Method and system for detecting ammonia leaks in a large two-stroke uniflow scavenging turbocharged internal combustion engine, method and system for treating leaked ammonia

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 disclosure of the present application (hereinafter referred to as the present disclosure) relates to a method and system for detecting ammonia leakage in an ammonia fuel system of a large two-stroke uniflow scavenging turbocharged multi-cylinder internal combustion engine having at least one operating mode using ammonia as a second main fuel, and a method and system for treating ammonia leakage in an ammonia fuel system of a large two-stroke uniflow scavenging turbocharged multi-cylinder internal combustion engine having at least one operating mode using ammonia as a main fuel, preferably for reducing and controlling ammonia emissions. Background 【0002】 Large two-stroke uniflow scavenging turbocharged internal combustion engines are typically used as propulsion systems for large ships and as prime movers for power generation plants. Their size, weight, and output set large two-stroke turbocharged compression ignition internal combustion engines apart from other combustion engines, positioning this type of compression internal combustion engine in a unique classification. 【0003】 Internal combustion engines have hitherto been mainly operated by hydrocarbon fuels such as fuel oils like diesel oil and fuel gases such as natural gas or petroleum gas. The combustion of hydrocarbon fuels is accompanied by the generation of greenhouse gases such as carbon dioxide (CO2), which can cause air pollution and climate change. Unlike the impurities in petroleum fuels that produce by-products, the generation of CO2 is inevitable in the combustion of hydrocarbons. The energy density and CO2 footprint of fuels depend on the length of the hydrocarbon chain and the complexity of the hydrocarbon molecules. Therefore, gaseous hydrocarbon fuels have a lower CO2 emissions than liquid hydrocarbon fuels. However, gaseous hydrocarbon fuels are difficult to handle and store and are costly. In order to reduce CO2 emissions, research on fuels other than hydrocarbons is underway. 【0004】 Ammonia is a compound obtained from petroleum, biomass, and renewable energy sources (wind, solar, hydro, and geothermal). Ammonia produced using renewable energy sources has virtually zero carbon emissions when burned, and does not emit 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. However, it has not yet been used to operate compression-ignition internal combustion engines. 【0006】 Ammonia is harmful and has a pungent odor. Therefore, ammonia leaks from engines must be avoided, and any leaks should be detected as quickly as possible, ideally within two minutes. Thus, there is a need for solutions that provide early detection of ammonia leaks and methods for addressing them. 【0007】 Furthermore, when discontinuing operation using ammonia fuel and switching to, for example, conventional fuel, it is necessary to purge (remove) the ammonia from the fuel system. However, the purged ammonia cannot simply be discharged into the atmosphere / environment. Therefore, it is also necessary to install a system to process this considerable amount of ammonia. 【0008】 KR20230104327A discloses a double-pipe system for ships, its installation method, and a method for discharging ammonia using this system. This document describes how the fuel supply and fuel return lines in the engine room of a ship using ammonia as fuel are double-pipe to accommodate ammonia leakage, and how the double-pipe at the rear end between the fuel preparation room and the engine is pressurized to prevent leaked ammonia from entering the fuel preparation room and the engine. Abstract 【0009】 The objective is to provide a large two-stroke uniflow scavenging turbocharged internal combustion engine that solves or at least mitigates the above-mentioned problems. 【0010】 The aforementioned and other issues are resolved by the features described in the independent claims. More specific implementations will become apparent from the dependent claims, specification, and drawings. 【0011】 According to the first aspect, a system is provided for detecting ammonia leaks in the ammonia fuel system of a large two-stroke uniflow scavenging turbocharged multi-cylinder internal combustion engine having at least one operating mode that uses ammonia as the primary fuel. This system features double-walled piping, The double-walled piping is for supplying ammonia to the engine's fuel valve through the first inner pipe of the double-walled piping, and / or for returning excess ammonia from the engine's fuel valve through the second inner pipe of the double-walled piping. The double-walled piping comprises at least the first inner pipe or the second inner pipe and an outer pipe surrounding the first or second inner pipe, with a space between the pipes between at least the first or second inner pipe and the outer pipe. The space between the pipes is connected to an intake pipe for taking in air from the atmosphere at or near the first end of the double-walled piping. The inter-pipe space is connected to a discharge pipe for supplying air from the inter-pipe space to the atmosphere at or near the second end of the double-walled piping. The aforementioned discharge pipe is equipped with a unit for mixing water vapor with the discharged air, The discharge pipe is equipped with a first pH sensor downstream of the unit. 【0012】 When an ammonia leak causes ammonia to be present in the exhaust airflow, adding a water vapor stream to the exhaust airflow affects the pH of the resulting mixture. Therefore, if ammonia is present in the exhaust air, the pH of the mixture measured downstream of the water vapor addition point will be higher. This allows for early detection of ammonia in exhaust air using a pH sensor. Dedicated ammonia sensors can typically only measure ammonia concentrations in the range of 100 to 5000 PPM. When exposed to ammonia concentrations higher than 5000 PPM, which are common in ammonia leaks, the sensor becomes saturated, rendering it non-functional for at least 24 hours. Therefore, being able to use a pH sensor instead of a dedicated ammonia sensor is a significant advantage. Furthermore, existing dedicated ammonia sensors are slow to react, delaying countermeasures after ammonia leak detection. 【0013】 In one example of the implementation of the first aspect described above, the system is provided with a blower in the exhaust pipe for drawing airflow from the atmosphere into the space between the pipes and for drawing air in and drawing a discharge flow or air from the space between the pipes into the exhaust pipe. 【0014】 In one example of the implementation of the first aspect, the system includes a control unit connected to the first pH sensor, and the control unit is configured to monitor the pH detected by the first pH sensor. 【0015】 In one example of the implementation of the first aspect, the first pH sensor is configured to emit a signal representing the measured pH, and the system includes a control unit that receives the signal from the first pH sensor. 【0016】 In one example of the implementation of the first aspect described above, the system includes a fuel pump for supplying a flow of ammonia to the first inner pipe, and the control unit is configured to issue a signal to stop the operation of the fuel pump in order to terminate the supply of ammonia to the inner pipe when it determines that ammonia has leaked into the inter-pipe space. Preferably, the control unit is configured to issue a signal to switch the engine operation to an alternative fuel. 【0017】 In one example of the implementation of the first aspect described above, the system is provided with a valve in the intake pipe, and the control unit is configured to close the valve to prevent the intake of fresh air into the inter-pipe space, or at least restrict it, when it determines that ammonia has leaked into the inter-pipe space. 【0018】 In one example of the implementation of the first aspect described above, the system includes a container in the discharge pipe for absorbing ammonia in the discharged air into an aqueous solution, and this container is preferably located downstream of the first pH sensor. 【0019】 In one example of the implementation of the first aspect described above, the system comprises an acid source for adding acid to the aqueous solution and a second pH sensor configured to detect the pH of the aqueous solution. The control unit 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 detected pH of the aqueous solution. Preferably, the control unit is configured to add acid when the detected pH of the aqueous solution exceeds a threshold. 【0020】 In one example of the implementation of the first aspect described above, the system includes a detection system for detecting the density of an aqueous solution. The control unit is connected to the detection system and is configured to determine that the aqueous solution needs to be replaced with a 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. 【0021】 In an example of an implementation form of the first aspect, the system includes a wet scrubber for removing ammonia vapor from the discharged air downstream of the container. 【0022】 In an example of an implementation form of the first aspect, an aqueous solution from the container is supplied to the wet scrubber and returned to the container after passing through the wet scrubber. 【0023】 In an example of an implementation form of the first aspect, a third pH sensor is configured to detect the pH of the aqueous solution returning from the wet scrubber. 【0024】 In an example of an implementation form 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 operating mode using ammonia as the main fuel. This engine includes · 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 formed between the reciprocating piston and the cylinder cover within the cylinder; · an ammonia fuel system configured to supply pressurized ammonia to a fuel valve arranged on the cylinder cover or the cylinder liner; · a system according to the first aspect and its possible implementation forms; and includes. 【0026】 In an example of an implementation form 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 is made of double-walled piping. 【0027】 According to a third aspect, a method is provided for detecting ammonia leaks in the ammonia fuel system of a large two-stroke uniflow scavenging turbocharged multi-cylinder internal combustion engine having at least one operating mode that uses ammonia as the primary fuel. In this method, The aforementioned engine has an ammonia fuel system, The ammonia fuel system comprises double-walled piping, which is for supplying ammonia to the engine's fuel valve through a first inner tube of the double-walled piping, and / or for returning excess ammonia from the engine's fuel valve through a second inner tube of the double-walled piping. The double-walled piping comprises at least the first inner pipe or the second inner pipe and an outer pipe surrounding the first or second inner pipe. And the above method is At the first end of the double-walled piping or in its vicinity, an airflow from the atmosphere is introduced into the space between the pipes, at least the first or second inner pipe and the outer pipe; At the other end of the double-walled piping or in its vicinity, an airflow is discharged from the space between the pipes into the atmosphere; To dissolve at least a portion of the ammonia in the emitted air, a water vapor stream is mixed with the emitted air stream to form an aqueous solution of ammonia; The pH of the resulting mixture of exhaust gas and water vapor is measured; Includes. 【0028】 In one example of the implementation of the third aspect described above, the method includes issuing a signal indicating that an ammonia leak has been detected when the measured pH exceeds a threshold, and preferably includes issuing a signal indicating that an ammonia leak has been detected when the pH is higher than a certain margin than the pH of the water vapor stream mixed with the discharged air stream. 【0029】 In one example of the implementation of the third aspect described above, the method includes drawing in the intake airflow into the inter-pipe space and drawing in the exhaust airflow from the inter-pipe space by drawing in air through suction, preferably including suction using a blower downstream of the inter-pipe space. 【0030】 In one example of the implementation of the third aspect, the method includes supplying a flow of ammonia to the first inner pipe and terminating the supply of ammonia to the first inner pipe when an ammonia leak is detected, and preferably also includes switching the engine to alternative fuel operation. 【0031】 In one example of the implementation of the third aspect described above, the method includes, when an ammonia leak is detected, preventing or at least restricting the intake of fresh air into the space between the pipes. 【0032】 In one example of the implementation of the third aspect, the method includes absorbing ammonia into an aqueous solution in a container downstream of the position where the pH is measured. 【0033】 In one example of the implementation of the third aspect described above, the method comprises adding an acid to the aqueous solution, wherein the acid preferably comprises one or more of sulfuric acid, citric acid, phosphoric acid, and hydrochloric acid. 【0034】 In one example of the implementation of the third aspect described above, the method includes purifying the discharged air with a scrubber located downstream of the container. 【0035】 In one example of the implementation of the third aspect described above, the method includes measuring the ammonia content in the exhaust downstream of the scrubber, preferably using a fourth pH sensor, an infrared sensor, or a catalytic sensor. 【0036】 In one example of the implementation of the third aspect described above, the method includes terminating the operation using ammonia as the main fuel when the ammonia content detected in the exhaust downstream of the scrubber exceeds a threshold. 【0037】 In one example of the implementation of the third aspect, the method includes determining the specific density of the aqueous solution or the 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 or when the total weight of the aqueous solution exceeds a threshold. 【0038】 According to a fourth aspect, a method is provided for addressing ammonia leakage in the fuel system of a large two-stroke uniflow scavenging turbocharged multi-cylinder internal combustion engine having at least one operating mode that uses ammonia as the primary fuel. In this method, The aforementioned engine has an ammonia fuel system, The ammonia fuel system comprises double-walled piping, which is for supplying ammonia to the engine's fuel valve through a first inner tube of the double-walled piping, and / or for returning excess ammonia from the engine's fuel valve through a second inner tube of the double-walled piping. The double-walled piping comprises at least the first inner pipe or the second inner pipe and an outer pipe surrounding the first or second inner pipe. And the above method is At the first end of the double-walled piping or in its vicinity, a flow of fresh air from the atmosphere is introduced into the inter-pipe space between the first or second inner pipe and the outer pipe; At the other end of the double-walled piping or in its vicinity, the airflow is discharged from the space between the pipes; To measure the ammonia concentration in the discharged airflow; The ammonia in the emitted air is absorbed into an aqueous solution in a container downstream of the location where the ammonia concentration of the emitted air is measured; To detect the pH of the aqueous solution; To add an acid to the aqueous solution, protonate NH3 under the production of ammonium hydroxide, and maintain the pH of the aqueous solution at a predetermined level; The density of the aqueous solution is determined (preferably in a wet scrubber), and if the determined density exceeds a threshold, the aqueous solution is replaced (preferably with fresh water); Includes. 【0039】 By adding acid to an aqueous solution to maintain a desired pH, the density of the solution increases over time. By measuring and determining the specific gravity of the supernatant liquid or the increase in the weight of the solution in the container, it is possible to determine when the solution is becoming saturated and needs to be replaced. 【0040】 According to a fifth aspect, a method is provided for addressing ammonia leakage in the fuel system of a large two-stroke uniflow scavenging turbocharged multi-cylinder internal combustion engine having at least one operating mode that uses ammonia as the primary fuel. In this method, The aforementioned engine has an ammonia fuel system, The ammonia fuel system comprises double-walled piping, which is for supplying ammonia to the engine's fuel valve through a first inner tube of the double-walled piping, and / or for returning excess ammonia from the engine's fuel valve through a second inner tube of the double-walled piping. The double-walled piping comprises at least a first inner pipe or a second inner pipe, and an outer pipe surrounding at least the first or second inner pipe. And the above method is At the first end of the double-walled piping or in its vicinity, fresh air is drawn in from the atmosphere through an intake pipe into the inter-pipe space between at least the first or second inner pipe and the outer pipe; At the other end of the double-walled piping or in its vicinity, the airflow is discharged from the space between the pipes; Preferably, a blower in the discharge pipe is used to promote the flow of intake air into the inter-pipe space through the intake pipe, and to draw in air by suction to draw the exhaust airflow from the inter-pipe space through the exhaust pipe; The ammonia concentration in the exhaust airflow is measured to detect whether ammonia has leaked into the space between the pipes; If an ammonia leak is detected, while continuing to draw in air by suction, the airflow through the intake pipe shall be blocked or at least restricted; Includes. 【0041】 When an ammonia leak is detected, blocking the airflow through the intake pipe reduces the ammonia flow rate to the downstream ammonia treatment system, such as a wet scrubber, thereby reducing the capacity requirements of the downstream treatment system for handling the ammonia flow, and consequently saving space and cost. 【0042】 These and other aspects will become even clearer from the embodiments described below. [Brief explanation of the drawing] 【0043】 The following will describe various perspectives, embodiments, and implementation examples in detail, with reference to the exemplary embodiments shown in the drawings. [Figure 1] This figure shows an overview of a large two-stroke diesel engine, according to an exemplary embodiment, viewed from the front. [Figure 2] Figure 1 shows an overview of the large two-stroke engine as viewed from the rear. [Figure 3] Figure 1 is a schematic representation of a large two-stroke engine. [Figure 4] This is a schematic representation of an engine according to the first embodiment. This engine has an ammonia fuel system, an ammonia leak detection system, and a leaked ammonia treatment system. [Figure 5] This is a schematic representation of an engine according to the second embodiment. This engine also has an ammonia fuel system, an ammonia leak detection system, and a leaked ammonia treatment system. Detailed description 【0044】 In the following detailed description, the internal combustion engine will be described with reference to the crosshead-type large low-speed two-stroke uniflow scavenging turbocharged internal combustion engine of the embodiment. Note that in some cases, the internal combustion engine may be a different type of engine. The large two-stroke low-speed uniflow scavenging turbocharged internal combustion engine can be a compression-ignition type (i.e., high-pressure type) engine 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 in which the scavenging air is mixed with fuel before or during compression. In the latter case, pilot ignition with an additive (e.g., fuel oil) is usually performed to ensure reliable ignition. 【0045】 Figures 1-3 depict a turbocharged large low-speed two-stroke diesel engine. This engine has a crankshaft 8 and a crosshead 9. Figure 3 is a schematic representation of the turbocharged large low-speed two-stroke diesel engine, along with its intake and exhaust systems. In this embodiment, the engine has six cylinders in series. A turbocharged large low-speed two-stroke diesel engine typically has 4 to 14 cylinders arranged in series. These cylinders are supported on a cylinder frame 23. The cylinder frame 23 is supported on an engine frame 11. Such engines can be used, for example, as the main engine of a ship or as a stationary engine to power a generator in a power plant. The total output of the engine can be in the range of, for example, 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 is provided with a scavenging port 18 in its lower region and an exhaust valve in the center of its 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 an ammonia-based fuel. In conventional fuel mode, the engine is operated on conventional fuels, such as fuel oil (marine diesel fuel) or heavy oil. 【0047】 Scavenging air is introduced through the scavenging receiver 2 to the scavenging 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, compressing the scavenging air. Fuel (ammonia in ammonia mode) is injected into the combustion chamber in the cylinder liner 1 at or near TDC through a plurality of (high-pressure) fuel valves 49 located in the cylinder cover 22. Combustion occurs following the injection of fuel, producing exhaust gas. Each cylinder cover 22 is provided with two or more fuel valves 49. The fuel valves 49 may be configured to inject only one specific type of fuel (e.g., ammonia). In that case, there would also be two or more fuel valves (not shown) for injecting conventional fuel into the combustion chamber. Thus, 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 in 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, an additional (usually small) fuel valve may be located in the cylinder cover, configured to inject a sparking fluid to ensure ignition of the ammonia fuel. The sparking fluid may be, for example, dimethyl ether (DME) or fuel oil. However, it may be another form of ignition accelerator, such as hydrogen. Since the engine may be a dual-fuel engine, the engine may have a conventional fuel supply system for conventionally supplying fuel to the fuel valve 49 (not shown). In some embodiments, a fuel valve 49' is located along the cylinder liner (shown by a dashed line). The fuel valve 49' introduces fuel into the cylinder liner on the way from BDC to TDC and before passing the fuel valve 49'. The piston 10 then compresses the mixture of scavenging air and fuel. Ignition is timed at or near TDC. Ignition is achieved by a spark, laser, injection of a sparking fluid, etc. In embodiments having a fuel valve 49', the pressure at the time fuel is introduced is considerably lower than the pressure at the time fuel is injected in embodiments having a fuel valve 49 in the cylinder cover 22.Therefore, the pressure required for the fuel supply system 30 to deliver fuel can be quite low, and / or a pressure booster, often used in the fuel valve 49 located in the cylinder cover 22, may not be necessary. 【0048】 When the exhaust valve 4 opens, the exhaust flows through the exhaust duct provided in the cylinder 1 to the exhaust receiver 3, then through the selective catalytic reduction reactor (SCR reactor) 28, through the first exhaust pipe 19, and to the turbine 6 of the turbocharger 5. From there, the exhaust flows through the second exhaust pipe 25 to the economizer 20, and is then released into the atmosphere from the outlet 21. The SCR reactor reduces emissions of exhaust gases, especially NOx. 【0049】 The turbine 6 drives the compressor 7 via a shaft. The compressor 9 is supplied with outside air through the air intake 12. The compressor 7 sends the compressed scavenging air to the scavenging pipe 13, which is connected to the scavenging receiver 2. The scavenging air in the scavenging pipe 13 passes through the 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 airflow when the compressor 7 of the turbocharger 5 cannot provide sufficient pressure for the scavenging tank 2, i.e., when the engine is under low or partial load. When the engine is under high load, the compressor 7 of the turbocharger can supply sufficiently compressed scavenging air, so the auxiliary blower 16 is bypassed by a check valve 15 and the electric motor 17 is stopped. 【0051】 In ammonia mode, the engine is operated using ammonia as the primary fuel. Ammonia is supplied to ammonia valves 30, 30' at approximately constant pressure and temperature. Ammonia can be supplied to ammonia valves 49, 49' in liquid or gas phase. Liquid ammonia may be aqueous ammonia, i.e., an aqueous solution of ammonia. 【0052】 Conventional fuel systems are well known and therefore are not illustrated or described in detail. The ammonia fuel system 30 supplies liquid-phase ammonia to ammonia valves 49, 49' at an intermediate supply pressure (e.g., 30–80 bar). In an alternative example, ammonia fuel is supplied in the gas phase to 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' are equipped with 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 engine's compression pressure. Typically, the injection pressure of a compression-ignition engine is higher than 300 bar. 【0053】 Figure 4 shows the early ammonia leak detection and treatment system in more detail. 【0054】 Ammonia is stored in the liquid phase at approximately 17 bar in a pressure-type storage tank 36. Ammonia can be stored in the liquid phase in the ammonia storage tank 36 if the pressure is 8.6 bar or higher at an ambient temperature of 20°C. However, to maintain the liquid phase even when the ambient temperature rises, it is preferable to store ammonia at 17 bar or higher. 【0055】 A low-pressure ammonia supply line 32 connects the outlet of the ammonia storage tank 36 to the inlet of the intermediate-pressure supply pump 32. The intermediate-pressure supply pump 32 pumps liquid ammonia from the intermediate-pressure ammonia supply line 31 to the valve train formed by the fuel valves 49, 49'. Some of the liquid ammonia supplied to the valve train is injected into the engine's combustion chamber, while another portion is returned to the ammonia return line 45. The ammonia return line 38 connects the return ports of the fuel valves to the low-pressure supply line 39. Thus, some of the liquid ammonia fuel is recirculated to the inlet of the intermediate-pressure supply pump 32. 【0056】 If operation on ammonia fuel is stopped due to a malfunction of the ammonia fuel system 30, an ammonia leak, or other reasons such as switching to a conventional fuel, the control unit 50 will purge the ammonia fuel system 30 to remove ammonia from the system and instruct the engine to switch 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 is for supplying ammonia to the engine's fuel valves 49, 49' through the first inner pipe 35 of the double-walled piping 34, 40, and for returning excess ammonia from the engine's fuel valves 49, 49' through the second inner pipe 45 of the double-walled piping 34, 40. The double-walled piping 34, 40 has the first inner pipe 35 and the second inner pipe 45, and an outer pipe surrounding the first inner pipe 35 or the second inner pipe 45. A space between the pipes 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 pipeline 31, and the second inner pipe 45 is part of the ammonia return pipeline 39. In some embodiments, a single space between the pipes 33 surrounds the first inner pipe 35 and the second inner pipe 45. In another embodiment, there is an inter-pipe space 33 surrounding the first inner pipe 35 and another inter-pipe space 33 surrounding the second inner pipe 45. 【0058】 The inter-pipe space 33 is connected to an intake pipe 26 for taking in air from the atmosphere at or near the first end of the double-walled piping 40. The inter-pipe space 33 is connected to an exhaust pipe 65 for sending air from the inter-pipe space 33 to the atmosphere at or near the second end of the double-walled piping 34, 40. 【0059】 Although the engine room 48 is schematically represented by a dashed line, the double-walled piping 34 and 40 extend along the first and second inner pipes 35 and 45, at least to the extent that they are located within the engine room 48, to prevent ammonia from entering the engine room. 【0060】 A blower 61 is provided in the exhaust pipe 65. This is to draw airflow from the atmosphere into the inter-pipe space 33 via the intake pipe 26, and to draw exhaust flow or air from the inter-pipe space 33 by drawing air into the exhaust pipe 66 through suction. A second blower 61' is also provided for redundancy. 【0061】 The discharge pipe 65 is equipped with a unit 66 for mixing water vapor with the discharged air. This unit 66 may be equipped with an absorber or a wet scrubber as shown in the figure. 【0062】 When ammonia gas in the exhausted air (which originates from leakage from the first or second inner tubes 35, 45 into the inter-tube space 33) mixes with water vapor in unit 66, the ammonia dissolves in water to form 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 water molecules to form ammonium ions (NH4). + ) and hydroxide ions (OH - ) generates. 【0063】 The reaction can be expressed as follows: NH3(g) + H2O(l) ⇔ NH4 + (aq)+ OH - (aq) 【0064】 Therefore, ammonia 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 fraction of ammonia molecules actually react to form ammonium ions and hydroxide ions. 【0065】 Hydroxide ions (OH) - The presence of ) makes the solution basic (or alkaline), which can be detected using a pH indicator or pH sensor. 【0066】 Therefore, 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 unit 66. Thus, the first pH sensor can detect an increase in the pH of the exhaust gas 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 representing 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 whether 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, 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 placed inside the discharge pipe 65. The container 70 is for absorbing ammonia from the discharged air into the aqueous solution 73. The container 70 is located downstream of the first pH sensor 69. 【0071】 An acid source 72 is provided to add acid to the aqueous solution 73. A second pH sensor 77 is also provided, configured to detect the pH of the aqueous solution 73 in the container 70. The control unit 50 is preferably connected to the acid source 72 and is configured to add acid from the acid source 72 to the aqueous solution 73 as a function of the detected pH of the aqueous solution 73. Preferably, the control unit is configured to add acid when the detected pH of the aqueous solution exceeds a threshold. The acid preferably includes one or more of sulfuric acid, citric acid, phosphoric acid, and hydrochloric acid. 【0072】 A detection system 74 for detecting the density of the aqueous solution 73 is also provided. In the illustrated embodiment, this detection system is a density sensor 74 connected to the container 72. The density sensor 74 may be, for example, a commercially available resonant tuning fork densimeter. Alternatively, the density may be determined by measuring the pressure inside the container 70 at two positions at different heights and deriving the density from the pressure difference between the two positions. 【0073】 The control unit 50 is preferably connected to the density sensor 74 and is configured to determine that the aqueous solution 73 needs to be replaced with fresh aqueous solution 73 when the specific gravity of the detected aqueous solution 73 exceeds a threshold. Preferably, the aqueous solution 73 is replaced with fresh water. 【0074】 A wet scrubber is provided downstream 75 of the container 70 to remove ammonia vapor from the discharged air. The aqueous solution 73 is pumped by a pump 71 through a solution line 76 to the wet scrubber 75, flows downward by gravity, and returns to the container 70 through a packing 78 provided in the wet scrubber 75. The bottom of the wet scrubber 75 opens to the top of the container 70. The pH of the aqueous solution returning to the container 70 is measured by a third pH sensor 81. This value is useful information for determining the amount of acid that needs to be added to the aqueous solution and the container 70. 【0075】 In some embodiments, the control unit 50 is configured to terminate engine operation using ammonia as the main fuel when the ammonia content detected in the exhaust air downstream of the scrubber 75 exceeds a threshold. 【0076】 The demister 79 removes excess moisture from the air before it is discharged into the atmosphere through the rest of the exhaust pipe 65. 【0077】 Downstream of the wet scrubber 75, an ammonia concentration sensor 80 is positioned to ensure that the air discharged into the atmosphere does not contain excess ammonia or ammonia levels exceeding acceptable limits. (Typically, a maximum release of 20 PPM into the atmosphere is permitted.) The ammonia sensor 80 uses an infrared sensor; it is a commercially available infrared gas detector, that is, an 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 can typically detect ammonia concentrations from 100 to 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 the signal from the ammonia sensor 80 downstream of the wet scrubber 75 to maintain the second pH sensor of the wet scrubber 75 at a certain threshold, for example, 7 or less, thereby ensuring the efficiency of the wet scrubber 75. 【0079】 In some embodiments, the system includes an adjustable throttle valve 25 in the intake pipe 26. During normal operation, the adjustable throttle valve is fully open and does not substantially restrict the intake airflow through the intake pipe 26. The control unit 50 is configured to close the adjustable throttle valve 25 to prevent, or at least restrict, the intake of fresh air into the inter-pipe space 33 if the control unit 50 determines that ammonia has leaked into the inter-pipe space 33 while air intake by suction by the blower 61 continues. Preferably, when a leak is detected, the control unit 50 is configured to first fully close the adjustable throttle valve 25, and then slightly open the throttle valve 25 so that the throttle valve 25 significantly restricts the intake airflow through the intake pipe 26. This closure and subsequent reduction in intake airflow significantly reduces the flow rate of ammonia into the exhaust pipe 65, and accordingly, the ammonia treatment system can remove ammonia from the exhaust air in a much smaller volume, thus saving cost and space. 【0080】 Figure 5 discloses another embodiment of the ammonia leak detection and treatment system. In this embodiment, components and features similar to those already described or illustrated are denoted by the same reference numerals used previously. This embodiment is essentially identical to the embodiment shown in Figure 4, except for a 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 detects the weight of the container 73 containing the aqueous solution. A control unit 50, supplied with a signal from the load cell 91, records the weight increase due to the added acid and, accordingly, determines when the aqueous solution needs to be replaced. Furthermore, instead of a variable throttle valve, the intake pipe 26 is provided with two control valves 25 and 25' that, when an ammonia leak is detected, selectively close the intake airflow and selectively force it through an orifice 24, which substantially restricts the intake airflow, thereby reducing the flow rate of ammonia to the exhaust pipe 65 and allowing the use of a smaller capacity ammonia treatment system. 【0081】 In this embodiment, the acid is added to the flow of aqueous solution supplied to the wet scrubber 75. By controlling the pH of the aqueous solution in this way, it becomes possible to quickly detect and change the pH value of the water supplied to the wet scrubber 75. The water in container 73 will not reach the very low pH value that can occur in a control strategy in which the acid is directly added to the aqueous solution in container 73. 【0082】 The control strategy of the control unit 50 is to use the pH from sensor 69 as a feedforward to initiate acid injection and circulation of the aqueous solution through the wet scrubber 75 before the third pH sensor 81 detects that the pH value is too high, and to maintain the pH detected by the third pH sensor 81 at a value of less than 7. If the third pH sensor 81 shows a pH lower than a certain value, almost all of the ammonia is absorbed into the aqueous solution, and the ammonia at the outlet is kept within an acceptable range. Therefore, in this embodiment, the outlet sensor 80 can be omitted. 【0083】 Furthermore, in this embodiment, an optional three-way valve 68 is provided in the discharge pipe 65, preferably downstream of the blower 61. The three-way valve 68 has a first position in which the discharged airflow is directed to the first pH sensor, the container 70, and the atmosphere, as in the previously described embodiment, and a second position in which the discharged airflow is directed to a large-capacity ammonia receiver 95. The large-capacity ammonia receiver 95 may consist of an absorption tank or a cascade of absorption tanks that is at least partially filled with water, and is preferably configured to dissolve ammonia in water, increasing the concentration of ammonia in the water, thereby effectively storing the ammonia or allowing it to be reused as engine fuel. 【0084】 In embodiments equipped with this optional three-way valve, the control unit 50 is configured to move the exhaust flow containing ammonia away from the ammonia detection system described earlier based on the first pH sensor 69 when ammonia above a predetermined threshold is detected using the ammonia detection system. This has the advantage that a large leak 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 processed by the large-capacity ammonia receiver 95. 【0085】 Various aspects and implementation forms of the invention have been described with several embodiments. However, by examining the specification, drawings, and claims of this application, a person skilled in the art will understand and be able to realize many variations in the invention described in the claims, in addition to the embodiments described. The words “equipped with,” “having,” “including,” and “consisting of” in the claims do not exclude the existence of elements or steps that are not described. Even if it is not explicitly stated in the claims that there are multiple elements, this does not exclude the existence of multiple such elements. 【0086】 The reference numerals 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 constitute an integral part of the disclosure herein.

Claims

[Claim 1] A system for detecting ammonia leaks in the ammonia fuel system of a large two-stroke uniflow scavenging turbocharged multi-cylinder internal combustion engine having at least one operating mode that uses ammonia as the primary fuel, The system comprises double-walled piping, the double-walled piping for supplying ammonia to the engine's fuel valve through a first inner tube of the double-walled piping, and / or for returning excess ammonia from the engine's fuel valve through a second inner tube of the double-walled piping. The double-walled piping comprises at least the first inner pipe or the second inner pipe and an outer pipe surrounding the first or second inner pipe, with a space between the pipes between at least the first or second inner pipe and the outer pipe. The aforementioned space between pipes is connected to an intake pipe for taking in air from the atmosphere at or near the first end of the double-walled piping. The inter-pipe space is connected to a discharge pipe for supplying air from the inter-pipe space to the atmosphere at or near the second end of the double-walled piping. The aforementioned discharge pipe is equipped with a unit for mixing water vapor with the discharged air, The discharge pipe is equipped with a first pH sensor downstream of the unit. system. [Claim 2] The system according to claim 1, further comprising a blower in the discharge pipe for drawing in an airflow from the atmosphere into the space between the pipes, and for drawing in air and drawing a discharge flow or air from the space between the pipes into the discharge pipe. [Claim 3] The system according to claim 1, further comprising a control unit connected to the first pH sensor, wherein the control unit is configured to monitor the pH value detected by the first pH sensor. [Claim 4] The system according to claim 3, further comprising a fuel pump for supplying a flow of ammonia to the first inner pipe, wherein the control unit is configured to issue a signal to stop the operation of the fuel pump in order to terminate the supply of ammonia to the inner pipe when it determines that ammonia has leaked into the space between the pipes. [Claim 5] The system according to claim 3, wherein the intake pipe is provided with a valve, and the control unit is configured to close the valve to prevent the intake of fresh air into the inter-pipe space, or at least restrict it, when it determines that ammonia has leaked into the inter-pipe space. [Claim 6] The system according to claim 1, further comprising a container in the discharge pipe for absorbing ammonia in the discharged air into an aqueous solution. [Claim 7] The system according to claim 6, wherein the container is located downstream of the first pH sensor. [Claim 8] The system according to claim 6, comprising an acid source for adding acid to the aqueous solution and a second pH sensor configured to detect the pH of the aqueous solution. [Claim 9] The system according to claim 8, wherein a control unit is connected to the acid source and is configured to add acid from the acid source to the aqueous solution as a function of the pH of the aqueous solution detected by the acid source. [Claim 10] The system according to claim 9, further comprising a detection system for detecting the density of the aqueous solution or for detecting the weight of the aqueous solution in the container. [Claim 11] The system according to claim 10, wherein the control unit is connected to the detection system, and the control unit is configured to determine that it is necessary to replace the aqueous solution with a fresh aqueous solution when the specific density of the detected aqueous solution exceeds a threshold, or when the weight of the aqueous solution in the container exceeds a threshold. [Claim 12] The system according to claim 6, further comprising a wet scrubber downstream of the container for removing ammonia vapor from the discharged air. [Claim 13] The system according to claim 12, wherein an aqueous solution from the container is supplied to the wet scrubber and returned to the container after passing through the wet scrubber. [Claim 14] The system according to claim 12, wherein a third pH sensor is configured to detect the pH of the aqueous solution returning from the wet scrubber. [Claim 15] The system according to claim 12, further comprising an ammonia concentration sensor downstream of the wet scrubber. [Claim 16] A large two-stroke uniflow scavenging turbocharged multi-cylinder internal combustion engine having at least one operating mode using ammonia as the main fuel, - A cylinder having a cylinder liner and a reciprocating piston within the cylinder liner, and a cylinder cover covering the cylinder; - A combustion chamber formed between the reciprocating piston and the cylinder cover within the cylinder; - An ammonia fuel system configured to supply pressurized ammonia to a fuel valve located in the cylinder cover or the cylinder liner; - The system according to any one of claims 1 to 14; An institution equipped with such facilities. [Claim 17] The engine according to claim 16, wherein the ammonia fuel system comprises a supply line and a return line, and the piping forming the supply line and the return line consists of double-walled piping. [Claim 18] A method for detecting ammonia leaks in the ammonia fuel system of a large two-stroke uniflow scavenging turbocharged multi-cylinder internal combustion engine having at least one operating mode that uses ammonia as the primary fuel, The aforementioned engine has an ammonia fuel system, The ammonia fuel system comprises double-walled piping, which is for supplying ammonia to the engine's fuel valve through a first inner pipe of the double-walled piping, and / or for returning excess ammonia from the engine's fuel valve through a second inner pipe of the double-walled piping. The double-walled piping comprises at least the first inner pipe or the second inner pipe and an outer pipe surrounding the first or second inner pipe. And the above method is At the first end of the double-walled piping or in its vicinity, an airflow from the atmosphere is introduced into the space between the pipes, at least the first or second inner pipe and the outer pipe; At the other end of the double-walled piping or in its vicinity, an airflow is discharged from the space between the pipes into the atmosphere; To dissolve at least a portion of the ammonia in the emitted air, a water vapor stream is mixed with the emitted air stream to form an aqueous solution of ammonia; The pH of the resulting mixture of exhaust gas and water vapor is measured; Methods that include... [Claim 19] The method according to claim 18, comprising issuing a signal indicating that an ammonia leak has been detected when the measured pH exceeds a threshold. [Claim 20] The method according to claim 19, comprising issuing a signal that an ammonia leak has been detected when the measured pH is higher by a certain margin than the pH of the water vapor stream mixed with the discharged air stream. [Claim 21] The method according to claim 18 or 19, comprising drawing in an intake airflow into the space between the pipes, and drawing in an exhaust airflow from the space between the pipes by drawing in air through suction. [Claim 22] The method according to claim 18, comprising supplying a flow of ammonia to the first inner pipe and terminating the supply of ammonia to the first inner pipe when an ammonia leak is detected. [Claim 23] The method according to claim 18, comprising obstructing or at least restricting the intake of fresh air into the inter-pipe space when an ammonia leak is detected. [Claim 24] The method according to claim 18, comprising absorbing ammonia into an aqueous solution in a container downstream of the position where pH is measured. [Claim 25] The method according to claim 24, comprising adding an acid to the aqueous solution. [Claim 26] The method according to claim 25, wherein the acid comprises sulfuric acid, citric acid, phosphoric acid, and / or hydrochloric acid. [Claim 27] The method according to claim 24, further comprising purifying the discharged air with a scrubber located downstream of the container. [Claim 28] The method according to claim 27, comprising measuring the ammonia content in the exhaust downstream of the scrubber using a fourth pH sensor or ammonia sensor, and terminating engine operation using ammonia as the main fuel when the ammonia content detected in the exhaust downstream of the scrubber exceeds a threshold. [Claim 29] The method according to claim 24, comprising determining the specific density of the aqueous solution or the 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. [Claim 30] A method for addressing ammonia leakage in the fuel system of a large two-stroke uniflow scavenging turbocharged multi-cylinder internal combustion engine having at least one operating mode that uses ammonia as the primary fuel, The aforementioned engine has an ammonia fuel system, The ammonia fuel system comprises double-walled piping, which is for supplying ammonia to the engine's fuel valve through a first inner pipe of the double-walled piping, and / or for returning excess ammonia from the engine's fuel valve through a second inner pipe of the double-walled piping. The double-walled piping comprises at least the first inner pipe or the second inner pipe and an outer pipe surrounding the first or second inner pipe. And the above method is At the first end of the double-walled piping or in its vicinity, a flow of fresh air from the atmosphere is introduced into the inter-pipe space between the first or second inner pipe and the outer pipe; Discharging airflow from the space between the pipes at the other end of the double-walled piping or in its vicinity; To measure the ammonia concentration in the discharged airflow; The ammonia in the emitted air is absorbed into an aqueous solution in a container downstream of the location where the ammonia concentration of the emitted air is measured; To detect the pH of the aforementioned aqueous solution; Adding an acid to the aqueous solution, protonating NH3(aq) under the formation of ammonium hydroxide, and maintaining the pH of the aqueous solution at a predetermined level; The density of the aqueous solution is determined, and if the determined density exceeds a threshold, the aqueous solution is replaced; Methods that include... [Claim 31] A method for addressing ammonia leakage in the fuel system of a large two-stroke uniflow scavenging turbocharged multi-cylinder internal combustion engine having at least one operating mode that uses ammonia as the primary fuel, The aforementioned engine has an ammonia fuel system, The ammonia fuel system comprises double-walled piping, which is for supplying ammonia to the engine's fuel valve through a first inner pipe of the double-walled piping, and / or for returning excess ammonia from the engine's fuel valve through a second inner pipe of the double-walled piping. The double-walled piping comprises at least a first inner pipe or the second inner pipe, and an outer pipe surrounding at least the first or second inner pipe. And the above method is At the first end of the double-walled piping or in its vicinity, fresh air is drawn in from the atmosphere through an intake pipe into the inter-pipe space between at least the first or second inner pipe and the outer pipe; Discharging airflow from the space between the pipes at the other end of the double-walled piping or in its vicinity; The airflow taken in through the intake pipe is drawn into the space between the pipes, and the exhaust airflow is drawn in from the space between the pipes through the exhaust pipe by drawing in air through the intake pipe; The ammonia concentration in the exhaust airflow is measured to detect whether ammonia has leaked into the space between the pipes; If an ammonia leak is detected, while continuing to draw in air by suction, the airflow through the intake pipe shall be blocked or at least restricted; Methods that include...

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