JPS60252108A - Turbine load control method for reheating steam turbine plant - Google Patents

Abstract

PURPOSE:To control the exhaust temperature of a high pressure turbine at the time of starting by controlling the change rate of switched load between the switching start load and the end load according to the follow-up capacity of the evaporation on boiler side when an adjustable valve of a high pressure turbine is opened to increase load. CONSTITUTION:A reheating steam turbine plant includes a high pressure by-pass system, a low pressure by-pass system and a ventilator system extending from high pressure turbine exhaust side to a condenser, wherein a switch load band extending from the switching start load to the switching end load is provided in a process of opening an adjustable valve of a high pressure turbine to increase load. When a target load is input to a control device, load is automatically set out of the switch load band L1-L3, and simultaneously, in consideration of the follow-up capacity of evaporation on boiler side, the change rate P of switched load in the switch load band is set. Thus, turbine load can be controlled in cooperation with a boiler.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention provides a boiler having a reheater, a high-pressure bypass system, a low-pressure bypass system, and a ventilator system extending from the exhaust side of a high-pressure turbine to a condenser. The present invention relates to a turbine load control method for a reheat steam turbine plant equipped with a reheat steam turbine plant, and is particularly suitable for controlling the high-pressure turbine exhaust temperature at startup and ensuring safe operation of the turbine in coordination with the boiler. Regarding.

[Background of the invention]

In the conventional turbine load control method for reheat steam turbine plants, an intermediate pressure startup method has been adopted, and
As disclosed in Publication No. 3-102401, at the time of plant start-up and during single-load operation within the plant, only the reheat turbine is vented, the high-pressure turbine is kept in a vacuum, and the venting and co-induction are performed using reheat (medium pressure) Do it from the turbine. As the load increases, the high-pressure turbine is also vented. In this intermediate-pressure start-up, the load is increased from the state where only the reheat turbine is taking load, and in the process of opening the control valve, the required steam is A predetermined opening degree to ensure a sufficient amount of steam (approximately 20 to 30 degrees based on the rated main steam pressure, which can secure a steam volume commensurate with the load equivalent to the reheat steam pressure, which is normally controlled by a low-pressure bypass valve) % opening). However, with this conventional control method, if the amount of steam generated by the boiler is insufficient compared to the amount of steam required by the steam turbine, the main steam pressure of the boiler will decrease.
Although it is necessary to generate steam by inputting fuel into the boiler, actual plant operation tests have shown that it is impossible to increase the amount of evaporation instantaneously, making it impossible to continue plant operation.

In particular, in the case of a cold start after a long shutdown, it is necessary to keep the rise in steam temperature low on the boiler side in order to reduce mismatch with the cold turbine. , the amount of steam generated by the boiler will inevitably decrease. This conflicts with the turbine side request for the amount of steam generated by the boiler due to the sudden opening of the control valve, and it becomes difficult to operate in coordination with the boiler.

[Purpose of the invention]

The object of the present invention is to provide a reheat steam turbine plant with:
The purpose is to provide a turbine load control method that controls the rise in high-pressure turbine exhaust temperature at startup, ensures safe operation of the turbine, and enables coordination with the boiler.Other purposes are to reduce turbine life consumption. Another object of the present invention is to provide a turbine load control method that allows even more fine control by taking into account the boiler allowable load. There is something to do.

[Summary of the invention]

The first aspect of the present invention is to provide a switching load band from the switching start load to the switching end load in the process of opening the high-pressure turbine control valve and increasing the load, and incorporating the ability to follow the boiler side evaporation amount during this period. It is characterized by power control based on the switching load change rate. With this configuration, it is possible to control the high-pressure turbine exhaust temperature at startup, ensure stable operation of the turbine side, and improve coordination with the boiler side. You can have it.

In addition, the second invention of the present invention is to provide a switching load band from a switching start load to a switching end load in the process of opening the regulating valve of the high pressure turbine and increasing the load, and during this period, the ability to follow the boiler side evaporation amount, It is characterized in that it is controlled by a switching load change rate that takes into account the turbine lifetime consumption, and with this configuration, the turbine load can be controlled more precisely.

Furthermore, the third aspect of the present invention is to provide a switching load band ranging from a switching start load to a switching end load in the process of opening the regulating valve of the high pressure turbine and increasing the load, and during this period, the ability to follow the boiler side evaporation amount, The feature is that the switching load change rate incorporates the turbine life consumption and the boiler load change allowable value, and is controlled by the switching load change rate, and with this configuration,
Turbine load can be more precisely controlled.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 conceptually shows an example of a steam system of a reheat steam turbine plant.

In this reheat steam turbine plant, during steady operation, steam generated in a boiler 10 passes through a control valve 11, flows through a high-pressure turbine 12, passes through a check valve 13, a low-temperature reheat pipe 14, and is guided to a reheater 15, where it is reheated again. heated. The steam that has passed through the reheater 15 passes through a high temperature reheat steam pipe 16, an intercept valve 17, an intermediate pressure turbine 18, a low pressure turbine 19, and then flows into a condenser 20. A generator 21 is connected to the shaft end of the low pressure turbine.

At startup, the boiler reheat system performs turbine bypass operation for cooling. An example of the turbine bypass operation will be described below.

Steam generated in the boiler 10 flows from the main steam pipe 22 to the reheater 15 via the high pressure bypass valve 23, and the steam leaving the reheater 15 is directly passed through the high temperature reheater 16 and the low pressure bypass valve 24. flows into the condenser 20. In this case, the control valve 11 and the intercept valve 17 are in a closed state, and the ventilator valve 25 is in an open state. The reheat system is controlled by a low pressure bypass valve 24 to maintain a constant pressure.

FIG. 2 shows the relationship between pressure and load in the reheat system controlled by the low pressure bypass valve.

In the example shown in FIG. 2, when the load is below 25%, the reheating pressure is controlled to be equivalent to 25% of the rated value. At this stage, if the boiler steam conditions, especially the reheat steam temperature, reaches a temperature that allows ventilation to the turbine (generally, the mismatch with the reheat steam indoor wall metal temperature is 1110C or more), the intercept valve 1
7 is gradually opened, and a portion of the high temperature reheated steam flowing into the low pressure bypass valve 24 is supplied to the medium and low turbines 18 and 19. This allows the turbine to speed up and carry several loads. Furthermore, in order to increase the load, it is necessary to flow steam to the high-pressure turbine 12 as well. Therefore, the load is increased by opening the control valve 11 and closing the high-pressure bypass valve 23.

FIG. 3 (4) @, 0 schematically shows the relationship among the load, valve opening degree, and high-pressure turbine exhaust temperature during the turbine load increase process.

Below, Figure 1 and Figure 3 (4), @
, 0 will be explained.

That is, at time to, the initial load L is applied only to the intermediate pressure turbine 18.
Take o. At this point, only the intercept valve 17 takes off the load, and the load is L! The load continues to be taken only by the intercept valve 17 until the end. When further increasing the load from load L1, the load is increased linearly up to load L3 at a constant load change rate P.

At this time, the control valve 11 starts to open at the time point of the load L2 at time t2. Along with this, the high-pressure turbine exhaust temperature increases, and as the load increases to L3, the high-pressure turbine exhaust temperature also decreases. This rise and fall of the high-pressure turbine exhaust temperature causes rotor thermal stress to occur in the high-pressure turbine rotor exhaust section. Ventilator valve 25 will close at time t2. Figure 4 shows a cross-sectional view of the high pressure turbine exhaust.

As shown in FIG. 4, the high-pressure turbine is composed of an external casing 30 and a rotor 31, and as the high-pressure turbine exhaust temperature increases, maximum thermal stress is applied especially to the disk root 8 portion 32 of the rotor 31. occurs. This thermal stress causes the rotor 31 to undergo low-cycle fatigue, and the life of the rotor 31 is consumed in proportion to the value of the thermal stress each time the rotor 31 is started.

The thermal stress generated at this time is proportional to the amount of temperature change and temperature change rate ΔT/Δt when the load increases, as shown in Figure 3 (end), but the switching time of Δt is usually an extremely short time of several minutes or less. Therefore, it is proportional to the temperature change amount ΔT. Further, the reheat stress is pre-pressure controlled by the low-pressure bypass valve 24 as described above, and is maintained at a constant pressure when the control valve 11 is opened. Therefore, assuming that the main steam conditions are constant, the temperature change amount ΔT is the load LI+ shown in Fig. 3 (4).
It is determined by L3 and load change rate P. Now, the loads L1 to L3 will be called a switching load band, the load L+ will be called a switching start load, and the load L3 will be called a switching end load.

The load change rate P will still be referred to as the switching load change rate P.

FIG. 5 shows an embodiment of the present invention, and shows an example of a control function for controlling the switching load band.

When the target load is input, the control device selects the switching load band. At the same time, the switching load change rate P of the switching load band is also set. This value is determined by taking into account followability of the amount of evaporation on the boiler side, but in this example, the hot mode (metal temperature of 40t : or more): 5%
/iN In other cases, an example is shown in which the value is uniformly 3%/m.

FIG. 6 shows another embodiment of the present invention, showing a method for more finely controlling the switching load band.
It is necessary to set the load to be slightly smaller than the maximum load that can be carried by the intermediate-pressure turbine and the low-pressure turbine, and to prevent the regulating valve 11 from opening before the turbine output enters the switching load zone. The load that can be carried by medium and low pressure turbines is proportional to the reheat steam pressure, and the higher the reheat steam temperature,
Also, the higher the degree of vacuum in the condenser, the larger it becomes.

Therefore, the switching start load L! will be calculated using the following formula: L+=c+xPrpxf(Trp)xg(V) −(1
) C1: Constant P! p: Reheat steam pressure f: Function with steam temperature as a parameter g: Function with condenser vacuum degree as a parameter The end load L3 allows a sufficient flow rate to flow so that the high-pressure turbine exhaust temperature does not rise. You need to choose a load. Further, the switching end load L3 is the sum of the high pressure turbine output, the intermediate pressure turbine output, and the low pressure turbine output. Therefore, the switching end load L3 is expressed by the following equation.

L3=C3XPip Xll (THp) +C4XP
rpX f' (TIp)x g' (V)...
(2) C*, C4: Constant PHp: Main steam pressure h: Function f/ with main steam temperature as a parameter, function g' with reheat steam temperature as a parameter: Condenser vacuum Functions f9g, h, f' used in equations (1) and (2) above, with degree as a parameter.

For example, if g′ is expressed as a linear equation for the parameter, the configuration of the control device will be easier; however, to improve accuracy, If the controllability of the reheat steam pressure is very good, the correction using the reheat steam pressure Pxp can be omitted.

The higher the switching load change rate P is, the better the effect of suppressing the high-pressure turbine exhaust temperature will be. The switching load change rate P is set high on the boiler side, and the switching load change rate P is set small on the cold side, where boiler side evaporation is less likely to occur and the number of startups and stops is small. The temperature of the metal after the first stage of the turbine is usually used as a hot or cold determination condition, but any signal that can determine the startup mode can also be used as an input.

FIG. 7 shows another embodiment of the present invention, in which the switching load change rate P is determined as a function in which the turbine life consumption setting value X is also considered. In other words, at each start-up, the operator or a pre-programmed value (computer command, etc.) selects a switching load change rate P that is lower as the allowable lifetime consumption is larger, and is set higher as the allowable lifetime consumption is smaller. Select the switching load change rate P.

FIG. 8 shows yet another embodiment of the present invention, in which the switching load change rate P is compared to the turbine side set value PT and the boiler allowable load change rate P.
A function has been added to constantly compare B and minimize the occurrence of trips due to insufficient evaporation on the boiler side.

〔Effect of the invention〕

According to the first aspect of the present invention explained above, in the process of opening the control valve of the high-pressure turbine and increasing the load, a switching load band is provided from the switching start load to the switching end load, and this period is used to reduce the boiler side evaporation amount. Since the control is based on the switching load change rate that incorporates tracking power, the high-pressure turbine exhaust temperature at startup can be controlled, stable operation of the turbine side can be ensured, and coordination with the boiler side can be maintained. This has the effect of enabling turbine load control.

Further, according to the second aspect of the present invention, in the process of opening the regulating valve of the high-pressure turbine and increasing the load, a switching load band is provided from the switching start load to the switching end load, and the boiler side evaporation follow-up ability is established during this period. Since the control is based on the switching load change rate that takes into account the rotor life consumption and the rotor life consumption, there is an effect that the turbine load can be controlled more finely by taking into consideration the turbine life consumption consumption.

Furthermore, according to the third aspect of the present invention, in the process of opening the regulating valve of the high-pressure turbine and increasing the load, a switching load band is provided from the switching start load to the switching end load, and the boiler side evaporation follow-up ability is provided during this period. , turbine lifetime consumption, and
Since the switching load change rate is controlled by taking into account the allowable boiler load change value, the turbine load can be controlled more finely by taking into account the allowable boiler load change value.

[Brief explanation of drawings]

Figure 1 is a conceptual diagram of the steam system of a reheat steam turbine plant, Figure 2 is a diagram showing the relationship between pressure and load in the reheat system controlled by the low-pressure bypass valve, Figure 3 (conversion), [ F])
, c') are diagrams showing the relationship between load, valve opening, and high-pressure turbine exhaust temperature during the turbine load increasing process, Figure 4 is a sectional view of the high-pressure turbine exhaust section, and Figure 5 shows an embodiment of the present invention. 6 is a diagram showing the control of the target load control setting value and the switching load change rate, FIG. 6 is a diagram showing the control of the switching load band and the switching load change rate in another embodiment of the present invention, and FIG. 7 is a diagram showing the control of the switching load change rate in another embodiment of the present invention. FIG. 8 is a diagram showing control of the switching load band and switching load change rate according to another aspect of the present invention. FIG. 8 is a diagram showing control of the switching load band and switching load change rate according to still another aspect of the present invention. 10...Boiler, 11...Adjustment valve, 12...High pressure turbine, 13...Check valve, 14...Low temperature reheat pipe,
15... Reheater, 16... High pressure reheat steam pipe, 17.
...Intercept valve, 18...Intermediate pressure turbine, 19.
...Low pressure turbine, 20... Condenser, 21... Generator, 22... Main steam generator, 23... High pressure bypass valve, 24... Low pressure bypass valve, 25... Ventilator Valve, 30... High pressure turbine external inE chamber, 31...
Rotor, 32...rotor disk root 8, Ll.
...Switching start load, L3...Switching end load, P...
Switching load change rate, X...Turbine life consumption setting value, P
g...Boiler allowable load change rate. Agent Patent Attorney Akimoto Masami Ratio 2 1,000 3 (B) Quasi 6 Days' 1

Claims (1)

[Claims] 1. A reheat steam turbine plant comprising a boiler with a reheater, a high-pressure bypass system, a low-pressure bypass system, and a ventilator system extending from the exhaust side of the high-pressure turbine to the condenser, In the process of opening the heating valve of the high-pressure turbine and increasing the load, a switching load band is created that spans from the switching start load to the switching end load, and this period is controlled by the switching load change rate that incorporates the ability to follow the boiler side evaporation amount. A turbine load control method for a reheat steam turbine plant, characterized in that: 2. In claim 1, the switching start load and switching end load are set as functions of main steam pressure and temperature, reheat steam pressure and temperature, and condenser vacuum degree. Turbine load control method for reheat steam turbine plant. 3.% Permissible A method for controlling a turbine load in a reheat steam turbine plant according to claim 1, wherein the switching load change rate is set as a function of a turbine metal temperature. 4. In a reheat steam turbine plant equipped with a boiler with a reheater, a high-pressure bypass system, a low-pressure bypass system, and a ventilator system extending from the exhaust side of the high-pressure turbine to the condenser, the control valve of the high-pressure turbine is In the process of opening and increasing the load, a switching load band is established from the switching start load to the switching end load, and during this period, the switching load change rate is determined by taking into account the ability to follow the boiler side evaporation amount and the turbine life consumption. A load control method for a reheat steam turbine plant, characterized in that the load is controlled by a reheat steam turbine plant. 5. In a reheat steam turbine plant equipped with a boiler with a reheater, a high-pressure bypass system, a low-pressure bypass system, and a ventilator system extending from the exhaust side of the high-pressure turbine to the condenser, the control valve of the high-pressure turbine is In the process of opening and increasing the load, a switching load band is established from the switching start load to the switching end load, and during this period, a switching load is established that takes into account boiler side evaporation follow-up ability, turbine life consumption, and boiler load change tolerance. A turbine load control method for a reheat steam turbine flint characterized by controlling by a rate of change.