JP2023129320A - Large two-stroke uniflow scavenged turbocharged internal combustion engine with system for reducing nitrous oxide emission and method for reducing nitrous oxide emission of such engine - Google Patents

Abstract

To reduce nitrous oxide emissions of large two-stroke uniflow scavenged turbocharged internal combustion engines that are fueled with ammonia.SOLUTION: The present invention discloses a large two-stroke uniflow scavenged turbocharged internal combustion engine configured for removing nitrous oxide from an exhaust gas using an electrogenerated mediator in a wet scrubber and a method for removing nitrous oxide from the exhaust gas of a large two-stroke uniflow scavenged turbocharged internal combustion engine by wet electroscrubbing.SELECTED DRAWING: Figure 3

Description

Disclosed herein is a large two-stroke uniflow scavenged turbocharged internal combustion engine having at least one mode of operation using ammonia as a fuel for combustion, which reduces nitrous oxide emissions. The present invention relates to an engine having a system for reducing nitrous oxide emissions and a method for reducing nitrous oxide emissions of such an engine.

background

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

Internal combustion engines have traditionally been operated primarily with hydrocarbon fuels, such as fuel oils such as diesel oil or fuel gases such as 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 byproduct emissions, the generation of _CO2 is inevitable in the combustion of hydrocarbons. The energy density and _CO2 emissions of a particular fuel depend on the length of the hydrocarbon chain and the complexity of the hydrocarbon molecule. Gaseous hydrocarbon fuels therefore emit less _CO2 than liquid hydrocarbon fuels. However, gaseous hydrocarbon fuels are difficult and costly to handle and store. Research into fuels other than hydrocarbons is underway to reduce _CO2 emissions.

Ammonia is a compound obtained from petroleum, biomass, and renewable energy sources (wind, solar, hydropower, geothermal). Ammonia produced using renewable energy sources has virtually zero carbon emissions when combusted and produces no _CO2 , SOx, particulate matter or unburned hydrocarbons.

Ammonia has been tested and used on a small scale in small spark ignition internal combustion engines. However, it has not yet been used to operate compression ignition internal combustion engines.

Engines that use ammonia as fuel tend to generate nitrous oxide (N ₂ O) as a byproduct of combustion. If measures are not taken, exhaust gas containing nitrous oxide will be released into the atmosphere. Nitrous oxide is known to have a global warming potential approximately 265 times greater than _CO2 , according to the United Nations climate report IPPC AR5. Therefore, it is necessary to reduce the nitrous oxide emissions of large two-stroke uniflow scavenged turbocharged internal combustion engines that use ammonia as fuel.

Currently available exhaust gas nitrous oxide removal systems use catalytic decomposition and thermal destruction methods. These methods convert nitrous oxide into nitrogen and oxygen. Catalytic decomposition operates at about 500°C and thermal destruction near 1000°C. The exhaust temperature of a large two-stroke uniflow scavenged turbocharged internal combustion engine depends on the operating conditions, but the exhaust temperature before the turbine is typically 300-500°C, and the exhaust temperature after the turbine is typically 150-500°C. The temperature is 250°C, which is insufficient for use in these known methods. Therefore, catalytic decomposition and thermal destruction are not suitable for removing nitrous oxide from the exhaust gas of large ammonia-fueled two-stroke uniflow scavenged turbocharged internal combustion engines.

DK178072B1 discloses a large two-stroke uniflow scavenged turbocharged internal combustion engine that operates with a first fuel consisting of liquid fuel and a second fuel consisting of ammonia. The engine includes at least one cylinder having a cylinder liner, a reciprocating piston therein, and a cylinder cover, a combustion chamber defined within the cylinder between the reciprocating piston and the cylinder cover, and a combustion chamber disposed in the cylinder cover. an ammonia fuel system configured to supply pressurized ammonia to a fuel valve configured to provide pressurized ammonia; and a turbocharging system having at least one compressor for compressing scavenging air and at least one exhaust gas-driven turbine. . A scrubber is also provided to clean the recirculated exhaust gas before reintroducing it into the combustion chamber. When using low-calorie fuels such as ammonia, NOx emissions can be kept low by increasing the exhaust gas recirculation rate.

Abstract

The objective is to provide a large two-stroke uniflow scavenged turbocharged internal combustion engine that solves or at least alleviates the above-mentioned problems.

The above-mentioned and other objects are solved by the features of the independent claims. More specific implementation forms will become apparent from the dependent claims, the detailed description of the invention, and the drawings.

According to the first approach, a large two-stroke uniflow scavenged turbocharged internal combustion engine is provided that has at least one operating mode in which the main fuel is ammonia. This institution is
- at least one cylinder having a cylinder liner and a reciprocating piston within the cylinder liner, and a cylinder covering the cylinder;
- a combustion chamber formed within the cylinder between the reciprocating piston and the cylinder cover;
- an ammonia fuel system configured to supply pressurized ammonia to a fuel valve disposed on the cylinder cover or the cylinder liner;
- a turbocharging system having at least one compressor for compressing scavenging air and at least one exhaust gas-driven turbine;
- a nitrous oxide scrubber provided downstream of the at least one exhaust gas-driven turbine, the nitrous oxide scrubber converting nitrous oxide in the exhaust gas flowing through the nitrous oxide scrubber into ammonia and/or nitrogen and oxygen or nitrogen and water; a nitrous oxide scrubber that reduces to oxides;
Equipped with

In one example of an implementation of the first perspective, the scrubber is an electroscrubber that combines wet cleaning with an electrogenerated mediator, the mediator being preferably Ni. system, more preferably a Ni(I) [Ni(I)(CN) ₄ ] ^3- mediator, said scrubber converts nitrous oxide to ammonia in one treatment step and/or Alternatively, nitrous oxide in the exhaust gas flowing through the scrubber is reduced to nitrogen and oxygen or nitrogen and hydroxide.

In an example of an implementation of the first perspective, the engine comprises a circulation system for circulating water containing a mediator through a scrubber, the mediator being preferably an electrically generated mediator, and the circulation system comprising: Preferably, the mediator comprises an electrolytic cell coupled to a voltage source for generating electricity, said electrolytic cell preferably having at least two electrodes coupled to said voltage source.

In an example of an implementation of the first perspective, the engine comprises means for separating ammonia from the exhaust gas, the means for separating ammonia from the exhaust gas being arranged downstream of the scrubber, preferably comprising a scrubber tower. are doing.

In an example of an implementation of the first perspective, the engine includes a condenser downstream of the turbine and upstream of the scrubber for removing part of the water in the exhaust gas, the condenser preferably comprising: is a controlled condenser, said condenser preferably having an outlet for discarding the water removed from the exhaust gas, said condenser preferably having an inlet for receiving cooling water and an inlet for discharging the cooling water. It has an outlet.

In one example of an implementation of the first aspect, the engine comprises an ammonia supply pump, an outlet of the ammonia supply pump is fluidly connected to a fuel valve, and the ammonia supply pump preferably supplies fluid to an ammonia storage tank. It has an inlet that is connected to the
In one example of an implementation of the first perspective, the engine includes a controller configured to control one or more of the following:
- Function of the condenser. Control in response to a signal representative of the amount of water or fluid in the circulation system. This is preferably done in order to keep the amount of water in the circulation system constant, and preferably by controlling the temperature of the cooling water passing through the condenser.
- the amount of power supplied to the electrolyzer from the voltage source; Preferably, the control is responsive to an electrically generated signal representative of the concentration of mediator in the recirculated water.
- the amount and/or pressure of ammonia supplied to the engine from the ammonia fuel system; Preferably, this is controlled by adjusting the speed of the ammonia supply pump.

In one example of an implementation of the first perspective, the reduction of nitrous oxide occurs at a mercury electrode in the presence of a small amount of Ni(II) complex in an aqueous solution. This Ni( _II ) complex is composed of Ni( _II ) is a complex.

In one example of an implementation of the first perspective, the reduction of N ₂ O to N ₂ is performed on a gas diffusion electrode modified with a Pt or Ni electrocatalyst.

According to a second aspect, a method is provided for removing nitrous oxide from the exhaust gas of a large two-stroke uniflow scavenged turbocharged internal combustion engine having a turbocharger. This method is
operating said engine with ammonia as the main fuel;
- Exhaust gas downstream of the turbine of a turbocharger is wet-cleaned by adding a Ni-based mediator (preferably Ni(I) [Ni(I)(CN) ₄ ] ^3- mediator) to water to remove nitrogen from the exhaust gas. converting nitrogen oxide to ammonia in a single process step, or
reducing the nitrous oxide to nitrogen and oxygen and/or reducing it to nitrogen and hydroxide using a Ni(II) complex of a macrocyclic polyamine added to water;
including.

In an example implementation of the second perspective, the method includes electrically generating the mediator, preferably in an electrolytic cell.

An example implementation of the second approach includes circulating the water containing the mediator in a scrubber.

In one example of an implementation of the second perspective, the method includes separating ammonia from the exhaust gas, followed by wet cleaning, preferably using a scrubber tower.

In one example of an implementation of the second perspective, the method includes controlling moisture content in the exhaust gas prior to wet cleaning. This is preferably done by removing water from the exhaust gas. Removal of water from the exhaust gas preferably takes place upstream of the turbine 6, preferably using a condenser.

In one example of an implementation of the second perspective, the method includes circulating water containing the Ni-based mediator in a circulation system having a wet scrubber.

An example of an implementation of the second perspective includes controlling the amount of water in the circulation system by removing water from the exhaust gas prior to cleaning. This control preferably activates the condenser when the amount of water in the circulation system is above an upper threshold, and activates the condenser when the amount of water in the circulation system is less than a lower threshold. This is done by reducing the function of the vessel.

In one example of an implementation of the second perspective, the method includes reducing nitrous oxide with a mercury electrode in the presence of a small amount of Ni(II) complex in an aqueous solution. This Ni(II) complex is a Ni(II) complex of [15 or 14]aneN4 {[15 or 14]aneN4=1,4,8,12 (or 11)-tetraazacyclopenta(or tetra)decane} It is.

In one example of an implementation of the second perspective, the method includes reducing N ₂ O to N ₂ on a gas diffusion electrode modified with a Pt or Ni electrocatalyst.

These and other aspects will become clearer from the accompanying drawings and the examples described below.

Various aspects, embodiments, and implementation examples will be described in detail below with reference to exemplary embodiments illustrated in the drawings.
1 is a diagram illustrating a front view of a large two-stroke diesel engine according to an exemplary embodiment; FIG. FIG. 2 is a diagram showing an overview of the large two-stroke engine shown in FIG. 1 when viewed from the rear. 2 is a schematic representation of an embodiment of the large two-stroke engine of FIG. 1 having an ammonia fuel system and a nitrous oxide removal system; 4 is a schematic representation of the engine of the embodiment of FIG. 3 showing the ammonia fuel system in more detail; FIG. 2 is a schematic representation of another embodiment of the large two-stroke engine of FIG. 1 having an ammonia fuel system and a nitrous oxide removal system;

Detailed explanation

In the following detailed description, the internal combustion engine will be described with reference to an exemplary crosshead large low speed two stroke uniflow scavenged turbocharged internal combustion engine. It should be noted that in some cases the internal combustion engine may be another type of engine. Large two-stroke, low-speed, uniflow, scavenged, turbocharged internal combustion engines can be compression ignition (ie, high-pressure) engines in which fuel is injected near or at top dead center of the piston. Alternatively, it can be a spark ignition type (i.e. low pressure type) engine where the scavenging air is mixed with the fuel before or during compression. In the latter case, a pilot ignition is usually performed with an additive liquid (for example, fuel oil) to ensure ignition.

Figures 1-3 depict a large, turbocharged, low speed, two-stroke diesel engine. This engine has a crankshaft 8 and a crosshead 9. FIG. 3 is a schematic representation of a large, turbocharged, low-speed, two-stroke diesel engine with its intake and exhaust systems. In this example, the engine has six cylinders in series. Large, low-speed, turbocharged, two-stroke diesel engines typically have four to fourteen cylinders arranged in series. These cylinders are carried by a cylinder frame 23. The cylinder frame 23 is carried by the engine frame 11. Further, such an engine can be used, for example, as a main engine of a ship or a stationary engine for operating a generator in a power plant. The total power of the engine can be, for example, from 1000 kW to 110 000 kW.

The engine in this embodiment is a two-stroke uniflow compression ignition binary engine, and each cylinder liner 1 is provided with a scavenging port 18 in its lower region, and an exhaust valve is arranged in the center of the top. The engine has at least one ammonia mode and at least one conventional fuel mode. In ammonia mode, the engine is operated on ammonia fuel or ammonia-based fuel. In conventional fuel mode, it is operated with conventional fuel, such as fuel oil (marine diesel fuel) or heavy oil.

Scavenging air is guided through the scavenging air receiver 2 to the scavenging air port 18 of each cylinder 1. The piston 10 reciprocates between bottom dead center (BDC) and top dead center (TDC) in the cylinder liner 1 and compresses scavenging air. Fuel (ammonia in ammonia mode) is injected into the combustion chamber through a fuel valve 50 located in the cylinder cover 22. For operation on the diesel principle, fuel is injected at high pressure when the piston is at or near TDC. In the case of operation based on the Otto principle, fuel is injected at low pressure while the piston is on its way to TDC. Following fuel injection, combustion occurs and exhaust gas is produced. Each cylinder cover 22 is provided with two or more fuel valves 50. Fuel valve 50 may be configured to inject only one particular type of fuel (eg, ammonia). In that case, two or more fuel valves for conventional fuel injection into the combustion chamber would also be provided (not shown in FIG. 3). The fuel valve 50 is arranged in the cylinder cover 22 around the exhaust valve 4 arranged in the center of the cylinder cover 22 . Although not shown, in some embodiments an additional (usually small) fuel valve may be located in the cylinder cover, configured to inject ignition fluid to ensure ignition of the ammonia fuel. The ignition fluid may be, for example, dimethyl ether (DME) or fuel oil. However, other forms of ignition accelerator are also possible, for example hydrogen. Since the engine may be a dual engine, the engine may be equipped with a conventional fuel supply system for supplying conventional fuel to the fuel valve 50 (not shown). In some embodiments, a fuel valve 50' is disposed along the cylinder liner (indicated by dashed lines). The fuel valve 50' introduces fuel into the cylinder while the piston 10 is on its way from BDC to TDC and before passing through the fuel valve 50'. In that case, the piston 10 compresses the scavenging air and fuel mixture. Ignition is timed at or near TDC. Ignition is performed by a spark, laser, injection of ignition fluid, or the like. In embodiments having a fuel valve 50', the pressure at which fuel is introduced is significantly lower than the pressure at which fuel is injected in embodiments having a fuel valve 50 in the cylinder cover 22. Since 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. Thus, in some embodiments, the engine operates according to the diesel principle (compression ignition) and compresses the scavenging gas. In other embodiments, the engine operates according to an Otto cycle (firing at predetermined times) to compress a mixture of fuel and scavenge gas. When operating according to the Otto principle, the pressure required for the fuel supply system 30 to supply fuel can be significantly lower than in the case of compression ignition, and/or the pressure required for the fuel supply system 30 to supply fuel can be significantly lower than in the case of compression ignition, and/or at the fuel valve 50 for compression ignition engines. The need to use the often used pressure boosters can be avoided.

When the exhaust valve 4 is opened, the exhaust gas flows through the exhaust duct provided in the cylinder 1 to the exhaust receiver 3 and through the first exhaust pipe 19 (through the selective catalytic reactor 33 depending on the embodiment); Proceed to the turbine 6 of the turbocharger 5. From there, the exhaust gases proceed through the second exhaust pipe 28, through the condenser 20, the wet scrubber 40, the scrubber tower 48, and are discharged to the atmosphere through the outlet 21. Wet scrubber 40 reduces nitrous oxide emissions (N ₂ O emissions), as described in further detail below.

A turbine 6 of the turbocharger 5 drives a compressor 7 via a shaft. The compressor 9 is supplied with outside air through an air intake 12 . The compressor 7 sends compressed scavenging air to the scavenging pipe 13 connected to the scavenging air receiver 2. The scavenging air from the scavenging pipe 13 passes through an intercooler 14 for cooling the scavenging air.

The cooled scavenging air passes through an auxiliary blower 16 driven by an electric motor 17. The auxiliary blower 16 compresses the scavenging air flow if the compressor 7 of the turbocharger 5 cannot provide sufficient pressure for the scavenging air receiver 2, ie when the engine is at low or part load. When the engine load is high, the turbocharger compressor 7 can supply sufficiently compressed scavenging air, so that the auxiliary blower 16 is bypassed by the check valve 15 and the electric motor 17 is stopped. . The turbocharging system may have two or more turbochargers 5.

In the ammonia mode, the engine is operated with ammonia as the main fuel. Ammonia is supplied by ammonia fuel system 30 to ammonia valve 50 at approximately constant pressure and temperature. Ammonia can be supplied to the ammonia valve 50 in liquid or gas phase. The liquid ammonia may be aqueous ammonia, ie, an aqueous ammonia solution.

Since conventional fuel systems are well known, they are not shown or described in detail. The ammonia fuel system 30 supplies ammonia in liquid phase to the ammonia valve 50 at an intermediate supply pressure (eg 30-80 bar). Alternatively, the ammonia fuel is supplied to the ammonia valve 50 in the gas phase and at a relatively low supply pressure (eg 8-30 bar). For compression ignition engines, the fuel valve 50 includes a pressure booster that significantly increases the pressure of the ammonia fuel. The pressure booster increases the pressure of the ammonia fuel from an intermediate pressure to a high pressure, thereby allowing the ammonia fuel to be injected at a pressure higher than the compression pressure of the engine. Typically, the injection pressure in compression ignition engines is higher than 300 bar.

In some embodiments, the engine includes an exhaust gas circulation system for reintroducing a portion of the exhaust gas into the combustion chamber along with the scavenging gas. This is for example to reduce the generation of NOx.

Referring to FIG. 4, ammonia fuel system 30 is shown in more detail. Ammonia is stored in the liquid phase in a pressure storage tank 31 at approximately 17 bar. Ammonia can be stored in the ammonia storage tank 31 in a liquid phase if the outside temperature is 8.6 bar or higher at 20°C. However, in order to maintain the liquid phase even when the outside temperature rises, it is preferable to store ammonia at 17 bar or higher.

A low pressure ammonia supply line 32 connects the outlet of the ammonia storage tank 31 and the inlet of the medium pressure supply pump 35. Low pressure feed pump 33 applies pressure such that liquid ammonia from tank 31 passes through filter device 34 to the inlet of medium pressure feed pump 35 . The medium pressure supply pump 35 pumps liquid ammonia from the medium pressure ammonia supply line 36 to the fuel valves 50, 50'. A portion of the liquid ammonia supplied to the fuel valve 50 is injected into the combustion chamber of the engine, while another portion is returned to the ammonia return line 38. Ammonia return line 38 connects the return ports of fuel valves 50, 50' to low pressure supply line 32. A portion of the liquid ammonia fuel is therefore recycled to the inlet of the medium pressure supply pump 35.

The electronic control unit 100 is connected by wires or wirelessly to the pumps and valves of the fuel system 30, the controlled condenser 20, and the suboxide removal system. The electronic control unit 100 is configured to control these elements, for example by adjusting the speed of a pump or controlling the opening and closing of a valve. This allows the fuel system and suboxide removal and absorption system to operate as described in detail below.

Return to Figure 3. The nitrous oxide reduction system includes a nitrous oxide scrubber 40 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 one treatment step. Therefore, the exhaust gas exiting the scrubber 40 has a significantly reduced suboxide content compared to the exhaust gas entering the scrubber 40, and the exhaust gas exiting the scrubber 40 has a significantly reduced content of ammonia compared to the exhaust gas entering the scrubber 40. content is increasing.

In some embodiments, scrubber 40 has a packed column. This packed column is packed with a material that provides high surface area and low pressure drop. In some embodiments, the scrubber has a plate column. The nitrous oxide removal process works regardless of column design. However, efficiency and flow rate can be affected by column type and construction.

Electric scrubber 40 combines wet scrubbing and an electrogenerated mediator to reduce nitrous oxide to ammonia in one process step. This mediator is preferably a Ni(I)-based mediator, more preferably a Ni(I) [Ni(I)(CN) ₄ ] ^3- mediator.

The mediator is mixed with water circulating within the nitrous oxide removal device. Since the pH value of the circulating water is high, ammonia is not dissolved in water and is discharged from the scrubber 40 together with the exhaust gas.

The circulation system uses a circulation pump 45 to circulate water in a circulation circuit 49 . The water contains a mediator and passes through the scrubber 40.

The presence of an electrical electronic mediator, e.g. [Ni(I)(CN) ₄ ] ^3- (Ni(I)) in 9M KOH, converts nitrous oxide (N ₂ O) to ammonia. This results in consistent removal (typically 95% removal) of nitrous oxide from the exhaust gas passing through the wet scrubber 40.

The process does not require high temperatures and works at temperatures as low as ambient. The exhaust gases entering the wet scrubber 40 will typically be in the range of 150-250°C, depending on engine operating conditions and the degree of controlled condenser 20 operation.

Nitrous oxide combines with the electrocatalytic mediator Ni(I) and is removed from the exhaust gas, which has cooled to ambient temperature. This mediator electrocatalyst promotes the conversion of N ₂ O to NH ₃ in the presence of excess nitrogen. This conversion is made possible by a solution phase reaction. This has the advantage that _NH3 is produced and can be used as engine fuel or as a reducing agent in selective catalytic reactors.

The mediator is an electrogenerated mediator, and the circulation system has an electrolytic cell 44 coupled to a potential source 46 for electrically generating the mediator. Electrolytic cell 44 has at least two electrodes (anode/cathode) connected to potential source 46 . The circulation system also has a sensor (not shown) for sensing the amount of water within the circulation system.

The potential source 46 , the circulation pump 45 , the sensor for detecting the amount of water in the circulation system, and the controllable condenser 20 are connected to the controller 100 .

A scrubber tower 48 for separating ammonia from exhaust gas is arranged downstream of the scrubber 40, and an outlet of the scrubber 40 is connected to an inlet of the scrubber tower 48. The exhaust gas exiting from scrubber tower 48 through outlet 21 to the atmosphere contains no or very little ammonia. The ammonia separated from the exhaust gas in the scrubber tower 48 can be used as engine fuel or as a reducing agent in the selective catalytic reactor 33, which can be used to reduce NOx emissions.

A condenser 20 located downstream of the turbine 6 and upstream of the scrubber 40 removes a portion of the water in the exhaust gas in order to avoid increasing the amount of water in the circulation system and reducing the concentration of mediator in the recirculating water. remove. The condenser 20 is preferably controllable by the control device 100 and has an outlet for discharging the water removed from the exhaust gas. Condenser 20 also has an inlet for receiving cooling water and an outlet for discharging cooling water. In some embodiments, the temperature and rate of reduction of cooling water through condenser 20 is controlled by controller 100.

The controller is configured to control one or more of the following:
- Capacity of condenser 20. The control is responsive to a signal representative of the amount of water or fluid in the circulation system, such as a signal from the sensor. This is preferably done in order to keep the amount of water in the circulation system constant or within limits, and is preferably done by controlling the temperature and/or flow rate of the cooling water passing through the condenser 20. Here, the temperature and/or flow rate of the cooling water passing through the condenser 20 is controlled such that no or almost no evaporation and/or condensation occurs within the scrubber 40 .
- The amount of power supplied to the electrolyzer 44 from the voltage source 46. Preferably, the control is dependent on a signal representative of the concentration of electrolytic mediator in the recirculated water. This signal is preferably from a sensor (not shown) located within the circulation system.
- The amount and/or pressure of ammonia supplied to the engine from the ammonia fuel system. Preferably, this is controlled by adjusting the speed of the ammonia supply pump 35.

In some embodiments, a method for removing nitrous oxide from the exhaust gas of a large two-stroke uniflow scavenged turbo internal combustion engine includes:
- operating said engine with ammonia as the main fuel;
- Wet cleaning the exhaust gas downstream of the turbine 6 of the turbocharger 5 by adding a Ni(I)-based mediator (preferably Ni(I) [Ni(I)(CN) ₄ ] ^3- mediator) to water. and converting nitrous oxide in the exhaust gas into ammonia in a single processing step;
including.

The method may further include electrogenerating the mediator, preferably in an electrolytic cell 44. The method may further include circulating the water containing the mediator through the scrubber 40, preferably using a circulation pump 45. The method may further include separating ammonia from the exhaust gas, followed by wet scrubbing, preferably using a scrubber tower. The method may further include controlling the moisture content in the exhaust gas prior to wet cleaning. This is preferably done by removing water from the exhaust gas. Removal of water from the exhaust gas preferably takes place upstream of the turbine 6, preferably using a condenser 20. The method may further include circulating water containing a Ni(I)-based mediator through the circulation system having a wet scrubber 40. The method may further include controlling the amount of water in the circulation system by removing water from the exhaust gas prior to cleaning. This control preferably activates the condenser when the amount of water in the circulation system is above an upper threshold, and activates the condenser when the amount of water in the circulation system is less than a lower threshold. This is done by reducing the function of the vessel.

FIG. 5 depicts another embodiment of the engine. In this embodiment, structures and features similar to those already described or illustrated are given the same reference numerals as previously used. In this embodiment, the engine is equipped with an electric scrubber 40 comprising electrodes connected to a DC current source 46. Water is circulated through the electric scrubber 40 by a circulation pump 45. In some embodiments, the water circulated through electric scrubber 40 includes a catalyst. Nitrous oxide in the exhaust gas passing through the electric scrubber 40 is decomposed into nitrogen and oxygen or into nitrogen and hydroxide using electrolysis. Although this process works at temperatures as low as ambient temperature, it works well in the typical temperature range of 150-250° C. where the exhaust gas enters the electric scrubber 40.

In some embodiments, the electrode is a mercury electrode, preferably a hanging mercury drop electrode. In this embodiment, the reduction of nitrous oxide occurs at a mercury electrode, and under the condition of the presence of a small amount of Ni(II) complex in the aqueous solution, only _N2 can be obtained with a yield close to 100%. Here, the above Ni(II) complex is Ni of [15 or 14]aneN ₄ {[15 or 14]aneN ₄ =1,4,8,12 (or 11)-tetraazacyclopenta(or tetra)decane} (II) It is a complex. Macrocyclic polyamines are conventionally prepared, the metal complexes of which are obtained by mixing selected metal ions and macrocyclic polyamines as ligands in ethanol and/or methanol.

Nitrous oxide may also be reduced using a gas diffusion electrode modified with a platinum or nickel electrocatalyst.

Since ammonia is not generated during the manufacturing process, it is not necessary to provide a scrubber tower 48 downstream of the electric scrubber 40 to remove ammonia in this embodiment.

Various conceptions and implementations of the invention have been described along with several examples. However, upon studying the specification, drawings, and claims of this application, those skilled in the art will realize that there are many variations in addition to the described embodiments in carrying out the invention described in the claims. You will be able to understand this and embody it. The use of the words "comprising," "having," and "including" in the claims does not exclude the presence of unstated elements or steps. Even if it is not explicitly stated that there is a plurality of elements recited in the claims, this does not exclude the existence of a plurality of the elements.

Any reference signs used in the claims shall not be construed as limiting the scope of the invention. Unless otherwise noted, the drawings are intended to be read in conjunction with the specification and are a part of the entire disclosure herein.

Claims (16)

A large two-stroke uniflow scavenged turbocharged internal combustion engine having at least one operating mode in which the main fuel is ammonia,
at least one cylinder having a cylinder liner, a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder;
a combustion chamber formed within the cylinder between the reciprocating piston and the cylinder cover;
an ammonia fuel system configured to supply pressurized ammonia to a fuel valve disposed on the cylinder cover or the cylinder liner;
- a turbocharging system having at least one compressor for compressing scavenging air and at least one exhaust gas-driven turbine;
In addition to providing
- a nitrous oxide scrubber provided downstream of the at least one exhaust gas-driven turbine, the nitrous oxide scrubber converting nitrous oxide in the exhaust gas flowing through the nitrous oxide scrubber into ammonia and/or nitrogen and oxygen or nitrogen and water; An engine equipped with a nitrous oxide scrubber that reduces to oxides. The scrubber is an electric scrubber that combines wet cleaning with an electrically generated mediator to reduce nitrous oxide to ammonia in one process step, the mediator preferably being Ni(I) based. The agent according to claim 1, which is a mediator, more preferably a Ni(I)[Ni(I)(CN) ₄ ] ^3- mediator. a circulation system for circulating water containing a mediator through the scrubber, said mediator preferably being an electrically generated mediator, said circulation system preferably having an electrolytic cell coupled to a voltage source for electrically generating said mediator; 3. An engine according to claim 1, wherein the electrolytic cell preferably has at least two electrodes coupled to the voltage source. 4. An engine according to any of claims 1 to 3, comprising means for separating ammonia from exhaust gas, said means being arranged downstream of said scrubber, preferably comprising a scrubber tower. Downstream of the turbine and upstream of the scrubber, a condenser is provided for removing a portion of the water in the exhaust gas, said condenser being preferably a controlled condenser, said condenser preferably removing water from the exhaust gas. Engine according to any of claims 1 to 4, having an outlet for discarding the removed water, said condenser preferably having an inlet for receiving cooling water and an outlet for discharging the cooling water. . Any of claims 1 to 5 comprising an ammonia supply pump, an outlet of said ammonia supply pump being fluidly connected to a fuel valve, said ammonia supply pump preferably having an inlet fluidly connected to an ammonia storage tank. Institutions listed in . The engine according to any one of claims 3, 5 and 6, comprising a controller, the controller comprising:
- controlling the operation of said condenser in response to a signal representative of the amount of water or fluid in said circulation system, preferably to maintain a constant amount of water in said circulation system; , also preferably by controlling the temperature of the cooling water passing through the condenser;
- controlling the amount of power supplied to the electrolyzer from the voltage source, preferably in response to a signal representative of the concentration of an electrically generated mediator in the recirculating water;
- controlling the amount and/or pressure of ammonia supplied to the engine from the ammonia fuel system, preferably by adjusting the speed of the ammonia supply pump 35;
An institution configured to do one or more of the following: A mercury electrode is provided, and the reduction of nitrous oxide occurs at said mercury electrode in the presence of a small amount of Ni(II) complex in aqueous solution, said Ni(II) complex being [15 or 14]aneN ₄ {[15 or 14] aneN ₄ =1,4,8,12 (or 11)-tetraazacyclopenta(or tetra)decane}. A method for removing nitrous oxide from exhaust gas of a large two-stroke uniflow scavenged turbocharged internal combustion engine having a turbocharger, the method comprising:
- operating said engine with ammonia as the main fuel;
Wet cleaning the exhaust gas downstream of the turbine of the turbocharger by adding a Ni(I)-based mediator, preferably a Ni(I)[Ni(I)(CN) ₄ ] ^3- mediator, to water; converting nitrous oxide in the exhaust gas into ammonia in a single process step, or
reducing the nitrous oxide to nitrogen and oxygen and/or reducing it to nitrogen and hydroxide using a Ni(II) complex of a macrocyclic polyamine added to water;
including methods. 10. The method of claim 9, comprising electrogenerating the mediator in an electrolytic cell. 11. A method according to claim 9 or 10, comprising circulating the water containing the mediator through a scrubber. 12. A method according to any of claims 9 to 11, comprising separating the ammonia from the exhaust gas followed by wet scrubbing, preferably using a scrubber tower. controlling the water content in the exhaust gas prior to wet cleaning, said controlling preferably being carried out by removing water from the exhaust gas, said removing preferably being carried out upstream of said turbine. 12. The method according to any of claims 9 to 11, wherein the method is carried out, preferably using a condenser. 13. A method according to any of claims 9 to 12, comprising circulating the water containing the Ni(I)-based mediator in a circulation system having a wet scrubber. controlling the amount of water in said circulation system by removing water from the exhaust gas prior to cleaning, said controlling preferably comprising: controlling the amount of water in said circulation system at or above an upper threshold; 15. According to any one of claims 9 to 14, by activating the condenser in some cases and decreasing the condenser function if the amount of water in the circulation system is below a lower threshold. the method of. reducing nitrous oxide with a mercury electrode in the presence of a small amount of Ni(II) complex in an aqueous solution, said Ni(II) complex being [15 or 14]aneN ₄ {[15 or 14]aneN ₄ =1,4,8,12(or 11)-tetraazacyclopenta(or tetra)decane}. The method according to claim 9, wherein the Ni(II) complex is