Waste heat recovery system

Abstract

This invention provides a waste heat recovery system that can recover thermal energy that cannot be recovered by the ORC cycle without compromising the efficiency of thermal energy recovery by the ORC cycle. [Solution] The waste heat recovery system comprises an exhaust gas line, an ORC cycle which includes a turbine and a first heat exchanger for recovering thermal energy from exhaust gas flowing through the exhaust gas line and which can heat a heat transfer medium with the thermal energy recovered by the first heat exchanger, an auxiliary boiler for generating steam to be supplied to a steam demander of a ship, which includes a second heat exchanger for recovering thermal energy from exhaust gas flowing upstream of the first heat exchanger in the exhaust gas line and which can generate steam with the thermal energy recovered by the second heat exchanger, a steam supply line for supplying steam discharged from the auxiliary boiler to a steam demander, a steam branch line branching off from the steam supply line, and a steam turbine which can be driven by the steam flowing through the steam branch line.

Description

Technical Field

[0001] The present disclosure relates to an exhaust heat recovery system configured to recover the thermal energy of exhaust gas discharged from an internal combustion engine mounted on a ship.

Background Art

[0002] Exhaust heat recovery systems are known that recover the thermal energy of exhaust gas discharged from an internal combustion engine (e.g., a marine main engine) by an ORC cycle (organic Rankine cycle) and a steam turbine (see, for example, Patent Document 1).

[0003] In the invention described in Patent Document 1, the ORC cycle recovers the thermal energy of the exhaust gas whose temperature has decreased after the thermal energy is recovered by the steam turbine.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, with the improvement of the fuel efficiency of internal combustion engines (marine main engines), the temperature of the exhaust gas discharged from the internal combustion engines has been decreasing. For this reason, in the invention described in Patent Document 1, there is a risk that it will be difficult to recover the thermal energy of the exhaust gas in the ORC cycle. Further, in the invention described in Patent Document 1, there is a problem that a trade-off occurs in the heat recovery between the steam turbine and the ORC cycle, that is, when the amount of thermal energy recovered by the steam turbine is increased, the amount of thermal energy that can be recovered by the ORC cycle decreases.

[0006] In view of the circumstances described above, at least one embodiment of this disclosure aims to provide a waste heat recovery system capable of recovering thermal energy that cannot be recovered by the ORC cycle without impairing the efficiency of thermal energy recovery by the ORC cycle. [Means for solving the problem]

[0007] A heat recovery system according to at least one embodiment of this disclosure is A waste heat recovery system configured to recover the thermal energy of exhaust gases emitted from an internal combustion engine installed on a ship, An exhaust gas line for guiding exhaust gas discharged from the internal combustion engine, An ORC cycle comprising a turbine configured to be driven by a heat transfer medium having a lower boiling point than water, wherein the ORC cycle comprises a first heat exchanger configured to recover the thermal energy of the exhaust gas flowing through the exhaust gas line, and the ORC cycle is configured to heat the heat transfer medium with the thermal energy of the exhaust gas recovered by the first heat exchanger, An auxiliary boiler for generating steam to be supplied to the steam demander of the aforementioned vessel, wherein the auxiliary boiler includes a second heat exchanger configured to recover thermal energy from the exhaust gas flowing upstream of the first heat exchanger in the exhaust gas line, and the auxiliary boiler is configured to generate the steam using the thermal energy of the exhaust gas recovered by the second heat exchanger, A steam supply line for supplying the steam discharged from the auxiliary boiler to the steam demanding party, A steam branch line that branches off from the aforementioned steam supply line, The system comprises a steam turbine configured to be driven by the steam flowing through the steam branch line. [Effects of the Invention]

[0008] According to at least one embodiment of the present disclosure, a waste heat recovery system is provided that can recover thermal energy that cannot be recovered by the ORC cycle without impairing the efficiency of thermal energy recovery by the ORC cycle. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of a ship equipped with a waste heat recovery system according to one embodiment of the present disclosure. [Figure 2] This is a schematic diagram of a ship equipped with a waste heat recovery system according to one embodiment of the present disclosure. [Figure 3] This is a schematic cross-sectional view along the axis of a steam turbine in a waste heat recovery system according to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0010] Hereinafter, several embodiments of this disclosure will be described with reference to the attached drawings. However, the dimensions, materials, shapes, relative arrangements, etc., of the components described or shown in the drawings as embodiments are not intended to limit the scope of this disclosure, but are merely illustrative examples.

[0011] (Waste heat recovery system) Figures 1 and 2 are schematic diagrams of a ship 10 equipped with a waste heat recovery system 1 according to one embodiment of the present disclosure. The waste heat recovery system 1 according to several embodiments is configured to recover the thermal energy of exhaust gas discharged from an internal combustion engine 11 installed on the ship 10. The waste heat recovery system 1 is installed on the ship 10.

[0012] The vessel 10 is a structure that can float on water and is configured to be self-propelled by driving a main engine. The main engine is configured to generate a driving force (thrust force) that drives a thruster (propeller in the illustrated example) 12 mechanically connected to the drive shaft of the main engine using the energy of the fuel supplied to the main engine.

[0013] The internal combustion engine 11 may be configured to operate using only one of either oil fuel (liquid fuel) or gas fuel (gaseous fuel), or it may be configured to operate using both oil fuel (liquid fuel) and gas fuel (gaseous fuel). In the illustrated embodiment, the internal combustion engine 11 is the main engine of the ship 10. In other embodiments, the internal combustion engine 11 may be an engine other than the main engine of the ship 10 (for example, an auxiliary engine of the ship 10).

[0014] As shown in Figures 1 and 2, the exhaust heat recovery system 1 comprises an exhaust gas line 2 for guiding exhaust gas discharged from an internal combustion engine 11, an ORC cycle (Organic Rankine cycle) 3 including a first heat exchanger 31, and an auxiliary boiler 5 including a second heat exchanger 51. The first heat exchanger 31 and the second heat exchanger 51 are configured to recover the thermal energy of the exhaust gas flowing through the exhaust gas line 2. The second heat exchanger 51 is located upstream of the first heat exchanger 31 in the exhaust gas line 2. The second heat exchanger 51 is configured to recover the thermal energy of the exhaust gas flowing upstream of the first heat exchanger 31 in the exhaust gas line 2. The exhaust gas from which thermal energy has been recovered in the second heat exchanger 51 is guided into the first heat exchanger 31.

[0015] In the embodiments shown in Figures 1 and 2, the exhaust heat recovery system 1 includes a supercharger 13. The supercharger 13 includes an exhaust gas turbine 14 located upstream of the second heat exchanger 51 in the exhaust gas flow direction of the exhaust gas line 2, and a compressor 15 located coaxially with the exhaust gas turbine 14. The exhaust gas turbine 14 is configured to recover the energy of the exhaust gas flowing through the exhaust gas line 2. The compressor 15 is configured to rotate using the energy recovered by the exhaust gas turbine 14, thereby compressing a fluid (for example, air used for combustion in the internal combustion engine 11) that is directed to the compressor 15.

[0016] (ORC cycle) As shown in FIGS. 1 and 2, the ORC cycle 3 includes a heat medium circulation cycle 40 that circulates a heat medium having a boiling point lower than that of water, a heater 41 configured to heat the heat medium by the thermal energy recovered from the exhaust gas in the first heat exchanger 31, and a turbine 42 configured to be driven by the heat medium heated in the heater 41. In the embodiments shown in FIGS. 1 and 2, the heater 41 is an evaporator configured to vaporize the heat medium by the thermal energy recovered from the exhaust gas in the first heat exchanger 31. The turbine 42 is an expansion turbine configured to be driven by the heat medium vaporized in the heater 41 (evaporator).

[0017] (Heat medium circulation cycle) As the heat medium circulating in the heat medium circulation cycle 40, low molecular weight hydrocarbons such as isopentane, butane, and propane, or R134a, R245fa, R1233zd, etc. used as refrigerants can be used. As shown in FIGS. 1 and 2, the heat medium circulation cycle 40 includes a first heat medium line 43 that forms a flow path for guiding the heat medium from the heater 41 to the turbine 42, and a second heat medium line 44 that forms a flow path for guiding the heat medium from the turbine 42 to the heater 41. The heat medium vaporized in the heater 41 is guided to the turbine 42 through the first heat medium line 43.

[0018] The heat medium circulation cycle 40 includes a condenser (cooler) 45 configured to liquefy (cool) the gaseous heat medium, and a heat medium circulation pump 46 for sending the liquid-phase heat medium. The heat medium circulation pump 46 is configured to compress the liquid-phase heat medium. Hereinafter, the upstream side in the flow direction of the heat medium in the heat medium circulation cycle 40 is simply referred to as the upstream side, and the downstream side in the flow direction of the heat medium in the heat medium circulation cycle 40 is simply referred to as the downstream side. The condenser 45 is provided in the second heat medium line 44. The heat medium circulation pump 46 is provided on the downstream side (heater 41 side) of the condenser 45 in the second heat medium line 44.

[0019] The heat medium circulation pump 46 is configured to send the liquid-phase heat medium to the downstream side of the heat medium circulation pump 46 in the second heat medium line 44. By driving the heat medium circulation pump 46, the heat medium circulates through the second heat medium line 44 and the first heat medium line 43. The heater 41 is guided with the liquid-phase heat medium compressed by the heat medium circulation pump 46 through the second heat medium line 44. The turbine 42 is guided with the heat medium vaporized by the heat exchange in the heater 41.

[0020] The turbine 42 is configured to rotate by the energy of the heat medium vaporized in the heater 41. The heat medium circulation cycle 40 is configured to recover the rotational force of the turbine 42 as power. In the illustrated embodiment, the heat medium circulation cycle 40 includes a generator 47. The generator 47 is mechanically connected to the drive shaft of the turbine 42 and is configured to convert the rotational force of the turbine 42 into electric power. In some other embodiments, the heat medium circulation cycle 40 may recover the rotational force of the turbine 42 as power as it is by a power transmission device (for example, a coupling, a belt, a pulley, etc.) instead of converting it into electric power.

[0021] The condenser 45 is guided with the heat medium that has passed through the turbine 42. The condenser 45 is configured to perform heat exchange between the heat medium guided to the condenser 45 and the cooling water introduced into the condenser 45 from the outside of the heat medium circulation cycle 40. By the heat exchange in the condenser 45, the heat medium is cooled and condensed.

[0022] The cooling water introduced into the condenser 45 may be water that can cool the heat medium that is the heat exchange target as a refrigerant in the condenser 45 (water at a lower temperature than the heat medium), but it is preferably the outside water that is easily recovered by the waste heat recovery system 1 mounted on the ship 10. The outside water means the water in the water area (for example, the sea area) where the ship 10 sails and includes seawater, river water, lake water, etc.

[0023] In the embodiments shown in Figures 1 and 2, the ORC cycle 3 includes a hot water circulation cycle 30 that circulates hot water (feedwater) heated in the first heat exchanger 31. The first heat exchanger 31 is configured to perform heat exchange between exhaust gas flowing through the exhaust gas line 2 and circulating water flowing through the hot water circulation cycle 30. The exhaust gas introduced into the first heat exchanger 31 is at a higher temperature than the circulating water introduced into the first heat exchanger 31. Through heat exchange between the exhaust gas and circulating water in the first heat exchanger 31, the thermal energy of the exhaust gas is transferred to the circulating water. Through heat exchange in the first heat exchanger 31, the exhaust gas is cooled and the circulating water is heated.

[0024] (Hot water circulation cycle) The hot water circulation cycle 30, as shown in Figures 1 and 2, includes a hot water pump 32 for supplying hot water flowing through the hot water circulation cycle 30, a first hot water line 33 forming a flow path for guiding hot water (circulating water) from the first heat exchanger 31 to the heater 41, and a second hot water line 34 forming a flow path for guiding hot water from the heater 41 to the first heat exchanger 31. The hot water pump 32 is configured to pressurize the hot water flowing through the hot water circulation cycle 30. In the illustrated embodiment, the hot water pump 32 is located in the second hot water line 34. By driving the hot water pump 32, hot water circulates through the first hot water line 33 and the second hot water line 34. Hereinafter, the upstream side in the direction of hot water flow in the hot water circulation cycle 30 will be simply referred to as the upstream side, and the downstream side in the direction of hot water flow in the hot water circulation cycle 30 will be simply referred to as the downstream side.

[0025] In the illustrated embodiment, the hot water circulation cycle 30 includes a bypass line 35 for directing hot water from the first hot water line 33 to the second hot water line 34, bypassing the heater 41, as shown in Figures 1 and 2. One end of the bypass line 35 is connected to the first hot water line 33, and the other end of the bypass line 35 is connected upstream of the hot water pump 32 (towards the heater 41) in the direction of hot water flow in the second hot water line 34.

[0026] In the illustrated embodiment, the hot water circulation cycle 30 includes a flow control valve 36 provided in the bypass line 35 and configured to adjust the flow rate of hot water flowing through the bypass line 35, and a flow control valve 37 provided downstream of the connection between the first hot water line 33 and the bypass line 35 and configured to adjust the flow rate of hot water led to the heater 41. The hot water circulation cycle 30 may also include a three-way valve provided at the upstream end of the bypass line 35 instead of the flow control valves 36 and 37.

[0027] (heater) The heater 41 is configured to perform heat exchange between the hot water flowing in the hot water circulation cycle 30 and the heat transfer medium flowing in the heat transfer medium circulation cycle 40. The hot water introduced to the heater 41 is at a higher temperature than the heat transfer medium introduced to the heater 41. Through heat exchange between the hot water and the heat transfer medium in the heater 41, the thermal energy of the hot water is transferred to the heat transfer medium. Through heat exchange in the heater 41, the hot water is cooled and the heat transfer medium is heated and vaporized. The hot water cooled in the heater 41 is introduced to the first heat exchanger 31 through the second hot water line 34.

[0028] In some other embodiments, the ORC cycle 3 does not include the hot water circulation cycle 30 described above. In this case, the first heat exchanger 31 is the same device as the heater 41 and functions as a heater 41. The first heat exchanger 31 is configured to perform heat exchange between the exhaust gas flowing through the exhaust gas line 2 and the heat transfer medium flowing through the heat transfer medium circulation cycle 40.

[0029] (Auxiliary boiler) The auxiliary boiler 5 is configured to generate steam to be supplied to the steam demanders 61 of the ship 10 using the thermal energy of the exhaust gas recovered by the second heat exchanger 51. Examples of steam demanders 61 include equipment and devices that use steam installed on the ship 10 (for example, steam heaters).

[0030] In the embodiments shown in Figures 1 and 2, the auxiliary boiler 5 includes a boiler body 52 configured to store feedwater, a boiler furnace 53 that heats and vaporizes the boiler feedwater introduced into the boiler body 52 by burning fuel, a first boiler feedwater line 54 that forms a flow path for introducing boiler feedwater from the boiler body 52 to the second heat exchanger 51, a second boiler feedwater line 55 that forms a flow path for returning the boiler feedwater (which may contain steam) heated in the second heat exchanger 51 back to the boiler body 52, and a boiler-side pump 56 for supplying boiler feedwater.

[0031] In the illustrated embodiment, the boiler-side pump 56 is installed in the first boiler feedwater line 54. By driving the boiler-side pump 56, the boiler feedwater circulates through the boiler body 52, the first boiler feedwater line 54, the second heat exchanger 51, and the second boiler feedwater line 55.

[0032] The second heat exchanger 51 is configured to exchange heat between the exhaust gas flowing upstream of the first heat exchanger 31 in the exhaust gas line 2 (towards the internal combustion engine 11) and the boiler feedwater led to the second heat exchanger 51. If the temperature of the exhaust gas in the second heat exchanger 51 is higher than that of the boiler feedwater, the thermal energy of the exhaust gas is recovered into the boiler feedwater.

[0033] The waste heat recovery system 1 may have a feedwater supply system that supplies feedwater to the boiler body 52. ​​In the illustrated embodiment, the waste heat recovery system 1 includes a feedwater tank 57 configured to store feedwater, a feedwater supply line 58 that forms a flow path for guiding feedwater from the feedwater tank 57 to the boiler body 52, a feedwater supply pump 59 provided on the feedwater supply line 58, and a flow control valve 50 provided on the feedwater supply line 58 that can adjust the flow rate of feedwater flowing through the feedwater supply line 58. By driving the feedwater supply pump 59, the feedwater stored in the feedwater tank 57 is guided to the boiler body 52 through the feedwater supply line 58. Drain water may be guided to the feedwater tank 57 from both inside and outside the waste heat recovery system 1.

[0034] As shown in Figures 1 and 2, some embodiments of the waste heat recovery system 1 include a steam supply line 6 for supplying steam discharged from an auxiliary boiler 5 (steam from vaporized feedwater in the boiler body 52) to a steam demand unit 61, a steam branch line 7 branching off from the steam supply line 6, and a steam turbine 9 configured to be driven by the steam flowing through the steam branch line 7.

[0035] The upstream end of the steam supply line 6 is connected to the gas phase of the boiler body 52, and the downstream end of the steam supply line 6 is connected to the steam demand unit 61. In the illustrated embodiment, the upstream end 71 of the steam branch line 7 is connected upstream of the steam demand unit 61 of the steam supply line 6, and the downstream end 72 of the steam branch line 7 is connected to a gas-liquid-water separator 73 having a stationary structure for separating gas and liquid.

[0036] The steam turbine 9 is configured to rotate using the energy of steam introduced through the steam branch line 7. The waste heat recovery system 1 is configured to recover the rotational force of the steam turbine 9 as power. In the illustrated embodiment, the steam turbine 9 includes a generator 90. The generator 90 is mechanically connected to the drive shaft of the steam turbine 9 and is configured to convert the rotational force of the steam turbine 9 into electricity. In some other embodiments, the waste heat recovery system 1 may recover the rotational force of the steam turbine 9 directly as power through a power transmission device (e.g., a coupling, belt, pulley, etc.) instead of converting it into electricity.

[0037] ORC cycle 3 cannot recover thermal energy exceeding the thermal energy recovery capacity of ORC cycle 3 (heat transfer medium circulation cycle 40). In other words, even with the turbine 42 output at maximum, the waste heat recovery system 1 may not be able to recover all the thermal energy of the exhaust gas flowing through the exhaust gas line 2 in ORC cycle 3. For example, in a waste heat recovery system 1 that uses outboard water as the refrigerant in the condenser 45, if the temperature of the outboard water in the area where the ship 10 is navigating is relatively low, the heat drop of ORC cycle 3 (heat transfer medium circulation cycle 40) increases compared to when the temperature of the outboard water is relatively high, and the amount of thermal energy recovered increases. If the temperature of the outboard water in the area where the ship 10 is navigating is relatively low, the thermal energy recovery capacity of ORC cycle 3 (heat transfer medium circulation cycle 40) may be exceeded.

[0038] In this embodiment, the waste heat recovery system 1 generates steam by recovering excess thermal energy that exceeds the thermal energy recovery capacity of the ORC cycle 3 (heat medium circulation cycle 40) in the second heat exchanger 51 of the auxiliary boiler 5. Of the steam discharged from the auxiliary boiler 5, the thermal energy of the excess steam that satisfies the steam demand of the steam demand unit 61 can be recovered by the steam turbine 9. Therefore, the waste heat recovery system 1 in this embodiment can recover thermal energy that cannot be recovered by the ORC cycle 3 without impairing the thermal energy recovery efficiency of the ORC cycle 3.

[0039] In some embodiments of the waste heat recovery system 1, as shown in Figures 1 and 2, the ORC cycle 3 described above includes the hot water circulation cycle 30 described above for circulating hot water heated in the first heat exchanger 31, the heat transfer medium circulation cycle 40 described above for circulating the heat transfer medium, and the heater 41 described above which is configured to heat the heat transfer medium with thermal energy recovered from the hot water flowing through the hot water circulation cycle 30.

[0040] In the waste heat recovery system 1 according to this embodiment, the first heat exchanger 31 and the heat transfer medium circulation cycle 40 transfer thermal energy via the hot water circulation cycle 30, thereby suppressing rapid increases and decreases in the amount of thermal energy introduced into the ORC cycle 3, and consequently enabling stable operation of the ORC cycle 3.

[0041] In some embodiments of the waste heat recovery system 1, as shown in Figure 2, a separator 38 is provided to separate the hot water flowing in the first hot water line 33 described above, that is, downstream of the first heat exchanger 31 and upstream of the heater 41 in the hot water circulation cycle 30, into a gas phase and a liquid phase. As shown in Figure 2, the separator 38 is provided upstream of the branching point where the steam branch line 7 of the steam supply line 6 branches off (not shown), or upstream of the steam turbine 9 of the steam branch line 7 (illustrated example).

[0042] The separator 38 has a stationary structure that separates the hot water introduced into the separator 38 into a gas phase and a liquid phase. The hot water introduced into the separator 38 is separated into a gas phase and a liquid phase. By driving the hot water pump 32, the liquid phase of the hot water is drawn out from inside the separator 38 to the downstream side of the separator 38 in the first hot water line 33.

[0043] Inside the separator 38, heat exchange takes place between the steam flowing upstream of the branching point where the steam branch line 7 of the steam supply line 6 branches off, or upstream of the steam turbine 9 of the steam branch line 7, and the hot water or steam introduced into the separator 38.

[0044] In the waste heat recovery system 1 according to this embodiment, the hot water flowing through the hot water circulation cycle 30 may be heated by excess thermal energy that exceeds the thermal energy recovery capacity of the ORC cycle 3. The separator 38 can recover the excess thermal energy in the hot water circulation cycle 30 into the steam flowing upstream of the branching point where the steam branch line 7 of the steam supply line 6 branches, or upstream of the steam turbine 9 of the steam branch line 7. Therefore, the waste heat recovery system 1 according to this embodiment can recover thermal energy that cannot be recovered by the ORC cycle 3 without impairing the thermal energy recovery efficiency of the ORC cycle 3.

[0045] In some embodiments of the waste heat recovery system 1, as shown in Figure 2, a steam flow rate adjustment device 39 is provided which is configured to increase the flow rate of steam led from the separator 38 to the steam turbine 9 when the pressure inside the separator 38 exceeds a predetermined value.

[0046] In the embodiment shown in Figure 2, the steam flow rate adjustment device 39 includes a pressure regulating valve 391 provided downstream of the separator 38 in the line where the separator 38 is provided (steam branch line 7 in the illustrated example), a pressure acquisition device (pressure sensor in the illustrated example) 392 configured to acquire (measure) the pressure inside the separator 38, and an opening degree indicator device (controller in the illustrated example) 393 that instructs the pressure regulating valve 391 to open to a degree corresponding to the pressure inside the separator 38 acquired by the pressure acquisition device 392. The pressure regulating valve 391 may be configured to open and close according to the pressure of the steam introduced into the pressure regulating valve 391, and to open the valve when it exceeds the above predetermined value. In this case, the steam flow rate adjustment device 39 does not need to include the pressure acquisition device 392 and the opening degree indicator device 393.

[0047] If the pressure inside the separator 38 exceeds a predetermined value, there is excess thermal energy in the hot water circulation cycle 30. In this case, the steam flow rate adjustment device 39 increases the flow rate of steam guided from the separator 38 to the steam turbine 9, allowing the excess thermal energy in the hot water circulation cycle 30 to be quickly recovered by the steam turbine 9.

[0048] In some embodiments of the waste heat recovery system 1, as shown in Figures 1 and 2, a steam dump valve 74 is provided in parallel with the steam turbine 9 in the steam branch line 7 described above.

[0049] In the embodiments shown in Figures 1 and 2, the steam branch line 7 branches into a first steam line 75 equipped with a steam turbine 9 and a second steam line 76 equipped with a steam dump valve 74, with the first steam line 75 downstream of the steam turbine 9 and the second steam line 76 downstream of the steam dump valve 74 merging.

[0050] For example, when there is no demand for the power generated by the steam turbine 9, or when the steam turbine 9 is shut down for maintenance or in the event of a malfunction, the steam flowing through the steam branch line 7 can be directed to the steam dump valve 74. By directing the excess steam flowing through the steam branch line 7 to the steam dump valve 74, the excess steam can be discharged.

[0051] (Specific examples of steam turbines) Figure 3 is a schematic cross-sectional view along the axis LA of a steam turbine 9 in a heat recovery system 1 according to one embodiment of the present disclosure. Note that the steam turbine 9 shown in Figure 3 is an example of a steam turbine 9 mounted in the heat recovery system 1, and the steam turbine 9 mounted in the heat recovery system 1 is not limited to the illustrated example.

[0052] In some embodiments of the waste heat recovery system 1, as shown in Figure 3, the steam turbine 9 described above includes a rotating shaft 91 extending along the axis LA of the rotating shaft 91, and a one-sided turbine wheel 92 attached to one side in the direction of extension of the rotating shaft 91. A turbine wheel 93 attached to the other side in the extending direction of the rotating shaft 91, The system includes a rotating shaft 91, a turbine casing 94 configured to house one turbine wheel 92 and the other turbine wheel 93.

[0053] Hereinafter, the direction in which the axis LA of the rotating shaft 91 extends will be defined as the axial direction of the rotating shaft 91 (steam turbine 9), the direction perpendicular to the axis LA will be defined as the radial direction of the rotating shaft 91 (steam turbine 9), and the circumferential direction around the axis LA will be defined as the circumferential direction of the rotating shaft 91 (steam turbine 9).

[0054] The turbine wheel 92 on one side and the turbine wheel 93 on the other side are configured to guide steam introduced from the radially outer side of the rotating shaft 91 along the axial direction of the rotating shaft 91. The turbine wheel 92 on one side and the turbine wheel 93 on the other side are positioned so that their back surfaces face each other.

[0055] As shown in Figure 3, the steam branch line 7 includes a first steam introduction line 77 for leading steam to one side turbine wheel 92, and a second steam introduction line 78 for leading steam to the other side turbine wheel 93, the second steam introduction line 78 branching off from the first steam introduction line 77.

[0056] In the steam turbine 9 according to this embodiment, the steam introduced to one side turbine wheel 92 via the first steam introduction line 77 has a temperature and pressure similar to that of the steam introduced to the other side turbine wheel 93 via the second steam introduction line 78 branching off from the first steam introduction line 77. As a result, the thrust load TL1 directed toward the other side of the rotating shaft 91 caused by the rotation of one side turbine wheel 92 and the thrust load TL2 directed toward the one side of the rotating shaft 91 caused by the rotation of the other side turbine wheel 93 are balanced. As a result, these thrust loads TL1 and TL2 cancel each other out, making it possible to reduce the thrust load acting on the rotating shaft 91 of the steam turbine 9.

[0057] In some embodiments of the waste heat recovery system 1, as shown in Figure 3, a generator 90 is provided. The generator 90 includes a rotor 901 (e.g., permanent magnets) mounted on a rotating shaft 91 between one turbine wheel 92 and the other turbine wheel 93, and a stator 902 (e.g., stationary coils) positioned on the outer circumference of the rotor 901.

[0058] The steam turbine 9 described above includes, as shown in Figure 3, at least one one-side gas bearing 95 and at least one other-side gas bearing 96. The at least one one-side gas bearing 95 is configured to rotatably support the rotating shaft 91 between the axial one-side turbine wheel 92 and the rotor 901 of the rotating shaft 91. The at least one other-side gas bearing 96 is positioned between the axial other-side turbine wheel 93 and the rotor 901 of the rotating shaft 91 and is configured to rotatably support the rotating shaft 91. In the illustrated embodiment, the one-side gas bearing 95 and the other-side gas bearing 96 include journal bearings for supporting radial loads of the rotating shaft 91. The one-side gas bearing 95 further includes a thrust bearing for supporting thrust loads of the rotating shaft 91. The other-side gas bearing 96 may include both a journal bearing and a thrust bearing.

[0059] In the steam turbine 9 according to this embodiment, the bearings 95 and 96 that rotatably support the rotating shaft 91 of the steam turbine 9 are gas bearings, thereby enabling an oil-free operation. By eliminating the oil, the steam turbine 9 can improve its heat resistance because it eliminates problems such as thermal degradation of the lubricating oil supplied to the bearings.

[0060] In some embodiments of the waste heat recovery system 1, as shown in Figure 3, the steam turbine 9 described above includes a pair of one-sided non-contact seals 101, 102, a pair of other-sided non-contact seals 103, 104, at least one (multiple in the illustrated example) cooling gas introduction line 105, a gas discharge line 108, and a suction device 109.

[0061] The pair of one-sided non-contact seal portions 101 and 102 are non-contact seals that seal the space between the rotating shaft 91 and the turbine casing 94 between the one-sided turbine wheel 92 and the one-sided gas bearing 95 axially adjacent to the one-sided turbine wheel 92. In the illustrated embodiment, the pair of one-sided non-contact seal portions 101 and 102 are narrow portions where the radial clearance between the rotating shaft 91 and the turbine casing 94 is smaller than the surrounding area. Labyrinth seals may be formed on the pair of one-sided non-contact seal portions 101 and 102.

[0062] The pair of other-side non-contact seal portions 103 and 104 are non-contact seals that seal the space between the rotating shaft 91 and the turbine casing 94 between the other-side turbine wheel 93 and the other-side gas bearing 96 which is axially adjacent to the other-side turbine wheel 93. In the illustrated embodiment, the pair of other-side non-contact seal portions 103 and 104 are narrow portions in which the radial clearance between the rotating shaft 91 and the turbine casing 94 is smaller than that of the surrounding area. Labyrinth seals may be formed on the pair of other-side non-contact seal portions 103 and 104.

[0063] At least one cooling gas introduction line 105 forms a flow path for introducing cooling gas into the radial gap 97 formed between the rotating shaft 91 and the turbine casing 94, on the other side of each of the pair of one-sided non-contact seal portions 101, 102, and on the other side of each of the pair of other-sided non-contact seal portions 103, 104. A portion of the cooling gas introduction line 105 is formed inside the turbine casing 94.

[0064] The cooling gas can be any gas capable of cooling the bearings 95, 96 and the generator 90, but air, nitrogen gas, oxygen gas, etc., which have relatively little effect on the steam when mixed with it, are preferred. The upstream end of the cooling gas introduction line 105 may be connected to a gas tank (not shown) for storing the cooling gas, or, if the cooling gas is air, it may be open to the atmosphere.

[0065] The gas discharge line 108 forms a flow path for discharging gas from a one-side seal space 106 formed between a pair of one-side non-contact seal portions 101 and 102, and a other-side seal space 107 formed between a pair of other-side non-contact seal portions 103 and 104. A portion of the gas discharge line 108 is formed inside the turbine casing 94. The one-side seal space 106 is a radial gap formed between the rotating shaft 91 and the turbine casing 94, and is a radial gap larger than the pair of one-side non-contact seal portions 101 and 102. The other-side seal space 107 is a radial gap formed between the rotating shaft 91 and the turbine casing 94, and is a radial gap larger than the pair of other-side non-contact seal portions 103 and 104.

[0066] A suction device 109 (for example, a vacuum pump) is provided in the gas discharge line 108 and is configured to suck gas from the one-side seal space 106 and the other-side seal space 107, respectively. In the embodiment shown in Figure 3, the gas discharge line 108 includes a one-side gas discharge line 108A for discharging gas from the one-side seal space 106, and a other-side gas discharge line 108B for discharging gas from the other-side seal space 107, which merges with the one-side gas discharge line 108A. The suction device 109 is provided downstream of the confluence where the one-side gas discharge line 108A and the other-side gas discharge line 108B merge.

[0067] In the steam turbine 9, cooling gas introduced into the radial gap 97 via the cooling gas introduction line 105 may enter the one-side seal space 106 and the other-side seal space 107. The suction device 109 draws gas from the one-side seal space 106 and the other-side seal space 107 to the gas discharge line 108, thereby suppressing the flow of cooling gas into the steam used to rotate the one-side turbine wheel 92 and the steam used to rotate the other-side turbine wheel 93.

[0068] Furthermore, steam may enter the one-side seal space 106 from the space facing the back of the one-side turbine wheel 92. Also, steam may enter the other-side seal space 107 from the space facing the back of the other-side turbine wheel 93. The suction device 109 may suck in steam together with the cooling gas. In some other embodiments, the suction device 109 may not be provided in the gas discharge line 108, and the downstream end of the gas discharge line 108 may be open to the atmosphere.

[0069] In this specification, expressions describing relative or absolute arrangements such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" shall not only describe such arrangements strictly, but also describe states of relative displacement with tolerances or angles or distances that allow for the same function to be achieved. For example, expressions such as "identical," "equal," and "homogeneous" that describe things being in an equal state not only describe a state of being strictly equal, but also describe a state in which there is a tolerance or a difference that is sufficient to achieve the same function. Furthermore, in this specification, expressions describing shapes such as quadrilaterals and cylindrical shapes shall not only represent geometrically precise quadrilaterals and cylindrical shapes, but also shapes that include uneven surfaces, chamfered surfaces, etc., to the extent that the same effect can be achieved. Furthermore, in this specification, the expressions “equipment,” “includes,” or “possess” of a component are not exclusive expressions that exclude the existence of other components.

[0070] This disclosure is not limited to the embodiments described above, but also includes modified forms of the embodiments described above, as well as forms that combine these forms as appropriate.

[0071] The contents described in some of the embodiments above can be understood, for example, as follows:

[0072] [1] A heat recovery system (1) according to at least one embodiment of the present disclosure is A waste heat recovery system (1) configured to recover the thermal energy of exhaust gas emitted from an internal combustion engine (11) installed on a ship (10), An exhaust gas line (2) for guiding the exhaust gas discharged from the internal combustion engine (11), An ORC cycle (3) comprising a turbine (42) configured to be driven by a heat transfer medium having a lower boiling point than water, wherein the ORC cycle (3) comprises a first heat exchanger (31) configured to recover the thermal energy of the exhaust gas flowing through the exhaust gas line (2), and the ORC cycle (3) is configured to heat the heat transfer medium with the thermal energy of the exhaust gas recovered by the first heat exchanger (31), An auxiliary boiler (5) for generating steam to be supplied to a steam demander (13) of the ship (10), wherein the auxiliary boiler (5) includes a second heat exchanger (51) configured to recover thermal energy from the exhaust gas flowing upstream of the first heat exchanger (32) in the exhaust gas line (2), and the auxiliary boiler (5) is configured to generate steam using the thermal energy of the exhaust gas recovered by the second heat exchanger (51), A steam supply line (6) for supplying the steam discharged from the auxiliary boiler (5) to the steam demander (13), A steam branch line (7) branches off from the steam supply line (6), The system includes a steam turbine (9) configured to be driven by the steam flowing through the steam branch line (7).

[0073] According to the configuration described in [1] above, the waste heat recovery system (1) according to this embodiment can generate steam by recovering excess thermal energy that exceeds the thermal energy recovery capacity of the ORC cycle (3) in the second heat exchanger (51) of the auxiliary boiler (5). Then, the thermal energy of the steam discharged from the auxiliary boiler (5) that has not satisfied the steam demand of the steam demander (61) can be recovered by the steam turbine (9). Therefore, the waste heat recovery system (1) according to this embodiment can recover thermal energy that cannot be recovered by the ORC cycle (3) without impairing the thermal energy recovery efficiency of the ORC cycle (3).

[0074] [2] In some embodiments, the exhaust heat recovery system (1) described in [1] above, The aforementioned ORC cycle (3) is A hot water circulation cycle (30) that circulates the hot water heated in the first heat exchanger (31), A heat transfer medium circulation cycle (40) that circulates the aforementioned heat transfer medium, The system includes a heater (41) configured to heat the heat transfer medium with thermal energy recovered from the hot water flowing through the hot water circulation cycle (30).

[0075] According to the configuration described in [2] above, the ORC cycle (3) can suppress rapid increases and decreases in the amount of thermal energy introduced into the ORC cycle (3) by having the first heat exchanger (31) and the heat transfer medium circulation cycle (40) transfer thermal energy via the hot water circulation cycle (30), thereby enabling stable operation of the ORC cycle (3).

[0076] [3] In some embodiments, the exhaust heat recovery system (1) described in [2] above, The hot water circulation cycle (30) further includes a separator (38) that separates the hot water flowing downstream of the first heat exchanger (31) and upstream of the heater (41) into a gas phase and a liquid phase. The separator (38) is provided upstream of the branching point where the steam branching line (7) branches off from the steam supply line (6), or upstream of the steam turbine (9) on the steam branching line (7).

[0077] According to the configuration described in [3] above, the waste heat recovery system (1) according to this embodiment may heat the hot water flowing through the hot water circulation cycle (30) with excess thermal energy that exceeds the thermal energy recovery capacity of the ORC cycle (3). The separator (38) can recover the excess thermal energy in the hot water circulation cycle (30) into the steam flowing upstream of the branching point where the steam branch line (7) of the steam supply line (6) branches off, or upstream of the steam turbine (9) of the steam branch line (7). Therefore, the waste heat recovery system (1) according to this embodiment can recover thermal energy that cannot be recovered by the ORC cycle (3) without impairing the thermal energy recovery efficiency of the ORC cycle (3).

[0078] [4] In some embodiments, the exhaust heat recovery system (1) described in [3] above, The system further includes a steam flow rate adjustment device (39) configured to increase the flow rate of the steam led from the separator (38) to the steam turbine (9) when the pressure inside the separator (38) exceeds a predetermined value.

[0079] According to the configuration described in [4] above, if the pressure inside the separator (38) exceeds a predetermined value, there is excess thermal energy in the hot water circulation cycle (30). In this case, the steam flow rate adjustment device (39) increases the flow rate of steam guided from the separator (38) to the steam turbine (9), allowing the excess thermal energy in the hot water circulation cycle (30) to be quickly recovered by the steam turbine (9).

[0080] [5] In some embodiments, the exhaust heat recovery system (1) described in any of [1] to [4] above, The steam branch line (8) further includes a steam dump valve (74) installed in parallel with the steam turbine (9).

[0081] According to the configuration described in [5] above, the excess steam flowing through the steam branch line (8) can be discharged by directing it to the steam dump valve (74).

[0082] [6] In some embodiments, the exhaust heat recovery system (1) described in any of [1] to [8] above, The steam turbine (9) is Rotating shaft (91), A one-sided turbine wheel (92) is attached to one side of the rotating shaft (91), The other side turbine wheel (93) is attached to the other side of the rotating shaft (91), The turbine casing (94) is configured to house the rotating shaft (91), the one-side turbine wheel (92), and the other-side turbine wheel (93), The aforementioned steam branch line (7) is A first steam introduction line (77) for guiding the steam to the one-side turbine wheel (92), A second steam introduction line (77) for guiding the steam to the other side turbine wheel (92) includes a second steam introduction line (78) branching off from the first steam introduction line (77).

[0083] According to the configuration described in [6] above, the steam introduced to one side turbine wheel (92) via the first steam introduction line (77) has a temperature and pressure similar to that of the steam introduced to the other side turbine wheel (93) via the second steam introduction line (78) branching off from the first steam introduction line (77). As a result, the thrust load (TL1) directed toward the other side of the rotating shaft (91) caused by the rotation of one side turbine wheel (92) and the thrust load (TL2) directed toward one side of the rotating shaft (91) caused by the rotation of the other side turbine wheel (93) are balanced. As a result, these thrust loads (TL1, TL2) cancel each other out, making it possible to reduce the thrust load acting on the rotating shaft (91) of the steam turbine (9).

[0084] [7] In some embodiments, the exhaust heat recovery system (1) described in [6] above, The generator (90) further includes a rotor (901) attached to the rotating shaft (91) between the one turbine wheel (92) and the other turbine wheel (93), and a stator (902) positioned on the outer circumference of the rotor (901), The steam turbine (9) is At least one one-sided gas bearing (95) is configured to rotatably support the rotating shaft (91) between the one-sided turbine wheel (92) and the rotor (901) in the axial direction of the rotating shaft (91), The system further includes at least one other-side gas bearing (96) positioned between the other-side turbine wheel (93) and the rotor (901) in the axial direction of the rotating shaft (91), and configured to rotatably support the rotating shaft (91),

[0085] According to the configuration described in [7] above, the bearings (95, 96) that rotatably support the rotating shaft (91) of the steam turbine (9) are gas bearings, thereby enabling an oil-free operation. By eliminating the oil in the steam turbine (9), problems such as thermal degradation of the lubricating oil supplied to the bearings are eliminated, thus improving the heat resistance of the steam turbine (9).

[0086] [8] In some embodiments, the exhaust heat recovery system (1) described in [7] above, The steam turbine (9) is Between the one-side turbine wheel (92) and the one-side gas bearing (95) adjacent to the one-side turbine wheel (92) in the axial direction, a pair of one-side non-contact seal portions (101, 102) seal the space between the rotating shaft (91) and the turbine casing (94), Between the other side turbine wheel (93) and the other side gas bearing (96) adjacent to the other side turbine wheel (93) in the axial direction, a pair of other side non-contact seal portions (103, 104) seal the space between the rotating shaft (91) and the turbine casing (94), At least one cooling gas introduction line (105) for introducing cooling gas into the radial gap (97) formed between the rotating shaft (91) and the turbine casing (94), located on the other side of each of the pair of one-sided non-contact seal portions (101, 102), and on the one side of each of the pair of other-sided non-contact seal portions (103, 104), A gas discharge line (108) for discharging gas from each of the following: a one-sided seal space (106) formed between the pair of one-sided non-contact seal portions (101, 102), and a other-sided seal space (107) formed between the pair of other-sided non-contact seal portions (103, 104), The system further includes a suction device (109) provided in the gas discharge line (108) for sucking the gas from the one-side sealing space (106) and the other-side sealing space (107), respectively.

[0087] According to the configuration described in [8] above, in the steam turbine (9), cooling gas introduced into the radial gap (97) via the cooling gas introduction line (105) may enter the one-side seal space (106) and the other-side seal space (107). By using a suction device (109) to draw gas from the one-side seal space (106) and the other-side seal space (107) to the gas discharge line (108), it is possible to suppress the flow of cooling gas into the steam used to rotate the one-side turbine wheel (92) and the steam used to rotate the other-side turbine wheel (93). [Explanation of symbols]

[0088] 1. Waste heat recovery system 2. Exhaust gas line 3 ORC cycles 5. Auxiliary boiler 6. Steam supply line 7 Steam branch line 9 Steam Turbine 10 ships 11 Internal Combustion Engine 13 Supercharger 14 Exhaust gas turbine 15 Compressor 30 Hot water circulation cycle 31 1st heat exchanger 32 Hot water pump 33. First hot water line 34. Second hot water line 35 Bypass Line 36, 37, 50 Flow control valve 38 Separator 39 Steam flow rate adjustment device 40 Heat transfer fluid circulation cycle 41 Heater 42 Turbine 43. First heat transfer fluid line 44 Second heat transfer fluid line 45 Condenser 46 Heat transfer fluid circulation pump 47,90 Generator 51 Second heat exchanger 52 Boiler body 53 Boiler furnace 54. First boiler feedwater line 55 Second boiler feedwater line 56 Boiler-side pump 57 Water tank 58 Water supply line 59 Water supply pump 61 Steam Demanders 71 Upstream end 72 Downstream end 73 Gas-liquid water separator 74 Steam dump valve 75. Steam Line 1 76. Second Steam Line 77. First steam introduction line 78. Second steam introduction line 91 Rotating Shaft 92 One-sided turbine wheel 93 Other side turbine wheel 94 Turbine Casing 95 One-sided gas bearing 96 Other gas bearing 97 Radial clearance 101 One-sided non-contact sealing section 103 Non-contact sealing portion on the other side 105 Cooling gas introduction line 106 One-sided sealing space 107 Other side sealing space 108, 108A, 108B Gas discharge lines 109 Suction device 391 Pressure regulating valve 392 Pressure acquisition device 393 Opening degree indicating device 901 Rotor 902 stater LA axis TL1, TL2 thrust load

Claims

1. A waste heat recovery system configured to recover the thermal energy of exhaust gases emitted from an internal combustion engine installed on a ship, An exhaust gas line for guiding exhaust gas discharged from the internal combustion engine, An ORC cycle comprising a turbine configured to be driven by a heat transfer medium having a lower boiling point than water, wherein the ORC cycle comprises a first heat exchanger configured to recover the thermal energy of the exhaust gas flowing through the exhaust gas line, and the ORC cycle is configured to heat the heat transfer medium with the thermal energy of the exhaust gas recovered by the first heat exchanger, An auxiliary boiler for generating steam to be supplied to the steam demander of the aforementioned vessel, wherein the auxiliary boiler includes a second heat exchanger configured to recover thermal energy from the exhaust gas flowing upstream of the first heat exchanger in the exhaust gas line, and the auxiliary boiler is configured to generate the steam using the thermal energy of the exhaust gas recovered by the second heat exchanger, A steam supply line for supplying the steam discharged from the auxiliary boiler to the steam demanding party, A steam branch line that branches off from the aforementioned steam supply line, A steam turbine configured to be driven by the steam flowing through the steam branch line is provided. Waste heat recovery system.

2. The ORC cycle is, A hot water circulation cycle that circulates the hot water heated in the first heat exchanger, A heat transfer medium circulation cycle that circulates the aforementioned heat transfer medium, A heater configured to heat the heat transfer medium using thermal energy recovered from the hot water flowing through the hot water circulation cycle, The waste heat recovery system according to claim 1.

3. The hot water circulation cycle further includes a separator that separates the hot water flowing downstream of the first heat exchanger and upstream of the heater into a gas phase and a liquid phase. The separator is provided upstream of the branching point where the steam branch line of the steam supply line branches off, or upstream of the steam turbine of the steam branch line. The waste heat recovery system according to claim 2.

4. The system further includes a steam flow rate adjustment device configured to increase the flow rate of steam led from the separator to the steam turbine when the internal pressure of the separator exceeds a predetermined value. The waste heat recovery system according to claim 3.

5. The steam branch line further includes a steam dump valve installed in parallel with the steam turbine. A waste heat recovery system according to any one of claims 1 to 4.

6. The aforementioned steam turbine is Rotating shaft and A one-sided turbine wheel attached to one side of the aforementioned rotating shaft, A turbine wheel attached to the other side of the aforementioned rotating shaft, The turbine casing includes the rotating shaft, the one-side turbine wheel, and the other-side turbine wheel, The aforementioned steam branch line is A first steam introduction line for guiding the steam to the one-side turbine wheel, A second steam introduction line for guiding the steam to the other side turbine wheel, comprising a second steam introduction line branching off from the first steam introduction line, A waste heat recovery system according to any one of claims 1 to 4.

7. The generator further includes a rotor attached to the rotating shaft between the one turbine wheel and the other turbine wheel, and a stator positioned on the outer circumference of the rotor, The aforementioned steam turbine is At least one one-sided gas bearing configured to rotatably support the rotating shaft between the one-sided turbine wheel and the rotor in the axial direction of the rotating shaft, The system further includes at least one other-side gas bearing positioned between the other-side turbine wheel and the rotor in the axial direction of the rotating shaft and configured to rotatably support the rotating shaft, The waste heat recovery system according to claim 6.

8. The aforementioned steam turbine is Between the one-side turbine wheel and the one-side gas bearing adjacent to the one-side turbine wheel in the axial direction, a pair of one-side non-contact seal portions seal the space between the rotating shaft and the turbine casing, Between the other turbine wheel and the other gas bearing adjacent to the other turbine wheel in the axial direction, a pair of other non-contact seal portions seal the space between the rotating shaft and the turbine casing, At least one cooling gas introduction line for introducing cooling gas into the radial gap formed between the rotating shaft and the turbine casing, located on the other side of each of the pair of one-sided non-contact seal portions, and on the one side of each of the other-sided non-contact seal portions, A gas discharge line for discharging gas from each of the one-sided seal space formed between the pair of one-sided non-contact seal portions and the other-sided seal space formed between the pair of the other-sided non-contact seal portions, The gas discharge line further includes a suction device provided for drawing the gas from the one-side sealing space and the other-side sealing space, respectively. The waste heat recovery system according to claim 7.

Images