Cold ORC power generator and operating method for the same

Abstract

To provide a cold ORC power generator that enables reduction of the size.SOLUTION: A cold ORC power generator 1 includes: an LNG vaporization flow passage 12 for causing LNG to flow and vaporize; a first Rankine cycle 2A in which methane circulates; and a second Rankine cycle 2B and a third Rankine cycle 2C in which ethylene and propane having a boiling point higher than that of methane circulate. A second heater 3B and a third heater 3C are provided between a first liquid pump 5A and a first evaporator 7A so as to cause methane to exchange heat. A first heater 3A is provided on an upstream side in a flowing direction of LNG flowing in the LNG vaporization flow passage 12 of the second heater 3B and the third heater 3C. Each power generation turbine 9A, 9B, 9C includes: a rotor shaft; a moving blade; a power generator rotor corotating with the rotor shaft; and a power generator stator disposed opposing to the power generator rotor.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a cold ORC power generation device and an operating method thereof. [Background technology]

[0002] A cold ORC (Organic Rankine Cycle) power generation system that uses a cold heat source such as LNG is known (for example, Patent Document 1). Such a cold ORC power generation system uses an organic fluid such as propane as a working fluid for performing a Rankine cycle. Patent Document 1 discloses that LNG is vaporized using multiple Rankine cycles. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2022-542136 Summary of the Invention [Problem to be solved by the invention]

[0004] When multiple Rankine cycles are used as in Patent Document 1, it is necessary to provide a turbine and a generator driven by the turbine for each Rankine cycle. Generally, turbines and generators, including their associated devices, become complex and large-scale equipment, so there is a problem that arranging turbines and generators in the number corresponding to the number of Rankine cycles leads to an increase in the complexity and size of the equipment.

[0005] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a cold ORC power generation device that has a simple configuration and can be made compact, and an operating method thereof. [Means for solving the problem]

[0006] A cold-heat ORC power generation apparatus according to one embodiment of the present disclosure includes a refrigerant vaporization flow path that circulates a liquefied refrigerant to vaporize it, an upstream Rankine cycle in which an upstream working fluid that is an organic fluid circulates, and a downstream Rankine cycle in which a downstream working fluid that is an organic fluid having a higher boiling point than the upstream working fluid circulates. The upstream Rankine cycle includes a upstream heater that uses the upstream working fluid to heat the liquefied refrigerant flowing through the refrigerant vaporization flow path, a upstream liquid pump that transports the upstream working fluid liquefied in the upstream heater, a upstream evaporator that evaporates the upstream working fluid guided from the upstream liquid pump, and a upstream power generation turbine that is driven by the upstream working fluid vaporized in the upstream evaporator to generate power. The downstream Rankine cycle includes a downstream working fluid that circulates the liquefied refrigerant flowing through the refrigerant vaporization flow path using the downstream working fluid. a downstream heater for heating a downstream working fluid, a downstream liquid pump for transporting the downstream working fluid liquefied in the downstream heater, a downstream evaporator for evaporating the downstream working fluid guided from the downstream liquid pump, and a downstream power generation turbine driven by the downstream working fluid vaporized in the downstream evaporator to generate power, the downstream heater is provided between the upstream liquid pump and the upstream evaporator so that the upstream working fluid exchanges heat, the upstream heater is provided upstream of the downstream heater in the flow direction of the liquefied refrigerant flowing through the refrigerant vaporization passage, and the upstream power generation turbine and the downstream power generation turbine each include a rotor shaft, a rotor blade attached to the rotor shaft, a generator rotor that rotates together with the rotor shaft, and a generator stator arranged opposite the generator rotor.

[0007] A method for operating a cold-heat ORC power generation system according to one embodiment of the present disclosure is a method for operating a cold-heat ORC power generation system including a refrigerant vaporization passage through which a liquefied refrigerant is circulated to vaporize it, an upstream Rankine cycle in which a upstream working fluid that is an organic fluid is circulated, and a downstream Rankine cycle in which a downstream working fluid that is an organic fluid having a higher boiling point than the upstream working fluid is circulated, wherein the upstream Rankine cycle includes a upstream heater that uses the upstream working fluid to heat the liquefied refrigerant flowing through the refrigerant vaporization passage, a upstream liquid pump that transports the upstream working fluid liquefied in the upstream heater, a upstream evaporator that evaporates the upstream working fluid guided from the upstream liquid pump, and a upstream power generation turbine that is driven by the upstream working fluid vaporized in the upstream evaporator to generate power, and the downstream Rankine cycle includes a downstream working fluid that is an organic fluid having a higher boiling point than the upstream working fluid, and a downstream Rankine cycle that uses the downstream working fluid to heat the liquefied refrigerant flowing through the refrigerant vaporization passage. a downstream heater that heats the liquefied refrigerant flowing through the refrigerant vaporization passage, a downstream liquid pump that transports the downstream working fluid liquefied in the downstream heater, a downstream evaporator that evaporates the downstream working fluid guided from the downstream liquid pump, and a downstream power-generating turbine that is driven by the downstream working fluid vaporized in the downstream evaporator to generate power, wherein the upstream working fluid is heat exchanged between the upstream liquid pump and the upstream evaporator by the downstream heater, and the upstream heater heats the liquefied refrigerant upstream of the downstream heater in the flow direction of the liquefied refrigerant flowing through the refrigerant vaporization passage, and the upstream power-generating turbine and the downstream power-generating turbine generate power by a rotor shaft, moving blades attached to the rotor shaft, a generator rotor that rotates together with the rotor shaft, and a generator stator arranged opposite the generator rotor. Effect of the Invention

[0008] The cold ORC power generation device can be made smaller with a simple configuration. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic configuration diagram illustrating a cold ORC power generation device according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a vertical cross-sectional view of the power generating turbine of FIG. [Diagram 3]3 is a cross-sectional view taken along line AA in FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. 1 shows a cold ORC (Organic Rankine Cycle) power generation system 1 according to this embodiment. The cold ORC power generation system 1 includes a first Rankine cycle (front-stage Rankine cycle) 2A, a second Rankine cycle (back-stage Rankine cycle) 2B, and a third Rankine cycle (back-stage Rankine cycle) 2C, each of which uses three working fluids with different boiling points. These Rankine cycles 2A, 2B, and 2C are configured in a cascade arrangement.

[0011] As the three working fluids with different boiling points, organic fluids are used, with methane (boiling point at atmospheric pressure: -161.6°C) being used for the first Rankine cycle 2A, ethylene (boiling point at atmospheric pressure: -103.7°C) being used for the second Rankine cycle 2B, and propane (boiling point at atmospheric pressure: -42°C) being used for the third Rankine cycle 2C. Note that the working fluid is not limited to the above, and examples of the working fluid that can be used include low molecular weight hydrocarbons such as isopentane and butane, and R134a and R245fa, which are used as refrigerants for air conditioners, etc.

[0012] In the cold ORC power generation system 1 of this embodiment, LNG (Liquefied Natural Gas) is used as a refrigerant that serves as a cold source. In addition to LNG, LPG (Liquefied Petroleum Gas: boiling point -42°C), carbon dioxide (boiling point -78°C), etc. can be used as the refrigerant.

[0013] LNG is supplied from an LNG source 10 in which LNG is stored, and is vaporized by flowing through an LNG vaporization flow path (refrigerant vaporization flow path) 12. The vaporized natural gas (NG) is heated to a predetermined temperature by seawater SW in a trim heater 14, and then supplied to a demand destination (not shown).

[0014] <First Rankine Cycle 2A> The first Rankine cycle 2A includes a first heater (pre-heater) 3A, a first circulation pump (pre-liquid pump) 5A, a first evaporator (pre-evaporator) 7A, and a first power generation turbine (pre-power generation turbine) 9A. The first heater 3A, the first circulation pump 5A, the first evaporator 7A, and the first power generation turbine 9A are connected to a first circulation flow path 11A through which methane, which is a working fluid, circulates.

[0015] The first heater 3A exchanges heat between LNG supplied from the LNG source 10 via the LNG vaporization passage 12 and methane supplied from the first power generation turbine 9A via the first circulation passage 11A. In the first heater 3A, the LNG is heated by the methane from about -162°C to about -100°C, for example. The heated LNG passes through the LNG vaporization passage 12 and is guided to the second heater 3B.

[0016] As the methane passes through the first heater 3A, heat of condensation is removed from the methane, and the methane is condensed and liquefied. Therefore, the first heater 3A is used as a condenser in the first Rankine cycle 2A that uses methane as the working fluid.

[0017] The first circulation pump 5A sucks in methane liquefied in the first heater 3A and discharges it toward the second heater 3B and the third heater 3C on the downstream side. The liquefied methane discharged from the first circulation pump 5A is heated in turn as it passes through the second heater 3B and the third heater 3C and is supplied to the first evaporator 7A. The first circulation pump 5A is controlled by a control unit, and the rotation speed can be controlled so that the flow rate is variable. Alternatively, the flow rate may be made variable by the opening degree of a valve (not shown) provided downstream of the first circulation pump 5A. The discharge flow rate of the first circulation pump 5A is controlled, for example, according to the pressure of the condensation section of the first heater 3A.

[0018] The first evaporator 7A is disposed downstream of the third heater 3C, and evaporates and gasifies the liquefied methane by exchanging heat with seawater SW, which is a heat source.

[0019] A first power generating turbine 9A is provided downstream of the first evaporator 7A. The first power generating turbine 9A is rotated by the inflowing working fluid (vaporized methane). The first power generating turbine 9A is integrally configured with a generator, the specific configuration of which will be described later.

[0020] <Second Rankine Cycle 2B> The second Rankine cycle 2B includes a second heater (rear stage heater) 3B, a second circulation pump (rear stage liquid pump) 5B, a second evaporator (rear stage evaporator) 7B, and a second power generation turbine (rear stage power generation turbine) 9B. The second heater 3B, the second circulation pump 5B, the second evaporator 7B, and the second power generation turbine 9B are connected to a second circulation flow path 11B through which ethylene, which is a working fluid, circulates.

[0021] The second heater 3B exchanges heat between LNG supplied from the LNG source 10 via the LNG vaporization passage 12 and heated in the first heater 3A, liquefied methane supplied from the first circulation pump 5A via the first circulation path 11A, and ethylene supplied from the second power generation turbine 9B via the second circulation passage 11B. In the second heater 3B, the LNG is heated by the ethylene from about -100°C to about -70°C. The heated LNG passes through the LNG vaporization passage 12 and is guided to the third heater 3C.

[0022] As ethylene passes through the second heater 3B, heat of condensation is removed from the ethylene, and the ethylene is condensed and liquefied. Therefore, the second heater 3B is used as a condenser in the second Rankine cycle 2B that uses ethylene as the working fluid.

[0023] The second circulation pump 5B sucks in ethylene liquefied in the second heater 3B and discharges it toward the third heater 3C downstream. The liquefied ethylene discharged from the second circulation pump 5B is heated as it passes through the third heater 3C and is supplied to the second evaporator 7B. The second circulation pump 5B is controlled by a control unit, and the rotation speed can be controlled so that the flow rate is variable. Alternatively, the flow rate may be made variable by the opening degree of a valve (not shown) provided downstream of the second circulation pump 5B. The discharge flow rate of the second circulation pump 5B is controlled, for example, according to the pressure of the condensation section of the second heater 3B.

[0024] The second evaporator 7B is disposed downstream of the third heater 3C, and evaporates and gasifies the liquefied ethylene by exchanging heat with seawater SW, which is a heat source.

[0025] A second power generation turbine 9B is provided downstream of the second evaporator 7B. The second power generation turbine 9B is rotated by the inflowing working fluid (vaporized ethylene). The second power generation turbine 9B is integrally configured with a generator, the specific configuration of which will be described later.

[0026] <Third Rankine Cycle 2C> The third Rankine cycle 2C includes a third heater (rear stage heater) 3C, a third circulation pump (rear stage liquid pump) 5C, a third evaporator (rear stage evaporator) 7C, and a third power generation turbine (rear stage power generation turbine) 9C. The third heater 3C, the third circulation pump 5C, the third evaporator 7C, and the third power generation turbine 9C are connected to a third circulation flow path 11C through which propane, which is a working fluid, circulates.

[0027] The third heater 3C exchanges heat between LNG supplied from the LNG source 10 via the LNG vaporization passage 12 and heated by the first heater 3A and the second heater 3B, liquefied methane supplied from the first circulation pump 5A via the first circulation passage 11A, liquefied ethylene supplied from the second circulation pump 5B via the second circulation passage 11B, and propane supplied from the third power generation turbine 9C via the third circulation passage 11C. In the third heater 3C, the LNG is heated by the propane from about -70°C to about -35°C and vaporized. The vaporized natural gas (NG) is heated to a predetermined temperature by seawater SW in the trim heater 14 and then supplied to a demand destination (not shown).

[0028] As the propane passes through the third heater 3C, the heat of condensation is removed from the propane, and the propane is condensed and liquefied. Therefore, the third heater 3C is used as a condenser in the third Rankine cycle 2C using propane as the working fluid.

[0029] The third circulation pump 5C sucks in the propane liquefied by the third heater 3C and discharges it toward the third evaporator 7C downstream. The third circulation pump 5C is controlled by a control unit, and the rotation speed can be controlled so that the flow rate is variable. Alternatively, the flow rate may be varied by the opening of a valve (not shown) provided downstream of the third circulation pump 5C. The discharge flow rate of the third circulation pump 5C is controlled, for example, according to the pressure of the condensation section of the third heater 3C.

[0030] The third evaporator 7C is disposed downstream of the third heater 3C, and evaporates and gasifies the liquefied propane by exchanging heat with seawater SW, which is a heat source.

[0031] A third power generation turbine 9C is provided downstream of the third evaporator 7C. The third power generation turbine 9C is rotated by the inflowing working fluid (vaporized propane). The third power generation turbine 9C is integrally configured with a generator, the specific configuration of which will be described later.

[0032] The above-mentioned three heaters 3A, 3B, and 3C are arranged in series on the LNG vaporization flow path 12. If the first heater 3A is a pre-heater, the second heater 3B and the third heater 3C are post-heaters.

[0033] The control unit is composed of, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and a computer-readable storage medium. A series of processes for realizing various functions is stored in a storage medium or the like in the form of a program, for example, and the CPU reads this program into the RAM or the like and executes information processing and arithmetic processing to realize various functions. The program may be installed in a ROM or other storage medium in advance, may be provided in a state stored in a computer-readable storage medium, or may be distributed via a wired or wireless communication means. The computer-readable storage medium may be a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like.

[0034] <Power generating turbine> The above-mentioned power generation turbines 9A, 9B, and 9C are integrated power generation turbines in which a turbine section and a power generation section are integrated, and have a similar configuration. Therefore, in the following, these power generation turbines 9A, 9B, and 9C will be represented by the reference numeral 9, and a description will be given of their common configuration.

[0035] 2 shows a longitudinal section of the power generating turbine 9. FIG 3 shows a cross section taken along line AA of FIG 2.

[0036] Hereinafter, the upstream side in the flow direction of the working fluid in the power generation turbine 9 may be simply referred to as the upstream side, and the downstream side in the flow direction of the working fluid in the power generation turbine 9 may be simply referred to as the downstream side. Furthermore, the radial direction of the power generation turbine 9 may be simply referred to as the radial direction, and the circumferential direction of the power generation turbine 9 may be simply referred to as the circumferential direction. Furthermore, the direction along the axis CA of the power generation turbine 9 may be simply referred to as the axial direction.

[0037] 2, the power generation turbine 9 includes a rotor shaft 16, a casing 6, a generator 8, a first-stage axial turbine 23, a second-stage axial turbine 24, and a working fluid flow path 63. The first-stage axial turbine 23 is composed of a first-stage rotor blade 23B and a first-stage stator blade 23A. The second-stage axial turbine 24 is composed of a second-stage rotor blade 24B and a second-stage stator blade 24A.

[0038] The rotor shaft 16 includes a shaft portion 111 having a longitudinal direction along the axis CA of the power generation turbine 9, a one-side disk portion 113A protruding radially outward in a circular plate shape from an outer surface 112A on one side (upstream side) of the shaft portion 111, and an other-side disk portion 113B protruding radially outward in a circular plate shape from an outer surface 112B on the other side (downstream side) of the shaft portion 111.

[0039] The axis CA of the power generation turbine 9 coincides with the axis of the rotor shaft 16 and the axis of the casing 6 .

[0040] At one end of the shaft portion 111 in the axial direction, a one-side protruding portion 114A is formed, which protrudes outward in the axial direction from an inner casing member 61A described later. At the other end of the shaft portion 111 in the axial direction, a other-side protruding portion 114B is formed, which protrudes outward in the axial direction from the inner casing member 61A. The one-side protruding portion 114A and the other-side protruding portion 114B are formed to have a smaller diameter than other parts of the shaft portion 111. The one-side disk portion 113A described above is attached to the outer surface 112A of the one-side protruding portion 114A. Similarly, the other-side disk portion 113B described above is attached to the outer surface 112B of the other-side protruding portion 114B. At one side of the one-side disk portion 113A in the one-side protruding portion 114A, a one-side nut 115A is screwed, thereby fixing the one-side disk portion 113A to the shaft portion 111. Similarly, a second-side nut 115B is screwed onto the second-side protrusion 114B on the other side of the second-side disk portion 113B, thereby fixing the second-side disk portion 113B to the shaft portion 111.

[0041] The casing 6 is composed of an inner casing 61 that rotatably houses the rotor shaft 16 and an outer casing 62 that is disposed on the outer periphery of the inner casing 61 . The inner casing 61 includes an inner casing member 61A, a one-side cover member 61B arranged on one axial side (upstream side) of the inner casing member 61A, and an other-side cover member 61C arranged on the other axial side (downstream side) of the inner casing member 61A.

[0042] The inner casing member 61A has a longitudinal direction along the axial direction of the power generation turbine 9, and is disposed between the first stage rotor blades 23B and the second stage rotor blades 24B in the axial direction of the power generation turbine 9. A space 610 is formed inside the inner casing member 61A, and houses the shaft portion 111 and a generator 8 (in the illustrated example, a generator rotor 81 and a generator stator 82) described below.

[0043] The one-side cover member 61B is arranged on one side of the inner casing member 61A so as to cover one end of the shaft portion 111, including the one-side protrusion 114A and the one-side nut 115A screwed thereto, on one axial side of the first stage rotor blade 23B.

[0044] The other side cover member 61C is positioned on the other side of the inner casing member 61A so as to cover the other side end of the shaft portion 111, including the other side protrusion 114B and the other side nut 115B screwed thereto, on the other axial side of the second stage rotor blade 24B.

[0045] The generator 8 is configured to include a generator rotor 81 including permanent magnets formed on the outer circumferential surface of the rotor shaft 16 , and a generator stator 82 supported on the inner circumferential surface 611 of the inner casing 61 .

[0046] The generator rotor 81 is integrally formed on the outer circumferential surface of the rotor shaft 16, and the two have an integral structure. However, the generator rotor 81 and the rotor shaft 16 may be formed separately, and the generator rotor 81 may be supported on the outer circumferential surface of the rotor shaft. The generator stator 82 is supported on the inner circumferential surface 611 of the inner casing member 61A, and is disposed radially outward of the generator rotor 81. The generator rotor 81 and the generator stator 82 are disposed on the other side of a one-side radial bearing 103A (described later) and on the one side of a other-side radial bearing 103B in the axial direction of the rotor shaft 16. That is, the generator rotor 81 and the generator stator 82 are located between the one-side radial bearing 103A and the other-side radial bearing 103B in the axial direction of the rotor shaft 16.

[0047] The first stage rotor blades 23B are provided on one side of the rotor shaft 16 relative to the generator rotor 81. In addition, the first stage stator vanes 23A are supported by an inner circumferential surface 621 of the outer casing 62 or an outer circumferential surface 612 of the inner casing 61 on one side of the rotor shaft 16 relative to the first stage rotor blades 23B.

[0048] The first stage rotor blades 23B are attached to the outer peripheral surface of the one-side disk portion 113A described above with a gap therebetween in the circumferential direction. The first stage stator vanes 23A are supported by the inner peripheral surface 621 of the outer casing 62 and are provided on the inner peripheral surface 621 with a gap therebetween in the circumferential direction. In another embodiment, the first stage stator vanes 23A may be supported by the outer peripheral surface 612 (the outer peripheral surface 612B of the one-side cover member 61B) of the inner casing 61 and provided on the outer peripheral surface 612 (the outer peripheral surface 612B) with a gap therebetween in the circumferential direction, or may be supported by both the inner peripheral surface 621 of the outer casing 62 and the outer peripheral surface 612 of the inner casing 61 (the outer peripheral surface 612B of the one-side cover member 61B).

[0049] The second stage stator vane 24A is supported by an inner circumferential surface 621 of the outer casing 62 or an outer circumferential surface 612 of the inner casing 61 on the other side of the rotor shaft 16 relative to the generator rotor 81. In addition, the second stage rotor blade 24B is provided on the other side of the rotor shaft 16 relative to the second stage stator vane 24A.

[0050] The second stage rotor blades 24B are attached to the outer peripheral surface of the above-mentioned other-side disk portion 113B with a gap therebetween in the circumferential direction. The second stage stator vanes 24A are supported by the inner peripheral surface 621 of the outer casing 62 and are provided on the inner peripheral surface 621 with a gap therebetween in the circumferential direction. In another embodiment, the second stage stator vanes 24A may be supported by the outer peripheral surface 612 (the outer peripheral surface 612A of the inner casing member 61A) of the inner casing 61 and provided on the outer peripheral surface 612 (the outer peripheral surface 612A) with a gap therebetween in the circumferential direction, or may be supported by both the inner peripheral surface 621 of the outer casing 62 and the outer peripheral surface 612 of the inner casing 61 (the outer peripheral surface 612A of the inner casing member 61A).

[0051] The working fluid flow path 63 is defined between the outer peripheral surface 612 of the inner casing 61 and the inner peripheral surface 621 of the outer casing 62, and is configured to extend along the axial direction of the rotor shaft 16 from upstream of the first stage stator vane 23A to downstream of the second stage rotor blade 24B.

[0052] The working fluid flow passage 63 has a longitudinal direction along the axial direction of the power generation turbine 9 and has an annular cross section surrounding the periphery of the inner casing member 61A. The working fluid flow passage 63 is configured to guide the working fluid from one side to the other side between the outer casing 62 and the inner casing 61.

[0053] A one-side introduction passage 64A is formed on one side of the working fluid flow passage 63 for introducing the working fluid from one side along the axial direction into the working fluid flow passage 63. The one-side introduction passage 64A is defined by an inner surface 630A of an inlet casing 65A connected to one side of the outer casing 62, on one axial side of the one-side cover member 61B.

[0054] A second-side discharge passage 64B is formed on the other side of the working fluid flow passage 63 for discharging the working fluid in the axial direction from the working fluid flow passage 63 to the other side. The second-side discharge passage 64B is defined by an inner surface 630B of an outlet casing 65B connected to the other side of the outer casing 62, on the other axial side of the other-side cover member 61C.

[0055] The working fluid introduced from the one-side introduction passage 64A into the working fluid passage 63 passes through the first-stage stator vane 23A, and then acts on the first-stage rotor blade 23B to impart a rotational force to the shaft portion 111, thereby driving the first-stage axial turbine 23. The working fluid that has passed through the first-stage rotor blade 23B exchanges heat with heat generated in the generator 8 (generator rotor 81, generator stator 82) housed in the space 610 formed inside the inner casing member 61A while flowing through the working fluid passage 63. In other words, the working fluid flowing through the working fluid passage 63 absorbs the heat generated in the generator 8. As a result, the generator 8 is cooled, and the working fluid flowing through the working fluid passage 63 is heated.

[0056] The heated working fluid passes through the second-stage stator vanes 24A, and then acts on the second-stage rotor blades 24B to impart a rotational force to the shaft portion 111, thereby driving the second-stage axial turbine 24. In other words, the working fluid heated by heat exchange with the generator 8 in the working fluid passage 63 flows into the second-stage axial turbine 24, and this heated working fluid drives the second-stage axial turbine 24. The working fluid that has flowed through the second-stage axial turbine 24 is discharged from the working fluid passage 63 to the other-side discharge passage 64B, and flows out to the outside of the power-generating turbine 9.

[0057] The power generation turbine 9 configured as above has a structure in which the first stage axial turbine 23 consisting of the first stage rotor blades 23B and the first stage stator vanes 23A is provided on one side of the generator rotor 81, and the second stage axial turbine 24 consisting of the second stage rotor blades 24B and the second stage stator vanes 24A is provided on the other side. In other words, axial turbines are provided on both ends of the generator rotor 81. An axial turbine does not require a large scroll (casing) as in a radial turbine, making it possible to miniaturize the entire power generation turbine.

[0058] The working fluid flows through a working fluid flow path 63 defined between an outer peripheral surface 612 of the inner casing 61 and an inner peripheral surface 621 of the outer casing 62, in the order of the first stage rotor blades 23B, the first stage stator vanes 23A, the second stage rotor blades 24B, and the second stage stator vanes 24A. In other words, the working fluid that has passed through the first stage axial turbine 23 absorbs heat of the generator 8 generated in the generator rotor 81 and the generator stator 82 while flowing through the working fluid flow path 63, and then flows into the second stage axial turbine 24. With this configuration, the generator 8 can be cooled using the working fluid, making it unnecessary or possible to reduce the size of additional cooling mechanisms such as equipment required for cooling or cooling channels, thereby preventing the device from becoming larger.

[0059] The working fluid recovers the exhaust heat from the generator 8, thereby increasing the temperature of the working fluid at the inlet of the second-stage axial turbine 24, thereby improving the efficiency of the second-stage axial turbine 24. In other words, it is possible to achieve both cooling of the generator 8 and exhaust heat recovery.

[0060] Since axial flow turbines are provided on both ends of the rotor shaft 16, the weight is well balanced and no counterweight is required.

[0061] A space 610 formed inside the inner casing member 61A accommodates a first radial bearing 103A and an second radial bearing 103B which rotatably support the shaft portion 111. The first radial bearing 103A is disposed on one side of the generator rotor 81, and the second radial bearing 103B is disposed on the other side of the generator rotor 81. The one-side radial bearing 103A and the other-side radial bearing 103B are disposed so as to contact, at their respective inner peripheries, the outer periphery of the bearing 103A with the outer periphery of the shaft portion 111 of the rotor shaft 16 and rotatably support the shaft portion 111. The one-side radial bearing 103A and the other-side radial bearing 103B are also supported, at their respective outer peripheries, by the inner periphery 611 of the inner casing member 61A. In the following description, a device including the one-side radial bearing 103A and the other-side radial bearing 103B may be simply referred to as radial bearing 103.

[0062] A space 610 formed inside the inner casing member 61A accommodates a thrust collar 101, a one-side thrust bearing 102A arranged facing the thrust collar 101 on one axial side of the thrust collar 101, and an other-side thrust bearing 102B arranged facing the thrust collar 101 on the other axial side of the thrust collar 101. In the following description, a device including the one-side thrust bearing 102A and the other-side thrust bearing 102B may be simply referred to as thrust bearing device 102.

[0063] The one-side radial bearing 103A, the other-side radial bearing 103B, the one-side thrust bearing 102A, and the other-side thrust bearing 102B may be configured by magnetic bearings.

[0064] With magnetic bearings, there is no need to use lubricating oil, and there is no need to form a device for supplying lubricating oil, so the size of the device can be suppressed. In addition, since no lubricating oil is used, it is possible to prevent oil (lubricating oil) from mixing with the working fluid.

[0065] The thrust collar 101 and the thrust bearing device 102 are disposed on the other side of the one-side radial bearing 103A and on one side of the generator rotor 81. That is, the generator rotor 81 and the generator stator 82 are disposed along the axial direction of the rotor shaft 16 between the thrust bearing device 102 and the other-side radial bearing 103B.

[0066] The blade height of the first stage stator vanes 23A is smaller than that of the second stage stator vanes 24A, and the blade height of the first stage rotor blades 23B is smaller than that of the second stage rotor blades 24B. Therefore, an inner circumferential surface 621 of an outer casing 62 accommodating the first stage axial turbine 23 and the second stage axial turbine 24 is formed so as to make the working fluid flow passage 63 wider in the radial direction at the position where the second stage axial turbine 24 is disposed than at the position where the first stage axial turbine 23 is disposed.

[0067] The above-mentioned power generation turbine 9 further includes a one-side seal portion 26A that seals between the rotor shaft 16 and the inner casing 61 on the other side (downstream side) of the first stage rotor blades 23B and on one side (upstream side) of the generator rotor 81.

[0068] The one-side seal portion 26A seals a gap between an inner circumferential surface 611 of the inner casing member 61A and an outer circumferential surface of the shaft portion 111 of the rotor shaft 16 in a space 610 formed inside the inner casing member 61A. The one-side seal portion 26A is disposed on one side of the one-side radial bearing 103A in the axial direction of the power generation turbine 9.

[0069] A ball bearing 27A is disposed between one side seal portion 26A and one side radial bearing 103A. Similarly, a ball bearing 27B is disposed between the other side seal portion 26B and the other side radial bearing 103B. When the power generation turbine 9 stops or trips due to a problem, these ball bearings 27A and 27B support the rotor shaft 16, thereby preventing contact between the radial bearing 103, which is a magnetic bearing, and the rotor shaft 16.

[0070] The one-side seal portion 26A may include a mechanical seal, or may include a labyrinth seal provided by machining the shaft portion 111 or the inner casing member 61A to have projections and recesses.

[0071] According to such a configuration, leakage of the working fluid that has passed through the first-stage rotor blades 23B into the inner casing 61 can be suppressed, and therefore a reduction in the working fluid flowing through the working fluid passage 63 can be suppressed compared to when the seal member 26 is not provided. As a result, compared to when the seal member is not provided, more of the generator heat generated in the generator rotor 81 and the generator stator 82 can be recovered, and the inlet temperature of the second-stage axial turbine 24 can be increased, and the efficiency of the second-stage axial turbine 24 can be improved.

[0072] In addition, since the working fluid leaking into the inner casing 61 between the high pressure region on the first stage axial turbine 23 side and the low pressure region on the second stage axial turbine 24 side can be sealed, the pressure inside the inner casing 61 can be kept low compared to a case where no seal member is provided. This makes it possible to reduce the thrust force acting on the rotor shaft 16 and the windage loss (loss) occurring inside the inner casing 61.

[0073] The power generation turbine 9 described above further includes an other-side seal portion 26B that seals between the rotor shaft 16 and the inner casing 61 on one side of the second stage rotor blades 24B and on the other side of the generator rotor 81. The other-side seal portion 26B seals a gap between an inner circumferential surface 611 of the inner casing member 61A and an outer circumferential surface of the shaft portion 111 of the rotor shaft 16 in a space 610 formed inside the inner casing member 61A. The other-side seal portion 26B is disposed on the other side of the other-side radial bearing 103B in the axial direction of the power generation turbine 9.

[0074] The one-side seal portion 26A may include a mechanical seal, or may include a labyrinth seal provided by machining the shaft portion 111 or the inner casing member 61A to have projections and recesses.

[0075] According to such a configuration, it is possible to reduce the amount of working fluid that has flowed from the working fluid flow path 63 into the inner casing 61 (inner casing member 61A) flowing out from between the second stage stator vanes 24A and the second stage rotor blades 24B into the working fluid flow path 63, and to suppress the generation of vortex flows in the working fluid passing through the second stage axial turbine 24. This makes it possible to improve the performance of the second stage axial turbine 24.

[0076] As shown in FIGS. 2 and 3, the power generation turbine 9 further includes a bypass line 40 that communicates between the inside of the inner casing 61 and a position in the working fluid flow passage 63 downstream of the second stage rotor blades 24B.

[0077] At one end of the bypass line 40, on one side of the second stage rotor blade 24B in the axial direction of the rotor shaft 16, an inlet side opening 40A is formed so as to open into a space 610 formed inside the inner casing member 61A.

[0078] The bypass line 40 penetrates the axially extending portion 61A1 on the bottom side of the inner casing member 61A below the power generation turbine 9 in the vertical direction. The inlet side opening 40A is located below the bottom surface of the shaft portion 111 and near the inner surface of the axially extending portion 61A1. The axially extending portion 61A1 is a side portion that extends along the axial direction of the inner casing member 61A and is provided so that the distance from the axis CA is constant in the radial direction, and is a bottom side surface on the vertically lower side where the working fluid that has leaked into the inner casing 61 is likely to accumulate. By providing the inlet side opening 40A near the axially extending portion 61A1, it is possible to make it easier for the working fluid to flow into the inlet side opening 40A.

[0079] An inlet side opening 40A at the end of the bypass line 40 is connected to a radially extending introduction portion 40B of the bypass line 40, and the working fluid that has leaked into the inside of the inner casing member 61A passes through the inlet side opening 40A and flows through the radially extending introduction portion 40B of the bypass line 40. The radially extending introduction portion 40B is provided so as to penetrate the inner casing member 61A, the working fluid flow path 63, and the outer casing 62 along the radial direction, and extend to the outside of the outer casing 62.

[0080] The radially extending introduction portion 40B is connected to the axially extending portion 40C, and the working fluid that flows through the radially extending introduction portion 40B flows into the axially extending portion 40C. The axially extending portion 40C is provided outside the outer casing 62 along the axial direction of the rotor shaft 16.

[0081] The axially extending portion 40C is connected to the radially extending discharge portion 40D, and the working fluid that has flowed through the axially extending portion 40C flows into the radially extending discharge portion 40D. The radially extending discharge portion 40D is provided to penetrate the outer casing 62 and the working fluid flow path 63 along the radial direction. In addition, an outlet side opening 40E is formed at the other end of the bypass line 40 on the other side of the second stage rotor blade 24B in the axial direction of the rotor shaft 16 so as to open into the working fluid flow path 63. The radially extending discharge portion 40D is connected to the outlet side opening 40E, and the working fluid that has flowed through the radially extending discharge portion 40D is discharged to the outside of the bypass line 40 from the outlet side opening 40E.

[0082] According to this configuration, the working fluid flowing inside the inner casing 61 can be made to flow to the other side (downstream side) of the second stage rotor blade 24B in the working fluid flow path 63, thereby preventing the working fluid from accumulating inside the inner casing 61.

[0083] In addition, it is possible to reduce the amount of the working fluid flowing inside the inner casing 61 flowing out from between the second stage stator vanes 24A and the second stage rotor blades 24B into the working fluid flow passage 63, thereby suppressing the generation of vortex flows in the working fluid passing through the second stage axial turbine 24. This makes it possible to improve the performance of the second stage axial turbine 24.

[0084] The power generation turbine 9 is provided with both the other-side seal portion 26B and the bypass line 40. In the power generation turbine 9 provided with the other-side seal portion 26B and not the bypass line 40, the working fluid that has flowed into the space 610 inside the inner casing 61 can be reduced from flowing out from between the second-stage stator vane 24A and the second-stage rotor blade 24B into the working fluid flow passage 63. However, since the other-side seal portion 26B is provided, there is no discharge destination for the working fluid that has leaked into the inner casing member 61A, and the working fluid continues to accumulate inside the inner casing member 61A. However, by providing the other-side seal portion 26B and the bypass line 40, the working fluid that has leaked into the inner casing member 61A can be discharged to the outside of the inner casing member 61A, so that the accumulation of the working fluid inside the inner casing member 61A can be suppressed.

[0085] The power generation turbine 9 further includes at least one support 30 extending in the working fluid flow path 63 along the radial direction of the rotor shaft 16. One end of the support 30 is connected to an inner circumferential surface 621 of the outer casing 62, and the other end is connected to an outer circumferential surface 612 of the inner casing 61. The inner casing 61 is supported by the outer casing 62 by the support 30 described above. In the illustrated embodiment, the inner casing member 61A of the inner casing 61 is supported by the support 30.

[0086] The support part 30 is provided in the working fluid flow path 63 and is connected to the outer peripheral surface 612 of the inner casing 61 (the outer peripheral surface 612A of the inner casing member 61A), so that it also functions as a cooling fin to promote cooling of the generator 8.

[0087] It is sufficient that at least one support portion 30 is disposed along the axial direction of the power generation turbine 9, and that at least one support portion 30 is also disposed in the circumferential direction of the outer circumferential surface 612 of the inner casing 61. In the embodiment shown in Fig. 3, eight support portions 30 are disposed at equal intervals in the circumferential direction.

[0088] The upstream end of the support portion 30 is located on one side (upstream side) of the generator stator 82 in the axial direction of the rotor shaft 16. Moreover, the downstream end of the support portion 30 is located on the other side (downstream side) of the generator stator 82 in the axial direction of the rotor shaft 16. With this configuration, the generator stator 82 can be effectively cooled by the support portion 30.

[0089] A portion of the bypass line 40 is formed inside the support part 30. In the illustrated embodiment, a through-hole 40B1 that penetrates the support part 30 along the radial direction is formed inside the support part 30. A portion of the bypass line 40 is composed of this through-hole 40B1. Also, a portion of the bypass line 40 may be composed of a pipe inserted into this through-hole 40B1.

[0090] According to this configuration, the bypass line 40 is provided inside the support part 30 that supports the inner casing 61. Therefore, compared to a case in which the bypass line 40 is not provided inside the support part 30 but is provided so as to extend inside the working fluid flow path 63 outside the support part 30, it is possible to suppress the occurrence of new flow path loss.

[0091] <Operation of cold ORC power generation device 1> Next, the operation of the cold ORC power generation device 1 having the above configuration will be described. Vaporized methane introduced from the exhaust side of the first power generating turbine 9A passes through the first circulation flow path 11A and is introduced to the first heater 3A. Vaporized ethylene introduced from the exhaust side of the second power generating turbine 9B passes through the second circulation flow path 11B and is introduced to the second heater 3B. Vaporized propane introduced from the exhaust side of the third power generating turbine 9C passes through the third circulation flow path 11C and is introduced to the third heater 3C.

[0092] The first heater 3A, the second heater 3B, and the third heater 3C sequentially heat the LNG flowing through the LNG vaporization passage 12, and finally vaporize the LNG. The vaporized natural gas (NG) is heated by a trim heater 14 and then sent to a supply destination.

[0093] The working fluids (methane, ethylene, propane) condensed and liquefied by heating LNG in each heater 3A, 3B, 3C are evaporated in each evaporator 7A, 7B, 7C and then sent to the power generation turbines 9A, 9B, 9C to generate electricity. As shown in Figures 2 and 3, the power generation turbines 9A, 9B, 9C have a turbine section and a power generation section integrated together, making it possible to generate electricity with a simple and compact configuration.

[0094] The effects of the present embodiment described above are as follows. A first Rankine cycle 2A, a second Rankine cycle 2B, and a third Rankine cycle 2C are combined to form a cascade system. After LNG is heated by a first heater 3A of the first Rankine cycle 2A, the LNG is further heated by a second heater 3B of the second Rankine cycle 2B and a third heater 3C of the third Rankine cycle 2C, thereby vaporizing the LNG flowing through an LNG vaporization passage 12. Moreover, by obtaining power output by power generation turbines 9A, 9B, and 9C provided in the respective Rankine cycles 2A, 2B, and 2C, it is possible to increase the output and improve the efficiency compared to a single Rankine cycle.

[0095] The power generating turbines 9A, 9B, and 9C each include a rotor shaft 16, rotor blades attached to the rotor shaft 16, a generator rotor 81 that rotates together with the rotor shaft, and a generator stator 82 disposed opposite the generator rotor 81, and the power generating turbines 9A, 9B, and 9C are configured as an integrated unit. This allows the cold ORC power generating device 1 to be made smaller.

[0096] The cold ORC power generation apparatus and the operating method thereof described in each of the above-described embodiments can be understood, for example, as follows.

[0097] A cold-energy ORC power generation device (1) according to a first aspect of the present disclosure includes a refrigerant vaporization flow path (12) through which a liquefied refrigerant (LNG) flows and vaporizes, a first-stage Rankine cycle (2A) in which a first-stage working fluid that is an organic fluid circulates, and a second-stage Rankine cycle (2B, 2C) in which a second-stage working fluid that is an organic fluid having a higher boiling point than the first-stage working fluid circulates, and the first-stage Rankine cycle (2A) includes a first-stage heater (3A) that uses the first-stage working fluid to heat the liquefied refrigerant (LNG) flowing through the refrigerant vaporization flow path (12). a first-stage liquid pump (5A) that transports a first-stage working fluid liquefied in the first-stage heater (3A), a first-stage evaporator (7A) that evaporates the first-stage working fluid guided from the first-stage liquid pump (5A), and a first-stage power generation turbine (9A) that is driven by the first-stage working fluid vaporized in the first-stage evaporator (7A) and generates power. The second-stage Rankine cycle (2B, 2C) comprises a second-stage heater (3B, 3C) that uses the second-stage working fluid to heat the liquefied refrigerant (LNG) flowing through the refrigerant vaporization passage (12), and a downstream liquid pump (5B, 5C) for transporting downstream working fluid liquefied in the upstream evaporator (3B, 3C), a downstream evaporator (7B, 7C) for evaporating the downstream working fluid guided from the downstream liquid pump (5B, 5C), and a downstream power generation turbine (9B, 9C) driven by the downstream working fluid vaporized in the downstream evaporator (7B, 7C) for generating power, wherein the downstream heater (3B, 3C) is provided between the upstream liquid pump (5A) and the upstream evaporator (7A) so that the upstream working fluid exchanges heat, and the upstream heater The front stage power generation turbine (9A) and the rear stage power generation turbine (9B, 9C) each include a rotor shaft (16), rotor blades (23B, 24B) attached to the rotor shaft (16), a generator rotor (81) that rotates together with the rotor shaft (16), and a generator stator (82) arranged opposite the generator rotor (81).

[0098] The upstream Rankine cycle and the downstream Rankine cycle are configured in a cascade arrangement by providing a downstream heater between the upstream liquid pump and the upstream evaporator of the upstream Rankine cycle. The upstream heater of the upstream Rankine cycle heats the liquefied refrigerant, and the downstream heater of the downstream Rankine cycle further heats the liquefied refrigerant flowing through the refrigerant vaporization passage, thereby vaporizing the liquefied refrigerant. Furthermore, the power generation turbines provided in each Rankine cycle generate power, thereby increasing the power output and improving efficiency compared to a single Rankine cycle. The power generating turbine is configured as an integrated unit that includes a rotor shaft, rotor blades attached to the rotor shaft, a generator rotor that rotates together with the rotor shaft, and a generator stator that faces the generator rotor, thereby making it possible to miniaturize the cold ORC power generating device. The Rankine cycle is not limited to two, that is, the front-stage Rankine cycle and the rear-stage Rankine cycle, but may be three or more.

[0099] A method for operating a cold-energy ORC power generation system (1) according to a first aspect of the present disclosure is a method for operating a cold-energy ORC power generation system including a refrigerant vaporization flow path (12) through which a liquefied refrigerant (LNG) flows and vaporizes, a first-stage Rankine cycle (2A) in which a first-stage working fluid that is an organic fluid circulates, and a second-stage Rankine cycle (2B, 2C) in which a second-stage working fluid that is an organic fluid having a boiling point higher than that of the first-stage working fluid circulates, the first-stage Rankine cycle (2A) using the first-stage working fluid to vaporize the liquefied refrigerant (LNG) flowing through the refrigerant vaporization flow path (12), a first-stage liquid pump (5A) that transports a first-stage working fluid liquefied in the first-stage heater (3A), a first-stage evaporator (7A) that evaporates the first-stage working fluid guided from the first-stage liquid pump (5A), and a first-stage power generation turbine (9A) that is driven by the first-stage working fluid vaporized in the first-stage evaporator (7A) and generates power. The second-stage Rankine cycle (2B, 2C) includes a second-stage heater (3B, a downstream liquid pump (5B, 5C) for transporting a downstream working fluid liquefied in the downstream heater (3B, 3C), a downstream evaporator (7B, 7C) for evaporating the downstream working fluid guided from the downstream liquid pump (5B, 5C), and a downstream power generation turbine (9B, 9C) driven by the downstream working fluid vaporized in the downstream evaporator (7B, 7C) to generate power. The front stage power generation turbine (9A) and the rear stage power generation turbine (9B, 9C) generate electricity using a rotor shaft (16), rotor blades (23B, 24B) attached to the rotor shaft (16), a generator rotor (81) rotating together with the rotor shaft (16), and a generator stator (82) arranged opposite the generator rotor (81). [Explanation of symbols]

[0100] 1 Cold ORC power generator 2A 1st Rankine cycle (pre-stage Rankine cycle) 2B Second Rankine cycle (post-stage Rankine cycle) 2C 3rd Rankine cycle (post-stage Rankine cycle) 3A 1st heater (first stage heater) 3B 2nd heater (second stage heater) 3C 3rd heater (second stage heater) 5A First Circulation Pump (Preliminary Liquid Pump) 5B Second Circulation Pump (Post-liquid Pump) 5C 3rd Circulation Pump (Later Liquid Pump) 6 Casing 7A First evaporator (pre-evaporator) 7B Second evaporator (post-evaporator) 7C Third evaporator (post-evaporator) 8. Generator 9A First generating turbine (pre-stage generating turbine) 9B Second generating turbine (rear stage generating turbine) 9C Third generating turbine (rear stage generating turbine) 10 LNG source 11A First circulation flow path 11B Second circulation flow path 11C 3rd circulation flow path 12 LNG vaporization path (refrigerant vaporization path) 14 Trim heater 16 rotor shaft 23 First stage axial flow turbine 23A 1st stage stator vane 23B 1st stage rotor blade 24 Second stage axial flow turbine 24A 2nd stage stator vane 24B 2nd stage rotor blade 26 Sealing material 26A One side seal 26B Other side seal part 27A Ball Bearing 27B Ball Bearing 30 Support part 40 Bypass Line 40A Inlet opening 40B Radial extension lead-in section 40B1 Penetration 40C Axial extension 40D radially extending discharge section 40E Exit side opening 61 Inner casing 61A Inner casing member 61A1 Axial extension 61B One side cover member 61C other side cover member 62 Outer casing 63 Working fluid flow path 64A One-side lead-in 64B Other side discharge path 65A Inlet Casing 65B Outlet casing 81 Generator rotor 82 Generator stator 101 Thrust collar 102 Thrust bearing device 102A One-side thrust bearing 102B Other side thrust bearing 103 Radial bearing 103A One side radial bearing 103B Other side radial bearing 111 Shaft section 112A External surface 112B External surface 113A One side disk part 113B Other side disk part 114A One side protrusion 114B Other side protrusion 115A One side nut 115B Other side nut 610 Space 611 Inner surface 612 Outer surface 612A Outer surface 612B Outer surface 621 Inner surface 630A Inner surface 630B Inner surface CA axis

Claims

1. a refrigerant vaporization flow path through which a liquefied refrigerant flows and vaporizes; a first-stage Rankine cycle in which a first-stage working fluid that is an organic fluid circulates; a downstream Rankine cycle in which a downstream working fluid, which is an organic fluid having a boiling point higher than that of the upstream working fluid, is circulated; Equipped with the upstream Rankine cycle includes a upstream heater that uses the upstream working fluid to heat the liquefied refrigerant flowing through the refrigerant vaporization flow passage, a upstream liquid pump that transports the upstream working fluid liquefied in the upstream heater, a upstream evaporator that evaporates the upstream working fluid guided from the upstream liquid pump, and a upstream power generation turbine that is driven by the upstream working fluid vaporized in the upstream evaporator to generate power, the downstream Rankine cycle includes a downstream heater that uses the downstream working fluid to heat the liquefied refrigerant flowing through the refrigerant vaporization flow passage, a downstream liquid pump that transports the downstream working fluid liquefied by the downstream heater, a downstream evaporator that evaporates the downstream working fluid guided from the downstream liquid pump, and a downstream power generation turbine that is driven by the downstream working fluid vaporized in the downstream evaporator to generate power, the post-stage heater is provided between the front-stage liquid pump and the front-stage evaporator so as to exchange heat with the front-stage working fluid; the pre-heater is provided upstream of the post-heater in a flow direction of the liquefied refrigerant flowing through the refrigerant vaporization flow path, The front-stage power generating turbine and the rear-stage power generating turbine are a cold ORC power generating device comprising a rotor shaft, rotor blades attached to the rotor shaft, a generator rotor that rotates together with the rotor shaft, and a generator stator arranged opposite the generator rotor.

2. a refrigerant vaporization flow path through which a liquefied refrigerant flows and vaporizes; a first-stage Rankine cycle in which a first-stage working fluid that is an organic fluid circulates; a downstream Rankine cycle in which a downstream working fluid, which is an organic fluid having a boiling point higher than that of the upstream working fluid, is circulated; A method for operating a cold ORC power generation system comprising: the upstream Rankine cycle includes a upstream heater that uses the upstream working fluid to heat the liquefied refrigerant flowing through the refrigerant vaporization flow passage, a upstream liquid pump that transports the upstream working fluid liquefied in the upstream heater, a upstream evaporator that evaporates the upstream working fluid guided from the upstream liquid pump, and a upstream power generation turbine that is driven by the upstream working fluid vaporized in the upstream evaporator to generate power, the downstream Rankine cycle includes a downstream heater that uses the downstream working fluid to heat the liquefied refrigerant flowing through the refrigerant vaporization flow passage, a downstream liquid pump that transports the downstream working fluid liquefied by the downstream heater, a downstream evaporator that evaporates the downstream working fluid guided from the downstream liquid pump, and a downstream power generation turbine that is driven by the downstream working fluid vaporized in the downstream evaporator to generate power, a first-stage working fluid is heat-exchanged between the first-stage liquid pump and the first-stage evaporator by the second-stage heater; The pre-heater heats the liquefied refrigerant upstream of the post-heater in a flow direction of the liquefied refrigerant flowing through the refrigerant vaporization flow path, A method for operating a cold ORC power generation system in which the front-stage power generation turbine and the rear-stage power generation turbine generate electricity using a rotor shaft, rotor blades attached to the rotor shaft, a generator rotor that rotates together with the rotor shaft, and a generator stator arranged opposite the generator rotor.

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