JP6262268B2 - Fuel gas supply system for internal combustion engines - Google Patents

Description

  The present invention relates to a fuel gas supply system for an internal combustion engine. The fuel gas supply system includes a liquefied gas storage tank, a fuel gas supply line, and a heat exchange circuit having a working fluid. The fuel gas supply line includes a tank outlet line for liquefied gas, at least one fuel gas pump for pressurizing the fuel gas to the fuel gas supply pressure for the internal combustion engine, and final heat located downstream of the at least one fuel gas pump. The heat exchange circuit comprises at least a compressor, a first heat exchanger and an expansion device downstream thereof, and a second heat exchanger disposed downstream of the expansion device.

  Internal combustion engines are used as propulsion engines in ships such as container ships, bulk carriers, tankers, and LNG carriers. An internal combustion engine is typically a large two-stroke crosshead engine that is coupled to a propeller shaft and utilizes direct injection of fuel so that the fuel gas must be highly pressurized before delivery to the internal combustion engine. Don't be. For LNG carriers, it is known to deliver fuel gas to an internal combustion engine at a pressure of about 250 bar by a fuel gas supply system, where the fuel gas can be liquefied fuel gas or reliquefied boil-off gas directly from the LNG cargo storage tank. (BOG).

  This type of fuel gas delivery system, known as the Cryostar EcoRel system, is shown in FIG. BOG line A from the top of tank T is connected to the inlet of compressor B which delivers BOG to flash tank E through BOG superheat reducer C and BOG condenser D. The tank outlet line for LNG includes a pump G immersed in the LNG in the tank T, and the pump G has a gas boil-off gas generation rate (the rate of boiling off gas) in the internal combustion engine. It may be actuated to transfer LNG to the flash tank E when it is insufficient to cover consumption. The flash tank E is a liquefied gas storage tank with a small storage capacity and can be sized as a day tank for an internal combustion engine to store the amount of LNG required for at least several hours of operation of the engine.

  The pump H immersed in the LNG in the flash tank E serves as a primer pump for at least one fuel gas pump I for pressurizing the fuel gas to a fuel gas pressure of about 250 bar, The gas is delivered to the gas fuel inlet of the internal combustion engine K via the final heat exchanger J. The final heat exchanger J is supplied with a warm fluid from a heat source L and heats the fuel gas to a temperature of about 45 ° C. so that the fuel gas is acceptable in the engine.

  Boil-off gas cooling and condensation is accomplished by a heat exchange circuit using nitrogen as the working fluid. Nitrogen is compressed in three stages in compressor N, with each stage being accompanied by cooling of the nitrogen. Nitrogen then passes through the heat exchanger and is delivered to the cold expansion turbine P, first through the BOG condenser D and then through the BOG superheat reducer C, and back to the compressor N via the heat exchanger. The compressor and expansion turbine are arranged on a common single gearbox.

  JP 2009-204026 describes another BOG liquefaction system for re-liquefying BOG and returning it to the storage tank so that gas loss due to evaporation is avoided. The liquefied gas from the storage tank can be pumped by a pump immersed in the liquefied gas in the storage tank, further pressurized to a pressure of about 100-120 bar by an additional pump outside the tank, and supplied to the internal combustion engine. .

  Another BOG liquefaction system is known from US Pat. No. 7,690,365B2 for supplying fuel gas to an internal combustion engine in an LNG carrier at a delivery pressure of 200-300 bar. A first fuel gas pump immersed in LNG in the liquefied gas storage tank supplies LNG at a pressure of about 30 bar to the high pressure fuel gas pump via a heat exchanger. The boil-off gas from the tank is compressed and passes through a heat exchanger where the LNG cools the BOG and the liquefied BOG is returned to the storage tank. There is no suitable heat exchange circuit containing working fluid in this system.

  Other systems are known that do not have a heat exchange circuit. U.S. Pat. No. 5,884,488 describes an LNG pump that is located at a lower height than the LNG tank and allows the supply of LNG to the pump by gravity and by BOG. The pump is of a special design that pumps both the liquid phase and the gas phase. WO 2013/170964 describes a high pressure pump that is supplied with LPG or LNG from a primer pump in the tank with a preload of 5.4 bar.

  During navigation between ports, the weather causes differences in engine loads, and hence differences in the consumption of fuel gas by the internal combustion engine, and differences in heat input to the liquefied gas storage tank. It also occurs during the night.

JP 2009-204026 A US Pat. No. 7,690,365B2 US Pat. No. 5,884,488 WO2013 / 170964

  It is an object of the present invention to provide a fuel gas supply system that provides a very reliable fuel gas supply at high pressure.

  To this end, in the fuel gas supply system according to the present invention, at least one fuel gas pump is disposed outside the liquefied gas storage tank, and converts the liquefied gas in the liquefied gas storage tank to the liquefied gas in the liquefied gas storage tank via the tank outlet line for the liquefied gas. Being connectable, a first heat exchanger in the heat exchange circuit being connected to the fuel gas supply line between the fuel gas pump and the final heat exchanger, and a second heat exchanger in the heat exchange circuit. The heat exchanger is arranged in a liquefied gas storage tank or in a liquid gas flow line in communication with the liquefied gas in the liquefied gas storage tank.

  The liquefied gas storage tank is structured to be difficult to access when filled with liquefied gas, and due to the low temperature in the tank, all equipment located in the tank should preferably be of a simple design . There may be a single fuel gas pump or two or more fuel gas pumps, which are arranged outside the liquefied gas storage tank. For system reliability, in particular operational reliability, it is advantageous to place a fuel gas pump outside the tank, in which case access is also easier.

  The second heat exchanger does not have an operating part and is installed in the tank as a fixed structure. Alternatively, the second heat exchanger is disposed on a liquid gas flow line in communication with the liquefied gas in the liquefied gas storage tank. In the latter case, the liquid gas flows through the second heat exchanger into the liquefied gas storage tank, and in the former case, the second heat exchanger is directly connected to the liquefied gas in the liquefied gas storage tank. It works in the same way. The second heat exchanger performs cooling of the liquid gas in the tank, and this cooling causes the liquid gas to have a temperature below the boiling point of the gas. The boiling point of the gas is pressure dependent in that boiling occurs at lower temperatures when the pressure is lower. By cooling below the boiling point at the pressure in the tank, it is possible to reduce the pressure in the liquid gas and avoid the formation of gas phase gas due to boiling. Therefore, if desired, the fuel gas pump arranged outside the tank can apply a suction force to the liquid gas in the tank via the tank outlet line for the liquefied gas without causing the liquid gas to boil at the same time. . The fuel gas pump receives only liquid gas that does not contain gas phase gas, so the pump is very reliable in operation.

  The supply of fuel gas to the engine is based on the liquid gas from the liquefied gas storage tank and is not based on boil-off gas, and the fuel gas supply is independent of weather conditions and variation in consumption rate, thereby The reliability of the fuel gas supply at high pressure is improved.

  The fuel gas pressure of the fuel gas pump is preferably in the range of 200 bar to 700 bar. For some embodiments, it may be possible to use higher fuel gas pressures, such as a pressure of 750 bar. However, a maximum pressure of 700 bar limits the energy consumption used to obtain that pressure. The fuel gas is injected directly into the combustion chamber of the internal combustion engine, which usually requires a pressure above 200 bar. As a result, the fuel gas pressure of the fuel gas pump is suitably in the range of 250 bar to 450 bar.

  In a preferred embodiment, a third heat exchanger is arranged downstream of the expansion device in the heat exchange circuit and upstream of at least one fuel gas pump in the fuel gas supply line. With this arrangement, the tank outlet line passes through the third heat exchanger and is cooled by the heat exchange circuit. A working fluid, such as nitrogen, has passed through the expansion device just prior to passing through the third heat exchanger and is therefore at its lowest temperature in the heat exchange circuit. The third heat exchanger effectively ensures that the gaseous fuel in the tank outlet line reaches a minimum temperature when entering the inlet of at least one fuel gas pump.

  In one embodiment, the compressor is sized to compress the working fluid to a maximum pressure in the range of 40 bar to 120 bar. The desired pressure of the working fluid at the outlet from the compressor is a balance between achieving a high level of vacuum in the expansion device and the output required to operate the compressor. This pressure can be less than 40 bar, such as 10, 25, or 35 bar. If superior efficiency is desired, the pressure is preferably higher than the pressure at the critical point of the working fluid so that the working fluid is in a supercritical state while flowing through the first heat exchanger. Can be.

  In one embodiment, the expansion device is configured to provide a downstream pressure in the range of 1 bar to 12 bar. The desired pressure range is determined by the working fluid. Preferably, the upper limit of the pressure range is 12 bar if the working fluid at that pressure has a pressure such that it has a boiling point less than that of the liquid gas in the tank and nitrogen is used as the working fluid. The pressure corresponds to a boiling point of about −165 ° C., and a pressure of 1 bar corresponds to a boiling point of about −196 ° C. At a preferred pressure of about 5 bar at the outlet of the expansion device, nitrogen has a boiling point of about −178 ° C., so the working fluid is significantly cooler than liquid gas.

  The working fluid is liquid or predominantly liquid when flowing into the second heat exchanger. The boiling point of the working fluid at the pressure reaching the second heat exchanger is less than the temperature of the liquid gas in the liquefied gas storage tank, and the heat flux from the liquid gas to the working fluid in the second heat exchanger is Boil the working fluid. Due to the heat of vaporization consumed by the working fluid, the second heat exchanger is very efficient in cooling the liquid gas in the liquefied gas storage tank. This principle of the working fluid boiling in the second heat exchanger can be applied to all embodiments of the present invention.

  In one embodiment, the liquefied gas storage tank has a volume capacity of liquefied gas corresponding to at most 3 days of fuel gas consumption at a continuous full load of the internal combustion engine. In this embodiment, the liquefied gas storage tank is a so-called day tank that holds a small amount of fuel gas in the vicinity of the internal combustion engine. The day tank is supplied with fuel gas at an interval, such as when the liquid fuel gas level is below a predetermined level in the tank. Day tanks are typically held at atmospheric pressure or at some overpressure of a few bar. In some embodiments, the day tank may have a capacity corresponding to fuel gas consumption of less than 24 hours.

  In one embodiment, the fuel gas supply system comprises at least two liquefied gas storage tanks. One of the liquefied gas storage tanks may be a day tank, but it is also possible that two or more of the liquefied gas storage tanks are large capacity tanks. When this embodiment is installed in a liquefied gas carrier such as an LNG carrier or LPG carrier, the liquefied gas storage tank is a cargo tank or cargo such as two cargo tanks located closest to the engine room. It can be a subset of the tank. If the ship is not carrying liquefied gas as cargo, it may be appropriate to have multiple liquefied gas storage tanks, such as 2-25 or more liquefied gas storage tanks.

  In one embodiment, the heat exchange circuit comprises at least two heat exchangers disposed in at least two liquefied gas storage tanks, preferably whereby at least one second heat exchanger is connected to each liquefied gas. Located in the storage tank.

  In one embodiment, the fuel gas supply system is for an internal combustion engine that serves as a propulsion engine in a ship. Alternatively, the fuel gas supply system may be for an auxiliary engine in a ship or for an internal combustion engine that serves as a prime mover in a stationary power plant.

  In one embodiment, the vessel is selected from the group comprising container ships, bulk carriers, passenger ships, oil carriers, tankers, rolow ships, and refrigerated ships. Carrying cargo different from liquefied gas is a common feature of ships in this group, in which case the ship is equipped with a gas fuel tank in the form of a liquefied gas storage tank. A low-low vessel is a vessel with a turret that allows cargo to be driven into or out of the ship. In another embodiment, the ship is a gas carrier.

  In one embodiment, the bypass line extends from a fuel gas supply line downstream of the first heat exchanger to a liquefied gas storage tank, the bypass line comprising a bypass pump and a stop valve. When the internal combustion engine is shut down, the stop valve in the bypass line is opened and the pump can be operated to circulate cryogenic liquid gas through the tank outlet line and the bypass line so that the system It is cooled before the internal combustion engine is started, or is kept in a low temperature condition while the engine is temporarily stopped.

  Examples of embodiments of the invention are described in more detail below with reference to highly schematic drawings.

1 shows a prior art fuel gas supply system for an internal combustion engine for propelling an LNG carrier. FIG. The figure which shows the LNG carrier which has the fuel gas supply system by this invention. The figure which shows the edge part outline of the internal combustion engine in the LNG carrier of FIG. The figure which shows the fuel gas system of the internal combustion engine of FIG. FIG. 4 is a more detailed view of the fuel gas system of FIG. 3 shown for a single cylinder on the engine. 1 is a schematic view of a first embodiment of a fuel gas supply system according to the present invention. Schematic of 2nd Embodiment of a fuel gas supply system. Schematic of 3rd Embodiment of a fuel gas supply system. Schematic of 4th Embodiment of a fuel gas supply system.

  The LNG carrier shown in FIG. 2 has an internal combustion engine that serves as a main propulsion engine in an engine room 1 disposed below the upper structure 2. The engine drives a propeller 3 for propelling the ship. The LNG carrier has a plurality of, in the illustrated embodiment four LNG storage tanks, at least one or preferably a plurality of which are liquefied gas storage tanks 4 used in the fuel gas supply system according to the invention. is there. The purpose of the LNG carrier is to transport LNG from the production site to the LNG usage site, but the LNG storage tank also functions as a fuel storage unit for the internal combustion engine being transported.

  The vessel need not be an LNG carrier, but can also be any other type of vessel in which at least one liquefied gas storage tank 4 serves only as a fuel storage unrelated to the vessel's cargo. Is possible. Examples of such other types of ships are low-low ships, container ships, oil tankers, car carriers, and bulk carriers.

  In FIG. 3, the internal combustion engine is shown in more detail. The internal combustion engine is a piston engine, preferably a two-stroke crosshead internal combustion engine, indicated generally at 5. The engine can have 4-15 cylinders. Institutions can be, for example, those from MAN Diesel & Turbo and type ME-GI or MC, or from Waertsilae, or from Mitsubishi. The cylinder can have a bore, for example in the range 25-120 cm, preferably 40-110 cm. A two-stroke crosshead internal combustion engine used as the main propulsion engine typically has a speed indicated as rpm in the range of 55 to 195 rpm. These engines are called low speed engines. Low speed is required to transmit propulsion thrust via propellers to water in the ship's wake. In order to transmit thrust to the water, the propeller requires a large area and thus a large diameter. Since cavitation in the propeller is undesirable, it is necessary to limit the speed of the propulsion engine to a low speed range such as 60-200 rpm.

  The internal combustion engine 5 has a plurality of cylinders each having a reciprocating piston in the cylinder. In a two-stroke crosshead internal combustion engine, the cylinder is typically of a single flow scavenging type, an exhaust valve 6 is located at the top of the cylinder, and a scavenging port (not shown) is located at the lower end of the cylinder. Placed in. Exhaust gas from the cylinder is sent first to the exhaust gas receiver 7 and to the turbine portion of the turbocharger 8. The compressor portion of the turbocharger supplies compressed intake air to the intake chamber 9. From this chamber, the intake air passes through the intake cooler 10 to a region surrounding the scavenging port of the cylinder.

  The engine has an injection system for direct injection of pilot fuel oil and gas phase fuel gas, and for safety reasons the system for injecting fuel gas comprises an air intake system and an inert gas system . The air intake system is provided in the pipe 15 surrounding the gas fuel pipe 16, and the annular space between the two pipes enables monitoring of gas leakage from the inner pipe. Air intake is performed at 11, and air blowing is typically performed at 12 when the injection system is operating. A pair of hydrocarbon detectors 13 are arranged downstream of the engine in the conduit following the air outlet 12. A pressurized inert gas source 14 is connected to the fuel gas pipe 16 and when the engine is stopped, the inert gas is supplied to the fuel gas pipe to purge the gas from the fuel gas pipe.

  The first fuel storage unit 17 supplies pilot fuel to the fuel injectors 18 on each cylinder 19 of the internal combustion engine. The pilot fuel is supplied at a pressure such as 300 or 400 bar and is used to initiate each fuel injection sequence within the cylinder. The pilot fuel can be fuel oil and can be auto-ignited in the combustion chamber at a compression pressure that can be used in the combustion chamber at the end of the combustion stroke. When the required pilot oil pressure is detected, the gas injectors 20 on each cylinder 19 are supplied with control oil from the control oil pump 21, and the control oil pressure is supplied from the gas injector 20 to inject gas. Needed. The control oil ensures that no gas is injected into the cylinder if the pilot oil fails to be injected. The gas injector 20 is supplied with pressurized sealing oil via a sealing oil line 22. Sealing oil prevents gas from exiting the gas injector in a manner other than through a gas injection nozzle that delivers the gas into the combustion chamber.

  The fuel gas from the liquefied gas storage tank 4 is supplied to the fuel gas pipe 16 via the fuel gas supply line 25 of the fuel gas supply system, flows to the accumulator 23, and when the control valve 24 is to perform fuel gas injection. Open for fuel gas to the injector 20. There may be a common rail pipe between the fuel gas pipe 16 and the injector 20, in which case it may be possible to dispense with the accumulator 23.

  A fuel gas supply system for an internal combustion engine is illustrated in further detail in FIGS. The fuel gas supply line 25 extends from the liquefied gas storage tank 4 to the internal combustion engine 5 and has an initial section formed by a tank outlet line 26. The tank outlet line 26 extends into the tank to a region near the inner bottom of the tank and has an end opening that allows the inflow of liquid gas. There is no pump on the tank outlet line 26 in the liquefied gas storage tank 4. Instead of extending into the tank from top to bottom, the tank outlet line may extend from the bottom opening of the tank to the bottom of the tank, or the liquefied gas storage tank has a horizontal central axis and an end bottom. When configured as a cylindrical tank, it may extend from the lower part of the end bottom.

  The tank outlet line is connected to a third heat exchanger 27 in which the fuel gas in the fuel gas supply line is operated in a heat exchange circuit generally indicated at 28. Cooled by fluid. The tank outlet line is provided with a stop valve (not shown) and possibly further a check valve outside the liquefied gas storage tank 4 so that the tank can be disconnected or connected depending on the selection. Downstream of the third heat exchanger 27, the fuel gas supply line continues to the inlet of the fuel gas pump 29, which is at least the pressure required at the fuel gas inlet to the internal combustion engine 5, ie A high pressure pump that raises the fuel gas pressure to a pressure in the range of 200 bar to 700 bar, typically in the range of about 300 to 400 bar. For the internal combustion engine to perform a direct injection of gas into the combustion chamber at the end of the compression stroke, where the pressure in the combustion chamber can be, for example, 180 bar, and for the injection pressure to distribute the gas well into the combustion zone High pressure is required because it must be significantly higher.

  The fuel gas pump may have a plurality of stages, or there may be two or more fuel gas pumps connected in series or in parallel. The fuel gas pump is a cryogenic pump, examples being high pressure centrifugal LNG pumps as disclosed in Cryogenic Industries, CA, USA model TC-34, and Hydrocarbon Processing, July 2011, pages 37-41. Preferably, the fuel gas pump is a piston displacement pump having a hydraulic actuator that operates in both directions. The at least one fuel gas pump may be a combination of one piston pump and one centrifugal pump.

  From the outlet of the fuel gas pump, the fuel gas supply line 25 is connected to the first heat exchanger 30, and the fuel gas in the fuel gas supply line is converted into the heat exchange circuit 28 in the first heat exchanger 30. Heated by the working fluid. The fuel gas supply line 25 continues from the outlet of the first heat exchanger 30 to the final heat exchanger 31, in which the fuel gas has an atmosphere suitable for delivery of the fuel gas to the internal combustion engine. It is heated to a temperature above 50, preferably about 45 ° C. The final heat exchanger is supplied with heated fluid from an available source 32 that is separate from the heat exchange circuit 28.

  From the outlet of the final heat exchanger 31, the fuel gas supply line 25 is connected to the gas fuel pipe 16 in the internal combustion engine, and the fuel gas is delivered to the gas fuel pipe 16 at the fuel gas supply pressure. The fuel gas is in a supercritical state in the section of the fuel gas supply line 25 that extends from the fuel gas pump 29 to the gas fuel pipe 16.

  The heat exchange circuit 28 is a closed circuit having a circulation line 33 through which a working fluid flows. A working fluid reservoir 34 is connected to the inlet of the compressor 35 via the circulation line 33. The compressor can be a single stage compressor or a compressor having multiple stages. At the outlet of the compressor 35, the working fluid is in a supercritical stage, such as at a pressure of 100 bar, and the outlet of the compressor is connected to the inlet on the first heat exchanger 30 so that the working fluid is Preferably, the working fluid will flow in a counter flow containing fuel gas that delivers heat as it passes through the first heat exchanger.

  From the outlet of the first heat exchanger, the circulation line 33 continues to the expansion device 36, where the working fluid pressure is reduced to a low pressure, such as a pressure in the range of 1 bar to 12 bar. , Thereby bringing the working fluid to a temperature below the boiling point of the fuel gas in the fuel gas supply line 25 upstream of the fuel gas pump 29, such as at least 10 ° C. below this boiling point and preferably at least 20 ° C. below this boiling point. In one embodiment, the pressure expansion device can include an orifice nozzle disposed in the closed chamber and connected to the circulation line 33 from the first heat exchanger so that the working fluid can enter the chamber. Expands, thus reducing both the pressure and temperature of the working fluid.

  From the outlet of the expansion device 36, the circulation line 33 is connected to a third heat exchanger 27, in which the fuel gas in the fuel gas supply line is operated in the heat exchange circuit 28. Cooled by fluid. This cooling is very effective because the working fluid is at its lowest temperature in the circulation line when it exits the expansion device. Thus, the fuel gas is cooled by a considerable degree of Celsius below its boiling point, which leaves room for low pressure in the liquid fuel gas without the presence of any gas phase immediately upstream of the at least one fuel gas pump 29. leave.

  From the outlet of the third heat exchanger 27, the circulation line 33 liquefies into a second heat exchanger 37, which can be in the form of a pipe section immersed in liquid gas in the tank, such as a helical pipe section. Continue in the gas storage tank 4. The second heat exchanger extending inside the circulation line and the liquefied gas storage tank 4 is formed in one embodiment from a single length pipe set of a shape, possibly for enhanced heat exchange. With external fins, moving parts or connecting parts between separate elements inside the tank can be avoided if desired to optimize reliability in operation. In another embodiment, the second heat exchanger has an internal flow path for the working fluid and an inlet opening and an outlet opening having a fixed connection to a circulation line 33 disposed in the liquefied gas storage tank 4. It is a plate-shaped structure which has. The dashed line indicates the upper surface 38 of the liquid gas in the tank. Of course, the height of the upper surface moves downward as the fuel gas is consumed. From the second heat exchanger 37, the circulation line 33 continues to the inlet on the reservoir 34.

  The working fluid can be nitrogen that can already be used for other purposes in ships where nitrogen is used as the inert gas. Alternatively, the working fluid can be argon or helium. Typical characteristics of these working fluids are shown in Table 1, along with similar characteristics of methane typically used as fuel gas. Helium is not preferred due to its low heat of vaporization.

  A bypass line 39 is connected to the fuel gas supply line 25 downstream of the first heat exchanger 30 and extends to the liquefied gas storage tank 4 via a bypass pump 40 and a stop valve (not shown). Pump 29 is embodied by a suction chamber having a bypass conduit that is opened and closed when bypass line 39 is opened and closed so that pump 29 allows bypass flow when bypass line 39 is open for bypass. Can be done. Alternatively, the pump 29 may be of the type that allows bypassing through the pump member when stopped. When the internal combustion engine is in a stopped state, the stop valve is opened and the bypass pump 40 cools the system and the liquid gas is the fuel gas to keep the system operational when the internal combustion engine is started. Operated to be circulated through most of supply line 25.

An example of the operation of the present invention is shown below with reference to the embodiment of FIG. The gas flow rate in the fuel gas supply line 25 is considered as 1 kg / s corresponding to LNG consumption when the internal combustion engine has an output of about 27 MW. The internal combustion engine associated with the ship propulsion range at a power of about 2 MW to about 90 MW, and the fuel gas consumption rate in proportion to the type of engine, the engine bore, and the number of cylinders in the engine are proportional to the power. Nitrogen N ₂ is used as the working fluid, and the flow rate of the working fluid in the circulation line 33 is 1.7 kg / s in this example.

  The liquid gas at the position ag in the liquefied gas storage tank 4 has a pressure of about 1 bar and a temperature of about −161 ° C., and the approximately the same temperature and pressure is located just upstream of the third heat exchanger 27. Related to fuel gas in tank outlet line 26 at bg. At position cg in the fuel gas supply line 25 downstream of the heat exchanger, the fuel gas has a pressure in the range of about 0.7-1 bar and a temperature of about -176 ° C. After pressurization in at least one fuel gas pump 29, the fuel gas has a pressure of about 300 bar and a temperature of about −172 ° C. at position dg, the same pressure and temperature being for example the first heat exchanger 30. It can be found at a position just upstream. Downstream of this heat exchanger at position fg, the fuel gas has a pressure of about 300 bar and a temperature of about −12 ° C., and downstream of the final heat exchanger 31 at position gg, the fuel gas is about It has a pressure of 300 bar and a temperature of about 45 ° C.

  The working fluid at location i in reservoir 34 has a pressure of about 5 bar and a temperature of about −161 ° C., with approximately the same temperature and pressure being associated with location h immediately upstream of compressor 35. Downstream of the compressor 35 at position f, the working fluid has a pressure of about 100 bar and a temperature of about 28 ° C. Downstream of the first heat exchanger 30 at locations e and d, the working fluid has a pressure of about 100 bar and a temperature of about −152 ° C. At position c downstream of the expansion device 36, the working fluid has a pressure of about 5 bar and a temperature of about -178 ° C, and a portion of the working fluid is in the vapor phase. In the third heat exchanger, the liquid phase part evaporates and downstream of the third heat exchanger 27 at positions b and a, the working fluid has a pressure of about 5 bar and a temperature of about -178 ° C. In the second heat exchanger 37, the working fluid boils and at a position i in its downstream and storage 34, the working fluid has a pressure of about 5 bar and a temperature of about -161 ° C.

  Under these flow conditions, the compressor 35 requires an output of 310 kW, 542 kW is transferred from the working fluid to the fuel gas in the first heat exchanger 30, and 66 kW is fuel in the third heat exchanger 27. The gas is transferred to the working fluid, and 165 kW is transferred from the fuel gas to the working fluid in the second heat exchanger 33.

  In the first heat exchanger 30, the working fluid enters at a temperature of 28 ° C. and exits at −152 ° C., while the fuel gas enters at a temperature of −171 ° C. in a counter flow and exits at −12 ° C. To do. The temperature difference between these two fluids is therefore 40 ° C. at one end of the heat exchanger and 19 ° C. at the other end, and the temperature difference is smaller in the heat exchanger, but the working fluid Has a higher temperature than the fuel gas at all locations in the heat exchanger.

  In the following description of other embodiments, the same reference numerals as in the previous embodiment are used with respect to the same functional details and only the differences with respect to the first embodiment are described.

  In the second embodiment of FIG. 7, the expansion device 20 is a turbine in which the working fluid expands while the turbine is subjected to forces on its shaft. The turbine shaft is coupled to the fuel gas pump shaft, possibly via a gearbox, to save energy.

  In the third embodiment of FIG. 8, the liquefied gas storage tank 4 to which the fuel gas supply line 25 is attached is a relatively small volume day tank, so that the internal combustion engine 5 operates for several hours but less than several days. Accommodates the required fuel gas volume. Since this day tank is small in size, it is convenient to install it near the engine room. A large volume of at least one additional liquefied gas storage tank 4 is also installed, a second heat exchanger 37 is also installed in this tank, and the circulation line 33 serves as a day tank. A separate loop connecting the second heat exchanger 37 in parallel with the second heat exchanger 37, and a control valve 41 controls the flow of the working fluid to each second heat exchanger 37. Used to do. A fuel gas supply line 42 having a service pump 43 extends from near the inner bottom of the large tank to the day tank, and the day tank is a sensor that activates the service pump when the liquid level in the day tank is less than a preset value. Or it may have a level control device so that an appropriate amount of liquid fuel gas is maintained in the day tank.

  The second heat exchanger 37 in each tank maintains the gas content in the tank at a temperature lower than the boiling point of the gas. Thus, the pressure level in the tank can be maintained at an atmospheric pressure of about 1 bar, thus avoiding gas boil-off. Therefore, the fuel gas supply system does not use boil-off gas and does not have facilities for re-liquefaction of boil-off gas. The liquid gas content in the liquefied gas storage tank 4 is cooled to a lower temperature, such as a temperature near the melting point but above the melting point of the gas, so that the internal combustion engine 5 is stopped while the temperature of the liquid gas is low. Give the rising period. Since the heat flux to the tank is generated at a low speed, the engine can be stopped for a maximum of several days without boiling in the tank.

  In the fourth embodiment of FIG. 9, the second heat exchanger 37 is disposed outside the liquefied gas storage tank 4 in a liquid gas flow line generally indicated at 50. The liquid gas flow line passes through the second heat exchanger 37. The liquid gas flow line includes a suction line 44 extending downward into the liquefied gas storage tank 4 near the inner bottom of the liquefied gas storage tank 4, and the liquefied gas passes through the second heat exchanger 37 by the circulation pump 46. It communicates with the liquefied gas in the liquefied gas storage tank via a delivery line 45 that returns the liquefied gas to the tank after being flowed. Further, the liquid gas flow line 50 may be a line for transferring liquid gas from one tank to another tank, and may be embodied as a fuel gas supply line 42 having a service pump 43.

  In other embodiments, connecting the tank outlet line directly to the inlet on the at least one fuel gas pump 29 and connecting the outlet from the expansion device 36 directly to the second heat exchanger is thus third. It is possible that no heat exchanger is required.

  Each liquefied gas storage tank 4 may include an inert gas line connecting an inert gas source to the upper portion of the tank, and the inert gas line is an atmospheric pressure (about 1 atm or 1 bar) may be provided. Alternatively, the inert gas line may be connected to an inert gas source having a flexible wall, and the exterior of the flexible wall opens to the atmosphere so that atmospheric pressure is all Is present in the inert gas source and thus in the liquefied gas storage tank 4 during the operating conditions of this and thus further when the liquefied gas is cooled well below its boiling point.

  In the various embodiments described above, there are stop valves and control valves as usual in such systems, and in particular stop valves in the fuel gas supply line 25, which stop valves are open. When in position, it is possible to connect at least one fuel gas pump to the liquefied gas in the liquefied gas storage tank.

  The fuel gas supply line 25 may be made with protection in the form of an outer pipe with a diameter larger than the outer diameter of the fuel gas supply line 25, and the annular space between these pipes is vented and vented. A gas leak detector is provided at the outlet. The outer pipe also serves to prevent personnel from coming into contact with very cold surfaces.

The details of the various described embodiments can be combined into further embodiments within the scope of the claims.
The matters described in the claims at the beginning of the application are appended as they are.
[1] A fuel gas supply system for an internal combustion engine (5), comprising a liquefied gas storage tank (4), a fuel gas supply line (25), and a heat exchange circuit having a working fluid, The gas supply line includes a tank outlet line (26) for liquefied gas, at least one fuel gas pump (29) for pressurizing fuel gas to the fuel gas supply pressure for the internal combustion engine, and the at least one fuel gas pump. A final heat exchanger (31) disposed downstream of the compressor, wherein the heat exchange circuit includes a compressor (35), a first heat exchanger (30) and an expansion device (36) downstream thereof, A fuel gas supply system comprising at least a second heat exchanger disposed downstream of the expansion device;
The at least one fuel gas pump (29) is disposed outside the liquefied gas storage tank (4), and is disposed in the liquefied gas storage tank (4) via the tank outlet line (26) for liquefied gas. Being connectable to liquefied gas,
The first heat exchanger (30) in the heat exchange circuit is connected to the fuel gas supply line (25) between the fuel gas pump (29) and the final heat exchanger (31). When,
The second heat exchanger (37) in the heat exchange circuit is a liquid gas flow line communicating with the liquefied gas in the liquefied gas storage tank (4) or in the liquefied gas storage tank (4). (50) It is arrange | positioned, The fuel gas supply system characterized by the above-mentioned.
[2] The fuel gas supply system according to [1], wherein the fuel gas pressure of the fuel gas pump (29) is in a range of 200 bar to 700 bar, preferably in a range of 250 bar to 450 bar.
[3] A third heat exchanger (27) is downstream of the expansion device (36) in the heat exchange circuit and upstream of the at least one fuel gas pump (29) in the fuel gas supply line. The fuel gas supply system according to [1] or [2], which is arranged.
[4] The compressor (35) is sized to compress the working fluid to a maximum pressure in the range of 40 bar to 120 bar, according to any one of [1] to [3]. Fuel gas supply system.
[5] The fuel gas supply system according to any one of [1] to [4], wherein the expansion device (36) is configured to provide a downstream pressure in the range of 1 bar to 12 bar.
[6] The fuel gas according to any one of [1] to [5], wherein the liquefied gas storage tank (4) has a volume capacity of the liquefied gas corresponding to fuel gas consumption for a maximum of three days. Supply system.
[7] The fuel according to any one of [1] to [6], wherein the fuel gas supply system includes at least two liquefied gas storage tanks (4) such as 2 to 25 liquefied gas storage tanks. Gas supply system.
[8] The heat exchange circuit (28) comprises at least two heat exchangers (37) arranged in at least two liquefied gas storage tanks (4), preferably thereby at least one second The fuel gas supply system according to [7], wherein the heat exchanger is disposed in each liquefied gas storage tank.
[9] The fuel gas supply system according to any one of [1] to [7], wherein the fuel gas supply system is for an internal combustion engine (5) that serves as a propulsion engine in a ship.
[10] The fuel gas supply system according to [9], wherein the ship is selected from the group comprising a container ship, a bulk carrier, a passenger ship, an oil ship, a tanker, a low-low ship, and a refrigerated ship.
[11] A bypass line (39) extends from the fuel gas supply line (25) downstream of the first heat exchanger (30) to the liquefied gas storage tank (4), and the bypass line is The fuel gas supply system according to [8] or [9], comprising a bypass pump (40) and a stop valve.
[12] The fuel gas supply system according to any one of [1] to [11], wherein the liquefied gas storage tank (4) is connected to an inert gas source at atmospheric pressure.

Claims (11)

A fuel gas supply system for an internal combustion engine (5), comprising a liquefied gas storage tank (4), a fuel gas supply line (25), and a heat exchange circuit having a working fluid, said fuel gas supply line A liquefied gas tank outlet line (26), at least one fuel gas pump (29) for pressurizing fuel gas to the fuel gas supply pressure for the internal combustion engine, and downstream of the at least one fuel gas pump A final heat exchanger (31) arranged, the heat exchange circuit comprising a compressor (35), a first heat exchanger (30) and an expansion device (36) downstream thereof, and the expansion device And a second heat exchanger disposed downstream of the fuel gas supply system,
The at least one fuel gas pump (29) is disposed outside the liquefied gas storage tank (4), and is disposed in the liquefied gas storage tank (4) via the tank outlet line (26) for liquefied gas. Being connectable to liquefied gas,
The first heat exchanger (30) in the heat exchange circuit is connected to the fuel gas supply line (25) between the fuel gas pump (29) and the final heat exchanger (31). When,
The second heat exchanger (37) in the heat exchange circuit is a liquid gas flow line communicating with the liquefied gas in the liquefied gas storage tank (4) or in the liquefied gas storage tank (4). (50) ,
A third heat exchanger (27) is disposed downstream of the expansion device (36) in the heat exchange circuit and upstream of the at least one fuel gas pump (29) in the fuel gas supply line. A fuel gas supply system. The fuel gas supply system according to claim 1, wherein the pressure of the fuel gas of the fuel gas pump (29) is in the range of 200 bar to 700 bar, preferably in the range of 250 bar to 450 bar. The fuel gas supply system according to claim 1 or 2 , wherein the compressor (35) is sized to compress the working fluid to a maximum pressure in the range of 40 bar to 120 bar. The inflation device (36) is configured to provide a downstream pressure in the range of 1 bar to 12 bar, the fuel gas supply system according to any one of claims 1 to 3. The fuel gas supply system according to any one of claims 1 to 4 , wherein the liquefied gas storage tank (4) has a volume capacity of liquefied gas corresponding to fuel gas consumption for a maximum of three days. The fuel gas supply system, even without least comprises two liquefied gas storage tank (4), a fuel gas supply system according to any one of claims 1 to 5. The heat exchange circuit (28) comprises at least two heat exchanger (37) disposed on at least two liquefied gas storage tank (4) within the Re its, at least one second heat exchanger The fuel gas supply system according to claim 6 , which is disposed in each liquefied gas storage tank. The fuel gas supply system according to any one of claims 1 to 6 , wherein the fuel gas supply system is for an internal combustion engine (5) that serves as a propulsion engine in a ship. 9. The fuel gas supply system according to claim 8 , wherein the ship is selected from the group comprising a container ship, a bulk carrier, a passenger ship, an oil carrier, a tanker, a low-low ship, and a refrigerated ship. A bypass line (39) extends from the fuel gas supply line (25) downstream of the first heat exchanger (30) to the liquefied gas storage tank (4), and the bypass line includes a bypass pump ( 40) and a fuel gas supply system according to claim 7 or 8 , comprising a stop valve. The liquefied gas storage tank (4) is connected to a source of inert gas at atmospheric pressure, the fuel gas supply system according to any one of claims 1 1 0.

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