TW201920830A - Plant control apparatus plant control method and power generation plant - Google Patents

Abstract

The present invention relates to a plant control apparatus capable of executing heat soak, a plant control method, and a power generation plant. According to one embodiment of the present invention, a plant control apparatus controls the power generation plant comprising: a combustor combusting fuel with oxygen introduced from an inlet guide blade to generate gas; a gas turbine operated by the gas provided from the combustor; an exhaust heat collection boiler using heat of exhaust gas outputted from the gas turbine to generate steam; and a steam turbine operated by the steam provided from the exhaust heat collection boiler. The plant control apparatus controls the opening degree of the inlet guide blade before starting the steam turbine, controls the opening degree of the inlet guide blade by a second opening degree greater than a first opening degree after starting the steam turbine, and decreases the opening degree of the inlet guide blade from the second opening degree to the opening degree equal to or greater than the first opening degree during a predetermined period to maintain an output value of the steam turbine at a predetermined value.

Description

Factory control unit, factory control method, and power plant

Embodiments of the present invention relate to a plant control device, a plant control method, and a power plant.

Generally, a recirculating power plant (C/C power plant) includes a gas turbine, a waste heat recovery boiler, and a steam turbine, and uses the energy generated by combustion of the fuel to generate thermal power. Specifically, the gas turbine is driven by a gas supplied from a burner that burns fuel. The waste heat recovery boiler generates steam using the heat of the exhaust gas discharged from the gas turbine. The steam turbine is driven by steam supplied from the waste heat recovery boiler. Such a technique is disclosed in Japanese Laid-Open Patent Publication No. 62-153505 (hereinafter referred to as Patent Document 1). In addition, as for the non-patent literature in Japan, the "Fireplace Association Lecture "Measurement and Control" Heisei 21 revised edition" issued by the Society for Firepower Atomic Power Generation Technology Association, Chapter III, 1.3.3, page 74 (hereinafter referred to as non- Patent Document 1).

[Problems to be solved by the invention]

The conventional C/C power plant uses a small-capacity gas turbine, so the steam turbine combined with it is also small in capacity, and the thermal stress generated by the steam turbine does not become a big problem.

However, in recent gas turbines used in recent C/C power plants, the temperature and capacity of the turbine inlet temperature (combustion temperature) have become remarkable. Therefore, the steam turbine combined therewith also has a large capacity, and the thermal stress generated by the steam turbine at the time of starting becomes a big problem. Therefore, before the output of the steam turbine is raised to the rated value, it is necessary to slowly increase the steam temperature of the steam turbine to alleviate the heat soaking of the thermal stress. At this time, in the same manner as in the case of performing soaking in the steam power plant, it is expected to introduce a uniform heat treatment in consideration of the limitations or characteristics of the C/C power plant.

An object of an embodiment of the present invention is to provide a plant control device, a plant control method, and a power plant that are suitable for performing soaking treatment on a power plant including a gas turbine and a steam turbine. [Means to solve the problem]

According to one embodiment, a plant control device controls a power plant having a burner that simultaneously combusts oxygen and fuel introduced by the inlet guide vanes to generate gas; the gas turbine is provided by the burner from the burner The gas is driven; the waste heat recovery boiler generates steam using heat from the exhaust gas of the gas turbine; and the steam turbine is driven by the steam from the waste heat recovery boiler. The apparatus includes: a first output control unit that controls an output value of the gas turbine; and a second output control unit that controls an output value of the steam turbine and sets an output value of the steam turbine within a predetermined period of time Keep at the specified value. Further, the apparatus further includes an opening degree control unit that controls an opening degree of the inlet guide vane before starting the steam turbine to a first opening degree, and controls an opening degree of the inlet guide vane after the steam turbine is started. a second opening degree larger than the first opening degree, wherein the opening degree of the inlet guide vane is lowered from the second opening degree to the first opening degree or lower than the first opening degree in the predetermined period And a third opening degree smaller than the second opening degree described above.

Embodiments of the present invention will now be described with reference to the drawings. The same or similar components are denoted by the same reference numerals in FIGS. 1 to 7, and the repeated description is omitted.

(First Comparative Example) FIG. 3 is a schematic view showing a configuration of a power plant 1 of a first comparative example. The power plant 1 of the comparative example includes a plant control device 2 that controls the power plant 1. The power plant 1 of this comparative example is a one-axis direct connection type C/C power plant.

The power plant 1 includes a fuel regulating valve 11, a burner 12, a compressor 13, a gas turbine 14, a rotating shaft 15, a generator 16, a servo valve 17, a compressed air temperature sensor 18, an output sensor 19, and a waste heat recovery boiler. 21. Steam drum 22, superheater 23, steam turbine 31, condenser 32, addition and subtraction valve 33, bypass regulating valve 34, metal temperature sensor 35, and main steam temperature sensor 36. Further, the compressor 13 includes an inlet 13a and a plurality of inlet guide vanes (IGV: Inlet Guide Vane) 13b, and the gas turbine 14 includes a plurality of exhaust gas temperature sensors 14a.

On the other hand, the plant control device 2 includes a function generator 41, a setter 42, an adder 43, an upper limiter 44, a lower limit limiter 45, a switch 51, an average value calculator 52, a subtractor 53, and a PID (Proportional- Integral-Derivative controller 54, lower limit limiter 55, setter 61, subtractor 62, comparator 63, mismatch chart calculation unit 64, notgate 65, and gate 66. These blocks function as an opening degree control unit that controls the opening degree of the IGV 13b by controlling the operation of the servo valve 17.

The plant control device 2 further includes a GT (gas turbine) output control unit 56 that controls the output of the gas turbine 14 by controlling the operation of the fuel regulator valve 11, and an operation of controlling the addition and subtraction valve 33 (or the operation of the bypass regulator valve 34). The ST (steam turbine) output control unit 57 that controls the output of the steam turbine 31. The GT output control unit 56 is an example of a first output control unit. The ST output control unit 57 is an example of a second output control unit.

The fuel regulating valve 11 is provided in a fuel pipe. When the fuel regulating valve 11 is opened, the fuel A1 is supplied to the combustor 12 by the fuel pipe. On the other hand, the compressor 13 includes an IGV 13b provided at the inlet 13a. The compressor 13 introduces the air A2 from the inlet 13a via the IGV 13b, and supplies the compressed air A3 to the burner 12. The burner 12 co-combuses the oxygen in the fuel A1 and the compressed air A3 to generate the high-temperature and high-pressure combustion gas A4.

The gas turbine 14 is rotationally driven by the combustion gas A4 to rotate the rotary shaft 15. The generator 16 is connected to the rotating shaft 15 and generates electric power by the rotation of the rotating shaft 15. The exhaust gas A5 discharged from the gas turbine 14 is sent to the waste heat recovery boiler 21. Each of the exhaust gas temperature sensors 14a detects the temperature of the exhaust gas A5 near the outlet of the gas turbine 14, and outputs the temperature detection result to the plant control device 2. As will be described later, the waste heat recovery boiler 21 generates steam using the heat of the exhaust gas A5.

The servo valve 17 is used to adjust the opening degree of the IGV 13b. The compressed air temperature sensor 18 detects the temperature of the compressed air A3 near the outlet of the compressor 13, and outputs the detected result of the temperature to the plant control device 2. The output sensor 19 is provided to the generator 16, detects the electrical output of the generator 16, and outputs the output detection result to the plant control device 2. The electric output of the generator 16 corresponds to the sum of the output of the gas turbine 14 (the work given to the outside by the gas turbine 14) and the output of the steam turbine 31 (the work performed by the steam turbine 31 to the outside).

The drum 22 and the superheater 23 are disposed in the waste heat recovery boiler 21 to constitute a part of the waste heat recovery boiler 21. The water in the drum 22 is sent to an evaporator (not shown), and is heated in the evaporator by the exhaust gas A5 to become saturated steam. The saturated steam is sent to the superheater 23, and is superheated in the superheater 23 by the exhaust gas A5 to become the superheated steam A6. The superheated steam A6 generated by the waste heat recovery boiler 21 is discharged to the steam piping. Hereinafter, this superheated steam A6 is referred to as main steam.

The steam piping is divided into a main pipe and a bypass pipe. The main pipe is connected to the steam turbine 31, and the bypass pipe is connected to the condenser 32. The addition and subtraction valve 33 is provided in the main pipe. The bypass regulating valve 34 is provided in the bypass pipe.

When the addition and subtraction valve 33 is opened, the main steam A6 from the main pipe is supplied to the steam turbine 31. The steam turbine 31 is rotationally driven by the main steam A6, whereby the rotary shaft 15 is rotated simultaneously with the gas turbine 14. The main steam A7 discharged from the steam turbine 31 is sent to the condenser 32.

On the other hand, when the bypass regulator valve 34 is opened, the main steam A6 from the bypass pipe bypasses the steam turbine 31 and is sent to the condenser 32. The condenser 32 cools the main steams A6, A7 by circulating water A8 to return the main steams A6, A7 to water. When the circulating water A8 is seawater, the circulating water A8 discharged from the condenser 32 is returned to the sea.

The metal temperature sensor 35 detects the metal temperature of the inner surface of the first stage of the steam turbine 31, and outputs the temperature detection result to the plant control device 2. The main steam temperature sensor 36 detects the temperature of the main steam A6 near the main steam outlet of the waste heat recovery boiler 21, and outputs the temperature detection result to the plant control device 2.

The temperature of the exhaust gas A5 can be controlled by adjusting the supply amount of the fuel A1 or the flow rate of the air A2. Hereinafter, the supply amount of the fuel A1 or the flow rate of the air A2 will be described in detail.

The supply amount of the fuel A1 is adjusted by controlling the opening degree of the fuel regulating valve 11. The GT output control unit 56 of the plant control device 2 outputs a valve control command signal for controlling the opening degree of the fuel regulating valve 11, and accordingly, the supply amount of the fuel A1 is adjusted. For example, when the supply amount of the fuel A1 is increased, the temperature of the combustion gas A4 is lowered, the output value of the gas turbine 14 is lowered, and the temperature of the exhaust gas A5 is lowered. On the other hand, when the supply amount of the fuel A1 decreases, the temperature of the combustion gas A4 rises, the output value of the gas turbine 14 rises, and the temperature of the exhaust gas A5 rises. In this manner, the GT output control unit 56 can control the output value of the gas turbine 14 by controlling the opening degree of the fuel regulating valve 11, whereby the temperature of the exhaust gas A5 can be controlled for control.

The flow rate of the air A2 is adjusted by controlling the opening degree of the IGV 13b. The opening degree of the IGV 13b is controlled by the plant control device 2 in the same manner as the opening degree of the fuel regulating valve 11. The compressor 13 draws in air A2 via the IGV 13b, and compresses the air A2 to generate compressed air A3. For example, when the opening degree of the IGV 13b is increased, the flow rate of the air A2 is increased, and the flow rate of the compressed air A3 is increased. At this time, the temperature of the compressed air A3 is higher than the temperature of the original air A2 (substantially atmospheric temperature) by the compression process, but is extremely low compared with the temperature of the combustion gas A4. As a result, when the opening degree of the IGV 13b is increased, the influence of the compressed air A3 increases the temperature of the combustion gas A4, and the temperature of the exhaust gas A5 decreases. On the other hand, when the opening degree of the IGV 13b is decreased, the influence of the compressed air A3 decreases the temperature rise of the combustion gas A4, and the temperature of the exhaust gas A5 rises. In this manner, the plant control device 2 controls the temperature of the exhaust gas A5 by controlling the opening degree of the IGV 13b. Further, when the supply amount of the fuel A1 is kept constant and the opening degree of the IGV 13b is changed, the output value of the gas turbine 14 is hardly changed.

Fig. 4 is a cross-sectional view showing the structure of a steam turbine 31 of a first comparative example.

The steam turbine 31 includes a rotor 31a having a plurality of moving blades, a stator 31b having a plurality of stationary blades, a steam inflow port 31c, and a steam outflow port 31d. The main steam A6 is introduced from the steam inflow port 31c, and is discharged from the steam outflow port 31d as the main steam A7 in the steam turbine 31.

FIG. 4 shows the installation position of the metal temperature sensor 35. The metal temperature sensor 35 is disposed near the inner surface of the first stage stationary blade of the steam turbine 31. Therefore, the metal temperature sensor 35 can detect the metal temperature of the inner surface of the first stage stationary blade.

Hereinafter, the plant control device 2 will be described in detail with reference to Fig. 3 again.

The function generator 41 generates a function for indicating the correspondence relationship between the output value of the gas turbine 14 (hereinafter referred to as "GT output value") and the temperature of the exhaust gas A5 (hereinafter referred to as "exhaust gas temperature"). The function generator 41 obtains the measured value B1 of the GT output value from the output sensor 19, and outputs a set value B2 of the exhaust gas temperature corresponding to the measured value B1 in accordance with a function curve set in the function generator 41.

Further, the function generator 41 may generate a function indicating the relationship between the pressure of the compressed air A3 (hereinafter referred to as "compressed air pressure") and the normal exhaust temperature. In this case, the function generator 41 acquires the measured value of the compressed air pressure, and outputs the set value B2 of the exhaust gas temperature corresponding to the measured value.

The setter 42 holds the set value ΔT of the temperature difference between the exhaust gas temperature at the time of starting and the metal temperature of the inner surface of the first stage of the steam turbine 31 (hereinafter referred to as "metal temperature"). The adder 43 obtains the measured value B3 of the metal temperature from the metal temperature sensor 35, and acquires the set value ΔT from the setter 42. The adder 43 adds the set value ΔT to the measured value B3 of the metal temperature, and outputs the set value "B3 + ΔT" of the exhaust gas temperature.

The upper limit limiter 44 holds the upper limit UL of the exhaust gas temperature and outputs the smaller of the set value B3 + ΔT and the upper limit UL. The lower limit limiter 45 holds the lower limit value LL of the exhaust gas temperature, and outputs the larger of the output of the upper limit limiter 44 and the lower limit value LL. Therefore, the lower limit limiter 45 outputs the intermediate value among the set value B3 + ΔT, the upper limit UL, and the lower limit LL as the set value B4 of the exhaust temperature. This means that the set value "B3 + ΔT" of the exhaust gas temperature is limited to a value between the upper limit UL and the lower limit LL.

Further, since the power plant 1 of the comparative example was started by the cold start, the measured value B3 of the metal temperature was low. Therefore, B3+ΔT is also a low temperature, and the set value B4 is often a lower limit LL. In this case, since the steam turbine 31 is likely to generate thermal stress, the plant control device 2 has a block for soaking as follows.

The setter 61 holds a set value (30 ° C) of the temperature difference between the temperature of the main steam A6 (hereinafter referred to as "main steam temperature") and the metal temperature. The subtracter 62 acquires the measured value B3 of the metal temperature from the metal temperature sensor 35, and the set value is obtained by the setter 61. The subtracter 62 subtracts the set value of the temperature difference from the measured value B3 of the metal temperature, and outputs the set value D2 of the main steam temperature, that is, "B3-30 °C".

The comparator 63 obtains the measured value D1 of the main steam temperature from the main steam temperature sensor 36, and the set value D2 of the main steam temperature is obtained by the subtracter 62. The comparator 63 compares the measured value D1 of the main steam temperature with the set value D2, and outputs a switching signal D3 corresponding to the comparison result.

The mismatched graph calculation unit 64 acquires the measured value B3 of the metal temperature from the metal temperature sensor 35, and calculates and outputs the initial load soaking time D4 of the steam turbine 31 based on the measured value B3 of the metal temperature. In the comparative example, as will be described later, the initial load soaking time is 90 minutes. After the initial load soaking operation of the steam turbine 31 continues for the initial load soaking time D4, the mismatched graph computing unit 64 outputs the initial load soaking end signal D5.

The reverse gate 65 receives the initial load soaking end signal D5 from the mismatched graph computing unit 64, and outputs the NOT (reverse) calculation result D6 of the initial load soaking end signal D5. Specifically, when the initial load soaking end signal D5 is 1, the NOT operation result D6 becomes 0, and when the initial load soaking end signal D5 is 0, the NOT operation result D6 becomes 1.

The gate 66 receives the switching signal D3 from the comparator 63, and the reverse gate 65 obtains the NOT operation result D6. The gate 66 outputs a switching signal D7 indicating the AND operation result of the switching signal D3 and the NOT operation result D6.

The switch 51 acquires the set value B2 of the exhaust gas temperature at the normal time by the function generator 41, and acquires the set value B4 of the exhaust gas temperature at the time of starting from the lower limit limiter 45, and corresponds to the switching signal D7 from the AND gate 66. The set value C1 of the exhaust gas temperature is output. Hereinafter, the operation of the switch 51 will be described in accordance with the nature of the switching signal D3 and the switching signal D7.

The instruction of the switching signal D3 is changed to the set value D2 (Y) according to the measured value D1 (X) of the main steam temperature, and is changed (X ≧ Y) by whether or not the set value D2 (Y) is reached. Therefore, the instruction of the switching signal D7 changes depending on whether or not the measured value D1 of the main steam temperature reaches the set value D2 and whether the initial load soaking operation of the steam turbine 31 is completed. As will be described later with reference to Fig. 5, the initial load soaking operation end time is later than the measured value D1 of the main steam temperature to reach the set value D2. Therefore, the description of Fig. 3 is limited to the state before the end of the initial load soaking operation. . Therefore, in the description of FIG. 3, the initial load soaking end signal D5 is always 0, and the indication of the switching signal D7 always coincides with the instruction of the switching signal D3.

Therefore, before the measured value D1 reaches the set value D2, the switch 51 maintains the set value C1 at the set value B2 of the exhaust gas temperature at the normal time. On the other hand, when the measured value D1 reaches the set value D2, the switch 51 switches the set value C1 to the set value B4 of the exhaust temperature at the time of starting. The set value C1 is used as a set value (SV value) of the PID control. Hereinafter, the set value C1 is also marked as the SV value.

The average value calculator 52 acquires the measured value C2 of the exhaust gas temperature via each of the exhaust gas temperature sensors 14a in the gas turbine 14. The exhaust temperature sensors 14a are disposed along the circumference of the exhaust portion of the gas turbine 14. The average value calculator 52 calculates and outputs the average value C3 of the measured values C2. The average value C3 is used as the process value (PV value) of the PID control. Hereinafter, the average value C3 is also marked as a PV value.

The subtracter 53 acquires the SV value C1 of the exhaust gas temperature via the switch 51, and acquires the PV value C3 of the exhaust gas temperature by the average value calculator 52. The subtractor 53 subtracts the SV value C1 from the PV value C3, and outputs the deviation C4 of the SV value C1 of the exhaust gas temperature and the PV value C3 (deviation C4 = PV value C3 - SV value C1).

The PID controller 54 acquires the deviation C4 via the subtractor 53, and performs PID control that approximates zero for the deviation C4. The operation amount (MV value) C5 output by the PID controller 54 is the opening degree of the IGV 13b (hereinafter referred to as "IGV opening degree"). If the PID controller 54 changes the MV value C5, the IGV opening degree changes and the exhaust gas temperature changes. As a result, the PV value C3 of the exhaust gas temperature changes in a manner similar to the SV value C1.

As such, the PID controller 54 controls the exhaust temperature by feedback control. Specifically, the PID controller 54 calculates the MV value C5 based on the deviation C4 between the SV value C1 and the PV value C3 of the exhaust gas temperature, and controls the exhaust gas temperature by the control of the MV value C5.

However, if the IGV opening is too small, it may hinder the combustion in the burner 12. Therefore, the MV value C5 is input to the lower limit limiter 55 that holds the lower limit LL (minimum opening) of the IGV opening degree. The lower limit limiter 55 outputs the larger of the MV value C5 and the lower limit value LL as the corrected MV value C6.

The plant control device 2 outputs the MV value C6 and drives the servo valve 17, and controls the IGV opening degree by the hydraulic action of the servo valve 17. As a result, the IGV opening degree changes in accordance with the MV value C6, and the PV value C3 of the exhaust gas temperature changes so as to approach the SV value C1.

Hereinafter, the difference between the set value B2 of the normal exhaust gas temperature and the set value B4 of the exhaust temperature at the time of starting will be described.

The normal setting value B2 of the exhaust gas temperature is used, for example, at the time of starting the power plant 1 until the main steam temperature reaches a predetermined condition. On the other hand, the set value B4 of the exhaust gas temperature at the time of starting is used, for example, at the time of starting the power plant 1, and after the main steam temperature reaches a predetermined condition.

[Set value B2 of the exhaust gas temperature at the normal time] When the power plant 1 of the recirculation type is started, it is preferable to increase the exhaust gas temperature and actively promote the generation of the main steam A6. Therefore, the function curve of the function generator 41 is usually set such that the exhaust gas temperature becomes relatively high.

Therefore, when the set value C1 of the exhaust gas temperature is set to the normal set value B2, the deviation C4 is maintained at a negative value, and the MV value C6 of the IGV opening degree is maintained at the minimum opening degree. That is, immediately after the start of the power plant 1, the IGV opening degree is maintained at the minimum opening degree irrespective of the GT output value. The value of the minimum opening is set, for example, between 30% opening and 50% opening.

[Setting Value B4 of Exhaust Gas Temperature at Startup] On the other hand, the set value B4 of the exhaust gas temperature at the time of starting is used when the main steam temperature is set to a temperature suitable for starting the steam turbine 31. Specifically, when the measured value B1 of the GT output value has reached the initial load, the set value C1 of the exhaust gas temperature is switched from the normal set value B2 to the start setting in order to bring the main steam temperature closer to the metal temperature. The value is B4. The set value B4 is generally given the sum of the measured value B3 of the metal temperature and the set value ΔT of the temperature difference (that is, the exhaust temperature = metal temperature + ΔT).

Accordingly, the mismatch between the main steam temperature and the metal temperature can be reduced. When the steam turbine 31 is ventilated in this state, the steam turbine 31 can obtain the main steam A6 which is less likely to generate thermal stress. The set value ΔT is, for example, 30 °C.

However, if the set value B4 of the exhaust gas temperature becomes a maximum value or an extremely small value, there is a problem in the operation of the gas turbine 14 or the waste heat recovery boiler 21. Therefore, the setting of the set value B4 limits the value of "metal temperature + ΔT" to a value between the upper limit UL and the lower limit LL.

In the above description, an example is described in which the SV value C1 of the exhaust gas temperature is switched from the set value B2 to the set value B4. When the initial load soaking of the steam turbine 31 is completed, the SV value C1 of the exhaust gas temperature is reversely The set value B4 is switched to the set value B2. Specifically, when the initial load soaking is completed, the initial load soaking end signal D5 becomes 1, and the NOT calculation result D6 becomes 0. Therefore, even if the instruction of the switching signal D4 is the set value B4, the instruction of the switching signal D7 becomes the set value. B2. Therefore, when the initial load soaking ends, the switch 51 switches the SV value C1 from the set value B4 to the set value B2. The details of such switching processing will be described below with reference to FIG. 5.

Fig. 5 is a graph showing the operation of the power plant 1 of the first comparative example.

[Time t0] After the generator 16 is parallelized at time t0, the GT output value rises from zero to the initial load (waveform W1). Accordingly, the exhaust gas temperature or the main steam temperature also starts to rise (waveforms W3, W5). At this time, since the measured value D1 of the main steam temperature is lower than the set value D2, the SV value C1 of the exhaust gas temperature is set to the set value B2 at the normal time. Further, since the set value B2 is usually at a high temperature, the deviation C4 is maintained at a negative value, and the IGV opening degree is maintained at a minimum opening degree, that is, P1% (waveform W2). On the other hand, in this comparative example, cold start was performed, and therefore the metal temperature was low (waveform W4).

[Time t1] At time t1, the GT output control unit 56 switches the set value of the GT output value. Therefore, at time t1, the GT output value rises from the initial load to the second output value (waveform W1). According to this, the exhaust gas temperature rises to the set value B2 (waveform W3). On the other hand, the main steam temperature continues to rise (waveform W5).

[Time t2] At the time t2, when the main steam temperature reaches the metal temperature of -30 ° C (waveform W5), the SV value C1 of the exhaust gas temperature is switched to the set value B4 at the time of starting. At this time, since the measured value B3 of the metal temperature is a low temperature (waveform W4), the set value B4 is usually a low temperature. Therefore, the deviation C4 becomes a positive value, and the IGV opening degree rises from P1% to P2% (waveform W2). According to this, the exhaust gas temperature is lowered to the set value B4 (waveform W3). On the other hand, the main steam temperature continues to rise (waveform W5). The opening degree P1% is an example of the first opening degree, and the opening degree P2% is an example of the second opening degree. The opening degrees P1% and P2% are the opening degrees at which the exhaust gas temperature can be maintained at the set value B4 when the GT output value is the first output value and the second output value, and the relationship of P1% < P2% is established. Further, after time t2, the GT output value is also maintained at the second output value (waveform W1).

[Time t3] At time t3, the IGV opening degree reaches P2%, and the exhaust gas temperature reaches the set value B4 (waveforms W2, W3). Further, the main steam temperature reaches the metal temperature (waveform W5) at time t3. The ST output control unit 57 starts the addition and subtraction valve 33 at time t3 to start the ventilation of the steam turbine 31, and gradually increases the opening degree of the addition and subtraction valve 33. In this manner, the steam turbine 31 is started, and the output value of the steam turbine 31 (hereinafter referred to as "ST output value") rises from zero to S1 (5%) (waveform W7).

In the comparative example, since the set value B4 of the exhaust gas temperature is the lower limit value LL (waveform W3), the main steam temperature at the time t3 temporarily becomes a value near the metal temperature (waveform W5). Thereafter, the main steam temperature rises in accordance with the exhaust gas temperature, and the main steam temperature becomes a high temperature higher than the metal temperature. Here, the surface of the rotating shaft 15 (turbine rotor) which is in contact with the high-temperature main steam is at a high temperature, and the inside of the rotating shaft 15 which is not in contact with the high-temperature main steam is maintained at a low temperature. As a result, deformation occurs due to thermal expansion of the rotating shaft 15, and turbine rotor bore thermal stress (hereinafter referred to as "hole thermal stress") is generated in the steam turbine 31. The turbine rotor hole is provided in a cylindrical inner cavity portion (hole) of the rotary shaft 15 (turbine rotor). After time t3, the pore thermal stress increases as the temperature of the main steam rises (waveform W6).

Since the gas turbine 14 and the steam turbine 31 of the comparative example are directly connected to the same rotating shaft 15, the number of revolutions of the steam turbine 31 is increased by the driving of the gas turbine 14. Specifically, the steam turbine 31 is driven by the gas turbine 14 from time t0 to operate at the rated number of revolutions, and continues to operate at time t3. Before the time t3, the addition and subtraction valve 33 is fully closed, and the main steam A6 does not flow into the steam turbine 31. Therefore, the thermal stress of the hole of the steam turbine 31 is not generated to be zero (waveform W6).

The lower limit value LL of the set value B4 of the exhaust gas temperature will be described below. Generally, in the case of aeration of the steam turbine 31, in order to suppress thermal stress, the main steam temperature is preferably close to the metal temperature. Therefore, the adder 43 of the comparative example outputs "B3 + ΔT" as an ideal set value of the exhaust gas temperature. However, in a typical cold start, the metal temperature is a low temperature of 80 ° C to 160 ° C, and the ideal set value of the exhaust gas temperature is constant in the vicinity of 80 ° C to 160 ° C. The exhaust gas temperature is a low temperature at which normal combustion operation cannot be performed. Therefore, the lower limit value LL of this comparative example is set to the lowest temperature exhaust gas temperature at which the gas turbine 14 can normally operate. On the other hand, the ventilation of the steam turbine 31 starts when the main steam temperature temporarily becomes a value near the metal temperature, and thereafter, the main steam temperature has to be increased in accordance with the exhaust gas temperature. In this process, large bore thermal stresses are generated in the steam turbine 31.

Further, the thermal stress generated in the steam turbine 31 may be, for example, thermal stress generated in a hole of the turbine rotor or thermal stress generated on a surface of the rotor of the turbine. When the main steam temperature is higher than the metal temperature, the polarity of the former thermal stress is a positive value, and the polarity of the latter thermal stress is a negative value. The thermal stress of both of the comparative examples is a problem, and the thermal stress (hole thermal stress) of the former is shown as a representative in FIG.

[Time t4] At time t4, the ST output value reaches 5% load (S1) (waveform W7). The initial load soaking of the steam turbine 31 (hereinafter appropriately referred to as "initial load HS") starts, and the ST output value is maintained at 5% load for 90 minutes from time t4. The 5% of the ST output value is an example of a predetermined value of the output value of the steam turbine 31, and the period of 90 minutes is an example of a predetermined period in which the output value of the steam turbine 31 is maintained at a predetermined value. Further, the numerical values of 90 minutes and 5% described herein are examples for convenience of explanation.

The main steam temperature continues to rise until it reaches the vicinity of the exhaust gas temperature (waveform W5). The exhaust gas temperature in the initial load soaking is maintained at a constant temperature (lower limit LL) (waveform W3), and therefore the main steam temperature becomes a constant temperature soon after the initial load soaking. The response of the pore thermal stress to the inflow of the main steam is slightly delayed in time, and therefore the pore thermal stress reaches the first peak Q1 (waveform W6) at a point slightly passing the time t4. However, since the inside of the rotor member is gradually thermally immersed, the thermal stress of the hole is gradually reduced, and the value is maintained at about Q0 as residual thermal stress. In the initial load soaking of this comparative example, the GT output value is held at the second output value (waveform W1), and the IGV opening degree is maintained at P2% (waveform W2). The GT output value of the second output value is an example of a predetermined value of the output value of the gas turbine 14.

Here, the details of the initial load soaking operation will be described.

The steam turbine used in the conventional C/C power plant is driven by the main steam at a pressure of 10 MPa. However, the steam turbine of the recent C/C power plant is going to be large in order to match the high output and high performance of the gas turbine. As the capacity progresses, it is driven by the main steam of high pressure near 15 MPa. As a result, the constituent members of the steam turbine (for example, the turbine rotor or the turbine casing) are required to be able to withstand the physical strength of high pressure, and therefore are composed of a member having a thick thickness.

As described above, the mechanism of thermal stress generation is such that the surface of the member in contact with the main steam at a high temperature becomes a high temperature, and the inside of the member which is not in contact with the main steam at a high temperature is maintained at a low temperature, and as a result, thermal stress is generated based on the deformation of the thermal expansion. Therefore, the more the components of the steam turbine are thick, the more serious the thermal stress becomes.

In the recent start of a steam turbine of a C/C power plant, an initial load soaking operation that is unnecessary when starting a small-capacity steam turbine is also performed. Specifically, when the steam turbine reaches the initial load (usually 3 to 5% of the nominal 100% load is the initial load), the initial load soaking time (usually 60 to 120 minutes of holding time) is maintained at the beginning. The operation of the load. The initial load soaking operation allows a relatively small amount of main steam to continuously flow into the steam turbine, thereby alleviating the problem of thermal stress.

It is assumed that the initial load soaking operation is not performed, and the operation of causing a large amount of main steam to flow into the steam turbine quickly in a short time (specifically, the load is rapidly increased after the steam turbine reaches the initial load) Then, the surface of the turbine component rapidly becomes a high temperature, and on the other hand, the inside of the turbine component is maintained at a low temperature, so that a large thermal stress is generated. More precisely, the interior of the turbine component is gradually transferred to the heat from the surface of the turbine component and gradually becomes a high temperature, but the surface of the turbine component becomes significantly higher and faster than the interior of the turbine component. As a result, the thermal stress of the steam turbine is generated in a transient manner, and the durability (life) of the steam turbine is likely to be greatly depleted.

And such a starter is the first load soaking operation. In the initial load soaking operation, a small amount of main steam flow is introduced into the steam turbine to gradually conduct heat to the member over a long period of time. According to this, the generation of thermal stress can be alleviated, the life of the steam turbine can be delayed by a small thermal stress, and the durability can be extended.

Therefore, how long the initial load soaking time is set is a major problem in the startup of the steam turbine. If the soaking time is set to a long time, the heat is slowly transmitted to the member to alleviate the thermal stress, and the factory start-up time is delayed. Conversely, if the soaking time is set to a short time, the thermal stress becomes large, but the factory start-up time can be shortened. Under such a background, the soaking time of the steam turbine (the execution time of the soaking) is determined based on the economical durability years and the trade-off based on the high-speed startability expected as a commercial machine. The specific example of the above soaking time has a set range of 60 to 120 minutes, taking into account the difference in the model of the steam turbine or the result of the above-mentioned different elements of each power plant.

Also, in terms of reducing thermal stress, it is effective to reduce the main steam flow rate, but the plant start-up time is delayed. Further, in the case where the operation of continuously reducing the main steam flow rate is maintained while maintaining the initial load, the opening degree of the addition and subtraction valve is extremely open, and the valve body is subjected to a load of a large pressure loss or the like. Therefore, in order to reduce thermal stress, it is common to perform the initial load soaking operation as a substitute for reducing the main steam flow rate.

Further, in a steam power plant used for a steam turbine having a larger capacity in a C/C power plant, low-speed soaking and high-speed soaking are generally performed in addition to the initial load soaking. The description of this comparative example describes an example of a C/C power plant that performs primary load soaking.

[Time t5~t7] The initial load soaking at 90 minutes ends at time t5. In the plant control device 2, at time t5, the initial load soaking end signal D5 becomes 1, and the exhaust gas temperature SV value C1 is switched to the set value B2 by the set value B4.

During the period from time t5 to time t7, two starting projects for raising the GT output value to the rated 100% load are started from time t7.

In the first start-up project, the IGV opening degree is reduced from P2% to P1% (minimum opening degree) (waveform W2), and at this time, the exhaust gas temperature rapidly rises from the lower limit value LL at time t5 (waveform W3). . Before the first start-up project, in order to generate the low-temperature exhaust gas temperature of the lower limit LL, the IGV opening degree is set to P2 in the "special operation mode" of the variation permitted by the lower GT output value (second output value). % of the opening. On the other hand, in the first start-up project, in order to increase the GT output value to an output field larger than the second output value, the IGV opening degree is returned to the "normal operation mode", which is a small opening of the so-called P1% opening degree. degree.

In the first start-up project, at time t5, the IGV opening degree is decreased from P2% to P1%, and at time t6 between time t5 and time t7, it reaches P1% (waveform W2). Usually, the period from time t5 to t6 is about three minutes. This is about 3 minutes, which is the time taken for the IGV opening to decrease from P2% to P1% on the IGV 13b mechanism. As the IGV opening degree decreases, the exhaust gas temperature rapidly rises from the lower limit value LL, and reaches the high temperature of the set value B2 at time t6 (waveform W3). Further, since the main steam temperature also rapidly rises in accordance with the exhaust gas temperature (waveform W5), the surface of the rotor member which is in contact with the main steam becomes high temperature, and the internal member of the rotor which is not in contact with the main steam is maintained at a low temperature, and the thermal stress of the display hole is again increased. Tendency (waveform W6). The response of the pore thermal stress is slightly delayed in time with respect to the inflow of the main steam, and therefore the pore thermal stress reaches the second peak Q2 (waveform W6) at a point slightly passing the time t7.

In the second starting project, the ST output value rises from the initial load S1 (5%) (waveform W7), and the bypass regulating valve 34 is fully closed. The bypass regulating valve 34 is a mechanism for fully closing, and is based on an increase in the opening value of the addition and subtraction valve 33 while the ST output value is increased. That is, the main steam A6 via the bypass regulating valve 34 flows into the addition and subtraction valve 33 based on the increase in the opening degree of the addition and subtraction valve 33, and the bypass control valve 34 is fully closed by the pressure control. The ST output value at the time when the bypass regulating valve 34 is fully closed is S2 as shown in FIG.

If the rise of the GT output value from the time t7 occurs in the valve opening of the bypass regulator valve 34, an increase in the GT output value causes an increase in the main steam A6 and an increase in the opening degree of the bypass regulator valve 34. In this case, a part of the main steam A6 is discarded to the condenser 32 via the bypass regulating valve 34 without contributing to power generation, resulting in a problem of unfavorable economy. Further, if the opening degree of the bypass regulating valve 34 is extremely increased, the bypass regulating valve 34 may become fully open. Therefore, it is necessary to set the bypass regulating valve 34 to the fully closed state before the rise of the GT output value from the time t7 by executing the second starting project.

[Time t7~t8] At time t7, the GT output value rises from the second output value to the rated 100% output (waveform W1). The rise of the GT output value is controlled by the GT control unit 56.

As the GT output value increases, the exhaust gas temperature becomes higher than the set value B2, but the temperature change rate of the exhaust gas temperature in this case is slow (waveform W3). The reason is that the increase in the exhaust gas temperature from time t7 causes the opening degree of the fuel regulating valve 11 to gradually increase and the GT output value to increase. Therefore, the IGV opening degree is not reduced from the P2% opening degree to the P1% opening degree. In the case of the case, the exhaust gas temperature rises rapidly.

Therefore, the rise of the main steam temperature from the time t7 is also slow as the exhaust gas temperature (waveform W5), and the hole thermal stress is not greatly increased (waveform W6). The pore thermal stress gradually decreases after reaching the second peak Q2 at a time point slightly passing through the time t7. Further, the ST output value is also increased by the influence of the increase in the heat of the main steam A6 (the increase in the flow rate or the temperature) accompanying the increase in the GT output value (waveform W7).

[Time t8~t10] At time t8, the IGV opening degree increases from P1% to the maximum opening degree (waveform W2). On the other hand, the exhaust gas temperature reaches the maximum temperature (isothermal temperature) at time t8, and the maximum temperature is maintained until the time t9, and is slightly lowered (waveform W3).

At time t10, the GT output value reaches the rated 100% output (waveform W1), and the IGV opening degree reaches the maximum opening degree (waveform W2). The ST output value is slightly delayed in response to the inflow of the main steam, so it reaches the nominal 100% output (waveform W6) at a point slightly past time t10.

(First Embodiment) In the first embodiment, factory control for eliminating or relaxing the second peak Q2 of the hole thermal stress generated in the first comparative example is employed. Here, when thermal stress (hole thermal stress) is generated in the hole of the turbine rotor of the steam turbine 31, thermal stress is also generated on the surface of the turbine rotor of the steam turbine 31. The factory control used in the first embodiment can eliminate or alleviate the thermal stress (hole thermal stress) of the former, and can also eliminate or alleviate the thermal stress of the latter.

As in the description of the first load soaking in the first comparative example, the large thermal stress has a problem that the durability (life) of the steam turbine 31 is greatly lost. As means for alleviating the thermal stress, for example, the temperature change rate of the main steam during the period in which the thermal stress is a problem is made slow. Specifically, the temperature change rate of the main steam can be alleviated by setting the period from time t5 to t6 to be longer. However, when a slow temperature change rate is employed, there is a problem that the power plant 1 takes a long time to become a rated 100% output. In other words, there is a trade-off between the relaxation of the thermal stress (the extension of the number of years of durability) and the shortening of the factory start-up time. In the first embodiment, factory control that can take care of both of these matters is adopted.

Fig. 1 is a schematic view showing the configuration of a power plant 1 according to the first embodiment.

In the plant control device 2 of Fig. 1, in place of the reverse gate 65 and the gate 66 in the mismatched graph calculation unit 64, the graph calculation unit 71 including the mismatch, the reverse gate 72, the gate 73, and the subtractor 74 are replaced. The divider 75, the setter 76, the switch 77, the setter 78, and the rate-of-change limiter 79.

The mismatched graph calculation unit 71 acquires the measured value B3 of the metal temperature by the metal temperature sensor 35, and calculates and outputs the initial load soaking time E1 of the steam turbine 31 based on the measured value B3 of the metal temperature. The initial load soaking time in the present embodiment is, for example, 90 minutes. The mismatched graph calculation unit 71 further outputs the initial load soaking start signal E2 when the initial load soaking operation of the steam turbine 31 is started.

The reverse gate 72 receives the initial load soaking start signal E2 from the mismatched graph computing unit 71, and outputs the NOT operation result E3 of the initial load soaking start signal E2. Specifically, when the initial load soaking start signal E1 is 1, the NOT operation result E3 becomes 0, and when the initial load soaking start signal E1 is 0, the NOT operation result E3 becomes 1.

The gate 73 receives the switching signal D3 from the comparator 63, and the reverse gate 73 obtains the NOT operation result E3. The gate 73 outputs a switching signal E4 indicating the result of the AND operation of the switching signal D3 and the NOT operation result E3.

The switch 51 acquires the set value B2 of the exhaust gas temperature in the normal state by the function generator 41, and acquires the set value B4 of the exhaust gas temperature at the time of starting from the lower limit limiter 45, and corresponds to the switching signal E3 from the AND gate 73. The set value C1 of the exhaust gas temperature is output. Hereinafter, the operation of the switch 51 will be described in accordance with the nature of the switching signal D3 and the switching signal E3.

The indication of the switching signal D3 changes to the set value D2 (Y) corresponding to the measured value D1 (X) of the main steam temperature, and changes (X ≧ Y) if it reaches the set value D2 (Y). Therefore, the indication of the switching signal E3 corresponds to whether or not the measured value D1 of the main steam temperature reaches the set value D2 and whether the initial load soaking operation of the steam turbine 31 starts or changes. As will be described later with reference to Fig. 2, the initial load soaking operation is started after the measured value D1 of the main steam temperature reaches the set value D2. Here, the description of FIG. 1 is first limited to the situation before the start of the initial load soaking operation, and then the situation after the start of the initial load soaking operation is also considered. Therefore, in the description of FIG. 1 herein, it is assumed that the initial load soaking start signal E2 is always 0, and the indication of the switching signal E3 always coincides with the indication of the switching signal D3.

Therefore, before the measured value D1 reaches the set value D2, the switch 51 maintains the set value C1 at the set value B2 of the exhaust gas temperature at the normal time. On the other hand, when the measured value D1 reaches the set value D2, the switch 51 switches the set value C1 to the set value B4 of the exhaust temperature at the time of starting. The set value C1 is used as the set value (SV value) of the PID control, so the following is also referred to as the SV value.

The average value calculator 52 acquires the measured value C2 of the exhaust gas temperature from each of the exhaust gas temperature sensors 14a in the gas turbine 14. The average value calculator 52 calculates and outputs the average value C3 of the measured values C2. The average value C3 is used as the process value (PV value) of the PID control, so the following is also referred to as the PV value.

The subtracter 53 acquires the SV value C1 of the exhaust gas temperature by the switch 51, and acquires the PV value C3 of the exhaust gas temperature by the average value calculator 52. The subtracter 53 subtracts the SV value C1 from the PV value C3, and outputs a deviation C4 between the SV value C1 of the exhaust gas temperature and the PV value C3.

Further, the subtracter 53 accurately obtains the corrected SV value E8 obtained by correcting the SV value C1 instead of acquiring the SV value C1, and outputs the deviation C4 of the corrected SV value E8 and the PV value C3. However, as will be described later, the corrected SV value E8 coincides with the SV value C1 before the start of the initial load soaking operation, and therefore the subtractor 53 operates to output the deviation C4 between the SV value C1 and the PV value C3.

The PID controller 54 obtains the deviation C4 from the subtractor 53, and performs PID control to bring the deviation C4 close to zero. The operation amount (MV value) C5 output by the PID controller 54 is the opening degree (IGV opening degree) of the IGV 13b. If the PID controller 54 changes the MV value C5, the IGV opening degree also changes, and the exhaust gas temperature changes. As a result, the PV value C3 of the exhaust gas temperature changes so as to approach the SV value C1.

However, when the IGV opening is too small, there is a possibility of hindering the combustion in the burner 12. Therefore, the MV value C5 is input to the lower limit limiter 55 that holds the lower limit LL (minimum opening degree) of the IGV opening degree. The lower limit limiter 55 outputs the larger of the MV value C5 and the lower limit value LL as the corrected MV value C6.

The operation of the plant control device 2 is described above in order to limit the situation before the start of the first load soaking operation. Next, the operation of the plant control device 2 will be described in consideration of the situation after the start of the initial load soaking operation.

The subtractor 74 acquires the set value B2 of the exhaust gas temperature at the normal time by the function generator 41, and acquires the set value B4 of the exhaust gas temperature at the time of starting by the lower limit limiter 45. The subtracter 53 subtracts the set value B4 from the set value B2, and outputs the deviation E5 of the set value B2 from the set value B4 (deviation E5 = set value B2 - set value B4).

The divider 75 acquires the deviation E5 by the subtractor 74, and the mismatched chart calculation unit 71 acquires the initial load soaking time E1 of the steam turbine 31. Next, the divider 75 divides the deviation E5 by the initial load soaking time E1, and outputs the division calculation result E6 (division calculation result E6 = deviation E5 ÷ initial load soaking time E1).

As will be described later, the plant control device 2 of the present embodiment raises the exhaust gas temperature from the set value B4 to the set value B2 during the initial load soaking. Therefore, the division calculation result E6 corresponds to the average temperature increase rate (average change rate) of the exhaust gas temperature in the initial load soaking. In the plant control device 2 of the present embodiment, the temperature increase rate of the exhaust gas temperature during soaking is operated so as to approach the average temperature increase rate. Hereinafter, the division calculation result E6 is also referred to as a set value of the temperature increase rate (rate of change) of the exhaust gas temperature.

The setter 76 maintains another set value (1000 ° C / min) of the rate of change of the exhaust gas temperature. The switch 77 acquires the set value E6 of the change rate by the divider 75, and acquires another set value (1000 ° C/min) of the change rate by the setter 76, and corresponds to the initial load soaking of the chart calculation unit 71 from the mismatch. The start signal E2 is output and the limit value E7 of the change rate is output. Specifically, the switch 77 outputs 1000° C./min as the limit value E7 when the initial load soaking start signal E2 is 0, and outputs the set value E6 as the limit value when the initial load soaking start signal E2 becomes 1. E7.

The setter 78 maintains another limit value (-1000 ° C / min) with a rate of change. The rate-of-change limiter 79 acquires the SV value C1 of the exhaust gas temperature by the switch 51, acquires the limit value E7 of the rate of change of the exhaust gas temperature by the switch 77, and obtains another limit of the rate of change of the exhaust gas temperature by the setter 78. Value (-1000 ° C / min).

The rate-of-change limiter 79 operates to limit the rate of change of the SV value C1 between the upper limit value and the lower limit value. Specifically, when the rate of change of the SV value C1 is between the upper limit value and the lower limit value, the change rate limiter 79 directly outputs the SV value C1 as the corrected SV value E8. When the rate of change of the SV value C1 is larger than the upper limit value, the SV value C1 is decreased so that the rate of change becomes the upper limit value, and the reduced SV value C1 is output as the corrected SV value E8. When the rate of change of the SV value C1 is smaller than the upper limit value, the SV value C1 is increased so that the rate of change becomes the lower limit value, and the increased SV value C1 is output as the corrected SV value E8.

The rate-of-change limiter 79 uses the limit value E7 as the upper limit value of the rate of change, and uses -1000 ° C/minute as the lower limit value of the rate of change. Therefore, when the load soaking start signal E2 becomes 0, the upper limit is 1000 ° C / min, and the lower limit is -1000 ° C / min. On the other hand, when the load soaking start signal E2 becomes 1, the upper limit value becomes the set value E6, and the lower limit value becomes -1000 ° C / min.

Here, the value of 1000 ° C / min is a large value that does not occur in practice, and the value of -1000 ° C / min is a small value that does not occur in practice. Therefore, the corrected SV value E8 of the present embodiment is changed by the SV value C1 in accordance with the upper limit value (set value E6) only when the initial load soaking start signal E2 becomes 1.

Further, in the above description, the example in which the SV value C1 of the exhaust gas temperature is switched from the set value B2 to the set value B4 is described. However, at the start of the initial load soaking of the steam turbine 31, the SV value C1 of the exhaust gas temperature is reversed. The set value B4 is switched to the set value B2. Specifically, when the initial load soaking starts, the initial load soaking start signal E2 becomes 1, and the NOT calculation result E2 becomes 0. Therefore, even if the instruction of the switching signal E3 is the set value B4, the instruction of the switching signal E4 becomes the set value B2. Therefore, when the initial load soaking starts, the switch 51 switches the SV value C1 from the set value B4 to the set value B2.

As a result, the IGV opening degree starts to decrease from P2% to P1%, and the exhaust gas temperature rises from the set value B4 to the set value B2. However, the rate-of-change limiter 79 operates by limiting the rate of change of the SV value C1 of the exhaust gas temperature to or lower than the set value E6. Therefore, the exhaust gas temperature gradually rises and the IGV opening degree gradually decreases. According to this, it is possible to suppress a large thermal stress generated in the steam turbine 31 due to a rapid rise in the main steam temperature.

Here, the set value E6 is obtained by dividing the difference between the set value B2 and the set value B4 by 90 minutes (the initial load soaking time E1). Therefore, when the rate of change of the SV value C1 of the exhaust gas temperature is limited to the set value E6 or less, the exhaust gas temperature during the soaking is gradually increased from the set value B4 to the set value B2 within 90 minutes. In order to achieve such a temperature rise, the IGV opening in the soaking is slowly and continuously reduced from P2% to P1% within 90 minutes. The details of such restriction processing will be described with reference to FIG.

Fig. 2 is a graph for explaining the operation of the power plant 1 of the first embodiment.

[Time t3] First, the same processing as in the first comparative example is performed from time t0 to time t3. At time t3, the IGV opening degree reaches P2%, and the exhaust gas temperature reaches the set value B4 (waveforms W2, W3). Further, the main steam temperature reaches the metal temperature (waveform W5) around time t3. Here, the ST output control unit 57 starts the addition and subtraction valve 33 at time t3 to start the ventilation of the steam turbine 31, and gradually increases the opening degree of the addition and subtraction valve 33. According to this, the steam turbine 31 is started, and the ST output value rises from zero to S1 (5%) (waveform W7).

Since the set value B4 of the exhaust gas temperature in the present embodiment is the lower limit value LL (waveform W3), the main steam temperature at the time t3 temporarily becomes a value near the metal temperature (waveform W5). Thereafter, the main steam temperature rises in accordance with the exhaust gas temperature, and the main steam temperature becomes a high temperature higher than the metal temperature. Here, the surface of the rotating shaft 15 (turbine rotor) which is in contact with the high-temperature main steam is at a high temperature, and the inside of the rotating shaft 15 which is not in contact with the high-temperature main steam is maintained at a low temperature. As a result, deformation occurs due to thermal expansion of the rotating shaft 15, and thermal stress is generated in the steam turbine 31. After time t3, the pore thermal stress increases as the main steam temperature rises (waveform W6).

[Time t4] At time t4, the ST output value reaches 5% load (S1) (waveform W7). The initial load soaking of the steam turbine 31 is started, and the ST output value is maintained at 5% load for 90 minutes from time t4. In the plant control device 2, the load soaking start signal E2 becomes 1 at the time t4, and the SV value C1 of the exhaust gas temperature is switched from the set value B4 to the set value B2.

On the other hand, the IGV opening degree corresponds to the initial load soaking start signal E2 and starts to decrease from P2% to P1% at time t4 (waveform W2). Therefore, the exhaust gas temperature rises from the set value B4 (lower limit value LL) to the set value B2 (waveform W3), and the main steam temperature continues to rise so as to reach the vicinity of the exhaust gas temperature (waveform W5).

When the initial load soaking starts, the upper limit value of the rate of change of the SV value C1 of the exhaust gas temperature is limited to the set value E6 in accordance with the initial load soaking start signal E2. The set value E6 is obtained by dividing the difference between the set value B2 of the exhaust gas temperature and the set value B4 by 90 minutes (the initial load soaking time E1). Therefore, the rate of change of the SV value C1 in the initial load soaking does not exceed the upper limit value, so the SV value C1 in the initial load soaking is gradually increased from the set value B4 to the set value B2 (waveform W3) within 90 minutes.

Therefore, the IGV opening degree in the first comparative example is rapidly decreased from P2% to P1% in about 5 to 10 minutes from time t5 to t6, and the IGV opening degree in the present embodiment is 90 minutes from time t4 to t5. The inside is slowly reduced from P2% to P1% (waveform W2). As a result, the main steam temperature also rises slowly within 90 minutes (waveform W5), and the pore thermal stress reaches the first peak Q1' (waveform W6) at a point when the time t4 is slightly passed.

The first peak Q1' of the first embodiment is substantially equal to the first peak Q1 of the first comparative example or slightly larger than the first peak Q1 of the first comparative example. The reason for this is that the rate of change of the main steam temperature in the present embodiment is slightly steeper than that in the first comparative example. However, this difference is not a significant influence on the durability (life) of the steam turbine 31. In the present embodiment, the inside of the rotor member is gradually impregnated with heat after the first peak Q1'. Therefore, even if the pore thermal stress is gradually decreased, there is a residual thermal stress and is maintained at a value of about Q0'. In the initial load soaking of the present embodiment, the GT output value is held at the second output value (waveform W1).

Further, the IGV opening degree in the initial load soaking of the present embodiment is not linear as in the exhaust gas temperature, but changes in a curved shape. The reason is that the relationship between the IGV opening degree and the exhaust gas temperature is not linear. Therefore, when the rate of change of the exhaust gas temperature is made constant, the rate of change of the IGV opening degree is not constant.

[Time t5~t7] The initial load soaking at 90 minutes ends at time t5. Unlike the first comparative example, the IGV opening degree at the time t5 is P1%, and the exhaust gas temperature at the time t5 is the set value B2.

During the period from time t5 to time t7, two starting projects for raising the GT output value to the rated 100% load are started from time t7. In the first comparative example, the first starting project for lowering the IGV opening degree from P2% to P1% and the second starting project for increasing the ST output value from S1 (5%) of the initial load are performed. In the present embodiment, only the second starting project is performed. The reason for this is that in the present embodiment, the work corresponding to the first start-up project has been completed in the initial load soaking.

Therefore, in the period from time t5 to time t7 of the present embodiment, the exhaust gas temperature and the main steam temperature are kept constant (waveforms W3 and W5). As a result, the second peak Q2' of the pore thermal stress appearing at the time point slightly passing through the time t7 is significantly lower than the second peak value Q2 of the first comparative example (waveform W6).

[Time t7~t8] At time t7, the GT output value rises from the second output value to the rated 100% output (waveform W1). The rise of the GT output value is controlled by the GT control unit 56.

As the GT output value increases, the exhaust gas temperature becomes higher than the set value B2, and the temperature change rate of the exhaust gas temperature in this case is slow (waveform W3). The reason for this is that the increase in the exhaust gas temperature from time t7 is caused by gradually increasing the opening degree of the fuel regulating valve 11 to increase the GT output value. Therefore, the IGV opening degree is not opened from P2% in the first comparative example. The degree of decrease is as high as the P1% opening.

Therefore, the rise of the main steam temperature from the time t7 is also slow (waveform W5) as in the exhaust gas temperature, and the hole thermal stress is not greatly increased (waveform W6). The pore thermal stress gradually decreases after reaching the second peak Q2' at a time point slightly passing through the time t7. Further, the ST output value is also increased by the influence of the heat (flow rate or temperature rise) of the main steam A6 which increases as the GT output value increases (waveform W7).

[Time t8~t10] At time t8, the IGV opening degree increases from P1% to the maximum opening degree (waveform W2). On the other hand, the exhaust gas temperature reaches the maximum temperature (isothermal) at time t8, and is slightly lowered (waveform W3) after the maximum temperature is maintained until time t9.

At time t10, the GT output value reaches the rated 100% output (waveform W1), and the IGV opening degree reaches the maximum opening degree (waveform W2). The response time of the ST output value is slightly delayed with respect to the inflow of the main steam, and therefore reaches the rated 100% output (waveform W6) at a point slightly past time t10.

As described above, in the present embodiment, in the initial load soaking of the steam turbine 31, the IGV opening degree is gradually lowered from P2% to P1%. Therefore, according to the present embodiment, the second peak value Q2' of the hole thermal stress can be reduced, and the number of years of durability of the steam turbine 31 can be extended. In the C/C power plant, the frequency of cold start is generally high, and the thermal stress of the hole is likely to be a problem. Therefore, according to the present embodiment, the number of years of durability of the steam turbine 31 of the C/C power plant can be effectively extended. As such, according to the present embodiment, it is possible to perform soaking suitable for a C/C power plant.

[Details of First Embodiment] Next, the details of the power plant 1 according to the first embodiment will be described with reference to Figs. 1 and 2 .

In the starting method of the first comparative example, in the starting process after the initial load soaking, it is necessary to increase the main steam temperature by the "rapid rate of change", and at this time, the thermal stress (second peak Q2) of the large steam turbine is generated. problem. In order to simply moderate the thermal stress, for example, the temperature change rate of the main steam after the initial load is soaked is slow. However, in this case, there is a problem that it takes a long time until the power plant 1 becomes a rated 100% output. That is, usually the thermal stress (durable years) has a trade-off relationship with the factory start-up time.

On the other hand, in the first feature of the present embodiment, in order to prevent the high-speed startability of the power plant 1 and to eliminate or alleviate the thermal stress of the steam turbine 31, it is possible to make the initial load soaking for a relatively long time (for example, 90 minutes). The main steam temperature gradually rises while suppressing thermal stress. That is, unlike the first comparative example, a large thermal stress is concentrated in a short period of time, and the generation of thermal stress is dispersed for a long period of time. As a result, the second peak Q2' of the thermal stress in the present embodiment is remarkably smaller than the second peak Q2 in the first comparative example. Accordingly, the burden on the steam turbine 31 is reduced, and the number of years of durability (life) can be extended. Further, in the present embodiment, even if the occurrence of thermal stress is suppressed as described above, the startup time of the factory is the same as that of the first comparative example.

The second feature of the present embodiment is that the rate of change in the exhaust gas temperature (temperature increase rate) is determined based on the soaking time E1. In the present embodiment, the exhaust gas temperature is linearly increased by limiting the rate of change of the exhaust gas temperature to a value obtained by dividing the difference between the set value B2 of the exhaust gas temperature and the set value B4 by the soaking time E1. As a result, the main steam temperature also rises substantially linearly, and the generation of thermal stress can be smoothed within 90 minutes. As a result, the burden on the steam turbine 31 can be further reduced.

According to a third feature of the embodiment, the main steam temperature is increased by lowering the IGV opening degree. More specifically, in the initial load soaking, the GT output value is maintained at the second output value while the IGV opening degree is lowered to increase the main steam temperature. Hereinafter, the third feature will be described in detail.

The rise in the main steam temperature can be achieved by an increase in the exhaust gas temperature, which can be achieved by 1) increasing the GT output value (i.e., increasing fuel A1), or 2) reducing the IGV opening. Hereinafter, the former is referred to as Method 1, and the latter is referred to as Method 2.

In the case of the method 1, it is conceivable to increase the GT output value from the second output value in the initial load soaking. In this case, for example, when the second output value is set, when all the main steam A6 flows into the condenser 32 via the bypass regulator valve 34, the temperature difference of the circulating water A8 at the inlet and outlet of the condenser 32 does not exceed the maximum value. In the case of the GT output value, there will be no problem.

Specifically, in the startup process before the ventilation of the steam turbine 31, all of the main steam A6 flows into the condenser 32 via the bypass regulator valve 34, so that the burden on the condenser 32 is increased, and the circulating water of the inlet and outlet of the condenser 31 is increased. The temperature difference of A8 becomes larger. In this case, when the second output value is set in consideration of the temperature difference of the circulating water A8 as described above, the temperature difference of the circulating water A8 can be stored in a temperature difference (for example, 7 ° C) that is environmentally acceptable. The output value is controlled. The maximum value of the GT output value that can achieve such control is the second output value in this case.

In this case, in the first method, when the GT output value is increased by the second output value in the initial load soaking, the flow rate of the main steam A6 generated from the drum 22 is increased. This means that the temperature difference of the circulating water A8 exceeds the limit of 7 ° C, causing environmental problems.

However, in order to understand this mechanism, it is necessary to consider that the situation in the initial load soaking and the situation before the ventilation of the steam turbine 31 are similar in terms of the burden of the condenser 32. Specifically, since the initial load is a load of a small load of 3 to 5%, the amount of main steam A6 flowing into the steam turbine 31 during the initial load soaking is small. Therefore, in the initial load soaking, most of the main steam A6 flows into the condenser 32 via the turbine bypass regulating valve 34, so that the condition of the initial load soaking and the steam turbine 31 are large in terms of the burden of the condenser 32. The condition before ventilation is similar.

On the other hand, in the case of the method 2 as in the present embodiment, the exhaust gas temperature is increased by the decrease in the IGV opening degree. Therefore, in the initial load soaking, the exhaust gas temperature can be raised while maintaining the GT output value at the second output value. Therefore, the problem that the temperature difference of the circulating water A8 needs to converge to 7 ° C in the case of the method 1 can be avoided. To be sure, when the flow rate of the fuel A1 is kept constant while reducing the IGV opening degree, the GT output value is only slightly increased, and the flow rate of the main steam A6 is only slightly increased, and the temperature difference of the circulating water A8 does not occur. Big change.

Further, in the present embodiment, when the IGV opening degree is increased, the flow rate of the compressed air A3 is increased, and the exhaust gas temperature is lowered. On the other hand, when the IGV opening degree is reduced, the flow rate of the compressed air A3 is decreased, and the exhaust gas temperature is increased.

However, depending on the model of the gas turbine 14, there is a case where the definition of the IGV opening degree is opposite to the definition of the present embodiment. That is, according to the model of the gas turbine 14, the wings of the IGV 13b are in a "lying down" state, and the flow rate of the compressed air A3 is increased as the IGV opening degree is reduced, and the wings of the IGV 13b are in a "standing" state, and the compressed air A3 is compressed. The decrease in flow is manifested by an increase in IGV opening. The factory control of the present embodiment is also applicable to such a model model. When the factory control of the present embodiment is applied to such a model model, the wing lie is interpreted as an increase in the IGV opening degree, and the wing standing is interpreted as an IGV opening. Degree reduction.

As described above, in the starting method of the present embodiment, the IGV opening degree is lowered during the soaking operation of the steam turbine 31, and the main steam temperature is gradually increased. Therefore, according to the present embodiment, the thermal stress of the steam turbine 31 can be alleviated, and the start of the steam turbine 31 can be realized without wasting or extending the plant start time.

(Second Embodiment) Fig. 6 is a schematic view showing a configuration of a power plant 1 according to a second embodiment.

The power plant 1 of Fig. 6 includes a desuperheating device 24 and a superheater 25 in addition to the components shown in Fig. 1 . Hereinafter, the superheater 23 is also referred to as "primary superheater 23", and the superheater 25 is also referred to as "secondary superheater 25". The primary superheater 23, the desuperheating device 24, and the secondary superheater 25 are constituent elements of the waste heat recovery boiler 21.

The primary superheater 23 receives saturated steam from the drum 22, and superheats the saturated steam by the heat of the exhaust gas A5 to generate primary steam from the saturated steam. The desuperheating device 24 receives the primary steam from the primary superheater 23, and injects the cooling water A9 into the primary steam to cool the primary steam. The secondary superheater 25 receives primary steam from the temperature reducing device 24, and superheats the primary steam by the heat of the exhaust gas A5 to generate secondary steam from the primary steam. The waste heat recovery boiler 21 discharges the secondary steam as the main steam A6.

Fig. 6 shows the plant control device 2 at three locations, which represent the same plant control device 2. The plant control device 2 shown in Fig. 6 has the same components as the plant control device 2 shown in Fig. 1 . Further, the plant control device 2 shown in Fig. 6 outputs a signal E9 for controlling the opening/closing or opening degree of the valve (cooling water flow rate adjusting valve) for the cooling water A9. When the valve is opened corresponding to the signal E9, the steam is injected into the desuperheating device 24 by the cooling water A9 of the valve.

In the factory control method of the second embodiment, the first peak Q1' (Fig. 2) of the pore thermal stress generated in the factory control method of the first embodiment can be further alleviated. Hereinafter, the details of the factory control method of the second embodiment will be described.

In the first embodiment, the IGV opening degree is controlled such that the exhaust gas temperature rises from the set value B4 to the set value B2 between 90 minutes of the initial load soaking. In this case, B2 is the temperature before starting (venting) the steam turbine 31, and is urging the higher temperature of the early main steam generation.

However, it is not always necessary to raise the exhaust gas temperature to B2 at a high temperature in the initial load soaking. The factory control method of the second embodiment corresponds to this example. In the second embodiment, the IGV opening degree is controlled such that the exhaust gas temperature rises from the set value B4 to the set value B5 between 90 minutes of the initial load soaking. Here, B5 of the second embodiment is lower than the low temperature of B2 (B5 < B2).

In the plant control device 2, the main steam temperature sensor 36 obtains the measured value D1 of the main steam temperature, that is, the temperature of the main steam (secondary steam) A6, and compares the measured value D1 with the critical value. The critical value is, for example, 560 °C. When the measured value D1 is smaller than the critical value, the plant control device 2 closes the valve for the cooling water A9, and when the measured value D1 is equal to or greater than the critical value, the plant control device 2 opens the valve for the cooling water A9. The mode outputs the signal E9. As a result, when the measured value D1 is equal to or greater than the critical value, the temperature reducing device 24 injects the cooling water A9 into the primary steam. This threshold value is an example of the first temperature.

The set value B5 of the second embodiment is determined based on the threshold value, and specifically, is determined to be the same value as the threshold value. Therefore, the set value B5 is, for example, 560 °C. The set value B5 is an example of the second temperature.

Hereinafter, the details of the desuperheating device 24 will be described.

In the power plant 1 not including the desuperheating device 24, when the load soaking end exhaust gas temperature becomes B2, the temperature of the main steam A6 gradually approaches B2. Therefore, the waste heat recovery boiler 21 must be manufactured using high-priced materials capable of withstanding the main steam A6 having a high temperature of B2.

On the other hand, in the power plant 1 of the present embodiment, the temperature of the main steam A6 is cooled to B5 or less by injecting the cooling water A9 by the desuperheating apparatus 24. This is the desuperheating spray control of the main steam A6 by the cooling water A9, and the temperature setting value (SV value) of the control is B5 [°C]. Moreover, correctly speaking, B5 is not the set value of the temperature reduction spray control, but the set value of the exhaust gas temperature at the end of the initial load soaking. In the present embodiment, both are the same value (540 ° C), so B5 is also It is called the temperature setting value of the desuperheating spray control.

The plant control device 2 increases/decreases the opening degree of the cooling water flow rate adjusting valve, and injects the cooling water A9 so that the temperature of the main steam A6 becomes B5 or less. According to this, although the thermal efficiency (performance) of the plant is slightly sacrificed, the waste heat recovery boiler 21 does not have to have heat resistance capable of maintaining the high temperature of B2, and it is only required to have heat resistance of B5 temperature which can withstand lower temperatures, and thus the waste heat recovery boiler 21 Manufacturing costs can be reduced.

In recent years, power plants tend to be economical and environmentally friendly, and in the latest gas turbines, performance is significantly improved by the high temperature of the turbine inlet temperature (combustion temperature). Therefore, the exhaust gas temperature is also higher than that of the conventional gas turbine in each load zone. In such a trend, the cooling by the desuperheating device 24 of the present embodiment is sufficiently economically justified.

The advantage of the desuperheating device 24 is that, for example, even when the exhaust gas temperature is a high temperature of B5 or higher, the temperature rise of the main steam A6 is suppressed to a temperature at which B5 is the upper limit. When the thermal stress of the turbine rotor is directly generated, the rise of the main steam A6 is not caused by the rise of the exhaust gas temperature. When the focus is on this point, the exhaust gas temperature is increased to B2 as in the first embodiment, as in the second embodiment. It is wasteful to set the condition of the desuperheating device 24. In other words, the exhaust gas temperature in the present embodiment can be increased to B5, and the rate of increase in the exhaust gas temperature can be reduced in accordance with such temperature rise. Hereinafter, such a rate of increase will be described.

Fig. 7 is a chart for explaining the operation of the power plant 1 of the second embodiment.

[Time t2] First, the same processing as in the first embodiment is performed from time t0 to time t2. As a result, the set value B2 of the IGV exhaust gas temperature control from time t1 to time t2 is maintained at a high temperature, and the IGV opening degree is maintained at P1% of the minimum opening degree.

In the initial stage of the starting, it is preferable to make the exhaust gas temperature high in an allowable range so that the steam is generated by the drum 22 as quickly as possible. Therefore, at the time when the initial load soaking of the post-engineering is completed [time t5], the exhaust gas temperature rises only to the low temperature B5, but at the time t2, the high temperature B2 is the same as in the first embodiment (Energetic The waste heat recovery boiler 21 is boiled. Such boiling is possible because the main steam temperature is low at the stage of time t2.

[Time t3] Next, from the time t2 to the time t3, the same processing as in the first embodiment is performed. At time t3, the IGV opening degree reaches P2%, and the exhaust gas temperature is lowered to the set value B4 (waveforms W2, W3). Further, the main steam temperature reaches the metal temperature (waveform W5) at about time t3. The addition and subtraction valve 33 is opened at time t3 to start the ventilation of the steam turbine 31, and the opening degree of the addition and subtraction valve 33 is gradually increased. According to this, the steam turbine 31 is started, and the ST output value rises from zero to S1 (5%) (waveform W7).

Further, in the present embodiment, the cold start is performed. Therefore, in this stage, the main steam temperature (base metal temperature) is sufficiently low compared to the temperature set value B5 of the main steam desuperheating spray control, and the cooling water A9 is not started. injection.

Similarly to the first embodiment, the main steam temperature rises in accordance with the exhaust gas temperature, and as a result, pore thermal stress is generated in the steam turbine 31. After time t3, the pore thermal stress increases as the main steam temperature rises (waveform W6).

[Time t4] At time t4, the ST output value reaches 5% load (S1) (waveform W7). Next, the initial load soaking of the steam turbine 31 is started, and the ST output value is maintained at 5% load for 90 minutes from time t4. Next, at time t4, after the initial load soaking starts, the set value of the exhaust gas temperature control is switched to the set value B5 from the set value B4. This operation is a control different from that of the first embodiment. In the first embodiment, the set value B4 is switched to the set value B2, whereas in the second embodiment, the set value B4 is switched to the set value B5. Such a switching can be realized, for example, in the switch 51 of FIG. 1 by using a terminal for B2 and a terminal for B4 as an input terminal.

On the other hand, the IGV opening degree is lowered from P2% to P3% at time t4 in response to the start of the initial load soaking (waveform W2). Therefore, the exhaust gas temperature rises from the set value B4 to the set value B2 (waveform W3), and the main steam temperature rises in accordance with the exhaust gas temperature (waveform W5).

Hereinafter, the rate of increase of the exhaust gas temperature in the initial load soaking of the present embodiment is compared with the first embodiment. The SV value C1 of the exhaust gas temperature control of the first embodiment is increased from the set value B4 to the set value B2 between 90 minutes of the initial load soaking. Therefore, the rate of increase in the exhaust gas temperature in the first embodiment is (B2-B4) ÷ 90 [° C / min]. On the other hand, the rate of increase in the exhaust gas temperature in the second embodiment is (B5 - B4) ÷ 90 [° C / min]. As described above, since B2 < B2 is established between B2 and B5, the rate of increase of the second embodiment is smaller than that of the first embodiment.

As the temperature of the exhaust gas rises, the main steam temperature also rises slowly between 90 minutes (waveform W5), and the pore thermal stress reaches the first peak Q1" (waveform W6) at a time when the time t4 is slightly passed. The second embodiment In the first embodiment, the increase in the exhaust gas temperature is slower than in the first embodiment. Therefore, the increase in the main steam temperature is slower than in the first embodiment. As a result, the first peak Q1" of the second embodiment is relatively the same. The first peak Q1' of the first embodiment is small.

Further, in the second embodiment, when the injection of the cooling water A9 is started by the main steam desuperheating spray control, the main steam temperature is maintained at a constant B5, and the pore thermal stress of the steam turbine 31 is no longer increased. This point is re-expressed at times t5 to t6 which will be described later. When the plant control method according to the first embodiment is applied to the power plant 1 having the second embodiment of the desuperheating device 24, the exhaust gas temperature rises from B4 to B5 but not from B4 to B2 in the initial load soaking (B4). <B5<B2). However, in the period in which the exhaust gas temperature rises from B5 to B2, the main steam temperature has been maintained at B5, so that it is meaningless to slowly increase the exhaust gas temperature in the band in consideration of the pore thermal stress. It is better to consider the period during which the exhaust gas temperature should be gradually increased in consideration of the pore thermal stress, and it is more suitable to increase the exhaust gas temperature from B4 to B5. Therefore, in the second embodiment, the exhaust gas temperature is raised as described above.

Further, similarly to the first embodiment, the IGV opening degree in the initial load soaking of the present embodiment is not linear as in the exhaust gas temperature, but is changed to a curved shape. The reason for this is that the relationship between the IGV opening degree and the exhaust gas temperature is not linear. Therefore, when the rate of change of the exhaust gas temperature is made constant, the rate of change of the IGV opening degree cannot be made constant.

[Time t5~t7] At time t5, the initial load soaking between 90 minutes ends. Unlike the first embodiment, the IGV opening degree at the time t5 is P3%, and the exhaust temperature at the time t5 is the set value B5. In the plant control device 2 of the present embodiment, the exhaust gas temperature at the time t5 is set to the set value B5, and the IGV opening degree is lowered from P2% to P3% (P2%>P3%) in the initial load soaking. Since the magnitude relationship between the set value B5 and the set value B2 is B5 < B2, the magnitude relationship of the IGV opening degree is P3%>P1%. This P3% is an example of the third opening degree.

During the period from time t5 to time t7, two starting projects are started to raise the GT output value to the rated 100% load from time t7. In the second embodiment, based on the same reason as in the first comparative example, the first starting project for lowering the IGV opening degree from P3% to P1% is performed, and the ST output value is increased from the initial load S1 (5%). The second starting project.

Therefore, in the period from time t5 to time t6 of the present embodiment, as in the first comparative example, the exhaust gas temperature rises. Specifically, the exhaust gas temperature starts to rise from B5 at time t5, and reaches B2 (waveform W3) at time t6. On the other hand, the main steam temperature following the exhaust gas temperature reaches B5 (waveform W5) at a time point slightly past time t5.

When the main steam temperature reaches B5, the injection of the cooling water A9 is started by the main steam desuperheating spray control, and the subsequent main steam temperature is maintained at a constant value even if the exhaust gas temperature rises (B5). In this regard, this embodiment is different from the first comparative example.

The hole thermal stress of the steam turbine 31 is caused by an increase in the temperature of the main steam. Therefore, after the main steam temperature is maintained at B5, even if the exhaust gas temperature rises steeply, the thermal stress of the hole of the steam turbine 31 does not increase. Therefore, in the first comparative example, the pore thermal stress starts to rise from the time t5, and the pore thermal stress of the present embodiment is maintained at about the residual thermal stress Q0" with respect to the first comparative example.

[Time t7~t8] At time t7, the GT output value rises from the second output value to the rated 100% output (waveform W1). Further, the ST output value is also increased by the influence of the heat (increased flow rate) of the main steam A6 which increases as the GT output value increases (waveform W7).

As the GT output value increases, the exhaust gas temperature becomes higher than the set value B2. However, as described above, since the main steam temperature is maintained at B5, the thermal stress of the hole of the steam turbine 31 is maintained at about the residual thermal stress Q0". In the first embodiment, the thermal stress at the point of the point t7 is slightly increased. In contrast to this, in the second embodiment, the second peak corresponding thereto is not generated. Thus, according to the second embodiment, the possibility of occurrence of the second peak of the thermal stress of the hole can be suppressed.

Finally, the details of the second embodiment will be added.

In the second embodiment, the steam generated by the energy of the fuel A1 is cooled by the cooling water A9, and the thermal efficiency (performance) of the plant is sacrificed. However, in the latest gas turbines, the temperature of the turbine inlet (combustion temperature) tends to increase. In such a latest gas turbine, even if the exhaust gas temperature is the set value B2 at the time of low load operation, it also appears to be the highest exhaust gas temperature (usually compared to the rated 100% base load system at the intermediate load). The role of the band) is not inferior to the high temperature characteristics. In the power plant 1 having such a latest gas turbine, even if the cooling water A9 is injected in accordance with B5, which is a lower temperature setting value than B2, only a slight deterioration in the thermal efficiency of the plant occurs. For example, when B2 is a combination of the latest gas turbine in the vicinity of 600 ° C and the main steam desuperheating spray control in which B5 is 560 ° C, the thermal stress of the steam turbine 31 can be alleviated, and the efficiency reduction also converges within the tolerance range.

On the other hand, depending on the type of the gas turbine 14, there is a case where the above-described characteristics are not present and the set value B2 at the time of low-load operation is low. The second embodiment is applied to a power plant 1 including such a gas turbine 14, and B5 which is lower in temperature than the set value B2 is used, which cannot be tolerated in a commercial power plant that is economical. In such a case, it is conceivable to switch the temperature setting value of the main steam desuperheating spray control in two stages. For example, the low temperature temperature set value B5 is applied only in the initial load soaking, and the high temperature temperature set value B5' is used in other periods. In the case of such a method, it is also expected that the thermal stress of the steam turbine 31 is not excessively large. In view of this, for example, the method of the following third embodiment can be employed.

(Third Embodiment) Hereinafter, a power plant 1 according to a third embodiment will be described with reference to Fig. 6 . In the following description, the configuration of the plant control device 2 or the symbol related to the configuration is referred to FIG. 2, and the operation of the power plant 1 or the symbol associated with the operation is referred to FIG.

In the plant control device 2 of the second embodiment, the exhaust gas temperature at the time t5 is set to the set value B5, and the IGV opening degree is lowered from P2% to P3% (P2%>P3%) in the initial load soaking. The set value B5 is, for example, 560 °C. Since the magnitude relationship between the set value B5 and the set value B2 is B5 < B2, the magnitude relationship of the IGV opening degree is P3%>P1%.

On the other hand, in the plant control device 2 of the third embodiment, the exhaust gas temperature at the time t5 is set to the set value B6, and the IGV opening degree is lowered from P2% to P4% in the initial load soaking (P2%>P4). %). The set value B6 is, for example, 540 °C. Since the magnitude relationship between the set value B6 and the set value B2 is B6 < B2, the magnitude relationship of the IGV opening degree is P4%>P1%. The P4% system and P3% are also examples of the third opening degree.

Further, the power plant 1 according to the third embodiment may include the desuperheating device 24 and the superheater 25, or may not include the desuperheating device 24 and the superheater 25.

The details of the set value B6 will be described below.

B6 of the present embodiment is determined based on the metal temperature of the steam turbine 31 in the case where the startup of the steam turbine 31 is defined as a hot start in the mismatch diagram, specifically, the metal temperature is added. It is decided by appropriate margin. The metal temperature is an example of the third temperature, and is, for example, 500 °C. B6 is an example of the fourth temperature, and is, for example, 540 °C. B6 of the present embodiment is determined by adding a constant value of 500 ° C to a constant value of 40 ° C.

The starting mode of the steam turbine 31 includes a cold start, a warm start, a hot start, and the like. These systems are assigned a defined starting mode corresponding to the metal temperature of the steam turbine 31. A cold start is usually defined as a start mode of a temperature band with a metal temperature of about 300 ° C or less. On the other hand, a warm start is usually defined as a start mode in which the inner metal temperature is approximately over 300 ° C (but above 500 ° C is a hot start).

In the same manner as the factory control method according to the first and second embodiments, the factory control method of the present embodiment is applied to a cold start having a long initial load soaking time (90 minutes) in the starting process. However, in the present embodiment, focusing on the thermal stress behavior of the hot start, the content of the hot start is taken into the factory control method at the time of cold start.

The mismatched chart calculation unit 71 has a chart of mismatch. A specific example of the mismatch chart is generally known, for example, the initial load hold time (initial load soak time) is specified by the mismatch chart. According to an example of the mismatch chart, when the metal temperature of the steam turbine 31 is higher, the initial load soaking time is decreased, and during the hot start, the initial load soaking time becomes zero. In this case, it is not necessary to perform the initial load soaking in the starting process of the hot start.

The metal temperatures defined and classified according to the hot start differ depending on each model type of the steam turbine 31. As described above, the recent factory-controlled mismatch chart generally defines a high temperature band in which the metal temperature measured before the ventilation of the steam turbine 31 is around 500 ° C or 500 ° C or more is a hot start. Therefore, in the present embodiment, the case where the metal temperature before the ventilation is 500 ° C or higher is defined as a hot start, but other definitions may be employed.

Usually, the initial load soaking operation causes a small amount of main steam A6 to flow into the steam turbine 31, and it takes a long time to gradually transfer heat from the main steam A6 to the turbine rotor to alleviate the generation of thermal stress. On the other hand, in the hot start, since the metal temperature is maintained at a high temperature of 500 ° C or higher, even if the main steam A 6 having a higher temperature than the metal temperature flows into the steam turbine 31 , the turbine rotor does not cause severe thermal stress. Therefore, there is no need for the initial load soaking operation in the hot start.

The third embodiment focuses on this fact. Specifically, at the point (t5) at the end of the initial load soaking, the starting process of raising the metal temperature of the steam turbine 31 to 500 ° C is performed. This is because the state of the steam turbine 31 is in a cold start state at the start of the ventilating, but the point is converted to the hot start state at the end of the initial load soaking, and the so-called pseudo-hot start can be realized. Then, in the startup process after the end of the initial load soaking, the exhaust gas temperature or the main steam temperature rises, but the high metal temperature of 500 ° C is maintained in the same manner as the hot start, so that the steam turbine 31 flows into the high temperature main steam temperature. The turbine rotor is also not subject to excessive thermal stress.

In the present embodiment, the IGV opening degree is controlled to increase the exhaust gas temperature to the set value B6 between 90 minutes of the initial load soaking, thereby realizing a pseudo hot start. In the present embodiment, the set value B6 is set to 540 ° C at a metal temperature of hot start, that is, 500 ° C, for example, a margin of 40 ° C is added.

The 40 ° C temperature is set, for example, in consideration of a temperature deviation between the exhaust gas temperature and the main steam temperature or a temperature deviation between the main steam temperature and the metal temperature. That is, when the exhaust gas temperature rises, the main steam temperature also rises following the exhaust gas temperature, and the metal temperature also rises following the main steam temperature. Therefore, in these rises, the main steam temperature is slightly lower than the exhaust gas temperature, and the metal temperature is slightly lower than the main steam temperature. In other words, the main steam temperature is delayed from the exhaust gas temperature, and the metal temperature is delayed from the main steam temperature. Further, it should be noted that only the metal temperature (W4) before the ventilation of the steam turbine 31 is shown in FIGS. 2, 5, and 7.

The rise of the main steam temperature with respect to the rise of the exhaust gas temperature is delayed, or the rise of the metal temperature with respect to the rise of the main steam temperature is delayed, and is a value inherent to each power plant 1. However, the delay points are different values according to the time zone on the start-up project (for example, the end period of the initial stage of the initial load soaking). Typically, these delays are estimated to be between 20 ° C and 60 ° C. Therefore, in the present embodiment, the rise delay of the increase in the metal temperature with respect to the exhaust gas temperature is assumed to be 40 ° C, and the above-described margin is set to 40 ° C. On the other hand, the delay score can be defined with good accuracy according to the actual test operation of the steam turbine 31, etc., and the delay value thus defined can be added to 500 ° C to determine the set value B6.

Hereinafter, the third embodiment will be compared with the second embodiment.

In the above embodiments, an example in which the set value B5 is set to 560 ° C or an example in which the set value B6 is set to 540 ° C will be described. The values of 560 ° C and 540 ° C are only examples. In most cases, the relationship of B5>B6 can be considered. The reason is as follows.

In the heat balance of a suitable commercial double-cycle power plant, the set value B5 of the main steam desuperheating spray control is higher than the metal temperature (for example, 500 ° C) defined as the hot start. plan. The reason for this is that the main steam temperature is actually determined by setting the set value B5 of the main steam desuperheating spray control as the upper limit value. Considering that the set value B5 is assumed to be lower than 500 ° C, the main steam temperature and the metal temperature do not exceed 500 ° C, and the definition of hot start is meaningless. Therefore, in general, the set value B5 is set to be higher than 500 ° C, and even if the margin is added at 500 ° C (for example, 40 ° C), the set value B6 is lower than the set value B5.

As described above, in the plant control method according to the first to third embodiments, the IGV opening degree is reduced during the soaking operation of the steam turbine 31, and the main steam temperature is increased at a slow temperature change rate. Therefore, according to these embodiments, the thermal stress of the steam turbine 31 can be alleviated, and a starting method that imposes less load on the steam turbine 31 without sacrificing the plant start time can be employed.

The embodiments are described above, and the embodiments are merely illustrative and are not intended to limit the scope of the invention. The new gauge device, method, and factory described in this specification can be implemented in various other forms. It is to be understood that the various modifications, substitutions and changes may be made without departing from the scope of the invention. The scope of the appended claims and the scope of the invention are intended to be in the

1‧‧‧Power Plant

2‧‧‧Factory control unit

11‧‧‧ fuel regulating valve

12‧‧‧ burner

13‧‧‧Compressor

13a‧‧‧ entrance

13b‧‧‧inlet guide wings

14‧‧‧ gas turbine

14a‧‧‧Exhaust temperature sensor

15‧‧‧Rotary axis

16‧‧‧Generator

17‧‧‧ Servo valve

18‧‧‧Compressed air temperature sensor

19‧‧‧Output sensor

21‧‧‧Waste heat recovery boiler

22‧‧‧Roller

23‧‧‧Superheater (primary superheater)

24‧‧‧Warming device

25‧‧‧Superheater (secondary superheater)

31‧‧‧ steam turbine

31a‧‧‧ Rotator

31b‧‧‧fixer

31c‧‧‧ steam inlet

31d‧‧‧Steam outlet

32‧‧‧Condenser

33‧‧‧plus and minus valves

34‧‧‧Bypass control valve

35‧‧‧Metal temperature sensor

36‧‧‧Main steam temperature sensor

41‧‧‧ function generator

42‧‧‧Setter

43‧‧‧Adder

44‧‧‧ upper limiter

45‧‧‧lower limiter

51‧‧‧Switcher

52‧‧‧Average Operator

53‧‧‧Subtractor

54‧‧‧PID controller

55‧‧‧ Lower limiter

56‧‧‧GT Output Control Department

57‧‧‧ST output control unit

61‧‧‧Setter

62‧‧‧Subtractor

63‧‧‧ comparator

64‧‧‧ mismatched charting department

65‧‧‧Reverse gate

66‧‧‧ and gate

71‧‧‧ mismatched charting department

72‧‧‧ reverse gate

73‧‧‧ and gate

74‧‧‧Subtractor

75‧‧‧ divider

76‧‧‧Setter

77‧‧‧Switcher

78‧‧‧Setter

79‧‧‧Change rate limiter

Fig. 1 is a schematic view showing a configuration of a power plant according to a first embodiment. Fig. 2 is a graph showing the operation of the power plant of the first embodiment. Fig. 3 is a schematic view showing a configuration of a power plant of a first comparative example. Fig. 4 is a cross-sectional view showing the structure of a steam turbine of a first comparative example. Fig. 5 is a graph showing the operation of the power plant of the first comparative example. Fig. 6 is a schematic view showing a configuration of a power plant according to a second embodiment. Fig. 7 is a graph showing the operation of the power plant of the second embodiment.

Claims (14)

A plant control device for controlling a power plant, the power plant having: a burner for simultaneously generating oxygen by injecting oxygen and fuel introduced by the inlet guide vane; and the gas turbine being driven by the gas from the burner a waste heat recovery boiler that generates heat by using heat from the exhaust gas of the gas turbine; and a steam turbine that is driven by the steam from the waste heat recovery boiler; the plant control device includes: a first output control unit that is connected to the gas turbine The output value of the steam turbine is controlled, and the output value of the steam turbine is controlled, and the output value of the steam turbine is maintained at a predetermined value for a predetermined period of time. The plant control device further includes: an opening degree The control unit controls the opening degree of the inlet guide vane before the start of the steam turbine to a first opening degree, and controls the opening degree of the inlet guide vane after the start of the steam turbine to be larger than the first opening degree. The second opening degree during the above specified period An inlet guide blade so that the opening degree of reduction by the second opening of the first opening, to reduce or larger than the first opening and the second opening smaller than the opening degree of the third degree. The plant control device according to the first aspect of the invention, wherein the second output control unit causes the opening degree of the inlet guide vane to be the second opening degree at the start of the predetermined period, and at the end of the predetermined period The opening degree of the inlet guide vane is changed to the first opening degree or the third opening degree, and the opening degree of the inlet guide vane is continuously decreased from the second opening degree to the first opening in the predetermined period. Degree or the third opening degree mentioned above. The plant control device according to the first or second aspect of the invention, wherein the opening degree control unit calculates a set value of a temperature increase rate of the temperature of the exhaust gas in the predetermined period, and the above-described temperature increase rate is set based on the set value of the temperature increase rate. The opening of the inlet guide is controlled. In the plant control device according to the third aspect of the invention, the opening degree control unit is configured to set a temperature of the exhaust gas at a start of the predetermined period and a temperature of the exhaust gas at the end of the predetermined period. The difference between the set values is divided by the predetermined period, and the set value of the temperature increase rate is calculated. The plant control device according to claim 4, wherein the set value of the temperature of the exhaust gas at the start of the predetermined period is a temperature of the exhaust gas when the opening degree of the inlet guide vane becomes the second opening degree The set value of the temperature of the exhaust gas at the end of the predetermined period is a set value of the temperature of the exhaust gas when the opening degree of the inlet guide vane is the first opening degree or the third opening degree. . The plant control device according to claim 1 or 2, wherein the first output control unit maintains an output value of the gas turbine at a predetermined value during the predetermined period. A plant control device according to claim 1 or 2, wherein the predetermined period is a period in which the soaking of the steam turbine is performed. The plant control device according to claim 1 or 2, wherein the waste heat recovery boiler includes: a primary superheater that generates primary steam by using heat of the exhaust gas; a desuperheating device that injects cooling water into the primary steam; a secondary superheater that generates secondary steam from the primary steam by the heat of the exhaust gas; the steam turbine is driven by the secondary steam from the waste heat recovery boiler, and the temperature reducing device is based on the secondary steam As a result of the comparison between the temperature and the first temperature, the first steam is injected into the cooling water, and the opening degree control unit sets the temperature of the exhaust gas at the end of the predetermined period to be the second temperature determined based on the first temperature. The temperature is such that the opening degree of the inlet guide vane is lowered from the first opening degree to the third opening degree in the predetermined period. The plant control device according to the eighth aspect of the invention, wherein the temperature reducing device is configured to inject the cooling water into the primary steam when the temperature of the secondary steam is higher than the first temperature, and the opening degree control unit When the temperature of the exhaust gas at the end of the predetermined period is the first temperature, the opening degree of the inlet guide vane is lowered from the first opening degree to the third opening degree in the predetermined period. The plant control device according to the first or second aspect of the invention, wherein the opening degree control unit sets the metal temperature of the steam turbine at the end of the predetermined period to a third temperature, and the above-mentioned predetermined period ends. The temperature of the exhaust gas is a fourth temperature determined based on the third temperature, and the opening degree of the inlet guide vane is lowered from the first opening degree to the third opening degree in the predetermined period. The plant control device according to claim 10, wherein the third temperature is defined as a temperature of the metal in the case where the startup of the steam turbine is a mismatch. A plant control device according to claim 10, wherein the fourth temperature is higher than the third temperature. A plant control method is for controlling a power plant, the power plant having: a burner that simultaneously combusts oxygen and fuel introduced by the inlet guide vane to generate a gas; the gas turbine is driven by the gas from the burner a waste heat recovery boiler that generates heat using heat from the exhaust gas of the gas turbine; and a steam turbine that is driven by the steam from the waste heat recovery boiler; the plant control method, the first output control unit to the gas turbine The output value is controlled such that the output value of the steam turbine is maintained at a predetermined value for a predetermined period of time, and the output value of the steam turbine is controlled by the second output control unit to control the steam turbine before starting The opening degree of the inlet guide vane is controlled to be the first opening degree, and the opening degree of the inlet guide vane after the start of the steam turbine is controlled to be a second opening degree larger than the first opening degree, and is made in the predetermined period. The opening degree of the inlet guide vane is lowered from the second opening degree to the first one Degrees, or reduced to a large degree than the first opening and the second opening smaller than the opening degree of the third degree. A power plant comprising: a burner for simultaneously generating combustion of oxygen and fuel introduced by an inlet guide vane; a gas turbine driven by the gas from the burner; a waste heat recovery boiler utilizing exhaust gas from the gas turbine The steam generating turbine is driven by the steam from the waste heat recovery boiler; the first output control unit controls the output value of the gas turbine; and the second output control unit controls the output of the steam turbine. The value is controlled, and the output value of the steam turbine is maintained at a predetermined value for a predetermined period of time; and the opening degree control unit controls the opening degree of the inlet guide vane before the start of the steam turbine to be the first opening degree. The opening degree of the inlet guide vane after the start of the steam turbine is controlled to be a second opening degree larger than the first opening degree, and the opening degree of the inlet guide vane is lowered by the second opening degree in the predetermined period. The first opening degree or the third opening is larger than the first opening degree and smaller than the second opening degree. Degree.