Method and large two-stroke uniflow scavenged internal combustion engine for carbon dioxide recovery

Abstract

To provide a crosshead type large two-stroke uniflow scavenged internal combustion engine configured to be operated with a carbon-based fuel and reduce carbon dioxide emissions.SOLUTION: A method includes: supplying a carbon-based fuel to combustion chambers; combusting the carbon-based fuel in the combustion chambers, thereby producing an exhaust gas flow containing carbon dioxide; recirculating a first portion of the exhaust gas flow, and exhausting a second portion of the exhaust gas flow; cooling the first portion of the recirculated exhaust gas flow in an exhaust gas system using a solvent thereby heating the solvent; chemically absorbing carbon dioxide from the second portion of the exhaust gas flow into a solvent by supplying a flow of carbon dioxide lean solvent to an absorber and discharging a flow of carbon dioxide rich solvent from the absorber 42 to a desorber 66 and reboiler 62 assembly; and regenerating the carbon rich solvent in the assembly through heating by supplying at least a portion of recirculated exhaust gas to the assembly for heating the solvent.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The subject matter disclosed herein relates to large two-stroke internal combustion engines, in particular crosshead type large two-stroke uniflow scavenged internal combustion engines that are operated on carbon-based fuels (gaseous or liquid fuels) and that are configured to reduce carbon dioxide emissions, and to methods of operating such types of engines.

[0002] Large crosshead two-stroke uniflow scavenging internal combustion engines 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 enormous in size. Their size alone is not the only reason why they are unique from other internal combustion engines. For example, the exhaust valves can weigh up to 400 kg, and the pistons can be as large as 100 cm in diameter. The maximum pressure in the combustion chamber during operation is typically several hundred bar. The forces generated by these high pressure levels and piston sizes are enormous.

[0003] Large two-stroke turbo 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. methane, natural gas (LNG), petroleum gas (LPG), methanol or ethane).

[0004] Gaseous fueled engines may operate according to the Otto cycle, in which gaseous fuel is introduced through a fuel valve located near the longitudinal center of the cylinder liner or in the cylinder cover. In this type of engine, the gaseous fuel is introduced into the cylinder during the piston's upward stroke (from bottom dead center to top dead center), 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 center (TDC) using a timed ignition means (e.g., liquid fuel injection).

[0005] Liquid-fueled engines and high-pressure-injected gas-fueled 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. These engines operate on the Diesel cycle, i.e., compression ignition.

[0006] 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 a cause of climate change and should be minimized or avoided.

[0007] Known carbon capture technologies typically include post-combustion CO2 capture, pre-combustion CO2 capture, and oxyfuel combustion (O x Pre-combustion CO2 capture is the separation and capture of carbonaceous components before the combustion of fuel.

[0008] In pre-combustion carbon dioxide capture, fuel is first reacted with oxygen and steam, and then further processed in a water-gas shift reactor to produce a mixture of H2 and CO2. The CO2 is captured from a pressurized gas mixture containing 15% to 40% CO2. The advantage of pre-combustion carbon dioxide capture technology is that it significantly reduces the amount of gas required for processing and increases the CO2 concentration in the gas. This reduces the energy consumption and capital investment of the separation process.

[0009] In oxyfuel combustion, carbon-based fuels are burned in recirculated exhaust gas and pure O2 rather than in air. However, the high cost of O2 separation limits its commercial viability. Oxyfuel combustion technology consists of an air separation unit that separates nitrogen from air. The carbon-based fuel is then burned in recirculated exhaust gas and pure O2. The exhaust gas, which primarily consists of particulate matter from combustion, CO2, sulfur oxides from the fuel, and water, is sent to a particulate matter removal unit and a sulfur removal unit, where the water is condensed and removed, leaving a compressible CO2 stream. The main advantage is that nearly 100% CO2 can be captured.

[0010] Post-combustion CO2 capture technologies involve burning carbon-based fuels and capturing CO2 from flue gases, similar to conventional energy generation. Carbon separation technologies can be broadly divided into four categories: absorption, adsorption, membrane, and cryogenic. Amine solvents can be used to absorb and capture CO2 from flue gases. Here, the CO2 is captured in the solvent, followed by an amine regeneration process. The drawbacks are the extremely large size of the power plant and the high energy requirements of the carbon dioxide capture process, particularly for the amine solvent regeneration. Another challenge with amine absorption is the size of the absorber tower, which is related to the volumetric flow rate of the exhaust gases. Because the absorber is located on the low-pressure side of the turbocharger, the volumetric flow rate is large and varies with engine load.

[0011] DK202270534A1 proposes a heat transfer medium (e.g., steam or water) to transfer energy from the high-pressure boiler in the EGR system to heat the amine solution (solvent) in the reboiler. However, steam is a limited and expensive resource on ships, and furthermore, the additional heat transfer process results in a loss of available energy in the stripping process.

[0012] It is an object to provide an engine and method that overcomes or at least mitigates the above-mentioned problems.

[0013] These and other problems are solved by the features of the independent claims. More specific implementations will become apparent from the dependent claims, the description and the drawings.

[0014] According to the first aspect, there is provided a crosshead type large two-stroke turbocharged uniflow scavenging internal combustion engine as follows. at least one combustion chamber defined by a cylinder liner, a piston configured to reciprocate within the cylinder liner, and a cylinder cover; a scavenging port disposed in the cylinder liner for introducing scavenging gas into the at least one combustion chamber; a fuel system configured to supply a carbon-based fuel to the at least one combustion chamber; wherein the at least one combustion chamber is configured to combust a carbon-based fuel to produce exhaust gases comprising carbon dioxide, and the engine further comprises: an exhaust outlet disposed in the cylinder cover and controlled by an exhaust valve; the at least one combustion chamber is connected to a scavenging air receiver through the scavenging port and to an exhaust gas receiver through the exhaust outlet, and the engine further comprises: an exhaust system having a turbine driven by the exhaust flow, the turbine being of a turbocharging system; an air intake system including a compressor of the turbocharging system configured to supply pressurized scavenging air to the scavenging air receiver; an exhaust gas recirculation system configured to recirculate a portion of the exhaust gas flow discharged from the at least one combustion chamber from upstream of the turbine of the turbocharging system to the scavenging air receiver, the exhaust gas recirculation system having a first blower for assisting the flow of exhaust gas to the scavenging air receiver; an absorber, preferably an absorption tower, for absorbing carbon dioxide into a solvent; a desorber and reboiler assembly for desorbing carbon dioxide from the solvent; Equipped with the absorber has a solvent inlet for receiving carbon dioxide-lean solvent from the desorber and a solvent outlet for supplying carbon dioxide-rich solvent to the desorber; the absorber is configured to separate carbon dioxide from the exhaust gas by chemical absorption in the solvent for at least a portion of the exhaust stream or recirculated exhaust stream passing through the absorber; the assembly having an inlet for receiving carbon dioxide-rich solvent from the absorber and an outlet for supplying carbon dioxide-lean solvent to the absorber; the assembly is configured to heat the solvent to release carbon dioxide from the solvent; the reboiler is disposed within the exhaust gas recirculation system, and the reboiler is configured as a heat exchanger through which the recirculated exhaust gas flows and the solvent flows to exchange heat between the recirculated exhaust gas and the solvent; and / or The reboiler is disposed in the exhaust system and is disposed upstream of the turbine of the turbocharging system, and is configured as a heat exchanger through which recirculated exhaust gas flows on one side and the solvent flows on the other side to exchange heat between the exhaust gas and the solvent.

[0015] Using the reboiler that vaporizes CO2 from the engine's rich amine solution in the EGR system as a heat exchanger reduces the running costs of amine absorbent CO2 capture and avoids the need for additional systems for handling and controlling the heat transfer medium.

[0016] In the engine, the high pressure boiler, desorber and reboiler can be combined to reduce the installation area on the ship.

[0017] In one example implementation of the first aspect, the reboiler is configured to exchange heat between exhaust gas in the exhaust gas recirculation system and the solvent, thereby cooling the exhaust gas in the exhaust gas recirculation system and heating the solvent.

[0018] In one implementation of the first aspect, the exhaust gas recirculation system includes a scrubber, preferably a wet scrubber, preferably located downstream of the reboiler in the exhaust gas recirculation system.

[0019] In one example of implementation of the first aspect, the engine comprises a control unit configured to adjust the mass fraction of recirculated exhaust gas in the scavenging gas to at least 40%, preferably 50%.

[0020] In one example implementation of the first aspect, the control unit is configured to control the speed of the first blower to adjust the proportion of exhaust gas that is recirculated, and / or the control unit is configured to control the position of a control valve in the exhaust system to adjust the proportion of exhaust gas that is recirculated.

[0021] According to a second aspect, there is provided a method of operating a large two-stroke turbocharged uniflow scavenged internal combustion engine having a plurality of combustion chambers and a turbocharging system, the method comprising: supplying a carbon-based fuel to the combustion chamber; burning a carbon-based fuel in a combustion chamber to produce an exhaust stream comprising carbon dioxide; recirculating a first portion of the exhaust stream from a high pressure side of the turbocharging system to a cylinder and exhausting a second portion of the exhaust stream; supplying a pressurized scavenging air flow including recirculated exhaust gas to said combustion chamber; chemically absorbing carbon dioxide from the first and / or second portions of the vent stream into a solvent by feeding a carbon dioxide-lean solvent stream to an absorber and discharging a carbon dioxide-rich solvent stream from the absorber to a desorber and reboiler assembly; Including, regenerating the carbon-rich solvent in the assembly by heating at least the first portion of the exhaust stream by passing it through the assembly, thereby heating the solvent and cooling the first portion of the exhaust stream by heat exchange between the first portion of the exhaust stream and the solvent; and / or regenerating the carbon-rich solvent in the assembly by heating at least the second portion of the exhaust stream through the assembly on the high pressure side of the turbocharging system, thereby heating the solvent and cooling the first portion of the exhaust stream by heat exchange between the first portion of the exhaust stream and the solvent; Includes:

[0022] In one implementation of the second aspect, the method includes recirculating at least 40% by mass of the exhaust stream. Preferably, at least 50% by mass of the exhaust stream is recirculated.

[0023] In one example implementation of the second aspect, the method includes controlling the speed of a first blower of an exhaust gas recirculation system to adjust the proportion of recirculated exhaust gas in the pressurized scavenging gas, and / or controlling the position of a control valve of the exhaust system to control the proportion of recirculated exhaust gas.

[0024] In one example implementation of the second aspect, the method includes feeding the gas stream comprising carbon dioxide and water vapor or steam generated in the desorber to a separator for separating the carbon dioxide and water vapor or steam, the separator preferably being a knock-out drum to obtain a gas stream comprising primarily carbon dioxide and a liquid stream comprising primarily water.

[0025] In one example implementation of the second aspect, the method comprises supplying the gas stream comprising primarily carbon dioxide to a liquefaction unit and liquefying the gas stream comprising primarily carbon dioxide to obtain a liquefied carbon dioxide stream, preferably further comprising directing the liquefied carbon dioxide stream to a liquefied carbon dioxide storage device.

[0026] According to a third aspect, there is provided a crosshead type large two-stroke turbocharged uniflow scavenged internal combustion engine, comprising: at least one combustion chamber defined by a cylinder liner, a piston configured to reciprocate within the cylinder liner, and a cylinder cover; a scavenging port disposed in the cylinder liner for introducing scavenging gas into the at least one combustion chamber; a fuel system configured to supply a carbon-based fuel to the at least one combustion chamber; wherein the at least one combustion chamber is configured to combust a carbon-based fuel to produce exhaust gases comprising carbon dioxide, and the engine further comprises: an exhaust outlet disposed in the cylinder cover and controlled by an exhaust valve; the at least one combustion chamber is connected to a scavenging air receiver through the scavenging port and to an exhaust gas receiver through the exhaust outlet, and the engine further comprises: an exhaust system having a turbine driven by the exhaust flow, the turbine being of a turbocharging system; an air intake system including a compressor of the turbocharging system configured to supply pressurized scavenging air to the scavenging air receiver; an exhaust gas recirculation system having a first blower for assisting exhaust gas flow to the scavenging air receiver, the exhaust gas recirculation system being configured to recirculate a portion of exhaust gases discharged from the at least one combustion chamber from upstream of the turbine of the turbocharging system to the scavenging air receiver; an absorber, preferably an absorption tower, for absorbing carbon dioxide into a solvent; a desorber and reboiler assembly for desorbing carbon dioxide from the solvent; Equipped with the absorber has a solvent inlet for receiving carbon dioxide-lean solvent from the desorber and a solvent outlet for supplying carbon dioxide-rich solvent to the desorber; the assembly having an inlet for receiving carbon dioxide-rich solvent from the absorber and an outlet for supplying carbon dioxide-lean solvent to the absorber; the assembly is configured to heat the solvent to release carbon dioxide from the solvent; The absorber comprises: at least a portion of the recirculated exhaust gas stream is passed through the absorber to separate carbon dioxide from the exhaust gas by chemical absorption in a solvent; and / or At least a portion of the exhaust gas flow upstream of the turbine of the turbocharger is arranged to pass through an absorber to separate carbon dioxide from the exhaust gas by chemical absorption in a solvent.

[0027] By placing an absorber in the EGR flow path on the high pressure side of a turbocharging system or in the exhaust gas flow path on the high pressure side of a turbocharging system, the absorber volume requirements can be reduced, assuming a constant reaction time, due to the higher pressure and gas density.

[0028] In EGR systems, a cooler is required to cool the EGR gas. The absorber has a certain CO2 capture efficiency. Recirculating the EGR gas improves efficiency because the CO2 that slips through the absorber is returned to the exhaust receiver after combustion.

[0029] In one implementation of the third aspect, the absorber is positioned within the exhaust gas recirculation system such that all of the recirculated exhaust gas passes through the absorber.

[0030] In one implementation of the third aspect, the reboiler is disposed within the exhaust gas recirculation system and configured as a heat exchanger through which the recirculated exhaust gas flows and the solvent flows to exchange heat between the recirculated exhaust gas and the solvent.

[0031] In one example implementation of the third aspect, the exhaust gas recirculation system branches into a first string and a second string, the first string connects to the air supply system at a location downstream of the compressor of the turbocharging system, and the second string connects to the exhaust system upstream of the turbine of the turbocharging system, the absorber is disposed in the exhaust gas recirculation system upstream of the branching location, the first string preferably includes a first blower, the second string preferably includes a second blower, and the reboiler is preferably disposed upstream of the branching location.

[0032] In one implementation of the third aspect, the second string passes through a heat exchanger, preferably an integral element of the reboiler, for heat exchange between the recirculated exhaust gas in the second string and the recirculated exhaust gas in the exhaust gas recirculation system upstream of the branching location.

[0033] In one example implementation of the third aspect, the exhaust gas recirculation system branches into a first string and a second string, the first string connects to the charge air system at a location downstream of the compressor of the turbocharging system, the second string connects to the exhaust system upstream of the turbine of the turbocharging system, the absorber is located in the second string, and the reboiler is preferably located upstream of the branching location.

[0034] In one example of an implementation of the third aspect, the first string includes a first blower, the second string includes a second blower, and the engine preferably includes a control unit that controls the rotation speeds of the first blower and the second blower to control the amount of exhaust gas flowing through the first string and the second string.

[0035] In one example of an implementation of the third aspect, the second string passes through a heat exchanger for heat exchange between the recirculated exhaust gas in the second string and the recirculated exhaust gas in the exhaust gas recirculation system upstream of the branching position, and the heat exchanger is preferably an integrated element of the reboiler.

[0036] According to a fourth aspect, there is provided a method of operating a large two-stroke turbocharged uniflow scavenged internal combustion engine having a plurality of combustion chambers and a turbocharging system, the method comprising: supplying a carbon-based fuel to the combustion chamber; burning a carbon-based fuel in a combustion chamber to produce an exhaust stream comprising carbon dioxide; recirculating a first portion of the exhaust flow from a cylinder and exhausting a second portion of the exhaust flow from the cylinder at a high pressure side of the turbocharging system; supplying a pressurized scavenging air flow to the combustion chamber, the pressurized scavenging air flow including the first portion of the exhaust flow from the cylinder; chemically absorbing carbon dioxide into a solvent from the first portion of the exhaust stream from the cylinder by supplying a carbon dioxide-lean solvent stream to an absorber and discharging a carbon dioxide-rich solvent stream from the absorber to a desorber and reboiler assembly, and / or chemically absorbing carbon dioxide into a solvent from the second portion of the exhaust stream from the cylinder only on the high pressure side of the turbocharging system; Regenerating the carbon-rich solvent in said assembly; Includes:

[0037] In one example implementation of the fourth aspect, the absorber is configured so that at least a portion of the first portion of the exhaust flow passes through the absorber and / or so that at least a portion of the second portion of the exhaust flow passes through the absorber.

[0038] In one example implementation of the fourth aspect, the first portion of the exhaust stream is passed through the assembly, thereby heating the solvent and cooling the first portion of the exhaust stream by heat exchange between the first portion of the exhaust stream and the solvent.

[0039] In one implementation of the fourth aspect, the method includes recirculating at least 40% by mass of the exhaust stream. Preferably, at least 50% by mass of the exhaust stream is recirculated.

[0040] In one example implementation of the fourth aspect, the method includes controlling the speed of a first blower of an exhaust gas recirculation system to adjust the proportion of recirculated exhaust gas in the pressurized scavenging gas, and / or controlling the position of a control valve of the exhaust system to control the proportion of recirculated exhaust gas.

[0041] In one example implementation of the fourth aspect, the method includes feeding a gas stream comprising carbon dioxide and water vapor or steam generated in the desorber to a separator for separating the carbon dioxide and water vapor or steam, the separator preferably being a knock-out drum to obtain a gas stream comprising primarily carbon dioxide and a liquid stream comprising primarily water.

[0042] In one example implementation of the fourth aspect, the method comprises supplying the gas stream comprising primarily carbon dioxide to a liquefaction unit and liquefying the gas stream comprising primarily carbon dioxide to obtain a liquefied carbon dioxide stream, preferably further comprising directing the liquefied carbon dioxide stream to a liquefied carbon dioxide storage device.

[0043] These and other aspects will become more apparent from the examples described below. [Brief explanation of the drawings]

[0044] Various aspects, embodiments and implementations will now be described in detail with reference to exemplary embodiments illustrated in the drawings. [Figure 1]1 is a perspective view of a large two-stroke diesel engine according to an exemplary embodiment; FIG. [Figure 2] FIG. 2 is a perspective view of the large two-stroke engine of FIG. 1, seen from a different angle. [Figure 3] 3 is a diagrammatic representation of the large two-stroke engine of FIGS. 1 and 2, according to an embodiment. [Figure 4] 3 is a diagrammatic representation of the large two-stroke engine of FIGS. 1 and 2 according to another embodiment. [Figure 5] 3 is a diagrammatic representation of the large two-stroke engine of FIGS. 1 and 2 according to yet another embodiment. [Figure 6] 3 is a diagrammatic representation of the large two-stroke engine of FIGS. 1 and 2 according to yet another embodiment. [Figure 7] 7 is a schematic representation of a heat exchanger used in the embodiment of FIGS. 5 and 6. Detailed explanation

[0045] In the following detailed description, internal combustion engines are described with reference to an example crosshead-type large, low-speed, two-stroke, turbocharged internal combustion engine. FIGS. 1-3 illustrate an example of a turbocharged large, low-speed, two-stroke diesel engine. The engine has a crankshaft 8 and a crosshead 9. FIGS. 1 and 2 are schematic views from different angles. FIG. 3 is a schematic representation of the turbocharged large, low-speed, two-stroke diesel engine of FIGS. 1 and 2, along with its intake and exhaust systems, according to one embodiment. In this example, the engine has six in-line cylinders. A turbocharged large, low-speed, two-stroke internal combustion engine may have four to fourteen in-line cylinders. These cylinders have cylinder liners supported by an engine frame 11. Such an engine may be used, for example, as a main engine on 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, in the range of 1,000 to 110,000 kW.

[0046] 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 liners 1. A central exhaust valve 4 is disposed in a cylinder cover 22 above the cylinder liners 1. Scavenging gas is guided from the scavenging air receiver 2 to the scavenging ports 18 of each cylinder liner 1 when the piston is below the scavenging ports 18.

[0047] When the engine is operated as a premixed engine (an engine based on the Otto principle), a carbonaceous gas fuel (e.g., methanol, petroleum gas or LPG, methane, natural gas (LNG), ethane) is introduced through the gas inlet valve 50' under the control of the electronic control unit 100. This occurs during the upward stroke of the piston 10 (from BDC to TDC) before the piston passes the fuel valve (gas inlet valve) 50'. The gaseous or liquid carbonaceous fuel (e.g., fuel oil) is injected into the combustion chamber through the fuel valve 50 at high pressure (preferably 300 bar or more) when the piston 10 is at or near TDC. The gaseous fuel is supplied by the gaseous fuel supply system 30' and introduced into the combustion chamber at a relatively low pressure. This pressure is less than 30 bar, preferably 25 bar, and more preferably less than 20 bar. The fuel-containing stream for injection through the fuel valve 50 is supplied by the fuel system 30. The high pressure for injection through the fuel valve 50 can be generated by the fuel system 30 (common rail) or the fuel valve 50. The fuel introduction valves 50' are preferably arranged at equal intervals around the circumference of the cylinder liner. Preferably, they are arranged near the center of the cylinder liner in the longitudinal direction. The introduction of gas fuel occurs when the compression pressure is relatively low. This is because the introduction occurs when the compression pressure is much lower than the compression pressure when the piston reaches TDC, making it possible to introduce the gas fuel at a relatively low pressure.

[0048] When the engine is operated as a compression ignition engine (diesel principle), there is no gas inlet valve 50' and carbon-containing fuel (gaseous or liquid) is injected at high pressure through fuel valve 50 when piston 10 is at or near TDC.

[0049] The piston 10 in the cylinder liner 1 compresses a mixture of gaseous fuel and scavenging gas (or scavenging gas if operating with only fuel injection at TDC), and ignition is induced at or near TDC by injection of high pressure fuel from a 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 compression, resulting in combustion and the production of exhaust gases including carbon dioxide.

[0050] When the exhaust valve 4 is opened, the combustion gas (exhaust gas) flows into the combustion gas receiver 3 through a combustion gas duct attached to the cylinder 1 and flows out into the first exhaust pipe 19. Nitrous oxide (NO x A selective catalytic reactor 33 is provided for reducing .

[0051] The turbocharging system 5 includes a turbine 6 and a compressor 7. The turbine 6 drives the compressor 7 via a shaft. Outside air is supplied to the compressor 9 through an air intake 12. The compressor 7 sends compressed scavenging air to a scavenging pipe 13 connected to the scavenging air receiver 2. Note that the transmission of energy from the turbine 6 to the compressor 7 does not necessarily have to be via a shaft, and an electrical transmission mechanism or a hydraulic transmission mechanism can also be used. The scavenging air in the scavenging pipe 13 passes through an intercooler 14 to cool the scavenging air.

[0052] Either upstream (as shown) or downstream (not shown) of the intercooler 14, the exhaust gas recirculation pipe 35 is connected to the scavenging pipe 13. At this point, the recirculated exhaust gas is mixed with scavenging air to form scavenging gas. The scavenging gas flows to the scavenging air receiver 2. As will be explained in more detail below, the control unit 100 (electronic control unit) is configured to adjust the ratio of scavenging air to exhaust gas in the scavenging gas.

[0053] The cooled scavenging air or scavenging gas passes through an auxiliary blower 16 driven by an electric motor 17. The auxiliary blower 16 compresses the scavenging air flow when the compressor 7 of the turbocharging system 5 cannot provide enough pressure for the scavenging air receiver 2, i.e. when the engine is at low or partial load. When the engine load is high, the turbocharger compressor 7 can provide sufficiently compressed scavenging air and the auxiliary blower 16 is bypassed by a check valve 15. An engine may be equipped with several turbochargers 5 forming a turbocharging system.

[0054] The control unit 100 (electronic control unit) may be comprised of multiple interconnected electronic units, each consisting of a processor and other hardware for performing the functions of the control unit. The control unit 40 generally controls the operation of the engine, including controlling, for example, gas fuel introduction (amount and timing), liquid fuel injection (amount and timing), exhaust valve 4 opening / closing (timing and lift), and exhaust gas recirculation ratio, as well as the operation of various coolers, pumps, and other devices. The control unit 100 receives various signals from sensors indicating engine operating conditions. These signals may include signals representing engine load, engine speed, blower speed, scavenging air temperature, exhaust gas temperatures at various locations, and exhaust gas temperatures at various locations. They may also include signals representing scavenging system pressure, combustion chamber pressure, exhaust system pressure, and exhaust gas recirculation system pressure. The engine preferably includes a variable timing exhaust valve actuation system that allows individual control of exhaust valve timing for each combustion chamber. The control unit 100 is connected to the fuel valve 50, the liquid fuel inlet 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 generates a signal representative of the crankshaft position. The pressure sensor is preferably located in the cylinder cover 22, or alternatively in the cylinder liner 1, and generates a signal representative of the pressure in the combustion chamber.

[0055] 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.

[0056] The cylinder liner 1 is mounted on a cylinder frame 23, and a cylinder cover 22 is installed on top of the cylinder liner 1. The cylinder liner 1 and the cylinder cover 22 are arranged to prevent gas leakage between them. The piston 10 is configured to reciprocate between bottom dead center (BDC) and top dead center (TDC). These two dead center positions of the piston 10 are separated by 180 degrees in terms of the rotation angle of the crankshaft 8. The cylinder liner 1 has multiple cylinder lubrication holes distributed circumferentially. 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 holes 25. The piston rings (not shown) of the piston 10 then distribute the cylinder lubricating oil over the entire running surface (inner surface) of the cylinder liner. Although not shown, the cylinder liner is provided with a jacket, and jacket cooling water circulates in the space between the jacket and the cylinder liner.

[0057] A plurality of liquid fuel valves 50, preferably three or four per cylinder, are attached to the cylinder cover 22 and connected to a pressurized carbon-containing fuel supply source (not shown). The liquid fuel valves 50 are preferably arranged at equal intervals in the circumferential direction around the exhaust valve 4, particularly around the central outlet (opening) of the cylinder cover 22. The outer shape of the central portion is controlled by the exhaust valve 4. The fuel injection timing and injection amount are controlled by the control unit 100. When the engine is operated in a premixed mode, the fuel valve 50 is used only to inject a small amount of ignition fluid (pilot). When the engine is operated in a compression ignition mode, the liquid fuel valve 50 injects the amount of liquid fuel necessary to operate the engine at the actual engine load. The cylinder cover 22 may be provided with a prechamber (not shown). The tip of the liquid fuel valve 50, typically provided with a nozzle having one or more nozzle holes, is positioned so that pilot oil (ignition fluid) is injected into the prechamber and atomized. The vestibule aids in reliable ignition.

[0058] The fuel inlet valve 50' is mounted on the cylinder liner 1 (or the cylinder cover 22) with its nozzle substantially flush with the inner surface of the cylinder liner 1 and the rear end of the fuel valve 50' protruding from the outer wall of the cylinder liner 1. Typically, one or two, but at most three or four, fuel valves 50' are provided for each cylinder liner 1. These are arranged (preferably at equal intervals) around the circumference of the cylinder liner 1. In this embodiment, the fuel inlet valve 50' is located exactly in the longitudinal center of the cylinder liner 1. The fuel inlet valve 50' is connected to a pressurized supply source 30' of gas fuel (e.g., methanol, LPG, LNG, ethane, or ammonia). That is, the fuel is in a gaseous phase when supplied to the fuel inlet valve 50'. Because the gas fuel is introduced during the stroke of the piston 10 from BDC to TDC, the pressure of the gas fuel supply source only needs to be higher than the pressure existing in the cylinder liner 1. Typically, a pressure of less than 20 bar is sufficient for the gas fuel delivered to the fuel inlet valve 50'. The fuel inlet valve 50' is connected to a control unit 100. The control unit 40 determines the opening and closing timing and the opening time of the fuel inlet valve 50'.

[0059] In some embodiments, the liquid fuel for ignition is heavy fuel oil, marine diesel, heavy fuel oil, ethanol, or dimethyl ether (DME).

[0060] The gas operating mode can be one of several operating modes for the engine. Other modes can include a liquid fuel operating mode in which all of the fuel required for engine operation is supplied in liquid form through the liquid fuel valve 50. In the gas fuel operating mode, the engine is primarily fueled by gas fuel introduced at relatively low pressure during the piston stroke from BDC to TDC. That is, the majority of the energy supplied to the engine is provided by such gas fuel. Meanwhile, liquid fuel is used in smaller amounts compared to the gas fuel, contributing 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 functions as an ignition fluid.

[0061] In this way, the engine of this 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 solely on gas fuel.

[0062] In this embodiment, the engine is shown as a premixed engine operating according to the Otto principle, but there are also embodiments in which the engine is a compression ignition engine (operating according to the Diesel principle), in which case a carbon-based fuel (gaseous or liquid) is injected at high pressure when the piston 10 is at or near TDC.

[0063] The engine is operated by supplying a carbon-based fuel (liquid and / or gaseous fuel) to a combustion chamber and combusting the carbon-based fuel therein, thereby generating an exhaust stream comprising carbon dioxide. During engine operation, a portion of the exhaust gas is recirculated through an exhaust gas recirculation system located on the high-pressure side of the turbocharging system 5. The proportion of the recirculated exhaust gas is variable. In some embodiments, a first portion of the exhaust stream is recirculated and a second portion of the exhaust stream is discharged to the atmosphere as exhaust gas. A pressurized scavenging gas comprising the exhaust gas is supplied to the combustion chamber. In some embodiments, the pressurized scavenging gas comprises at least 40% by mass of the recirculated exhaust gas, and preferably 50% by mass or more of the recirculated exhaust gas. In some embodiments, the recirculated gas is derived directly from the combustion gas in the combustion chamber.

[0064] Downstream of the turbocharger turbine 6, the exhaust gases enter a second exhaust pipe 28, which directs the exhaust gases to a boiler 20 (also called an economizer). The boiler 20 is configured to generate steam, which can be used for various purposes, for example on board a ship on which the engine is installed.

[0065] The second exhaust pipe 28 continues downstream of the boiler 20 and connects to an inlet at the bottom of an absorber 42. The absorber 42 is preferably an absorber tower, such as a packed absorber tower. The exhaust gases pass through the absorber tower 42 and exit at an outlet at the top of the absorber tower 42.

[0066] Absorber 42 is part of a system that uses a solvent to chemically absorb carbon dioxide. An example of a suitable solvent is an amine solution. The amine solution may include primary, secondary, and / or tertiary amines. Another example of a suitable solution is a NaOH / KOH solution, preferably an amine-NaOH / KOH aqueous solution.

[0067] Carbon dioxide is removed from the exhaust gas by a packed absorber 42. This reaction is exothermic, increasing the solvent temperature along the absorber 42. By way of example, the carbon dioxide concentration in engine exhaust gas is 4-5% by volume without exhaust gas recirculation and 9-10% by volume with exhaust gas recirculation. The exhaust gas is introduced into the absorber 42 countercurrently to the solvent entering the top of the absorber 42. This solvent is referred to as lean CO2 or CO2-free solvent. This CO2-free solvent is supplied from the desorber 66 at approximately 35°C to 55°C and atmospheric pressure. The absorber 42 has a packed-bed water wash at the top, which condenses and solubilizes the majority of the volatile amine sorbent that has escaped into the exhaust gas. The absorber 42 can be up to 50 meters tall. After the carbon dioxide is absorbed in the absorber 42, a carbon dioxide-rich solvent stream from the bottom of the absorber 42 is fed by a pump 44 to a cross heat exchanger 60, where it is heat exchanged with a carbon dioxide-lean solvent stream before being introduced into a desorber 66 and reboiler 62 assembly, where it is heated to release carbon dioxide from the solvent. The reboiler is sometimes referred to in the art as a "regenerator." The desorption temperature varies between 120°C and 150°C, and the operating pressure can reach up to 5 bar.

[0068] A water-saturated carbon dioxide stream is discharged from the top of desorber 66. It is cooled in heat exchanger 68 to condense most of the water. The water is separated in knockout drum 69 and returned to desorber 66. The carbon dioxide stream from knockout drum 69 is compressed / liquefied in liquefaction unit 70 and temporarily stored in storage tank 85, which may be a cryogenic storage tank. From temporary storage tank 85, the liquefied carbon dioxide can be transported to a final storage location or to a utility facility (not shown). If the engine is on board a vessel, temporary storage tank 85 is located on board the vessel and is emptied when the vessel is in port with facilities to receive liquefied carbon dioxide.

[0069] The regeneration step of the amine solution does not remove all of the carbon dioxide in the solution. The regenerated carbon dioxide-lean solvent is recycled to absorber 42 at a carbon dioxide-lean load by the action of pump 64. Before reaching absorber 42, the carbon dioxide-rich solvent exchanges heat with the carbon dioxide-lean solvent in cross heat exchanger 60 and heat exchanger 67.

[0070] The carbon dioxide loading of the solvent after absorbing carbon dioxide through the absorber is called the carbon dioxide rich solvent. The difference between the lean and rich solvent is the amount of carbon dioxide recovered from the exhaust gas.

[0071] The carbon dioxide concentration in the exhaust gas exiting the absorber 42 is up to 10 times lower than the carbon dioxide concentration in the exhaust gas entering the absorber 42 .

[0072] Some of the solvent amine may still be present in the exhaust gas exiting absorber 42. This amine is removed by amine scrubber 41 located in exhaust line 49 downstream of absorber 42.

[0073] The engine is equipped with an exhaust gas recirculation system having an exhaust gas recirculation pipe 35 connecting the first exhaust pipe 19 to the scavenge air pipe 13. That is, exhaust gas recirculation occurs on the high-pressure side of the turbocharging system 5. Preferably, the exhaust gas recirculation pipe 35 connects to the first exhaust pipe 19 upstream of the selective catalytic reactor 33. Preferably, the exhaust gas recirculation pipe 35 connects to the scavenge air pipe 13 upstream of the scavenge air cooler 14. However, embodiments can also exist in which the exhaust gas recirculation pipe 35 connects to the scavenge air pipe 13 downstream of the scavenge air cooler 14. The exhaust gas recirculation pipe 35 includes a blower 34 for forcing exhaust gas from the exhaust pipe into the scavenge air pipe. This is because the pressure in the scavenge air pipe 13 during engine operation is typically higher than the pressure in the first exhaust pipe 19. In the illustrated embodiment, the blower 34 is driven by an electric motor. In other embodiments, the blower can be driven by another rotary power source. In the illustrated embodiment, the blower 34 is located downstream of the wet scrubber 36 and downstream of the water mist catcher 38. However, the location of the blower 34 could be upstream or downstream of other elements of the exhaust gas recirculation circuit 35. The primary purpose of the exhaust gas recirculation scrubber 36 is to remove impurities (soot).

[0074] The water mist catcher 38 removes water particles from the recirculated exhaust gases and prevents them from entering the combustion chamber.

[0075] The reboiler 62 is disposed within the exhaust gas recirculation system and functions as an exhaust gas recirculation cooler. The reboiler 62 is disposed within the exhaust gas recirculation system, preferably upstream of the exhaust gas recirculation scrubber / injector 36. In the reboiler 62, the solvent exchanges heat with the recirculated exhaust gas, heating the solvent and cooling the recirculated exhaust gas. The reboiler 62 is configured as a heat exchanger through which the recirculated exhaust gas flows and the solvent flows, to exchange heat between the recirculated exhaust gas and the solvent.

[0076] The control unit 100 is configured to control the speed of the exhaust gas recirculation system blower 34 to adjust the proportion of recirculated exhaust gas in the pressurized scavenging gas to a proportion of preferably at least 40% by mass. This is to increase the carbon dioxide concentration in the exhaust gas, thereby increasing the effectiveness of the carbon dioxide absorption system. The exhaust gas recirculation rate can also be controlled by a valve (not shown) controlled by the control unit 100. Thus, the control unit 100 is configured to operate the engine with a proportion of recirculated exhaust gas in the pressurized scavenging gas of 40% or more, 50% or more, 60% or more, etc., depending on the operating conditions. Generally, the control unit 100 is configured to operate with the highest possible proportion of recirculated exhaust / combustion gas. "Highest possible" means the highest proportion that does not cause unacceptable adverse effects, such as a reduction in the quality of the combustion process, a decrease in the reliability of the combustion process, or an unacceptable increase in the engine heat load. The recirculated exhaust gas enters the reboiler 62 at a temperature of approximately 260-400°C. The solvent flow rate through the reboiler 62 can be adjusted to achieve the desired solvent temperature. Vent recirculation increases the carbon dioxide concentration of the exhaust gas fed to absorber 42, thereby reducing the energy consumption of the desorber 66 and reboiler 62 assembly. Increasing the exhaust recirculation ratio also reduces the size of the exhaust stream to absorber 42, allowing a smaller diameter absorber tower to be used when exhaust recirculation is used or when the exhaust recirculation ratio is increased.

[0077] Figure 4 shows another embodiment of the engine. In this embodiment, components and features similar to those already described or illustrated are designated by the same reference numerals previously used. The engine and its operation in this embodiment are substantially similar to the previous embodiment, and therefore only the differences from the previous embodiment will be described in detail.

[0078] In this embodiment, the reboiler 62 receives heat from a steam system associated with the engine. The steam may be generated in a heat exchanger 32 disposed in the exhaust gas recirculation system for cooling the recirculated exhaust gas. The absorber 42 in this embodiment is disposed in the exhaust gas recirculation pipe 35, preferably located downstream of the water mist catcher 38 and preferably upstream of the EGR blower 34.

[0079] That is, absorber 42 is positioned such that the recirculated exhaust stream passes through absorber 42 to separate the carbon dioxide from the exhaust stream by chemical absorption in a solvent. In another version of this embodiment, not shown, absorber 42 is positioned such that the exhaust stream upstream of the turbine of turbocharger 6 passes through absorber 42 to separate the carbon dioxide from the exhaust stream by chemical absorption in a solvent.

[0080] Figure 5 shows another embodiment of the engine. In this embodiment, components and features similar to those already described or illustrated are designated by the same reference numerals as previously used. The engine and its operation in this embodiment are substantially similar to the previous embodiment, and therefore only the differences from the previous embodiment will be described in detail.

[0081] In this embodiment, the absorber 42 is arranged similarly to the embodiment of Figure 4, i.e., the absorber 42 is arranged so that the recirculated exhaust stream passes through it to separate carbon dioxide from the exhaust stream by chemical absorption into a solvent. The reboiler 62 is also arranged similarly to the embodiment of Figure 3, i.e., the reboiler 62 is located within the exhaust gas recirculation system and configured as a heat exchanger with the recirculated exhaust gas flowing in one direction and the solvent flowing in the other direction to exchange heat between the recirculated exhaust gas and the solvent, thereby combining the advantages of the two embodiments.

[0082] To achieve this, the exhaust gas recirculation system is branched into a first string 35 and a second string 92. The first string 35 connects to the charge air system downstream of the compressor 7 of the turbocharging system 5, and the second string 92 connects to the exhaust system upstream of the turbine 6 of the turbocharging system 5. An absorber 42 is located in the exhaust gas recirculation system upstream of the point where the first string 35 and the second string 92 branch off. The first string 35 preferably includes a first blower 34, and the second string 92 preferably includes a second blower 93. A reboiler 62 is also preferably located upstream of the branching point.

[0083] The second string 92 passes through a heat exchanger, preferably integrated into the reboiler 62, for heat exchange between the recirculated exhaust gases in the second string 92 and the recirculated exhaust gases in the exhaust gas recirculation system upstream of the split point.

[0084] The first string 35 includes a first blower 34, and the second string 92 includes a second blower 93. The control unit 100 controls the rotation speeds of the first blower 34 and the second blower 93 to control the amount of exhaust gas flowing through the first string and the second string.

[0085] A first control valve 55 upstream of the branch point in the exhaust gas recirculation system and a second control valve 56 in the first exhaust pipe 19 are used to regulate the flow through their respective pipes, preferably under the command of an electronic control unit 100.

[0086] For the highest CO2 removal rate, all (or nearly all) of the exhaust gas is directed through the first control valve 55 (i.e., the first control valve is open and the second control valve is closed or nearly closed). Thus, the entire exhaust flow passes through the reboiler 62 and the absorber 42. 40-50% of the exhaust gas is sent to the scavenge air receiver 2 by the EGR blower 34. The remaining gas is forced through the reboiler 62 by a dedicated exhaust gas blower 93 via a line 92. This allows the remaining gas to exchange heat (be heated) with the exhaust gas flowing through the reboiler 62 as part of the exhaust gas recirculation line 35. The remaining gas is then sent to the inlet side of the turbine 6 of the turbocharging system 5.

[0087] Figure 6 shows another embodiment of the engine. In this embodiment, components and features similar to those already described or illustrated are designated by the same reference numerals previously used. The engine and its operation in this embodiment are substantially similar to the previous embodiment, and therefore only the differences from the previous embodiment will be described in detail.

[0088] In this embodiment, the absorber 42 is arranged similarly to the embodiment of Figure 4, i.e., the absorber 42 is arranged so that the recirculated exhaust stream passes through it to separate carbon dioxide from the exhaust stream by chemical absorption into a solvent. The reboiler 62 is also arranged similarly to the embodiment of Figure 3, i.e., the reboiler 62 is located within the exhaust gas recirculation system and configured as a heat exchanger with the recirculated exhaust gas flowing in one direction and the solvent flowing in the other direction to exchange heat between the recirculated exhaust gas and the solvent, thereby combining the advantages of the two embodiments.

[0089] To achieve this, the exhaust gas recirculation system is branched into a first string 35 and a second string. The first string connects to the charge air system downstream of the compressor 7 of the turbocharging system 5, and the second string connects to the exhaust system upstream of the turbine 6 of the turbocharging system 5. An absorber 42 is arranged in the second string, and a reboiler 62 is preferably arranged upstream of the point where the first string 35 and the second string branch off.

[0090] The first string 35 includes a first blower 34, and the second string includes a second blower 93. The control unit 100 controls the rotation speeds of the first blower 34 and the second blower 93 to control the amount of exhaust gas flowing through the first string and the second string.

[0091] The second string 92 passes through a heat exchanger, which is integrated into the reboiler 62, for heat exchange between the recirculated exhaust gases in the second string and the recirculated exhaust gases in the exhaust gas recirculation system upstream of the split point.

[0092] A first control valve 55 upstream of the branch point in the exhaust gas recirculation system and a second control valve 56 in the first exhaust pipe 19 are used to regulate the flow through their respective pipes, preferably under the command of an electronic control unit 100.

[0093] All (or almost all) of the exhaust gas is directed through the first control valve 55 and the reboiler 62. 40-50% of the exhaust gas is sent to the scavenge air receiver 2 by the EGR blower 34. The remaining gas is directed by a dedicated exhaust gas blower 93 through a pipe 92 to the absorber 42 and then to the reboiler 62. This causes the remaining gas to exchange heat with the exhaust gas flowing through the reboiler 62 as part of the exhaust gas recirculation pipe 35 (to be heated). The remaining gas is then sent to the inlet side of the turbine 6 of the turbocharging system 5.

[0094] Figure 7 is a schematic representation of the heat exchanger formed by reboiler 62 and used in the embodiments of Figures 5 and 6. Heat exchanger / reboiler 62 has an inlet and an outlet connected to exhaust gas recirculation line 35, an inlet and an outlet for solvent connected to solvent line 83, and an inlet and an outlet for exhaust gas in line 92, thereby allowing heat exchange between the exhaust gas in exhaust gas recirculation line 35 and the solvent, and between the exhaust gas in line 92 and the exhaust gas in exhaust gas recirculation line 35.

[0095] Various aspects and implementations of the invention have been described with several examples. The above embodiments can be combined in various ways. Furthermore, upon studying the specification, drawings, and claims of this application, those skilled in the art will understand and be able to embody many variations in addition to the described examples in implementing the claimed invention. The words "comprise," "have," and "include" in the claims do not exclude the presence of unrecited elements or steps. A claim without explicitly stating a plurality of elements does not exclude the presence of a plurality of elements. The functions of several elements recited in the claims may be performed by a single processor, controller, or other unit. The fact that several items are recited in separate dependent claims does not exclude them from being combined, and may benefit from being combined. Reference signs used in the claims should not be construed as limiting the scope of the invention.

Claims

1. A crosshead type large two-stroke turbocharged uniflow scavenging internal combustion engine, at least one combustion chamber defined by a cylinder liner, a piston configured to reciprocate within the cylinder liner, and a cylinder cover; a scavenging port disposed in the cylinder liner for introducing scavenging gas into the at least one combustion chamber; a fuel system configured to supply a carbon-based fuel to the at least one combustion chamber; wherein the at least one combustion chamber is configured to combust a carbon-based fuel to produce exhaust gases comprising carbon dioxide, and the engine further comprises: an exhaust outlet disposed in the cylinder cover and controlled by an exhaust valve; the at least one combustion chamber is connected to a scavenging air receiver through the scavenging port and to an exhaust gas receiver through the exhaust outlet, and the engine further comprises: an exhaust system having a turbine driven by the exhaust flow, the turbine being of a turbocharging system; an air intake system including a compressor of the turbocharging system configured to supply pressurized scavenging air to the scavenging air receiver; an exhaust gas recirculation system configured to recirculate a portion of the exhaust gas flow discharged from the at least one combustion chamber from upstream of the turbine of the turbocharging system to the scavenging air receiver, the exhaust gas recirculation system having a first blower for assisting the flow of exhaust gas to the scavenging air receiver; an absorber for absorbing carbon dioxide into a solvent; a desorber and reboiler assembly for desorbing carbon dioxide from the solvent; Equipped with the absorber has a solvent inlet for receiving carbon dioxide-lean solvent from the desorber and a solvent outlet for supplying carbon dioxide-rich solvent to the desorber; the absorber is configured to separate carbon dioxide from the exhaust gas by chemical absorption in the solvent for at least a portion of the exhaust stream or recirculated exhaust stream passing through the absorber; the assembly having an inlet for receiving carbon dioxide-rich solvent from the absorber and an outlet for supplying carbon dioxide-lean solvent to the absorber; the assembly is configured to heat the solvent to release carbon dioxide from the solvent; The reboiler is - configured as a heat exchanger disposed within the exhaust gas recirculation system and through which the recirculated exhaust gas flows and the solvent flows, for exchanging heat between the recirculated exhaust gas and the solvent; and / or a heat exchanger disposed in the exhaust system upstream of the turbine of the turbocharging system, the heat exchanger configured with recirculated exhaust gases flowing through one side and the solvent flowing through the other side for exchanging heat between the exhaust gases and the solvent; institution.

2. 2. The engine of claim 1, wherein the reboiler is configured to exchange heat between exhaust gases in the exhaust gas recirculation system and the solvent, thereby cooling the exhaust gases in the exhaust gas recirculation system and heating the solvent.

3. 3. An engine according to claim 1 or 2, wherein the exhaust gas recirculation system comprises a wet scrubber.

4. The engine of claim 3 , wherein the wet scrubber is disposed within the reboiler in the exhaust gas recirculation system.

5. 2. The engine of claim 1, comprising a control unit configured to adjust the mass fraction of recirculated exhaust gas in the scavenging gas to at least 40% or at least 55%.

6. 6. The engine of claim 5, wherein the controller is configured to control a speed of the first blower to adjust the proportion of exhaust gases that are recirculated, and / or the controller is configured to control a position of a control valve in the exhaust system to adjust the proportion of exhaust gases that are recirculated.

7. 1. A method of operating a large two-stroke turbocharged uniflow scavenged internal combustion engine having a plurality of combustion chambers and a turbocharging system, comprising: supplying a carbon-based fuel to the combustion chamber; burning a carbon-based fuel in a combustion chamber to produce an exhaust stream comprising carbon dioxide; recirculating a first portion of the exhaust stream from a high pressure side of the turbocharging system to a cylinder and exhausting a second portion of the exhaust stream; supplying a pressurized scavenging air flow including recirculated exhaust gas to the combustion chamber; chemically absorbing carbon dioxide from the first and / or second portions of the vent stream into a solvent by supplying a carbon dioxide-lean solvent stream to an absorber and discharging a carbon dioxide-rich solvent stream from the absorber to a desorber and reboiler assembly; Including, regenerating the carbon-rich solvent in the assembly by heating at least the first portion of the exhaust stream by passing it through the assembly, thereby heating the solvent and cooling the first portion of the exhaust stream by heat exchange between the first portion of the exhaust stream and the solvent; and / or regenerating the carbon-rich solvent in the assembly by heating at least the second portion of the exhaust stream through the assembly on the high pressure side of the turbocharging system, thereby heating the solvent and cooling the first portion of the exhaust stream by heat exchange between the first portion of the exhaust stream and the solvent; A method comprising:

8. The method of claim 7, comprising recirculating at least 40% by mass of the exhaust stream, or recirculating at least 50% by mass of the exhaust stream.

9. 9. The method of claim 7 or 8, comprising controlling the speed of a first blower of the exhaust gas recirculation system to adjust the proportion of recirculated exhaust gas in the pressurized scavenging gas, and / or controlling the position of a control valve in the exhaust system to control the proportion of recirculated exhaust gas.

10. 9. A method according to claim 7 or 8, comprising feeding the gas stream comprising carbon dioxide and water vapour or steam generated in the desorber to a separator which separates the carbon dioxide and water vapour or steam.

11. 11. The method of claim 10, wherein the separator comprises a knock-out drum for obtaining a gas stream comprising primarily carbon dioxide and a liquid stream comprising primarily water.

12. 11. The method of claim 10, comprising supplying a gas stream comprising primarily carbon dioxide to a liquefaction unit and liquefying the gas stream comprising primarily carbon dioxide to obtain a liquefied carbon dioxide stream.

13. A crosshead type large two-stroke turbocharged uniflow scavenging internal combustion engine, at least one combustion chamber defined by a cylinder liner, a piston configured to reciprocate within the cylinder liner, and a cylinder cover; a scavenging port disposed in the cylinder liner for introducing scavenging gas into the at least one combustion chamber; a fuel system configured to supply a carbon-based fuel to the at least one combustion chamber; wherein the at least one combustion chamber is configured to combust a carbon-based fuel to produce exhaust gases comprising carbon dioxide, and the engine further comprises: an exhaust outlet disposed in the cylinder cover and controlled by an exhaust valve; the at least one combustion chamber is connected to a scavenging air receiver through the scavenging port and to an exhaust gas receiver through the exhaust outlet, and the engine further comprises: an exhaust system having a turbine driven by the exhaust flow, the turbine being of a turbocharging system; an air intake system including a compressor of the turbocharging system configured to supply pressurized scavenging air to the scavenging air receiver; an exhaust gas recirculation system configured to recirculate a portion of exhaust gases discharged from the at least one combustion chamber from upstream of the turbine of the turbocharging system to the scavenging air receiver, the exhaust gas recirculation system having a first blower for assisting exhaust gas flow to the scavenging air receiver; an absorber for absorbing carbon dioxide into a solvent; a desorber and reboiler assembly for desorbing carbon dioxide from the solvent; Equipped with the absorber has a solvent inlet for receiving carbon dioxide-lean solvent from the desorber and a solvent outlet for supplying carbon dioxide-rich solvent to the desorber; the assembly having an inlet for receiving carbon dioxide-rich solvent from the absorber and an outlet for supplying carbon dioxide-lean solvent to the absorber; the assembly is configured to heat the solvent to release carbon dioxide from the solvent; The absorber comprises: at least a portion of the recirculated exhaust gas stream is configured to pass through the absorber; and / or at least a portion of the exhaust flow upstream of the turbine of the turbocharging system is configured to pass through the absorber; institution.

14. 14. The engine of claim 13, wherein the absorber is positioned within the exhaust gas recirculation system such that all of the recirculated exhaust gas passes through the absorber.

15. 14. The engine of claim 13, wherein the reboiler is disposed within the exhaust gas recirculation system and configured as a heat exchanger through which the recirculated exhaust gas flows and the solvent flows to exchange heat between the recirculated exhaust gas and the solvent.

16. 16. An engine according to any one of claims 13 to 15, wherein the exhaust gas recirculation system branches into a first string and a second string, the first string connecting to the air charge system at a location downstream of the compressor of the turbocharging system and the second string connecting to the exhaust system upstream of the turbine of the turbocharging system, the absorber being located in the second string, the absorber being located in the exhaust gas recirculation system upstream of the location where the first string and the second string branch off.

17. 17. The engine of claim 16, wherein said first string comprises a first blower and said second string comprises a second blower.

18. 17. The engine of claim 16, wherein the reboiler is located upstream of a location where the first string and the second string diverge.

19. 17. The engine of claim 16, wherein the second string passes through a heat exchanger for heat exchange between recirculated exhaust gases in the second string and recirculated exhaust gases in the exhaust gas recirculation system upstream of the branching location.

20. 20. An engine as set forth in claim 19, wherein said heat exchanger is an integral element of said reboiler.

21. 14. The engine of claim 13, wherein the exhaust gas recirculation system branches into a first string and a second string, the first string connecting to the charge air system at a location downstream of the compressor of the turbocharging system, and the second string connecting to the exhaust system upstream of the turbine of the turbocharging system, and the absorber being disposed in the second string.

22. 22. The engine of claim 21, wherein the reboiler is located upstream of a location where the first string and the second string diverge.

23. 22. The engine of claim 21, wherein the first string comprises a first blower and the second string comprises a second blower, and the engine comprises a controller that controls the rotational speeds of the first blower and the second blower to control the amount of exhaust gas flowing through the first string and the second string.

24. 23. An engine according to claim 21 or 22, wherein the second string passes through a heat exchanger for heat exchange between recirculated exhaust gases in the second string and recirculated exhaust gases in the exhaust gas recirculation system upstream of the branching location.

25. 25. An engine as set forth in claim 24 wherein said heat exchanger is an integral element of said reboiler.

26. 1. A method of operating a large two-stroke turbocharged uniflow scavenged internal combustion engine having a plurality of combustion chambers and a turbocharging system, comprising: supplying a carbon-based fuel to the combustion chamber; burning a carbon-based fuel in a combustion chamber to produce an exhaust stream comprising carbon dioxide; recirculating a first portion of the exhaust flow from a cylinder and exhausting a second portion of the exhaust flow from the cylinder at a high pressure side of the turbocharging system; supplying a pressurized scavenging air flow to the combustion chamber, the pressurized scavenging air flow including the first portion of the exhaust flow from the cylinder; chemically absorbing carbon dioxide into a solvent from the first portion of the exhaust stream from the cylinder by feeding a carbon dioxide-lean solvent stream to an absorber and discharging a carbon dioxide-rich solvent stream from the absorber to a desorber and reboiler assembly, and / or chemically absorbing carbon dioxide into a solvent from the second portion of the exhaust stream from the cylinder only on the high pressure side of the turbocharging system; Regenerating the carbon-rich solvent in the assembly; A method comprising:

27. 27. The method of claim 26, wherein the absorber is configured such that at least a portion of the first portion of the exhaust stream passes through the absorber and / or such that at least a portion of the second portion of the exhaust stream passes through the absorber.

28. 27. The method of claim 26, wherein the first portion of the exhaust stream is passed through the assembly, whereby heat exchange between the first portion of the exhaust stream and the solvent heats the solvent and cools the first portion of the exhaust stream.

29. 29. The method of any of claims 26 to 28, comprising recirculating at least 40 mass% of the exhaust stream, or recirculating at least 50 mass% of the exhaust stream.

30. 30. The method of claim 29, comprising controlling the speed of a first blower in the exhaust gas recirculation system to adjust the proportion of recirculated exhaust gas in the pressurized scavenging gas, and / or controlling the position of a control valve in the exhaust system to control the proportion of exhaust gas that is recirculated.

31. 29. A method according to any one of claims 26 to 28, comprising feeding the gas stream comprising carbon dioxide and water vapour or steam generated in the desorber to a separator for separating the carbon dioxide and water vapour or steam, the separator being for obtaining a gas stream comprising mainly carbon dioxide and a liquid stream comprising mainly water.

32. 32. The method of claim 31 , wherein the separator comprises a knockout drum.

33. 32. The method of claim 31 , comprising supplying a gas stream comprising primarily carbon dioxide to a liquefaction unit and liquefying the gas stream comprising primarily carbon dioxide to obtain a liquefied carbon dioxide stream.

34. 34. The method of claim 33, comprising directing the liquefied carbon dioxide stream to a liquefied carbon dioxide storage device.

Images