Power generation system for vessel

Abstract

To suppress sulfuric acid dew point corrosion generated on a heat transfer surface of a heater when using exhaust gas of an internal combustion engine that uses oil fuel containing large amount of sulfur contents such as heavy oil as heat source fluid in an organic Rankine cycle power generation system for a vessel that recovers heat from two types or more of heat source fluid with different temperatures by using the heater.SOLUTION: A power generation system 1 for a vessel includes: a circulation circuit LC for circulating a working medium R; a first heater 10 that heats the working medium R by using supercharged air A2 from a supercharger 64; a second heater 12 that heats the working medium R heated by the first heater 10; a bypass passage LB that causes the working medium R to bypass the second heater 12 and / or causes exhaust gas E2 to bypass the second heater 12; heating mode switching means V1-V4; and control means 30. In single supply of oil fuel, a heating stop mode is executed in a period when a detection temperature is below a set temperature, and the mode is transferred to a heating operation mode when the detection temperature exceeds the set temperature.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a marine power generation system. [Background technology]

[0002] Conventionally, marine power generation systems using an organic Rankine cycle have been known. For example, Patent Document 1 describes an energy recovery device that recovers thermal energy from exhaust gas flowing through an exhaust gas passage 3 from an engine EG of a ship fueled by heavy oil C toward a funnel ST to generate electricity. In this energy recovery device, in order to prevent corrosion of the exhaust gas passage 3 and the like downstream of the heater 16, the amount of heat transferred from the exhaust gas to the working medium is adjusted so that the exhaust gas temperature downstream of the heater 16 is equal to or higher than a set temperature. Specifically, the flow rate of the working medium passing through the heater 16 is adjusted by adjusting the rotation speed of a pump 14 or opening and closing a bypass valve 57 provided in a bypass passage 56 to the heater 16. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-132192 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, an increasing number of LNG carriers have been equipped with dual-fuel diesel engines that can run on both LNG and heavy fuel oil. When using heavy fuel oil with a high sulfur content to recover heat from the exhaust gas of the internal combustion engine using a heat exchanger (heater for the working fluid), there is a concern that sulfuric acid dew-point corrosion will occur not only in the exhaust gas passage but also on the heat transfer surface of the heater. If the heater is damaged by corrosion, there is also a risk that the working fluid will leak inside the ship.

[0005] Therefore, an object of the present invention is to suppress sulfuric acid dew-point corrosion that occurs on the heat transfer surface of a heater in an organic Rankine cycle power generation system for a ship that recovers heat from two or more types of heat source fluids with different temperatures using a heater, when the heat source fluid is exhaust gas from an internal combustion engine that uses oil fuel containing a high sulfur content, such as heavy oil. [Means for solving the problem]

[0006] The marine power generation system of the present invention includes a circulation circuit for circulating a working medium having a boiling point lower than that of water, a circulation pump for circulating the working medium in the circulation circuit, a first heater for heating the working medium from the circulation pump using supercharged air from a supercharger attached to an internal combustion engine as a heat source fluid, a second heater for heating the working medium after being heated in the first heater using exhaust gas from the internal combustion engine as a heat source fluid, an expander rotated by the expansion energy of the working medium after being heated in the second heater, a cooler for cooling the working medium after passing through the expander with a cooling fluid, a generator connected to the expander and driven by the rotation of the expander, one or two bypass paths for bypassing the working medium from the second heater and / or bypassing exhaust gas from the second heater, a heating operation mode in which the working medium and exhaust gas are simultaneously circulated through the second heater, and a heating operation mode in which at least one of the working medium and the exhaust gas is simultaneously circulated through the second heater. a temperature detection means for detecting the temperature of the working medium after it has flowed out of the first heater; a fuel type information acquisition means for acquiring information on the type of fuel supplied to the internal combustion engine; and a control means for controlling the operation of the power generation system, wherein when power generation operation is started, under the condition that the fuel type information acquired by the fuel type information acquisition means is a single supply of oil fuel, the control means (i) controls the heating mode switching means to execute the heating stop mode while the temperature detected by the temperature detection means is below a set temperature after the circulation pump is started, and (ii) controls the heating mode switching means to transition from the heating stop mode to the heating operation mode when the temperature detected by the temperature detection means exceeds the set temperature, and the set temperature is selected based on the resistance to sulfuric acid dew-point corrosion of the metal material constituting the heat transfer surface of the second heater. [Effects of the Invention]

[0007] According to the marine power generation system of the present invention, in an organic Rankine cycle power generation system for a marine vessel that recovers heat from two or more types of heat source fluids with different temperatures using a heater, when the heat source fluid is exhaust gas from an internal combustion engine that uses oil fuel with a high sulfur content, such as heavy oil, sulfuric acid dew-point corrosion that occurs on the heat transfer surface of the heater can be suppressed. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing a marine power generation system according to an embodiment of the present invention; [Figure 2] FIG. 10 is a diagram showing a marine power generation system according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] 1 and 2 are schematic diagrams illustrating a marine power generation system 1 according to an embodiment of the present invention. The bypass passage provided in FIG. 1 differs from that in FIG. 2. The bypass passage will be described later. The marine power generation system 1 according to this embodiment is a system that generates power through an organic Rankine cycle (ORC) using exhaust heat from a marine vessel 100, and uses supercharged air and exhaust gas generated by the operation of an internal combustion engine 60 as heat source fluids. An ORC power generation system is also called a binary power generation system because it generates power using two thermal cycles: a heat source fluid system and a working medium system.

[0010] 1. Configuration of main and auxiliary engines of a ship The ship 100 of this embodiment is, for example, an LNG (liquefied natural gas) carrier, and is equipped with an internal combustion engine 60 that generates propulsion power for the hull, a fuel supply means 62 that supplies fuels F1 and F2 to the internal combustion engine 60, a supercharger 64 that supplies supercharged air A2 to the internal combustion engine 60, and an exhaust turbine 66 that is connected to the supercharger 64 and rotated by exhaust gas E1 from the internal combustion engine 60.

[0011] The internal combustion engine 60 is a two-stroke diesel engine known as the main engine. The internal combustion engine 60 can use a portion of the LNG cargo in addition to heavy oil as fuel, and the fuel supply means 62 is composed of a first fuel supply means 62A having an LNG tank and a vaporizer, and a second fuel supply means 62B having a heavy oil tank and a preheater. The first fuel supply means 62A is connected to the internal combustion engine 60 via a first fuel line LF1. The second fuel supply means 62B is connected to the internal combustion engine 60 via a second fuel line LF2. In the figure, LNG is indicated by the symbol F1, and heavy oil is indicated by the symbol F2.

[0012] The internal combustion engine 60 switches between three combustion modes depending on the navigation conditions of the ship 100, etc. Specifically, the first combustion mode is an LNG-only combustion mode in which only LNG, which is the gas fuel F1, is supplied. The second combustion mode is an LNG-heavy oil mixed combustion mode in which heavy oil, which is the oil fuel F2, and LNG, which is the gas fuel F1, are supplied simultaneously. The third combustion mode is a heavy oil-only combustion mode in which only heavy oil, which is the oil fuel F2, is supplied.

[0013] The turbocharger 64 is a device that draws in air A1 from outside the ship by operating an exhaust turbine 66 and compresses this air A1 to generate turbocharged air A2. An intake section of the turbocharger 64 is connected to an air filter (not shown) via an intake line LA3. A discharge section of the turbocharger 64 is connected to an inlet section of a high-temperature side flow path of the intercooler 70 via a first air supply line LA1.

[0014] The intercooler 70 is a heat exchanger that removes heat of compression contained in the supercharged air A2 by heat exchange with cooling water W1. An outlet of the high-temperature side flow passage of the intercooler 70 is connected to an inlet of a Venturi mixer 72 via a second air supply line LA2. A first cooling water line LW1 is connected to the low-temperature side flow passage of the intercooler 70, through which seawater pumped from the ocean area where the ship is navigating or fresh water circulated in the ship's central cooling facility flows in and out as cooling water W1.

[0015] The venturi mixer 72 is a device that uses the supercharged air A2 as a driving fluid to draw in fuels F1 and F2 by utilizing the Venturi effect of the air flow, thereby generating an air-fuel mixture. The generated air-fuel mixture is supplied to the combustion chamber of the internal combustion engine 60. The exhaust chamber 74 is a device that uses the kinetic energy of the combustion gas that continuously flows out of the combustion chamber to increase the charging efficiency of the air-fuel mixture. While the internal combustion engine 60 is running, the combustion gas that flows into the exhaust chamber 74 expands within the chamber and is discharged as exhaust gas E1. The outlet of the exhaust chamber 74 is connected to the inlet of the exhaust turbine 66 via a first exhaust gas line LE1.

[0016] The exhaust turbine 66 is a device that recovers a portion of the thermal energy of the exhaust gas E1 discharged from the exhaust chamber 74 and drives the turbocharger 64. Inside the exhaust turbine 66, the expansion energy of the exhaust gas E1 is converted into kinetic energy, which drives the rotating shaft of the impeller. The rotating shaft of the impeller drives the rotating shaft of the turbocharger 64, which is connected by a coupling or the like. An outlet of the exhaust turbine 66 is connected to the funnel of the ship 100 via a second exhaust gas line LE2, and the exhaust gas E2, after having had its heat recovered by a second heater 12 described later, is discharged overboard from the funnel.

[0017] The marine power generation system 1 of this embodiment may also include an exhaust gas economizer. The exhaust gas economizer is a type of steam generator that utilizes the thermal energy of the exhaust gas E2 that has passed through the exhaust turbine 66, and together with a steam-water separation drum (not shown), constitutes an exhaust gas boiler. When the exhaust gas economizer is included, a large number of steam pipes (heat transfer pipes) are arranged inside a shell through which the exhaust gas E2 flows. One side of each steam pipe is connected to a feedwater header for distributing feedwater, and the other side of each steam pipe is connected to a steam header for collecting steam. A feedwater line is connected to the feedwater header for introducing water stored in the steam-water separation drum as feedwater. Meanwhile, a steam line is connected to the steam header for returning the generated steam to the steam-water separation drum. The steam after separation in the steam-water separation drum is used for preheating heavy oil, etc. The shell outlet of the exhaust gas economizer is connected to the chimney of the ship 100 via an exhaust gas line, and the exhaust gas after heat recovery is discharged overboard from the chimney.

[0018] 2. Configuration of marine power generation system The marine vessel power generation system 1 of this embodiment includes a circulation pump 22, a first heater 10, a second heater 12, an expander 16, and a cooler 20. These devices are connected in the order mentioned above in a circular manner by a circulation circuit LC for the working medium R. This circulation circuit LC is laid over a wide area in both horizontal and vertical directions within the ship, and can therefore also be referred to as a transport pipeline for the working medium R. The marine vessel power generation system 1 also includes control means 30 for controlling the operation of the system.

[0019] A polymer organic compound having a boiling point lower than that of water is used as the working fluid R circulating through the circulation circuit LC. The working fluid R is, for example, a fluorocarbon-based medium such as HFC-245fa (chemical name: 1,1,1,3,3-pentafluoropropane, boiling point at 1 atmosphere: 15.3°C). Non-fluorocarbon-based mediums such as isopentane (boiling point at 1 atmosphere: 27.8°C) and pentane (boiling point at 1 atmosphere: 36.1°C) may also be used. Note that the working fluid R may be mixed with a lubricating oil having a boiling point higher than that of the polymer organic compound in order to reduce friction and cool the expander 16.

[0020] The circulation pump 22 is a device for circulating the working medium R containing lubricating oil through the circulation circuit LC, and is driven by, for example, an inverter device 40. In this embodiment, the rotation speed of the drive motor of the circulation pump 22 is adjusted using the variable voltage and variable frequency control function of the inverter device 40.

[0021] The first heater 10 is a heater for heating the working medium R (liquid medium R) delivered from the circulation pump 22. L ). The high-temperature side flow path of the first heater 10 is connected to the middle of the first air supply line LA1, and uses the supercharged air A2 from the supercharger 64 as a heat source fluid to heat the working medium R flowing through the low-temperature side flow path. The first heater 10 operates as an evaporator by adjusting the flow rate of the working medium R supplied from the circulation pump 22. That is, the liquid medium flowing in from the inlet of the low-temperature side flow path of the first heater 10 becomes saturated steam (wet steam) or superheated steam due to the heat input from the supercharged air A2.

[0022] The second heater 12 is a heater for heating the working medium R (medium gas R G ). The high-temperature side flow path of the second heater 12 is connected to the middle of the second exhaust gas line LE2, and uses the exhaust gas E2 from the exhaust turbine 66 as a heat source fluid to heat the working medium R flowing through the low-temperature side flow path. The second heater 12 operates as a superheater by adjusting the flow rate of the working medium R supplied from the circulation pump 22. That is, saturated steam or superheated steam flowing in from the inlet of the low-temperature side flow path of the second heater 12 is further superheated by the heat input from the exhaust gas E2, and becomes even higher-temperature superheated steam before flowing out from the outlet.

[0023] The expander 16 is configured to expand the working medium R (medium gas R) in a superheated state. GThe expander 16 is a device that converts the expansion energy of the compressor (16) into kinetic energy and drives a rotating shaft. The main body of the expander 16 has, for example, a twin-screw type expansion mechanism. The rotating shaft of the screw rotor is driven by the rotating shaft of the generator 18 connected by a coupling or the like. The expander 16 may have another expansion mechanism such as a turbine, and may be either an oil-lubricated type or an oil-free type.

[0024] The cooler 20 cools the working medium R (medium gas R) whose temperature has been lowered and whose volume has been increased by the expander 16. G ) is a heat exchanger that condenses the working medium R. The high-temperature side flow path of the cooler 20 is connected to the middle of the circulation circuit LC, and cools the working medium R using cooling water W2 as a cooling fluid. A second cooling water line LW2 is connected to the low-temperature side flow path of the cooler 20, through which seawater pumped from the sea area during navigation or fresh water circulated in the ship's central cooling facility flows in and out as cooling water W2. Note that the second cooling water line LW2 may be provided with a cooling water pump as needed.

[0025] The generator 18 is connected to the expander 16 and is driven by the working medium R expanding in the expansion space to rotate the screw rotor. The generator 18 in this embodiment is, for example, a permanent magnet synchronous generator. This permanent magnet synchronous generator has a rotating shaft connected to one side of the screw rotor, and generates electric power by rotating this rotating shaft in conjunction with the rotation of the screw rotor.

[0026] A temperature detection means 44 is provided near the outlet of the low-temperature side flow path of the first heater 10. The temperature detection means 44 is a sensor that detects the temperature of the working medium R immediately after it flows out of the first heater 10. Each detection signal of the temperature detection means 44 is input to the control means 30, which will be described later.

[0027] The control means 30 includes a circulation flow rate control unit 31 and a fuel type information acquisition means 32. The circulation flow rate control unit 31 controls the rotation speed of the circulation pump 22 using the inverter device 40 so that the first heater 10 operates as an evaporator and the second heater 12 operates as a superheater. The load factor information acquisition unit 32 acquires information related to the load factor of the internal combustion engine 60. The fuel type information acquisition means 32 acquires information related to the type of fuel supplied to the internal combustion engine 60. Specifically, the fuel type information acquisition means 33 identifies the fuel type using combustion mode information of the internal combustion engine 60 (single-fuel LNG combustion mode, LNG / heavy oil mixed combustion mode, or single-fuel heavy oil combustion mode).

[0028] Here, the mechanisms of heat recovery and power generation will be explained. The working medium R is pressurized by driving the circulation pump 22, and flows through the circulation circuit LC in the direction of the arrows shown in FIG. 1. The working medium R is heated in the first heater 10 and the second heater 12 by heat recovery from the heat source fluid (supercharged air A2, exhaust gas E2) described above, and becomes superheated steam. The working medium R that has become high-temperature, high-pressure superheated steam G The working medium R, which has become low-temperature, low-pressure expanded vapor after passing through the screw rotor, rotates the screw rotor of the expander 16 to drive the generator 18. G The working medium R is cooled in the cooler 20 and becomes a condensate. L is again fed to the first heater 10 and the second heater 12 by the circulation pump 22. In this way, the working medium R repeatedly changes state while circulating through the circulation circuit LC, thereby enabling the thermal energy to be converted into electrical energy.

[0029] 3. Bypass switching control for working medium and exhaust gas The marine vessel power generation system 1 of this embodiment includes one or two bypass paths LB for bypassing the working medium R from the second heater 12 and / or bypassing the exhaust gas E2 from the second heater 12. The bypass paths LB include a first bypass path LB1 and a second bypass path LB2. The first bypass path LB1 is the bypass path LB for bypassing the working medium R. The second bypass path LB2 is the bypass path LB for bypassing the exhaust gas E2. FIG. 1 shows a marine vessel power generation system 1 including only the first bypass path LB1. FIG. 2 shows a marine vessel power generation system 1 including only the second bypass path LB2. Note that both the first bypass path LB1 and the second bypass path LB2 may be provided in a single marine vessel power generation system 1.

[0030] The marine vessel power generation system 1 also includes a heating mode switching means, which is a valve mechanism that switches between a heating operation mode in which the working medium R and the exhaust gas E2 are simultaneously circulated through the second heater 12, and a heating stop mode in which at least one of the working medium R and the exhaust gas E2 is circulated through the bypass line LB.

[0031] The first bypass passage LB1 shown in FIG. 1 branches off from the circulation circuit LC downstream of the temperature detection means 44 and upstream of the second heater 12. A two-way valve V1 constituting the heating mode switching means is provided downstream of this branching point and upstream of the second heater 12. The first bypass passage LB1 merges with the circulation circuit LC downstream of the second heater 12 and upstream of the oil separator 14. The first bypass passage LB1 is provided with a two-way valve V2 constituting the heating mode switching means. The two-way valves V1 and V2 can be, for example, ball-type motor-operated valves. Instead of the two-way valves V1 and V2, a three-way valve may be provided at the branching point of the first bypass passage LB1.

[0032] On the other hand, the second bypass passage LB2 shown in FIG. 2 branches off from the second exhaust gas line LE2 upstream of the second heater 12. A two-way valve V3 constituting the heating mode switching means is provided downstream of this branching point and upstream of the second heater 12. The second bypass passage LB2 merges with the second exhaust gas line LE2 downstream of the second heater 12. The second bypass passage LB2 is provided with a two-way valve V4 constituting the heating mode switching means. The two-way valves V3 and V4 can be, for example, butterfly damper valves. Note that instead of the two-way valves V3 and V4, a three-way valve may be provided at the branching point of the second bypass passage LB2.

[0033] The control means 30 refers to information on the fuel type acquired by the fuel type information acquisition unit 32. If the information indicates that only oil fuel is being supplied (i.e., the internal combustion engine 60 is operating in heavy oil mono-fuel mode), the control means 30 executes control operation A, which will be described later. If the information indicates that oil fuel and gas fuel are being supplied simultaneously (i.e., the internal combustion engine 60 is operating in LNG-heavy oil mixed-fuel mode), the control means 30 executes control operation B, which will be described later. If the information indicates that only gas fuel is being supplied (i.e., the internal combustion engine 60 is operating in LNG mono-fuel mode), the control means 30 executes control operation C, which will be described later. By selecting control operations A to C, the amount of heat input to the second heater 12 (i.e., the amount of cooling of the exhaust gas E2) is adjusted according to the fuel type.

[0034] 3.1 Control Action A In this control operation A, the control means 30 (i) controls the heating mode switching means to execute the heating stop mode while the temperature detected by the temperature detection means 44 is below the set temperature after the circulation pump 22 is started, and (ii) controls the heating mode switching means to transition from the heating stop mode to the heating operation mode when the temperature detected by the temperature detection means 44 exceeds the set temperature.

[0035] Specifically, in the initial state during the cold state, the control means 30 executes the heating stop mode by opening the two-way valves V2 and V4 as bypass valves, closing the two-way valves V1 and V3 as inlet shutoff valves, and stopping the circulation pump 22. As will be described later, the heating stop mode is entered when power generation ends, and so this mode is maintained in the initial state.

[0036] When the power generation operation starts, the control means 30 starts the circulation pump 22 and increases the speed to a specified number of revolutions, and when the set temperature is reached, the control means 30 opens the inlet shutoff valves (two-way valves V1 and V3) and closes the bypass valves (two-way valves V2 and V4), thereby transitioning to a heating operation mode. In the heating operation mode, the working medium R and the exhaust gas E2 are circulated through the second heater 12, and as heat exchange progresses, the working medium R is heated and the exhaust gas E2 is cooled.

[0037] Here, the set temperature is selected based on the resistance to sulfuric acid dew-point corrosion of the metal material that constitutes the heat transfer surface of the second heater 12. That is, if the corrosion resistance to sulfuric acid of the metal material that constitutes the heat transfer surface of the second heater 12 is relatively low, the set temperature is set to a higher first set temperature (e.g., 100°C), and if the corrosion resistance is relatively high, the set temperature is set to a lower second set temperature (e.g., 80°C).

[0038] In addition, when the control means 30 terminates the power generation operation, (i) it controls the heating mode switching means to transition from the heating operation mode to the heating stop mode, and (ii) after transitioning to the heating stop mode, it stops the circulation pump 22.

[0039] Specifically, upon termination of the power generation operation, the control means 30 opens the bypass valves (two-way valves V2 and V4), closes the inlet shutoff valves (two-way valves V1 and V3), and decelerates the rotation speed of the circulation pump 22 to zero and stops it, thereby transitioning to a heating stop mode. In the heating stop mode, the working medium R or the exhaust gas E2 is bypassed from the second heater 12, so that cooling of the exhaust gas E2 does not progress.

[0040] 3.2 Control Action B In this control operation B, the control means 30 changes the set temperature to a lower correction temperature. This correction temperature can be set to a value approximately 10 to 20°C lower than the first set temperature and the second set temperature described above. Control operation B is the same as control operation A, except for the set temperature.

[0041] 3.3 Control Action C In this control operation C, the control means 30 controls the heating mode switching means to execute the heating operation mode regardless of the temperature detected by the temperature detection means 44. That is, the control means 30 keeps the inlet shutoff valves (two-way valves V1 and V3) always open and the bypass valves (two-way valves V2 and V4) always closed.

[0042] The marine power generation system according to the embodiment described above provides the following advantages.

[0043] (1) The marine power generation system 1 includes a circulation circuit LC that circulates a working medium R having a boiling point lower than that of water, a circulation pump 22 that circulates the working medium R within the circulation circuit LC, a first heater 10 that heats the working medium from the circulation pump 22 using supercharged air from a supercharger 64 attached to an internal combustion engine 60 as a heat source fluid, a second heater 12 that heats the working medium R after being heated by the first heater 10 using exhaust gas from the internal combustion engine 60 as a heat source fluid, and a second heater 12 that heats the working medium R after being heated by the expansion energy of the working medium R after being heated by the second heater 12. an expander 16 rotated in a direction perpendicular to the axis of rotation of the expander 16; a cooler 20 for cooling the working medium R after passing through the expander 16 with a cooling fluid; a generator 18 connected to the expander 16 and driven by the rotation of the expander 16; one or two bypass paths LB for bypassing the working medium R from the second heater 12 and / or bypassing the exhaust gas E2 from the second heater 12; a heating operation mode in which the working medium R and the exhaust gas E2 are simultaneously circulated through the second heater 12; the heating mode switching means (two-way valves V1 to V4) for switching between a heating stop mode and a heating operation mode in which the working medium R flows through the bypass line LB, a temperature detection means 44 for detecting the temperature of the working medium R after it has flowed out of the first heater 10, a fuel type information acquisition means 33 for acquiring information on the type of fuel supplied to the internal combustion engine 60, and a control means 30 for controlling the operation of the power generation system 1, wherein when starting power generation operation, under the condition that the fuel type information acquired by the fuel type information acquisition means 33 is a single supply of oil fuel, the control means 30 (i) controls the heating mode switching means (two-way valves V1 to V4) to execute the heating stop mode while the temperature detected by the temperature detection means 44 is below a set temperature after the start of the circulation pump 22, and (ii) controls the heating mode switching means (two-way valves V1 to V4) to transition from the heating stop mode to the heating operation mode when the temperature detected by the temperature detection means 44 exceeds the set temperature, and the set temperature is selected based on the resistance to sulfuric acid dew-point corrosion of the metal material constituting the heat transfer surface of the second heater 12.

[0044] When the internal combustion engine 60 is operating in an oil-only combustion mode (e.g., burning heavy oil containing sulfur), after the circulation pump 22 is started to start the power generation operation, the heating stop mode is executed so that either the working medium R or the exhaust gas E2 is circulated through the bypass path LB while the detected temperature of the working medium R flowing out from the first heater 10 is below a set temperature. After the circulation pump 22 is started, the speed of the circulation pump 22 is increased at a constant acceleration via the flow rate adjustment means 40 (inverter device) until it reaches a rated rotation speed, for example, and during that time, the working medium R is preheated in the first heater 10. When the preheating of the working medium R progresses and the detected temperature of the working medium R flowing out from the first heater 10 exceeds the set temperature, the circulation pump 22 is switched to a heating operation mode so that both the working medium R and the exhaust gas E2 are circulated through the second heater 12.

[0045] In bypass operation at a first set temperature (e.g., 100°C), which is applied when the corrosion resistance to sulfuric acid of the metal material constituting the heat transfer surface of the second heater 12 is relatively low, sulfuric acid dew-point corrosion can be effectively prevented by avoiding condensation on the heat transfer surface of the second heater 12. In addition, in bypass operation at a second set temperature (e.g., 80°C), which is applied when the corrosion resistance to sulfuric acid of the metal material constituting the heat transfer surface of the second heater 12 is relatively high, condensation may occur on the heat transfer surface of the second heater 12, but sulfuric acid dew-point corrosion can be avoided due to the high corrosion resistance of the metal material.

[0046] (2) In the marine power generation system 1 described above in (1), when the power generation operation is terminated, the control means 30 (i) controls the heating mode switching means (two-way valves V1 to V4) to transition from the heating operation mode to the heating stop mode, and (ii) stops the circulation pump 22 after transitioning to the heating stop mode.

[0047] When the power generation operation is terminated, the heating operation mode is switched to the heating stop mode prior to the deceleration and stopping of the circulation pump 22, and either the working medium R or the exhaust gas E2 is circulated through the bypass path LB. Thereafter, the circulation pump 22 is gradually decelerated and finally stopped.

[0048] If the circulation pump 22 is slowed down toward stopping while in the heating operation mode, the working medium R, whose flow rate has decreased, may become overheated in the second heater 12, which may cause damage to the expander 16 due to thermal fatigue. By bypassing either the working medium R or the exhaust gas E2 and then stopping the circulation pump 22, it is possible to prevent overheating of the working medium R and, in turn, avoid thermal fatigue of the expander 16.

[0049] (3) In the marine power generation system 1 described above in (1) or (2), when the control means 30 starts power generation operation, if the fuel type information acquired by the fuel type information acquisition means 33 indicates that oil fuel and gas fuel are being supplied simultaneously, the control means 30 changes the set temperature to a lower correction temperature.

[0050] When the internal combustion engine 60 is operating in an oil-gas mixed combustion mode (burning heavy oil containing sulfur and LNG containing no sulfur, etc.), the concentration of sulfur oxides (SO3) in the exhaust gas is lower than when it is operating in an oil-only combustion mode, so the set temperature is changed to a lower correction temperature. Although lowering the set temperature may cause condensation on the heat transfer surface of the second heater 12, the amount of sulfuric acid attached is reduced, making it possible to avoid sulfuric acid dew-point corrosion.

[0051] (4) In the marine power generation system 1 described above in (1) to (3), when power generation operation is started, the control means 30 controls the heating mode switching means (two-way valves V1 to V4) to execute the heating operation mode regardless of the temperature detected by the temperature detection means 44, provided that the fuel type information acquired by the fuel type information acquisition means 33 indicates a single supply of gas fuel.

[0052] When the internal combustion engine 60 is operated in a gas-only combustion mode (such as burning sulfur-free LNG), sulfur oxides (SO3) are not generated, so bypass operation is not performed regardless of the detected temperature. After the circulation pump 22 is started, the working medium R can be preheated using both the first heater 10 and the second heater 12, so power generation can be started in a short time.

[0053] [Contribution to the United Nations-led Sustainable Development Goals (SDGs)] The marine power generation system disclosed herein can contribute to achieving Goal 7 of the Sustainable Development Goals (SDGs), "Affordable and clean energy," and Goal 13, "Take urgent action to combat climate change." [Explanation of symbols]

[0054] 1. Marine power generation systems 10 1st heater 12 Second heater 16 Expander 18 Generator 20 Cooler 22 Circulation pump 30 Control Means 32 Fuel type information acquisition means 44 Temperature detection means 60 Internal combustion engine 64 Supercharger A2 Supercharged air E2 exhaust gas R Working medium LC circulation circuit LB Bypass LB1 First Bypass LB2 Second Bypass V1, V2, V3, V4 two-way valve (heating mode switching means)

Claims

1. a circulation circuit for circulating a working medium having a boiling point lower than that of water; a circulation pump that circulates the working medium through the circulation circuit; a first heater that uses supercharged air from a supercharger attached to the internal combustion engine as a heat source fluid to heat the working medium from the circulation pump; a second heater that uses exhaust gas from the internal combustion engine as a heat source fluid to heat the working medium heated by the first heater; an expander that is rotated by expansion energy of the working medium heated by the second heater; a cooler that cools the working medium after passing through the expander with a cooling fluid; a generator connected to the expander and driven by rotation of the expander; one or two bypass paths for bypassing the working medium from the second heater and / or for bypassing the exhaust gas from the second heater; a heating mode switching means for switching between a heating operation mode in which the working medium and the exhaust gas are simultaneously circulated through the second heater and a heating stop mode in which at least one of the working medium and the exhaust gas is circulated through the bypass passage; a temperature detection means for detecting the temperature of the working medium after it has flowed out of the first heater; a fuel type information acquisition means for acquiring information about the type of fuel supplied to the internal combustion engine; a control means for controlling the operation of the power generation system, When starting the power generating operation, the control means Under the condition that the fuel type information acquired by the fuel type information acquisition means is a single supply of oil fuel, (i) controlling the heating mode switching means to execute the heating stop mode during a period in which the temperature detected by the temperature detection means is lower than a set temperature after the start of the circulation pump; (ii) controlling the heating mode switching means to transition from the heating stop mode to the heating operation mode when the temperature detected by the temperature detection means exceeds the set temperature; A marine power generation system, wherein the set temperature is selected based on the resistance to sulfuric acid dew-point corrosion of the metal material that constitutes the heat transfer surface of the second heater.

2. When the power generating operation is to be terminated, the control means (i) controlling the heating mode switching means to transition from the heating operation mode to the heating stop mode; (ii) After transitioning to the heating stop mode, stopping the circulation pump The marine power generation system according to claim 1 .

3. When starting the power generating operation, the control means When the fuel type information acquired by the fuel type information acquisition means indicates that oil fuel and gas fuel are being supplied simultaneously, the set temperature is changed to a lower correction temperature.

3. A marine power generation system according to claim 1 or 2.

4. When starting the power generating operation, the control means When the fuel type information acquired by the fuel type information acquisition means indicates a single supply of gas fuel, the heating mode switching means is controlled to execute the heating operation mode regardless of the temperature detected by the temperature detection means.

3. A marine power generation system according to claim 1 or 2.

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