Ammonia leak detection method and system for large two-stroke uniflow scavenging turbocharged internal combustion engines, and ammonia leak treatment method and system

Abstract

To early detect and treat ammonia leakage in an ammonia fuel system.SOLUTION: Double-walled pipes 34, 40 have: at least a first inner pipe 35 or a second inner pipe 45; and an outer pipe surrounding the first or second inner pipe, wherein an inter-pipe space 33 is present between the at least first or second inner pipe and the outer pipe, the inter-pipe space 33 is connected at or near a first end of the double-walled pipes 34, 40 to an inlet pipe 26 for taking in air from the atmosphere, the inter-pipe space 33 is connected at or near a second end of the double-walled pipes 34, 40 to an outlet pipe 65 for sending air from the inter-pipe space 33 to the atmosphere, the outlet pipe 65 comprises a unit 66 for mixing steam into air to be discharged, and the outlet pipe 65 comprises a first pH sensor 69 downstream of the unit.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure (hereinafter referred to as the present disclosure) relates to a method and system for detecting an ammonia leak in an ammonia fuel system of a large, two-stroke, uniflow-scavenged, turbocharged, multi-cylinder internal combustion engine having at least one operating mode using ammonia as a secondary primary fuel, and a method and system for treating an ammonia leak and preferably reducing and controlling ammonia emissions in an ammonia fuel system of a large, two-stroke, uniflow-scavenged, turbocharged, multi-cylinder internal combustion engine having at least one operating mode using ammonia as a secondary primary fuel.

[0002] Large two-stroke uniflow scavenged turbocharged internal combustion 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] Internal combustion engines have traditionally been powered primarily by hydrocarbon fuels, such as fuel oils like diesel and fuel gases like natural gas or petroleum gas. Combustion of hydrocarbon fuels results in the production of greenhouse gases, including 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 when hydrocarbons are burned. The energy density and CO2 footprint of a fuel depend on the length of the hydrocarbon chain and the complexity of the hydrocarbon molecule. Therefore, gaseous hydrocarbon fuels emit less CO2 than liquid hydrocarbon fuels. However, gaseous hydrocarbon fuels are difficult and expensive to handle and store. Research into non-hydrocarbon fuels is ongoing to reduce CO2 emissions.

[0004] Ammonia is a compound derived from petroleum, biomass, and renewable energy sources (wind, solar, hydroelectric, and geothermal). Ammonia produced using renewable energy sources has virtually zero carbon emissions when burned, emitting no CO2, SOx, particulate matter, or unburned hydrocarbons.

[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 operate a compression-ignition internal combustion engine.

[0006] Ammonia is harmful and has a pungent odor. Therefore, ammonia leaks from engines must be avoided and must be detected as quickly as possible, ideally within two minutes. Therefore, a solution is needed that can detect ammonia leaks early and provide a way to deal with them.

[0007] Furthermore, when ammonia fuel operation is discontinued and operation is switched to conventional fuel, for example, the ammonia in the fuel system must be purged (removed), but the purged ammonia cannot simply be discharged into the atmosphere / ambient, so a system must be installed to process this considerable amount of ammonia.

[0008] KR20230104327A discloses a double-pipe system for a ship, its installation method, and a method for discharging ammonia using the system. This document describes that the fuel supply line and fuel return line installed in the engine room of a ship that uses ammonia as fuel are double-piped to deal with ammonia leaks, and that the double pipes at the rear end on the fuel preparation room and engine side are pressurized double pipes to prevent leaked ammonia from leaking into the fuel preparation room and engine. Abstract

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

[0010] These and other problems are solved by the features of the independent claims. More specific implementations will become apparent from the dependent claims, the description and the drawings.

[0011] According to a first aspect, a system is provided for detecting an ammonia leak in an ammonia fuel system of a large, two-stroke, uniflow-scavenged, turbocharged, multi-cylinder internal combustion engine having at least one operating mode using ammonia as a primary fuel. The system has double-walled piping, the double-walled piping is for supplying ammonia to a fuel valve of the engine through a first inner pipe of the double-walled piping and / or returning excess ammonia from the fuel valve of the engine through a second inner pipe of the double-walled piping; the double-walled piping has at least the first inner pipe or the second inner pipe and an outer pipe surrounding the first or second inner pipe, and an inter-pipe space exists between the at least first or second inner pipe and the outer pipe; the inter-pipe space is connected to an intake pipe at or near a first end of the double-walled pipe for taking in air from the atmosphere; the inter-tube space is connected to an exhaust pipe at or near a second end of the double-walled piping for delivering air from the inter-tube space to the atmosphere; the discharge pipe comprises a unit for mixing water vapor with the air being discharged; The outlet line includes a first pH sensor downstream of the unit.

[0012] If an ammonia leak results in the presence of ammonia in the exhaust air stream, adding a water vapor stream to the exhaust air stream will affect the pH of the resulting mixture. Therefore, if ammonia is present in the exhaust air, the pH of the mixture measured downstream of the point where the water vapor is added will be high. Therefore, a pH sensor can be used to detect ammonia in the exhaust air early. Dedicated ammonia sensors typically only measure ammonia concentrations in the range of 100–5000 PPM. Exposure to ammonia concentrations above 5000 PPM, which is likely to occur during an ammonia leak, will saturate the sensor, rendering it inoperable for at least 24 hours. Therefore, the ability to use a pH sensor instead of a dedicated ammonia sensor is a significant advantage. Furthermore, the slow response of existing dedicated ammonia sensors can delay response after detecting an ammonia leak.

[0013] In one example implementation of the first aspect, the system includes a blower in the exhaust pipe to draw airflow from the atmosphere into the inter-tube space and to draw air from the inter-tube space to draw exhaust flow or air into the exhaust pipe.

[0014] In one example implementation of the first aspect, the system includes a controller connected to the first pH sensor, the controller configured to monitor the pH sensed by the first pH sensor.

[0015] In one example implementation of the first aspect, the first pH sensor is configured to emit a signal representative of the measured pH, and the system includes a controller that receives the signal from the first pH sensor.

[0016] In one implementation of the first aspect, the system includes a fuel pump for supplying a flow of ammonia to the first inner pipe, and the controller is configured to issue a signal to stop operation of the fuel pump to terminate the supply of ammonia to the inner pipe when it determines that ammonia has leaked into the inter-pipe space. Preferably, the controller is configured to issue a signal to switch engine operation to an alternative fuel.

[0017] In one example of an implementation of the first aspect, the system includes a valve in the intake pipe, and the control unit is configured to close the valve to prevent or at least throttle the intake of fresh air into the inter-pipe space when it determines that ammonia has leaked into the inter-pipe space.

[0018] In one implementation of the first aspect, the system includes a container in the exhaust pipe for absorbing ammonia in the exhaust air into an aqueous solution, the container preferably being located downstream of the first pH sensor.

[0019] In one implementation of the first aspect, the system includes an acid source for adding acid to the aqueous solution and a second pH sensor configured to sense a pH of the aqueous solution, and the controller is preferably connected to the acid source and configured to add acid from the acid source to the aqueous solution as a function of the sensed pH of the aqueous solution, preferably when the sensed pH of the aqueous solution exceeds a threshold value.

[0020] In one implementation of the first aspect, the system includes a detection system for detecting a density of the aqueous solution, and the controller is connected to the detection system and configured to determine that the aqueous solution needs to be replaced with fresh aqueous solution when the detected specific density of the aqueous solution or the total weight of the aqueous solution in the container exceeds a threshold value.

[0021] In one implementation of the first aspect, the system includes a wet scrubber downstream of the vessel for removing ammonia vapor from the exhausted air.

[0022] In one example implementation of the first aspect, the aqueous solution from the container is supplied to the wet scrubber and returned to the container after passing through the wet scrubber.

[0023] In one example implementation of the first aspect, a third pH sensor is configured to sense the pH of the aqueous solution returning from the wet scrubber.

[0024] In one implementation of the first aspect, the system includes an ammonia concentration sensor, preferably an infrared sensor or a catalytic sensor, downstream of the wet scrubber.

[0025] According to a second aspect, there is provided a large, two-stroke, uniflow-scavenged, turbocharged, multi-cylinder internal combustion engine having at least one mode of operation using ammonia as a primary fuel, the engine comprising: at least one 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 between the reciprocating piston and the cylinder cover; an ammonia fuel system configured to supply pressurized ammonia to a fuel valve disposed in the cylinder cover or the cylinder liner; a system according to the first aspect and possible implementations thereof; Includes.

[0026] In one implementation of the first aspect, the ammonia fuel system includes a supply line and a return line, and the piping forming the supply line and the return line comprises double-walled piping.

[0027] According to a third aspect, there is provided a method for detecting an ammonia leak in an ammonia fuel system of a large, two-stroke, uniflow-scavenged, turbocharged, multi-cylinder internal combustion engine having at least one operating mode using ammonia as a primary fuel, the method comprising: the engine has an ammonia fuel system; the ammonia fuel system comprises double-walled piping for supplying ammonia to a fuel valve of the engine through a first inner pipe of the double-walled piping and / or for returning excess ammonia from the fuel valve of the engine through a second inner pipe of the double-walled piping; the double-walled piping has at least the first inner pipe or the second inner pipe, and an outer pipe surrounding the first or second inner pipe, and the method further comprises: introducing an air flow from the atmosphere into an inter-tube space between the at least first or second inner tube and the outer tube at or near a first end of the double-walled pipe; Discharging the air flow from the inter-pipe space to atmosphere at or near the other end of the double-walled piping; mixing a stream of water vapor with the exhausted air stream to form an aqueous solution of ammonia so as to dissolve at least a portion of the ammonia in the exhausted air; measuring the pH of the resulting exhaust gas and water vapor mixture; Includes.

[0028] In one example implementation of the third aspect, the method includes issuing a signal that an ammonia leak has been detected if the measured pH exceeds a threshold, preferably higher than the pH of a water vapor stream mixed with the exhaust air stream by a certain margin.

[0029] In one example implementation of the third aspect, the method includes aspirating an intake air flow into the inter-tube space and aspirating an exhaust air flow from the inter-tube space by drawing air by suction, preferably using a blower downstream of the inter-tube space.

[0030] In one example implementation of the third aspect, the method includes supplying a flow of ammonia to the first inner tube and terminating the supply of ammonia to the first inner tube when an ammonia leak is detected, and preferably also includes switching the engine to alternative fuel operation.

[0031] In one example implementation of the third aspect, the method includes preventing or at least restricting the intake of fresh air into the inter-tube space if an ammonia leak is detected.

[0032] In one implementation of the third aspect, the method includes absorbing ammonia into an aqueous solution in a vessel downstream from a location where the pH is measured.

[0033] In one implementation of the third aspect, the method includes adding an acid to the aqueous solution, the acid preferably including one or more of sulfuric acid, citric acid, phosphoric acid, and hydrochloric acid.

[0034] In one implementation of the third aspect, the method includes scrubbing the exhausted air with a scrubber located downstream of the vessel.

[0035] In one example implementation of the third aspect, the method includes measuring the ammonia content in the exhaust gas downstream of the scrubber, preferably with a fourth pH sensor or an infrared sensor or a catalytic sensor.

[0036] In one example implementation of the third aspect, the method includes terminating ammonia-based operation when ammonia content detected in exhaust downstream of the scrubber exceeds a threshold.

[0037] In one example implementation of the third aspect, the method includes determining a specific density of the aqueous solution or a total weight of the container and the aqueous solution, and replacing the aqueous solution when the specific density of the aqueous solution exceeds a threshold value or when the total weight of the aqueous solution exceeds a threshold value.

[0038] According to a fourth aspect, there is provided a method of addressing an ammonia leak in a fuel system of a large, two-stroke, uniflow-scavenged, turbocharged, multi-cylinder internal combustion engine having at least one operating mode using ammonia as a primary fuel, the method comprising: the engine has an ammonia fuel system; the ammonia fuel system comprises double-walled piping for supplying ammonia to a fuel valve of the engine through a first inner pipe of the double-walled piping and / or for returning excess ammonia from the fuel valve of the engine through a second inner pipe of the double-walled piping; the double-walled piping has at least the first inner pipe or the second inner pipe, and an outer pipe surrounding the first or second inner pipe, and the method further comprises: introducing a flow of fresh air from the atmosphere into an inter-pipe space between at least the first or second inner pipe and the outer pipe at or near a first end of the double-walled pipe; Discharging the air flow from the inter-tube space at or near the other end of the double-walled piping; measuring the ammonia concentration in the discharged air stream; Absorbing ammonia in the exhausted air in an aqueous solution in a container downstream from a location where the ammonia concentration of the exhausted air is measured; sensing the pH of the aqueous solution; adding an acid to the aqueous solution to protonate NH3 under the formation of ammonium hydroxide, and maintaining the pH of the aqueous solution at a predetermined level; determining the density of the aqueous solution (preferably in a wet scrubber) and replacing the aqueous solution (preferably with fresh water) when the determined density exceeds a threshold value; Includes.

[0039] By adding acid to the solution to maintain the desired pH, the density of the solution will increase over time, and by measuring and determining the specific gravity of the supernatant liquid and the increase in weight of the solution in the container, it is possible to determine when the solution is approaching saturation and needs to be replaced.

[0040] According to a fifth aspect, there is provided a method of addressing an ammonia leak in a fuel system of a large, two-stroke, uniflow-scavenged, turbocharged, multi-cylinder internal combustion engine having at least one operating mode using ammonia as a primary fuel, the method comprising: the engine has an ammonia fuel system; the ammonia fuel system comprises double-walled piping for supplying ammonia to a fuel valve of the engine through a first inner pipe of the double-walled piping and / or for returning excess ammonia from the fuel valve of the engine through a second inner pipe of the double-walled piping; The double-walled piping has at least a first inner pipe or the second inner pipe, and an outer pipe surrounding the at least first or second inner pipe, and the method further comprises: Intake a fresh air flow from the atmosphere through an intake pipe into an inter-pipe space between the at least first or second inner pipe and the outer pipe at or near a first end of the double-walled pipe; Discharging the air flow from the inter-tube space at or near the other end of the double-walled piping; facilitating a flow of intake air through the intake pipe into the inter-tube space, preferably using a blower in the discharge pipe, and drawing an exhaust air flow from the inter-tube space through the exhaust pipe by drawing air by suction; measuring ammonia concentration in the exhaust air stream to detect whether ammonia has leaked into the inter-tube space; if an ammonia leak is detected, blocking or at least throttling air flow through said intake tube while continuing to draw air by suction; Includes.

[0041] By shutting off the air flow through the intake pipe when an ammonia leak is detected, the ammonia flow rate to the downstream ammonia treatment system, e.g., a wet scrubber, is reduced, thereby reducing the demand on the capacity of the downstream treatment system to process the ammonia stream, resulting in space and cost savings.

[0042] These and other aspects will be more apparent from the examples described below. [Brief explanation of the drawings]

[0043] Various aspects, embodiments, and implementations will be described in detail below with reference to exemplary embodiments shown in the drawings. [Figure 1] 1 shows a front view of a large two-stroke diesel engine according to an exemplary embodiment; FIG. [Figure 2] Figure 1 shows an overview of the large two-stroke engine as seen from the rear. [Figure 3] 2 is a schematic representation of the large two-stroke engine of FIG. [Figure 4] 1 is a schematic representation of an engine according to a first embodiment, the engine having an ammonia fuel system, an ammonia leak detection system, and an ammonia leak treatment system. [Figure 5] 1 is a schematic representation of an engine according to a second embodiment, also having an ammonia fuel system, an ammonia leak detection system, and an ammonia leak treatment system. Detailed explanation

[0044] In the following detailed description, the internal combustion engine will be described with reference to an exemplary crosshead-type, large, slow-speed, two-stroke, uniflow-scavenged, turbocharged internal combustion engine. Note that in some cases, the internal combustion engine may be of another type. A large, two-stroke, slow-speed, uniflow-scavenged, turbocharged internal combustion engine may be a compression-ignition (i.e., high-pressure) engine, in which fuel is injected near or at top dead center of the piston. Or, it may be a spark-ignition (i.e., low-pressure) engine, in which scavenging air is mixed with fuel before or during compression. In the latter case, a pilot ignition with an additive (e.g., fuel oil) is usually used to ensure ignition.

[0045] 1-3 illustrate a turbocharged, large, slow-speed, two-stroke diesel engine. The engine has a crankshaft 8 and a crosshead 9. FIG. 3 is a schematic representation of a turbocharged, large, slow-speed, two-stroke diesel engine, along with its intake and exhaust systems. In this embodiment, the engine has six cylinders arranged in series. Turbocharged, large, slow-speed, two-stroke diesel engines typically have four to fourteen cylinders arranged in series. These cylinders are supported on a cylinder frame 23, which is supported on an engine frame 11. Such an engine can also be used, for example, as a main engine on a ship or as a stationary engine for driving a generator in a power plant. The total power output of the engine can be, for example, in the range of 1,000 to 110,000 kW.

[0046] The engine of this embodiment is a two-stroke uniflow compression ignition dual-fuel engine. Each cylinder liner 1 has a scavenging port 18 in its lower region and an exhaust valve at the top center. The engine has at least one ammonia mode and at least one conventional fuel mode. In the ammonia mode, the engine operates on ammonia fuel or an ammonia-based fuel. In the conventional fuel mode, the engine operates on conventional fuels, such as fuel oil (marine diesel fuel) or heavy oil.

[0047] Scavenging air is introduced into 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 air. Fuel (ammonia in the ammonia mode) is injected into the combustion chamber in the cylinder liner 1 at or near TDC through multiple (high-pressure) fuel valves 49 located in the cylinder cover 22. Following fuel injection, combustion occurs and exhaust is generated. Two or more fuel valves 49 are provided in each cylinder cover 22. The fuel valves 49 may be configured to inject only one specific type of fuel (e.g., ammonia). In that case, two or more fuel valves for injecting conventional fuel into the combustion chamber may also be provided (not shown). Therefore, in such a case, the engine would have four or more fuel valves. If the fuel valves 49 are configured to inject both ammonia and conventional fuel, the number of fuel valves 49 provided in each cylinder may be two or more. The fuel valve 49 is located on the cylinder cover 22 around the exhaust valve 4, which is located in the center of the cylinder cover 22. Although not shown, in some embodiments, the cylinder cover may include an additional (usually small) fuel valve 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 accelerators, such as hydrogen, may also be used. Since the engine may be a dual-fuel engine, the engine may include a conventional fuel supply system (not shown) for supplying conventional fuel to the fuel valve 49. In some embodiments, a fuel valve 49' is located along the cylinder liner (shown in dashed lines). The fuel valve 49' introduces fuel into the cylinder liner as the piston 10 moves from BDC to TDC before passing the fuel valve 49'. The piston 10 then compresses the scavenging air / fuel mixture. Ignition is timed at or near TDC. Ignition can be achieved by a spark, laser, injected ignition fluid, or the like. In the embodiment with fuel valve 49', the pressure at which fuel is introduced is significantly lower than the pressure at which fuel is injected in the embodiment with fuel valve 49 in cylinder cover 22.As a result, the pressure required for the fuel supply system 30 to deliver fuel may be significantly lower and / or the pressure booster often used with fuel valves 49 located on the cylinder cover 22 may not be necessary.

[0048] When the exhaust valve 4 opens, the exhaust flows through an exhaust duct in the cylinder 1 to an exhaust receiver 3, then through a selective catalytic reduction reactor (SCR reactor) 28, through a first exhaust pipe 19 and on to the turbine 6 of the turbocharger 5. From there, the exhaust flows through a second exhaust pipe 25 to an economizer 20 and then out an outlet 21 into the atmosphere. The SCR reactor reduces emissions in the exhaust, particularly NOx emissions.

[0049] The turbine 6 drives the compressor 7 via a shaft. Outside air is supplied to the compressor 9 through an air intake 12. The compressor 7 sends compressed scavenging air into a scavenging pipe 13 connected to the scavenging air receiver 2. The scavenging air in the scavenging pipe 13 passes through an intercooler 14 to cool the scavenging air.

[0050] 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 when the compressor 7 of the turbocharger 5 cannot provide sufficient pressure for the scavenging air receiver 2, i.e. when the engine is at low or partial load. When the engine load is high, the turbocharger compressor 7 can provide sufficiently compressed scavenging air, so the auxiliary blower 16 is bypassed by the check valve 15 and the electric motor 17 is switched off.

[0051] In ammonia mode, the engine is operated using ammonia as the primary fuel. Ammonia is supplied to the ammonia valves 30, 30' at a substantially constant pressure and temperature. Ammonia can be supplied to the ammonia valves 49, 49' in either the liquid or gas phase. Liquid ammonia can be aqueous ammonia, i.e., an aqueous ammonia solution.

[0052] Conventional fuel systems are well known and are not shown or described in detail. The ammonia fuel system 30 supplies ammonia in liquid phase at an intermediate supply pressure (e.g., 30-80 bar) to the ammonia valves 49, 49'. Alternatively, the ammonia fuel is supplied in vapor phase to the ammonia valves 449, 49' at a relatively low supply pressure (e.g., 8-30 bar). In the case of a compression ignition engine, the fuel valves 49, 49' include a pressure booster that significantly increases the pressure of the ammonia fuel. The pressure booster increases the pressure of the ammonia fuel from intermediate pressure to high pressure, thereby allowing the ammonia fuel to be injected at a pressure higher than the engine compression pressure. Typically, the injection pressure of a compression ignition engine is greater than 300 bar.

[0053] Referring to FIG. 4, the early ammonia leak detection and treatment system is shown in more detail.

[0054] Ammonia is stored in liquid phase at approximately 17 bar in pressurized storage tank 36. Ammonia can be stored in liquid phase in ammonia storage tank 36 at a pressure of 8.6 bar or higher at an ambient temperature of 20°C. However, it is preferred to store ammonia at a pressure of 17 bar or higher to maintain the liquid phase even as the ambient temperature increases.

[0055] A low-pressure ammonia supply line 32 connects the outlet of the ammonia storage tank 36 to the inlet of the medium-pressure feed pump 32. The medium-pressure feed pump 32 pumps liquid-phase ammonia from the medium-pressure ammonia supply line 31 to a valve train formed by fuel valves 49, 49′. A portion of the liquid-phase ammonia supplied to the valve train is injected into the combustion chamber of the engine, while another portion is returned to the ammonia return line 45. An ammonia return line 38 connects the return port of the fuel valve to the low-pressure supply line 39. Thus, a portion of the liquid-phase ammonia fuel is recirculated to the inlet of the medium-pressure feed pump 32.

[0056] When operation on ammonia fuel is discontinued, such as due to a failure of the ammonia fuel system 30, an ammonia leak, or another reason for switching to conventional fuel, the control unit 50 directs the ammonia fuel system 30 to be purged to remove ammonia from the system and to switch engine operation to another fuel, such as marine diesel fuel.

[0057] The ammonia fuel system includes double-walled piping 34, 40. The double-walled piping 34, 40 supplies ammonia to an engine fuel valve 49, 49′ through a first inner pipe 35 of the double-walled piping 34, 40, and returns excess ammonia from the engine fuel valve 49, 49′ through a second inner pipe 45 of the double-walled piping 34, 40. The double-walled piping 34, 40 includes a first inner pipe 35 and a second inner pipe 45, and an outer pipe surrounding the first inner pipe 35 or the second inner pipe 45. An inter-pipe space 33 exists between the first inner pipe 35 or the second inner pipe 45 and the outer pipe. The first inner pipe 45 is part of the ammonia supply line 31, and the second inner pipe 45 is part of the ammonia return line 39. In some embodiments, a single inter-pipe space 33 surrounds the first inner pipe 35 and the second inner pipe 45. In another embodiment, there is an inter-tube space 33 surrounding the first inner tube 35 and another inter-tube space 33 surrounding the second inner tube 45 .

[0058] The inter-tube space 33 is connected at or near a first end of the double-walled piping 40 to an intake pipe 26 for taking in air from the atmosphere. The inter-tube space 33 is connected at or near a second end of the double-walled piping 34, 40 to an exhaust pipe 65 for delivering air from the inter-tube space 33 to the atmosphere.

[0059] The engine room 48 is shown diagrammatically in dashed lines, and the double-walled piping 34, 40 extends along the first and second inner pipes 35, 45, at least to the extent that it is located within the engine room 48, to prevent ammonia from entering the engine room.

[0060] A blower 61 is provided in the discharge pipe 65 for drawing an air flow from the atmosphere into the inter-tube space 33 via the intake pipe 26 and for drawing an exhaust flow or air from the inter-tube space 33 by drawing the air by suction into the discharge pipe 66. A second blower 61' is also provided for redundancy.

[0061] The discharge pipe 65 is provided with a unit 66 for mixing water vapor into the discharged air, which may comprise an absorber or, as shown, a wet scrubber or the like.

[0062] When ammonia gas in the exhausted air (which originates from leakage into the inter-tube space 33 from the first or second inner tube 35, 45) mixes with the water vapor in the unit 66, the ammonia dissolves in the water, forming an aqueous solution of ammonia. This process is a physical change known as dissolution. Chemically, ammonia (NH3) is a base, and when dissolved in water, it reacts to some extent with the water molecules to form ammonium ions (NH4 + ) and hydroxide ions (OH - )

[0063] The reaction can be expressed as follows: NH3(g) + H2O(l) ⇔ NH4 + (aq) + OH - (aq)

[0064] Ammonia therefore acts as a weak base in water. The extent of this reaction depends on the concentration of ammonia and the temperature. In aqueous solution, only a small proportion of ammonia molecules actually react to form ammonium and hydroxide ions.

[0065] Hydroxide ion (OH - The presence of ) makes the solution basic (or alkaline), which can be detected using a pH indicator or pH sensor.

[0066] Thus, when exhaust gas containing ammonia gas is mixed with water vapor, a basic solution is formed due to the weakly basic properties of ammonia.

[0067] The discharge pipe 65 is equipped with a first pH sensor 69 downstream of the unit 66. The first pH sensor is therefore able to detect an increase in the pH of the exhaust air and water mixture passing through the first pH sensor 65 when ammonia is present in the discharged air.

[0068] Preferably, the first pH sensor 69 is configured to emit a signal representative of the measured pH, and the control unit 50 receives the signal from the first pH sensor, for example via a signal line or by wireless connection.

[0069] The control unit 50 is configured to determine that ammonia has leaked into the inter-tube space 33 as a function of the detected pH. For example, it is configured to determine that ammonia has leaked when the pH detected by the first pH sensor 69 exceeds a threshold value, preferably when the measured pH is higher by a certain margin than the pH of the water vapor flow mixed with the exhaust air flow.

[0070] A container 70 is also disposed in the discharge pipe 65. The container 70 is for absorbing ammonia in the discharged air into an aqueous solution 73. The container 70 is disposed downstream of the first pH sensor 69.

[0071] An acid source 72 is provided for adding acid to the aqueous solution 73. A second pH sensor 77 is also provided, configured to sense the pH of the aqueous solution 73 in the container 70. The controller 50 is preferably connected to the acid source 72 and configured to add acid from the acid source 72 to the aqueous solution 73 as a function of the sensed pH of the aqueous solution 73. Preferably, the controller 50 is configured to add acid when the sensed pH of the aqueous solution exceeds a threshold value. The acid preferably includes one or more of sulfuric acid, citric acid, phosphoric acid, and hydrochloric acid.

[0072] A sensing system 74 is also provided for sensing the density of the aqueous solution 73. In the illustrated embodiment, this sensing system is a density sensor 74 connected to the container 72. The density sensor 74 can be, for example, a commercially available resonant tuning fork densitometer. Alternatively, the density can be determined by measuring the pressure within the container 70 at two separate height positions and deriving the density from the pressure difference between the two positions.

[0073] The control unit 50 is preferably connected to a density sensor 74, and is configured to determine that the aqueous solution 73 needs to be replaced with fresh aqueous solution 73 when the detected specific gravity of the aqueous solution 73 exceeds a threshold value. Preferably, the aqueous solution 73 is replaced with fresh water.

[0074] Downstream 75 of vessel 70 is a wet scrubber for removing ammonia vapor from the exhaust air. Aqueous solution 73 is pumped into wet scrubber 75 by pump 71 through solution line 76 and flows downward by gravity back to vessel 70 through packing 78 in wet scrubber 75. The bottom of wet scrubber 75 opens to the top of vessel 70. The pH of the aqueous solution returning to vessel 70 is measured by a third pH sensor 81. This value is suitable information for determining the amount of acid that needs to be added to the aqueous solution and vessel 70.

[0075] In some embodiments, the controller 50 is configured to terminate ammonia-based engine operation if the ammonia content detected in the exhaust air downstream of the scrubber 75 exceeds a threshold value.

[0076] The demister 79 removes excess moisture from the air before it is exhausted through the remainder of the exhaust pipe 65 to the atmosphere.

[0077] An ammonia concentration sensor 80 is located downstream of the wet scrubber 75 to ensure that the air discharged to the atmosphere does not contain excessive ammonia or levels above acceptable levels (typically, a maximum of 20 ppm is permitted to be discharged to the atmosphere). The ammonia sensor 80 is an infrared sensor, a commercially available infrared gas detector that uses infrared absorption technology to detect the presence of ammonia gas. An example of this type of commercially available sensor is the E12-15 IR Optical supplied by Analytical Technology. Such sensors are typically capable of detecting ammonia concentrations between 100 and 5000 ppm. Alternatively, the ammonia concentration sensor 80 may be a catalytic type, such as the OLCT 100-XP233-5 catalytic sensor supplied by Teledyne Oldham Simtronics.

[0078] The control unit 50 uses a signal from an ammonia sensor 80 downstream of the wet scrubber 75 to maintain the second pH sensor of the wet scrubber 75 below a certain threshold, for example 7, thereby ensuring the efficiency of the wet scrubber 75.

[0079] In some embodiments, the system includes an adjustable throttle valve 25 in the intake conduit 26. During normal operation, the adjustable throttle valve is fully open, providing no substantial restriction to the flow of intake air through the intake conduit 26. The control unit 50 is configured to close the adjustable throttle valve 25 to prevent or at least throttle the intake of fresh air into the inter-tube space 33 if the control unit 50 determines that ammonia has leaked into the inter-tube space 33, while continuing to draw air through suction by the blower 61. The control unit 50 is preferably configured to first fully close the adjustable throttle valve 25 when a leak is detected, and then slightly open the throttle valve 25 so that the throttle valve 25 provides a significant restriction to the flow of intake air through the intake conduit 26. This valve closure and the subsequent reduction in intake air flow significantly reduces the flow of ammonia to the discharge conduit 65, and accordingly, the ammonia treatment system requires a much smaller capacity to remove ammonia from the exhaust air, thereby saving cost and space.

[0080] FIG. 5 discloses another embodiment of an ammonia leak detection and treatment system. In this embodiment, components and features similar to those already described or illustrated are designated by the same reference numerals previously used. This embodiment is essentially the same as the embodiment shown in FIG. 4, except for the system for determining the specific density of the aqueous solution 73. In this embodiment, the specific density is determined by a load cell 91 that senses the weight of the container 73 containing the aqueous solution. The load cell 91 signals a control unit 50 that records the weight gain due to the added acid and, accordingly, determines when the aqueous solution needs to be replaced. Furthermore, instead of a variable throttle valve, two control valves 25 and 25' are provided in the intake pipe 26. When an ammonia leak is detected, these valves selectively close the intake air flow and selectively force the intake air through an orifice 24, which provides a substantial restriction to the intake air flow, thereby reducing the flow of ammonia to the discharge pipe 65, allowing the use of a smaller-capacity ammonia treatment system.

[0081] Also, in this embodiment, the acid is added to the aqueous solution stream supplied to the wet scrubber 75. Controlling the pH of the aqueous solution in this manner allows for rapid detection and rapid change of the pH value of the water supplied to the wet scrubber 75. The water in the vessel 73 does not reach very low pH values, which can occur with a control strategy that directly doses acid into the aqueous solution in the vessel 73.

[0082] The control strategy of the control unit 50 is to use the pH from the sensor 69 as a feedforward to start the injection of acid and the circulation of the aqueous solution through the wet scrubber 75 before the third pH sensor 81 detects that the pH value is too high, to maintain the pH detected by the third pH sensor 81 at a value below 7. If the third pH sensor 81 indicates a pH lower than a certain value, almost all of the ammonia will be absorbed into the aqueous solution, and the ammonia in the outlet will be kept within an acceptable range. Therefore, in this embodiment, the outlet sensor 80 can be omitted.

[0083] Additionally, in some embodiments, an optional three-way valve 68 is provided in the discharge line 65, preferably downstream of the blower 61. This three-way valve 68 has a first position in which the discharged air stream is directed to the first pH sensor, to the container 70, and to the atmosphere, as in the previously described embodiments, and a second position in which the discharged air stream is directed to a large capacity ammonia receiver 95. The large capacity ammonia receiver 95 can consist of an absorption tank at least partially filled with water, or at least partially a cascade of absorption tanks, and is preferably configured to dissolve the ammonia in the water, increasing the concentration of ammonia in the water so that the ammonia can be effectively stored or reused as engine fuel.

[0084] In embodiments where this optional three-way valve is provided, the control unit 50 is configured to divert the ammonia-containing exhaust air flow away from the previously described ammonia detection system based on the first pH sensor 69 when ammonia above a predetermined threshold is detected using the ammonia detection system, thereby providing the advantage that a large leakage of ammonia into the inter-tube space 33 does not exceed the capacity of the wet scrubber 75, and the ammonia in the exhaust air is safely treated in the large-capacity ammonia receiver 95.

[0085] Various aspects and implementations of the invention have been described with reference to several examples. However, upon reviewing the specification, drawings, and claims of this application, those skilled in the art will understand and be able to embody many variations in addition to the described examples in implementing the claimed invention. The words "comprise," "have," "include," and "consist" in the claims do not exclude the presence of unrecited elements or steps. The absence of an explicit reference to a plurality of recited elements in a claim does not exclude the presence of a plurality of such elements.

[0086] Any 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. 1. A system for detecting an ammonia leak in an ammonia fuel system of a large, two-stroke, uniflow-scavenged, turbocharged, multi-cylinder internal combustion engine having at least one operating mode using ammonia as a primary fuel, comprising: the system comprises a double-walled piping for supplying ammonia to a fuel valve of the engine through a first inner pipe of the double-walled piping and / or for returning excess ammonia from the fuel valve of the engine through a second inner pipe of the double-walled piping; the double-walled piping has at least the first inner pipe or the second inner pipe and an outer pipe surrounding the first or second inner pipe, and an inter-pipe space exists between the at least first or second inner pipe and the outer pipe; the inter-pipe space is connected to an intake pipe at or near a first end of the double-walled pipe for taking in air from the atmosphere; the inter-tube space is connected to an exhaust pipe at or near a second end of the double-walled piping for delivering air from the inter-tube space to the atmosphere; the discharge pipe comprises a unit for mixing water vapor with the air being discharged; the discharge line includes a first pH sensor downstream of the unit; system.

2. 10. The system of claim 1, further comprising a blower in the exhaust pipe for drawing airflow from the atmosphere into the inter-tube space and for drawing air to draw exhaust flow or air from the inter-tube space into the exhaust pipe.

3. 3. The system of claim 1, further comprising a controller connected to the first pH sensor, the controller configured to monitor the pH value sensed by the first pH sensor.

4. 4. The system of claim 3, further comprising a fuel pump for supplying a flow of ammonia to the first inner pipe, wherein the controller is configured to issue a signal to stop operation of the fuel pump to terminate the supply of ammonia to the inner pipe when it is determined that ammonia has leaked into the inter-pipe space.

5. 5. The system according to claim 3, further comprising a valve in the intake pipe, wherein the control unit is configured to close the valve to prevent or at least throttle the intake of fresh air into the inter-pipe space when it is determined that ammonia has leaked into the inter-pipe space.

6. 10. The system of claim 1, further comprising a container in the exhaust pipe for absorbing ammonia in the exhausted air into an aqueous solution.

7. The system of claim 6 , wherein the container is located downstream of the first pH sensor.

8. 7. The system of claim 6, comprising an acid source for adding acid to the aqueous solution and a second pH sensor configured to sense a pH of the aqueous solution.

9. 9. The system of claim 8, wherein a controller is coupled to the acid source and configured to add acid from the acid source to the aqueous solution as a function of the sensed pH of the aqueous solution.

10. 9. The system of claim 8, comprising a sensing system for sensing the density of the aqueous solution or for sensing the weight of the aqueous solution in the container.

11. 11. The system of claim 10, wherein the controller is connected to the detection system and configured to determine that the aqueous solution needs to be replaced with fresh aqueous solution when the detected specific density of the aqueous solution exceeds a threshold value or when the weight of the aqueous solution in the container exceeds a threshold value.

12. 7. The system of claim 6, further comprising a wet scrubber downstream of the vessel for removing ammonia vapor from the exhausted air.

13. 13. The system of claim 12, wherein the aqueous solution from the vessel is supplied to the wet scrubber and returned to the vessel after passing through the wet scrubber.

14. The system of claim 10 , wherein a third pH sensor is configured to sense the pH of the aqueous solution returning from the wet scrubber.

15. The system of claim 12 including an ammonia concentration sensor downstream of the wet scrubber.

16. 1. A large, two-stroke, uniflow-scavenged, turbocharged, multi-cylinder internal combustion engine having at least one operating mode using ammonia as a primary fuel, comprising: at least one cylinder having a cylinder liner and a reciprocating piston within said cylinder liner, and a cylinder cover covering said cylinder; a combustion chamber defined 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 in the cylinder cover or the cylinder liner; a system according to any one of claims 1 to 14; An institution that has:

17. 17. The engine of claim 16, wherein said ammonia fuel system comprises a supply line and a return line, and wherein the piping forming said supply line and said return line comprises double-walled piping.

18. 1. A method for detecting an ammonia leak in an ammonia fuel system of a large, two-stroke, uniflow-scavenged, turbocharged, multi-cylinder internal combustion engine having at least one operating mode using ammonia as a primary fuel, comprising: the engine has an ammonia fuel system; the ammonia fuel system comprises double-walled piping for supplying ammonia to a fuel valve of the engine through a first inner pipe of the double-walled piping and / or for returning excess ammonia from the fuel valve of the engine through a second inner pipe of the double-walled piping; the double-walled piping has at least the first inner pipe or the second inner pipe, and an outer pipe surrounding the first or second inner pipe, and the method further comprises: introducing an air flow from the atmosphere into an inter-tube space between the at least first or second inner tube and the outer tube at or near a first end of the double-walled pipe; Discharging the air flow from the inter-pipe space to atmosphere at or near the other end of the double-walled piping; mixing a stream of water vapor with the exhaust air stream to form an aqueous solution of ammonia so as to dissolve at least a portion of the ammonia in the exhaust air; measuring the pH of the resulting exhaust gas and water vapor mixture; A method comprising:

19. 20. The method of claim 18, comprising issuing a signal that an ammonia leak has been detected if the measured pH exceeds a threshold value.

20. 20. The method of claim 19, including issuing a signal that an ammonia leak has been detected if the measured pH is higher than the pH of the water vapor stream mixed with the exhaust air stream by a margin.

21. 20. A method according to claim 18 or 19, comprising aspirating an intake air flow into the inter-tubular space and aspirating an exhaust air flow from the inter-tubular space by drawing air by suction.

22. 20. The method of claim 18, comprising supplying a flow of ammonia to the first inner tube and terminating the supply of ammonia to the first inner tube when an ammonia leak is detected.

23. 20. The method of claim 18, comprising preventing or at least restricting the intake of fresh air into the inter-tube space if an ammonia leak is detected.

24. 20. The method of claim 18, comprising absorbing ammonia into an aqueous solution in a vessel downstream from the location where the pH is measured.

25. 25. The method of claim 24, comprising adding an acid to the aqueous solution.

26. 26. The method of claim 25, wherein the acid comprises sulfuric acid, citric acid, phosphoric acid, and / or hydrochloric acid.

27. 25. The method of claim 24, including cleaning the exhausted air with a scrubber located downstream of the vessel.

28. 28. The method of claim 27, including measuring ammonia content in the exhaust downstream of the scrubber with a fourth pH or ammonia sensor, and terminating ammonia-primarily fueled engine operation when the ammonia content detected in the exhaust downstream of the scrubber exceeds a threshold value.

29. 25. The method of claim 24, comprising determining a specific density of the aqueous solution or a weight of the aqueous solution in the container, and replacing the aqueous solution when the specific density of the aqueous solution or the weight of the aqueous solution in the container exceeds a threshold value.

30. 1. A method of addressing an ammonia leak in a fuel system of a large, two-stroke, uniflow-scavenged, turbocharged, multi-cylinder internal combustion engine having at least one operating mode using ammonia as a primary fuel, comprising: the engine has an ammonia fuel system; the ammonia fuel system comprises double-walled piping for supplying ammonia to a fuel valve of the engine through a first inner pipe of the double-walled piping and / or for returning excess ammonia from the fuel valve of the engine through a second inner pipe of the double-walled piping; the double-walled piping has at least the first inner pipe or the second inner pipe, and an outer pipe surrounding the first or second inner pipe, and the method comprises: introducing a flow of fresh air from the atmosphere into an inter-pipe space between at least the first or second inner pipe and the outer pipe at or near a first end of the double-walled pipe; Discharging the air flow from the inter-tube space at or near the other end of the double-walled piping; measuring the ammonia concentration in the discharged air stream; Absorbing ammonia in the exhaust air in an aqueous solution in a container downstream from a location where the ammonia concentration of the exhaust air is measured; sensing the pH of the aqueous solution; adding an acid to the aqueous solution to protonate NH3(aq) under the formation of ammonium hydroxide, and maintaining the pH of the aqueous solution at a predetermined level; determining a density of the aqueous solution and replacing the aqueous solution when the determined density exceeds a threshold; A method comprising:

31. 1. A method of addressing an ammonia leak in a fuel system of a large, two-stroke, uniflow-scavenged, turbocharged, multi-cylinder internal combustion engine having at least one operating mode using ammonia as a primary fuel, comprising: the engine has an ammonia fuel system; the ammonia fuel system comprises double-walled piping for supplying ammonia to a fuel valve of the engine through a first inner pipe of the double-walled piping and / or for returning excess ammonia from the fuel valve of the engine through a second inner pipe of the double-walled piping; The double-walled piping includes at least a first inner pipe or the second inner pipe, and an outer pipe surrounding the at least first or second inner pipe, and the method further comprises: Intake a fresh air flow from the atmosphere through an intake pipe into an inter-pipe space between the at least first or second inner pipe and the outer pipe at or near a first end of the double-walled pipe; Discharging the air flow from the inter-tube space at or near the other end of the double-walled piping; Suctioning an intake air flow through the intake pipe into the inter-tube space, and suctioning an exhaust air flow from the inter-tube space through an exhaust pipe by drawing air by suction; measuring ammonia concentration in the exhaust air stream to detect whether ammonia has leaked into the inter-tube space; if an ammonia leak is detected, blocking or at least restricting air flow through the intake tube while continuing to draw air by suction; A method comprising:

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