JP2017223431A - Plant control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plant control device enabling a superheater and a desuperheater to stably control a steam temperature.SOLUTION: According to one embodiment, the plant control device controls a power-generating plant comprising an upstream desuperheater cooling steam; a superheater superheating the steam from the upstream desuperheater; and a downstream desuperheater cooling the steam from the superheater. The plant control device comprises: a first setting section outputting a first setting value for adjusting a first temperature being a temperature of the steam at a first point between the superheater and the downstream desuperheater; and a second setting section outputting a second setting value for adjusting a second temperature being a temperature of the steam at a second point positioned downstream from the downstream desuperheater. The device further comprises: a first control section controlling the upstream desuperheater such that the first temperature is adjusted to be higher than the second setting value by the first setting value; and a second control section controlling the downstream desuperheater such that the second temperature is adjusted to the second setting value.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a plant control apparatus.

  The combined cycle power plant includes a gas turbine, an exhaust heat recovery boiler, and a steam turbine as components. The gas turbine is driven by gas from the combustor. The exhaust heat recovery boiler generates steam using the heat of the exhaust gas discharged from the gas turbine. The steam turbine is driven by steam generated in the exhaust heat recovery boiler. Further, when the steam turbine includes a high pressure turbine and a low pressure turbine, the steam discharged from the exhaust heat recovery boiler is supplied to the high pressure turbine, and the steam discharged from the high pressure turbine is supplied to the low pressure turbine.

  In the combined cycle power plant, it is necessary to control the steam temperature of steam generated in the exhaust heat recovery boiler to a set value. In order to be used for such control, the exhaust heat recovery boiler includes a superheater that superheats steam. The exhaust heat recovery boiler is not only a superheater that superheats the steam supplied from the exhaust heat recovery boiler to the high pressure turbine, but also a superheater that reheats (reheats) the steam supplied from the high pressure turbine to the low pressure turbine. (Heater) may be provided. The superheater in the following sentence shall mean both the former superheater and the latter superheater.

  During normal operation of the combined cycle power plant, when the steam temperature in the exhaust heat recovery boiler is higher than a set value, the steam temperature may exceed the allowable temperature of the piping material. On the other hand, when the steam temperature in the exhaust heat recovery boiler is lower than the set value, the steam temperature of the steam supplied to the steam turbine is lowered, so the power generated in the steam turbine is reduced and the efficiency of the plant is reduced. It will decline.

  Even when the combined cycle power plant is started, the problem is that the steam temperature in the exhaust heat recovery boiler cannot be controlled to the set value. For example, if the steam temperature in the exhaust heat recovery boiler is higher than the set value, the steam temperature in the steam turbine increases, so the temperature difference between the surface and the interior of the steam turbine rotor increases, and the steam turbine has strong heat. Stress is generated. This thermal stress is problematic not only because the steam temperature in the steam turbine is high, but also low. If the steam temperature rapidly changes from a low temperature to a high temperature in the process of increasing the steam temperature during the start-up of the plant, the temperature of the surface of the steam turbine rotor increases while the internal heating of the steam turbine rotor is insufficient. As a result, in the process of increasing the steam temperature during start-up of the plant, the thermal stress of the steam turbine rotor may become stronger than when the steam temperature does not change rapidly from a low temperature to a high temperature.

  Thus, in the combined cycle power plant, it is necessary to control the steam temperature in the exhaust heat recovery boiler to the set value. Therefore, various methods for controlling the steam temperature to the set value are known.

  For example, there is a method of controlling the steam temperature with a temperature reducer. In this case, due to problems such as the allowable temperature of the piping material, a method of increasing the steam temperature with the superheater after lowering the steam temperature with the temperature reducer is used. In other words, this is a technique of installing a temperature reducer in front of the superheater. In this case, when the exhaust gas temperature of the exhaust gas discharged from the gas turbine becomes high, it is difficult to control the steam temperature to the set value by this method.

  On the other hand, there is a method of installing a temperature reducer after the superheater. As described above, when the steam temperature in the exhaust heat recovery boiler is higher than the set value, it becomes a problem that the steam temperature exceeds the allowable temperature of the piping material. For this reason, this method is effective when it is desired to adjust the steam temperature mainly at the start of the plant. That is, when the steam temperature in the exhaust heat recovery boiler is higher than the set value, the steam temperature can be further reduced. However, in this case, measures are required to prevent water droplets sprayed by the temperature reducer from flowing out to the steam turbine without evaporating.

  There is also a method of controlling the steam temperature by mixing steam that bypasses the superheater and steam that has passed through the superheater. Furthermore, there is also a technique for controlling the steam temperature by controlling the exhaust gas temperature in the gas turbine. For example, by controlling the amount of air introduced into the combustor with an IGV (Inlet Guide Vane), the exhaust gas temperature can be lowered, and as a result, the steam temperature can also be lowered.

JP 2012-82971 A

  As described above, in the combined cycle power plant, it is necessary to control the steam temperature in the exhaust heat recovery boiler to a set value, and various methods are known as the control method. However, even if these methods are combined, it is difficult to control the steam temperature sufficiently stably.

  Then, embodiment of this invention makes it a subject to provide the plant control apparatus which can control steam temperature stably with a superheater and a temperature reducer.

  According to one embodiment, the plant controller includes an upstream desuperheater that cools the steam, a superheater that superheats the steam from the upstream desuperheater, and a downstream that cools the steam from the superheater. A power plant including a temperature reducer is controlled. The device includes a first setting unit that outputs a first set value for adjusting a first temperature that is a temperature of the steam at a first point between the superheater and the downstream desuperheater, A second setting unit that outputs a second set value for adjusting a second temperature that is the temperature of the steam at a second point downstream of the downstream desuperheater. The apparatus further includes a first control unit that controls the upstream desuperheater so that the first temperature is adjusted to be higher than the second set value by the first set value, and the second temperature is the second set value. A second control unit that controls the downstream temperature reducer so as to be adjusted to the second set value.

It is a mimetic diagram showing the composition of the power plant of a 1st embodiment. It is a graph for demonstrating operation | movement of the power plant of 1st Embodiment. It is a schematic diagram which shows the structure of the 2nd superheater of 1st Embodiment. It is a flowchart which shows the calculation method of the heat exchange amount of 1st Embodiment. It is a schematic diagram which shows the structure of the control apparatus of 1st Embodiment. Is a graph showing an example of a T ₄ set value of the first embodiment. It is a graph which shows the operation example of the power plant of the comparative example of 1st Embodiment. It is a graph which shows the operation example of the power plant of 1st Embodiment. It is a schematic diagram which shows the structure of the power plant of the modification of 1st Embodiment. It is a schematic diagram which shows the structure of the power plant of 2nd Embodiment. It is a graph for demonstrating operation | movement of the power plant of 2nd Embodiment. It is a schematic diagram which shows the structure of the control apparatus of 2nd Embodiment. It is a schematic diagram which shows the structure of the 1st bypass control part of 2nd Embodiment. It is a graph which shows the operation example of the power plant of 2nd Embodiment. It is a schematic diagram which shows the structure of the power plant of the modification of 2nd Embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 15, the same or similar components are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment)
Drawing 1 is a mimetic diagram showing the composition of the power plant of a 1st embodiment. The power plant in FIG. 1 is a combined cycle thermal power plant using an exhaust heat recovery system.

  The power plant in FIG. 1 includes a gas turbine 1, a compressor 2, a first generator 3, an exhaust gas pipe 4, an exhaust heat recovery boiler 5, a drum 11, a downcomer pipe 12, an evaporator 13, First superheater 14, first temperature reducer 15, second superheater 16, second temperature reducer 17, first temperature reducer valve 18, second temperature reducer valve 19, and control device 20, a main steam pipe 21, a main steam valve 22, a bypass steam pipe 23, a bypass steam valve 24, a steam turbine 25, and a second generator 26. The first temperature reducer 15, the second superheater 16, the second temperature reducer 17, the first temperature reducer valve 18, the second temperature reducer valve 19, and the control device 20 are respectively an upstream temperature reducer and a superheater. It is an example of a downstream temperature reducer, a 1st valve, a 2nd valve, and a plant control apparatus. The control device 20 controls various operations of the power plant of FIG.

This power plant further comprises a steam channel L ₁ between the drum 11 and the first superheater 14, the steam path L ₂ between the first superheater 14 and the first desuperheater 15, the first It includes a desuperheater 15 a steam flow path L ₃ between the second superheater 16, the second superheater 16 and the steam channel L ₄ between the second desuperheater 17.

This power plant further comprises a thermometer 31 and a flow meter 32 provided in the exhaust gas pipe 4, a pressure gauge 41 provided in the drum 11, a flow meter 42 provided in the steam channel L _1, steam channel A thermometer 43 provided in L ₂ , a thermometer 44 provided in the steam flow path L ₃ , a thermometer 45 provided in the steam flow path L ₄ , and a pressure gauge 46 provided in the main steam pipe 21. A thermometer 47 and a flow meter 48.

  The power plant further includes a pressure gauge 51, a thermometer 52, and a flow meter 53 provided in a water flow path for transporting water to the first temperature reducer 15 via the first temperature reducer valve 18. The power plant further includes a pressure gauge 54, a thermometer 55, and a flow meter 56 provided in a water flow path for transporting water to the second temperature reducer 17 via the second temperature reducer valve 19. The power plant further includes a rotational speed measuring device 57 provided in the steam turbine rotor of the steam turbine 25 and an electrical output measuring device 58 provided in the second generator 26.

  In the power plant shown in FIG. 1, the compressor 2 supplies compressed air to a combustor disposed between the compressor 2 and the gas turbine 1, and the combustor burns fuel using the compressed air. As a result, high-temperature and high-pressure gas is generated in the combustor and supplied to the gas turbine 1. The gas turbine 1 is rotated by the gas, thereby rotating the gas turbine rotor. The first generator 3 generates power using the rotation of the gas turbine rotor. The exhaust gas discharged from the gas turbine 1 is sent to the exhaust heat recovery boiler 5 through the exhaust gas pipe 4. The exhaust gas sent to the exhaust heat recovery boiler 5 uses the heat in the order of the second superheater 16, the first superheater 14, and the evaporator 13, and is discharged from the exhaust heat recovery boiler 5.

  The state of the exhaust gas is controlled by the control device 20. For example, the control device 20 can control the exhaust gas temperature and the exhaust gas pressure at the exhaust gas inlet and the exhaust gas outlet of the exhaust heat recovery boiler 5 to set values by controlling the operations of the gas turbine 1 and the exhaust heat recovery boiler 5. .

On the other hand, the water in the drum 11 is sent to the evaporator 13 in the exhaust heat recovery boiler 5 through the downcomer 12 and is heated by the heat of the exhaust gas in the evaporator 13 to become saturated steam. The steam is sent to the first superheater 14 of the exhaust heat recovery boiler 5 through a steam channel L _1, after being superheated in the first superheater 14, a first down through the steam channel L ₂ It is sent to the warmer 15 and cooled by the first warmer 15. The first temperature reducer 15 cools the steam with water from the first temperature reducer valve 18. Cooling steam in the first desuperheater 15 are sent to the second superheater 16 in the exhaust heat recovery boiler 5 through a steam channel L _3, after being superheated again by the second superheater 16, steam It is sent to the second temperature reducer 17 via the flow path L ₄ and cooled again by the second temperature reducer 17. The second temperature reducer 17 cools the steam with water from the second temperature reducer valve 19.

  The state of the steam is controlled by the control device 20. For example, the control device 20 adjusts the opening degree of the first temperature reducer valve 18 and adjusts the flow rate of the spray water in the first temperature reducer 15, thereby adjusting the outlet steam temperature of the second superheater 16. Can be controlled to set value. Further, the control device 20 adjusts the opening degree of the second temperature reducer valve 19 and adjusts the flow rate of the spray water in the second temperature reducer 17 so that the outlet steam temperature of the second temperature reducer 17 is adjusted. Can be controlled to a set value.

  Specifically, the first temperature reducer 15 can control the outflow steam to a state in which the enthalpy of the spray water and the enthalpy of the inflow steam are added at a flow rate ratio by mixing the spray water with the inflow steam. . However, the first temperature reducer 15 of the present embodiment does not control the steam temperature below a predetermined temperature (a temperature obtained by adding a certain margin temperature to the saturated steam temperature). In addition, since the flow rate of the spray water in the first temperature reducer 15 has an upper limit, the range in which the steam temperature can be controlled is determined depending on this upper limit. The same applies to the second temperature reducer 17.

  In addition, the 2nd superheater 16 of this embodiment is a superheater located in the last stage of the waste heat recovery boiler 5 with respect to the flow of steam. The first temperature reducer 15 is positioned upstream of the second superheater 16 with respect to the steam flow, and the second temperature reducer 17 is positioned downstream of the second superheater 16 with respect to the steam flow. doing.

  The steam (main steam) cooled by the second temperature reducer 17 is sent to the steam turbine 25 via the main steam pipe 21. The steam turbine 25 is rotationally driven by the steam to rotate the steam turbine rotor. The second generator 26 generates power using the rotation of the steam turbine rotor. The bypass steam pipe 23 branches from the main steam pipe 21 upstream of the steam turbine 25. A main steam valve 22 is provided in the main steam pipe 21. A bypass steam valve 24 is provided in the bypass steam pipe 23.

  The state of the steam supplied from the exhaust heat recovery boiler 5 is controlled by the control device 20. For example, the control device 20 can control the steam pressure and the steam flow rate at the steam inlet of the steam turbine 25 to set values by adjusting the opening of the main steam valve 22 and the bypass steam valve 24.

  The control device 20 controls the rotational speed of the steam turbine 25 by adjusting the steam flow rate at the steam inlet of the steam turbine 25, thereby controlling the electrical output of the second generator 26 to a set value. The electrical output of the second generator 26 is also called MW (megawatt) output. The rotational speed of the steam turbine 25 is measured by the rotational speed measuring device 57, and the electrical output of the second generator 26 is measured by the electrical output measuring device 58.

  FIG. 2 is a graph for explaining the operation of the power plant according to the first embodiment.

The horizontal axis in FIG. 2 indicates the distance between each point on the steam flow path and the drum 11. The vertical axis in FIG. 2 indicates the temperature of the steam flowing through the steam flow path. Reference numeral T ₁ indicates the temperature of the steam flowing through the steam flow path L ₂ and is measured by the thermometer 43. Symbol T ₂ indicates the temperature of the steam flowing through the steam flow path L ₃ , and is measured by the thermometer 44. Reference numeral T ₃ indicates the temperature of the steam flowing through the steam flow path L ₄ , and is measured by the thermometer 45. Reference numeral T ₄ indicates the temperature of the steam flowing through the main steam pipe (main steam flow path) 21 and is measured by the thermometer 47. FIG. 2 shows the measured values of the steam temperatures T _{1 to} T ₄ by these thermometers 43, 44, 45, 47.

Hereinafter, how to calculate the steam temperature _T 1 through T _4.

Steam temperature T ₂ is an inlet steam temperature of the outlet steam temperature and the second superheater 16 in the first desuperheater 15 is given by the following equation (1) and (2).
T ₂ = HPT (H _T2 , P _T2 ) (1)
H _T2 = {F _S1 × TPH (T _S1 , P _S1 ) + F _T1 × TPH (T ₁ , P _T1 )}
/ (F _T1 + F _S1 ) (2)
However, T ₁ , P _T1 , and FT ₁ represent the temperature, pressure, and flow rate of the steam flowing through the point of the thermometer 43. F _T1 is equal to the flow rate F ₁ of the steam flowing through the flow meter 42. T _{2, P T2, H} T2 represents the temperature of the steam flowing through the point of the thermometer 44, the pressure, the enthalpy. P _S1 , T _S1 , and F _S1 represent the pressure, temperature, and flow rate of the spray water flowing through the points of the pressure gauge 51, the thermometer 52, and the flow meter 53, respectively. HPT is a function for calculating the temperature of steam from the enthalpy of steam (first argument) and pressure (second argument). TPH is a function for calculating the enthalpy of steam from the temperature (first argument) and pressure (second argument) of steam. The units of pressure, temperature, and flow rate are MPa, ° C, and t / h.

The steam temperature T ₃ that is the outlet steam temperature of the second superheater 16 and the inlet steam temperature of the second desuperheater 17 is given by the following equations (3) and (4).
T ₃ = Func (T _G , F _G , T ₂ , F _T2 ) (3)
F _T2 = F _T1 + F _S1 (4)
However, T ₂ and _{FT 2} represent the temperature and flow rate of the steam flowing through the point of the thermometer 44. T ₃ represents the temperature of the steam flowing through the point of the thermometer 45. T _G and F _G represent the temperature and flow rate of the exhaust gas flowing through the points of the thermometer 31 and the flow meter 32, respectively. Func is the second superheater from the inlet exhaust gas temperature (first argument), the inlet exhaust gas flow rate (second argument), the inlet steam temperature (third argument), and the inlet steam flow rate (fourth argument) of the second superheater 16. 16 is a function for calculating 16 outlet steam temperatures. Func calculates the outlet steam temperature from the amount of heat exchange between the exhaust gas and steam in the second superheater 16, as will be described later.

Steam temperature T ₄ is an outlet steam temperature of the second desuperheater 17 is given by the following equation (5) to (7).
T ₄ = HPT (H _T4 , P _T4 ) (5)
H _T4 = {F _S2 × TPH (T _S2 , P _S2 ) + F _T3 × TPH (T ₃ , P _T3 )}
/ (F _T3 + F _S2 ) (6)
F _T3 = F _T2 (7)
However, T ₃ , P _T3 , and FT ₃ represent the temperature, pressure, and flow rate of the steam flowing through the point of the thermometer 45. T _{4, P T4, H} T4 represents a temperature of the steam flowing through the point of the thermometer 47, the pressure, the enthalpy. P _T4 is equal to the pressure P ₂ of the steam flowing through the point of the pressure gauge 46. P _S2 , T _S2 , and F _S2 represent the pressure, temperature, and flow rate of the spray water flowing through the points of the pressure gauge 54, the thermometer 55, and the flow meter 56, respectively.

In equations (1) to (7), it is assumed that the pressure loss in the steam channel is almost zero. The control device 20 can calculate the value of the left side of the equations (1) to (7) by substituting the measured value acquired from the thermometers 43 to 45 or the like into the right side of the equations (1) to (7). it can. If measurement error such as the pressure loss and temperature gauge 43 to 45 is small, it is possible to calculate accurately the value of the steam temperature T ₂ through T ₄ from these equations.

  Next, with reference to FIG. 3 and FIG. 4, a method of calculating the Func in the expression (3) will be described.

  FIG. 3 is a schematic diagram showing the configuration of the second superheater 16 of the first embodiment. FIG. 3 shows a state of heat exchange between exhaust gas and steam.

The symbol Q represents the heat exchange amount [kW] between the exhaust gas and the steam in the second superheater 16. Code _{t IN} denotes an inlet steam temperature of the second superheater 16, corresponding to the steam temperature _{T 2.} The symbol t _OUT represents the outlet steam temperature of the second superheater 16 and corresponds to the steam temperature T ₃ . Code _{T IN} represents an inlet exhaust gas temperature of the second superheater 16, which corresponds to the exhaust gas temperature _{T G.} The code T _OUT represents the outlet exhaust gas temperature of the second superheater 16.

The relationship of the following formula (8) is established between the steam temperatures t _IN and t _OUT . Further, the exhaust gas temperature _{T IN,} between _{T OUT} is holds the relationship of the following equation (9).
t _OUT = t _IN + Q / c / f (8)
T _OUT = T _IN −Q / C / F (9)
Here, c represents the specific heat of steam [kW / ° C./kg], and f represents the flow rate of steam [kg / s]. C represents the specific heat of the exhaust gas [kW / ° C./kg], and F represents the flow rate [kg / s] of the exhaust gas. For example, when the heat exchange amount Q is determined, it is possible to calculate the set value of the inlet steam temperature t _IN from the measured value of the outlet steam temperature t _OUT using Equation (8).

  FIG. 4 is a flowchart illustrating a method for calculating the heat exchange amount Q according to the first embodiment.

First, an exhaust gas temperature T _OUT and a steam temperature t _OUT are assumed (step S1). Next, the heat transfer coefficient h [kW / ° C.] of the second superheater 16 is calculated (step S2). In the present embodiment, it is assumed that the heat transfer coefficient h is a constant value.

Next, a heat release amount Q ₁ [kW] of exhaust gas and a heat recovery amount Q ₂ [kW] of steam are calculated (steps S3 and S4). Heat radiation amount _{Q 1} is given by the following equation (10). Heat absorption _{Q 2} is given by the following equation (11).
Q ₁ = (T _IN −T _OUT ) × C × F (10)
Q ₂ = h {(T _IN −t _OUT ) − (T _OUT −t _IN )}
/ Log {(T _IN -t _OUT ) / (T _OUT -t _IN )} (11)
Here, if the assumptions of the exhaust gas temperature T _OUT and the steam temperature t _OUT are correct, the heat dissipation amount Q ₁ and the heat recovery amount Q ₂ coincide with each other from the energy conservation law. Therefore, comparing the absolute value of the difference between the heat radiation amount Q _1, heat absorption Q ₂ with the threshold value epsilon (step S5).

If the absolute value | Q ₁ −Q ₂ | is larger than the threshold value ε, the exhaust gas temperature T _OUT and the steam temperature t _OUT are corrected (step S6). Then the method repeats step S2~S5 using the modified exhaust gas temperature _{T OUT} and the steam temperature _{t OUT.}

On the other hand, when the absolute value | Q ₁ −Q ₂ | is smaller than the threshold value ε, the heat release amount Q ₁ calculated in step S3 (or the heat recovery amount Q ₂ calculated in step S4) is used as the heat exchange amount Q. decide. In this way, the heat exchange amount Q of the second superheater 16 can be calculated, and thereby the function Func can be calculated. At this time, the control device 20 can search the target temperature of the exhaust gas temperature T _IN at which the steam temperature t _OUT becomes the target temperature by changing the exhaust gas temperature T _IN and repeatedly executing this method.

(1) Control device 20 of the first embodiment
FIG. 5 is a schematic diagram illustrating a configuration of the control device 20 according to the first embodiment.

  The control device 20 includes a first setting unit 61, a second setting unit 62, an adder 63, an upper limit value setting unit 64, a margin value setting unit 65, a subtractor 66, a selection unit 67, A temperature reducer control unit 68 and a second temperature reducer control unit 69 are provided. The first and second cooler controllers 68 and 69 are examples of the first and second controllers, respectively. FIG. 5 shows the components related to the control of the steam temperature among the components of the control device 20.

  The control device 20 may be realized by a computer or an electric circuit mounted on a single hardware, or may be realized by a computer or an electric circuit mounted on a plurality of hardware. In the latter case, the control device 20 controls the power plant while communicating with each other between the hardware. It is assumed that the control device 20 of this embodiment is realized by a single piece of hardware. However, the following description is also applicable to the control device 20 realized by a plurality of hardware.

The first setting unit 61 holds a T ₄ negative deviation allowable value as a setting value for adjusting the steam temperature T ₃ at the point of the thermometer 45. The point of the thermometer 45 is an example of a first point between the superheater and the downstream temperature reducer. Steam temperature T ₃ is an example of the first temperature. T ₄ negative deviation allowable value is an example of a first set value.

The T ₄ negative deviation allowable value is a set value for adjusting the steam temperature T ₃ in relation to the set value of the steam temperature T ₄ . The T ₄ negative deviation allowable value of this embodiment is 10 ° C., and is a constant that does not change with time.

The second setting unit 62 holds a T ₄ set value as a set value for adjusting the steam temperature T ₄ at the point of the thermometer 47. The point of the thermometer 47 is an example of a second point downstream of the downstream desuperheater. Steam temperature T ₄ is an example of the second temperature. T ₄ set value is an example of the second set value.

The T ₄ set value is a set value for adjusting the steam temperature T ₄ . As shown in FIG. 6, the T ₄ set value of the present embodiment changes according to time.

FIG. 6 is a graph illustrating an example of the T ₄ set value according to the first embodiment.

The second setting portion 62 holds the time series values of T ₄ set value as shown in FIG. Therefore, the T ₄ set value output from the second setting unit 62 changes with the passage of time. Figure 6 shows an example of a T ₄ set value at the time of activation of the power plant.

  Hereinafter, the configuration of the control device 20 will be described with reference to FIG. 5 again.

The adder 63 acquires the T ₄ negative deviation allowable value output from the first setting unit 61 and the T ₄ set value output from the second setting unit 62. The adder 63 adds of _{T 4} negative deviation tolerance to _{T 4} set value, outputs the _{T 3} set value _{(T 3} set value = _{T 4} set value + _{T 4} negative deviation tolerance).

Upper limit value setting unit 64, the upper limit of the steam temperature of the power plant, specifically, as the upper limit of the steam temperature T _4, holds a 550 ° C.. The margin value setting unit 65 holds 3 ° C. as the margin value of this upper limit value. This is to prevent reliably that the steam temperature T ₄ is greater than the upper limit, instead of limiting the steam temperature T ₄ 550 ° C. The (upper limit) on the basis, the steam temperature T ₄ 547 ° C. (maximum value - margin Value) as a reference.

The subtractor 66 acquires the upper limit value output from the upper limit value setting unit 64 and the margin value output from the margin value setting unit 65. The subtractor 66 subtracts the margin value from the upper limit value, and outputs the modified upper limit of the steam temperature T ₄ (modified upper limit value = upper limit - margin value).

The selection unit 67 acquires the T ₃ set value output from the adder 63 and the corrected upper limit value output from the subtractor 66. The selector 67 outputs the lower value of the corrected upper limit value T ₃ set value. This is because of preventing that the steam temperature T ₃ exceeds the upper limit value, is to prevent the steam temperature T ₄ is greater than the upper limit.

The selection unit 67 may output the lower one of the T ₃ set value and the upper limit value (550 ° C.) instead of outputting the lower one of the T ₃ set value and the corrected upper limit value (547 ° C.). That is, in this embodiment, the margin value (3 ° C.) may or may not be adopted. Both the former correction upper limit value and the latter upper limit value are examples of limit values. In the latter case, the margin value setting unit 65 and the subtraction unit 66 are unnecessary. On the other hand, in the former case, the upper limit value setting unit 64, the margin value setting unit 65, and the subtractor 66 may be replaced with a correction upper limit value holding unit that holds the correction upper limit value.

The first temperature reducer control unit 68 controls the first temperature reducer 15 so that the steam temperature T ₃ is adjusted to the lower of the T ₃ set value and the corrected upper limit value. Specifically, the first temperature reducer control unit 68 calculates and outputs the opening instruction value Z _S1 of the first temperature reducer valve 18 based on the lower one. As a result, the opening degree of the first temperature reducer valve 18 is adjusted to the opening degree instruction value Z _S1 , and the steam temperature T ₃ approaches the lower one of the T ₃ set value and the corrected upper limit value.

The first temperature reducer control unit 68 controls the first temperature reducer 15 by, for example, PID (Proportional-Integral-Derivative) control. Specifically, first desuperheater control unit 68 obtains the measured value of the steam temperature T ₃ from the thermometer 45, calculates the deviation between the lower and the measured value of T ₃ set value corrected upper limit value Then, the opening instruction value Z _S1 is set so that the deviation approaches zero.

The second temperature reducer control unit 69 controls the second temperature reducer 17 so that the steam temperature T ₄ is adjusted to the T ₄ set value. Specifically, the second desuperheater control unit 69, based on the T ₄ set value, calculates and outputs the opening degree command value Z _S2 of the second desuperheater valve 19. Thus, the degree of opening of the second desuperheater valve 19 is adjusted to the opening degree instruction value Z _S2, steam temperature T ₄ approaches the T ₄ setting.

For example, the second temperature reducer control unit 69 controls the second temperature reducer 17 by PID control. Specifically, first desuperheater control unit 69 obtains the measured value of the steam temperature T ₄ from the thermometer 47 calculates the deviation between the measured value and T ₄ set value, the deviation to zero The opening instruction value Z _S2 is set so as to approach.

Note that the control device 20 of the present embodiment operates at a regular cycle. The operation cycle of the control device 20 is, for example, 1 second. In this case, the opening instruction values Z _S1 and Z _S2 are updated every second.

Here, the T ₄ negative deviation allowable value of the first setting unit 61 will be described in detail.

The thermometer 45 measures the steam temperature T ₃ that is the inlet steam temperature of the second temperature reducer 17, and the thermometer 47 measures the steam temperature T ₄ that is the outlet steam temperature of the second temperature reducer 17. If the vapor temperature T ₃ higher than T ₄ set value, second desuperheater 17, the temperature of the steam taken by lowering the cooling from T _3, the steam temperature T ₄ to T ₄ set value Can be adjusted. On the other hand, if the steam temperature T ₃ lower than T ₄ set value, second desuperheater 17, it is impossible to adjust the steam temperature T ₄ to T ₄ setting. Reason, second desuperheater 17 is because it is impossible to raise the superheat temperature of the steam taken from the T _3.

This problem can be avoided by maintaining the steam temperature T ₃ higher than the T ₄ set value. Therefore, in this embodiment, T ₃ set value to be set higher than T ₄ set value is set to a negative deviation of T ₄ setting for T ₃ set value (T ₄ set value -T ₃ Setting value <0). Therefore, the T ₃ set value of this embodiment is set to the sum of the T ₄ set value and the T ₄ negative deviation allowable value. _{(T 3} set value = _{T 4} set value + _{T 4} negative deviation tolerance). T ₄ negative deviation allowable value is a positive value, for example, 10 ° C.. Thus, it is possible to set the deviation of T ₄ setting for T ₃ set value to a negative constantly.

In this case, the steam temperature _{T 3} is adjusted to be higher 10 ° C. than the vapor temperature _{T 4.} Therefore, prior to the steam temperature T ₄ reaches the upper limit value, the steam temperature T ₃ would reach the upper limit. Therefore, in this embodiment, ₃ setpoint steam temperature T ₃ T and the upper limit value (specifically, corrected upper limit value) is adjusted based on the. Thereby, it becomes possible to prevent the steam temperature of the power plant from reaching the upper limit value.

(2) Operation of Power Plant of First Embodiment and Comparative Example FIG. 7 is a graph showing an operation example of the power plant of the comparative example of the first embodiment. The power plant of the comparative example has the same configuration as the power plant of the present embodiment, but the T ₄ negative deviation allowable value of the comparative example is set to 0 ° C.

Figure 7 is a period _{R 1} earlier than time _{t 1,} the time _t 1 ~t the period _{R 2} of _2, the time _t 2 and the period _{R 3} of ~t _3, the period _{R 4} later than the time _{t 3} The operation example of the power plant in is shown.

In the period R ₁ , the spray flow rate F _S1 at the point of the flow meter 53 and the spray flow rate F _S2 at the point of the flow meter 56 are both set to zero. Accordingly, the steam temperature T ₂ is the same value as the steam temperature T _1, rises with time. Similarly, steam temperature T ₄ is the same value as the steam temperature T _3, rises with time.

In the period _{R 2,} spray flow _{F S1} is set to a constant value. As a result, the steam temperature T ₂ is slowly decrease or increase. On the other hand, than the decrease rate of the steam temperature at the first desuperheater 15 towards the rising speed of the steam temperature in the second superheater 16 fast, steam temperature T ₃ is rises with time. Further, since the T ₄ set value is maintained at a constant value (400 ° C.) in the first half of the period R ₂ (see FIG. 6), the spray flow rate F _S2 is set so that the steam temperature T ₄ is maintained at 400 ° C. Adjusted. Thereafter, the T ₄ set value gradually increases from 400 ° C. in the latter half of the period R ₂ (see FIG. 6). Therefore, the spray flow rate F _S2 decreases with time, and the steam temperature T ₄ increases with time. Go.

Steam temperature _{T 4} in the second half of the period _{R 2} that is sharply higher than the steam temperature _{T 3,} in the period _{R 3,} steam temperature _{T 4} has reached the steam temperature _{T 3} (arrow _A 1). This is because the T ₄ negative deviation allowable value of the comparative example is set to 0 ° C., and the T ₃ set value is equal to the T ₄ set value. In this case, since it is adjusted so that the steam temperature T ₃ and the steam temperature T ₄ approaches both T ₄ set value, there is a case where the steam temperature T ₃ lower than T ₄ setting. In this case, the second desuperheater 17, it is not possible to raise the temperature of the vapor taken, it is impossible to adjust the steam temperature T ₄ to T ₄ setting. Accordingly, the steam temperature T ₄ can not exceed the steam temperature T _3. (Arrow A ₁ ). As a result, in the period R ₃ , a divergence occurs between the steam temperature T ₄ and the T ₄ set value.

In the period R ₄ , the steam temperature T ₃ has reached the corrected upper limit value (547 ° C.). As a result, the steam temperature T ₃ is maintained at 547 ° C., and the steam temperature T ₄ is also maintained at 547 ° C. The spray flow rate F _S1 is adjusted to maintain the vapor temperature T ₃ at 547 ° C. Meanwhile, since the steam temperature _{T 3} and the steam temperature _{T 4} is adjusted to both 547 ° C., spray flow _{F S2} is maintained substantially zero. The spray flow rate F _S2 increases from 0 only when the vapor temperature T ₄ becomes higher than 547 ° C.

FIG. 8 is a graph illustrating an operation example of the power plant according to the first embodiment. The T ₄ negative deviation allowable value of the comparative example is set to 0 ° C., whereas the T ₄ negative deviation allowable value of the present embodiment is set to 10 ° C.

In the period R ₁ , the spray flow rates F _S1 and F _S2 are set to zero. Accordingly, the steam temperature T ₂ is the same value as the steam temperature T _1, rises with time. Similarly, steam temperature T ₄ is the same value as the steam temperature T _3, rises with time.

In the period R ₂ , the spray flow rate F _S1 is initially set to a constant value (arrow B ₁ ). As a result, the steam temperature T ₂ is slowly decrease or increase. On the other hand, than the decrease rate of the steam temperature at the first desuperheater 15 towards the rising speed of the steam temperature in the second superheater 16 fast, steam temperature T ₃ is rises with time. Further, since the T ₄ set value is maintained at a constant value (400 ° C.) in the first half of the period R ₂ (see FIG. 6), the spray flow rate F _S2 is set so that the steam temperature T ₄ is maintained at 400 ° C. Adjusted. Thereafter, the T ₄ set value gradually increases from 400 ° C. in the latter half of the period R ₂ (see FIG. 6), so the steam temperature T ₄ increases with time.

However, the T ₄ negative deviation allowable value of this embodiment is set to 10 ° C., and the T ₃ set value is higher than the T ₄ set value. As a result, even if increased steam temperature _{T 4} in the second half of the period _{R 2,} steam temperature _{T 4} does not reach the steam temperature _{T 3} in the period _{R 3} (arrow _A 2). Thus, the second desuperheater 17 in the present embodiment, it is possible to adjust the steam temperature T ₄ in the period R ₃ to T ₄ setting value, is divergence between the steam temperature T ₄ and T ₄ set value Generation | occurrence | production can be suppressed. In the periods R ₂ and R ₃ , the spray flow rate F _S1 is adjusted so that the steam temperature T ₃ approaches the T ₃ set value (= T ₄ set value + T ₄ negative deviation allowable value) (arrows B ₂ and B _3). ). Similarly, the spray flow rate F _S2 is adjusted so that the steam temperature T ₄ approaches the T ₄ set value.

It should be noted that the spray flow rate F _S2 of this embodiment has not reached 0 between times t _{1 and} t ₃ . This, during the time _t 1 ~t _3, means that the second desuperheater 17 continues to adjust the steam temperature _{T 4} to _{T 4} setting.

In the period _{R 4,} after the steam temperature _{T 3} during the period _{R 3} has reached 547 ° C., steam temperature _{T 4} has reached 547 ° C.. As a result, the steam temperature T ₃ is maintained at 547 ° C., and the steam temperature T ₄ is also maintained at 547 ° C. The spray flow rate F _S1 is adjusted to maintain the vapor temperature T ₃ at 547 ° C. Meanwhile, since the steam temperature _{T 3} and the steam temperature _{T 4} is adjusted to both 547 ° C., spray flow _{F S2} is maintained substantially zero. The spray flow rate F _S2 increases from 0 only when the vapor temperature T ₄ becomes higher than 547 ° C.

(3) Modified Example of First Embodiment FIG. 9 is a schematic diagram illustrating a configuration of a power plant according to a modified example of the first embodiment.

  The steam turbine 25 of this modification is configured by a high pressure turbine 25a and a low pressure turbine 25b. The high-pressure turbine 25a is provided downstream of the second temperature reducer 17 with respect to the steam flow. The low pressure turbine 25b is provided downstream of the high pressure turbine 25a with respect to the flow of steam. The high-pressure and low-pressure turbines 25a and 25b are examples of first and second steam turbines, respectively.

  In addition to the components shown in FIG. 1, the power plant according to the present modification includes a third superheater 101, a third temperature reducer 102, a fourth superheater 103, a fourth temperature reducer 104, and a third reducer. A warmer valve 105 and a fourth desuperheater valve 106 are provided. The third temperature reducer 102, the fourth superheater 103, the fourth temperature reducer 104, the third temperature reducer valve 105, and the fourth temperature reducer valve 106 are respectively an upstream temperature reducer, a superheater, and a downstream temperature drop. It is an example of a container, a 1st valve, and a 2nd valve.

  The third and fourth superheaters 101 and 103 are provided in the exhaust heat recovery boiler 5 in the same manner as the first and second superheaters 14 and 16. The third and fourth superheaters 101 and 103 are reheaters that reheat the steam supplied from the high pressure turbine 25a to the low pressure turbine 25b with the heat of the exhaust gas.

This power plant further comprises a steam channel L _A between the high pressure turbine 25a and the third superheater 101, and steam path L _B between the third superheater 101 and the third desuperheater 102, a 3 desuperheater 102 and the steam channel _{L C} between the fourth superheater 103, and steam path _{L D} between the fourth superheater 103 and the fourth desuperheater 104, a fourth desuperheater and a steam flow path _{L E} between 104 and the low pressure turbine 25b.

This power plant further includes a flow meter 111 provided in the steam flow path L _A, a thermometer 112 provided in the steam flow path L _B, a thermometer 113 provided in the steam channel L _C, steam flow a thermometer 114 provided in the road _{L D,} and includes a pressure gauge 115 provided on the steam flow path _{L E,} thermometer 116, and a flow meter 117.

  The power plant further includes a pressure gauge 121, a thermometer 122, a flow meter 123 provided in a water flow path for conveying water to the third temperature reducer 102 via the third temperature reducer valve 105, A pressure gauge 124, a thermometer 125, and a flow meter 126 are provided in a water flow path for transporting water to the fourth temperature reducer 104 via the warmer valve 106.

The steam discharged from the second temperature reducer 17 is sent to the high-pressure turbine 25a through the main steam pipe 21. The high pressure turbine 25a is rotationally driven by the steam, thereby rotating the steam turbine rotor. Further, steam exhausted from the high pressure turbine 25a is fed to the low pressure turbine 25b via a steam pipe _L A ~L _E. The low pressure turbine 25b is rotationally driven by the steam, thereby rotating the steam turbine rotor together with the high pressure turbine 25a. The second generator 26 generates power using the rotation of the steam turbine rotor.

Pass steam pipe 23, upstream of the steam turbine 25 is branched from the main steam pipe 21, and joins the vapor flow path L _A. Therefore, when the main steam valve 22 and the bypass steam valve 24 are open, the low pressure turbine 25b is rotationally driven by the steam that has passed through the high pressure turbine 25a and the steam that has bypassed the high pressure turbine 25a.

Vapor steam channel L _A is fed to the third superheater 101 of the exhaust heat recovery boiler 5, after being superheated in the first superheater 101, the third desuperheater through a steam channel L _B 102 And is cooled by the third temperature reducer 102. The third temperature reducer 102 cools the steam with the water from the third temperature reducer valve 105. Cooling steam in the third desuperheater 102 is sent to the fourth superheater 103 of the exhaust heat recovery boiler 5 through a steam channel L _C, after being superheated again in the fourth superheater 103, the steam is sent to the fourth desuperheater 104 through the flow path L _D, it is again cooled in the fourth desuperheater 104. The fourth temperature reducer 104 cools the steam with the water from the fourth temperature reducer valve 106. Steam cooled in the fourth desuperheater 104 is sent to the low pressure turbine 25b via a steam channel L _E.

State of the steam flowing through the steam channel _L A ~L _E is controlled by the controller 20. For example, the control device 20 adjusts the opening degree of the third desuperheater valve 105 and adjusts the flow rate of the spray water in the third desuperheater 102, thereby adjusting the outlet steam temperature of the fourth superheater 103. Can be controlled to set value. Furthermore, the control device 20 adjusts the opening degree of the fourth desuperheater valve 106 and adjusts the flow rate of the spray water in the fourth desuperheater 104, so that the outlet steam temperature of the fourth desuperheater 104 is adjusted. Can be controlled to a set value. This is the same as the control of the first and second coolers 15 and 17.

  In addition, the 4th superheater 103 of this embodiment is a superheater located in the last stage of the waste heat recovery boiler 5 with respect to the flow of steam. The third temperature reducer 102 is positioned upstream of the fourth superheater 103 with respect to the steam flow, and the fourth temperature reducer 104 is positioned downstream of the fourth superheater 103 with respect to the steam flow. doing.

  The description of FIGS. 2 to 8 is also applicable to the first and second superheaters 14 and 16 and the first and second temperature reducers 15 and 17 of this modification. 2 to 8, the first and second superheaters 14 and 16 and the first and second temperature reducers 15 and 17 are replaced with the third and fourth superheaters 101 and 103 and the third and fourth. By replacing with the temperature reducers 102 and 104, the present invention can also be applied to the third and fourth superheaters 101 and 103 and the third and fourth temperature reducers 102 and 104 of this modification.

In this case, in the description of FIGS. 2 to 8, the flow meters, thermometers, and pressure gauges indicated by reference numerals 42 to 48 are replaced with the flow meters, thermometers, and pressure gauges indicated by reference numerals 111 to 117. Moreover, the flowmeter, thermometer, and pressure gauge indicated by reference numerals 51 to 56 are replaced with the flowmeter, thermometer, and pressure gauge indicated by reference numerals 121 to 126, respectively. Moreover, _{T 4} negative deviation tolerance of Figure 5, _{T 4} set value, the opening degree instruction value _{Z S1} of the first desuperheater valve 18, opening indicated value _{Z S2} of the second desuperheater valve 19, _{T 8} negative deviation tolerance, _{T 8} set value, the opening degree instruction value _{Z S3} of the third desuperheater valve 105 is replaced with the opening command value _{Z S4} of the fourth desuperheater valve 106. In this case, the steam temperature T ₇ and steam temperature T _8, it is possible to appropriately control the same manner as the steam temperature T ₃ and the steam temperature T _4.

As described above, the power generation plant of this embodiment, the upstream and downstream of the second superheater 16 comprises first and second desuperheater 15 and 17, the steam temperature T ₄ These two desuperheater T Control to ₄ set values. Therefore, according to this embodiment, as compared with the case of controlling the steam temperature T ₄ by one desuperheater, and controlling the steam temperature T ₄ with high accuracy, it is possible to start the power plant in a short time It becomes possible.

Further, the power generation plant of this embodiment, as the steam temperature T ₃ is higher adjusted by T ₄ negative deviation tolerance than T ₄ set value, and controls the first desuperheater 15, the steam temperature T ₄ T ₄ as adjusted to the set value, and controls the second desuperheater 17. Therefore, according to this embodiment, it is possible that the steam temperature T ₃ second desuperheater 17 is lower than T ₄ set value to suppress a situation where becomes impossible adjust the steam temperature T _4. Therefore, according to this embodiment, it is possible to stably control the steam temperature T _4.

(Second Embodiment)
FIG. 10 is a schematic diagram illustrating a configuration of a power plant according to the second embodiment.

The power plant shown in FIG. 10 includes bypass flow paths L _{5 to} L ₇ in addition to the components shown in FIG. The steam flow paths L _{1 to} L ₄ convey the steam from the drum 11 via the first and second superheaters 14 and 16 and the first and second temperature reducers 15 and 17, whereas the bypass flow paths L _{5 to} L ₇ convey the steam from the drum 11 by bypassing at least a part of the steam flow paths L _{1 to} L ₄ .

Specifically, the bypass flow path L ₅ is branched from the steam flow path L ₁ at a point upstream of the flow meter 42. The bypass flow paths L ₆ and L ₇ are branched from the bypass flow path L ₅ . The bypass channel L ₆ supplies the steam from the bypass channel L ₅ to the junction C ₁ with the steam channel L ₂ . Bypass passage _{L 7} is steam from the bypass flow passage _{L 5,} and supplies at the junction _{C 2} of the steam flow path _{L 4.}

This power plant further comprises 'and, thermometer 45 provided in the steam flow path L _4' thermometer 43 provided on the steam flow path L ₂ and. Thermometer 43, while located upstream of the junction C _1, thermometer 43 'is located downstream of the junction C _1. Similarly, thermometer 45, while located upstream of the junction C _2, thermometer 45 'is located downstream of the junction C _2.

The power plant further includes a first bypass valve 71 and a first bypass flow meter 73 provided in the bypass flow path L ₆ , and a second bypass valve 72 and a second bypass flow meter 74 provided in the bypass flow path L _7. And.

In the present power plant, steam from the steam flow path L ₂ can be cooled by the first temperature reducer 15, and steam from the steam flow path L ₄ can be cooled by the second temperature reducer 17. Moreover, this power plant, to cool the steam can be cooled by the steam of the steam of the steam flow path L ₂ from the bypass flow passage L _6, the steam of the steam flow path L ₄ from the bypass flow passage L ₇ Can do.

In this case, downstream of the steam temperature of the junction C ₁ can be controlled and upstream of the steam junction C _1, the flow rate ratio of the vapor of the bypass passage L _6. Downstream of the upper limit of the steam temperature of the junction C ₁ becomes an upstream steam temperature of junction C _1, downstream of the lower limit of the steam temperature of the junction C ₁ is a steam temperature of the bypass passage L _6. This is the same even in the confluence C _2.

  FIG. 11 is a graph for explaining the operation of the power plant according to the second embodiment.

The horizontal axis in FIG. 11 indicates the distance between each point on the steam flow path and the drum 11. The vertical axis | shaft of FIG. 11 shows the temperature of the steam which flows through a steam flow path. Symbols T ₁ and T ₁ ′ indicate the temperature of the steam flowing through the steam flow path L ₂ , and are measured by the thermometers 43 and 43 ′. A symbol ΔT ₁ indicates a temperature difference between T ₁ and T ₁ ′ (ΔT ₁ = T ₁ −T ₁ ′). Symbol T ₂ indicates the temperature of the steam flowing through the steam flow path L ₃ , and is measured by the thermometer 44. Symbols T ₃ and T ₃ ′ indicate the temperature of the steam flowing through the steam flow path L ₄ , and are measured by the thermometers 45 and 45 ′. A symbol ΔT ₃ indicates a temperature difference between T ₃ and T ₃ ′ (ΔT ₃ = T ₃ −T ₃ ′). Reference symbol T ₄ indicates the temperature of the steam flowing through the main steam pipe 21 and is measured by the thermometer 47. FIG. 11 shows measured values of the steam temperatures T _{1 to} T ₄ by these thermometers 43, 43 ′, 44, 45, 45 ′, 47.

Hereinafter, how to calculate the steam temperature _T 1 through T _4.

The steam temperature T ₁ ′ at the point between the merging point C ₁ and the first temperature reducer 15 is given by the following equation (12).
T ₁ ′ = (TF _B1 + T ₁ F _T1 ) / (F _B1 + F _T1 ) (12)
However, T is, representative of the temperature of steam flowing through the bypass passage _L 5 ~L _7. Here, T is the saturated steam temperature calculated assuming that the steam pressure (drum pressure) at the point of the pressure gauge 41 is the saturated steam pressure. T ₁ and F _T1 represent the temperature and flow rate of the steam flowing through the point of the thermometer 43. F _T1 is equal to the flow rate F ₁ of the steam flowing through the flow meter 42. T ₁ ′ represents the temperature of the steam flowing through the point of the thermometer 43 ′. F _B1 represents the flow rate of the steam flowing through the point of the first bypass flow meter 73.

Steam temperature _{T 2} is an inlet steam temperature of the outlet steam temperature and the second superheater 16 in the first desuperheater 15, the formula (1) and in the same manner as (2), the following equation (13) to (15) Given in.
T ₂ = HPT (H _T2 , P _T2 ) (13)
H _T2 = {F _S1 × TPH (T _S1 , P _S1 ) + F _T1 ′ × TPH (T ₁ ′, P _T1 ′)}
/ (F _T1 '+ F _S1 ) (14)
F _T1 ′ = F _T1 + F _B1 (15)
However, T ₁ ′, P _T1 ′, and F _T1 ′ represent the temperature, pressure, and flow rate of the steam flowing through the point of the thermometer 43 ′. T _{2, P T2, H} T2 represents the temperature of the steam flowing through the point of the thermometer 44, the pressure, the enthalpy. P _S1 , T _S1 , and F _S1 represent the pressure, temperature, and flow rate of the spray water flowing through the points of the pressure gauge 51, the thermometer 52, and the flow meter 53, respectively.

Steam temperature _{T 3} is the inlet steam temperature of the outlet steam temperature and the second desuperheater 17 of the second superheater 16, similarly to the equation (3) and (4), the following equation (16) and (17) Given in.
T ₃ = Func (T _G , F _G , T ₂ , F _T2 ) (16)
F _T2 = F _T1 '+ F _S1 (17)
However, T ₂ and _{FT 2} represent the temperature and flow rate of the steam flowing through the point of the thermometer 44. T ₃ represents the temperature of the steam flowing through the point of the thermometer 45. T _G and F _G represent the temperature and flow rate of the exhaust gas flowing through the points of the thermometer 31 and the flow meter 32, respectively.

The steam temperature T ₃ ′ at a point between the merging point C ₂ and the second temperature reducer 17 is given by the following equations (18) and (19).
T ₃ '= (TF _{B 2} + T ₃ F _T3 ) / (F _B2 + F _T3 ) (18)
F _T3 = F _T2 (19)
However, T ₃ and F _T3 represent the temperature and flow rate of the steam flowing through the point of the thermometer 45. T ₃ ′ represents the temperature of the steam flowing through the point of the thermometer 45 ′. F _B2 represents the flow rate of the steam flowing through the point of the second bypass flow meter 74.

Steam temperature _{T 4} is an outlet steam temperature of the second desuperheater 17, similarly to Equation (5) to (7), is given by the following equation (20) to (22).
T ₄ = HPT (H _T4 , P _T4 ) (20)
H _T4 = {F _S2 × TPH (T _S2 , P _S2 ) + F _T3 ′ × TPH (T ₃ ′, P _T3 ′)}
/ (F _T3 '+ F _S2 ) (21)
F _T3 ′ = F _T3 + F _B2 (22)
However, T ₃ ′, P _T3 ′, and F _T3 ′ represent the temperature, pressure, and flow rate of the steam flowing through the point of the thermometer 45 ′. T _{4, P T4, H} T4 represents a temperature of the steam flowing through the point of the thermometer 47, the pressure, the enthalpy. P _T4 is equal to the pressure P ₂ of the steam flowing through the point of the pressure gauge 46. P _S2 , T _S2 , and F _S2 represent the pressure, temperature, and flow rate of the spray water flowing through the points of the pressure gauge 54, the thermometer 55, and the flow meter 56, respectively.

In Expressions (12) to (22), it is assumed that the pressure loss in the steam channel and the bypass channel is almost zero. The control device 20 calculates the value of the left side of the equations (12) to (22) by substituting the measured value acquired from the thermometers 43 to 45 ′ into the right side of the equations (12) to (22). Can do. When measurement errors such as the pressure loss and the thermometers 43 to 45 ′ are small, the values of the steam temperatures T ₁ ′ to T ₄ can be accurately calculated from these equations.

(1) Control device 20 of the second embodiment
FIG. 12 is a schematic diagram illustrating a configuration of the control device 20 according to the second embodiment.

  In addition to the components shown in FIG. 5, the control device 20 includes a first bypass setting unit 81, a second bypass setting unit 82, a first bypass control unit 83, a second bypass control unit 84, a subtractor 85, It has. The first and second bypass setting units 81 and 82 are examples of a third setting unit. The first and second bypass control units 83 and 84 are examples of a third control unit.

The first bypass setting unit 81 holds a ΔT ₁ set value as a set value for adjusting the temperature difference ΔT ₁ . The temperature difference [Delta] T ₁ includes a steam temperature _{T 1} of the at the point of the thermometer 43 represents the difference between the 'steam temperature _{T 1} of the at the point' thermometer _{43 (ΔT 1 = T 1 -T} 1 '). The point of the thermometer 43 and the point of the thermometer 43 ′ are examples of the third point and the fourth point upstream of the upstream desuperheater. The steam temperature T ₁ and the steam temperature T ₁ ′ are examples of the third temperature and the fourth temperature. The ΔT ₁ set value of the present embodiment is a constant that does not change with time, and is set to 5 ° C., for example. The ΔT ₁ set value is an example of a third set value.

The first bypass flow rate F _B1 , which is the steam flow rate at the point of the first bypass flow meter 73, is given by the following equation (23) by this temperature difference ΔT ₁ .
F _B1 = ΔT ₁ F _T1 / (T ₁ −ΔT ₁ −T) (23)
Equation (23) is derived by substituting ΔT ₁ into Equation (12). When the ΔT ₁ set value is substituted for ΔT ₁ in Expression (23), the first bypass flow rate F _{B1 at} the equilibrium point is calculated.

The second bypass setting unit 82 holds a ΔT ₃ set value as a set value for adjusting the temperature difference ΔT ₃ . Temperature difference [Delta] T ₃ includes a steam temperature _{T 3} at the point of the thermometer 45 represents the difference between the 'steam temperature _{T 3} at the point of' thermometer _{45 (ΔT 3 = T 3 -T} 3 '). The point of the thermometer 45 and the point of the thermometer 45 ′ are examples of the third point and the fourth point between the superheater and the downstream temperature reducer. The steam temperature T ₃ and the steam temperature T ₃ ′ are examples of the third temperature and the fourth temperature. The ΔT ₃ set value of the present embodiment is a constant that does not change with time, and is set to 20 ° C., for example. The ΔT ₃ set value is an example of a third set value.

The second bypass flow rate F _B2 that is the steam flow rate at the point of the second bypass flow meter 74 is given by the following equation (24) by this temperature difference ΔT ₂ .
F _B2 = ΔT ₃ F _T3 / (T ₃ −ΔT ₃ −T) (24)
Equation (24) is derived by substituting ΔT ₃ into Equation (18). When the ΔT ₃ set value is substituted for ΔT ₃ in the equation (24), the second bypass flow rate F _{B2 at} the equilibrium point is calculated.

The first bypass control unit 83 controls the first bypass valve 71 so that the temperature difference ΔT ₁ is adjusted to the ΔT ₁ set value. Specifically, the first bypass control unit 83 calculates the first bypass flow rate F _B1 by substituting the ΔT ₁ set value into the equation (23), and calculates the first bypass flow rate F _B1 from the first bypass flow rate F _B1 . The opening instruction value Z _B1 is calculated and output. As a result, the opening degree of the first bypass valve 71 is adjusted to the opening degree instruction value Z _B1 , the first bypass flow rate F _B1 reaches the equilibrium point, and the temperature difference ΔT ₁ approaches the ΔT ₁ set value.

However, since the first bypass flow rate F _B1 does not always reach the equilibrium point, and there is a measurement error in the thermometers 43, 43 ′, etc., the temperature difference ΔT ₁ does not become the ΔT ₁ set value by the above control. There is a case. Therefore, the first bypass control unit 83 performs PID control using a deviation between the measured value of the steam temperature T ₁ ′ and the set value, and performs the PID control on the first bypass flow rate F _B1 calculated from the ΔT ₁ set value. The first bypass flow rate F _B1 is corrected by adding the operation amount. As a result, the temperature difference ΔT ₁ can be accurately adjusted to the ΔT ₁ set value.

The second bypass control unit 84 controls the second bypass valve 72 so that the temperature difference ΔT ₃ is adjusted to the ΔT ₃ set value. Specifically, the second bypass control unit 84 calculates the second bypass flow rate F _B2 by substituting the ΔT ₃ set value into the equation (24), and calculates the second bypass flow rate F _B2 from the second bypass flow rate F _B2 . The opening instruction value Z _B2 is calculated and output. Thereby, the opening degree of the second bypass valve 72 is adjusted to the opening degree instruction value Z _B2 , the second bypass flow rate F _B2 reaches the equilibrium point, and the temperature difference ΔT ₃ approaches the ΔT ₃ set value.

However, since the second bypass flow rate F _B2 does not always reach the equilibrium point and there is a measurement error in the thermometers 45, 45 ′, etc., the temperature difference ΔT ₃ does not become the ΔT ₃ set value by the above control. There is a case. Therefore, the second bypass control unit 84 performs PID control using a deviation between the measured value of the steam temperature T ₃ ′ and the set value, and performs the PID control on the second bypass flow rate F _B2 calculated from the ΔT ₃ set value. The second bypass flow rate F _B2 is corrected by adding the operation amount. As a result, the temperature difference ΔT ₃ can be accurately adjusted to the ΔT ₃ set value.

  The first setting unit 61, the second setting unit 62, the adder 63, the upper limit value setting unit 64, the margin value setting unit 65, the subtractor 66, the selection unit 67, the first temperature reducer control unit 68, the second in FIG. 12. The operation of the temperature reducer control unit 69 is the same as in FIG.

However, the T ₄ negative deviation allowable value of the present embodiment is the difference between the T ₃ set value and the T ₄ set value as in the first embodiment (T ₄ negative deviation allowable value = T ₃ set value). -T ₄ set value), the inlet steam temperature of the second desuperheater 17 in the present embodiment is a steam rather than steam temperature T ₃ temperature T _{3 '.}

Therefore, the control device 20 of the present embodiment, the adder 63, after outputting the T ₃ set value by adding of T ₄ negative deviation tolerance to T ₄ setting value, the subtracter 85, from the T ₃ set value by subtracting the [Delta] T ₃ set value 'outputs a preset value _{(T 3' T 3} set value = _{T 3} set value -.DELTA.T ₃ set value). The selection unit 67 outputs the lower value of the T ₃ ′ set value and the correction upper limit value. Further, the first temperature reducer control unit 68 controls the first temperature reducer 15 so that the steam temperature T ₃ ′ is adjusted to the lower of the T ₃ ′ set value and the corrected upper limit value. As a result, the steam temperature T ₃ ′ approaches the lower value of the T ₃ ′ set value and the corrected upper limit value, and further, the steam temperature T ₃ is lower than the T ₃ set value and “corrected upper limit value + ΔT ₃ set value”. I ’m getting closer.

As described above, the T ₃ set value is given by “T ₄ negative deviation allowable value + T ₄ set value”, and T ₃ ′ set value is “T ₄ negative deviation allowable value + T ₄ set value−ΔT ₃ set value”. Given. The T ₄ negative deviation allowable value, the T ₄ set value, and the ΔT ₃ set value are examples of the first, second, and third set values, respectively. In the present embodiment, the steam temperature T ₃ is adjusted to be higher than the second set value by the first set value, and the steam temperature T ₃ ′ is set between the first set value and the third set value than the second set value. The difference value is adjusted higher. The steam temperature T ₃ is an example of the first and third temperatures, the steam temperature T ₃ ′ is an example of the fourth temperature, and the steam temperature T ₄ is an example of the second temperature.

  FIG. 13 is a schematic diagram illustrating a configuration of the first bypass control unit 83 of the second embodiment.

  The first bypass control unit 83 includes a bypass steam temperature calculation unit (hereinafter referred to as “temperature calculation unit”) 91, a bypass steam flow rate calculation unit (hereinafter referred to as “flow rate calculation unit”) 92, a subtractor 93, and a PID. A control unit 94, an adder 95, and a valve opening calculation unit (hereinafter referred to as “opening calculation unit”) 96 are provided.

Temperature calculation section 91 calculates the saturated steam temperature as a drum pressure P _D of the pressure gauge 41 is a saturated vapor pressure, and outputs the saturated steam temperature as the steam temperature T of the bypass flow passage L ₅ ~L _7.

The flow rate calculation unit 92 includes a steam temperature T from the temperature calculation unit 91, a ΔT ₁ set value from the first bypass setting unit 81, a steam temperature T ₁ from the thermometer 43, and a steam flow rate F from the flow meter 42. ₁ (= F _T1 ) is substituted into equation (23) to calculate the first bypass flow rate F _B1 .

The subtractor 93 subtracts the ΔT ₁ set value from the steam temperature T ₁ measured by the thermometer 43 and outputs a set value of the steam temperature T ₁ ′ for PID control.

PID control unit 94, the steam temperature T _{1 'measured} values obtained from the thermometer 43, the steam temperature T _1' acquires the setting value from the subtractor 93, using a difference between these measured values with the set value PID control is performed. Specifically, PID control unit 94 sets the correction amount of the first bypass flow F _B1 to approach the deviation to zero.

The adder 95 adds the correction amount to the first bypass flow rate F _B1 calculated by the flow rate calculation unit 92, and outputs the corrected first bypass flow rate F _B1 .

The opening calculation unit 96 calculates and outputs an opening instruction value Z _B1 of the first bypass valve 71 based on the corrected first bypass flow rate F _B1 . For example, the opening degree calculation unit 96 converts the corrected first bypass flow rate F _B1 into the opening degree instruction value Z _B1 using the CV characteristic of the first bypass valve 71.

The configuration of the second bypass control unit 84 is the same as the configuration of the first bypass control unit 83. In this case, the equation (23) is replaced with the equation (24), and the steam flow rate F ₁ (= F _T1 ), the steam temperatures T ₁ and T ₁ ′, and ΔT ₁ set values are the steam flow rate F _T3 and the steam temperature T, respectively. ₃ and T ₃ ′, ΔT ₃ set value is replaced. As shown in the equations (15), (17), and (19), the steam flow rate F _T3 includes the steam flow rate F ₁ from the flow meter 42, the steam flow rate F _B1 from the first bypass flow meter 73, and the flow meter. 53 and the vapor flow rate F _S1 from 53 (F _T3 = F ₁ + F _B1 + F _S1 ).

(2) Operation of Power Plant of Second Embodiment FIG. 14 is a graph showing an operation example of the power plant of the second embodiment. In the present embodiment, the T ₄ negative deviation allowable value, ΔT ₁ set value, and ΔT ₃ set value are set to 30 ° C., 5 ° C., and 20 ° C., respectively.

In the period R ₁ , the spray flow rates F _S1 and F _S2 are set to 0, and the bypass flow rates F _B1 and F _B2 are also set to 0. Therefore, the steam temperature T ₂ becomes the same value as the steam temperatures T ₁ and T ₁ ′, and increases with time. Similarly, the steam temperature T ₄ becomes the same value as the steam temperatures T ₃ and T ₃ ′, and increases with time.

In the period R ₂ , the spray flow rate F _S1 is initially set to a constant value (arrow B ₁ ). Further, in the period R ₂ and the subsequent period, the bypass flow rates F _B1 and F _B2 are set so as to adjust the temperature differences ΔT ₁ and ΔT ₃ to the set values ΔT ₁ and ΔT ₃ , respectively. As a result, the steam temperature T ₂ is slowly decrease or increase. On the other hand, the steam temperature T ₃ ′ increases with time because the steam temperature rising speed at the second superheater 16 is faster than the steam temperature decreasing speed at the first decelerator 15 and the junction C _2. To go. Further, since the T ₄ set value is maintained at a constant value (400 ° C.) in the first half of the period R ₂ (see FIG. 6), the spray flow rate F _S2 is set so that the steam temperature T ₄ is maintained at 400 ° C. Adjusted. Thereafter, the T ₄ set value gradually increases from 400 ° C. in the latter half of the period R ₂ (see FIG. 6), so the steam temperature T ₄ increases with time.

However, the T ₄ negative deviation allowable value and ΔT ₃ set value of this embodiment are set to 30 ° C. and 20 ° C., respectively, and the T ₃ ′ set value is higher by 10 ° C. than the T ₄ set value. As a result, even if increased steam temperature _{T 4} in the second half of the period _{R 2,} steam temperature _{T 4} in the period _{R 3} does not reach the steam temperature _{T 3} '(arrow _A 3). Thus, the second desuperheater 17 in the present embodiment, it is possible to adjust the steam temperature T ₄ in the period R ₃ to T ₄ setting value, is divergence between the steam temperature T ₄ and T ₄ set value Generation | occurrence | production can be suppressed. In the periods R ₂ and R ₃ , the spray flow rate F _S1 is adjusted so that the steam temperature T ₃ ′ approaches the T ₃ ′ set value (= T ₄ set value + T ₄ negative deviation allowable value−ΔT ₃ set value). (Arrows B ₂ and B ₃ ). Similarly, the spray flow rate F _S2 is adjusted so that the steam temperature T ₄ approaches the T ₄ set value.

In the period R ₄ , the steam temperature T ₄ has reached 547 ° C. after the steam temperature T ₃ ′ has reached 547 ° C. in the period R ₃ . As a result, the steam temperature T ₃ ′ is maintained at 547 ° C., and the steam temperature T ₄ is also maintained at 547 ° C. The spray flow rate F _S1 is adjusted to maintain the vapor temperature T ₃ ′ at 547 ° C. On the other hand, since both the steam temperature T ₃ ′ and the steam temperature T ₄ are adjusted to 547 ° C., the spray flow rate F _S2 is maintained at approximately 0. The spray flow rate F _S2 increases from 0 only when the vapor temperature T ₄ becomes higher than 547 ° C.

(3) Modified Example of Second Embodiment FIG. 15 is a schematic diagram illustrating a configuration of a power plant according to a modified example of the second embodiment.

  The steam turbine 25 of this modification is comprised by the high pressure turbine 25a and the low pressure turbine 25b similarly to the steam turbine 25 (FIG. 9) of the modification of 1st Embodiment.

The power plant of this modification is provided with bypass flow paths L _{F to} L _H in addition to the components shown in FIGS. 9 and 10. Steam channel _L A ~L _E is the steam from the high pressure turbine 25a third, fourth superheater 101, 103, and the third, while conveying through a fourth desuperheater 102, a bypass flow road _L F ~L _H is the steam from the high pressure turbine 25b conveys bypassing at least a portion of the steam channel _L a ~L _E.

Specifically, the bypass flow passage L _F is at a point upstream of the flow meter 111 is branched from the steam passage L _A. The bypass channels L _G and L _H branch from the bypass channel L _F. Bypass passage _{L G} is, steam from the bypass passage _{L F,} and supplies the confluence _{C A} between the steam path _{L B.} Bypass passage _{L H} is the steam from the bypass passage _{L F,} and supplies the confluence _{C B} of the steam flow path _{L D.}

This power plant further comprises 'and, thermometer 114 provided in the steam flow path L _D' thermometer 112 provided in the steam flow path L _B and. Thermometer 112, while located upstream of the junction C _A, thermometer 112 'is located downstream of the merging point C _A. Similarly, thermometer 114, while located upstream of the junction C _B, thermometer 114 'is located downstream of the junction C _B.

This power plant further bypass channel L and the third bypass valve 131 and the third bypass flowmeter 133 provided in _G, the bypass flow passage L 4 bypass valve provided in _H 132 and the fourth bypass flowmeter 134 And.

In the present power plant, the steam from the steam channel L _B can be cooled by the third temperature reducer 102, and the steam from the steam channel L _D can be cooled by the fourth temperature reducer 104. Moreover, this power plant, it is possible to cool the steam of the steam flow path L _B by the steam from the bypass passage L _G, be cooled by steam steam steam path L _D from the bypass flow passage L _H Can do.

The description of FIGS. 11 to 14 is also applicable to the first and second superheaters 14 and 16, the first and second temperature reducers 15 and 17, and the bypass flow paths L _{5 to} L ₇ of this modification. is there. Moreover, the description of FIGS. 11-14 replaces these with the third and fourth superheaters 101 and 103, the third and fourth desuperheaters 102 and 104, and the bypass flow paths L _{F to} L _G. The present invention can also be applied to the third and fourth superheaters 101 and 103, the third and fourth temperature reducers 102 and 104, and the bypass flow paths L _{F to} L _G of this modification.

In this case, in the description of FIGS. 11 to 14, in addition to the replacement in the modification of the first embodiment, the valves and flow meters denoted by reference numerals 71 to 74 are replaced with the valves and flow meters denoted by reference numerals 131 to 134. It is done. In addition, T ₄ negative deviation allowable value, T ₄ set value, ΔT ₁ set value, ΔT ₃ set value, opening instruction values Z _S1 , Z _S2 , Z _B1 , Z _B2 in FIG. 12 are T ₈ negative deviation allowable values. , _{T 8} set value, [Delta] T ₅ set value, [Delta] T ₇ set value, the opening degree instruction value _{Z S3,} Z _S4, is replaced by Z _{B3, Z B4.} In this case, the steam temperatures T ₇ , T ₇ ′, and T ₈ can be appropriately controlled in the same manner as the steam temperatures T ₃ , T ₃ ′, and T ₄ .

As described above, the power generation plant of this embodiment, the upstream and downstream of the second superheater 16 comprises first and second desuperheater 15 and 17, the steam temperature T ₄ These two desuperheater T Control to ₄ set values. Therefore, according to this embodiment, as compared with the case of controlling the steam temperature T ₄ by one desuperheater, and controlling the steam temperature T ₄ with high accuracy, it is possible to start the power plant in a short time It becomes possible.

In the power plant of this embodiment, the steam temperature T ₄ is controlled to the T ₄ set value by the first and second temperature reducers 15 and 17 and the first and second bypass valves 71 and 72. Therefore, according to this embodiment, as compared with the case of controlling the steam temperature T ₄ at only these desuperheater, it is possible to realize a short activation than control of high accuracy.

Further, the power generation plant of this embodiment, as the steam temperature T ₃ is higher adjusted by T ₄ negative deviation tolerance than T ₄ set value, and controls the first desuperheater 15, the steam temperature T ₄ T ₄ as adjusted to the set value, and controls the second desuperheater 17. Further, the power plant of the present embodiment controls the first bypass valve 71 so that the steam temperature T ₃ ′ is adjusted to be higher by “T ₄ negative deviation allowable value−ΔT ₃ set value” than the T ₄ set value. To do. Therefore, according to the present embodiment, it is possible to suppress a situation in which the steam temperature T ₃ ′ becomes lower than the T ₄ set value and the second temperature reducer 17 becomes unable to adjust the steam temperature T ₄ . Therefore, according to this embodiment, it is possible to stably control the steam temperature T _4.

  Although several embodiments have been described above, these embodiments are presented as examples only and are not intended to limit the scope of the invention. The novel apparatus, methods, and plants described herein can be implemented in a variety of other forms. In addition, various omissions, substitutions, and changes can be made to the apparatus, method, and plant configuration described in the present specification without departing from the spirit of the invention. The appended claims and their equivalents are intended to include such forms and modifications as fall within the scope and spirit of the invention.

1: gas turbine, 2: compressor, 3: first generator,
4: exhaust gas piping, 5: exhaust heat recovery boiler,
11: drum, 12: downcomer, 13: evaporator,
14: 1st superheater, 15: 1st desuperheater, 16: 2nd superheater, 17: 2nd desuperheater,
18: 1st temperature reducer valve, 19: 2nd temperature reducer valve, 20: Control apparatus,
21: Main steam piping, 22: Main steam valve,
23: Bypass steam piping, 24: Bypass steam valve, 25: Steam turbine,
25a: high-pressure turbine, 25b: low-pressure turbine, 26: second generator,
31: Thermometer, 32: Flow meter,
41: Pressure gauge, 42: Flow meter, 43, 43 ': Thermometer, 44: Thermometer,
45, 45 ': Thermometer, 46: Pressure gauge, 47: Thermometer, 48: Flow meter,
51: Pressure gauge, 52: Thermometer, 53: Flow meter,
54: Pressure gauge, 55: Thermometer, 56: Flow meter,
57: Rotational speed measuring instrument, 58: Electrical output measuring instrument,
61: first setting unit, 62: second setting unit, 63: adder,
64: upper limit value setting unit, 65: margin value setting unit, 66: subtractor,
67: Selection unit, 68: First temperature reducer control unit, 69: Second temperature reducer control unit,
71: 1st bypass valve, 72: 2nd bypass valve,
73: 1st bypass flow meter, 74: 2nd bypass flow meter,
81: 1st bypass setting part, 82: 2nd bypass setting part,
83: 1st bypass control part, 84: 2nd bypass control part, 85: Subtractor,
91: bypass steam temperature calculation unit, 92: bypass steam flow rate calculation unit,
93: Subtractor, 94: PID control unit, 95: Adder, 96: Valve opening calculation unit,
101: third superheater, 102: third desuperheater,
103: 4th superheater, 104: 4th desuperheater,
105: 3rd temperature reducer valve, 106: 4th temperature reducer valve,
111: flow meter, 112, 112 ′: thermometer, 113: thermometer,
114, 114 ′: thermometer, 115: pressure gauge, 116: thermometer, 117: flow meter,
121: Pressure gauge, 122: Thermometer, 123: Flow meter,
124: Pressure gauge, 125: Thermometer, 126: Flow meter,
131: Third bypass valve, 132: Fourth bypass valve,
133: Third bypass flow meter, 134: Fourth bypass flow meter

Claims (11)

An upstream desuperheater that cools the steam;
A superheater that superheats the steam from the upstream desuperheater;
A downstream desuperheater that cools the steam from the superheater;
A plant control device for controlling a power plant comprising:
A first setting unit that outputs a first set value for adjusting a first temperature that is a temperature of the steam at a first point between the superheater and the downstream desuperheater;
A second setting unit that outputs a second set value for adjusting a second temperature that is the temperature of the steam at a second point downstream of the downstream desuperheater;
A first control unit that controls the upstream desuperheater so that the first temperature is adjusted to be higher by the first set value than the second set value;
A second control unit that controls the downstream temperature reducer so that the second temperature is adjusted to the second set value;
A plant control apparatus comprising: The first control unit outputs an opening instruction value of a first valve that supplies water to the upstream desuperheater,
The second control unit outputs an opening instruction value of a second valve that supplies water to the downstream temperature reducer,
The plant control apparatus according to claim 1.   The plant control device according to claim 1, wherein the second setting unit outputs the second setting value that changes according to time.   The first control unit is configured to adjust the first temperature to a lower value of a sum of the first set value and the second set value and a limit value of the steam temperature. The plant control apparatus of any one of Claim 1 to 3 which controls an upstream desuperheater. The power plant is
A steam flow path for conveying the steam via the upstream desuperheater, the superheater, and the downstream desuperheater;
A bypass passage for bypassing at least a part of the steam passage to convey the steam and supplying the steam to a junction with the steam passage;
A bypass valve provided in the bypass channel;
The plant control device according to any one of claims 1 to 4, further comprising: The temperature difference between the third temperature, which is the temperature of the steam at the third point upstream from the junction, and the fourth temperature, which is the temperature of the steam at the fourth point downstream from the junction, is adjusted. A third setting unit for outputting a third setting value for
A third control unit for controlling the bypass valve such that the temperature difference is adjusted to the third set value;
The plant control apparatus according to claim 5, further comprising:   The plant control device according to claim 6, wherein the junction point, the third point, and the fourth point are located upstream of the upstream desuperheater.   The plant control apparatus according to claim 6, wherein the junction point, the third point, and the fourth point are located between the superheater and the downstream desuperheater. The third point and the third temperature are the first point and the first temperature, respectively.
The first control unit adjusts the third temperature to be higher than the second set value by the first set value, and the fourth temperature is higher than the second set value. Controlling the upstream desuperheater so as to be adjusted higher by a difference value from the third set value;
The plant control apparatus according to claim 8.   The first control unit reduces the upstream temperature so that the fourth temperature is adjusted to a lower value of a sum of the second set value and the difference value and a limit value of the steam temperature. The plant control apparatus of Claim 9 which controls a warmer. The power plant further includes a first steam turbine and a second steam turbine provided downstream of the first steam turbine,
The upstream desuperheater, the superheater, and the downstream desuperheater are:
Provided in a first steam flow path upstream of the first steam turbine and supplying the steam from the downstream desuperheater to the first steam turbine, or
Provided in a second steam flow path between the first steam turbine and the second steam turbine to supply the steam from the downstream desuperheater to the second steam turbine;
The plant control apparatus of any one of Claim 1 to 10.

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