Marine power generation system

Abstract

Provided is an organic Rankine cycle power generation system for a ship in which heat is recovered from two or more heat source fluids having different temperatures by means of a heater, the organic Rankine cycle power generation system being configured so that when exhaust gas from an internal combustion engine using an oil fuel containing a large amount of sulfur, such as heavy oil, is used as a heat source fluid. Sulfuric acid dew point corrosion generated on a heat transfer surface of a heater is suppressed. This marine power generation system is provided with: a circulation circuit that circulates a working medium; a first heater that heats the working medium with pressurized air from the supercharger; a second heater that heats the working medium heated by the first heater; a bypass path that bypasses the working medium with respect to the second heater and / or bypasses the exhaust gas with respect to the second heater; a heating mode switching unit; and a control unit that, during the single supply of the oil fuel, executes the heating stop mode while the detected temperature is lower than the set temperature, and transitions to the heating operation mode when the detected temperature exceeds the set temperature.

Description

Technical Field

[0001] The present invention relates to a power generation system for a ship. Background Art

[0002] Marine power generation systems utilizing the organic Rankine cycle are known. For example, Patent Document 1 describes an energy recovery device that generates electricity by recovering the thermal energy of exhaust gas flowing through the exhaust gas passage 3 from a ship's engine EG fueled by C heavy oil toward the chimney ST. To prevent corrosion of the exhaust gas passage 3 and other areas downstream of the heater 16, this energy recovery device adjusts the amount of heat transferred from the exhaust gas to the working medium so that the exhaust gas temperature downstream of the heater 16 is above a set temperature. Specifically, the flow rate of the working medium passing through the heater 16 is regulated by adjusting the rotational speed of the pump 14 or by opening and closing a bypass valve 57 provided in a bypass passage 56 connected to the heater 16.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2019-132192 Summary of the Invention

[0004] In recent years, LNG carriers have increasingly been equipped with dual-fuel diesel engines that can run on both LNG and heavy fuel oil. When heat is recovered from the exhaust gas of internal combustion engines operating on heavy fuel oil containing a high sulfur content through heat exchangers (heaters for the working medium), sulfuric acid dew-point corrosion can occur not only in the exhaust gas path but also on the heater's heat transfer surfaces. If the heater were damaged by corrosion, there's also the risk of the working medium leaking into the ship.

[0005] Therefore, the object of the present invention is to suppress sulfuric acid dew point corrosion generated on the heat transfer surface of the heater when the exhaust gas of an internal combustion engine using an oil fuel containing a large amount of sulfur, such as heavy oil, is used as the heat source fluid in an organic Rankine cycle power generation system for ships that uses a heater to recover heat from two or more heat source fluids of different temperatures.

[0006] The ship power generation system of the present invention comprises: a circulation circuit that circulates a working medium with a lower boiling point than water; a circulation pump that circulates the working medium in the circulation circuit; a first heater that uses the compressed 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 the 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 rotates by the expansion energy of the working medium heated by the second heater; a cooler that cools the working medium after passing through the expander by a cooling fluid; a generator that is connected to the expander and is driven by the rotation of the expander; one or two bypass passages that bypass the working medium relative to the second heater and / or bypass the exhaust gas relative to the second heater; a heating mode switching unit that switches between a heating operation mode in which the working medium and the exhaust gas are simultaneously circulated through the second heater and a heating operation mode in which the working medium and the exhaust gas are simultaneously circulated through the second heater. a heating stop mode in which at least one side flows through the bypass passage; a temperature detection unit that detects the temperature of the working medium after flowing out of the first heater; a fuel type information acquisition unit that acquires information related to the fuel type supplied to the internal combustion engine; and a control unit that controls the operation of the power generation system, and when the power generation operation is started, under the condition that the fuel type information acquired by the fuel type information acquisition unit is a single supply of oil fuel, the control unit performs the following control: (i) after the circulation pump is started, while the detected temperature of the temperature detection unit is lower than the set temperature, controls the heating mode switching unit to execute the heating stop mode; and (ii) when the detected temperature of the temperature detection unit exceeds the set temperature, controls the heating mode switching unit to transfer from the heating stop mode to the heating action mode, and selects the set temperature based on the resistance of the metal material constituting the heat transfer surface of the second heater to sulfuric acid dew point corrosion.

[0007] According to the ship power generation system of the present invention, in an organic Rankine cycle power generation system for a ship that uses a heater to recover heat from two or more heat source fluids of different temperatures, when the exhaust gas of an internal combustion engine using an oil fuel containing a large amount of sulfur components such as heavy oil is used as the heat source fluid, sulfuric acid dew point corrosion generated on the heat transfer surface of the heater can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a diagram showing a marine power generation system according to an embodiment of the present invention.

[0009] Figure 2 It is a diagram showing a marine power generation system according to another embodiment of the present invention. DETAILED DESCRIPTION

[0010] Figure 1and Figure 2 1 is a diagram schematically showing a marine power generation system 1 according to an embodiment of the present invention. Figure 1 and Figure 2 The bypass passages are different. The bypass passages will be described later. The marine power generation system 1 of this embodiment utilizes waste heat from the ship 100 to generate electricity via an organic Rankine cycle (ORC). The pressurized air and exhaust gas generated by the operation of the internal combustion engine 60 serve as the heat source fluid. Furthermore, because the ORC power generation system utilizes two heat cycles—the heat source fluid system and the working medium system—to generate electricity, it is also referred to as a dual-cycle power generation system.

[0011] 1. The structure of the ship's main engine and auxiliary engine

[0012] The ship 100 of this embodiment is, for example, an LNG (liquefied natural gas) transport ship, and includes: an internal combustion engine 60, which obtains propulsion force for the hull; a fuel supply unit 62, which supplies fuels F1 and F2 to the internal combustion engine 60; a supercharger 64, which supplies pressurized air A2 to the internal combustion engine 60; and an exhaust turbine 66, which is connected to the supercharger 64 and is rotated by the exhaust gas E1 from the internal combustion engine 60.

[0013] Internal combustion engine 60 is a two-stroke diesel engine, also known as the main engine. Furthermore, internal combustion engine 60 can utilize a portion of the LNG carried as cargo, in addition to heavy fuel oil. Fuel supply unit 62 consists of a first fuel supply unit 62A equipped with an LNG tank and a vaporizer, and a second fuel supply unit 62B equipped with a heavy fuel oil tank and a preheater. First fuel supply unit 62A is connected to internal combustion engine 60 via a first fuel line LF1. Second fuel supply unit 62B is connected to internal combustion engine 60 via a second fuel line LF2. In the figure, LNG is represented by symbol F1, and heavy fuel oil by symbol F2.

[0014] The internal combustion engine 60 switches between three combustion modes depending on the navigation conditions of the vessel 100. Specifically, the first combustion mode is an LNG-only combustion mode, in which LNG is supplied solely as the gas fuel F1. The second combustion mode is an LNG / heavy oil mixed combustion mode, in which heavy oil is supplied as the oil fuel F2 and LNG is supplied as the gas fuel F1. The third combustion mode is a heavy oil-only combustion mode, in which heavy oil is supplied solely as the oil fuel F2.

[0015] The supercharger 64 draws in air A1 from outside the ship through the operation of the exhaust turbine 66 and compresses this air A1 to produce supercharged air A2. The intake port of the supercharger 64 is connected to an air filter (not shown) via an intake line LA3. The discharge port of the supercharger 64 is connected to the inlet of the high-temperature side flow path of the intercooler 70 via a first air supply line LA1.

[0016] The intercooler 70 is a heat exchanger that removes the heat of compression contained in the charge air A2 through heat exchange with cooling water W1. The outlet of the high-temperature side flow path of the intercooler 70 is connected to the inlet of the venturi mixer 72 via the second air supply line LA2. Furthermore, the low-temperature side flow path of the intercooler 70 is connected to a first cooling water line LW1, which allows the flow of cooling water W1, either seawater drawn from the sea during navigation or fresh water circulating through the central cooling equipment within the ship.

[0017] The Venturi mixer 72 uses the compressed air A2 as the driving fluid and utilizes the Venturi effect of the airflow to draw in the fuels F1 and F2, generating a mixed gas. This mixed gas is then supplied to the combustion chamber of the internal combustion engine 60. The exhaust chamber 74 utilizes the kinetic energy of the combustion gases continuously flowing out of the combustion chamber to improve the efficiency of the mixture. During operation of the internal combustion engine 60, the combustion gases flowing into the exhaust chamber 74 expand within the chamber and are discharged as exhaust gas E1. The outlet of the exhaust chamber 74 is connected to the inlet of the exhaust turbine 66 via the first exhaust gas line LE1.

[0018] The exhaust turbine 66 recovers a portion of the thermal energy of the exhaust gas E1 discharged from the exhaust chamber 74 to drive the supercharger 64. Within 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 impeller's rotating shaft drives the rotating shaft of the supercharger 64, which is connected via a coupling or the like. The outlet of the exhaust turbine 66 is connected to the chimney of the ship 100 via a second exhaust gas line LE2. The exhaust gas E2, after heat recovery in the second heater 12 (described later), is discharged overboard from the chimney.

[0019] The marine power generation system 1 of this embodiment may also include an exhaust gas economizer. An 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. Together with a steam-water separator (not shown), it constitutes an exhaust gas boiler. When an exhaust gas economizer is included, multiple steam pipes (heat transfer pipes) are arranged within the housing through which the exhaust gas E2 flows. One side of each steam pipe is connected to a water supply header (manifold) for distributing water, and the other side of each steam pipe is connected to a steam header (manifold) for collecting steam. The water supply header is connected to a water supply line that directs stored water within the steam-water separator as supply water. Furthermore, the steam header is connected to a steam line that returns the generated steam to the steam-water separator. Steam separated by the steam-water separator is used, for example, for preheating heavy fuel oil. The exhaust gas economizer housing outlet 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.

[0020] 2. Structure of marine power generation system

[0021] The marine 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 components are connected in this order in a loop through a circulation loop LC for the working medium R. This circulation loop LC is laid out over a large area within the ship in both horizontal and vertical directions and can therefore also be referred to as a pipeline for transporting the working medium R. The marine power generation system 1 also includes a control unit 30 for controlling the operation of the system.

[0022] The working medium R circulating in the circulation loop LC uses a high-molecular-weight organic compound with a lower boiling point than water. An example of the working medium R is a fluorocarbon-based medium such as HFC-245fa (chemical name: 1,1,1,3,3-pentafluoropropane, boiling point at 1 atmosphere: 15.3°C). Alternatively, a non-fluorocarbon-based medium such as isopentane (boiling point at 1 atmosphere: 27.8°C) or pentane (boiling point at 1 atmosphere: 36.1°C) may be used. Furthermore, to reduce friction and cool the expander 16, a lubricating oil with a higher boiling point than the high-molecular-weight organic compound may be mixed with the working medium R.

[0023] The circulation pump 22 is a device for circulating the working medium R containing lubricating oil in the circulation circuit LC and is driven by, for example, the inverter device 40. In this embodiment, the drive motor of the circulation pump 22 uses the variable voltage and variable frequency control function of the inverter device 40 to adjust the rotation speed.

[0024] The first heater 10 is a heater that receives the working medium R (medium liquid R) sent from the circulation pump 22. L ) heat exchanger. The high-temperature side flow path of the first heater 10 is connected midway through the first air supply line LA1. It uses the pressurized 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 regulating the flow rate of the working medium R supplied by the circulation pump 22. Specifically, the medium fluid flowing into the low-temperature side flow path of the first heater 10 is converted into saturated steam (wet steam) or superheated steam due to the heat input from the pressurized air A2.

[0025] The second heater 12 is a heater for heating the working medium R (medium gas R G) heat exchanger. The high-temperature side flow path of the second heater 12 is connected midway through the second exhaust gas line LE2. It 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 regulating the flow rate of the working medium R supplied by the circulation pump 22. Specifically, the saturated steam or superheated steam flowing into the low-temperature side flow path of the second heater 12 is further superheated by the heat input from the exhaust gas E2, becoming even higher-temperature superheated steam before flowing out of the outlet.

[0026] The expander 16 is used to convert the working medium R (medium gas R) in a superheated state into G ) into kinetic energy to drive the rotating shaft. The expander 16 comprises, for example, a twin-screw expansion mechanism. The rotating shaft of the screw rotor drives the rotating shaft of a generator 18, which is connected by a coupling or the like. Furthermore, the expander 16 may include another expansion mechanism such as a turbine, and may be either oil-fed or oil-free.

[0027] The cooler 20 is used to cool the working medium R (medium gas R) which has been heated by the expander 16 and has a lower temperature and increased volume. G ) condensation heat exchanger. The high-temperature side flow path of cooler 20 is connected midway through circulation loop LC, using cooling water W2 as the cooling fluid to cool the working medium R. A second cooling water pipeline LW2 is connected to the low-temperature side flow path of cooler 20. This second cooling water pipeline LW2 is used to flow in and out of seawater drawn from the sea during navigation or clean water circulating through the central cooling equipment within the ship as cooling water W2. Furthermore, a cooling water pump may be provided in the second cooling water pipeline LW2 as needed.

[0028] The generator 18 is coupled to the expander 16 and is driven by the expansion of the working medium R within the expansion space, which causes the screw rotor to rotate. 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 end of the screw rotor. This rotating shaft rotates as the screw rotor rotates, thereby generating electricity.

[0029] A temperature detection unit 44 is provided near the outlet of the low-temperature side flow path of the first heater 10. The temperature detection unit 44 is a sensor that detects the temperature of the working medium R immediately after flowing out of the first heater 10. Detection signals from the temperature detection unit 44 are input to the control unit 30 described below.

[0030] The control unit 30 includes a circulation flow rate control unit 31 and a fuel type information acquisition unit 32. The circulation flow rate control unit 31 controls the rotation speed of the circulation pump 22 via 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 regarding the load factor of the internal combustion engine 60. The fuel type information acquisition unit 32 acquires information regarding the type of fuel supplied to the internal combustion engine 60. Specifically, the fuel type information acquisition unit 32 uses the combustion mode information of the internal combustion engine 60 (LNG-only combustion mode, LNG / heavy oil mixed combustion mode, heavy oil-only combustion mode) to determine the fuel type.

[0031] Here, the structure of heat recovery and power generation will be described. The working medium R is pressurized by driving the circulation pump 22 and is transferred to the heat exchanger in the circulation circuit LC. Figure 1 The working medium R flows in the direction of the arrow shown. The working medium R is heated in the first heater 10 and the second heater 12 by recovering heat from the heat source fluid (charged air A2, exhaust gas E2) and becomes superheated steam. The working medium R that becomes high-temperature / high-pressure superheated steam G The screw rotor of the expander 16 rotates to drive the generator 18. The working medium R becomes low-temperature / low-pressure expanded steam after passing through the screw rotor. G The working medium R that becomes condensed liquid is cooled by the cooler 20. L The heat is again fed to the first heater 10 and the second heater 12 by the circulation pump 22. As described above, the working medium R repeats its state change while circulating in the circulation circuit LC, and thus thermal energy can be converted into electrical energy.

[0032] 3. Bypass switching control of working medium and exhaust gas

[0033] The marine power generation system 1 of this embodiment includes one or two bypass passages LB for bypassing the working medium R and / or the exhaust gas E2 relative to the second heater 12. The bypass passages LB include a first bypass passage LB1 and a second bypass passage LB2. The first bypass passage LB1 bypasses the working medium R. The second bypass passage LB2 bypasses the exhaust gas E2. Figure 1 The marine power generation system 1 is shown including only the first bypass LB1 . Figure 2 The ship power generation system 1 is shown as including only the second bypass channel LB2 . Note that both the first bypass channel LB1 and the second bypass channel LB2 may be provided in one ship power generation system 1 .

[0034] The marine power generation system 1 also includes a heating mode switching unit, 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 directed to 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 directed to the bypass path LB.

[0035] Figure 1 The first bypass passage LB1 shown branches off from the circulation loop LC on the downstream side of the temperature detection unit 44 and the upstream side of the second heater 12. A two-way valve V1 constituting a heating mode switching unit is provided on the downstream side of the branch point and the upstream side of the second heater 12. The first bypass passage LB1 merges with the circulation loop LC on the downstream side of the second heater 12 and the upstream side of the oil separator 14. A two-way valve V2 constituting a heating mode switching unit is provided in the first bypass passage LB1. For example, a ball-type electric valve can be used for the two-way valves V1 and V2. In addition, a three-way valve can be provided at the branch point of the first bypass passage LB1 instead of the two-way valves V1 and V2.

[0036] on the other hand, Figure 2 The second bypass passage LB2 shown branches off from the second exhaust gas line LE2 upstream of the second heater 12. A two-way valve V3, which constitutes a heating mode switching unit, is located 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. A two-way valve V4, which constitutes a heating mode switching unit, is located in the second bypass passage LB2. For example, butterfly damping valves can be used for the two-way valves V3 and V4. Alternatively, a three-way valve can be provided at the branching point of the second bypass passage LB2 in place of the two-way valves V3 and V4.

[0037] The control unit 30 refers to the information regarding 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 the heavy oil-only combustion mode), the control unit 30 executes control action A, described below. If the information indicates that both oil fuel and gas fuel are being supplied (i.e., the internal combustion engine 60 is operating in the LNG / heavy oil mixed combustion mode), the control unit 30 executes control action B, described below. Furthermore, if the information indicates that only gas fuel is being supplied (i.e., the internal combustion engine 60 is operating in the LNG-only combustion mode), the control unit 30 executes control action C, described below. By selecting control actions A through C, the 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.

[0038] 3.1 Control Action A

[0039] In this control action A, the control unit 30 (i) controls the heating mode switching unit to execute the heating stop mode while the temperature detected by the temperature detection unit 44 is lower than the set temperature after the circulation pump 22 is started, and (ii) controls the heating mode switching unit to switch from the heating stop mode to the heating operation mode when the temperature detected by the temperature detection unit 44 exceeds the set temperature.

[0040] Specifically, in the initial cold state, the control unit 30 opens the two-way valves V2 and V4, which serve as bypass valves, closes the two-way valves V1 and V3, which serve as inlet shutoff valves, and stops the circulation pump 22, thereby executing the heating stop mode. As will be described later, the heating stop mode is switched to when power generation ends, so this mode continues in the initial state.

[0041] With the start of power generation operation, the control unit 30 starts the circulation pump 22 and increases its speed to a specified value. When the set temperature is reached, the control unit 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 heating mode. In heating mode, the working medium R and exhaust gas E2 flow through the second heater 12. As heat exchange proceeds, the working medium R is heated and the exhaust gas E2 is cooled.

[0042] Here, the set temperature is selected based on the resistance of the metal material constituting the heat transfer surface of the second heater 12 to sulfuric acid dew-point corrosion. Specifically, if the metal material constituting the heat transfer surface of the second heater 12 has relatively low corrosion resistance to sulfuric acid, the set temperature is set to a higher first set temperature (e.g., 100°C). If the corrosion resistance is relatively high, the set temperature is set to a lower second set temperature (e.g., 80°C).

[0043] Furthermore, when terminating the power generation operation, the control unit 30 (i) controls the heating mode switching unit to switch from the heating operation mode to the heating stop mode, and (ii) stops the circulation pump 22 after switching to the heating stop mode.

[0044] Specifically, upon completion of power generation operation, the control unit 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 circulation pump 22 to zero speed before stopping it, thereby transitioning to the heating stop mode. In the heating stop mode, the working medium R or exhaust gas E2 bypasses the second heater 12, preventing the exhaust gas E2 from being cooled.

[0045] 3.2 Control Action B

[0046] In this control action B, the control unit 30 changes the set temperature to a lower correction temperature. This correction temperature can be set to a value approximately 10°C to 20°C lower than the first and second set temperatures described above. Control action B is identical to control action A, except for the different set temperatures.

[0047] 3.3 Control Action C

[0048] In this control action C, the control unit 30 controls the heating mode switching unit so that the heating operation mode is executed regardless of the temperature detected by the temperature detection unit 44. Specifically, the control unit 30 always opens the inlet shutoff valves (two-way valve V1 and two-way valve V3) and always closes the bypass valves (two-way valve V2 and two-way valve V4).

[0049] According to the marine power generation system of the embodiment described above, the following effects are achieved.

[0050] (1) A marine power generation system 1 comprises: a circulation circuit LC for circulating a working medium R having a lower boiling point than water; a circulation pump 22 for circulating the working medium R in the circulation circuit LC; a first heater 10 for heating the working medium from the circulation pump 22 using the pressurized air from the supercharger 64 attached to the internal combustion engine 60 as a heat source fluid; a second heater 12 for heating the working medium R heated by the first heater 10 using the exhaust gas from the internal combustion engine 60 as a heat source fluid; an expander 16 for heating the working medium R heated by the second heater 16; The heater 12 rotates by utilizing the expansion energy of the working medium R heated by the heater 12; a cooler 20 that cools the working medium R after passing through the expander 16 with a cooling fluid; a generator 18 that is connected to the expander 16 and is driven by the rotation of the expander 16; one or two bypass paths LB that bypass the working medium R relative to the second heater 12 and / or bypass the exhaust gas E2 relative to the above-mentioned second heater 12; a heating mode switching unit (two-way valves V1 to V4) that switches so that the working medium R and the exhaust gas E2 are simultaneously fed to the second heater 12. 12 flows, and a heating stop mode in which the working medium R and the exhaust gas E2 are caused to flow to at least one of the bypass passage LB; a temperature detection unit 44 that detects the temperature of the working medium R after flowing out of the first heater 10; a fuel type information acquisition unit 32 that acquires information about the type of fuel supplied to the internal combustion engine 60; and a control unit 30 that controls the operation of the power generation system 1, wherein the control unit 30, when starting the power generation operation, controls the heating mode switching unit (two-way valves V1 to V4) to execute the heating stop mode while the temperature detected by the temperature detection unit 44 is lower than a set temperature after the circulation pump 22 is started, and (ii) controls the heating mode switching unit (two-way valves V1 to V4) to switch from the heating stop mode to the heating operation mode when the temperature detected by the temperature detection unit 44 exceeds a set temperature, wherein the set temperature is selected based on the resistance of the metal material constituting the heat transfer surface of the second heater 12 to sulfuric acid dew point corrosion.

[0051] When the internal combustion engine 60 is operating in an oil-only combustion mode (for example, burning heavy oil containing sulfur), after the circulation pump 22 is activated to begin power generation, while the detected temperature of the working medium R flowing out of the first heater 10 is below a set temperature, the heating stop mode is executed, causing either the working medium R or the exhaust gas E2 to flow through the bypass path LB. After activation, the circulation pump 22 is accelerated at a constant acceleration rate, for example, via the flow control unit 40 (inverter device), until it reaches the rated speed. During this period, the working medium R is preheated in the first heater 10. If preheating of the working medium R progresses and the detected temperature of the working medium R flowing out of the first heater 10 exceeds the set temperature, the system switches to a heating operation mode, causing both the working medium R and the exhaust gas E2 to flow through the second heater 12.

[0052] During bypass operation at a first set temperature (e.g., 100°C), which is used when the metal material constituting the heat transfer surface of the second heater 12 has relatively low corrosion resistance to sulfuric acid, condensation on the heat transfer surface of the second heater 12 is avoided, effectively preventing sulfuric acid dew-point corrosion. Furthermore, during bypass operation at a second set temperature (e.g., 80°C), which is used when the metal material constituting the heat transfer surface of the second heater 12 has relatively high corrosion resistance to sulfuric acid, condensation may occur on the heat transfer surface of the second heater 12. However, due to the high corrosion resistance of the metal material, sulfuric acid dew-point corrosion can be avoided.

[0053] (2) In the marine power generation system 1 of the above-mentioned (1), when the power generation operation is terminated, the control unit 30 (i) controls the heating mode switching unit (two-way valves V1 to V4) so ​​as to switch from the heating operation mode to the heating stop mode, and (ii) stops the circulation pump 22 after switching to the heating stop mode.

[0054] When the power generation operation is terminated, the heating operation mode is switched to the heating stop mode before the circulation pump 22 is decelerated and stopped, and either the working medium R or the exhaust gas E2 is caused to flow through the bypass path LB. Thereafter, the circulation pump 22 is gradually decelerated and finally stopped.

[0055] If the circulation pump 22 is decelerated toward a stop in the heating mode, the working medium R, whose flow rate has decreased, will become overheated in the second heater 12, potentially damaging the expander 16 due to thermal fatigue. By operating the circulation pump 22 to stop after bypassing either the working medium R or the exhaust gas E2, overheating of the working medium R can be prevented, thereby avoiding thermal fatigue of the expander 16.

[0056] (3) In the marine power generation system 1 of (1) or (2) above, when starting power generation operation, the control unit 30 changes the set temperature to a lower correction temperature under the condition that the fuel type information acquired by the fuel type information acquisition unit 32 indicates that oil fuel and gas fuel are supplied simultaneously.

[0057] When the internal combustion engine 60 is operating in the oil / gas mixed combustion mode (combusting sulfur-containing heavy oil or sulfur-free LNG, for example), the concentration of sulfur oxides (SO₃) in the exhaust gas is lower than when operating in the oil-only combustion mode. Therefore, the set temperature is changed to a lower correction temperature. While lowering the set temperature may cause condensation on the heat transfer surface of the second heater 12, this reduces the amount of sulfuric acid deposited, thereby preventing sulfuric acid dew point corrosion.

[0058] (4) In the marine power generation system 1 of (1) to (3) above, when starting the power generation operation, the control unit 30 controls the heating mode switching unit (two-way valves V1 to V4) to execute the heating operation mode regardless of the temperature detected by the temperature detection unit 44, under the condition that the fuel type information obtained by the fuel type information acquisition unit 32 is a single supply of gas fuel.

[0059] When the internal combustion engine 60 is operating in a gas-only combustion mode (such as combustion of sulfur-free LNG), no sulfur oxides (SO3) are generated, and therefore, no bypass operation is performed regardless of the detected temperature. After the circulation pump 22 is activated, the working medium R can be preheated using both the first heater 10 and the second heater 12, enabling power generation to commence quickly.

[0060] [Contribution to the Sustainable Development Goals (SDGs) led by the United Nations]

[0061] The marine power generation system according to the present disclosure can contribute to the achievement of Goal 7 of the SDGs (Sustainable Development Goals), namely, "Making all energy clean" and Goal 13, "Taking concrete measures to combat climate change."

[0062] Explanation of symbols

[0063] 1 Marine power generation system

[0064] 10First heater

[0065] 12 Second heater

[0066] 16 expanders

[0067] 18 generators

[0068] 20 coolers

[0069] 22 circulation pump

[0070] 30 control units

[0071] 32 Fuel type information acquisition unit

[0072] 44 temperature detection unit

[0073] 60 internal combustion engines

[0074] 64 supercharger

[0075] A2 pressurized air

[0076] E2 exhaust

[0077] RWorking medium

[0078] LC circulation loop

[0079] LB bypass

[0080] LB1 first bypass

[0081] LB2 second bypass

[0082] V1, V2, V3, V4 two-way valves (heating mode switching units).

Claims

1. A power generation system for a ship, characterized in that: have: a circulation loop that circulates a working medium having a lower boiling point than water; a circulation pump for circulating the working medium within the circulation loop; a first heater, which uses the pressurized 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, which uses the 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 rotates by expansion energy of the working medium heated by the second heater; a cooler for cooling the working medium after passing through the expander using a cooling fluid; a generator connected to the expander and driven by the rotation of the expander; One or two bypass passages for bypassing the working medium relative to the second heater and / or for bypassing the exhaust gas relative to the second heater; a heating mode switching unit 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 unit configured to detect a temperature of the working medium after flowing out of the first heater; a fuel type information acquisition unit that acquires information on the type of fuel supplied to the internal combustion engine; as well as a control unit that controls the operation of the power generation system, When starting the power generation operation, the control unit performs the following control under the condition that the fuel type information acquired by the fuel type information acquisition unit indicates that the oil fuel is supplied alone: (i) after the circulation pump is started, while the temperature detected by the temperature detection unit is lower than a set temperature, controlling the heating mode switching unit to execute the heating stop mode; and (ii) when the temperature detected by the temperature detection unit exceeds the set temperature, controlling the heating mode switching unit to switch from the heating stop mode to the heating operation mode, The set temperature is selected based on the resistance of the metal material constituting the heat transfer surface of the second heater to sulfuric acid dew point corrosion.

2. The marine power generation system according to claim 1, wherein: When the power generation operation is terminated, the control unit performs the following control: (i) controlling the heating mode switching unit to shift from the heating operation mode to the heating stop mode; and (ii) After transitioning to the heating stop mode, the circulation pump is stopped.

3. The marine power generation system according to claim 1 or 2, characterized in that: When starting the power generation operation, the control unit controls to change the set temperature to a lower correction temperature under the condition that the fuel type information acquired by the fuel type information acquisition unit indicates simultaneous supply of oil fuel and gas fuel.

4. The marine power generation system according to claim 1 or 2, characterized in that: When starting the power generation operation, the control unit performs the following control: under the condition that the fuel type information obtained by the fuel type information acquisition unit is a single supply of gas fuel, the heating mode switching unit is controlled in a manner that performs the heating action mode regardless of the detection temperature of the temperature detection unit.

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