Large two-stroke turbocharged uniflow scavenged internal combustion engine having a system for reducing nitrous oxide emissions, and method for reducing nitrous oxide emissions thereof

Abstract

A large two-stroke turbocharged uniflow scavenged internal combustion engine and a method for removing nitrous oxide from the exhaust gas of a large two-stroke turbocharged uniflow scavenged internal combustion engine by a wet electric scrubber are provided, the engine being configured for removing nitrous oxide from the exhaust gas using an electrically generated medium in a wet scrubber.

Description

Technical Field

[0001] The present disclosure relates to a large two-stroke turbocharged uniflow scavenged internal combustion engine which operates in at least one mode with ammonia as a fuel for combustion in the engine and has a system for reducing nitrous oxide emissions, and the present disclosure also relates to a method for reducing nitrous oxide emissions of such an engine. Background Art

[0002] Large two-stroke turbocharged uniflow scavenged compression ignition crosshead internal combustion engines are commonly used in the propulsion systems of large ships or as prime movers in power plants. The large size, weight and power output make this internal combustion engine completely different from ordinary internal combustion engines and put large two-stroke turbocharged compression ignition internal combustion engines in a class of their own.

[0003] Internal combustion engines used to work mainly with hydrocarbon fuels, such as fuel oil such as diesel, or gas such as natural gas or petroleum gas. The combustion of hydrocarbon fuels releases carbon dioxide (CO2) and other greenhouse gases that cause air pollution and climate change. Unlike fossil fuel impurities that produce byproduct emissions, CO2 is an inevitable product of hydrocarbon combustion. The energy density and CO2 footprint of a particular fuel depend on the length of the hydrocarbon chain and the complexity of the hydrocarbon molecules of the particular fuel. Therefore, gaseous hydrocarbon fuels have a lower footprint than liquid hydrocarbon fuels, and the disadvantage of gaseous hydrocarbon fuels is that the disposal and storage of gaseous hydrocarbon fuels are more challenging and more expensive. In order to reduce the CO2 footprint, non-hydrocarbon fuels are being studied.

[0004] Ammonia is a synthetic product obtained from fossil fuels, biomass, or renewable resources (wind, sun, water, or heat), and when ammonia is produced from renewable resources, it will have almost no carbon footprint or emit almost no CO2, SOx, particulate matter, or unburned hydrocarbons when burned.

[0005] Ammonia has been tested and used on a small scale in small spark-ignition internal combustion engines, but has not yet been used to power compression-ignition internal combustion engines.

[0006] Engines fueled by ammonia tend to produce nitrous oxide (N2O) as a byproduct of combustion. Without countermeasures, the exhaust containing this nitrous oxide will eventually enter the atmosphere. It is known that nitrous oxide has a significant global warming potential, which is about 265 times that of CO2 according to the UN climate report IPPC AR5. Therefore, it is necessary to reduce the nitrous oxide emissions of large two-stroke turbocharged single-flow scavenging internal combustion engines fueled by ammonia.

[0007] Commercially available systems for removing nitrous oxide from exhaust gas are used for catalytic decomposition and thermal destruction. These methods convert nitrous oxide into nitrogen and oxygen. Catalytic decomposition operates at about 500°C, and thermal destruction operates at nearly 1000°C. The temperature of the exhaust gas of a large two-stroke turbocharged single-flow scavenging internal combustion engine is not enough to be used with these known methods, because the exhaust gas temperature before the turbine is usually between 300°C and 500°C depending on the operating conditions, and the exhaust gas temperature after the turbine is usually between 150°C and 250°C depending on the operating conditions. Therefore, catalytic decomposition and thermal destruction are not suitable for removing nitrous oxide from the exhaust gas of a large two-stroke turbocharged single-flow scavenging internal combustion engine fueled by ammonia.

[0008] DK178072B1 discloses a large two-stroke turbocharged single-flow scavenging internal combustion engine, which operates with a first fuel including a liquid fuel and a second fuel including ammonia, and the engine includes: at least one cylinder having a cylinder liner and a reciprocating piston located in the cylinder liner and having a cylinder head covering the cylinder; a combustion chamber formed in the cylinder between the cylinder head and the reciprocating piston; an ammonia fuel system configured to supply pressurized ammonia to a fuel valve arranged in the cylinder head; a turbocharging system including at least one compressor for compressing scavenging air and at least one exhaust-driven turbine. A scrubber is provided for cleaning the recirculated exhaust gas before it re-enters the combustion chamber. Increasing the rate of exhaust gas recirculation when operating with a low calorific value fuel such as ammonia ensures that NOx emissions remain at a low level. Summary of the invention

[0009] The object is to provide a large two-stroke turbocharged uniflow scavenged internal combustion engine which overcomes or at least reduces the above mentioned problems.

[0010] The foregoing and other objects are achieved by the present application.Other embodiments are apparent from the description and drawings.

[0011] According to a first aspect, there is provided a large two-stroke turbocharged uniflow scavenged internal combustion engine having at least one operating mode in which the primary fuel is ammonia, the engine comprising:

[0012] - at least one cylinder having a cylinder liner and a piston reciprocating in the cylinder liner and having a cylinder head covering the cylinder;

[0013] - a combustion chamber formed in the cylinder between the reciprocating piston and the cylinder head;

[0014] an ammonia fuel system configured for supplying pressurized ammonia to a fuel valve arranged in the cylinder head or in the cylinder liner;

[0015] a turbocharger system comprising at least one compressor for compressing scavenging air and comprising at least one exhaust-gas driven turbine; and

[0016] a nitrous oxide scrubber located downstream of the at least one exhaust-driven turbine, the nitrous oxide scrubber being configured to: convert nitrous oxide in the exhaust gas flowing through the scrubber into ammonia; and / or to reduce nitrous oxide in the exhaust gas flowing through the scrubber to nitrogen and oxygen or to nitrogen and hydroxide.

[0017] In a possible embodiment of the first aspect, the scrubber is an electroscrubber which couples wet scrubbing with an electrogenerated medium to convert nitrous oxide into ammonia or reduce nitrous oxide in the exhaust gas flowing through the scrubber to nitrogen and oxygen or to nitrogen and hydroxide in a single treatment stage, preferably, the electrogenerated medium is a Ni-based medium, more preferably, the electrogenerated medium is a NiI[NiICN4]3-medium.

[0018] In a possible implementation form of the first aspect, the engine includes a circulation system that circulates water containing a medium through the scrubber, the medium preferably being an electrically generated medium, and the circulation system preferably includes an electrolytic cell coupled to a voltage source and used to electrically generate the medium, the electrolytic cell preferably including at least two electrodes coupled to the voltage source.

[0019] In a possible implementation form of the first aspect, the engine comprises a device for separating ammonia from the exhaust gas, the device for separating ammonia from the exhaust gas is arranged downstream of the scrubber, and the device for separating ammonia from the exhaust gas preferably comprises a scrubber tower.

[0020] In a possible implementation form of the first aspect, the engine includes a condenser, which is located downstream of the turbine and upstream of the scrubber and is used to remove a portion of the water in the exhaust gas. The condenser is preferably a controlled condenser, and the condenser preferably has an outlet for disposing of the water removed from the exhaust gas. The condenser preferably has an inlet for receiving cooling water and an outlet for discharging the cooling water.

[0021] In a possible implementation form of the first aspect, the engine comprises an ammonia feed pump, wherein an outlet of the ammonia feed pump is fluidly connected to the fuel valve, the ammonia feed pump preferably having an inlet fluidly connected to the ammonia storage tank.

[0022] In a possible implementation form of the first aspect, the engine includes a controller configured to perform one or more of the following:

[0023] - controlling the functioning of the condenser in response to a signal representative of the amount of water or fluid in the circulation system, preferably in order to keep the amount of water in the circulation system constant; preferably, controlling the functioning of the condenser by controlling the temperature of the cooling water passing through the condenser in response to a signal representative of the amount of water or fluid in the circulation system, preferably in order to keep the amount of water in the circulation system constant;

[0024] - controlling the amount of power supplied by the voltage source to the electrolyser, preferably in response to a signal representative of the concentration of the electricity generating medium in the recirculating water;

[0025] - controlling the amount and / or pressure of ammonia supplied to the engine by the ammonia fuel system; preferably by adjusting the speed of the ammonia feed pump.

[0026] In a possible embodiment of the first aspect, a small amount of [15 or 14]aneN4 {[15 or 14]aneN4 = 1,4,8,12 (or 11)-tetraazacyclopentane (or tetra)decane} Ni is present in the aqueous solution. II In the case of the complex, the reduction of nitrous oxide takes place at the mercury electrode.

[0027] In a possible implementation form of the first aspect, the reduction of N2O to N2 is carried out on a gas diffusion electrode modified with Pt and Ni electrocatalysts.

[0028] According to a second aspect, there is provided a method for removing nitrous oxide from the exhaust gas of a large two-stroke turbocharged uniflow scavenged internal combustion engine having a turbocharger, the method comprising:

[0029] - Enable the engine to operate with ammonia as the main fuel;

[0030] - wet scrubbing of the exhaust gas downstream of the turbine of the turbocharger using a Ni-based medium, preferably a NiI[NiICN4]3-medium added to water, thereby converting the nitrous oxide in the exhaust gas into ammonia in a single treatment stage, or

[0031] Ni using macrocyclic polyamines added to water downstream of the turbocharger turbine ll The complex wet scrubs the exhaust gas, thereby reducing the nitrous oxide to nitrogen and oxygen and / or to nitrogen and hydroxide.

[0032] In a possible implementation form of the second aspect, the method comprises: electrically generating the medium; preferably electrically generating the medium in an electrolytic cell.

[0033] In a possible implementation form of the second aspect, the method comprises: circulating water containing the medium through a scrubber.

[0034] In a possible implementation form of the second aspect, the method comprises: separating ammonia from the exhaust gas after wet scrubbing; preferably, separating ammonia from the exhaust gas after wet scrubbing using a scrubber tower.

[0035] In a possible implementation form of the second aspect, the method comprises: controlling the water content in the exhaust gas before wet scrubbing; preferably, controlling the water content in the exhaust gas before wet scrubbing by removing water from the exhaust gas, preferably upstream of the turbine, preferably using a condenser.

[0036] In a possible implementation form of the second aspect, the method comprises: recirculating water containing said Ni-based medium in a circulation system comprising a wet scrubber.

[0037] In a possible implementation form of the second aspect, the method includes: before washing, controlling the amount of water in the circulation system by removing water from the exhaust gas; preferably, by increasing the function of the condenser when the amount of water in the circulation system is higher than an upper limit threshold, and by reducing the function of the condenser when the amount of water in the circulation system is lower than a lower limit threshold, the amount of water in the circulation system is controlled by removing water from the exhaust gas before washing.

[0038] In a possible implementation form of the second aspect, the method comprises: in the presence of a small amount of [15 or 14]aneN4 {[15 or 14]aneN4 = 1,4,8,12 (or 11)-tetraazacyclopentane (or tetra)decane} Ni II In the case of the complex, N2O is reduced at the mercury electrode.

[0039] In a possible implementation form of the second aspect, the method comprises reducing N2O to N2 on a gas diffusion electrode modified with Pt and Ni electrocatalysts.

[0040] These and other aspects will become apparent from the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In the following detailed portion of the present disclosure, various aspects, embodiments and implementations will be described in more detail with reference to example implementations shown in the accompanying drawings, in which:

[0042] Figure 1 is a front view of a large two-stroke diesel engine according to an example embodiment;

[0043] Figure 2 yes Figure 1 Side view of a large two-stroke engine;

[0044] Figure 3 yes Figure 1 A schematic diagram of an embodiment of a large two-stroke engine having an ammonia fuel system and a nitrous oxide reduction system;

[0045] Figure 4 yes Figure 3 a schematic diagram of an engine of an embodiment of the invention, wherein the ammonia fuel system is shown in more detail; and

[0046] Figure 5 yes Figure 1 A schematic diagram of another embodiment of a large two-stroke engine with its ammonia fuel system and nitrous oxide reduction system. DETAILED DESCRIPTION

[0047] In the following detailed description, the internal combustion engine will be described with reference to a large two-stroke, low-speed, turbocharged, uniflow scavenged internal combustion engine with a crosshead in an example embodiment, but it should be understood that the internal combustion engine may be of other types. The large two-stroke, low-speed, turbocharged, uniflow scavenged internal combustion engine may be of the (high pressure) type, in which the fuel is injected at or near the top dead center of the piston and compression ignited; the large two-stroke, low-speed, turbocharged, uniflow scavenged internal combustion engine may also be of the (low pressure) type, in which the fuel is mixed with the scavenging air before or during compression and is spark ignited. In the case of spark ignition, a "pilot" ignition will usually be performed with an ignition fluid, such as fuel, to ensure reliable ignition.

[0048] Figure 1 , Figure 2 and Figure 3 A large two-stroke, low speed, turbocharged diesel engine is shown having a crankshaft 8 and a crosshead 9 . Figure 3 A schematic diagram of a large two-stroke low-speed turbocharged diesel engine with its intake system and exhaust system is shown. In this example embodiment, the engine has six cylinders arranged in a row (in line). A large two-stroke low-speed turbocharged diesel engine generally has between four and fourteen cylinders arranged in a row, which are carried by a cylinder frame 23, and the cylinder frame 23 is carried by an engine frame 11. The engine can be used, for example, as a main engine in a ship or as a stationary engine for making a generator in a power station work. The total output of the engine can be, for example, in the range of 1,000 kW to 110,000 kW.

[0049] In this example embodiment, the engine is a two-stroke uniflow dual-fuel compression-ignition engine with scavenging ports 18 in the lower region of the cylinder liners 1 and with a central exhaust valve 4 at the top of each cylinder liner 1. The engine has at least one ammonia mode in which the engine is operated on ammonia fuel or on a fuel based on ammonia and at least one conventional fuel mode in which the engine is operated on conventional fuels such as fuel oil (marine diesel) or heavy fuel oil.

[0050] The scavenging air travels from the scavenging air receiver 2 to the scavenging ports 18 of each cylinder 1. The piston 10 reciprocating between the bottom dead center (BDC) and the top dead center (TDC) in the cylinder liner 1 compresses the scavenging air. When the piston is at or close to TDC, the fuel (ammonia in ammonia mode) is injected into the combustion chamber at high pressure through the fuel valve 50 arranged in the cylinder head 22 (diesel principle), and when the piston travels toward TDC, the fuel (ammonia in ammonia mode) is injected into the combustion chamber at low pressure through the fuel valve 50 arranged in the cylinder head 22 (Otto principle). Combustion then takes place, and exhaust gas is produced. Each cylinder head 22 is provided with two or more fuel valves 50. The fuel valve 50 is configured to inject only one specific type of fuel, such as ammonia, and in this case, two or more fuel valves (not in the cylinder head 22) that inject conventional fuel into the combustion chamber will also be provided. Figure 3). The fuel valve 50 is arranged in the cylinder head 22 around the central exhaust valve 4. In addition, in an embodiment, an additional, usually smaller fuel valve (not shown) is also provided on the cylinder head for injecting an ignition fluid to ensure reliable ignition of the ammonia fuel. The ignition fuel is dimethyl ether (DME) or fuel oil, but it can also be another form of ignition promoter, such as hydrogen. Since the engine can be a dual-fuel engine, the engine can also be provided with a conventional fuel supply system (not shown) for supplying conventional fuel to the fuel valve 50. In an embodiment, a fuel valve 50' is arranged along the cylinder liner (shown by the interrupted line), and the fuel valve 50' allows fuel to enter the cylinder before the piston 10 passes through the fuel valve 50' when it moves from BDC to TDC. Therefore, the piston 10 compresses the mixture of scavenging air and fuel. Timed ignition at or near TDC is triggered by a spark, a laser, an ignition liquid injection, etc. In embodiments with a fuel valve 50', the pressure at which the fuel is admitted is significantly lower than the pressure at which the fuel is injected in embodiments with a fuel valve 50 located in the cylinder head 22, which injects when the piston is at or near top dead center (TDC), and the pressure at which the fuel is injected needs to be significantly higher than the compression pressure. Thus, in embodiments, the engine operates according to the diesel principle (compression ignition) and compresses the scavenging gases, while in other embodiments, the engine operates according to the Otto cycle (timed ignition) and compresses a mixture of fuel and scavenging gases. When operating according to the Otto principle, the pressure at which the fuel supply system 30 needs to deliver the fuel can be significantly lower, and / or a booster commonly used in the fuel valve 50 of a compression ignition engine can be avoided.

[0051] When the exhaust valve 4 is opened, the exhaust gas flows into the exhaust receiver 3 through the exhaust pipe associated with the cylinder and travels through the first exhaust conduit 19 to the turbine 6 of the turbocharger 5 via the optional selective catalytic reactor 33, from which the exhaust gas flows through the condenser 20 via the second exhaust conduit 28 and then flows towards the outlet 21 and into the atmosphere via the wet scrubber 40 and the scrubber tower 48. The wet scrubber 40 reduces nitrous oxide emissions, NOx emissions, as will be described in further detail below.

[0052] Via a shaft, a turbine 6 of the turbocharger 5 drives a compressor 7 which is supplied with fresh air via an air inlet 12. The compressor 7 delivers pressurized scavenging air to a scavenging air duct 13 leading to a scavenging air receiver 2. The scavenging air in the scavenging air duct 13 passes through an intercooler 14 for cooling the scavenging air.

[0053] When the compressor 7 of the turbocharger 5 does not deliver sufficient pressure to the scavenging air receiver 2, i.e. under low or part load conditions of the engine, the cooled scavenging air passes through an auxiliary blower 16 driven by an electric motor 17 which pressurizes the scavenging air flow. At higher engine loads, the compressor 7 of the turbocharger delivers sufficiently compressed scavenging air, and then the auxiliary blower 16 is bypassed via the non-return valve 15 and the electric motor 17 is deactivated. The turbocharging system may include more than one turbocharger 5.

[0054] The engine operates with ammonia as the main fuel in the ammonia mode, and ammonia is supplied to the ammonia valve 50 at a substantially constant pressure and temperature through the ammonia fuel system 30. Ammonia can be supplied to the ammonia valve 50 in a liquid phase or a gas phase. The ammonia liquid phase can be aqueous ammonia (ammonia-water mixture).

[0055] Conventional fuel systems are well known and are not shown and described in more detail. The ammonia fuel system 30 supplies liquid ammonia to the fuel valve 50 at a medium supply pressure (e.g., a pressure of 30 bar to 80 bar). Alternatively, the ammonia fuel is supplied to the ammonia valve 50 in a gas phase and at a relatively low supply pressure (e.g., a pressure of 30 bar to 80 bar). If the engine is a compression ignition type, the fuel valve 50 includes a booster that significantly increases the pressure of the ammonia fuel from a medium pressure to a high pressure to allow the ammonia fuel to be injected at a pressure far higher than the compression pressure of the engine. Typically, the injection pressure for a compression ignition engine is above 300 bar.

[0056] In an embodiment, the engine is provided with an exhaust gas recirculation system for reintroducing a portion of the exhaust gas into the combustion chamber together with scavenging air, for example to reduce the production of NOx.

[0057] Reference Figure 4 , discloses an ammonia fuel system 30 in more detail. Ammonia is stored in a pressurized storage tank 31 in a liquid phase and at a pressure of about 17 bar. Ammonia can be stored in the ammonia storage tank 31 in a liquid phase and at a pressure of more than 8.6 bar and an ambient temperature of 20° C. However, ammonia is preferably stored at a pressure of about 17 bar or higher so that the ammonia remains in a liquid phase when the ambient temperature increases.

[0058] The low-pressure ammonia supply line 32 connects the outlet of the ammonia storage tank 31 with the inlet of the medium-pressure feed pump 35. The low-pressure feed pump 33 forces liquid-phase ammonia from the storage tank 31 to travel to the inlet of the medium-pressure feed pump 35 through the filter arrangement 34. The medium-pressure feed pump 35 forces liquid ammonia to travel to the fuel valves 50, 50' through the medium-pressure ammonia supply line 36. A portion of the liquid ammonia supplied to the fuel valves 50, 50' is injected into the combustion chamber of the engine, and another portion of the liquid ammonia supplied to the fuel valve 50 is returned to the ammonia return line 38, which connects the return port of the fuel valve 50 with the low-pressure supply line 32. Therefore, a portion of the liquid ammonia fuel is recovered to the inlet of the medium-pressure feed pump 35.

[0059] The electronic control unit 100 is connected to the pumps and valves of the fuel system 30, the controlled condenser 20 and the nitrous oxide reduction system via signal lines or wirelessly. The electronic control unit 100 is configured to control these components, for example by regulating the speed of the pump and by controlling the opening and closing of various valves to ensure the operation of the fuel system and the nitrous oxide reduction system, as will be described in more detail below.

[0060] Return to reference Figure 3 , the nitrous oxide reduction system comprises a nitrous oxide scrubber 40, which is located downstream of the turbine 6 and downstream of the controlled condenser 20. The nitrous oxide scrubber 40 is configured to convert nitrous oxide in the exhaust gas flowing through the scrubber 40 into ammonia in a single treatment stage. Therefore, the exhaust gas leaving the scrubber 40 has a significantly reduced content of nitrous oxide compared to the exhaust gas entering the scrubber 40, while the exhaust gas leaving the scrubber 40 has an increased content of ammonia compared to the exhaust gas entering the scrubber 40.

[0061] In an embodiment, the scrubber 40 comprises a packed column that is filled with a material that ensures a high surface area at low pressure loss. In another embodiment, the scrubber comprises a plate column. Regardless of the design of the column, the nitrous oxide removal process will work. However, efficiency and flow may be affected by the type and structure of the column.

[0062] The electroscrubber 40 couples wet scrubbing with an electrogenerated medium to reduce nitrous oxide to ammonia in a single process stage, preferably the electrogenerated medium is a Ni(I) based medium, more preferably the electrogenerated medium is a Ni(I)([Ni(I)(CN)4]3-) medium.

[0063] The medium is mixed with water circulating in the nitrous oxide removal system. Due to the higher pH of the recirculating water, ammonia does not dissolve in the water and leaves the scrubber 40 with the exhaust gas.

[0064] The circulation system circulates water using a circulation pump 45 in a circulation loop 49. The water contains the medium and travels through the scrubber 40.

[0065] The presence of an electrogenerating medium, such as [Ni(I)(CN)4]3-(Ni(I)), in, for example, 9M KOH allows for the continuous removal of nitrous oxide (N2O) from the exhaust gas traveling through the wet scrubber 40 by converting it to ammonia (typically 95% of the nitrous oxide is removed). The process does not require high temperatures and will function at temperatures as low as ambient temperature. The exhaust gas entering the wet scrubber 40 will typically be in the range of between 150°C and 250°C, depending on the operating conditions of the engine and the functioning of the controlled condenser 20.

[0066] Nitrous oxide is removed from the exhaust gas at temperatures as low as ambient temperature by incorporating a mediated electrocatalyst, Ni(I). The mediated electrocatalyst promotes the conversion of N2O to NH 3 Preferably, in the presence of excess nitrogen, the mediated electrocatalyst promotes the conversion of N2O to NH 3 This conversion is achieved by solution phase reaction. This has the following benefits: 3 , NH 3 It can be used as a fuel for engines or as a reducing agent in selective catalytic reactors.

[0067] The medium is an electrogenerated medium, and the circulation system includes an electrolytic cell 44, which is coupled to a voltage source 46 and is used to electrogenerate the medium. The electrolytic cell 44 includes at least two electrodes (anode / cathode) coupled to the voltage source 46. The circulation system also includes a sensor (not shown) for sensing the amount of water in the circulation system.

[0068] A voltage source 46 , a circulation pump 45 , a sensor for sensing the amount of water in the circulation system, and a controllable condenser 20 are connected to the controller 100 .

[0069] Downstream of the scrubber 40, a scrubber tower 48 or other device for separating ammonia from the exhaust gas is arranged, wherein the outlet of the scrubber 40 is connected to the inlet of the scrubber tower 48. The exhaust gas leaving the scrubber tower 48 into the atmosphere via the outlet 21 contains no ammonia or very little ammonia. The ammonia separated from the exhaust gas in the scrubber tower 48 can be used as a fuel for the engine or as a reducing agent in the selective catalytic reactor 33, which can be used to reduce NOx emissions.

[0070] The condenser 20 located downstream of the turbine 6 and upstream of the scrubber 40 removes a portion of the water in the exhaust gas to avoid an increase in the amount of water in the circulation system and reduce the concentration of the medium in the recirculating water. The condenser 20 can preferably be controlled by the controller 100, and the condenser 20 has an outlet for disposing of the water removed from the exhaust gas. The condenser 20 is provided with an inlet for receiving cooling water and an outlet for discharging cooling water. In an embodiment, the temperature and reduced flow rate of the cooling water passing through the condenser 20 are controlled by the controller 100.

[0071] The controller 100 is configured to do one or more of the following:

[0072] - controlling the functioning of the condenser 20, preferably to keep the amount of water in the circulation system constant or to keep the amount of water in the circulation system within limits, in response to a signal, for example from the above-mentioned sensor, representative of the amount of water or fluid in the circulation system; preferably, in response to a signal, for example from the above-mentioned sensor, representative of the amount of water or fluid in the circulation system, by controlling the temperature and / or the flow rate of cooling water passing through the condenser 20, so that there is no evaporation and / or condensation or little evaporation and / or condensation in the scrubber 40;

[0073] the amount of power supplied by the voltage source 46 to the electrolysis cell 44 is controlled, preferably in response to a signal representative of the concentration of the electrogenic medium in the recirculating water; the amount of power supplied by the voltage source 46 to the electrolysis cell 44 is controlled, preferably by a signal from a sensor (not shown) arranged in the circulation system, in response to a signal representative of the concentration of the electrogenic medium in the recirculating water;

[0074] - Controlling the amount and / or pressure of ammonia supplied to the engine by the ammonia fuel system; preferably by regulating the speed of the ammonia feed pump 35 .

[0075] In an embodiment, a method for removing nitrous oxide from the exhaust gas of a large two-stroke turbocharged uniflow scavenged internal combustion engine comprises:

[0076] - Enable the engine to operate with ammonia as the main fuel;

[0077] - Wet scrubbing of the exhaust gas downstream of the turbine 6 of the turbocharger 5 using a Ni(I)-based medium, preferably a Ni(I) ([Ni(I)(CN)4]3-) medium added to water, thereby reducing the nitrous oxide in the exhaust gas to ammonia in a single treatment stage.

[0078] The method may further include: electrogenerating the medium; preferably electrogenerating the medium in an electrolytic cell 44. The method may further include: circulating water containing the medium through a scrubber 40; preferably circulating water containing the medium through the scrubber 40 using a circulation pump 45. The method may further include: separating ammonia from the exhaust gas after wet scrubbing; preferably separating ammonia from the exhaust gas after wet scrubbing using a scrubber tower 48. The method may further include: controlling the water content in the exhaust gas before wet scrubbing; preferably, controlling the water content in the exhaust gas before wet scrubbing by removing water from the exhaust gas, preferably upstream of the turbine 6, preferably using a condenser 20. The method may further include: recirculating water containing the Ni(I)-based medium in a circulation system including the wet scrubber 40. The method may further include: controlling the amount of water in the circulation system before washing by removing water from the exhaust gas; preferably, controlling the amount of water in the circulation system before washing by increasing the function of the condenser when the amount of water in the circulation system is higher than an upper threshold value, and by reducing the function of the condenser when the amount of water in the circulation system is lower than a lower threshold value.

[0079] Figure 5 Another embodiment of the engine is shown. In this embodiment, for simplicity, structures and features that are the same or similar to corresponding structures and features previously described or shown in this document are indicated by the same reference numerals as the reference numerals used previously. In this embodiment, the engine is provided with an electric scrubber 40, which is provided with electrodes connected to a direct current source 46. Water is circulated through the electric scrubber 40 by a circulation pump 45. In an embodiment, the water recirculated through the electric scrubber 40 contains a catalyst. Nitrous oxide in the exhaust gas traveling through the electrodes of the electric scrubber 40 is decomposed into nitrogen and oxygen or into nitrogen and hydroxide by electrolysis. This process can function at temperatures as low as ambient temperature and functions well in the temperature range of 150°C to 250°C where the exhaust gas typically enters the electric scrubber 40.

[0080] In an embodiment, the electrode comprises a mercury electrode, preferably, the mercury electrode is a hanging mercury drop electrode. In this embodiment, in the presence of a small amount of NiII complex of [15 or 14]aneN4{[15 or 14]aneN4=1,4,8,12(or 11)-tetraazacyclopentane(or tetra)decane} in aqueous solution, the reduction of nitrogen oxides occurs at the mercury electrode to obtain only N2 with a yield close to 100%. The macrocyclic polyamines are prepared in a conventional manner, and the metal complexes of the macrocyclic polyamines are obtained by mixing the selected metal ions and the macrocyclic polyamines as ligands in ethanol and / or methanol.

[0081] Alternatively, the reduction of nitrous oxide takes place at a gas diffusion electrode to which platinum and nickel electrocatalysts are added.

[0082] Since no ammonia is produced during the production process, in this embodiment, there is no need to provide a scrubber tower 48 downstream of the electrospray tip 40 to remove ammonia.

[0083] Various aspects and embodiments have been described in conjunction with various embodiments herein. However, other variations to the disclosed embodiments may be understood and effected by those skilled in the art in practicing the claimed subject matter by studying the drawings, the present disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

[0084] The reference signs used in the claims should not be construed as limiting the scope. Unless otherwise indicated, the drawings are intended to be read together with the specification (e.g., section lines, arrangement of components, proportions, extent, etc.), and should be considered part of the entire written description of the present disclosure.

Claims

1. A large two-stroke turbocharged uniflow scavenged internal combustion engine having at least one operating mode in which the primary fuel is ammonia, the engine comprising: - at least one cylinder, the cylinder comprising a cylinder liner (1), a piston (10) located in the cylinder liner (1) and reciprocating, and a cylinder head (22) covering the cylinder; - a combustion chamber formed inside the cylinder between the reciprocating piston (10) and the cylinder head (22); an ammonia fuel system (30) configured to supply pressurized ammonia to a fuel valve (50, 50') arranged in the cylinder head (22) or in the cylinder liner (1); a turbocharger system (5) comprising at least one compressor (7) for compressing scavenging air and at least one turbine (6) driven by exhaust gas, A wet scrubber is arranged downstream of at least one of the exhaust gas driven turbines, characterized in that The wet scrubber is a nitrous oxide scrubber (40) configured to: convert nitrous oxide in the exhaust gas flowing through the nitrous oxide scrubber (40) into ammonia using a Ni(I) based media; and / or, using Ni(I) based macrocyclic polyamines added to water. ll The complex reduces nitrous oxide in the exhaust gas flowing through the nitrous oxide scrubber (40) to nitrogen and oxygen or to nitrogen and hydroxide.

2. The engine according to claim 1, wherein: The nitrous oxide scrubber (40) is an electro-scrubber that couples wet scrubbing with electrically generated said medium to reduce nitrous oxide to ammonia in a single process stage.

3. The engine according to claim 1 or 2, wherein: The media based on Ni(I) is a Ni(I)([Ni(I)(CN)4]3-) media.

4. An engine according to claim 1 or 2, comprising a circulation system which circulates water containing the electrically generated medium through the nitrous oxide scrubber (40).

5. The engine according to claim 4, wherein: The circulation system includes an electrolytic cell (44) coupled to a voltage source (46) for electrically generating the medium.

6. The engine according to claim 5, wherein: The electrolytic cell (44) includes at least two electrodes coupled to the voltage source (46).

7. An engine according to claim 1, comprising a device (48) for separating the ammonia from the exhaust gas, the device (48) for separating the ammonia from the exhaust gas being arranged downstream of the nitrous oxide scrubber (40).

8. The engine according to claim 7, wherein: The means (48) for separating the ammonia from the exhaust gas comprises a scrubber tower.

9. The engine according to claim 5, comprising a condenser (20) located downstream of the turbine (6) and upstream of the nitrous oxide scrubber (40) for removing a portion of the water in the exhaust gas.

10. The engine according to claim 9, wherein: The condenser (20) is a controlled condenser having an outlet for disposing of water removed from the exhaust gas, and having an inlet for receiving cooling water and an outlet for discharging the cooling water.

11. The engine according to claim 1, comprising an ammonia feed pump (35), wherein: The outlet of the ammonia feed pump (35) is fluidly connected to the fuel valve (50, 50').

12. The engine according to claim 11, wherein: The ammonia feed pump (35) has an inlet fluidly connected to the ammonia storage tank (31).

13. The engine of claim 9, comprising a controller (100) configured to do one or more of the following: - in response to a signal representing the amount of water or fluid in the circulation system, controlling the functioning of the condenser (20) so as to keep the amount of water in the circulation system constant; - controlling the amount of power supplied by the voltage source (46) to the electrolytic cell (44); - Controlling the amount and / or pressure of ammonia supplied to the engine by the ammonia fuel system.

14. The engine of claim 9, comprising a controller (100) configured to do one or more of the following: - in response to a signal representing the amount of water or fluid in the circulation system, controlling the functioning of the condenser (20) by controlling the temperature of the cooling water passing through the condenser (20) so as to keep the amount of water in the circulation system constant; - controlling the amount of power supplied by the voltage source (46) to the electrolytic cell (44) in response to a signal representative of the concentration of the medium for electrogeneration in the recycled water; - Controlling the amount and / or pressure of ammonia supplied to the engine by the ammonia fuel system by adjusting the speed of the engine's ammonia feed pump (35).

15. The engine of claim 1, comprising mercury electrodes, and wherein: In the aqueous solution, there is a small amount of [15 or 14]aneN4 {[15 or 14]aneN4 = 1,4,8,12 (or 11)-tetraazacyclopentane (or tetra)decane} Ni II In the case of the complex, the reduction of nitrous oxide takes place at the mercury electrode.

16. A method for removing nitrous oxide from the exhaust gas of a large two-stroke turbocharged uniflow scavenged internal combustion engine having a turbocharging system (5), the method comprising: - operating the engine with ammonia as the main fuel; - wet scrubbing of the exhaust gas downstream of the turbine (6) of the turbocharging system (5), characterized in that the wet scrubbing is carried out using a Ni(I)-based medium added to water, thereby converting the nitrous oxide in the exhaust gas into ammonia in a single treatment stage; or Ni is added to the water using a macrocyclic polyamine downstream of the turbine (6) of the turbocharger system (5). ll The complex wet scrubs the exhaust gas, thereby reducing the nitrous oxide in the exhaust gas to nitrogen and oxygen and / or to nitrogen and hydroxide.

17. The method according to claim 16, wherein: The method comprises wet scrubbing the exhaust gas downstream of a turbine (6) of the turbocharger system (5) using a Ni(I) ([Ni(I)(CN)4]3-) medium added to water, thereby converting nitrous oxide in the exhaust gas into ammonia in a single treatment stage.

18. The method according to claim 16 or 17, comprising: The medium is generated electrically.

19. The method according to claim 18, comprising: The medium is electrogenerated in an electrolytic cell (44).

20. The method according to claim 16 or 17, comprising: The water containing the medium is circulated through a nitrous oxide scrubber (40).

21. The method according to claim 16 or 17, comprising: The ammonia is separated from the exhaust gas after wet scrubbing.

22. The method according to claim 16 or 17, comprising: After wet scrubbing, the ammonia is separated from the exhaust gas using a scrubber tower.

23. The method according to claim 16 or 17, comprising: The water content in the exhaust gas is controlled by removing water from the exhaust gas prior to wet scrubbing.

24. The method according to claim 16 or 17, comprising: The water content in the exhaust gas is controlled prior to wet scrubbing by removing water from the exhaust gas using a condenser (20) upstream of the turbine (6).

25. The method according to claim 24, comprising: The water containing said Ni(I) based medium is recycled in a circulation system comprising a nitrous oxide scrubber (40).

26. The method according to claim 25, comprising: Before washing, the amount of water in the circulation system is controlled by increasing the function of the condenser when the amount of water in the circulation system is higher than an upper threshold value, and by reducing the function of the condenser when the amount of water in the circulation system is lower than a lower threshold value to remove water from the exhaust gas.

27. The method according to claim 16, comprising: In the aqueous solution, there is a small amount of [15 or 14]aneN4 {[15 or 14]aneN4 = 1,4,8,12 (or 11)-tetraazacyclopentane (or tetra)decane} Ni II In the case of the complex, N2O is reduced at the mercury electrode.

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