JPS58197408A - Starting device for combined plant - Google Patents

Abstract

PURPOSE:To aim at making a starting of a combined power plant system in a short time and as well preventing the stress deviation of a steam turbine, by determining an initial load upon the initial load control of a gas turbine in accordance with the thermal condition of the steam turbine. CONSTITUTION:Exhaust gas from a gas turbine 1 which has driven a generator 15 is led into an exhaust gas boiler 2 in which the exhaust gas heats a supply water for generating steam, thereby heat recovery is conducted. The steam is led through a pipe 100 into a steam turbine 3 for rotating a generator 4. A metal temperature TM of the steam turbine 3 is read at the step B1, a steam temperature T1ST after a first stage necessary for setting the thermal stress of the steam turbine below a limiting value is calculated at the step B2, a main steam temperature TS is calculated in consideration with the steam temperature T1ST at the step B3, an exhaust gas temperature TG of the exhaust gas boiler 2 is obtained at the step B4, and the output LG of the gas turbine can be obtained at the step B5.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention combines a gas turbine and a steam turbine to
This invention relates to a device for determining a gas turbine load amount suitable for steam turbine starting steam conditions and optimally starting the steam turbine in a combined plan.

In a combined plant that combines a gas turbine and a steam turbine, heat is recovered from the exhaust gas of the gas turbine to obtain steam, which is used to drive the steam turbine. This combined plant, like other power plants, is required to start up at high speed, and this can be achieved by increasing the load on the gas turbine and increasing the amount of gas turbine exhaust gas. However, C means that the steam condition flowing into the steam turbine will be extremely high temperature.
This is not preferable from the viewpoint of preventing deviation from thermal stress limits of the steam turbine.

In view of the above, an object of the present invention is to provide a combined plant starting device that can obtain steam suitable for starting a steam turbine.

In the present invention, the initial load of 1 liter when controlling the initial load of the gas turbine is
The above objective is achieved by determining the temperature according to the thermal state of the t-steam turbine.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

Figure @1 shows the overall configuration of a multi-shaft system (a gas turbine and a steam turbine each drive a separate generator) as an example of a combined plant to which the present invention can be applied. The exhaust gas from the gas turbine 1 that drives the generator 15 is guided to the exhaust gas boiler 2, where it heats feed water to generate steam and recover heat. This steam is transferred to the piping 100, the turbine inlet valve 10
The water is guided to a steam turbine 3 via a steam turbine 2, and after passing through a generator 4, is cooled and condensed in a condenser 5 to become condensed water. The condensate is pushed up to the deaerator 7 by the condensate pump 6, and after deaeration, the water is pumped to the water supply pump 8.
The water is pressurized and sent to the drum 101 of the exhaust gas boiler.

This is the thermal cycle of a multi-shaft combined plant. Although there are many control devices such as a control device IQj, a closed loop control device, a sequence control device, and a turbine control device that control this plan), they are omitted because they are not directly related to the present invention. Control devices related to the present invention include a gas turbine control device lO that controls the amount of fuel in the gas turbine l, and an optimum starting device tt'. The optimum startup control device 11 measures the metal salt fTi* of the steam turbine 3 (this thermometer 12 normally measures the temperature of the inner wall after the first stage of the steam turbine 3), and determines the temperature of the metal salt fTi* of the steam turbine 3 to optimize the startup of the turbine. The gas turbine zero load is set in the gas turbine control device IO.

Before going into the details of the control device, an overview of the startup operation of this combined plant will be explained with reference to FIG. 2. First, the gas turbine l starts to start up at time t, and the gas turbine speed increases! fsGt increases to rated speed SGO. At time t after reaching the rated speed, the gas turbine generator 15 is connected to the power system, the load LG is increased to a predetermined initial load amount LGO, and is temporarily held at this initial load LGO. Feed water is heated in the exhaust gas boiler 2 by the exhaust gas applied to this initial load maintenance card, and the main steam pressure PM and the main steam temperature Ts rise. In the initial state, the turbine valve 102 is fully closed, the dump valve 16 is fully open, and the steam generated in the boiler 2 is dumped to the condenser 5. At time t, the main steam temperature 1
When fT- reaches [T*o] sufficient to vent to the steam turbine 3, the turbine artificial valve 102 is opened, the dump valve 16 is closed, and the steam turbine 3 is started. Speed of steam turbine 3 f8
8 reaches the rated speed tsso at time t4, the steam-one-bin generator number is connected to the power system and the load LS is increased.

The present invention controls the initial load amount of the gas turbine so as to obtain the optimum steam temperature for starting the steam turbine during this startup process, and FIG. 3 shows a flowchart of the processing contents of the optimum startup device 11. The initial load on the gas turbine is at the time t when the load control starts.

It is held constant from t to the steam turbine load control start time t, t. For this reason, the starting device 1t shown in FIG.
The process ll must be completed before time t, and the initial load must be set on the gas turbine controller IO.

First, in block Bl, the temperature of the metal 114 Wt T w of the steam turbine 3 is read at 1fli12 to know the cooling state of the steam turbine before starting the steam turbine. Next, in block B2, the first post-destruction steam ff1lf T 1m t required to make the turbine thermal force during ventilation of the steam turbine less than the limit basket is estimated and calculated.

TIs! One estimation method is described below. Usually, the casing inner wall temperature after the turbine tR is used as the input turbine metal temperature If T hs;
You can think of it as equal to the post-stage rotor metal. On the other hand, the thermal stress of the rotor is proportional to the difference ΔT between the rotor metal temperature and the @1 stage trailing air 111jTtst. Therefore, the temperature difference ΔT is determined in advance according to the limiting stress, and Tlmy is
If you want to find it as Txat = T + ΔT, then this TIat
This means that the stress does not deviate from the limit frL at the first post-cooling steam temperature of . In block B3, this steam temperature T! Steam turbine control valve from s〒! Reverse calculation 17 of the throttling effect in step 2. Calculate the main steam temperature at the turbine inlet and the temperature T1 using all the known characteristics shown in FIG. 4(a). Is this characteristic the main steam pressure PM? It is determined in advance as a parameter, and T1 is determined after determining the main steam pressure Pw during ventilation. According to the predetermined ftPw, the pressure is controlled to match the PM during actual ventilation of the steam turbine. Once the optimum main steam temperature T- for turbine ventilation is determined, in block B4, the exhaust gas temperature If Ta of the exhaust gas boiler 2 necessary to obtain this filfT- is determined using the heat transfer coefficient K in the exhaust gas boiler. Once this gas temperature [To has been determined, block B5 determines the gas turbine output Lo required to reach To from the gas turbine exhaust gas temperature characteristic curve shown in FIG. 4(b). Here, the calculated skin load amount Lo is set as the gas turbine initial load amount LGO to the gas turbine control device 11 after the gas turbine is installed.

In a combined plant, the exhaust gas flow rate of the gas turbine depends on the gas turbine rotation speed, and after the gas turbine is installed, it is kept at a nearly constant amount, and because the amount of exhaust gas is large, the heat transfer coefficient K in the exhaust gas boiler becomes large. Gas temperature [T
The time constant from o to main steam temperature [Ts is short, and it is sufficiently practical even with the gas turbine load determined from the static characteristic curve as described above.

The above calculation process is usually performed by a computer, and this optimal startup program may be incorporated into a dedicated microcomputer, or may be part of an overall large-scale automated system that includes a gas turbine and a steam turbine.

The second embodiment of the present invention is intended to achieve almost the same amount of effect and cost by using a simple conventional control device without using a high-class control device like the embodiment of @l. It is shown in FIG.

Calculate the initial load amount using the first method on a desk, and determine the optimal initial load t for the barrel temperature after immersion in the first stage # T M
Lo is created in advance as a function, and the initial load amount La is determined by the function generator z7. The larger of the initial load amount Lo output from the function generator 27 and the set value Lm of the manual load setter 32 is selected by the tA selector 28 and passed through the rate of change controller 291 to be set as the target load of the gas turbine. The comparator 30 compares this ripple with the actual load 21, and the control circuit 31 is passed through to control the gas turbine fuel valve 9.

This circuit calculates the initial load amount and is disconnected by the switch 34 to avoid outputting an erroneous signal. In this method, the initial load amount is fixed and the original value is somewhat rough, but the device is pure and suitable for practical use.

As a third embodiment, an example of a control method that enables short-time startup while keeping thermal stress within a limit value is shown in Figure 6. In this method, the calculation of the target value of the post-first-stage beauty temperature in the embodiment shown in FIG. 3 is modified.

This means that if the shortest time start mode is selected, the temperature difference α that is allowed due to thermal stress will be added to the result of the wIJ 1 stage steaming degree T * s t calculated in block B2 of Fig. 3.
By adding the target @1st stage post-death temperature [T 1m t, the initial load of the gas turbine is increased as much as possible in terms of thermal stress, the gas turbine load rise time is shortened, and the start-up time is minimized. It is.

The temperature addition α is related to the inner m temperature, and the actual
It is calculated by the right thermal stress calculation and is a friendly cough. This embodiment has a feature that minimizes startup time. In addition, the selection of whether or not the block BI
I#i represents the function of modifying the first stage steam temperature.

In short, the present invention described above is a method in which the initial load amount of the gas turbine is determined in consideration of the thermal deafness of the steam turbine before performing gas turbine load operation, and as a result, the steam turbine is cooled. By reducing the initial load on the gas turbine, it is possible to start up the entire combined plant system in the shortest possible time and prevent stress deviation in the steam turbine.

In addition to the multi-shaft combined plant shown in Fig. 1 of the present invention, a double-shaft type plant in which a gas turbine 1, a steam turbine 3, and a generator are arranged on the same axis is also adopted as in 4. It is possible.

[Brief explanation of drawings]

@ Figure 1 is an overall configuration diagram of the combined plant and control device, Figure 2 is the startup curve of the combined plant, Figure 3 is a process 70-diagram in the device of the present invention for determining the optimum main steam temperature, and Figure 4 is The characteristic curves used in the calculation of the present invention, FIG. 5 shows a simple embodiment, and FIG. 6 shows a processing flow diagram for minimizing the startup time. ! ...Gas turbine, 2...Exhaust gas boiler, 3...
- Steam turbine, 5... Condenser, lO... Gas turbine control device, 11... Optimum starting device, 12... Turbine metal thermometer, 21... Gas turbine load, 2
2...Main steam pressure, 23...Main steam temperature, 27...
- Initial load calculation function generator. 1:111 Figure 1 Y2 Figure 5

Claims (1)

[Claims] ! , consists of a gas turbine, a boiler that generates steam using its exhaust gas, and a steam turbine that is driven by the steam from the boiler. After igniting the gas turbine and maintaining its load at the initial load, the steam turbine In a ventilated combined plant, a first device that controls the initial load amount of the gas turbine according to the thermal state of the steam turbine before controlling the initial load amount of the gas turbine, and a first device that controls the initial load amount of the gas turbine according to the output of the device. A combined plant starting device characterized by comprising a second device for.