the turbocharging system, the compressor being configured to supply pressurized scavenging air to the scavenging air receiver; the exhaust system includes a carbon dioxide separator disposed downstream of the turbine, and a carbon dioxide storage unit connected to an outlet of the carbon dioxide separator; the carbon dioxide separation device is configured to receive flue gas and separate at least a portion of the carbon dioxide in the flue gas from the flue gas, preferably by liquefying and / or solidifying the carbon dioxide, and deliver the separated carbon dioxide to the carbon dioxide storage unit; the engine further comprises a combustion gas-water cooler disposed upstream of a location where combustion gas discharged from the combustion chamber is divided into a recirculated portion and an exhaust portion, and a combustion gas-coolant heat exchanger disposed downstream of the location and upstream of the turbine, institution.

19. The combustion gas-cooling medium heat exchanger is configured to reduce the temperature of the exhaust gas to a level at which at least a portion of the moisture in the exhaust gas solidifies; The engine is provided with a drain for discharging moisture solidified by the combustion gas-cooling medium heat exchanger.

20. The engine of claim 18.

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