Organic rankine cycle power generation plant

Abstract

This organic Rankine cycle power generation plant comprises: a circulation line through which an organic medium circulates; an evaporator that is provided to the circulation line and that evaporates the organic medium through heat exchange with a heat medium; at least one turbine generator that includes a turbine driven by the organic medium evaporated by the evaporator and a generator connected to the turbine; a condenser that condenses the organic medium discharged from the turbine through heat exchange with a liquefied natural gas; a pressure ratio information acquisition unit that is configured to acquire pressure ratio information indicating the pressure ratio of the turbine; and a turbine control unit that is configured to control the rotation speed of the turbine on the basis of the pressure ratio information acquired by the pressure ratio information acquisition unit.

Description

Organic Rankine Cycle Power Plant

[0001] This disclosure relates to an organic Rankine cycle power plant. This application claims priority to Japanese Patent Application No. 2024-099600, filed on June 20, 2024, with the Japan Patent Office, the contents of which are incorporated herein by reference.

[0002] Patent Document 1 discloses a Rankine cycle turbine plant equipped with a turbine equipped with a variable nozzle. Patent Document 2 discloses a Rankine cycle device equipped with a pump, an evaporator, an expander, and a condenser provided in a working fluid circuit. In this Rankine cycle device, a generator is connected to the expander, and the generator output when a target pressure difference between the inlet pressure and outlet pressure of the expander is increased by a predetermined value and the generator output when the target pressure difference is decreased by a predetermined value are stored, and the target pressure difference is updated to the target pressure difference that maximizes the power generation output.

[0003] JP 60-013903 A JP 2021-095852 A

[0004] The turbine with a variable nozzle described in Patent Document 1 can suppress efficiency decline by using the variable nozzle, but in a turbine without a variable nozzle, the internal efficiency of the turbine decreases with fluctuations in the turbine pressure ratio. Also, when the expander in the configuration of Patent Document 2 is a turbine, the internal efficiency of the turbine decreases as the speed ratio U / C0, which is the ratio of the peripheral speed U of the turbine rotor blades to the fluid velocity C0, deviates from the optimal speed ratio. Therefore, when the turbine is operating at partial load, even if the turbine rotation speed is changed in accordance with the pressure difference between the turbine inlet pressure and outlet pressure, as in the method described in Patent Document 2, the effect of suppressing declines in the internal efficiency of the turbine is limited.

[0005] In view of the above circumstances, at least one embodiment of the present disclosure aims to provide an organic Rankine cycle power plant configured to drive a turbine connected to a generator with an organic heat medium, which is capable of suppressing a decrease in the internal efficiency of the turbine even when the turbine is operated at a partial load.

[0006] In order to achieve the above object, an organic Rankine cycle power plant according to at least one embodiment of the present disclosure includes: a circulation line through which an organic medium circulates; an evaporator provided in the circulation line and configured to evaporate the organic medium by heat exchange with a heat medium; at least one turbine generator including a turbine driven by the organic medium evaporated in the evaporator and a generator connected to the turbine; a condenser that condenses the organic medium that has left the turbine by heat exchange with liquefied natural gas; a pressure ratio information acquisition unit configured to acquire pressure ratio information indicating a pressure ratio of the turbine; and a turbine control unit configured to control a rotation speed of the turbine based on the pressure ratio information acquired by the pressure ratio information acquisition unit.

[0007] According to at least one embodiment of the present disclosure, there is provided an organic Rankine cycle power plant configured to drive a turbine connected to a generator using an organic heat medium, which is capable of suppressing a decrease in the internal efficiency of the turbine even when the turbine is operated at a partial load.

[0008] 1 is a diagram showing a schematic configuration of an organic Rankine cycle power plant 2 according to an embodiment. FIG. 2 is a diagram showing an example of a detailed configuration of a plurality of turbine generators 10 and their periphery in the plant 2 shown in FIG. 1. FIG. 3 is a diagram showing an example of a hardware configuration of a control device 90. FIG. 4 is a block diagram showing an example of a functional configuration of the control device 90. FIG. 5 is a diagram showing the number of operating turbine generators 10 and the load (%) of each of the turbine generators 10A, 10B, and 10C when the operating load of the plant 2 is 100%. FIG. 6 is a diagram showing the number of operating turbine generators 10 and the load (%) of each of the turbine generators 10A, 10B, and 10C when the operating load of the plant 2 is 75%. FIG. 7 is a diagram showing the number of operating turbine generators 10 and the load (%) of each of the turbine generators 10A, 10B, and 10C when the operating load of the plant 2 is 60%. FIG. 8 is a diagram showing the number of operating turbine generators 10 and the load (%) of each of the turbine generators 10A, 10B, and 10C when the operating load of the plant 2 is 50%. 1 is a diagram showing the number of operating turbine generators 10 and the load (%) of each of the turbine generators 10A, 10B, and 10C when the operating load of the plant 2 is 30%. FIG. 2 is a diagram showing an example of correlation information T indicating the correlation between the operating load of the plant 2, the pressure ratio of the turbine 30, and the rotation speed of the turbine 30 for each of a plurality of turbine generators 10A, 10B, and 10C. FIG. 3 is a diagram showing the relationship between the load of the turbine generator and the internal efficiency of the turbine. FIG. 4 is a diagram showing the relationship between the operating load of the plant 2 and the internal efficiency of the turbine in operation.

[0009] Several embodiments of the present disclosure will be described below with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the invention. For example, expressions expressing relative or absolute arrangements, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such arrangements, but also express relative displacements with a tolerance or angle or distance to the extent that the same function is achieved. For example, expressions expressing the equality of things, such as "same," "equal," and "homogeneous," not only express strict equality, but also express tolerance or differences to the extent that the same function is achieved. For example, expressions expressing shapes such as a square or cylindrical shape not only express shapes such as a square or cylindrical shape in the strict geometric sense, but also express shapes including concave and convex portions, chamfered portions, etc., to the extent that the same effect is achieved. On the other hand, the expressions "comprise," "include," "have," "includes," or "have" of one element are not exclusive expressions that exclude the presence of other elements.

[0010] 1 is a diagram showing a schematic configuration of an organic Rankine cycle power plant 2 (hereinafter simply referred to as "plant 2") according to one embodiment. As shown in Fig. 1, the plant 2 includes a circulation line 4, a pump 6, an organic medium evaporator 8, a plurality of turbine generators 10, an organic medium condenser 12, a seawater line 14, an LNG tank 16, an LNG line 18, and a trim heater 20.

[0011] The circulation line 4 is composed of piping, and an organic medium as a working fluid circulates through the circulation line 4. A low-boiling-point medium with a boiling point lower than that of water is used as the organic medium. The type of organic medium is not particularly limited, but may be, for example, the following substances: Alkanes such as butane, propane, pentane, hexane, heptane, octane, and decane Cyclic alkanes such as cyclopentane and cyclohexane Refrigerants such as R1234zee, R1234yf, R134a, and R245fa Combinations of the above refrigerants

[0012] The pump 6 is provided between the organic medium condenser 12 and the organic medium evaporator 8 in the circulation line 4 , and is configured to pump the organic medium condensed in the organic medium condenser 12 to the organic medium evaporator 8 .

[0013] The organic medium evaporator 8 is provided downstream of the pump 6 in the circulation line 4. The organic medium evaporator 8 is a heat exchanger configured to heat and evaporate the organic medium flowing through the circulation line 4 by heat exchange between the organic medium flowing through the circulation line 4 and seawater as a heat medium flowing through the seawater line 14. The seawater flowing through the seawater line 14 is cooled by heat exchange with the organic medium in the organic medium evaporator 8 and is discharged from the organic medium evaporator 8 as wastewater.

[0014] The plurality of turbine generators 10 are arranged in parallel on the circulation line 4. The circulation line 4 branches into a plurality of lines downstream of the organic medium evaporator 8, each passing through a plurality of turbine generators 10, and then joins together upstream of the organic medium condenser 12.

[0015] In the illustrated example, the multiple turbine generators 10 are three turbine generators 10A, 10B, and 10C. The circulation line 4 branches into three branch lines 4a, 4a, and 4c downstream of the organic medium evaporator 8, with the turbine generator 10A provided in the branch line 4a, the turbine generator 10B provided in the branch line 4b, and the turbine generator 10B provided in the branch line 4c. The three branch lines 4a, 4b, and 4c join together upstream of the organic medium condenser 12.

[0016] In the illustrated example, the circulation line 4 is provided with a bypass line 5 that bypasses the three turbine generators 10 , and the bypass line 5 is provided with a bypass valve 22 .

[0017] The organic media that have exited the turbines (described later) in each of the plurality of turbine generators 10A, 10B, and 10C join together upstream of the organic media condenser 12 and are supplied to the organic media condenser 12.

[0018] The organic medium condenser 12 is provided in the circulation line 4 between the plurality of turbine generators 10 and the pump 6. The organic medium condenser 12 is a heat exchanger configured to cool and condense the organic medium by heat exchange between the organic medium flowing through the circulation line 4 (the organic medium exiting the turbines described below in each of the plurality of turbine generators 10A, 10B, and 10C) and LNG (liquefied natural gas) supplied from an LNG tank 16 as a cold heat source. The LNG flowing through the LNG line 18 is heated and evaporated by heat exchange with the organic medium in the organic medium condenser 12, becoming natural gas, which is supplied to the trim heater 20. The natural gas supplied to the trim heater 20 is further heated by heat exchange with seawater supplied from a branch line 15 branching off from the seawater line 14, and is used as fuel, etc.

[0019] 1 , a flow control valve 19 for adjusting the flow rate of LNG in the LNG line 18 is provided in the LNG line 18 at a position between the LNG tank 16 and the organic medium condenser 12. In addition, a flow meter 45 for measuring the flow rate of LNG in the LNG line 18 is provided in the LNG line 18 at a position between the LNG tank 16 and the organic medium condenser 12.

[0020] Fig. 2 is a diagram showing an example of a detailed configuration of the multiple turbine generators 10 and their surroundings in the plant 2 shown in Fig. 1. As shown in Fig. 2, each of the multiple turbine generators 10A, 10B, and 10C includes a turbine 30 and a generator 32 connected to the turbine 30. An inverter device 34 is connected to the generator 32 of each of the turbine generators 10A, 10B, and 10C. The inverter device 34 includes a converter 36 that converts the AC current output from the generator 32 into DC current, and an inverter 38 that converts the DC current output from the converter 36 into AC current, and converts the frequency of the output of the generator 32 and outputs it to the outside of the plant 2.

[0021] As shown in FIG. 2 , the plant 2 includes a pressure gauge 40A that measures the inlet pressure of the turbine 30 of the turbine generator 10A, a pressure gauge 42A that measures the outlet pressure of the turbine 30 of the turbine generator 10A, a pressure gauge 40B that measures the inlet pressure of the turbine 30 of the turbine generator 10B, a pressure gauge 42B that measures the outlet pressure of the turbine 30 of the turbine generator 10B, a pressure gauge 40C that measures the inlet pressure of the turbine 30 of the turbine generator 10C, and a pressure gauge 42C that measures the outlet pressure of the turbine 30 of the turbine generator 10C.

[0022] 2, the plant 2 includes a control device 90 for controlling the rotation speed of the turbine 30 and the rotation speed of the generator 32 in each of the plurality of turbine generators 10A, 10B, 10C. The control device 90 controls the rotation speed of the turbine 30 and the generator 32 via the inverter device 34 for each of the plurality of turbine generators 10A, 10B, 10C.

[0023] FIG. 3 is a diagram illustrating an example of the hardware configuration of the control device 90. FIG. 4 is a block diagram illustrating an example of the functional configuration of the control device 90. As shown in FIG. 3 , the control device 90 includes, for example, a processor 91, a RAM (Random Access Memory) 92, a ROM (Read Only Memory) 93, a HDD (Hard Disk Drive) 94, an input I / F 96, and an output I / F 98, which are connected to each other via a bus 95. The control device 90 is configured by the computer executing a program that realizes each function of the control device 90. The functions of each part of the control device 90 described below are realized, for example, by loading a program stored in the ROM 93 into the RAM 92 and executing it with the processor 91, and by reading and writing data from and to the RAM 92 and the ROM 93. The hardware that makes up the control device 90 may be integrated into one location or distributed across multiple locations.

[0024] 4, the control device 90 includes an operating load information acquisition unit 50, a pressure ratio information acquisition unit 52, and a turbine control unit 54. The operating load information acquisition unit 50 acquires operating load information S Ｌ Here, the operating load information acquiring unit 50 acquires, for example, the ratio F1 / Fmax between the flow rate F1 of LNG measured by the flow meter 45 (see FIG. 1) and the maximum flow rate Fmax set in advance, as the operating load information S Ｌ Alternatively, the ratio F2 / Fmax of the control command value F2 of the LNG flow rate for the flow rate adjustment valve 19 (see FIG. 1) to the preset maximum flow rate Fmax may be acquired as the operating load information S Ｌ It may be obtained as.

[0025] The pressure ratio information acquisition unit 52 acquires pressure ratio information S indicating the pressure ratio of the turbine 30 for each of the turbine generators 10A, 10B, and 10C. Ｐ Specifically, the pressure ratio information acquisition unit 52 acquires the inlet pressure PAi of the turbine 30 of the turbine generator 10A measured by the pressure gauge 40A and the outlet pressure PAo of the turbine 30 of the turbine generator 10A measured by the pressure gauge 42A, and calculates the ratio PAi / PAo of the inlet pressure PAi to the outlet pressure PAo as the pressure ratio of the turbine 30 of the turbine generator 10A, thereby obtaining the pressure ratio information S of the turbine 30 of the turbine generator 10A. Ｐ Furthermore, the pressure ratio information acquisition unit 52 acquires the inlet pressure PBi of the turbine 30 of the turbine generator 10B measured by the pressure gauge 40B and the outlet pressure PBo of the turbine 30 of the turbine generator 10B measured by the pressure gauge 42B, and calculates the ratio PBi / PBo of the inlet pressure PBi to the outlet pressure PBo as the pressure ratio of the turbine 30 of the turbine generator 10B, thereby obtaining pressure ratio information S ＰFurthermore, the pressure ratio information acquisition unit 52 acquires the inlet pressure PCi of the turbine 30 of the turbine generator 10C measured by the pressure gauge 40C and the outlet pressure PCo of the turbine 30 of the turbine generator 10C measured by the pressure gauge 42C, and calculates the ratio PCi / PCo of the inlet pressure PCi and the outlet pressure PCo as the pressure ratio of the turbine 30 of the turbine generator 10C, thereby obtaining pressure ratio information S Ｐ The ratio PCi / PCo is obtained as:

[0026] The turbine control unit 54 includes an operating unit number determination unit 56, a correlation information reference unit 58, and a rotation speed determination unit 60. A method for determining the number of operating turbine generators 10 by the operating unit number determination unit 56 will be described below with reference to Figures 5A to 5E.

[0027] The operating unit number determination unit 56 determines the number of operating units based on the operating load information S Ｌ The number of operating turbine generators 10 is determined in accordance with the operating load of the plant 2 indicated by the load. Here, the number of operating turbine generators 10 refers to the number of operating turbine generators 10 among the plurality of turbine generators 10A, 10B, and 10C.

[0028] The operating number determination unit 56 is configured to be able to execute a continuous operating number mode in which the number of operating turbine generators 10 is continuously changed according to the operating load of the plant 2, and a skip operating number mode in which the number of operating turbine generators 10 is discontinuously changed according to the operating load of the plant 2.

[0029] 5A to 5E, the load (%) of each of the multiple turbine generators 10A, 10B, 10C in the continuous operating number mode is shown by a solid bar graph, and the load (%) of each of the multiple turbine generators 10A, 10B, 10C in the skip-operating-number-of-units mode is shown by a dotted bar graph. Note that the open bars represent the case where variable speed control (described below) of the turbine 30 is performed, and the hatched bars represent the case where fixed speed control of the turbine 30 is performed (comparative form). That is, the open solid bar represents the case where the continuous operating number mode and variable speed control of the turbine 30 are performed, the open dotted bar represents the case where skip-operating-number mode and variable speed control of the turbine 30 are performed, and the hatched solid bar represents the case where the continuous operating number mode and fixed speed control of the turbine 30 are performed.

[0030] FIG. 5A shows the number of operating turbine generators 10 and the load (%) of each of the turbine generators 10A, 10B, and 10C when the operating load of the plant 2 is 100%. FIG. 5B shows the number of operating turbine generators 10 and the load (%) of each of the turbine generators 10A, 10B, and 10C when the operating load of the plant 2 is 75%. FIG. 5C shows the number of operating turbine generators 10 and the load (%) of each of the turbine generators 10A, 10B, and 10C when the operating load of the plant 2 is 60%. FIG. 5D shows the number of operating turbine generators 10 and the load (%) of each of the turbine generators 10A, 10B, and 10C when the operating load of the plant 2 is 50%. FIG. 5E shows the number of operating turbine generators 10 and the load (%) of each of the turbine generators 10A, 10B, and 10C when the operating load of the plant 2 is 30%.

[0031] First, the continuous operating number mode will be described. As shown in Figures 5A and 5B , in the continuous operating number mode, when the operating load of the plant 2 is between 100% (the maximum load of the plant 2) and a predetermined first predetermined load L1 (e.g., 70%), the operating number determination unit 56 determines the number of operating turbine generators 10 to be three (i.e., the total number of turbine generators 10 included in the plant 2), and uniformly reduces the loads of the multiple turbine generators 10A, 10B, and 10C as the operating load of the plant 2 decreases. For example, when the operating load of the plant 2 is 100% as shown in Figure 5A , the loads of each of the multiple turbine generators 10A, 10B, and 10C are 100%, whereas when the operating load of the plant 2 is 75% as shown in Figure 5B , the loads of each of the multiple turbine generators 10A, 10B, and 10C are 75%, and the loads of the multiple turbine generators 10A, 10B, and 10C are uniformly reduced by 25% from 100%.

[0032] 5C , in the continuous operating unit number mode, when the operating load of the plant 2 is between the first predetermined load L1 and a predetermined second predetermined load L2 (e.g., 30%), the operating unit number determination unit 56 determines the number of operating turbine generators 10 to be two (i.e., the total number of turbine generators 10 included in the plant 2 minus one). In the example shown in FIG. 5C , of the three turbine generators 10A, 10B, and 10C, two (the turbine generators 10A and 10B in the example shown in FIG. 5C ) continue to operate, and one turbine generator 10C is suspended. Therefore, when the operating load of the plant 2 is 60%, the load on the turbine generators 10A and 10B is greater than when the operating load of the plant 2 is 75% (see FIG. 5B ).

[0033] 5C and 5D , in the continuous operating unit number mode, when the operating load of the plant 2 is between the first predetermined load L1 and the second predetermined load L2, the loads of the turbine generators 10A, 10B are uniformly reduced as the operating load of the plant 2 decreases. For example, when the operating load of the plant 2 is 60% as shown in Fig. 5C , the loads of each of the turbine generators 10A, 10B are 90%, whereas when the operating load of the plant 2 is 50% as shown in Fig. 5D , the loads of each of the turbine generators 10A, 10B are 75%, and the loads of the turbine generators 10A, 10B are uniformly reduced by 15% from 90%.

[0034] As shown in Fig. 5E , in the continuous operating number mode, when the operating load of the plant 2 becomes equal to or less than the second predetermined load L2, the operating number determination unit 56 determines the number of operating turbine generators 10 to be one. In the example shown in Fig. 5E , of the three turbine generators 10A, 10B, and 10C, one turbine generator (in the example shown in Fig. 5E , the turbine generator 10A) continues to operate, and the operation of the other two turbine generators 10B and 10C is suspended. Therefore, when the operating load of the plant 2 is 30%, the load on the turbine generator 10A is greater than when the operating load of the plant 2 is 50% (see Fig. 5D ).

[0035] In this way, in a first case in which the operating load of the plant 2 is a load between the maximum load and the first predetermined load L1, the turbine control unit 54 uniformly reduces the loads of the multiple turbine generators 10A, 10B, 10C as the operating load of the plant 2 decreases, and in a second case in which the operating load of the plant 2 is equal to or less than the first predetermined load L1, the turbine control unit 54 reduces the number of operating turbine generators 10 compared to the first case. Furthermore, in the continuous operating number mode, when the operating load of the plant 2 is a load between the first predetermined load L1 and the second predetermined load L2, the turbine control unit 54 uniformly reduces the loads of the multiple turbine generators 10A, 10B as the operating load of the plant 2 decreases, and when the operating load of the plant 2 is equal to or less than the second predetermined load L2, the turbine control unit 54 reduces the number of operating turbine generators 10 compared to when the operating load of the plant 2 is a load between the first predetermined load L1 and the second predetermined load L2.

[0036] Next, the operating-unit-number skip mode will be described. As shown in Figures 5A and 5B , in the operating-unit-number skip mode, when the operating load of the plant 2 is between 100% (maximum load) and a predetermined third predetermined load L3 (e.g., 30%), the operating-unit-number determination unit 56 determines the number of operating turbine generators 10 to be three (i.e., the total number of turbine generators 10 included in the plant 2), and uniformly reduces the loads of the multiple turbine generators 10A, 10B, and 10C as the operating load of the plant 2 decreases. For example, when the operating load of the plant 2 is 100% as shown in Figure 5A , the loads of each of the multiple turbine generators 10A, 10B, and 10C are 100%, whereas when the operating load of the plant 2 is 75% as shown in Figure 5B , the loads of each of the multiple turbine generators 10A, 10B, and 10C are 75%, and the loads of the multiple turbine generators 10A, 10B, and 10C are uniformly reduced by 25% from 100%. 5C, when the operating load of the plant 2 is 60%, the load of each of the multiple turbine generators 10A, 10B, 10C is 60%, and the loads of the multiple turbine generators 10A, 10B, 10C are uniformly reduced by 40% from 100%. Also, as shown in FIG. 5D, when the operating load of the plant 2 is 50%, the load of each of the multiple turbine generators 10A, 10B, 10C is 50%, and the loads of the multiple turbine generators 10A, 10B, 10C are uniformly reduced by 50% from 100%.

[0037] As shown in Fig. 5E , in the operating-unit-number-skip mode, when the operating load of the plant 2 becomes equal to or less than the third predetermined load L3, the operating-unit-number determination unit 56 determines the number of operating turbine generators 10 to be one. In the example shown in Fig. 5E , of the three turbine generators 10A, 10B, and 10C, one turbine generator (in the example shown in Fig. 5E , the turbine generator 10A) continues to operate, and the operation of the other two turbine generators 10B and 10C is suspended. Therefore, when the operating load of the plant 2 is 30%, the load on the turbine generator 10A is greater than when the operating load of the plant 2 is 50% (see Fig. 5D ).

[0038] In this way, in the first case where the operating load of the plant 2 is a load between the maximum load and the third predetermined load L3, the turbine control unit 54 uniformly reduces the loads of the multiple turbine generators 10A, 10B, 10C as the operating load of the plant 2 decreases, and in the second case where the operating load of the plant 2 is equal to or less than the third predetermined load L3, the turbine control unit 54 reduces the number of operating turbine generators 10 by two compared to the first case.

[0039] Furthermore, in order to suppress a decrease in the internal efficiency of the turbine 30 when each of the multiple turbine generators 10A, 10B, 10C is operating at partial load, the turbine control unit 54 performs variable speed control of the turbine 30 for each of the multiple turbine generators 10A, 10B, 10C as described below.

[0040] FIG. 6 shows an example of correlation information T indicating the correlation between the operating load of the plant 2, the pressure ratio of the turbine 30, and the rotation speed of the turbine 30 for each of the multiple turbine generators 10A, 10B, and 10C. Here, the correlation information R common to the three turbine generators 10A, 10B, and 10C will be described using an example in which the three turbine generators 10A, 10B, and 10C have the same configuration. That is, the correlation information T shown in FIG. 6 is used to determine the rotation speed of the turbine 30 for each of the multiple turbine generators 10A, 10B, and 10C. The correlation information T shown in FIG. 6 indicates the relationship between the pressure ratio range of the turbine 30 and the rotation speed of the turbine 30 for each operating load of the plant 2. The correlation information T indicates that the rotation speed of the turbine 30 decreases as the operating load of the plant 2 decreases, and indicates that the rotation speed of the turbine 30 decreases as the pressure ratio of the turbine 30 decreases for each operating load of the plant 2. In the illustrated example, the number of operating turbines 30 is shown together with the rotation speed of the turbine 30, but the number of operating turbines 30 is determined by the operating number determination unit 56 as described above.

[0041] The correlation information reference unit 58 shown in Fig. 4 references the correlation information T shown in Fig. 6. The rotation speed determination unit 60 shown in Fig. 4 uses the operating load information S acquired by the operating load information acquisition unit 50 for each of the plurality of turbine generators 10A, 10B, and 10C. Ｌand the pressure ratio information S acquired by the pressure ratio information acquisition unit 52 Ｐ and the correlation information T referenced by the correlation information reference unit 58, the rotation speed of the turbine 30 is determined. The turbine control unit 54 also controls the rotation speed of the turbine 30 of each of the plurality of turbine generators 10A, 10B, 10C to the rotation speed determined by the rotation speed determination unit 60. A specific example of a method for determining the rotation speed of the turbine 30 for each of the plurality of turbine generators 10A, 10B, 10C using the correlation information T shown in Fig. 6 will be described below.

[0042] For example, the driving load information S acquired by the driving load information acquisition unit 50 Ｌ The operating load of the plant 2 indicated by is 100%, and the pressure ratio information S Ｐ is within the range of 4 to 5, the rotation speed determination unit 60 determines the rotation speed of the turbine 30 of the turbine generator 10A to be 10,000 (rpm), which is the rotation speed of the turbine 30 determined by the operating load of 100% and the pressure ratio of 4 to 5 in the correlation information T referenced by the correlation information reference unit 58. Ｌ The operating load of the plant 2 indicated by is 100%, and the pressure ratio information S Ｐ When the pressure ratio indicated by (i.e., the above-mentioned ratio PBi / PBo) is a value within the range of 4 to 5, the rotation speed determination unit 60 determines the rotation speed of the turbine 30 of the turbine generator 10B to be 10,000 (rpm), which is the rotation speed of the turbine 30 determined by the operating load of 100% and the pressure ratio of 4 to 5 in the correlation information T referenced by the correlation information reference unit 58. Also, when the operating load information S Ｌ The operating load of the plant 2 indicated by is 100%, and the pressure ratio information S Ｐis a value within the range of 4 to 5, the rotation speed determination unit 60 determines the rotation speed of the turbine 30 of the turbine generator 10C to be 10,000 (rpm), which is the rotation speed of the turbine 30 determined by the operating load of 100% and the pressure ratio of 4 to 5 in the correlation information T referenced by the correlation information reference unit 58.

[0043] In addition, for example, in the continuous operating vehicle number mode described with reference to FIGS. 5A to 5E, the driving load information S Ｌ The operating load of the plant 2 indicated by is 60%, and the pressure ratio information S Ｐ is within the range of 4 to 5, the rotation speed determination unit 60 determines the rotation speed of the turbine 30 of the turbine generator 10A to be 9700 (rpm), which is the rotation speed of the turbine 30 determined by the operating load of 60% and the pressure ratio of 4 to 5 in the correlation information T referenced by the correlation information reference unit 58. Also, in the continuous operating unit number mode described with reference to FIGS. 5A to 5E, the operating load information S Ｌ The operating load of the plant 2 indicated by is 60%, and the pressure ratio information S Ｐ is within the range of 4 to 5, the rotation speed determination unit 60 determines the rotation speed of the turbine 30 of the turbine generator 10B to be 9700 (rpm), which is the rotation speed of the turbine 30 determined by the operating load of 60% and the pressure ratio of 4 to 5 in the correlation information T referenced by the correlation information reference unit 58. Note that in the continuous operating unit number mode described with reference to FIGS. 5A to 5E, the operating load information S Ｌ When the operating load of the plant 2 indicated by is 60%, the operation of the turbine generator 10C is stopped.

[0044] In addition, for example, in the operating vehicle number skip mode described with reference to FIGS. 5A to 5E, the driving load information S ＬThe operating load of the plant 2 indicated by is 60%, and the pressure ratio information S Ｐ is within the range of 3 to 4, the rotation speed determination unit 60 determines the rotation speed of the turbine 30 of the turbine generator 10A to be 8500 (rpm), which is the rotation speed of the turbine 30 determined by the operating load of 60% and the pressure ratio of 3 to 4 in the correlation information T referenced by the correlation information reference unit 58. Also, in the operating unit number skip mode described with reference to FIGS. 5A to 5E, the operating load information S Ｌ The operating load of the plant 2 indicated by is 60%, and the pressure ratio information S Ｐ is within the range of 3 to 4, the rotation speed determination unit 60 determines the rotation speed of the turbine 30 of the turbine generator 10B to be 8500 (rpm), which is the rotation speed of the turbine 30 determined by the operating load of 60% and the pressure ratio of 3 to 4 in the correlation information T referenced by the correlation information reference unit 58. Also, in the operating unit number skip mode described with reference to FIGS. 5A to 5E, the operating load information S Ｌ The operating load of the plant 2 indicated by is 60%, and the pressure ratio information S Ｐ is a value within the range of 3 to 4, the rotation speed determination unit 60 determines the rotation speed of the turbine 30 of the turbine generator 10C to be 8500 (rpm), which is the rotation speed of the turbine 30 determined by the operating load of 60% and the pressure ratio of 3 to 4 in the correlation information T referenced by the correlation information reference unit 58.

[0045] The effects of the plant 2 will be described below with reference to Figures 7 and 8. Figure 7 is a diagram showing the relationship between the load on the turbine generator and the internal efficiency of the turbine, with the solid line graph representing the case where the turbine is operated at variable speed (where the turbine speed is reduced as the turbine pressure ratio decreases), and the dashed line graph representing the case where the turbine is operated at fixed speed (where the turbine speed is controlled to a constant value regardless of the turbine pressure ratio).

[0046] As shown in FIG. 7 , when the turbine is operated at variable speed, it is possible to suppress the deterioration of turbine performance due to a decrease in the turbine pressure ratio (a decrease in the load on the turbine generator) even when the turbine is operated at partial load, compared to when the turbine is operated at fixed speed, and it is also possible to suppress the deterioration of the turbine's internal efficiency.

[0047] Furthermore, the internal efficiency of the turbine increases as the speed ratio U / C0, which is the ratio between the peripheral speed U of the turbine rotor blades and the fluid velocity C0 of the fluid flowing into the turbine rotor blades, approaches an optimal speed ratio (a preset design speed ratio). However, the fluid velocity C0 decreases as the turbine pressure ratio decreases. Meanwhile, there is no fixed correlation between the speed ratio U / C0 and the pressure difference across the turbine. Therefore, by controlling the rotation speed of the turbine 30 based on pressure ratio information of the turbine 30, as in the plant 2, the rotation speed of the turbine 30 can be controlled so that the speed ratio U / C0 approaches the optimal speed ratio (design speed ratio), compared to the Rankine cycle system described in Patent Document 2, which changes the turbine rotation speed in accordance with the pressure difference between the turbine's inlet pressure and outlet pressure. Therefore, compared to the configuration described in Patent Document 1, a decrease in the internal efficiency of the turbine 30 can be suppressed even when the turbine 30 is operated at partial load.

[0048] As an additional effect, variable speed operation of the turbine 30 allows the turbine generator 10 to maintain power generation up to a smaller pressure ratio in the turbine 30, thereby expanding the operable range of the turbine generator 10 and enabling earlier start-up (start of providing power). Furthermore, reducing the rotational speed of the turbine 30 when operating the turbine 30 at partial load is also effective in reducing windage loss, which contributes to reducing losses (improving performance) associated with partial load operation of the turbine 30. Furthermore, starting the turbine generator 10 at a rotational speed lower than conventionally reduces losses due to windage loss, thereby reducing the starting power of the turbine generator 10.

[0049] Furthermore, in the plant 2, the number of operating turbine generators 10 changes depending on the operating load of the plant 2, so the fluid velocity C0 changes not only depending on the pressure ratio of the turbine 30 but also depending on the operating load of the plant 2. For this reason, as described above, the operating load information S Ｌ and the pressure ratio information S acquired by the pressure ratio information acquisition unit 52 Ｐ Based on this, by controlling the rotation speed of the turbine 30 of each of the plurality of turbine generators 10A, 10B, 10C so that the speed ratio U / C0 approaches the optimum speed ratio (design speed ratio), it is possible to suppress a decrease in turbine performance even if the operating load of the plant 2 and the pressure ratio of each of the turbines 30 of the plurality of turbine generators 10A, 10B, 10C change, and it is also possible to suppress a decrease in the internal efficiency of the turbine 30.

[0050] Furthermore, by using the correlation information T that associates the pressure ratio range of the turbine 30 with the rotation speed of the turbine 30 for each operating load of the plant 2 as the correlation information T, simpler control can be performed without continuously changing the rotation speed of the turbine 30. Furthermore, hunting can be suppressed.

[0051] In a first case where the operating load of the plant 2 is between the maximum load and a first predetermined load L1, the turbine control unit 54 uniformly reduces the loads of the plurality of turbine generators 10A, 10B, 10C as the operating load of the plant 2 decreases, and in a second case where the operating load of the plant 2 is equal to or less than the first predetermined load L1, the turbine control unit 54 reduces the number of operating turbine generators 10 compared to the first case. Ｐ Since the efficiency reduction associated with partial load operation of the turbine 30 can be suppressed by controlling the rotation speed of the turbine 30 based on the above, it is possible to continue operation of all the turbine generators 10 until the load of the plant 2 reaches a lower load range (without reducing the number of operating turbine generators 10), compared to the case of fixed-speed operation in which the rotation speed of the turbine 30 is fixed. This reduces the frequency of changes in the number of operating turbine generators 10. This reduces the burden on the operator for controlling the number of operating turbine generators 10, and also reduces the risk of plant fluctuations associated with changes in the number of operating turbine generators 10 (for example, the risk of fluctuations in the amount of LNG evaporated in the organic medium condenser 12).

[0052] FIG. 8 is a diagram showing the relationship between the operating load of the plant 2 and the internal efficiency of the turbine 30 during operation. The solid line graph shows the case where variable speed operation of each turbine 30 of the multiple turbine generators 10A, 10B, 10C is performed in the above-mentioned continuous operating unit mode (where the rotation speed of the turbine 30 is reduced as the pressure ratio of the turbine 30 decreases), the dashed line graph shows the case where variable speed operation of each turbine 30 of the multiple turbine generators 10A, 10B, 10C is performed in the above-mentioned skip operating unit mode (where the rotation speed of the turbine 30 is reduced as the pressure ratio of the turbine decreases), and the dashed line graph shows, as a comparative example, the case where fixed speed operation of each turbine 30 of the multiple turbine generators 10A, 10B, 10C is performed.

[0053] In the example shown in Figure 8, the first predetermined load L1 that determines the timing for changing the number of operating turbine generators 10 from three to two in the continuous operating number mode is the same as the load that determines the timing for changing the number of operating turbine generators 10 from three to two when the turbine 30 is operated at a fixed speed (comparative example). In addition, the second predetermined load L2 that determines the timing for changing the number of operating turbine generators 10 from two to one in the continuous operating number mode is the same as the load that determines the timing for changing the number of operating turbine generators 10 from two to one when the turbine 30 is operated at a fixed speed (comparative example). In the example shown in Figure 8, the third predetermined load L3 that determines the timing for changing the number of operating turbine generators 10 from three to one in the skip operating number mode is the same as the second predetermined load L2 that determines the timing for changing the number of operating turbine generators 10 from two to one in the continuous operating number mode.

[0054] 8 , in both the continuous number of operating units mode and the skip number of operating units mode, for each of the multiple turbine generators 10A, 10B, 10C, variable speed operation of the turbine 30 is performed so that the rotation speed of the turbine 30 decreases as the pressure ratio of the turbine 30 decreases, thereby making it possible to suppress a decrease in the internal efficiency of the operating turbine 30 in the process of reducing the load on the plant 2, compared to the comparative example in which fixed speed operation of the turbine 30 is performed. Furthermore, the continuous number of operating units mode can more effectively suppress a decrease in the internal efficiency of the operating turbine 30 in the intermediate load range of the plant 2 than the skip number of operating units mode.

[0055] On the other hand, in the plant 2, in order to ensure the stability and economy of the amount of evaporation of LNG (the amount of natural gas supplied) in the organic medium condenser 12, the plant 2 is basically operated at a high load, and therefore the frequency of operation at an intermediate load is relatively low. Therefore, by operating the plant 2 in the operating unit number skip mode, it is possible to suppress a decrease in the power generation efficiency of the turbine generator 10 while ensuring the stability of the amount of evaporation of LNG (the amount of natural gas supplied). Furthermore, the operating unit number skip mode reduces the frequency of changes in the number of operating turbine generators 10, thereby reducing the burden on the operator for controlling the number of operating turbine generators 10 and reducing the risk of plant fluctuations associated with changes in the number of operating turbine generators 10 (for example, the risk of fluctuations in the amount of evaporation of LNG in the organic medium condenser 12).

[0056] The present disclosure is not limited to the above-described embodiments, but also includes modifications to the above-described embodiments and appropriate combinations of these modifications.

[0057] For example, in the above-described embodiment, the plant 2 is provided with three turbine generators 10A, 10B, and 10C, but the number of turbine generators 10 provided in the plant 2 is not limited, and it is sufficient that the plant 2 includes at least one turbine generator 10. Furthermore, when the number of turbine generators 10 provided in the plant 2 is one, the rotation speed determination unit 60 uses the operating load information S Ｌ When the plant 2 includes one turbine generator 10, the correlation information V indicating the correlation between the pressure ratio of the turbine 30 in the turbine generator 10 and the rotation speed of the turbine 30 may be used instead of the correlation information T used when the plant 2 includes a plurality of turbine generators 10, and the rotation speed determination unit 60 may be configured to determine the rotation speed of the turbine 30 based on the pressure ratio information of the turbine 30 acquired by the pressure ratio information acquisition unit 52 and the correlation information V referenced by the correlation information reference unit 58.

[0058] In addition, the operating unit number determination unit 56 may be configured to be able to change each of the first predetermined load L1, the second predetermined load L2, and the third predetermined load L3 that determine the timing for changing the number of operating turbine generators 10, and these loads L1, L2, and L3 may be changed in accordance with, for example, deterioration of the turbine generators 10 over time, the season, changes in the operating method of the organic medium condenser 12, etc.

[0059] Furthermore, in a case where the plant 2 is equipped with a plurality of turbine generators 10, and the number of turbine generators 10 equipped in the plant 2 is n (here, n is an integer greater than or equal to 2), the turbine control unit 54 may, in the continuous operating number mode, operate n turbine generators 10 in a first case where the operating load of the plant 2 is a load between the maximum load and a first predetermined load L1, and may continue operation of (n-1) turbine generators 10 and suspend operation of one turbine generator 10 when the operating load of the plant 2 changes from the first case to a second case where the operating load is greater than a second predetermined load L2 but equal to or less than the first predetermined load L1.

[0060] Furthermore, in a case where the plant 2 is equipped with a plurality of turbine generators 10, where the number of turbine generators 10 equipped in the plant 2 is defined as n (here, n is an integer greater than or equal to 2), and m is defined as an integer greater than or equal to 2, the turbine control unit 54 may, in the operating unit number skip mode, operate n turbine generators 10 when the operating load of the plant 2 is a load between the maximum load and a third predetermined load L3, and may continue operating (n-m) turbine generators 10 and suspend operation of m turbine generators 10 when the operating load of the plant 2 becomes equal to or less than the third predetermined load L3.

[0061] Furthermore, although the operating number determination unit 56 is configured to be able to execute the continuous operating number mode and the skip operating number mode, the operating number determination unit 56 may be configured to be able to execute only one of the continuous operating number mode and the skip operating number mode (only the continuous operating number mode or only the skip operating number mode).

[0062] Furthermore, since a change in the temperature of the seawater flowing through the seawater line 14 affects the outlet pressure of the turbine 30, the turbine control unit 54Ｌ and pressure ratio information S of the plurality of turbine generators 10 Ｐ In addition, the number of operating turbine generators 10 and the rotation speed of the turbine 30 may be determined taking into consideration the temperature of the seawater flowing through the seawater line 14 .

[0063] The contents described in each of the above embodiments can be understood, for example, as follows.

[0064] [1] An organic Rankine cycle power plant according to at least one embodiment of the present disclosure (e.g., the organic Rankine cycle power plant 2 described above) includes: a circulation line (e.g., the circulation line 4 described above) through which an organic medium circulates; an evaporator (e.g., the organic medium evaporator 8 described above) provided in the circulation line and evaporating the organic medium by heat exchange with a heat medium; at least one turbine generator (e.g., the turbine generator 10 described above) including a turbine (e.g., the turbine 30 described above) driven by the organic medium evaporated in the evaporator and a generator (e.g., the generator 32 described above) connected to the turbine; a condenser (e.g., the organic medium condenser 12 described above) condensing the organic medium discharged from the turbine by heat exchange with liquefied natural gas; a pressure ratio information acquisition unit (e.g., the pressure ratio information acquisition unit 52 described above) configured to acquire pressure ratio information indicating a pressure ratio of the turbine; and a turbine control unit (e.g., the turbine control unit 54 described above) configured to control the rotation speed of the turbine based on the pressure ratio information acquired by the pressure ratio information acquisition unit.

[0065] According to the organic Rankine cycle power plant described in [1] above, compared to a case where the turbine rotation speed is controlled to a constant value (e.g., a rated rotation speed) regardless of the turbine pressure ratio, the deterioration of turbine performance due to changes in the turbine pressure ratio can be suppressed even when the turbine is operated at a partial load, thereby suppressing a deterioration in the turbine's internal efficiency. Furthermore, the turbine's internal efficiency increases as the speed ratio U / C0, which is the ratio between the turbine blade peripheral speed U and the fluid velocity C0 of the fluid flowing into the turbine blade, approaches the optimal speed ratio (design speed ratio). However, the fluid velocity C0 is affected by the turbine pressure ratio, and the fluid velocity C0 decreases as the turbine pressure ratio decreases. Meanwhile, there is no fixed correlation between the speed ratio U / C0 and the turbine pressure difference. Therefore, by controlling the turbine rotation speed based on turbine pressure ratio information as described in (1) above, the turbine rotation speed can be controlled so that the speed ratio U / C0 approaches the optimal speed ratio (design speed ratio), compared to a case where the turbine rotation speed is changed according to the pressure difference between the turbine's inlet pressure and outlet pressure, as in the Rankine cycle system described in Patent Document 2. Therefore, compared to the configuration described in Patent Document 1, it is possible to suppress a decrease in the internal efficiency of the turbine even when the turbine is operated at a partial load.

[0066] In addition to the above effects, the turbine generator can maintain power generation even at a lower pressure ratio in the turbine, thereby expanding the operable range of the turbine generator and enabling it to be put into service sooner (start providing power). Furthermore, reducing the rotational speed when operating the turbine at partial load also has the effect of reducing windage loss, which contributes to reducing losses (improving performance) associated with partial load operation of the turbine. Furthermore, starting the turbine generator at a lower rotational speed than before reduces losses due to windage loss, thereby reducing the starting power of the turbine generator.

[0067] [2] In some embodiments, the organic Rankine cycle power plant described in [1] above further comprises an operating load information acquisition unit (e.g., the above-mentioned operating load information acquisition unit 50) configured to acquire operating load information indicating an operating load of the organic Rankine cycle power plant, wherein the at least one turbine generator is a plurality of turbine generators (e.g., the above-mentioned plurality of turbine generators 10A, 10B, 10C), and the turbine control unit is configured to control the rotation speed of the turbine of each of the plurality of turbine generators based on the operating load information acquired by the operating load information acquisition unit and the pressure ratio information acquired by the pressure ratio information acquisition unit.

[0068] When an organic Rankine cycle power plant includes a plurality of turbine generators, the number of operating turbine generators among the plurality of turbine generators changes depending on the operating load of the plant, and therefore the fluid velocity C0 changes depending not only on the turbine pressure ratio but also on the operating load of the plant. Therefore, as described in [2] above, by controlling the rotation speed of each turbine of the plurality of turbine generators so that the speed ratio U / C0 approaches an optimal speed ratio (design speed ratio) based on the operating load information acquired by the operating load information acquisition unit and the pressure ratio information acquired by the pressure ratio information acquisition unit, it is possible to suppress a decrease in turbine performance even if the operating load of the plant and the turbine pressure ratio change, and it is possible to suppress a decrease in the internal efficiency of the turbine.

[0069] [3] In some embodiments, in the organic Rankine cycle power plant described in [2] above, the turbine control unit includes: a correlation information reference unit (e.g., the above-mentioned correlation information reference unit 58) configured to refer to correlation information indicating a correlation between the operating load, the pressure ratio of the turbine, and a rotation speed of the turbine for each of the plurality of turbine generators; and a rotation speed determination unit (e.g., the above-mentioned rotation speed determination unit 60) configured to determine a rotation speed of the turbine for each of the plurality of turbine generators based on the operating load information acquired by the operating load information acquisition unit, the pressure ratio information acquired by the pressure ratio information acquisition unit, and the correlation information referred to by the correlation information reference unit, and the turbine control unit is configured to control the rotation speed of the turbine of each of the plurality of turbine generators to the rotation speed determined by the rotation speed determination unit.

[0070] According to the organic Rankine cycle power plant described in the above [3], by using correlation information that associates the range of the turbine pressure ratio with the turbine rotation speed for each operating load of the plant as the correlation information, it is possible to perform simpler control without continuously changing the turbine rotation speed, and also to suppress hunting.

[0071] [4] In some embodiments, in the organic Rankine cycle power plant according to any one of [1] to [3] above, the turbine control unit is configured to uniformly reduce the loads of the plurality of turbine generators as the operating load decreases in a first case where the operating load of the organic Rankine cycle power plant is a load between a maximum load and a predetermined load, and to reduce the number of operating turbine generators of the plurality of turbine generators compared to the first case in a second case where the operating load is equal to or less than the predetermined load.

[0072] According to the organic Rankine cycle power plant described in [4] above, by controlling the turbine rotation speed based on the turbine pressure ratio information, it is possible to suppress a decrease in efficiency due to partial load operation of the turbine. Therefore, compared to when the turbine rotation speed is fixed, it is possible to continue operating all of the turbine generators until the plant load reaches a lower range (without reducing the number of operating turbine generators). This reduces the frequency of changes in the number of operating turbine generators. Therefore, it is possible to reduce the burden on operators for controlling the number of operating turbine generators and to reduce the risk of plant fluctuations in the organic Rankine cycle power plant due to changes in the number of operating turbine generators (for example, the risk of fluctuations in the amount of evaporation of liquefied natural gas in the condenser).

[0073] [5] In some embodiments, in the organic Rankine cycle power plant described in [4] above, the plurality of turbine generators are n turbine generators, and the turbine control unit is configured to operate the n turbine generators in the first case, and when the first case changes to the second case, to continue operation of (n-1) turbine generators and suspend operation of one turbine generator.

[0074] According to the organic Rankine cycle power generation plant described in the above [5], it is possible to suppress a decrease in the load of the (n-1) turbine generators that continue to operate by an amount corresponding to the amount of the turbine generators whose operation has been suspended, and therefore it is possible to suppress a decrease in the internal efficiency of the turbines of the (n-1) turbine generators that continue to operate.

[0075] [6] In some embodiments, in the organic Rankine cycle power plant described in [4] above, the plurality of turbine generators are n turbine generators, and when m is defined as an integer equal to or greater than 2, the turbine control unit is configured to operate the n turbine generators in the first case, and when the first case changes to the second case, to continue operation of (n-m) turbine generators and suspend operation of m turbine generators.

[0076] In an organic Rankine cycle power plant that uses the cold energy of liquefied natural gas, in order to ensure the stability and economy of the evaporation rate of liquefied natural gas (the supply rate of natural gas), the plant is basically operated at a high load all the time, and operation at an intermediate load is relatively rare. Therefore, as described in [6] above, when the first case changes to the second case, by continuing to operate the (n-m) turbine generators and suspending the operation of the m turbine generators, it is possible to ensure the stability of the evaporation rate of liquefied natural gas (the supply rate of natural gas) while suppressing a decrease in the power generation efficiency of the turbine generators.

[0077] 2 Organic Rankine cycle power plant 4 Circulation line 4a, 4b, 4c Branch line 5 Bypass line 6 Pump 8 Evaporator 10, 10A, 10B, 10C Turbine generator 12 Condenser 14 Seawater line 15 Branch line 16 Tank 18 LNG line 19 Flow control valve 20 Trim heater 22 Bypass valve 30 Turbine 32 Generator 34 Inverter device 36 Converter 38 Inverter 40A, 40B, 40C, 42A, 42B, 42C Pressure gauge 45 Flow meter 50 Operating load information acquisition unit 52 Pressure ratio information acquisition unit 54 Turbine control unit 56 Operating unit number determination unit 58 Correlation information reference unit 60 Rotation speed determination unit 90 Control device 91 Processor 92 RAM 93 ROM 94 HDD 95 Bus 96 Input I / F 98 Output I / F

Claims

1. An organic Rankine cycle power plant comprising: a circulation line through which an organic medium circulates; an evaporator provided in the circulation line and evaporating the organic medium by heat exchange with a heat medium; at least one turbine generator including a turbine driven by the organic medium evaporated in the evaporator and a generator connected to the turbine; a condenser that condenses the organic medium that has left the turbine by heat exchange with liquefied natural gas; a pressure ratio information acquisition unit configured to acquire pressure ratio information indicating a pressure ratio of the turbine; and a turbine control unit configured to control the rotation speed of the turbine based on the pressure ratio information acquired by the pressure ratio information acquisition unit.

2. The organic Rankine cycle power plant according to claim 1, further comprising an operating load information acquisition unit configured to acquire operating load information indicating an operating load of the organic Rankine cycle power plant, wherein the at least one turbine generator is a plurality of turbine generators, and the turbine control unit is configured to control the rotation speed of the turbine of each of the plurality of turbine generators based on the operating load information acquired by the operating load information acquisition unit and the pressure ratio information acquired by the pressure ratio information acquisition unit.

3. The organic Rankine cycle power plant according to claim 2, wherein the turbine control unit includes: a correlation information reference unit configured to reference correlation information indicating a correlation between the operating load, the pressure ratio of the turbine, and the rotation speed of the turbine for each of the plurality of turbine generators; and a rotation speed determination unit configured to determine a rotation speed of the turbine for each of the plurality of turbine generators based on the operating load information acquired by the operating load information acquisition unit, the pressure ratio information acquired by the pressure ratio information acquisition unit, and the correlation information referenced by the correlation information reference unit; and the turbine control unit is configured to control the rotation speed of the turbine of each of the plurality of turbine generators to the rotation speed determined by the rotation speed determination unit.

4. The organic Rankine cycle power plant according to claim 2, wherein the turbine control unit is configured to uniformly reduce the loads of the plurality of turbine generators as the operating load decreases in a first case in which the operating load of the organic Rankine cycle power plant is a load between a maximum load and a predetermined load, and to reduce the number of operating turbine generators of the plurality of turbine generators compared to the first case in a second case in which the operating load is equal to or less than the predetermined load.

5. The organic Rankine cycle power plant according to claim 4, wherein the plurality of turbine generators are n turbine generators, and the turbine control unit is configured to operate n turbine generators in the first case, and when the first case changes to the second case, to continue operation of (n-1) turbine generators and suspend operation of one turbine generator.

6. The organic Rankine cycle power plant according to claim 4, wherein the plurality of turbine generators is n turbine generators, and when m is defined as an integer equal to or greater than 2, the turbine control unit is configured to operate n turbine generators in the first case, and when a change is made from the first case to the second case, to continue operation of (n-m) turbine generators and to suspend operation of m turbine generators.

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