Large two-stroke uniflow scavenge-supercharged closed-cycle oxi-fuel internal combustion engine

Abstract

To provide a large two-stroke uniflow scavenged closed-cycle oxy-fuel internal combustion engine with a CO2 recovery system.SOLUTION: A large two-stroke uniflow scavenged internal combustion engine comprises: a plurality of cylinders 1; an intake system having a scavenging receiver 2 connected to the cylinders for supplying scavenging gas to combustion chambers of the cylinders; and an exhaust system having an exhaust receiver 3 for receiving an exhaust gas flow generated by combustion of a carbon-based fuel. The engine is a closed cycle oxy-fuel engine and further comprises: a recirculation conduit 5 connecting the exhaust receiver to the scavenging receiver; a blower 7 in the recirculation conduit; an oxygen supply system 12; and a separation and carbon dioxide liquefaction system 60, in which a portion of the exhaust gas flow produced in the combustion chambers is diverted to the separation and carbon dioxide liquefaction system. The separation and carbon dioxide liquefaction system separates oxygen from the diverted exhaust gas flow with the aid of liquefaction of carbon dioxide from the diverted exhaust gas flow.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The subject matter disclosed herein (hereinafter referred to as the present disclosure) relates to a large two-stroke internal combustion engine, and in particular to a large two-stroke uniflow scavenging closed cycle oxy-fuel internal combustion engine with a CO2 capture system.

[0002] Large two-stroke uniflow scavenged turbocharged internal combustion crosshead engines are typically used in the propulsion systems of large ships, and as prime movers in power plants. Their size, weight, and power output set them apart from other combustion engines, placing this type of compression ignition engine in a unique category.

[0003] Large two-stroke uniflow scavenged turbocharged internal combustion crosshead engines have been mainly operated with hydrocarbon fuels, such as fuel oils, like diesel oil, or fuel gases, like natural gas or petroleum gas. Combustion of hydrocarbon fuels involves the production of greenhouse gases, such as carbon dioxide (CO2), which can contribute to air pollution and climate change. Unlike impurities in petroleum fuels that result in by-product emissions, the production of CO2 is inevitable in the combustion of hydrocarbons. The energy density of the fuel and the CO2 emissions depend on the length of the hydrocarbon chain and the complexity of the hydrocarbon molecule. Therefore, gaseous hydrocarbon fuels have lower CO2 emissions than liquid hydrocarbon fuels. However, gaseous hydrocarbon fuels are difficult and expensive to handle and store. To reduce CO2 emissions, large two-stroke uniflow scavenged turbocharged compression ignition internal combustion crosshead engines running on hydrocarbon fuels, with CO2 capture and storage systems, have been proposed.

[0004] One of the known CO2 capture and storage technologies is the installation of amine-based scrubbers on large two-stroke uniflow scavenged turbocharged internal combustion crosshead engines. This is currently considered the most mature carbon capture solution and is expected to be installed on ships as pilot and demonstration plants in the coming years. This technology has some disadvantages: Amines are sensitive to SOx, NOx, O2, particulate matter and temperatures above about 150°C, so they degrade over time; Amines form harmful emissions that must be controlled; and the energy consumed in the reboiler is huge, equivalent to 60% of the engine shaft power.

[0005] Another CO2 capture and storage technology is a large two-stroke uniflow scavenging turbocharged internal combustion crosshead engine fitted with EGR and upstream air separation (N2 and O2) and downstream CO2 liquefaction. The upstream air separation is performed by a membrane. This technology has the following disadvantages: Air separation membranes are large, expensive, have high pressure drop and are prone to breakage. Initially, this technology was tested at land-based power plants (to avoid NOx formation) but was not successful. Furthermore, a significant amount of O2 can be wasted when O2 and CO2 are separated in the exhaust gas.

[0006] Another known technology is upstream pyrolysis / reforming of the fuel to a mixture of H2 and CO2. H2 and CO2 are separated by a membrane, H2 is burned in a hydrogen engine, and CO2 is liquefied. This technology has the following disadvantages: A catalyst is required for pyrolysis / reforming. Catalysts reduce the operating temperature and improve the selectivity of the reaction. Catalysts are expensive, sensitive to impurities in the fuel, and have a limited lifespan. Also, the products from the decomposition-reforming process may contain species other than the desired CO2+H2 (CO, CH4, etc.). The energy consumption for pyrolysis / reforming is about 40% of the engine shaft power. Furthermore, this technology requires a membrane to efficiently separate H2 and CO2. Little information has been found on CO2 / H2-membrane separation, but cost, size, and lifespan must be considered. Finally, this technology requires hydrogen as fuel. Development of a large two-stroke uniflow scavenged turbocharged internal combustion crosshead engine is required.

[0007] Yet another technology is a large two-stroke uniflow scavenging turbocharged internal combustion crosshead engine running on ammonia fuel synthesized from hydrogen and nitrogen. This technology is currently under development. This technology has the following disadvantages: Ammonia is highly toxic and corrosive to certain materials. Ammonia engines will require an SCR catalyst and possibly also an N2O catalyst. Ammonia ICEs are carbon free, but considering N2O emissions, the GWP reduction compared to diesel is expected to be around 90%. The combustion properties of ammonia are not suitable for compression ignition (diesel) engines. Abstract

[0008] It is an object to provide a large two-stroke uniflow scavenged turbocharged internal combustion crosshead engine which solves or at least mitigates the above mentioned problems. Another object is to provide a method for eliminating or at least reducing gaseous CO2 emissions from a large two-stroke uniflow scavenged turbocharged internal combustion crosshead engine.

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

[0010] According to the first aspect, there is provided a large two-stroke uniflow scavenging internal combustion engine as follows. a cylinder having a cylinder liner and a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder; a combustion chamber defined within the cylinder liner between the reciprocating piston and the cylinder cover; a scavenging port disposed in the cylinder liner for introducing scavenging gas into the combustion chamber; an exhaust outlet disposed in the cylinder cover and controlled by an exhaust valve; an intake system having a scavenging receiver connected to the cylinder for supplying scavenging gas to the combustion chamber of the cylinder; a fuel system configured to supply a carbon-based fuel to the combustion chamber; an exhaust system coupled to the combustion chamber via the exhaust valve and having an exhaust receiver configured to receive an exhaust gas stream generated by combustion of the carbon-based fuel in the combustion chamber; the engine being a closed cycle oxy-fuel engine; a recirculation conduit connecting said exhaust air receiver to said scavenge air receiver; a blower disposed within the recirculation conduit for pressurizing exhaust gas from the exhaust receiver and for delivering the exhaust gas to the scavenge receiver; an oxygen supply system configured to supply oxygen to the inlet system; · Separation and carbon dioxide liquefaction system; a portion of the exhaust gas stream produced in the combustion chamber is diverted to the separation and carbon dioxide liquefaction system, the separation and carbon dioxide liquefaction system separating oxygen and carbon dioxide from the diverted exhaust gas stream while assisting in liquefying carbon dioxide from the diverted exhaust gas stream, the engine further comprising: a bypass conduit for bypassing the portion diverted from the exhaust gas stream, the bypass conduit being coupled to the recirculation conduit and including a diversion compressor and one or more coolers.

[0011] This large two-stroke uniflow scavenging internal combustion engine has no gas emissions. The engine also consumes less energy for oxygen separation and carbon dioxide liquefaction compared to known technologies. The efficient separation of oxygen and carbon dioxide minimizes oxygen consumption. The engine is compatible with a wide range of fuels and is compatible with a wide range of retrofit solutions. It does not require rare or expensive earth metals in the catalysts and gas separation membranes used in known carbon dioxide capture technologies. Another advantage of this engine is that the oxygen concentration in the scavenging air can be freely set. Furthermore, the Specific Fuel Oil Consumption (SFOC) is reduced, since there is no need to consider NOx formation. This means that the engine can operate at higher combustion temperatures and pressures, which improves fuel efficiency.

[0012] In one example implementation of the first approach, the bypass conduit is coupled to the recirculation circuit at a location downstream of the first cooler, preferably upstream of the blower.

[0013] In one example implementation of the first approach, the one or more coolers are located downstream of the split-flow compressor, and the bypass conduit preferably leads to a separation and liquefaction vessel.

[0014] In one example implementation of the first approach, the separation and carbon dioxide liquefaction system includes a compressor to pressurize the diverted exhaust gas stream to a target pressure and one or more heat exchangers to cool the diverted exhaust gas stream to a target temperature, the combination of desired pressure and desired temperature causing liquefaction of carbon dioxide in vapor, thereby separating oxygen in the diverted exhaust gas stream in a separation vessel, the target pressure preferably being at least 7 bar and the target temperature preferably being less than -50°C.

[0015] In one example implementation of the first aspect, the oxygen supply system includes a liquid oxygen tank.

[0016] In one example implementation of the first approach, the carbon-based fuel is a hydrocarbon-based fuel, water is generated by combustion of the hydrocarbon-based fuel in the combustion chamber, and the engine is equipped with a water separation system configured to separate water from the exhaust gas stream.

[0017] In one example implementation of the first aspect, the engine includes a first cooler in the recirculation line for cooling the exhaust gas, the first cooler being positioned upstream of the blower.

[0018] In one example implementation of the first aspect, the first cooler is configured to separate water from exhaust gas.

[0019] In one example implementation of the first aspect, the combustion chamber is configured to combust a carbon-based fuel with oxygen, thereby producing an exhaust gas stream that includes carbon dioxide.

[0020] In one example implementation of the first approach, the mole fraction of carbon dioxide in the scavenging gas supplied to the combustion chamber is greater than 0.70 mol / mol.

[0021] In one example implementation of the first approach, the mole fraction of nitrogen in the scavenging gas supplied to the combustion chamber is less than 0.05 mol / mol.

[0022] In one example implementation of the first approach, the mole fraction of oxygen in the scavenging gas supplied to the combustion chamber is greater than 0.17 mol / mol.

[0023] In one example of an implementation form of the first approach, at least one of the coolers in the bypass conduit is a heat exchanger that exchanges heat between the diverted exhaust gas and liquid oxygen supplied from the liquid oxygen tank to the scavenging air receiver.

[0024] According to the second aspect, there is provided a large two-stroke uniflow scavenging internal combustion engine as follows. a cylinder having a cylinder liner and a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder; a combustion chamber defined within the cylinder liner between the reciprocating piston and the cylinder cover; a scavenging port disposed in the cylinder liner for introducing scavenging gas into the combustion chamber; an exhaust outlet disposed in the cylinder cover and controlled by an exhaust valve; an intake system having a scavenging receiver connected to the cylinder for supplying scavenging gas to the combustion chamber of the cylinder; a fuel system configured to supply a carbon-based fuel to the combustion chamber; an exhaust system coupled to the combustion chamber via the exhaust valve and having an exhaust receiver configured to receive an exhaust gas stream generated by combustion of the carbon-based fuel in the combustion chamber; the engine being a closed cycle oxy-fuel engine; a recirculation conduit connecting said exhaust air receiver to said scavenge air receiver; a blower disposed within the recirculation conduit for pressurizing exhaust gas from the exhaust receiver and for delivering the exhaust gas to the scavenge receiver; an oxygen supply system configured to supply oxygen to the inlet system; · Separation and carbon dioxide liquefaction system; a portion of the exhaust gas stream produced in the combustion chamber is diverted to the separation and carbon dioxide liquefaction system, the separation and carbon dioxide liquefaction system separating oxygen and carbon dioxide from the diverted exhaust gas stream while assisting in liquefying carbon dioxide from the diverted exhaust gas stream; the separation and carbon dioxide liquefaction system comprising a compressor for compressing the diverted exhaust gas stream to a target pressure and one or more heat exchangers for cooling the diverted exhaust gas stream to a target temperature; The combination of the desired pressure and the desired temperature causes the liquefaction of the carbon dioxide in the vapor, thereby separating the oxygen in the diverted exhaust gas stream within a separation vessel.

[0025] According to the third aspect, there is provided a large two-stroke uniflow scavenging internal combustion engine as follows. This engine has: a cylinder having a cylinder liner and a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder; a combustion chamber defined within the cylinder liner between the reciprocating piston and the cylinder cover; a scavenging port disposed in the cylinder liner for introducing scavenging gas into the combustion chamber; an exhaust outlet disposed in the cylinder cover and controlled by an exhaust valve; an intake system having a scavenging receiver connected to the cylinder for supplying scavenging gas to the combustion chamber of the cylinder; a fuel system configured to supply a carbon-based fuel to the combustion chamber; an exhaust system coupled to the combustion chamber via the exhaust valve and having an exhaust receiver configured to receive an exhaust gas stream generated by combustion of the carbon-based fuel in the combustion chamber; the engine being a closed cycle oxy-fuel engine; a recirculation conduit connecting said exhaust air receiver to said scavenge air receiver; a blower disposed within the recirculation conduit for pressurizing exhaust gas from the exhaust receiver and for delivering the exhaust gas to the scavenge receiver; an oxygen supply system configured to supply oxygen to the inlet system; · Separation and carbon dioxide liquefaction system; a portion of the exhaust gas stream produced in the combustion chamber is diverted to the separation and carbon dioxide liquefaction system, the separation and carbon dioxide liquefaction system separating oxygen and carbon dioxide from the diverted exhaust gas stream while assisting in liquefying carbon dioxide from the diverted exhaust gas stream; The mole fraction of carbon dioxide in the scavenging gas supplied to the combustion chamber is greater than 0.70 mol / mol.

[0026] According to the fourth aspect, there is provided a large two-stroke uniflow scavenging internal combustion engine as follows. This engine has: a cylinder having a cylinder liner and a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder; a combustion chamber defined within the cylinder liner between the reciprocating piston and the cylinder cover; a scavenging port disposed in the cylinder liner for introducing scavenging gas into the combustion chamber; an exhaust outlet disposed in the cylinder cover and controlled by an exhaust valve; an intake system having a scavenging receiver connected to the cylinder for supplying scavenging gas to the combustion chamber of the cylinder; a fuel system configured to supply a carbon-based fuel to the combustion chamber; an exhaust system coupled to the combustion chamber via the exhaust valve and having an exhaust receiver configured to receive an exhaust gas stream generated by combustion of the carbon-based fuel in the combustion chamber; the engine being a closed cycle oxy-fuel engine; a recirculation conduit connecting said exhaust air receiver to said scavenge air receiver; a blower disposed within the recirculation conduit for pressurizing exhaust gas from the exhaust receiver and for delivering the exhaust gas to the scavenge receiver; an oxygen supply system configured to supply oxygen to the inlet system; · Separation and carbon dioxide liquefaction system; a portion of the exhaust gas stream produced in the combustion chamber is diverted to the separation and carbon dioxide liquefaction system, the separation and carbon dioxide liquefaction system separating oxygen and carbon dioxide from the diverted exhaust gas stream while assisting in liquefying carbon dioxide from the diverted exhaust gas stream; The mole fraction of nitrogen in the scavenging gas supplied to the combustion chamber is less than 0.05 mol / mol.

[0027] According to the fifth aspect, there is provided a large two-stroke uniflow scavenging internal combustion engine as follows. This engine comprises: a cylinder having a cylinder liner and a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder; a combustion chamber defined within the cylinder liner between the reciprocating piston and the cylinder cover; a scavenging port disposed in the cylinder liner for introducing scavenging gas into the combustion chamber; an exhaust outlet disposed in the cylinder cover and controlled by an exhaust valve; an intake system having a scavenging receiver connected to the cylinder for supplying scavenging gas to the combustion chamber of the cylinder; a fuel system configured to supply a carbon-based fuel to the combustion chamber; an exhaust system coupled to the combustion chamber via the exhaust valve and having an exhaust receiver configured to receive an exhaust gas stream generated by combustion of the carbon-based fuel in the combustion chamber; the engine being a closed cycle oxy-fuel engine; a recirculation conduit connecting said exhaust air receiver to said scavenge air receiver; a blower disposed within the recirculation conduit for pressurizing exhaust gas from the exhaust receiver and for delivering the exhaust gas to the scavenge receiver; an oxygen supply system configured to supply oxygen to the inlet system; · Separation and carbon dioxide liquefaction system; a portion of the exhaust gas stream produced in the combustion chamber is diverted to the separation and carbon dioxide liquefaction system, the separation and carbon dioxide liquefaction system separating oxygen and carbon dioxide from the diverted exhaust gas stream while assisting in liquefying carbon dioxide from the diverted exhaust gas stream; The mole fraction of oxygen in the scavenging gas supplied to the combustion chamber is greater than 0.17 mol / mol.

[0028] According to a sixth aspect, there is provided a large two-stroke uniflow scavenging internal combustion engine as follows. This engine comprises: a cylinder having a cylinder liner and a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder; a combustion chamber defined within the cylinder liner between the reciprocating piston and the cylinder cover; a scavenging port disposed in the cylinder liner for introducing scavenging gas into the combustion chamber; an exhaust outlet disposed in the cylinder cover and controlled by an exhaust valve; an intake system having a scavenging receiver connected to the cylinder for supplying scavenging gas to the combustion chamber of the cylinder; a fuel system configured to supply a carbon-based fuel to the combustion chamber; an exhaust system coupled to the combustion chamber via the exhaust valve and having an exhaust receiver configured to receive an exhaust gas stream generated by combustion of the carbon-based fuel in the combustion chamber; the engine being a closed cycle oxy-fuel engine; a recirculation conduit connecting said exhaust air receiver to said scavenge air receiver; a blower disposed within the recirculation conduit for pressurizing exhaust gas from the exhaust receiver and for delivering the exhaust gas to the scavenge receiver; an oxygen supply system configured to supply oxygen to the inlet system; · Separation and carbon dioxide liquefaction system; a portion of the exhaust gas stream produced in the combustion chamber is diverted to the separation and carbon dioxide liquefaction system which separates oxygen and carbon dioxide from the diverted exhaust gas stream while assisting in liquefying carbon dioxide from the diverted exhaust gas stream.

[0029] According to the seventh aspect, there is provided a large two-stroke uniflow scavenging internal combustion engine as follows. This engine comprises: a cylinder having a cylinder liner and a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder; a combustion chamber defined within the cylinder liner between the reciprocating piston and the cylinder cover; a scavenging port disposed in the cylinder liner for introducing scavenging gas into the combustion chamber; an exhaust outlet disposed in the cylinder cover and controlled by an exhaust valve; an intake system having a scavenging receiver connected to the cylinder for supplying scavenging gas to the combustion chamber of the cylinder; a fuel system configured to supply a carbon-based fuel to the combustion chamber; an exhaust system coupled to the combustion chamber via the exhaust valve and having an exhaust receiver configured to receive an exhaust gas stream generated by combustion of the carbon-based fuel in the combustion chamber; the engine being a closed cycle oxy-fuel engine; a recirculation conduit connecting said exhaust air receiver to said scavenge air receiver; a blower disposed within the recirculation conduit for pressurizing exhaust gas from the exhaust receiver and for delivering the exhaust gas to the scavenge receiver; an oxygen supply system configured to supply oxygen to the inlet system; · Separation and carbon dioxide liquefaction system; a portion of the exhaust gas stream produced in the combustion chamber is diverted to the separation and carbon dioxide liquefaction system, the separation and carbon dioxide liquefaction system separating oxygen and carbon dioxide from the diverted exhaust gas stream while assisting in liquefying carbon dioxide from the diverted exhaust gas stream; the oxygen supply system includes a liquid oxygen tank; At least one of the coolers in the bypass conduit is a heat exchanger that exchanges heat between the diverted exhaust gas and liquid oxygen supplied from the liquid oxygen tank to the scavenging air receiver.

[0030] These and other aspects will become more apparent from the accompanying drawings and the embodiments described below. [Brief description of the drawings]

[0031] Various aspects, embodiments, and implementations will be described in detail below with reference to exemplary embodiments illustrated in the drawings. [Figure 1] FIG. 1 shows a schematic front view of a large two-stroke internal combustion engine according to an embodiment. [Diagram 2] The following shows an overview of the large two-stroke engine in Figure 1, seen from the rear. [Diagram 3] 2 is a schematic representation of an embodiment of the large two-stroke engine of FIG. 1 having a separation and carbon dioxide liquefaction system. [Figure 4] 2 is a schematic representation of an embodiment of the large two-stroke engine of FIG. 1 having a separation and carbon dioxide liquefaction system. Detailed explanation

[0032] In the following detailed description, the internal combustion engine will be described with reference to an example embodiment of a crosshead type large slow speed uniflow scavenging two-stroke turbocharged internal combustion engine. A crosshead type large slow speed uniflow scavenging turbocharged internal combustion engine can be a compression ignition (i.e. high pressure) engine, in which fuel is injected at or near the top dead center (TDC) of the piston, or it can be a spark ignition (also low pressure or premixed) engine, in which scavenging air is mixed with fuel before or during compression and the mixture is ignited or otherwise. In the case of a premixed engine, a pilot ignition with an additive liquid (e.g. fuel oil) is usually provided at or near TDC to ensure ignition.

[0033] 1-3 show a turbocharged large low-speed two-stroke diesel engine. The engine has a crankshaft 8 and a crosshead 9 and operates on the diesel principle, i.e. it is a compression ignition engine. FIG. 3 shows a schematic representation of a turbocharged large low-speed two-stroke diesel engine together with its intake and exhaust systems. In this embodiment the engine has six cylinders in series. A turbocharged large low-speed two-stroke internal combustion engine usually has 4 to 14 cylinders arranged in series. The cylinders are carried on a cylinder frame 23. The cylinder frame 23 is carried on an engine frame 11. Such an engine can also be used, for example, as the main engine of a ship or as a stationary engine for driving a generator in a power plant. The total power output of the engine can be, for example, in the range 1000-110000 kW.

[0034] The engine can be configured as a dual fuel engine. The engine can be a compression ignition engine or a premixed engine. The engine in this embodiment is a two-stroke uniflow type engine, with each cylinder having a scavenging port 18 in the lower region of the cylinder liner 1 and an exhaust valve 4 at the top center of the cylinder liner 1. The engine has at least one mode of operation with carbon-based fuels such as natural gas, methanol, dimethyl ether (DME), or fuel oil (e.g. marine diesel).

[0035] The scavenging gas is led to the scavenging ports 18 of each cylinder 1 through the scavenging receiver 2. The piston 10 reciprocates between bottom dead center (BDC) and top dead center (TDC) in the cylinder liner 1, compressing the scavenging gas. Fuel is injected at high pressure into the combustion chamber in the cylinder liner 1 through a number of fuel valves 50 arranged in the cylinder cover 22 at or near TDC (Diesel principle, i.e. compression ignition). If the engine is configured as a premixed engine, fuel is introduced at relatively low pressure through the fuel inlet valves on the piston's way to TDC (Otto principle, i.e. premixed). Typically, two or more fuel inlet valves are provided for each cylinder. The fuel inlet valves can be provided in the cylinder liner above the scavenging ports 18 or in the cylinder cover 22. Combustion follows the injection of the fuel and produces exhaust. If the engine is configured as a compression ignition engine, two or more fuel valves 50 are provided in each cylinder cover 22. The fuel valve 50 is configured to inject only fuel into the combustion chamber. The fuel valve 50 is arranged in the cylinder cover 22 around the exhaust valve 4, which is arranged in the center of the cylinder cover 22. Although not shown, in some embodiments, the cylinder cover 22 may be provided with an additional (usually small) fuel valve arranged to inject ignition fluid to ensure ignition of the fuel (e.g., gaseous fuel). The ignition fluid may be, for example, dimethyl ether (DME) or fuel oil. However, it may also be other forms of ignition enhancer, such as, for example, hydrogen. Although not shown, in some embodiments, a fuel valve is arranged along the cylinder liner (shown in dashed lines). The fuel valve introduces fuel into the cylinder when the piston 10 is on its way from BDC to TDC, before it passes the fuel valve. Thus, if the engine is configured for premixing, the piston 10 compresses the mixture of scavenging air and fuel. Ignition is timed at or near TDC. Ignition is achieved by a spark, a laser, injection of ignition fluid, etc. In the embodiment having the fuel valve, the pressure at which the fuel is introduced is significantly lower than the pressure at which the fuel is injected in the embodiment having the fuel valve 50 in the cylinder cover 22 .Because the fuel valve 50 located in the cylinder cover 22 injects fuel when the piston is at or near TDC, the fuel injection pressure must be significantly higher than the compression pressure.

[0036] When the exhaust valve 4 is opened, the exhaust gas flows through the exhaust duct of the cylinder into the exhaust gas receiver 3, and then through the recirculation conduit 5 to the blower 7 via the first cooler 14, from where the exhaust gas flows back to the scavenge air receiver 2. If the fuel is a hydrocarbon fuel and water is generated during combustion, the cooler 14 is configured to remove most of the water from the exhaust gas stream and drain the removed water into a water tank 16. A portion of the exhaust gas is diverted from the recirculation conduit 5 to a separation and carbon dioxide liquefaction system 60, preferably at a location downstream of the first cooler 14 and upstream of the blower 7. The separation and carbon dioxide liquefaction system 60 liquefies the carbon dioxide, stores the liquefied carbon dioxide in a liquefied carbon dioxide storage tank 49, and transports the oxygen separated from the carbon dioxide in the diverted exhaust gas stream to the scavenge air receiver 2. An oxygen source (i.e., an oxygen supply system 12, in this embodiment a liquid oxygen tank 12) supplies an oxygen flow to the scavenge air receiver 2.

[0037] The exhaust gas pressurized by the blower 7 is mixed with oxygen from the oxygen supply system 12 in the scavenging receiver to form scavenging gas that can be supplied to the combustion chamber in the cylinder liner 1 through the scavenging ports 18 .

[0038] Referring now to FIG. 4, the engine of FIGS. 1-3 is disclosed in more detail, in particular with regard to the separation and carbon dioxide liquefaction system. In this version of the embodiment, the engine is operated on a hydrocarbon fuel. The combustion gases therefore contain both water and carbon dioxide. The first cooler 14 is configured to condense and separate a large portion of the water in the exhaust gas. The water condensed and separated from the exhaust gas is transported by conduit 15 to a water tank 16. A portion of the exhaust gas leaving the first cooler 14 is diverted from the main flow of cooled exhaust gas to a bypass conduit 40. The amount of exhaust gas diverted from the recirculation conduit 5 is, in an embodiment, regulated by a control valve 38 located in the bypass conduit 40. The amount of exhaust gas diverted is adjusted corresponding to the amount of carbon dioxide produced in the combustion process so that the total amount of carbon dioxide recirculated in the engine is substantially constant. Preferably, the engine comprises a control device, such as a microcontroller (not shown), configured to be informed of the amount of carbon in the injected fuel and to calculate the amount of carbon dioxide produced by the combustion and to adjust the amount of exhaust gas diverted accordingly. The remaining part of the exhaust gas leaving the first cooler 14 goes to the blower 7 and is led from there as pressurized exhaust gas to the scavenge air receiver 2. It should be noted that it is also possible to control the engine operation in a different way than determining the required amount of carbon dioxide removal as described above. For example, the absolute pressure in the exhaust air receiver can be used as a parameter for determining how much carbon dioxide needs to be removed from the exhaust gas.

[0039] In this example, the controller uses a base pressure in the exhaust receiver, or a base pressure that is a function of engine operating conditions such as engine load, to increase, decrease, or maintain carbon dioxide removal.

[0040] In other words, if the pressure determined or measured in the exhaust receiver is within an acceptable range around the reference pressure, the amount of carbon dioxide removed is not changed, but if the pressure determined or measured in the exhaust receiver is higher than the reference pressure, the amount of carbon dioxide removed is increased, and if the pressure determined or measured in the exhaust receiver is lower than the reference pressure, the amount of carbon dioxide removed is decreased.

[0041] The diversion conduit 40 is equipped with a compressor 42, which is arranged to substantially increase the pressure of the diverted exhaust gas, for example by at least 40 bar. Downstream of the compressor 42, a second cooler 44 is provided, which condenses the residual water, which is separated and sent to the water tank 16. Downstream of the second cooler, a third cooler 45 is arranged. The third cooler 45 is a heat exchanger, which exchanges heat with liquid oxygen from the liquid oxygen tank 61, which is sent to the scavenge air receiver 2 through a liquid oxygen supply conduit 63.

[0042] A fourth cooler 46 is arranged downstream of the third cooler 45. The fourth cooler 46 exchanges heat with a mixture of oxygen and carbon dioxide, supplied from a carbon dioxide liquefaction and oxygen separation vessel 47 and supplied from a liquefied carbon dioxide storage tank 49. A bypass conduit leads to the carbon dioxide liquefaction and oxygen separation vessel 47. When the diverted exhaust gas leaves the fourth cooler 46, the temperature is low enough and the pressure is high enough for the carbon dioxide in the diverted exhaust gas to be liquefied in the carbon dioxide liquefaction and oxygen separation vessel 47. Thus, the carbon dioxide is separated from the oxygen. Oxygen does not liquefy at these temperatures and pressures. Thus, the lower part of the carbon dioxide liquefaction and oxygen separation vessel 47 contains liquefied carbon dioxide, and the upper part of the carbon dioxide liquefaction and oxygen separation vessel 47 contains a mixture of oxygen and carbon dioxide in the gas phase. The lower part of the carbon dioxide liquefaction and oxygen separation vessel 47 is connected to the liquefied carbon dioxide tank 49 by a liquefied carbon dioxide conduit 48. Liquefied carbon dioxide gas is stored in the lower part of the liquefied carbon dioxide gas tank 49, and a mixture (gas phase) of oxygen and carbon dioxide gas is stored in the upper part of the liquefied carbon dioxide gas tank 49. The gas phase mixture in the carbon dioxide liquefaction / oxygen separation vessel 47 and preferably the liquefied carbon dioxide tank 49 is sent to the scavenging air receiver 2 through the oxygen return conduit 43 via expansion valves 65 and 66, respectively. The return conduit 43 is not provided in some embodiments. However, when provided, the return conduit 43 passes through a fourth cooler 46 for heat exchange with the diverted exhaust gas.

[0043] The amount of oxygen in the scavenging gas is regulated by adjusting the flow of liquid oxygen supplied from a liquid oxygen tank 61 through a liquid oxygen supply conduit 63 to the scavenging receiver 2. This flow rate is regulated by a control valve 64 located in the oxygen supply conduit 63. The control valve 64 is preferably under the control of a controller.

[0044] A bypass conduit 25 is provided extending from the exhaust receiver 3 to the scavenging receiver 2 to bypass the blower 7. A bypass control valve 26 is also provided to control the flow of gas from the scavenging receiver 2 to the exhaust receiver 3. The bypass control valve 26 acts as a process control handle. By allowing the carbon dioxide rich gas (before oxygen is added) to bypass the cylinder and return to the exhaust receiver, the amount of excess scavenging can be reduced. In this way, the amount of oxygen short-circuited can be minimized. Furthermore, the scavenging efficiency can be reduced, allowing hot residual gases to remain in the cylinder until the next cycle. In this way, higher compression temperatures can be achieved if necessary, such as to avoid a tendency to knock. 〔example〕

[0045] In the example operating conditions, fuel with Sfoc=362gCH3OH / kWh is used, and the thermal efficiency is assumed to be 50%.

[0046] In the exhaust receiver, the temperature of the exhaust gas is typically 400-500°C and the pressure is about 4 bar. yCO2 is about 0.85 mol / mol and yO2 is about 0.15 mol / mol.

[0047] Downstream of the first cooler 14, the exhaust gas temperature is typically around 5° C. and the pressure around 4 bar. yCO2 is around 0.85 mol / mol and yO2 is around 0.15 mol / mol.

[0048] The blower 7 increases the pressure by 0.3 bar.

[0049] In the scavenge receiver, the temperature of the scavenge gas is typically about 10°C and the pressure is about 4.3 bar. yCO2 is about 0.79 mol / mol and yO2 is about 0.21 mol / mol.

[0050] The compressor increases the pressure of the diverted exhaust gases to about 41 bar. Downstream of the second cooler 44, the diverted exhaust gases have a temperature of 10° C. and a pressure of about 45 bar. yCO2 is about 0.79 mol / mol and yO2 is about 0.21 mol / mol.

[0051] By the time the diverted exhaust gas reaches the carbon dioxide liquefaction / oxygen separation vessel 47, its temperature is minus 20°C and its pressure is approximately 45 bar.

[0052] The temperature of the liquid oxygen in the liquid oxygen tank 61 is about -140°C, and the pressure is about 20 bar.

[0053] Various aspects and implementations of the invention have been described with several examples. However, upon review of 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 carrying out the claimed invention. The words "comprise", "have", and "include" in the claims do not exclude the presence of elements or steps not described. The absence of a plurality of elements in the claims does not exclude the presence of a plurality of the elements. Reference signs used in the claims should not be construed as limiting the scope of the invention. Unless otherwise noted, the drawings are intended to be read together with the specification and are an integral part of this disclosure.

Claims

1. A large two-stroke uniflow scavenging internal combustion engine, - a cylinder having a cylinder liner and a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder; - a combustion chamber formed between the reciprocating piston and the cylinder cover within the cylinder liner; - a scavenging port for introducing scavenging gas into the combustion chamber, the scavenging port being arranged in the cylinder liner; - an exhaust outlet arranged in the cylinder cover and controlled by an exhaust valve; - an intake system having a scavenging receiver connected to the cylinder for supplying scavenging gas to the combustion chamber of the cylinder; - a fuel system configured to supply carbon-based fuel to the combustion chamber; - an exhaust system having an exhaust receiver coupled to the combustion chamber via the exhaust valve and receiving the exhaust gas flow generated by the combustion of the carbon-based fuel in the combustion chamber; comprising, the engine being a closed cycle oxy-fuel engine, and further, - a recirculation conduit connecting the exhaust receiver to the scavenging receiver; - a blower arranged in the recirculation conduit for pressurizing the exhaust gas from the exhaust receiver and feeding it into the scavenging receiver; - an oxygen supply system configured to supply oxygen to the intake system; - a separation and carbon dioxide liquefaction system; comprising, a part of the exhaust gas flow generated in the combustion chamber being diverted to the separation and carbon dioxide liquefaction system, the separation and carbon dioxide liquefaction system separating oxygen and carbon dioxide from the diverted exhaust gas flow while being assisted in the liquefaction of carbon dioxide from the diverted exhaust gas flow, and the engine further, - a bypass conduit for bypassing the part diverted from the exhaust gas flow, the bypass conduit being coupled to the recirculation conduit and having a bypass compressor and one or more coolers, comprising, an engine.

2. The engine according to claim 1, comprising a first cooler for cooling the exhaust gas within the recirculation conduit.

3. The engine according to claim 2, wherein the bypass conduit is coupled to the recirculation conduit at a position downstream of the first cooler.

4. The engine according to claim 2, wherein the first cooler is configured to separate water from the exhaust gas.

5. The carbon-based fuel is a hydrocarbon-based fuel, water is generated by combustion of the hydrocarbon-based fuel in the combustion chamber, and the engine includes a water tank that receives the water separated by the first cooler. The engine according to claim 4.

6. The one or more coolers are arranged downstream of the bypass compressor in the bypass conduit. The engine according to any one of claims 1 to 5.

7. The separation and carbon dioxide liquefaction system includes a compressor that pressurizes the bypassed exhaust gas stream to a target pressure, and one or more heat exchangers for cooling the bypassed exhaust gas stream to a target temperature. The combination of the desired pressure and the desired temperature causes liquefaction of carbon dioxide in the steam, thereby separating oxygen in the bypassed exhaust gas stream in the separation container. The engine according to any one of claims 1 to 5.

8. The oxygen supply system has a liquid oxygen tank. The engine according to any one of claims 1 to 5.

9. The combustion chamber is configured to combust a carbon-based fuel with oxygen, thereby generating an exhaust gas stream containing carbon dioxide. The engine according to any one of claims 1 to 5.

10. The molar fraction of carbon dioxide in the scavenging gas supplied to the combustion chamber is greater than 0.70 mol / mol. The engine according to any one of claims 1 to 5.

11. The molar fraction of nitrogen in the scavenging gas supplied to the combustion chamber is less than 0.05 mol / mol. The engine according to any one of claims 1 to 5.

12. The molar fraction of oxygen in the scavenging gas supplied to the combustion chamber is greater than 0.17 mol / mol. The engine according to any one of claims 1 to 5.

13. At least one of the coolers in the bypass conduit is a heat exchanger that performs heat exchange between the bypassed exhaust gas and the liquid oxygen supplied from the liquid oxygen tank to the scavenging receiver. The engine according to claim 8.

14. A large two-stroke uniflow scavenging internal combustion engine, - A cylinder having a cylinder liner and a reciprocating piston in the cylinder liner, and a cylinder cover covering the cylinder; - A combustion chamber formed between the reciprocating piston and the cylinder cover in the cylinder liner; - A scavenging port for introducing scavenging gas into the combustion chamber, the scavenging port being arranged in the cylinder liner; - An exhaust outlet arranged in the cylinder cover and controlled by an exhaust valve; - An intake system having a scavenging receiver connected to the cylinder for supplying scavenging gas to the combustion chamber of the cylinder; - A fuel system configured to supply carbon-based fuel to the combustion chamber; - An exhaust system having an exhaust receiver coupled to the combustion chamber via the exhaust valve and receiving an exhaust gas flow generated by combustion of the carbon-based fuel in the combustion chamber; - Comprising, the engine being a closed-cycle oxy-fuel engine, and further, - A recirculation conduit connecting the exhaust receiver to the scavenging receiver; - A blower arranged in the recirculation conduit for pressurizing exhaust gas from the exhaust receiver and feeding it into the scavenging receiver; - An oxygen supply system configured to supply oxygen to the intake system; - A separation and carbon dioxide liquefaction system; - Comprising, a part of the exhaust gas flow generated in the combustion chamber is diverted to the separation and carbon dioxide liquefaction system, and the separation and carbon dioxide liquefaction system separates oxygen and carbon dioxide from the diverted exhaust gas flow while being assisted in liquefying carbon dioxide from the diverted exhaust gas flow, - The separation and carbon dioxide liquefaction system has a compressor for pressurizing the diverted exhaust gas flow to a target pressure and one or more heat exchangers for cooling the diverted exhaust gas flow to a target temperature, - The combination of the desired pressure and the desired temperature causes liquefaction of carbon dioxide in the vapor, thereby separating oxygen in the diverted exhaust gas flow in a separation container, - Engine.

15. - A large two-stroke uniflow scavenging internal combustion engine, - A cylinder having a cylinder liner and a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder; - A combustion chamber formed between the reciprocating piston and the cylinder cover within the cylinder liner; - A scavenging port for introducing scavenging gas into the combustion chamber, the scavenging port being arranged in the cylinder liner; - An exhaust outlet arranged in the cylinder cover and controlled by an exhaust valve; - An intake system having a scavenging receiver connected to the cylinder for supplying scavenging gas to the combustion chamber of the cylinder; - A fuel system configured to supply carbon-based fuel to the combustion chamber; - An exhaust system having an exhaust receiver coupled to the combustion chamber via the exhaust valve and receiving an exhaust gas flow generated by combustion of the carbonaceous fuel in the combustion chamber; comprising, wherein the engine is a closed cycle oxy-fuel engine, and further, - A recirculation conduit connecting the exhaust receiver to the scavenging receiver; - A blower disposed in the recirculation conduit for pressurizing exhaust gas from the exhaust receiver and feeding it into the scavenging receiver; - An oxygen supply system configured to supply oxygen to the intake system; - A separation and carbon dioxide liquefaction system; comprising, a part of the exhaust gas flow generated in the combustion chamber is diverted to the separation and carbon dioxide liquefaction system, and the separation and carbon dioxide liquefaction system separates oxygen and carbon dioxide from the diverted exhaust gas flow while being assisted in liquefying carbon dioxide from the diverted exhaust gas flow, The molar fraction of carbon dioxide in the scavenging gas supplied to the combustion chamber is greater than 0.70 mol / mol, engine.

16. A large two-stroke uniflow scavenging internal combustion engine, - A cylinder having a cylinder liner and a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder; - A combustion chamber formed between the reciprocating piston and the cylinder cover within the cylinder liner; - 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; - An intake system having a scavenging receiver connected to the cylinder for supplying scavenging gas to the combustion chamber of the cylinder; - A fuel system configured to supply carbonaceous fuel to the combustion chamber; - An exhaust system having an exhaust receiver coupled to the combustion chamber via the exhaust valve and receiving an exhaust gas flow generated by combustion of the carbonaceous fuel in the combustion chamber; comprising, wherein the engine is a closed cycle oxy-fuel engine, and further, - A recirculation conduit connecting the exhaust receiver to the scavenging receiver; - A blower disposed in the recirculation conduit for pressurizing exhaust gas from the exhaust receiver and feeding it into the scavenging receiver; - An oxygen supply system configured to supply oxygen to the intake system; - A separation and carbon dioxide liquefaction system; comprising, a part of the exhaust gas flow generated in the combustion chamber being diverted to the separation and carbon dioxide liquefaction system, the separation and carbon dioxide liquefaction system separating oxygen and carbon dioxide from the diverted exhaust gas flow while assisting in the liquefaction of carbon dioxide from the diverted exhaust gas flow, the molar fraction of nitrogen in the scavenging gas supplied to the combustion chamber being less than 0.05 mol / mol, an engine.

17. A large two-stroke uniflow scavenging internal combustion engine, - a cylinder having a cylinder liner and a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder; - a combustion chamber formed between the reciprocating piston and the cylinder cover within the cylinder liner; - a scavenging port for introducing scavenging gas into the combustion chamber, the scavenging port being arranged in the cylinder liner; - an exhaust outlet arranged in the cylinder cover and controlled by an exhaust valve; - an intake system having a scavenging receiver connected to the cylinder for supplying scavenging gas to the combustion chamber of the cylinder; - a fuel system configured to supply a carbon-based fuel to the combustion chamber; - an exhaust system having an exhaust receiver coupled to the combustion chamber via the exhaust valve and receiving the exhaust gas flow generated by the combustion of the carbon-based fuel in the combustion chamber; comprising, the engine being a closed cycle oxy-fuel engine, and further, - a recirculation conduit connecting the exhaust receiver to the scavenging receiver; - a blower arranged in the recirculation conduit for pressurizing the exhaust gas from the exhaust receiver and feeding it into the scavenging receiver; - an oxygen supply system configured to supply oxygen to the intake system; - a separation and carbon dioxide liquefaction system; comprising, a part of the exhaust gas flow generated in the combustion chamber being diverted to the separation and carbon dioxide liquefaction system, the separation and carbon dioxide liquefaction system separating oxygen and carbon dioxide from the diverted exhaust gas flow while assisting in the liquefaction of carbon dioxide from the diverted exhaust gas flow, the molar fraction of oxygen in the scavenging gas supplied to the combustion chamber being greater than 0.17 mol / mol, an engine.

18. A large two-stroke uniflow scavenging internal combustion engine, - a cylinder having a cylinder liner and a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder; - A combustion chamber formed between the reciprocating piston and the cylinder cover within the cylinder liner; - A scavenging port for introducing scavenging gas into the combustion chamber, the scavenging port being arranged in the cylinder liner; - An exhaust outlet arranged in the cylinder cover and controlled by an exhaust valve; - An intake system having a scavenging receiver connected to the cylinder for supplying scavenging gas to the combustion chamber of the cylinder; - A fuel system configured to supply carbon-based fuel to the combustion chamber; - An exhaust system having an exhaust receiver coupled to the combustion chamber via the exhaust valve and receiving the exhaust gas flow generated by the combustion of the carbon-based fuel in the combustion chamber; - Comprising, the engine being a closed-cycle oxy-fuel engine, and further, - A recirculation conduit connecting the exhaust receiver to the scavenging receiver; - A blower arranged in the recirculation conduit for pressurizing the exhaust gas from the exhaust receiver and feeding it into the scavenging receiver; - An oxygen supply system configured to supply oxygen to the intake system; - A separation and carbon dioxide liquefaction system; - Comprising, a part of the exhaust gas flow generated in the combustion chamber is diverted to the separation and carbon dioxide liquefaction system, and the separation and carbon dioxide liquefaction system separates oxygen and carbon dioxide from the diverted exhaust gas flow while being assisted in the liquefaction of carbon dioxide from the diverted exhaust gas flow, an engine.

19. A large two-stroke uniflow scavenging internal combustion engine, - A cylinder having a cylinder liner and a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder; - A combustion chamber formed between the reciprocating piston and the cylinder cover within the cylinder liner; - A scavenging port for introducing scavenging gas into the combustion chamber, the scavenging port being arranged in the cylinder liner; - An exhaust outlet arranged in the cylinder cover and controlled by an exhaust valve; - An intake system having a scavenging receiver connected to the cylinder for supplying scavenging gas to the combustion chamber of the cylinder; - A fuel system configured to supply carbon-based fuel to the combustion chamber; - An exhaust system having an exhaust receiver coupled to the combustion chamber via the exhaust valve and receiving the exhaust gas flow generated by the combustion of the carbon-based fuel in the combustion chamber; comprising, wherein the engine is a closed-cycle oxy-fuel engine, and further, - a recirculation duct connecting the exhaust receiver to the scavenging receiver; - a blower disposed in the recirculation duct for pressurizing exhaust gas from the exhaust receiver and feeding it into the scavenging receiver; - an oxygen supply system configured to supply oxygen to the intake system; - a separation and carbon dioxide liquefaction system; comprising, wherein a part of the exhaust gas flow generated in the combustion chamber is diverted to the separation and carbon dioxide liquefaction system, and the separation and carbon dioxide liquefaction system separates oxygen and carbon dioxide from the diverted exhaust gas flow while being assisted in the liquefaction of carbon dioxide from the diverted exhaust gas flow, the oxygen supply system has a liquid oxygen tank, at least one of the coolers in the bypass duct is a heat exchanger that performs heat exchange between the diverted exhaust gas and the liquid oxygen supplied from the liquid oxygen tank to the scavenging receiver, engine.

Images