Exhaust gas waste heat recovery system for ships

Abstract

A waste heat recovery system for exhaust gas for a ship is disclosed. The waste heat recovery system for exhaust gas for a ship of the present invention includes a heat medium circulation line provided on a ship and through which a working fluid circulates, a carburetor provided in the heat medium circulation line and vaporizing the working fluid by heat exchange with exhaust gas discharged from an engine of the ship, and an expansion turbine provided in the heat medium circulation line and expanding the working fluid to generate shaft power, wherein a liquefied gas with a low flash point is supplied to the engine as fuel, and the working fluid circulates through the heat medium circulation line and undergoes a phase change from liquid to gas using the exhaust gas as a heat source.

Description

[Technical field]

[0001] The present invention relates to a waste heat recovery system for exhaust gas for a ship, and more particularly to a waste heat recovery system for exhaust gas for a ship, which uses exhaust gas discharged from an engine that uses a low flash point liquefied gas as fuel as a heat source, and generates shaft power by changing the phase of a working fluid circulating in a closed loop heat medium circulation line. [Background technology]

[0002] Conventionally, ship propulsion engines are provided with fuel supply systems that use relatively inexpensive heavy oil such as bunker C oil. When fuel is burned, such fuel supply systems that use heavy oil emit large amounts of exhaust gases that contain greenhouse gases such as carbon dioxide, sulfur oxides, nitrogen oxides, and other substances whose emissions are regulated by the International Maritime Organization (IMO).

[0003] As global warming becomes more serious, efforts to reduce greenhouse gas emissions are being made worldwide. The Kyoto Protocol, which was adopted in 1997 and requires developed countries to reduce their greenhouse gas emissions, will expire in 2020. As a result, the 195 signatory countries to the Paris Climate Change Accord, which was adopted at the 21st Conference of the Parties to the United Nations Framework Convention on Climate Change held in Paris, France in December 2015 and came into force in November 2016, are making various efforts to reduce greenhouse gas emissions. Coupled with the strengthening of international environmental regulations, countries are becoming more concerned about the emissions of greenhouse gases and air pollutants, and environmentally friendly fuel technologies are being actively developed for ships.

[0004] Liquefied gas is known as an environmentally friendly fuel because it emits less air pollutants than heavy oil and marine diesel oil (MDO) because air pollutants can be removed or reduced during the liquefaction process. Liquefied natural gas (LNG), a representative liquefied gas, is a colorless and transparent liquid obtained by liquefying natural gas, which is mainly composed of methane, by cooling it to about -163°C. Liquefied natural gas has excellent storage and transportation efficiency because its volume is reduced to about 1 / 600 compared to natural gas in gaseous state. For these reasons, liquefied gas has been actively developed and used as a fuel for ships. Another representative liquefied gas, LPG (Liquefied Petroleum Gas), is made by liquefying petroleum gas, which is mainly composed of low-boiling point hydrocarbons such as propane and butane in crude oil, and is easier to store than LNG, which must be liquefied at extremely low temperatures. In addition, the specific energy and energy density of LPG are comparable to those of HFO (heavy fuel oil), and it has lower emissions of SOx, NOx, and CO compared to HFO. 2 LPG has the advantage of being able to reduce emissions of pollutants such as PM. For these reasons, LPG has been actively developed and used as a marine fuel.

[0005] In recent years, research and development into the use of ammonia as a marine fuel has been actively carried out in order to achieve complete decarbonization. Ammonia (NH 3 Ammonia is a substance in which one nitrogen atom is bonded to three hydrogen atoms, and because it forms strong hydrogen bonds between molecules, it is easily liquefied, with a boiling point of -33.34°C and a melting point of -77.73°C under standard pressure. Ammonia is particularly easy to store and transport, and can be easily mass-produced using the Haber-Bosch process, making it more economical than other carbon-neutral fuels. Summary of the Invention [Problem to be solved by the invention]

[0006] In order to supply fuel to an engine, it is necessary to heat liquefied gas such as fuel oil or LNG according to the fuel supply conditions of the engine. In a ship that uses HFO as fuel, the waste heat of the exhaust gas discharged from the engine is recovered to generate steam, the generated steam is used to heat fuel oil, and the heated fuel oil is supplied to the engine. Similarly, in a ship that uses LNG as fuel, the waste heat of the exhaust gas discharged from the engine is recovered to generate steam, the generated steam is used to vaporize LNG, and the vaporized natural gas is supplied to the engine. In this way, the thermal efficiency of the ship can be improved by recovering the waste heat of the exhaust gas and using it to heat the fuel. However, fuel oil contains sulfur components, and when exhaust gas waste heat is recovered, sulfur dioxide (SO ) contained in the exhaust gas is mixed with sulfur dioxide (SO ) contained in the exhaust gas. 2 ) is converted to sulfuric acid (H 2 SO 4 There is a risk of sulfuric acid dew point corrosion, which is a corrosion-causing phenomenon caused by sulfuric acid condensing on metal surfaces as sulfuric acid dew point corrosion. For this reason, in systems equipped with a heat exchanger that uses the waste heat from the exhaust gas, if the metal surface temperature of the system falls below the dew point of sulfuric acid, corrosion is likely to occur on the metal surface. To avoid this, waste heat is only recovered from exhaust gas with a temperature of 150°C or higher.

[0007] Among low flashpoint fuels, LPG and ammonia have relatively high boiling points, so they require very little heat to heat them up to the supply temperature required by the engine when they are supplied, and there is almost no risk of icing of the heater for the fuel supply. Therefore, LPG and ammonia can be heated by engine cooling water or the like without using waste heat from exhaust gas.

[0008] In addition, because these fuels do not contain sulfur components, low-temperature corrosion is unlikely to occur even when waste heat is recovered from exhaust gases with temperatures of 150°C or less.

[0009] The present invention focuses on these points and proposes a method for recovering energy that can be used on board a ship from the waste heat of the exhaust gas discharged from the engine when liquefied gas is supplied to the engine as fuel, particularly when liquefied gas with a low flash point such as LPG or ammonia is supplied to the engine as fuel. [Means for solving the problem]

[0010] In order to solve the above problem, an embodiment of the present invention provides a waste heat recovery system for exhaust gas for a ship, comprising: a heat medium circulation line provided in a ship and through which a working fluid circulates; a carburetor provided in the heat medium circulation line and configured to vaporize the working fluid by heat exchange with exhaust gas discharged from an engine of the ship; and an expansion turbine provided in the heat medium circulation line and configured to expand the working fluid to generate shaft power, wherein a liquefied gas having a low flash point is supplied to the engine as fuel, and the working fluid circulates through the heat medium circulation line and undergoes a phase change from liquid to gas using the exhaust gas as a heat source.

[0011] Preferably, the heat medium circulation line is provided with a condenser which cools and condenses the working fluid cooled by expansion in the expansion turbine, and a supply pump which pressurizes the working fluid condensed in the condenser and sends it to the evaporator.

[0012] Preferably, the compressor further includes a compressor that compresses air by shaft power generated by the expansion turbine, and an air supply line that supplies air to the compressor.

[0013] Preferably, the air compressed by the compressor is supplied to a consumer within the ship via the air supply line, and the consumer within the ship injects air onto the outside of the bottom of the ship while in operation to reduce frictional resistance with seawater.

[0014] Preferably, the engine further comprises a turbocharger which supercharges the scavenging air to be supplied to the engine, a scavenging air supply line which cools the scavenging air compressed by the turbocharger and supplies the cooled scavenging air to the engine, a branch line which branches off from the scavenging air supply line and is connected to the air supply line downstream of the compressor, and a branch valve which is provided in the branch line.

[0015] Preferably, when the pressure of the scavenging air compressed by the turbocharger is higher than the discharge pressure of the compressor and therefore the pressure of the scavenging air needs to be reduced, an opening degree of the branch valve is adjusted so that a portion of the scavenging air compressed by the turbocharger is supplied to a consumer within the ship.

[0016] Preferably, the working fluid is an organic refrigerant or an aqueous ammonia solution.

[0017] Preferably, the low flash point liquefied gas includes at least one of LPG and ammonia.

[0018] In order to solve the above problem, an embodiment of the present invention provides a waste heat recovery system for exhaust gas for a ship, comprising: a heat medium circulation line provided in a ship and through which a working fluid circulates; a carburetor provided in the heat medium circulation line and configured to heat the working fluid by heat exchange with exhaust gas discharged from an engine of the ship; a gas-liquid separator provided in the heat medium circulation line and configured to separate the working fluid heated by the carburetor into gas and liquid; an expansion turbine configured to expand the gaseous working fluid separated in the gas-liquid separator to generate shaft power; a condenser configured to cool and condense the working fluid cooled by expansion in the expansion turbine; a supply pump provided in the heat medium circulation line and configured to pressurize the working fluid condensed in the condenser; and a liquid line configured to supply the liquid working fluid separated in the gas-liquid separator to a side of the heat medium circulation line downstream of the expansion turbine, wherein a liquefied gas having a low flash point is supplied as fuel to the engine.

[0019] Preferably, the system further includes a recuperator provided in the heat medium circulation line for heating the working fluid pressurized by the supply pump and supplying the working fluid to the evaporator, and the working fluid circulates through the heat medium circulation line and undergoes a phase change from liquid to gas using the exhaust gas as a heat source.

[0020] Preferably, the recuperator is provided downstream of a junction of the heat medium circulation line with the liquid line, and the recuperator heats the working fluid pressurized by the supply pump by heat exchange with the working fluid supplied to the condenser.

[0021] Preferably, the working fluid is a fluid having a boiling point lower than that of water.

[0022] Preferably, in the recuperator, the working fluid pressurized by the supply pump is heated by heat exchange with the working fluid in a liquid state that has been separated in the gas-liquid separator and flows through the liquid line.

[0023] Preferably, the working fluid is an aqueous ammonia solution.

[0024] Preferably, the engine is an engine that uses a low flash point liquefied gas as fuel, and the low flash point liquefied gas includes at least one of LPG and ammonia.

[0025] Preferably, air is compressed in a compressor using shaft power generated by the expansion turbine, and the air compressed by the compressor is supplied to a consumer within the ship, and the consumer within the ship is an air lubrication system that injects air onto the outside of the bottom of the ship while it is in operation to reduce frictional resistance with seawater.

[0026] In order to solve the above problem, an embodiment of the present invention includes a heat medium circulation line provided in a ship and through which a working fluid circulates; a carburetor provided in the heat medium circulation line and configured to heat the working fluid by heat exchange with exhaust gas discharged from an engine of the ship; a gas-liquid separator provided in the heat medium circulation line and configured to separate the working fluid heated by the carburetor into gas and liquid; an expansion turbine configured to expand the gaseous working fluid separated by the gas-liquid separator to generate shaft power; and a condensation heat exchanger configured to cool and condense the working fluid cooled by expansion in the expansion turbine. The present invention provides a waste heat recovery system for exhaust gas for a ship, comprising: a supply pump provided in a heat medium circulation line for pressurizing the working fluid condensed in the condensing heat exchanger and sending it to the evaporator; and a first cooling water supply line for supplying cooling water to the condensing heat exchanger for cooling the working fluid, wherein a liquefied gas with a low flash point is supplied to the engine as fuel, and heat is exchanged in the condensing heat exchanger among three flows: the working fluid cooled by expansion in the expansion turbine, the working fluid pressurized by the supply pump, and the cooling water in the first cooling water supply line.

[0027] Preferably, the system further includes a suction pot for additionally cooling the working fluid condensed in the condensation heat exchanger before supplying it to the supply pump, and a second cooling water supply line for supplying cooling water to the suction pot for cooling the working fluid, and by supplying the working fluid additionally cooled in the suction pot to the supply pump, cavitation at the suction section of the supply pump can be prevented.

[0028] Preferably, the system further includes a liquid line for supplying the liquid working fluid separated in the gas-liquid separator to a side of the heat medium circulation line downstream of the expansion turbine, and the liquid working fluid separated in the gas-liquid separator is supplied to the condensing heat exchanger via the liquid line together with the working fluid discharged from the expansion turbine.

[0029] Preferably, the working fluid is a fluid that circulates through the heat medium circulation line, changes phase from liquid to gas using the exhaust gas as a heat source, and has a boiling point lower than that of water.

[0030] Preferably, the system further includes a recuperator that is provided in the heat medium circulation line, heats the working fluid that has been pressurized by the supply pump and then heat-exchanged in the condensing heat exchanger, and supplies the working fluid to the evaporator.

[0031] Preferably, in the recuperator, the working fluid that has been pressurized by the supply pump and then heat exchanged in the condensing heat exchanger is heated by heat exchange with the liquid working fluid that has been separated in the gas-liquid separator and flows through the liquid line.

[0032] Preferably, the working fluid is an aqueous ammonia solution.

[0033] Preferably, the low flash point liquefied gas includes at least one of LPG and ammonia.

[0034] Preferably, air is compressed in a compressor using shaft power generated by the expansion turbine, and the air compressed by the compressor is supplied to a consumer within the ship, and the consumer within the ship is an air lubrication system that injects air onto the outside of the bottom of the ship while it is in operation to reduce frictional resistance with seawater.

[0035] In order to solve the above problem, in an embodiment of the present invention, there is provided a heat medium circulation line provided in a ship and through which a working fluid circulates, an evaporation section provided in the heat medium circulation line and performing heat exchange between the working fluid and exhaust gas discharged from an engine of the ship that uses a liquefied gas having a low flash point as fuel, an exhaust gas supply line that supplies exhaust gas to be heat exchanged with the working fluid to the evaporation section, a gas-liquid separator provided in the heat medium circulation line and performing gas-liquid separation of the working fluid heated in the evaporation section, an expansion turbine that expands the working fluid in a gaseous state separated in the gas-liquid separator to generate shaft power, and a cooling system that cools the working fluid cooled by expansion in the expansion turbine. a condensation heat exchanger for condensing a working fluid condensed in the condensation heat exchanger, and a supply pump provided in the heat medium circulation line for pressurizing the working fluid condensed in the condensation heat exchanger and sending it to the vaporization section, the vaporization section including a vaporizer and a superheater provided in this order in a flow direction of the working fluid supplied from the supply pump, the exhaust gas supplied from the exhaust gas supply line being supplied in the order of the superheater and the vaporizer, the working fluid that has exchanged heat with the exhaust gas in the vaporizer being separated into gas and liquid in the gas-liquid separator, the separated working fluid in a gaseous state being additionally heated in the superheater and supplied to the expansion turbine.

[0036] Preferably, the system further includes a cooling water supply line for supplying cooling water to the condensation heat exchanger for cooling the working fluid, and in the condensation heat exchanger, heat is exchanged between three flows: the working fluid cooled by expansion in the expansion turbine, the working fluid pressurized by the supply pump, and the cooling water in the cooling water supply line.

[0037] Preferably, the system further includes a liquid line for supplying the liquid working fluid separated in the gas-liquid separator to a portion of the heat medium circulation line downstream of the expansion turbine, and the liquid working fluid separated in the gas-liquid separator is supplied to the condensing heat exchanger via the liquid line together with the working fluid discharged from the expansion turbine.

[0038] Preferably, the working fluid is a fluid that circulates through the heat medium circulation line, changes phase from liquid to gas using exhaust gas discharged from the engine as a heat source, and has a boiling point lower than that of water.

[0039] Preferably, the system further includes a recuperator that is provided in the heat medium circulation line, heats the working fluid that has been pressurized by the supply pump and has been heat exchanged in the condensing heat exchanger, and supplies the heated working fluid to the evaporator.

[0040] Preferably, in the recuperator, the working fluid that has been pressurized by the supply pump and then heat exchanged in the condensing heat exchanger is heated by heat exchange with the liquid working fluid that has been separated in the gas-liquid separator and flows through the liquid line.

[0041] Preferably, the vaporization unit further includes an exhaust heat heater for exchanging heat between the exhaust gas discharged from the vaporizer and the working fluid pressurized by the supply pump and then heat exchanged in the condensing heat exchanger, The heating apparatus further includes a branch line that branches the working fluid that has been pressurized by the supply pump and then heat exchanged in the condensing heat exchanger and supplies it to the exhaust heat heater, and supplies the working fluid discharged from the exhaust heat heater to a side of the heat medium circulation line downstream of the recuperator.

[0042] Preferably, the working fluid is an aqueous ammonia solution.

[0043] Preferably, the low flash point liquefied gas includes at least one of LPG and ammonia.

[0044] Preferably, air is compressed in a compressor using shaft power generated by the expansion turbine, and the air compressed by the compressor is supplied to a consumer within the ship, and the consumer within the ship is an air lubrication system that injects air onto the outside of the bottom of the ship while it is in operation to reduce frictional resistance with seawater.

[0045] In order to solve the above problems, in an embodiment of the present invention, a heat medium circulation line provided in a ship and through which a working fluid circulates; an evaporation unit provided in the heat medium circulation line and performing heat exchange between the working fluid and exhaust gas discharged from an engine of the ship that uses a liquefied gas having a low flash point as fuel; a gas-liquid separator provided in the heat medium circulation line and performing gas-liquid separation of the working fluid heated in the evaporation unit; an expansion turbine that expands the gaseous working fluid separated in the gas-liquid separator to generate shaft power; a condenser that cools and condenses the working fluid cooled by expansion in the expansion turbine; and a cooling unit provided in the heat medium circulation line and configured to cool the working fluid condensed in the condenser. a supply pump for pressurizing a working fluid, a first recuperator for heating a portion of the working fluid pressurized by the supply pump and supplying it to the evaporation section; and a second recuperator arranged in parallel with the first recuperator for heating another portion of the working fluid pressurized by the supply pump and supplying it to the evaporation section, wherein the first recuperator exchanges heat between the working fluid pressurized by the supply pump and the working fluid that is cooled by expansion in the expansion turbine and then supplied to the condenser, and the second recuperator heats the working fluid pressurized by the supply pump with waste heat supplied from a compression device or a cooling device on the ship.

[0046] Preferably, the vaporization unit includes a vaporizer and a superheater arranged in the same order as the flow direction of the working fluid supplied from a supply pump, and an exhaust gas supply line for supplying exhaust gas to the vaporizer and the superheater for heat exchange with the working fluid, and the exhaust gas is supplied from the exhaust gas supply line to the superheater and then to the vaporizer, the working fluid that has exchanged heat with the exhaust gas in the vaporizer is separated into gas and liquid in the gas-liquid separator, and the separated gaseous working fluid is further heated in the superheater and supplied to the expansion turbine.

[0047] Preferably, the system further includes a cooling water supply line for supplying cooling water to the condenser for cooling the working fluid, and a liquid line for supplying the liquid working fluid separated in the gas-liquid separator to a portion of the heat medium circulation line downstream of the expansion turbine, and the liquid working fluid separated in the gas-liquid separator is supplied from the liquid line to the first recuperator together with the working fluid discharged from the expansion turbine, and is then supplied to the condenser.

[0048] Preferably, the steam turbine further includes a compressor that compresses air using shaft power generated by the expansion turbine, and an air supply line that supplies air to the compressor, and the air compressed by the compressor is supplied to the second recuperator through the air supply line, and is supplied to a consumer within the ship after heat exchange with another part of the working fluid pressurized by the supply pump.

[0049] Preferably, the system further includes a third recuperator that is provided in the heat medium circulation line and that heats the working fluid that has been pressurized by the supply pump and then heat-exchanged in the first or second recuperator and supplies the working fluid to the evaporator.

[0050] Preferably, in the third recuperator, the working fluid that has been pressurized by the supply pump and then heat exchanged in the first or second recuperator is heated by heat exchange with the liquid working fluid that has been separated in the gas-liquid separator and flows through a liquid line.

[0051] Preferably, the vaporization section further includes an exhaust heat heater that exchanges heat between the exhaust gas discharged from the vaporizer and a working fluid that is pressurized by the supply pump, heat exchanged in the first recuperator, and then branched, and further includes a branch line that supplies the working fluid that has been heat exchanged in the exhaust heat heater to a side of the heat medium circulation line downstream of the third recuperator.

[0052] Preferably, the steam turbine further includes a compressor which compresses air using shaft power generated by the expansion turbine, and an air supply line which supplies air to the compressor, and the air compressed by the compressor is supplied to the second recuperator via the air supply line, and is supplied to a consumer within the ship after heat exchange with another part of the working fluid pressurized by the supply pump.

[0053] Preferably, the working fluid is an aqueous ammonia solution.

[0054] Preferably, the low flash point liquefied gas comprises at least one of LPG and ammonia. Effect of the Invention

[0055] The exhaust gas waste heat recovery system of the present invention can improve the energy efficiency of a ship by efficiently recovering the waste heat of exhaust gas emitted from an engine that uses a low-flash point liquefied gas as fuel.

[0056] The exhaust gas waste heat recovery system of the present invention converts the waste heat of the exhaust gas into power to generate compressed air, and supplies the compressed air to an in-ship consumer, such as an air lubrication system. In this case, the air lubrication system reduces frictional resistance with seawater during operation of the ship, improving the fuel efficiency of the ship.

[0057] The exhaust gas waste heat recovery system of the present invention applies an organic Rankine cycle (ORC) suitable for recovering low-temperature exhaust gas waste heat, and recovers the waste heat of exhaust gas discharged from an engine using a low-flash point fuel by configuring a heat medium circulation line with three heat exchangers, a heat medium circulation line with a condensing heat exchanger that exchanges heat between three fluid flows, or a heat medium circulation line with multiple recuperators to improve the thermal efficiency in the system. The recovered waste heat is then converted into electricity to generate electricity and compressed air that can be consumed in the ship, and the waste heat of the exhaust gas is effectively utilized, thereby improving the energy efficiency of the ship.

[0058] In addition, the exhaust gas waste heat recovery system of the present invention has a suction pot provided upstream of the supply pump to additionally cool the working fluid condensed in the condensing heat exchanger, thereby preventing cavitation at the suction part of the supply pump caused by steam flowing into the supply pump, thereby improving the stability of the system.

[0059] In addition, the exhaust gas waste heat recovery system of the present invention is configured by dividing the vaporization section into a superheater and a vaporizer according to the temperature of the exhaust gas, and the gas-state working fluid vaporized in the vaporizer and separated into gas and liquid is additionally heated by the high-temperature exhaust gas in the superheater, and the superheated working fluid is supplied to the expansion turbine. This prevents the generation of liquid droplets and improves the waste heat recovery efficiency and the stability of the system. [Brief description of the drawings]

[0060] [Figure 1] 1 is a schematic diagram showing a waste heat recovery system for an exhaust gas for a marine vessel according to a first embodiment of the present invention; [Diagram 2] 5 shows a schematic diagram of a waste heat recovery system for an exhaust gas for a marine vessel according to a second embodiment of the present invention. [Diagram 3] 5 shows a schematic diagram of a marine exhaust gas waste heat recovery system according to a third embodiment of the present invention. [Figure 4] 13 shows a schematic diagram of a marine exhaust gas waste heat recovery system according to a fourth embodiment of the present invention. [Diagram 5] 13 shows a schematic diagram of a waste heat recovery system for an exhaust gas for a marine vessel according to a fifth embodiment of the present invention. [Figure 6] 13 shows a schematic diagram of a marine exhaust gas waste heat recovery system according to a sixth embodiment of the present invention. [Figure 7] 13 shows a schematic diagram of a waste heat recovery system for an exhaust gas for a marine vessel according to a seventh embodiment of the present invention. [Figure 8] 13 shows a schematic diagram of an exhaust gas waste heat recovery system for a marine vessel according to an eighth embodiment of the present invention. [Figure 9] 13 shows a schematic diagram of a marine exhaust gas waste heat recovery system according to a ninth embodiment of the present invention. [Figure 10] 13 shows a schematic diagram of a marine exhaust gas waste heat recovery system according to a tenth embodiment of the present invention. [Figure 11] 13 shows a schematic diagram of an exhaust gas waste heat recovery system for a marine vessel according to an eleventh embodiment of the present invention. [Figure 12] 12 illustrates a schematic diagram of a marine exhaust gas waste heat recovery system according to a twelfth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0061] The operating advantages of the present invention and the objects attained by the embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: FIG.

[0062] Hereinafter, the configuration and operation of the embodiment of the present invention will be described with reference to the accompanying drawings. Note that in this specification and the accompanying drawings, the same components are denoted by the same reference numerals.

[0063] The ships according to the embodiments of the present invention described below are any type of ship equipped with a propulsion engine or a power generation engine that can use liquefied gas as fuel. Examples of such ships include self-propelled ships such as LPG carriers, LNG carriers, liquid hydrogen carriers, and LNG RVs (regasification vessels), as well as floating marine structures that do not have self-propelling capabilities, such as LNG FPSOs (floating production storage offloading) and LNG FSRUs (floating storage reasification units).

[0064] Moreover, the embodiment of the present invention can be applied to any kind of liquefied gas that can be liquefied at a low temperature, transported, and supplied as engine fuel. Examples of such liquefied gas include liquefied petrochemical gases such as LNG (Liquefied Natural Gas), LEG (Liquefied Ethane Gas), LPG (Liquefied Petroleum Gas), liquefied ethylene gas, and liquefied propylene gas, and ammonia. In the embodiment described below, ammonia and LPG, which are liquefied gases with low flash points and relatively high boiling points among liquefied gases, are used as engine fuel.

[0065] Fig. 1 shows a schematic diagram of a waste heat recovery system for exhaust gas for a ship according to a first embodiment of the present invention, and Fig. 2 shows a schematic diagram of a waste heat recovery system for exhaust gas for a ship according to a second embodiment of the present invention.

[0066] As shown in FIGS. 1 and 2 , the exhaust gas waste heat recovery system of the first and second embodiments includes a heat medium circulation line RCL that is provided on a ship and through which a working fluid circulates, a carburetor 100 that is provided in the heat medium circulation line RCL and vaporizes the working fluid by heat exchange with exhaust gas discharged from an engine of the ship, and an expansion turbine 200 that is provided in the heat medium circulation line RCL and expands the working fluid to generate shaft power.

[0067] In the first and second embodiments, a liquefied gas having a low flash point is supplied as fuel to an engine (not shown). The working fluid circulates through a closed loop heat medium circulation line RCL and changes phase from liquid to gas using exhaust gas discharged from an engine that uses the liquefied gas having a low flash point as fuel as a heat source.

[0068] Here, ammonia and LPG have relatively high boiling points among liquefied gases with low flash points, and LPG, which is mainly composed of propane, has a flash point of -105°C and a boiling point of -42°C under standard pressure. The boiling point of ammonia is -33°C under standard pressure, which is higher than that of methane (LNG), which has a boiling point of -161°C under standard pressure, and hydrogen, which has a boiling point of -253°C under standard pressure. Therefore, when ammonia or LPG is supplied to an engine as fuel, the amount of heat required to heat it up to the supply temperature required by the engine is very small, and it can be supplied to the engine as fuel after being heated with engine cooling water or the like without using steam generated by using high-temperature exhaust gas discharged from the engine. In addition, since the fuel does not contain sulfur components, low-temperature corrosion is unlikely to occur, and waste heat can be recovered from exhaust gas with a temperature of 150°C or less. Therefore, in the first and second embodiments, an organic Rankine cycle suitable for recovering low-temperature waste heat is applied to the heat medium circulation line RCL to recover waste heat from exhaust gas discharged from the engine.

[0069] The heat medium circulation line RCL is provided with: a carburetor 100 that vaporizes the working fluid by heat exchange with exhaust gas; an expansion turbine 200 that expands the working fluid vaporized in the carburetor 100 to generate shaft power; a condenser 300 that cools and condenses the working fluid cooled by expansion in the expansion turbine 200; and a supply pump 400 that pressurizes the working fluid condensed in the condenser 300 and supplies it to the carburetor 100.

[0070] In the systems of the first and second embodiments, the working fluid circulating through the heat medium circulation line RCL may be, for example, an organic refrigerant or an aqueous ammonia solution. The working fluid is supplied in a liquid state to the supply pump 400, and is pressurized by the supply pump 400 to a pressure required for driving the expansion turbine 200, and then supplied to the vaporizer 100. In the vaporizer 100, the working fluid is heated by waste heat of the exhaust gas HM supplied through the exhaust gas supply line HRL, and the heated and vaporized gaseous working fluid is supplied to the expansion turbine 200. The gaseous working fluid expands in the expansion turbine 200 to drive the turbine and generate shaft power. In addition, the working fluid partially cooled by the expansion is supplied to the condenser 300. In the condenser 300, the working fluid before being supplied to the supply pump 400 is further cooled and condensed by the cooling water CM supplied from the cooling water supply line CRL. Then, the condensed liquid working fluid is supplied to the supply pump 400. In this manner, the working fluid undergoes a phase change while circulating through the closed-loop heat medium circulation line RCL, thereby recovering the waste heat of the exhaust gas and converting it into power.

[0071] The shaft power generated by the expansion turbine 200 using the waste heat of the exhaust gas can be used to drive a generator to generate electric power. In the first and second embodiments, a compressor 250 that compresses air using the shaft power generated by the expansion turbine 200 and an air supply line AL that supplies air to the compressor 250 are provided. The compressed air compressed by the compressor 250 is supplied to a consumer CS in the ship through the air supply line AL. The compressor 250 can also be connected to the expansion turbine 200 via a shaft. The compression ratio of the compressor 250 can be determined according to a consumer in the ship to which the compressed air is supplied.

[0072] Furthermore, the consumer CS within the ship to which the compressed air is supplied may be, for example, an air lubrication system that injects air onto the outside bottom surface of the ship's hull. The air lubrication system injects air onto the outside bottom surface of the hull to form a continuous air layer between the hull and seawater, thereby reducing frictional resistance between the hull and seawater during operation and improving the fuel efficiency of the ship.

[0073] The air lubrication system is configured to include an air compressor (not shown) that compresses air to generate compressed air, piping for supplying compressed air, an air injection unit (not shown), an air layer (not shown) formed on the outer surface of the bottom of the hull, a control unit (not shown), and the like. Compressed air generated in a waste heat recovery system can also be supplied to the air lubrication system. In the systems of the first and second embodiments, air is compressed in a compressor 250 using shaft power generated in an expansion turbine 200, and the compressed air compressed in the compressor 250 is supplied to the air lubrication system. In this way, since the compressor of the waste heat recovery system can be used instead of the air compressor of the air lubrication system, there is no need to separately provide an air compressor or the like in the air lubrication system. Even if an air compressor is provided in the air lubrication system, a capacity that is insufficient in the air compressor can be supplemented by compressed air generated in the waste heat recovery system, so that an air compressor with a smaller capacity can be used. In addition, when compressed air is supplied to the air lubrication system, the compressor 250 is operated at a compression ratio of about 2. In this case, the compressor 250 may be a single-stage centrifugal compressor.

[0074] As described above, the systems of the first and second embodiments recover waste heat from exhaust gas discharged from an engine that uses low flash point fuel. In addition, the recovered waste heat is converted into electricity or compressed air is generated and supplied to an air lubrication system that consumes the energy on the ship, thereby reducing frictional resistance with seawater during ship operation and improving the fuel efficiency and energy efficiency of the ship.

[0075] 2 differs from the system of the first embodiment in that some components are added so that surplus compressed air can be supplied from the turbocharger 500 to a waste heat recovery system and then to a consumer within the ship. Hereinafter, a description of the same components as in the first embodiment will be omitted, and the following description will focus on the components that differ from the first embodiment.

[0076] As shown in FIG. 2, the system of the second embodiment further includes a turbocharger 500 that supercharges scavenge air to be supplied to an engine, a scavenging air supply line SL that cools the scavenging air compressed by the turbocharger 500 and supplies it to the engine, a branch line BL branching off from the scavenging air supply line SL and connected to the air supply line AL downstream of the compressor 250, and a branch valve BV provided in the branch line BL.

[0077] In order to improve the efficiency of the ship engine, intake air (called scavenging air) compressed to a high pressure by a turbocharger 500 is supplied to the engine. The compressed air compressed to a high pressure by the turbocharger 500 and heated to a high temperature is supplied to a scavenging air cooler SC to be cooled and then supplied to the engine. The scavenging air pressure supplied to the engine varies depending on the engine load (Load) and the outside air temperature, and when the scavenging air pressure is high, it is necessary to discharge (vent) a part of the scavenging air in order to adjust the scavenging air pressure. In this embodiment, when the scavenging air pressure is high and it is necessary to discharge a part of the scavenging air in order to adjust the pressure, the surplus compressed air is supplied to the downstream side of the compressor 250 of the air supply line AL by a branch line BL, and then supplied to a consumer CS in the ship, such as an air lubrication system, for use.

[0078] That is, when the pressure of the scavenging air compressed by the turbocharger 500 is higher than the outlet pressure of the compressor and it is necessary to reduce the scavenging air pressure supplied to the engine, the opening of the branch valve BV provided in the branch line BL is adjusted according to the scavenging air pressure detected by the pressure transmitter PT provided in the scavenging air supply line SL, and a part of the scavenging air compressed by the turbocharger 500 is supplied to the air supply line AL, and this is supplied to the consumer CS inside the ship.

[0079] As described above, in the system of the second embodiment, the scavenging air pressure supplied to the engine is adjusted in response to engine load fluctuations, and surplus compressed air from the turbocharger 500 is supplied to consumers within the ship.

[0080] Next, Fig. 3 shows a schematic diagram of a waste heat recovery system for exhaust gas for a ship according to a third embodiment of the present invention, and Fig. 4 shows a schematic diagram of a waste heat recovery system for exhaust gas for a ship according to a fourth embodiment of the present invention.

[0081] As shown in Figures 3 and 4, the exhaust gas waste heat recovery system of the third and fourth embodiments is provided with a heat medium circulation line RCL that is provided on a ship and through which a working fluid circulates, a carburetor 100 that is provided in the heat medium circulation line RCL and heats and vaporizes the working fluid by heat exchange with exhaust gas discharged from an engine of the ship, a gas-liquid separator 200 that separates the working fluid heated (vaporized) by the carburetor 100 into gas and liquid, and an expansion turbine 300 that is provided in the heat medium circulation line RCL and expands the working fluid to generate shaft power.

[0082] In the third and fourth embodiments, a liquefied gas having a low flash point is supplied as fuel to an engine (not shown). The working fluid circulates through a closed loop heat medium circulation line RCL and changes phase from liquid to gas using exhaust gas discharged from an engine that uses the liquefied gas having a low flash point as fuel as a heat source.

[0083] Here, ammonia and LPG have relatively high boiling points among liquefied gases with low flash points, and LPG, which is mainly composed of propane, has a flash point of -105°C and a boiling point of -42°C under standard pressure. The boiling point of ammonia is -33°C under standard pressure, which is higher than that of methane (LNG), which has a boiling point of -161°C under standard pressure, and hydrogen, which has a boiling point of -253°C under standard pressure. Therefore, when ammonia or LPG is supplied to an engine as fuel, the amount of heat required to heat it up to the supply temperature required by the engine is very small, and it can be supplied to the engine as fuel after being heated with engine cooling water or the like without using steam generated by using high-temperature exhaust gas discharged from the engine. In addition, since the fuel does not contain sulfur components, low-temperature corrosion is unlikely to occur, and waste heat can be recovered from exhaust gas with a temperature of 150°C or less. Therefore, in the third and fourth embodiments, an organic Rankine cycle suitable for recovering low-temperature waste heat is applied to the heat medium circulation line RCL to recover waste heat from exhaust gas discharged from the engine.

[0084] The heat medium circulation line RCL is provided with a carburetor 100 that heats and vaporizes the working fluid by heat exchange with the exhaust gas, a gas-liquid separator 200 that separates the working fluid heated (vaporized) by the carburetor 100 into gas and liquid, an expansion turbine 300 that expands the gaseous working fluid separated by the gas-liquid separator 200 to generate shaft power, a condenser 500 that cools and condenses the working fluid cooled by expansion in the expansion turbine 300, a supply pump 600 that pressurizes and sends out the working fluid condensed by the condenser 500, and a recuperator 400a or 400b that heats the working fluid pressurized by the supply pump 600. The working fluid heated by the recuperator 400a or 400b is supplied to the carburetor 100. In addition, the liquid working fluid separated in the gas-liquid separator 200 is supplied to the heat medium circulation line RCL downstream of the expansion turbine 300 via the liquid line LLa or LLb, and is supplied to the condenser 500 together with the working fluid discharged from the expansion turbine 300.

[0085] In the system of the third embodiment, a fluid having a boiling point lower than that of water can be used as the working fluid circulating through the heat medium circulation line RCL so that the waste heat of the low-temperature exhaust gas can also be recovered.

[0086] As shown in FIG. 3, in the system of the third embodiment, the liquid-state working fluid condensed in the condenser 500 is pressurized by the supply pump 600 to a pressure required for driving the expansion turbine 300, and is then supplied to the recuperator 400a, and is then supplied to the vaporizer 100. In the recuperator 400a, downstream of the junction of the heat medium circulation line RCL with the liquid line LLa, the working fluid pressurized by the supply pump 600 is heated by heat exchange with the working fluid before being supplied to the condenser 500. That is, in the recuperator 400a, the working fluid pressurized by the supply pump 600 and sent out from the supply pump 600 is heat-exchanged with the working fluid before being supplied to the condenser 500. The working fluid discharged from the recuperator 400a and supplied to the vaporizer 100 is heated and vaporized by the waste heat of the exhaust gas HM supplied from the exhaust gas supply line HL, and the gaseous working fluid separated by the gas-liquid separator 200 is then supplied to the expansion turbine 300. The working fluid in a gaseous state expands in the expansion turbine 300 to drive the turbine and generate shaft power. The working fluid partially cooled by the expansion is supplied to the recuperator 400a for heat exchange, and then supplied to the condenser 500. In the condenser 500, the working fluid before being supplied to the supply pump 600 is further cooled (additionally cooled) and condensed by cooling water CM supplied from a cooling water supply line CL. The condensed working fluid in a liquid state is then supplied to the supply pump 600. In this manner, the working fluid circulates through the closed-loop heat medium circulation line RCL with a phase change, thereby recovering waste heat from the exhaust gas and converting it into power.

[0087] In addition, in this embodiment, the shaft power SP generated in the expansion turbine 300 by utilizing the waste heat of the exhaust gas can be used to drive a generator to generate electricity, and the shaft power SP may also be used in a compressor to generate compressed air to be supplied to consumers on the ship.

[0088] Also, a compressor (not shown) may be configured to be connected to the expansion turbine 300 via a shaft. The compression ratio of the compressor may be determined depending on the destination of consumption within the ship to which the compressed air is supplied.

[0089] In addition, the consumer CS within the ship to which the compressed air is supplied may be, for example, an air lubrication system that injects air onto the outside bottom surface of the ship's hull. The air lubrication system injects air onto the outside bottom surface of the hull to form a continuous air layer between the hull and seawater, thereby reducing frictional resistance between the hull and seawater during operation and improving the fuel efficiency of the ship.

[0090] The air lubrication system is configured to include an air compressor (not shown) that compresses air to generate compressed air, a pipe that supplies compressed air, an air injection unit (not shown), an air layer (not shown) formed on the surface of the bottom outside of the hull, a control unit (not shown), and the like. In addition, compressed air generated in a waste heat recovery system can also be supplied to the air lubrication system. In addition, in the system of this embodiment, air is compressed by a compressor using the shaft power SP generated by the expansion turbine 300, and the compressed air is supplied to the air lubrication system. In this way, since the compressor of the waste heat recovery system can be used instead of the air compressor of the air lubrication system, there is no need to separately provide an air compressor or the like in the air lubrication system. In addition, even if an air compressor is provided in the air lubrication system, a smaller capacity air compressor can be used because the capacity insufficient in the air compressor can be supplemented by compressed air generated in the waste heat recovery system.

[0091] As described above, the system of the third embodiment recovers waste heat from exhaust gas discharged from an engine that uses a low flash point fuel by using the heat medium circulation line RCL provided with three heat exchangers, the carburetor 100, the condenser 500, and the recuperator 400a. In addition, the recovered waste heat is converted into electricity or compressed air is generated and supplied to consumers within the ship, thereby improving the energy efficiency of the ship.

[0092] 4 differs from the system of the third embodiment in the position where the recuperator 400b is provided. In the following, the description will be omitted for the same configuration as the system of the third embodiment, and the description will be centered on the configuration that differs from the third embodiment.

[0093] As shown in FIG. 4, the system of the fourth embodiment is configured such that in the recuperator 400b, the working fluid pressurized by the supply pump 600 is heated by heat exchange with the liquid working fluid separated in the gas-liquid separator 200 and flowing through the liquid line LLb.

[0094] By arranging the recuperator 400b in this manner, it is possible to recover thermal energy from the working fluid that remains in a liquid state and does not vaporize even when heated by the waste heat of the exhaust gas in the carburetor 100, and to preheat the working fluid discharged from the condenser 500 and the supply pump 600 before supplying it to the carburetor 100.

[0095] In the system of the fourth embodiment, the working fluid circulating through the heat medium circulation line RCL may be, for example, an aqueous ammonia solution. When the aqueous ammonia solution is heated by heat exchange with low-temperature exhaust gas in the vaporizer 100, the ammonia having a low boiling point is vaporized into a gaseous state, but water may remain in a liquid state without being vaporized. The gaseous ammonia separated in the gas-liquid separator 200 is supplied to the expansion turbine 300. On the other hand, the water separated in the gas-liquid separator 200 is supplied to the recuperator 400b through the liquid line LLb, and after thermal energy is recovered, it is supplied to the upstream side of the condenser 500 of the heat medium circulation line RCL, and is supplied to the condenser 500 together with the ammonia discharged from the expansion turbine 300 and condensed.

[0096] As described above, the system of the fourth embodiment improves the thermal efficiency of the ship by effectively recovering the waste heat of the exhaust gas by the heat medium circulation line RCL provided with three heat exchangers. In addition, by using an aqueous ammonia solution as the working fluid of the heat medium circulation line RCL, refilling and management of the working fluid becomes easy. In particular, when the system of this embodiment is applied to an ammonia-fuel propulsion ship or an ammonia carrier that uses ammonia as engine fuel, ammonia as fuel or cargo can be directly used as the working fluid of the heat medium circulation line RCL, so there is no need to separately install a refrigerant management system, and the installation costs of related facilities such as a refrigerant storage tank can be reduced.

[0097] Fig. 5 shows a schematic diagram of a waste heat recovery system for exhaust gas for a ship according to a fifth embodiment of the present invention. Also, Fig. 6 shows a schematic diagram of a waste heat recovery system for exhaust gas for a ship according to a sixth embodiment of the present invention.

[0098] As shown in Figures 5 and 6, the exhaust gas waste heat recovery system of the fifth and sixth embodiments is provided with: a heat medium circulation line RCL that is provided on a ship and through which a working fluid circulates; a carburetor 100 that is provided in the heat medium circulation line RCL and heats and vaporizes the working fluid by heat exchange with exhaust gas discharged from an engine of the ship; a gas-liquid separator 200 that separates the working fluid heated (vaporized) by the carburetor 100 into gas and liquid; and an expansion turbine 300 that is provided in the heat medium circulation line RCL and expands the working fluid to generate shaft power.

[0099] In the fifth and sixth embodiments, a liquefied gas having a low flash point is supplied as fuel to an engine (not shown). The working fluid circulates through a closed loop heat medium circulation line RCL and changes phase from liquid to gas using exhaust gas discharged from an engine that uses the liquefied gas having a low flash point as fuel as a heat source.

[0100] Here, ammonia and LPG have relatively high boiling points among liquefied gases with low flash points, and LPG, which is mainly composed of propane, has a flash point of -105°C and a boiling point of -42°C under standard pressure. The boiling point of ammonia is -33°C under standard pressure, which is higher than that of methane (LNG), which has a boiling point of -161°C under standard pressure, and hydrogen, which has a boiling point of -253°C under standard pressure. For this reason, when ammonia or LPG is supplied to an engine as fuel, the amount of heat required to heat the fuel to the supply temperature required by the engine is very small, and the fuel can be supplied to the engine as fuel after being heated with engine cooling water or the like without using steam generated by using high-temperature exhaust gas discharged from the engine. In addition, since the fuel does not contain sulfur components, low-temperature corrosion is unlikely to occur, and waste heat can be recovered from exhaust gas with a temperature of 150°C or less. Therefore, in the fifth and sixth embodiments, an organic Rankine cycle suitable for recovering low-temperature waste heat is applied to the heat medium circulation line RCL to recover waste heat from exhaust gas discharged from the engine.

[0101] The heat medium circulation line RCL is provided with a vaporizer 100 that heats and vaporizes the working fluid by heat exchange with the exhaust gas, a gas-liquid separator 200 that separates the working fluid heated (vaporized) by the vaporizer 100 into gas and liquid, an expansion turbine 300 that expands the gaseous working fluid separated by the gas-liquid separator 200 to generate shaft power, a condensation heat exchanger 400 that cools and condenses the working fluid cooled by expansion in the expansion turbine 300, and a supply pump 600 that pressurizes the working fluid condensed by the condensation heat exchanger 400 and sends it to the vaporizer 100. The liquid working fluid separated by the gas-liquid separator 200 is supplied to the downstream side of the expansion turbine 300 of the heat medium circulation line RCL by the liquid line LLa or LLb, and is supplied to the condensation heat exchanger 400 together with the working fluid discharged from the expansion turbine 300.

[0102] In the condensation heat exchanger 400, the working fluid partially cooled by expansion in the expansion turbine 300 and the working fluid supplied from the liquid line LLa or LLb are cooled and condensed. Then, the condensed liquid state working fluid is supplied to the supply pump 600. In addition, in the systems of the fifth and sixth embodiments, cooling water for cooling the working fluid is supplied to the condensation heat exchanger 400 from the first cooling water supply line CL1. In addition, the working fluid condensed in the condensation heat exchanger 400 and pressurized by the supply pump 600 is supplied to the condensation heat exchanger 400 before being supplied to the vaporizer 100. As a result, in the condensation heat exchanger 400, heat exchange is performed between three flows of fluids, namely, the flow of the working fluid in the heat medium circulation line RCL cooled by expansion in the expansion turbine 300, the flow of the working fluid in the heat medium circulation line RCL pressurized by the supply pump 600 and supplied to the vaporizer 100, and the flow of the cooling water in the first cooling water supply line CL1.

[0103] By exchanging heat among the three fluid flows, in the condensation heat exchanger 400, the working fluid cooled by expansion in the expansion turbine 300 is supplied with cold heat from the other two flows, and the working fluid cooled by expansion in the expansion turbine 300 is effectively condensed. In addition, the working fluid pressurized by the supply pump 600 can be preheated before being supplied to the vaporizer 100. For this reason, the condensation heat exchanger 400 functions as a condenser that condenses the working fluid in a gaseous state, and also functions as a recuperator that preheats the working fluid pressurized by the supply pump 600 before being supplied to the vaporizer 100. This makes it possible to reduce the number of devices and maximize the thermal efficiency of the ship.

[0104] In the system of the fifth embodiment, a fluid having a boiling point lower than that of water can be used as the working fluid circulating through the heat medium circulation line RCL so that the waste heat of the low-temperature exhaust gas can also be recovered.

[0105] As shown in FIG. 5, in the system of the fifth embodiment, the liquid-state working fluid condensed in the condensation heat exchanger 400 is pressurized by the supply pump 600 to a pressure required for driving the expansion turbine 300, and is then supplied to the condensation heat exchanger 400 and then to the vaporizer 100. The working fluid preheated in the condensation heat exchanger 400 and then supplied to the vaporizer 100 is heated and vaporized by the waste heat of the exhaust gas HM supplied from the exhaust gas supply line HL, and the gaseous working fluid separated in the gas-liquid separator 200 is supplied to the expansion turbine 300. The gaseous working fluid expands in the expansion turbine 300 to drive the turbine and generate shaft power. In addition, the working fluid partially cooled by the expansion is supplied to the condensation heat exchanger 400. In the condensation heat exchanger 400, the working fluid partially cooled by expansion in the expansion turbine 300 is further cooled (added) and condensed by the flow of the cooling water CM supplied from the first cooling water supply line CL and the flow of the working fluid sent out from the supply pump 600 and before being supplied to the evaporator 100. The condensed working fluid in a liquid state is then supplied to the supply pump 600 and pressurized to a pressure required to drive the expansion turbine 300.

[0106] In this embodiment, a suction pot 500 is provided downstream of the condensation heat exchanger 400 on the heat medium circulation line RCL to further cool (additionally cool) the working fluid condensed in the condensation heat exchanger 400 before supplying it to the supply pump 600. A second cooling water supply line CL2 that supplies cooling water is connected to the suction pot 500. The working fluid before being supplied to the supply pump 600 is further cooled (additionally cooled) by heat exchange with the cooling water supplied from the second cooling water supply line CL2. In this way, the working fluid cooled in the condensation heat exchanger 400 is further cooled in the suction pot 500 and then supplied to the supply pump 600, thereby preventing cavitation at the suction part of the supply pump caused by vapor flowing into the supply pump, and improving the stability of the system.

[0107] The working fluid in a liquid state, which is cooled and condensed in the condensation heat exchanger 400 and then further cooled in the suction pot 500, is pressurized by the supply pump 600, and is then supplied to the condensation heat exchanger 400, where it is preheated, and then supplied to the vaporizer 100. In this way, the working fluid circulates through the closed-loop heat medium circulation line RCL with a phase change, thereby recovering the waste heat of the exhaust gas and converting it into power.

[0108] In addition, in this embodiment, the shaft power SP generated in the expansion turbine 300 by utilizing the waste heat of the exhaust gas can be used to drive a generator to generate electricity, and the shaft power SP may also be used in a compressor to generate compressed air to be supplied to consumers on the ship.

[0109] Also, a compressor (not shown) may be configured to be connected to the expansion turbine 300 via a shaft. The compression ratio of the compressor may be determined depending on the destination of consumption within the ship to which the compressed air is supplied.

[0110] In addition, the consumer CS within the ship to which the compressed air is supplied may be, for example, an air lubrication system that injects air onto the outside bottom surface of the ship's hull. The air lubrication system injects air onto the outside bottom surface of the hull to form a continuous air layer between the hull and seawater, thereby reducing frictional resistance between the hull and seawater during operation and improving the fuel efficiency of the ship.

[0111] The air lubrication system is configured to include an air compressor (not shown) that compresses air to generate compressed air, a pipe that supplies compressed air, an air injection unit (not shown), an air layer (not shown) formed on the surface of the bottom outside of the hull, a control unit (not shown), and the like. In addition, compressed air generated in a waste heat recovery system can also be supplied to the air lubrication system. In addition, in the system of this embodiment, air is compressed by a compressor using the shaft power SP generated by the expansion turbine 300, and the compressed air is supplied to the air lubrication system. In this way, since the compressor of the waste heat recovery system can be used instead of the air compressor of the air lubrication system, there is no need to separately provide an air compressor or the like in the air lubrication system. In addition, even if an air compressor is provided in the air lubrication system, a smaller capacity air compressor can be used because the capacity insufficient in the air compressor can be supplemented by compressed air generated in the waste heat recovery system.

[0112] As described above, the system of the fifth embodiment recovers waste heat from exhaust gas discharged from an engine that uses a low flash point fuel by using the heat medium circulation line RCL provided with the condensation heat exchanger 400 that exchanges heat between three fluid flows. In addition, the recovered waste heat is converted into electricity or compressed air is generated and supplied to the ship's consumers, thereby improving the energy efficiency of the ship.

[0113] 6 differs from the system of the above-mentioned fifth embodiment in that a recuperator 450 is additionally provided to recover thermal energy from the liquid working fluid that is separated in the gas-liquid separator 200 and flows through the liquid line LLb. In the following, a description of the configuration that is the same as that of the system of the fifth embodiment will be omitted, and the configuration that differs from that of the above-mentioned fifth embodiment will be mainly described.

[0114] 6, in the system of the sixth embodiment, a recuperator 450 is provided in the heat medium circulation line RCL, which further heats (additionally heats) the working fluid that has been pressurized by the supply pump 500 and then heat-exchanged in the condensation heat exchanger 400 before being supplied to the vaporizer 100. In the recuperator 450, the working fluid that has been pressurized and preheated by the supply pump 600 and the condensation heat exchanger 400 is heated by heat exchange with the working fluid in a liquid state that has been separated in the gas-liquid separator 200 and flows through the liquid line LLb.

[0115] By arranging the recuperator 450 in this manner, thermal energy can be recovered from the working fluid that remains in a liquid state and does not vaporize even when heated by the waste heat of the exhaust gas in the evaporator 100, and the working fluid discharged from the supply pump 500 and the condensation heat exchanger 400 can be preheated before being supplied to the evaporator 100.

[0116] In the system of the sixth embodiment, the working fluid circulating through the heat medium circulation line RCL may be, for example, an aqueous ammonia solution. When the aqueous ammonia solution is heated by heat exchange with low-temperature exhaust gas in the vaporizer 100, the ammonia having a low boiling point is vaporized into a gaseous state, but water may be in a liquid state without being vaporized. The gaseous ammonia separated in the gas-liquid separator 200 is supplied to the expansion turbine 300. On the other hand, the water separated in the gas-liquid separator 200 is supplied to the recuperator 450 through the liquid line LLb, and after thermal energy is recovered, it is supplied to the upstream side of the condensing heat exchanger 400 of the heat medium circulation line RCL, and is supplied to the condensing heat exchanger 400 together with the ammonia discharged from the expansion turbine 300 and condensed.

[0117] As described above, the system of the sixth embodiment is provided with the condensing heat exchanger 400 that exchanges heat between the three fluid flows, effectively recovers the waste heat of the exhaust gas, and improves the thermal efficiency of the ship, thereby simplifying the system configuration and maximizing the thermal efficiency of the ship. In addition, by using an aqueous ammonia solution as the working fluid of the heat medium circulation line RCL, it becomes easy to replenish and manage the working fluid. In particular, when the system of this embodiment is applied to an ammonia-fuel propulsion ship or an ammonia carrier that uses ammonia as engine fuel, ammonia as fuel or cargo can be directly used as the working fluid of the heat medium circulation line RCL, so there is no need to separately install a refrigerant management system, and the installation costs of related equipment such as a refrigerant storage tank can be reduced.

[0118] Fig. 7 is a schematic diagram of a waste heat recovery system for exhaust gas for a ship according to a seventh embodiment of the present invention. Fig. 8 is a schematic diagram of a waste heat recovery system for exhaust gas for a ship according to an eighth embodiment of the present invention.

[0119] As shown in Figures 7 and 8, the exhaust gas waste heat recovery system of the seventh and eighth embodiments includes a heat medium circulation line RCL that is provided on a ship and through which a working fluid circulates, an evaporation unit 100A or 100B that is provided in the heat medium circulation line RCL and heats and vaporizes the working fluid by heat exchange with exhaust gas discharged from an engine of the ship, a gas-liquid separator 200 that separates the working fluid heated (vaporized) in the evaporation unit 100A or 100B into gas and liquid, and an expansion turbine 300 that is provided in the heat medium circulation line RCL and expands the working fluid to generate shaft power.

[0120] In the seventh and eighth embodiments, a liquefied gas having a low flash point is supplied as fuel to an engine (not shown). The working fluid circulates through a closed loop heat medium circulation line RCL and changes phase from liquid to gas using exhaust gas discharged from an engine that uses the liquefied gas having a low flash point as fuel as a heat source.

[0121] Here, ammonia and LPG have relatively high boiling points among liquefied gases with low flash points, and LPG, which is mainly composed of propane, has a flash point of -105°C and a boiling point of -42°C under standard pressure. The boiling point of ammonia is -33°C under standard pressure, which is higher than that of methane (LNG), which has a boiling point of -161°C under standard pressure, and hydrogen, which has a boiling point of -253°C under standard pressure. For this reason, when ammonia or LPG is supplied to an engine as fuel, the amount of heat required to heat the fuel to the supply temperature required by the engine is very small, and the fuel can be supplied to the engine as fuel after being heated with engine cooling water or the like without using steam generated by using high-temperature exhaust gas discharged from the engine. In addition, since the fuel does not contain sulfur components, low-temperature corrosion is unlikely to occur, and waste heat can be recovered from exhaust gas with a temperature of 150°C or less. Therefore, in the seventh and eighth embodiments, an organic Rankine cycle suitable for recovering low-temperature waste heat is applied to the heat medium circulation line RCL to recover waste heat from exhaust gas discharged from the engine.

[0122] The heat medium circulation line RCL is provided with an evaporation section 100A or 100B that heats and vaporizes the working fluid by heat exchange with the exhaust gas, a gas-liquid separator 200 that separates the working fluid heated (vaporized) in the evaporation section 100A or 100B into gas and liquid, an expansion turbine 300 that expands the gaseous working fluid separated in the gas-liquid separator 200 to generate shaft power, a condensation heat exchanger 400 that cools and condenses the working fluid cooled by expansion in the expansion turbine 300, and a supply pump 500 that pressurizes the working fluid condensed in the condensation heat exchanger 400 and sends it to the evaporation section 100A or 100B. The liquid working fluid separated in the gas-liquid separator 200 is supplied to the downstream side of the expansion turbine 300 of the heat medium circulation line RCL by a liquid line LLa or LLb, and is supplied to the condensation heat exchanger 400 together with the working fluid discharged from the expansion turbine 300.

[0123] In the condensation heat exchanger 400, the working fluid partially cooled by expansion in the expansion turbine 300 and the working fluid supplied from the liquid line LLa or LLb are cooled and condensed. Then, the condensed liquid state working fluid is supplied to the supply pump 500. In the systems of the seventh and eighth embodiments, the cooling water CM for cooling the working fluid is supplied to the condensation heat exchanger 400 from the cooling water supply line CL. In addition, the working fluid condensed in the condensation heat exchanger 400 and pressurized by the supply pump 500 is supplied to the condensation heat exchanger 400 before being supplied to the evaporation unit 100A or 100B. As a result, the condensation heat exchanger 400 exchanges heat between three fluid flows: the flow of the working fluid in the heat medium circulation line RCL cooled by expansion in the expansion turbine 300, the flow of the working fluid in the heat medium circulation line RCL pressurized by the supply pump 500 and supplied to the evaporation unit 100A or 100B, and the flow of the cooling water CM in the cooling water supply line CL.

[0124] By exchanging heat among the three fluid flows, in the condensation heat exchanger 400, the working fluid cooled by expansion in the expansion turbine 300 is supplied with cold heat from the other two flows, and the working fluid cooled by expansion in the expansion turbine 300 is effectively condensed. In addition, the working fluid pressurized by the supply pump 600 can be preheated before being supplied to the vaporization unit 100A or 100B. Therefore, the condensation heat exchanger 400 has a function as a condenser that condenses the gaseous working fluid into a liquid, and also has a function as a recuperator that preheats the working fluid pressurized by the supply pump 500 before being supplied to the vaporization unit 100A or 100B. This reduces the number of devices and maximizes the thermal efficiency of the ship.

[0125] In the systems of the seventh and eighth embodiments, the vaporizer 100A or 100B includes a vaporizer 110a or 110b and a superheater 120a or 120b, which are provided in accordance with the flow direction of the working fluid delivered from the supply pump 500. The exhaust gas HM supplied from the exhaust gas supply line HL is supplied to the superheater 120a or 120b of the vaporizer 100A or 100B, and then to the vaporizer 110a or 110b of the vaporizer 100A or 100B. The exhaust gas supplied to the superheater 120a or 120b has a higher temperature than the exhaust gas supplied to the vaporizer 110a or 110b.

[0126] As shown in FIG. 7, in the system of the seventh embodiment, the working fluid pressurized by the supply pump 500 is preheated by the condensation heat exchanger 400, and then the working fluid vaporized by heat exchange with a relatively low-temperature exhaust gas in the vaporizer 110a of the vaporization unit 100A is separated into gas and liquid in the gas-liquid separator 200. The gaseous working fluid separated by the gas-liquid separator 200 is supplied to the superheater 120a of the vaporization unit 100A, further heated (additionally heated) by the relatively high-temperature exhaust gas, and then supplied to the expansion turbine 300. In this way, in the system of the seventh embodiment, the working fluid before being supplied to the expansion turbine 300 is additionally heated to a superheated state by the high-temperature exhaust gas in the superheater 120a, thereby preventing the generation of droplets. In addition, the system of this embodiment can improve the waste heat recovery efficiency and the stability of the system.

[0127] In the system of the seventh embodiment, a fluid having a boiling point lower than that of water can be used as the working fluid circulating through the heat medium circulation line RCL so that the waste heat of the low-temperature exhaust gas can also be recovered.

[0128] As shown in FIG. 7, in the system of the seventh embodiment, the working fluid in a liquid state condensed in the condensing heat exchanger 400 is pressurized to a required pressure by the supply pump 500 by driving the expansion turbine 300, and is supplied to the condensing heat exchanger 400 for preheating, and then supplied to the vaporizer 110a of the vaporization unit 100A. The working fluid preheated in the condensing heat exchanger 400 and then supplied to the vaporizer 110a is heated and vaporized by the waste heat of the exhaust gas HM supplied from the exhaust gas supply line HL, and the gaseous working fluid separated in the gas-liquid separator 200 is supplied to the superheater 120a of the vaporization unit 100A. The working fluid supplied to the superheater 120a is heated to a superheated state by the high-temperature exhaust gas HM supplied from the exhaust gas supply line HL, and is supplied to the expansion turbine 300. The working fluid in a gaseous state is expanded in the expansion turbine 300 to drive the turbine and generate shaft power. Furthermore, the working fluid partially cooled by expansion is supplied to the condensation heat exchanger 400. In the condensation heat exchanger 400, the working fluid is further cooled (additionally cooled) and condensed by the flow of the cooling water CM supplied from the cooling water supply line CL and the flow of the working fluid sent out from the supply pump 500 and before being supplied to the evaporator 110a. The condensed working fluid in a liquid state is then supplied to the supply pump 500 and pressurized to a pressure required to drive the expansion turbine 300.

[0129] The working fluid pressurized by the supply pump 500 is supplied to the condensation heat exchanger 400, where it is preheated, and then supplied to the vaporizer 110a. In this manner, the working fluid undergoes a phase change while circulating through the closed-loop heat medium circulation line RCL, thereby recovering the waste heat of the exhaust gas and converting it into power.

[0130] In addition, in this embodiment, the shaft power SP generated in the expansion turbine 300 by utilizing the waste heat of the exhaust gas can be used to drive a generator to generate electricity, and the shaft power SP may also be used in a compressor to generate compressed air to be supplied to consumers on the ship.

[0131] Also, a compressor (not shown) may be configured to be connected to the expansion turbine 300 via a shaft. The compression ratio of the compressor may be determined depending on the destination of consumption within the ship to which the compressed air is supplied.

[0132] In addition, the consumer CS within the ship to which the compressed air is supplied may be, for example, an air lubrication system that injects air onto the outside bottom surface of the ship's hull. The air lubrication system injects air onto the outside bottom surface of the hull to form a continuous air layer between the hull and seawater, thereby reducing frictional resistance between the hull and seawater during operation and improving the fuel efficiency of the ship.

[0133] The air lubrication system is configured to include an air compressor (not shown) that generates compressed air to be injected outside the bottom surface of the hull, piping that supplies the compressed air, an air injection unit (not shown), an air layer (not shown) formed on the surface of the outside bottom surface of the hull, a control unit (not shown), and the like. In addition, compressed air generated in a waste heat recovery system can also be supplied to the air lubrication system. In addition, in the system of this embodiment, air is compressed by a compressor using the shaft power SP generated by the expansion turbine 300, and the compressed air is supplied to the air lubrication system. In this way, since the compressor of the waste heat recovery system can be used instead of the air compressor of the air lubrication system, there is no need to separately provide an air compressor or the like in the air lubrication system. In addition, even if an air compressor is provided in the air lubrication system, a smaller capacity air compressor can be used because the capacity insufficient in the air compressor can be supplemented by compressed air generated in the waste heat recovery system.

[0134] As described above, the system of the seventh embodiment recovers waste heat from exhaust gas discharged from an engine that uses a low flash point fuel by using the heat medium circulation line RCL provided with the condensation heat exchanger 400 that exchanges heat between three fluid flows. In addition, the recovered waste heat is converted into electricity or compressed air is generated and supplied to the ship's consumers, thereby improving the energy efficiency of the ship.

[0135] 8 differs from the system of the seventh embodiment in that a recuperator 450 that recovers thermal energy from the liquid working fluid separated in the gas-liquid separator 200 and flowing through the liquid line LLb, and an exhaust heat heater 130b that recovers exhaust heat from low-temperature exhaust gas are additionally provided. Hereinafter, a description of the same configuration as the system of the seventh embodiment will be omitted, and the configuration different from the seventh embodiment will be mainly described.

[0136] 8, in the system of the eighth embodiment, a recuperator 450 is provided in the heat medium circulation line RCL to further heat (additionally heat) the working fluid that has been pressurized by the supply pump 500 and then heat exchanged in the condensation heat exchanger 400 before being supplied to the vaporizer 110b of the vaporization section 110B. In the recuperator 450, the working fluid that has been pressurized and preheated by the supply pump 500 and the condensation heat exchanger 400 is heated by heat exchange with the working fluid in a liquid state that has been separated in the gas-liquid separator 200 and flows through the liquid line LLb.

[0137] By arranging the recuperator 450 in this manner, thermal energy can be recovered from the working fluid that remains in a liquid state and does not vaporize even when heated by the waste heat of the exhaust gas in the evaporator 110b, and the working fluid discharged from the supply pump 500 and the condensation heat exchanger 400 can be preheated before being supplied to the evaporator 100.

[0138] In the system of the eighth embodiment, the working fluid circulating through the heat medium circulation line RCL may be, for example, an aqueous ammonia solution. When the aqueous ammonia solution is heated by heat exchange with low-temperature exhaust gas in the vaporizer 110b of the vaporizer 110B, the ammonia with a low boiling point is vaporized into a gaseous state, but water may not be vaporized and may be in a liquid state. The gaseous ammonia separated in the gas-liquid separator 200 is heated to a superheated state in the superheater 120b and then supplied to the expansion turbine 300. On the other hand, the water separated in the gas-liquid separator 200 is supplied to the recuperator 450 through the liquid line LLb, and after thermal energy is recovered, it is supplied to the upstream side of the condensation heat exchanger 400 of the heat medium circulation line RCL, and is supplied to the condensation heat exchanger 400 together with the ammonia discharged from the expansion turbine 300 and condensed.

[0139] In the eighth embodiment, the vaporization section 100B is further provided with an exhaust heater 130b for exchanging heat between the working fluid and the low-temperature exhaust gas supplied to the superheater 120b and the vaporizer 110b from the exhaust gas supply line HL and discharged from the vaporizer 110b. A part of the working fluid that has been pressurized by the supply pump 500 and then heat-exchanged in the condensation heat exchanger 400 is branched by a branch line RCLb, heated by the low-temperature exhaust gas in the exhaust heater 130b, and then supplied to the downstream side of the recuperator 450 of the heat medium circulation line RCL. That is, a part of the working fluid that has been pressurized by the supply pump 500 and then preheated in the condensation heat exchanger 400 is heated by the fluid flow in the liquid line LLb in the recuperator 450, and a part of the branched working fluid is heated by the low-temperature exhaust gas flow in the exhaust heater 130b. Then, these are joined together on the heat medium circulation line RCL downstream of the recuperator 450, and are supplied to the vaporizer 110b of the vaporization section 110B. This makes it possible to further improve the amount of waste heat recovered from the exhaust gas.

[0140] As described above, the system of the eighth embodiment is provided with the condensing heat exchanger 400 that exchanges heat between the three fluid flows, effectively recovers the waste heat of the exhaust gas, and improves the thermal efficiency of the ship, thereby simplifying the system configuration and maximizing the thermal efficiency of the ship. In addition, by using an aqueous ammonia solution as the working fluid of the heat medium circulation line RCL, it becomes easy to replenish and manage the working fluid. In particular, when the system of this embodiment is applied to an ammonia-fuel propulsion ship or an ammonia carrier that uses ammonia as engine fuel, ammonia as fuel or cargo can be directly used as the working fluid of the heat medium circulation line RCL, so there is no need to separately install a refrigerant management system, and the installation costs of related equipment such as a refrigerant storage tank can be reduced.

[0141] 9 to 12 are schematic diagrams showing waste heat recovery systems for exhaust gas for ships according to ninth to twelfth embodiments of the present invention, respectively.

[0142] As shown in Figures 9 to 12, the exhaust gas waste heat recovery system of the ninth to twelfth embodiments is provided with: a heat medium circulation line RCL that is provided on a ship and through which a working fluid circulates; a carburetor 100 that is provided in the heat medium circulation line RCL and heats and vaporizes the working fluid by heat exchange with exhaust gas discharged from an engine of the ship; a gas-liquid separator 200 that separates the working fluid heated (vaporized) by the carburetor 100 into gas and liquid; and an expansion turbine 300 that is provided in the heat medium circulation line RCL and expands the working fluid to generate shaft power.

[0143] In the ninth to twelfth embodiments, a liquefied gas having a low flash point is supplied as fuel to an engine (not shown). The working fluid circulates through a closed loop heat medium circulation line RCL and changes phase from liquid to gas using exhaust gas discharged from an engine that uses the liquefied gas having a low flash point as fuel as a heat source.

[0144] Here, ammonia and LPG have relatively high boiling points among liquefied gases with low flash points, and LPG, which is mainly composed of propane, has a flash point of -105°C and a boiling point of -42°C under standard pressure. The boiling point of ammonia is -33°C under standard pressure, which is higher than that of methane (LNG), which has a boiling point of -161°C under standard pressure, and hydrogen, which has a boiling point of -253°C under standard pressure. For this reason, when ammonia or LPG is supplied to an engine as fuel, the amount of heat required to heat the fuel to the supply temperature required by the engine is very small, and the fuel can be supplied to the engine as fuel after being heated with engine cooling water or the like without using steam generated by using high-temperature exhaust gas discharged from the engine. In addition, since the fuel does not contain sulfur components, low-temperature corrosion is unlikely to occur, and waste heat can be recovered from exhaust gas with a temperature of 150°C or less. Therefore, in the ninth to twelfth embodiments, an organic Rankine cycle suitable for recovering low-temperature waste heat is applied to the heat medium circulation line RCL to recover waste heat from exhaust gas discharged from the engine.

[0145] The heat medium circulation line RCL is provided with an evaporation section 100 that heats and vaporizes the working fluid by heat exchange with the exhaust gas, a gas-liquid separator 200 that separates the working fluid heated (vaporized) in the evaporation section 100 into gas and liquid, an expansion turbine 300 that expands the gaseous working fluid separated in the gas-liquid separator 200 to generate shaft power, a condenser 400 that cools and condenses the working fluid cooled by expansion in the expansion turbine 300, a supply pump 500 that pressurizes the working fluid condensed in the condenser 400 and sends it to the evaporation section 100, and first and second recuperators 600, 650 that heat the working fluid pressurized by the supply pump 500 and supply it to the evaporation section 100. The first and second recuperators 600, 650 have a function of preheating the working fluid pressurized by the supply pump 500 before supplying it to the evaporation section 100. In the first recuperator 600, heat is exchanged between the working fluid pressurized by the supply pump 500 and the working fluid cooled by expansion in the expansion turbine 300 and before being supplied to the condenser 400. In the second recuperators 650a, 650b, 650c, and 650d, the working fluid pressurized by the supply pump 500 is heated by waste heat supplied from a compressor, a cooling device, or the like in the ship. The liquid working fluid separated in the gas-liquid separator 200 is supplied to the heat medium circulation line RCL downstream of the expansion turbine 300 by the liquid line LL, or LLc or LLd, and is supplied to the first recuperator 600 together with the working fluid discharged from the expansion turbine 300, and then is supplied to the condenser 400.

[0146] In the systems of the ninth to twelfth embodiments, the vaporization unit 100 includes a vaporizer 110 and a superheater 120 that are provided in accordance with the flow direction of the working fluid delivered from the supply pump 500. The exhaust gas HM supplied from the exhaust gas supply line HL is supplied to the superheater 120 of the vaporization unit 100, and then supplied to the vaporizer 110 of the vaporization unit 100. The exhaust gas supplied to the superheater 120 has a higher temperature than the exhaust gas supplied to the vaporizer 110.

[0147] As shown in FIG. 9 and FIG. 10, in the systems of the ninth and tenth embodiments, the working fluid pressurized by the supply pump 500 is preheated by the first or second recuperator 600 or 650a or 650b, and then the working fluid vaporized by heat exchange with a relatively low-temperature exhaust gas in the vaporizer 110 is separated into gas and liquid in the gas-liquid separator 200. The gaseous working fluid separated by the gas-liquid separator 200 is supplied to the superheater 120 of the vaporizer 100, and is further heated (additionally heated) by a relatively high-temperature exhaust gas and then supplied to the expansion turbine 300. In this way, in the ninth and tenth embodiments, the working fluid before being supplied to the expansion turbine 300 is additionally heated to a superheated state by the high-temperature exhaust gas in the superheater 120, thereby preventing the generation of droplets. In addition, the system of this embodiment can improve the waste heat recovery efficiency and the stability of the system.

[0148] In the systems of the ninth and tenth embodiments, a fluid having a boiling point lower than that of water can be used as the working fluid circulating through the heat medium circulation line RCL so that waste heat from low-temperature exhaust gas can also be recovered.

[0149] As shown in Figs. 9 and 10, in the systems of the ninth and tenth embodiments, the working fluid in a liquid state condensed by the condenser 400 is pressurized by the supply pump 500 to a pressure required for driving the expansion turbine 300, and is supplied to the first or second recuperator 600 or 650a or 650b for preheating, and then supplied to the vaporizer 110 of the vaporization unit 100. The working fluid pressurized by the supply pump 500 is branched into two flows and supplied to the first recuperator 600 and the second recuperator 650a or 650b, respectively. In the first recuperator 600, the working fluid pressurized by the supply pump 500 is heated by heat exchange with the working fluid discharged from the expansion turbine 300 and before being supplied to the condenser 400, downstream of the junction of the heat medium circulation line RCL with the liquid line LL. In the second recuperator 650a or 650b, the working fluid pressurized by the supply pump 500 is heated by waste heat from air, cooling water, etc. discharged from other devices such as a compressor or a cooling device in the ship. That is, in the first recuperator 600, heat is exchanged between the working fluid pressurized and discharged by the supply pump 500 and the working fluid before being supplied to the condenser 400. In addition, in the second recuperator 650a or 650b, waste heat from other devices in the ship is recovered. The working fluid preheated in the first or second recuperator 600 or 650a or 650b and then supplied to the vaporizer 110 is heated and vaporized by the waste heat of the exhaust gas HM supplied to the vaporizer 110 after being supplied to the superheater 120 from the exhaust gas supply line HL, and the gaseous working fluid separated in the gas-liquid separator 200 is supplied to the superheater 120 of the vaporization unit 100. The working fluid supplied to the superheater 120 is heated to a superheated state by high-temperature exhaust gas supplied from an exhaust gas supply line HL, and is then supplied to the expansion turbine 300. The working fluid in a gaseous state expands in the expansion turbine 300 to drive the turbine and generate shaft power. In addition, the working fluid that has been partially cooled by the expansion is heat exchanged in the first recuperator 600 and supplied to the condenser 400. In the condenser 400, the working fluid is further cooled (additionally cooled) by cooling water supplied from a cooling water supply line CL, and condensed. The condensed working fluid in a liquid state is then supplied to the supply pump 500.In this manner, the working fluid undergoes a phase change while circulating through the closed-loop heat medium circulation line RCL, thereby recovering the waste heat of the exhaust gas and converting it into power.

[0150] In addition, in the system of the ninth embodiment, the shaft power SP generated in the expansion turbine 300 by utilizing the waste heat of the exhaust gas can be used to drive a generator to generate electricity, and the shaft power SP may also be used in a compressor to generate compressed air to be supplied to consumers on board the ship.

[0151] The system of the tenth embodiment shown in FIG. 10 differs from the system of the ninth embodiment in that a compressor 350 is additionally provided, which is connected to the expansion turbine 300 via a shaft.

[0152] As shown in FIG. 10, the system of the tenth embodiment further includes a compressor 350 that compresses air using shaft power generated by the expansion turbine 300, and an air supply line AL that supplies air to the compressor 350.

[0153] In the system of the tenth embodiment, the compressed air compressed by the compressor 350 is supplied to the second recuperator 650b through the air supply line AL to exchange heat with the working fluid, and then supplied to the consumer CS in the ship. That is, in the tenth embodiment and the system of the twelfth embodiment described later, a compressor 350 connected to the expansion turbine 300 via a shaft is provided. The compressor 350 uses shaft power to compress air to generate compressed air, and the compressed air compressed by the compressor 350 is supplied to the consumer CS in the ship. In addition, the heat of the compressed air discharged from the compressor 350 is recovered by the second recuperator 650b or 650d and used to preheat the working fluid.

[0154] In addition, the consumer CS within the ship to which the compressed air is supplied may be, for example, an air lubrication system that injects air onto the outside bottom surface of the ship's hull. The air lubrication system injects air onto the outside bottom surface of the hull to form a continuous air layer between the hull and seawater, thereby reducing frictional resistance between the hull and seawater during operation and improving the fuel efficiency of the ship.

[0155] The air lubrication system is also configured to include an air compressor (not shown) for generating compressed air to be injected outside the bottom surface of the hull, a pipe for supplying compressed air, an air injection unit (not shown), an air layer (not shown) formed on the surface of the outside bottom surface of the hull, a control unit (not shown), and the like. The compressed air generated in the waste heat recovery system can also be supplied to the air lubrication system. In the system of this embodiment, the shaft power generated by the expansion turbine 300 is used to compress air in the compressor, and the compressed air is supplied to the air lubrication system. In this way, since the compressor of the waste heat recovery system can be used instead of the air compressor of the air lubrication system, there is no need to separately provide an air compressor or the like in the air lubrication system. Even if an air compressor is provided in the air lubrication system, the capacity that is insufficient in the air compressor can be supplemented by the compressed air generated in the waste heat recovery system, so that an air compressor with a smaller capacity can be used. In addition, when compressed air is supplied to the air lubrication system, the compressor 350 is operated at a compression ratio of about 2. In this case, the compressor 350 can be configured as a single-stage (single-stage) centrifugal compressor.

[0156] As described above, the systems of the ninth and tenth embodiments recover waste heat from exhaust gas discharged from an engine using a low flash point fuel by using the heat medium circulation line RCL provided with the multiple recuperators 600, 650b and the vaporization unit 100 configured to recover waste heat in sequence according to the temperature of the exhaust gas. In addition, the recovered waste heat is converted into electricity or compressed air is generated and supplied to the consumer in the ship, thereby improving the energy efficiency of the ship.

[0157] 11 and 12 differ from the systems of the ninth and tenth embodiments in that a third recuperator 700 that recovers thermal energy from the liquid working fluid separated in the gas-liquid separator 200 and flowing through the liquid line LLc or LLd, and an exhaust heat heater 130 that is provided in the vaporizer 100 and recovers exhaust heat from low-temperature exhaust gas are additionally provided. Hereinafter, a description of the same configurations as those of the systems of the ninth and tenth embodiments will be omitted, and the following description will focus on the configurations that differ from those of the ninth and tenth embodiments.

[0158] As shown in FIG. 11 and FIG. 12, in the systems of the eleventh and twelfth embodiments, the heat medium circulation line RCL is provided with a third recuperator 700 for heating the working fluid preheated in the first or second recuperator 600, 650c, or 650d after being pressurized by the supply pump 500. The working fluid heated in the third recuperator 700 is supplied to the vaporizer 110. In the systems of the eleventh and twelfth embodiments, the working fluid pressurized by the supply pump 500 is branched into two flows and supplied to the first or second recuperator 600, 650c, or 650d, respectively. Then, the working fluid discharged from the first or second recuperator 600, 650c, or 650d and joined together is heated by heat exchange with the liquid working fluid separated in the gas-liquid separator 200 and flowing through the liquid line LLc or LLd.

[0159] By arranging the third recuperator 700 in this manner, thermal energy can be recovered from the working fluid that remains in a liquid state without being vaporized even when heated by the waste heat of the exhaust gas in the carburetor 110, and the working fluid discharged from the supply pump 500 and the first or second recuperator 600 or 650c or 650d can be preheated before being supplied to the carburetor 110.

[0160] In the systems of the eleventh and twelfth embodiments, the working fluid circulating through the heat medium circulation line RCL may be, for example, an aqueous ammonia solution. When the aqueous ammonia solution is heated by heat exchange with low-temperature exhaust gas in the vaporizer 110 of the vaporization unit 100, the ammonia having a low boiling point is vaporized into a gaseous state, but water may be in a liquid state without being vaporized. Then, the gaseous ammonia separated in the gas-liquid separator 200 is heated to a superheated state in the superheater 120 and supplied to the expansion turbine 300. On the other hand, the water separated in the gas-liquid separator 200 is supplied to the third recuperator 700 through the liquid line LLc or LLd, and after recovering thermal energy, is supplied to the downstream side of the expansion turbine 300 of the heat medium circulation line RCL, and is supplied to the first recuperator 600 together with the ammonia discharged from the expansion turbine 300, and is then supplied to the condenser 400.

[0161] In the systems of the eleventh and twelfth embodiments, the vaporizer 100 is further provided with an exhaust heat heater 130. In the exhaust heat heater 130, low-temperature exhaust gas supplied from the exhaust gas supply line HL to the superheater 120 and the vaporizer 110 and discharged from the vaporizer 110 is heat-exchanged with the working fluid. A part of the working fluid that has been pressurized by the supply pump 500 and then heat-exchanged in the first recuperator 600 is branched by the branch line RCLc or RCLd, heated by the low-temperature exhaust gas in the exhaust heat heater 130, and then supplied downstream of the third recuperator 700 of the heat medium circulation line RCL. That is, a part of the working fluid that has been pressurized by the supply pump 500 and then preheated in the first recuperator 600 is heated in the third recuperator 700 by the flow of the fluid in the liquid line LLc or LLd, and a part of the branched working fluid is heated in the exhaust heat heater 130 by the flow of the low-temperature exhaust gas. Then, these are joined downstream of the third recuperator 700 in the heat medium circulation line RCL, and are supplied to the vaporizer 110 of the vaporization section 100. This makes it possible to further improve the amount of waste heat recovered from the exhaust gas.

[0162] Also, like the system of the above-mentioned 10th embodiment, the system of the 12th embodiment is configured so that compressed air generated by the compressor 350 using shaft power is supplied to a second recuperator 650d through an air supply line AL and then supplied to a consumer CS in the ship, so that the heat of the compressed air discharged from the compressor 350 can be used to preheat the working fluid. Note that a description of the same configuration as that of the above-mentioned 11th embodiment will be omitted.

[0163] As described above, the system of this embodiment further improves the thermal efficiency of the ship by providing the third recuperator 700 and the exhaust heat heater 130, and can effectively recover the waste heat of the exhaust gas. In addition, by using an aqueous ammonia solution as the working fluid of the heat medium circulation line RCL, refilling and management of the working fluid becomes easy. In particular, when the system of this embodiment is applied to an ammonia-fuel propulsion ship or an ammonia carrier that uses ammonia as engine fuel, ammonia as fuel or cargo can be directly used as the working fluid of the heat medium circulation line RCL, so there is no need to separately install a refrigerant management system, and the installation costs of related equipment such as a refrigerant storage tank can be reduced.

[0164] The present invention is not limited to the above-described embodiment, and it will be obvious to those skilled in the art to which the present invention pertains that various changes or modifications can be made without departing from the technical gist of the present invention.

Claims

1. A heat medium circulation line provided in the ship through which a working fluid circulates; and a vaporizer provided in the heat medium circulation line and configured to vaporize the working fluid by heat exchange with exhaust gas discharged from an engine of the ship; and an expansion turbine provided in the heat medium circulation line and configured to expand the working fluid to generate shaft power; supplying the engine with a low flash point liquefied gas as fuel; The working fluid circulates through the heat medium circulation line and changes phase from liquid to gas using the exhaust gas as a heat source. A waste heat recovery system for marine exhaust gases.

2. The heat medium circulation line includes: a condenser that cools and condenses the working fluid that has been cooled by expansion in the expansion turbine; and a supply pump that pressurizes the working fluid condensed in the condenser and sends it to the vaporizer.

2. A marine exhaust gas waste heat recovery system according to claim 1.

3. A compressor that compresses air using shaft power generated by the expansion turbine; and an air supply line for supplying air to the compressor; 3. A marine exhaust gas waste heat recovery system according to claim 2.

4. The air compressed by the compressor is supplied to a consumer in the ship through the air supply line. The in-ship consumer is an air lubrication system that injects air onto the outside of the bottom of the ship during operation to reduce frictional resistance with seawater.

4. A marine exhaust gas waste heat recovery system according to claim 3.

5. A supercharger for supercharging scavenging air supplied to the engine; and A scavenging air supply line that cools the scavenging air compressed by the turbocharger and supplies the cooled scavenging air to the engine; and a branch line branching off from the scavenging air supply line and connected to the air supply line downstream of the compressor; and A branch valve provided in the branch line.

5. A marine exhaust gas waste heat recovery system according to claim 4.

6. when the pressure of the scavenging air compressed by the turbocharger is higher than the discharge pressure of the compressor and therefore the pressure of the scavenging air needs to be reduced, an opening degree of the branch valve is adjusted to supply a part of the scavenging air compressed by the turbocharger to a consumer in the ship.

6. A marine exhaust gas waste heat recovery system according to claim 5.

7. A heat medium circulation line provided in the ship through which a working fluid circulates; and a carburetor provided in the heat medium circulation line for heating the working fluid by heat exchange with exhaust gas discharged from an engine of the ship; and a gas-liquid separator provided in the heat medium circulation line for separating the working fluid heated by the evaporator into gas and liquid; and an expansion turbine for expanding the gaseous working fluid separated by the gas-liquid separator to generate shaft power; and a condenser that cools and condenses the working fluid that has been cooled by expansion in the expansion turbine; and a supply pump provided in the heat medium circulation line and configured to pressurize the working fluid condensed in the condenser; and a liquid line that supplies the liquid working fluid separated by the gas-liquid separator to a downstream side of the expansion turbine of the heat medium circulation line; The engine is supplied with a liquefied gas having a low flash point as fuel. A waste heat recovery system for marine exhaust gases.

8. The heat transfer medium circulation system further includes a recuperator that is provided in the heat transfer medium circulation line and heats the working fluid pressurized by the supply pump and supplies the working fluid to the evaporator. The working fluid circulates through the heat medium circulation line and changes phase from liquid to gas using the exhaust gas as a heat source.

8. A marine exhaust gas waste heat recovery system according to claim 7.

9. The recuperator is provided downstream of a junction of the heat medium circulation line with the liquid line, The recuperator heats the working fluid pressurized by the supply pump by heat exchange with the working fluid supplied to the condenser.

9. A marine exhaust gas waste heat recovery system according to claim 8.

10. The working fluid is a fluid having a boiling point lower than that of water.

10. A marine exhaust gas waste heat recovery system according to claim 9.

11. The recuperator heats the working fluid pressurized by the supply pump by heat exchange with the liquid working fluid separated by the gas-liquid separator and flowing through the liquid line.

9. A marine exhaust gas waste heat recovery system according to claim 8.

12. Compressing air in a compressor using shaft power generated by the expansion turbine, The air compressed by the compressor is supplied to a consumer in the ship; The on-board consumer is an air lubrication system that injects air onto the outside of the bottom of the ship during operation to reduce frictional resistance with seawater.

12. A marine exhaust gas waste heat recovery system according to claim 11.

13. A heat medium circulation line provided in the ship through which a working fluid circulates; and a carburetor provided in the heat medium circulation line for heating the working fluid by heat exchange with exhaust gas discharged from an engine of the ship; and a gas-liquid separator provided in the heat medium circulation line for separating the working fluid heated by the evaporator into gas and liquid; and an expansion turbine for expanding the gaseous working fluid separated by the gas-liquid separator to generate shaft power; and a condensation heat exchanger that cools and condenses the working fluid that has been cooled by expansion in the expansion turbine; and a supply pump provided in the heat medium circulation line for pressurizing the working fluid condensed in the condensing heat exchanger and sending the working fluid to the vaporizer; and a first cooling water supply line that supplies cooling water to the condensation heat exchanger for cooling the working fluid; supplying the engine with a low flash point liquefied gas as fuel; The condensation heat exchanger exchanges heat among three flows of the working fluid cooled by expansion in the expansion turbine, the working fluid pressurized by the supply pump, and the cooling water in the first cooling water supply line. A waste heat recovery system for marine exhaust gases.

14. a suction pot for additionally cooling the working fluid condensed in the condensing heat exchanger before supplying it to the supply pump; and a second cooling water supply line for supplying cooling water to the suction pot for cooling the working fluid; The working fluid additionally cooled by the suction pot is supplied to the supply pump to prevent cavitation at a suction portion of the supply pump.

14. A marine exhaust gas waste heat recovery system according to claim 13.

15. a liquid line that supplies the liquid working fluid separated by the gas-liquid separator to a downstream side of the expansion turbine of the heat medium circulation line; The liquid working fluid separated in the gas-liquid separator is supplied to the condensing heat exchanger through the liquid line together with the working fluid discharged from the expansion turbine.

15. A marine exhaust gas waste heat recovery system according to claim 14.

16. The working fluid is a fluid that circulates through the heat medium circulation line, changes phase from liquid to gas using the exhaust gas as a heat source, and has a boiling point lower than that of water.

16. A marine exhaust gas waste heat recovery system according to claim 15.

17. The present invention further comprises a recuperator provided in the heat medium circulation line, which heats the working fluid that has been pressurized by the supply pump and then heat-exchanged in the condensing heat exchanger and supplies the working fluid to the evaporator.

16. A marine exhaust gas waste heat recovery system according to claim 15.

18. In the recuperator, the working fluid pressurized by the supply pump and then heat-exchanged in the condensing heat exchanger is heated by heat exchange with the liquid-state working fluid separated in the gas-liquid separator and flowing through the liquid line.

18. A marine exhaust gas waste heat recovery system according to claim 17.

19. Compressing air in a compressor using shaft power generated by the expansion turbine, The air compressed by the compressor is supplied to a consumer in the ship; The on-board consumer is an air lubrication system that injects air onto the outside of the bottom of the ship during operation to reduce frictional resistance with seawater.

20. A marine exhaust gas waste heat recovery system according to claim 18.

20. A heat medium circulation line provided in the ship through which a working fluid circulates; and A vaporizer provided in the heat medium circulation line for exchanging heat between the working fluid and exhaust gas discharged from an engine of the ship that uses a liquefied gas having a low flash point as fuel; and an exhaust gas supply line for supplying exhaust gas to be heat exchanged with the working fluid to the vaporizer; and A gas-liquid separator provided in the heat medium circulation line for separating the working fluid heated in the vaporizer into gas and liquid; and an expansion turbine for expanding the gaseous working fluid separated by the gas-liquid separator to generate shaft power; and a condensation heat exchanger that cools and condenses the working fluid that has been cooled by expansion in the expansion turbine; and a supply pump provided in the heat medium circulation line to pressurize the working fluid condensed in the condensing heat exchanger and send the working fluid to the vaporization section; The vaporization unit includes a vaporizer and a superheater, which are provided in this order in a flow direction of the working fluid supplied from the supply pump, and the exhaust gas supplied from the exhaust gas supply line is supplied to the superheater and the vaporizer in this order; The working fluid that has been heat exchanged with the exhaust gas in the carburetor is separated into gas and liquid in the gas-liquid separator, and the separated gaseous working fluid is additionally heated in the superheater and supplied to the expansion turbine. A waste heat recovery system for marine exhaust gases.

21. a cooling water supply line for supplying cooling water to the condensation heat exchanger for cooling the working fluid; The condensation heat exchanger exchanges heat among three flows of the working fluid cooled by expansion in the expansion turbine, the working fluid pressurized by the supply pump, and the cooling water in the cooling water supply line.

21. A marine exhaust gas waste heat recovery system according to claim 20.

22. a liquid line that supplies the liquid working fluid separated by the gas-liquid separator to a downstream side of the expansion turbine of the heat medium circulation line; The liquid working fluid separated in the gas-liquid separator is supplied to the condensing heat exchanger through the liquid line together with the working fluid discharged from the expansion turbine.

22. A marine exhaust gas waste heat recovery system according to claim 21.

23. The working fluid is a fluid that circulates through the heat medium circulation line, changes phase from liquid to gas using exhaust gas discharged from the engine as a heat source, and has a boiling point lower than that of water.

23. A marine exhaust gas waste heat recovery system according to claim 22.

24. The present invention further comprises a recuperator provided in the heat medium circulation line, which heats the working fluid pressurized by the supply pump and heat-exchanged in the condensing heat exchanger and supplies the working fluid to the evaporator.

23. A marine exhaust gas waste heat recovery system according to claim 22.

25. In the recuperator, the working fluid pressurized by the supply pump and then heat-exchanged in the condensing heat exchanger is heated by heat exchange with the liquid-state working fluid separated in the gas-liquid separator and flowing through the liquid line.

25. A marine exhaust gas waste heat recovery system according to claim 24.

26. The vaporization unit further includes an exhaust heat heater that exchanges heat between the exhaust gas discharged from the vaporizer and the working fluid that has been pressurized by the supply pump and then heat exchanged in the condensation heat exchanger, The present invention is characterized in that the present invention further comprises a branch line that branches the working fluid that has been pressurized by the supply pump and then heat exchanged in the condensing heat exchanger and supplies it to the exhaust heat heater, and supplies the working fluid discharged from the exhaust heat heater to a downstream side of the recuperator of the heat medium circulation line.

26. A marine exhaust gas waste heat recovery system according to claim 25.

27. Compressing air in a compressor using shaft power generated by the expansion turbine, The air compressed by the compressor is supplied to a consumer in the ship; The on-board consumer is an air lubrication system that injects air onto the outside of the bottom of the ship during operation to reduce frictional resistance with seawater.

27. A marine exhaust gas waste heat recovery system according to claim 26.

28. A heat medium circulation line provided in the ship through which a working fluid circulates; and A vaporizer provided in the heat medium circulation line for exchanging heat between the working fluid and exhaust gas discharged from an engine of the ship that uses a liquefied gas having a low flash point as fuel; and A gas-liquid separator provided in the heat medium circulation line for separating the working fluid heated in the vaporizer into gas and liquid; and an expansion turbine for expanding the gaseous working fluid separated by the gas-liquid separator to generate shaft power; and a condenser that cools and condenses the working fluid that has been cooled by expansion in the expansion turbine; and a supply pump provided in the heat medium circulation line and configured to pressurize the working fluid condensed in the condenser; and a first recuperator that heats a portion of the working fluid pressurized by the supply pump and supplies the heated portion to the vaporizing section; and a second recuperator provided in parallel with the first recuperator, for heating another part of the working fluid pressurized by the supply pump and supplying the heated working fluid to the vaporizing section; In the first recuperator, heat is exchanged between the working fluid pressurized by the supply pump and the working fluid that is cooled by expansion in the expansion turbine and then supplied to the condenser, The second recuperator heats the working fluid pressurized by the supply pump using waste heat supplied from a compressor or a cooling device in the ship. A waste heat recovery system for marine exhaust gases.

29. The vaporization unit includes a vaporizer and a superheater that are provided in this order in the direction in which the working fluid supplied from the supply pump flows, and an exhaust gas supply line that supplies exhaust gas to be heat exchanged with the working fluid to the vaporizer and the superheater, and the exhaust gas is supplied from the exhaust gas supply line to the superheater and then to the vaporizer, The working fluid that has been heat exchanged with the exhaust gas in the carburetor is separated into gas and liquid in the gas-liquid separator, and the separated gaseous working fluid is additionally heated in the superheater and supplied to the expansion turbine.

29. A marine exhaust gas waste heat recovery system according to claim 28.

30. a cooling water supply line for supplying cooling water to the condenser for cooling the working fluid; and a liquid line that supplies the liquid working fluid separated by the gas-liquid separator to a downstream side of the expansion turbine of the heat medium circulation line; The liquid working fluid separated in the gas-liquid separator is supplied to the first recuperator through the liquid line together with the working fluid discharged from the expansion turbine, and then supplied to the condenser.

30. A marine exhaust gas waste heat recovery system according to claim 29.

31. A compressor that compresses air using shaft power generated by the expansion turbine; and an air supply line for supplying air to the compressor; The air compressed by the compressor is supplied to the second recuperator through the air supply line, and is heat exchanged with another part of the working fluid pressurized by the supply pump, and then is supplied to a consumer in the ship.

31. A marine exhaust gas waste heat recovery system according to claim 30.

32. The heat transfer medium circulation system further includes a third recuperator that is provided in the heat transfer medium circulation line and that heats the working fluid that has been pressurized by the supply pump and then heat-exchanged in the first or second recuperator and supplies the working fluid to the evaporator.

31. A marine exhaust gas waste heat recovery system according to claim 30.

33. In the third recuperator, the working fluid pressurized by the supply pump and then heat-exchanged in the first or second recuperator is heated by heat exchange with the liquid working fluid separated in the gas-liquid separator and flowing through a liquid line.

33. A marine exhaust gas waste heat recovery system according to claim 32.

34. The vaporization unit further includes an exhaust heat heater that exchanges heat between the exhaust gas discharged from the vaporizer and a working fluid that is pressurized by the supply pump and heat-exchanged in the first recuperator and then branched, The present invention further comprises a branch line that supplies the working fluid that has been heat exchanged in the exhaust heat heater to a downstream side of the third recuperator of the heat medium circulation line.

34. A marine exhaust gas waste heat recovery system according to claim 33.

35. A compressor that compresses air using shaft power generated by the expansion turbine; and an air supply line for supplying air to the compressor; The air compressed by the compressor is supplied to the second recuperator through the air supply line, and is heat exchanged with another part of the working fluid pressurized by the supply pump, and then is supplied to a consumer in the ship.

35. A marine exhaust gas waste heat recovery system according to claim 34.

36. The working fluid is an organic refrigerant or an aqueous ammonia solution. A marine exhaust gas waste heat recovery system according to any one of claims 1 to 35.

37. The low flash point liquefied gas contains at least one of LPG and ammonia.

37. A marine exhaust gas waste heat recovery system according to claim 36.

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