JPS58192908A - Control device of combined cycle turbine plant - Google Patents

Abstract

PURPOSE:To reduce thermal stresses in a waste heat recovery boiler and steam turbine by providing a limit value output circuit that outputs a limit value with receiving input from a drum temperature limiting circuit and steam turbine temperature limiting circuit. CONSTITUTION:A combined cycle turbine plant consists of a gas turbine 5 and steam turbine 11. A plant control device 17 is provided with the drum temperature limiting circuit 30 for waste heat recovery boiler 7, a steam turbine temperature limiting circuit 35, and a limiter 33 that operates by the output from a limit value output circuit 32. The fuel signal from a low value preference circuit 22 is converted to opening signal by an opening control circuit 21 to adjust the opening of a fuel control valve 3. With this arrangement thermal stresses in the waste heat recovery boiler 7 and the steam turbine 11 can be reduced even in starting and sudden change in loading.

Description

DETAILED DESCRIPTION OF THE INVENTION [Contact Field of the Invention] The present invention provides a system that combines a gas turbine and a steam turbine.
This invention relates to a control device for a combined 8-cycle turbine plant, and in particular to a control device that reduces thermal stress of the steam turbine and exhaust heat recovery boiler 2 by 14 during startup or sudden load changes.

[Technical background of the invention]

Combined cycle turbine plants, which consist of a gas turbine and a steam turbine driven by the generated steam generated using its exhaust gas as a heat source, have high thermal efficiency.
It has received particular attention in recent years.

Cono combined cycle turbine plants include a type that combines several gas turbines, an exhaust heat recovery boiler and seven steam turbines, and a type that consists of a gas turbine, an exhaust heat recovery boiler, and six steam turbines. be. Among these, those in which a gas turbine and a steam turbine are connected to a single shaft have been increasingly adopted in recent years because they require a relatively small installation space. Figure 1 shows a combined cycle turbine plant in which a gas turbine and a steam turbine are connected to each other by a six-wheel shaft. is supplied to the main fuel control valve 3.
It is heated by the combustion of the main fuel supplied through the main fuel supply pipe, which has a main fuel supply pipe, and turns into high-temperature gas to the gas turbine! supplied to

The gas turbine above! The high-temperature gas supplied to the gas turbine j performs work in the gas turbine j to drive the generator 4 connected to the same shaft, and the high-temperature exhaust gas discharged from the gas turbine j is sent to the waste heat recovery boiler e. It is supplied as a heat source. The exhaust gas exchanges heat with steam and feed water while passing through the superheater I, evaporator, and economizer IO, lowers its temperature, and is released into the atmosphere. On the other hand, the feed water that has completed its work in the steam turbine ii and has been condensed in the condenser/co passes through the feed water pump 13, is heated by the economizer/θ, and is introduced into the drum/l. Thereafter, the feed water is evaporated while passing through the circulation pump/S and the evaporator, and the generated steam is separated from brackish water in the drum/4' and then superheated in the superheater r.

This superheated steam passes through a steam control valve 16 and then passes through a steam control valve 16.
The steam turbine performs expansion work and drives a generator connected to the same shaft.

The control of such a combined cycle turbine plant is such that the amount of fuel supplied to the combustor from the main fuel supply 1<<, which has the main fuel control valve 3, is controlled by controlling the amount of fuel supplied to the combustor from the main fuel 1b1]
This is done by adjusting the control valve 3. That is, if the control device U adjusts the opening degree of the control valve 3 and the amount of fuel in accordance with the required load, the load on the gas turbine j can be controlled, and furthermore, the amount of fuel discharged from the gas turbine j can be controlled. As the temperature and flow rate of the exhaust gas are adjusted, the amount of heat input to the exhaust heat recovery boiler changes, and as a result, the steam turbine/
By changing the steam supply profile to l, the load on the steam turbine // can be controlled. The steam control valve 6 is kept fully open during normal operation, so all the steam generated in the heat recovery boiler is supplied to the steam turbine, increasing the thermal efficiency of the combined cycle turbine plant. There is. Like this, a gas turbine! A control device U that controls
The system also controls the start/stop of the entire plant and load adjustment.

However, the damping device U is used from the ignition to the gas turbine! Start control circuit/l that controls until the rated rotation speed is reached, and the gas turbine! A speed control circuit/9 that outputs a fuel signal to always maintain the rotation speed of the gas turbine at the rated rotation speed and follow the load request according to the speed regulation rate, and a gas turbine! and a combustion temperature control circuit which calculates a combustion temperature from the temperature of exhaust gas discharged from the exhaust gas and outputs a fuel signal such that the combustion temperature falls within an allowable value, and further includes the startup control circuit /I.

It has a speed control circuit 19 and a low value priority circuit which outputs the minimum value of the fuel signals output from the combustion temperature control circuit to the opening degree control circuit 21. Therefore, fuel No. 16 that does not exceed the combustion temperature limit and that follows the required values of rotational speed and load is always input to the opening control circuit. Furthermore, this fuel signal is once converted into a command signal, and the opening degree of the main fuel control valve J is increased by v4wJ.

[Problems with background technology]

However, as mentioned above, in the conventional technology, gas turbines! Although the combustion temperature of the steam turbine is limited to below the allowable value, no consideration is given to the thermal stress of the drum of the exhaust heat recovery boiler, the thick wall of the circulation pump, and the steam turbine. Therefore, there is a problem in that thermal stress is applied to the exhaust heat recovery boiler and the steam turbine during excitation or sudden changes in load, which shortens the life of the equipment.

[Purpose of the invention]

The present invention has been made in view of these points, and provides a control device for a combined cycle turbine plant that reduces thermal stress in an exhaust heat recovery boiler and a steam turbine even during startup or sudden changes in load. The purpose is to

[Summary of the invention]

The present invention provides a startup control circuit for controlling startup, a speed control circuit for controlling speed and load, a combustion temperature control circuit for controlling combustion temperature of a gas turbine, and a minimum value of the output of each of the above circuits in a combined cycle turbine plant. In a plant control device that has a low value priority circuit that outputs a low value, there is a drum temperature limiting circuit that inputs a signal from a drum temperature detector installed in the drum of the exhaust heat recovery boiler, and a steam turbine temperature detection circuit installed in the steam turbine. A steam turbine temperature limiting circuit that inputs signals from the steam turbine, a limit value output circuit that receives input from the above-mentioned λ temperature limit circuits and outputs a limit value, and operates based on the output from the limit value output circuit. It is characterized by being equipped with a restrictor.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. Note that the same parts as in FIG. 1 are given the same reference numerals, and their explanations will be omitted.

In FIG. 1, reference numeral 30 denotes a drum temperature limiting circuit, which includes drum temperature detectors J/, which are provided on the upper and lower surfaces of the drum 1, and detect the metal temperature, respectively. The detection signal from 31' is manually generated. In addition, the upper 6th dome temperature limiting circuit 3θ is,
Calculate the input temperature difference between the upper and lower surfaces of the drum, and calculate this temperature by 1J.
It outputs 4 signals to determine whether the E difference is less than the allowable value determined in advance from the drum/da size, #quality, etc., and if it is above the allowable value, outputs a signal to the limit value output circuit 3. ,
The limit value output circuit 32 thereby operates the mountain 11 limiter 33 and applies a limit so as to suppress the rise of fuel No. 1g from the low value priority circuit n. In addition, the drum temperature detector 3
/, 3/' are installed on the upper and lower surfaces of the drum /4' as in this embodiment, or when installed on the inner and outer surfaces of the drum/hiro to measure the temperature difference between the inner and outer surfaces. , may be installed on the upper and lower surfaces and the inner and outer surfaces, and both the upper and lower thI temperature difference and the inner and outer surface temperature difference may be measured. On the other hand, a detection signal from a steam turbine temperature detector installed on the inner and outer surfaces of the first stage shell of the steam turbine 1/1 is inputted manually to the steam turbine temperature limiting circuit 35, The temperature limit circuit 3j calculates the temperature difference between the inner and outer surfaces, calculates the life consumption rate of the steam turbine l/ based on this value, and determines whether or not it is within a preset life consumption rate. After that, if the temperature difference between the inside and outside surfaces is too large, a signal is output to the three limit value output circuits, and the three limit value output circuits send a limit value that changes depending on the size of this temperature difference to the limiter 33. input and limit the fuel signal from the low value priority circuit. The limit value output circuit 3 manually calculates the temperature difference (No. 1) from the drum temperature limit circuit 3θ and the steam turbine temperature limit circuit 3S, and the deviation between the temperature difference and the allowable value, and if this deviation is large, The limit value is kept low, and when the deviation is small, the limit value is falsified to a large value, and the smaller limit value of the drum temperature limit and the steam turbine temperature limit is output to the limiter 33.Then, the limit value is output from the low value priority circuit n. The fuel signal is limited so that the temperature difference between the upper and lower surfaces or the inner and outer surfaces of the drum 1 is within a tolerance value, or the temperature difference between the inner and outer surfaces of the steam turbine 1/ is within a tolerance value.

This limited fuel signal is converted into an opening signal by the opening control circuit 2/, and the opening/closing of the fuel control valve 3 is adjusted.

〔Effect of the invention〕

As explained above, according to the present invention, the 51 drum temperature limiting circuit inputs the detection number 1d from the drum temperature detector installed in the drum, and the detection signal from the steam turbine temperature detector installed in the steam turbine. It is operated by the output from the limit value output circuit, which receives the input signals from the two temperature W7LilJ limit circuits and outputs the limit value. By installing the restrictor, the gas turbine is operated to keep the temperature of the exhaust heat recovery boiler and steam turbine within the allowable value even during start-up or sudden load changes, so the exhaust heat recovery boiler It is possible to completely reduce the thermal stress of steam turbines and steam turbines, which has the effect of extending the life of the equipment.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a control system of a conventional combined cycle turbine plant, and FIG. 2 is a system diagram of a system of a control system of a turbine plant according to an embodiment of the present invention. ! ...Gas turbine, E...Exhaust heat recovery boiler, /
/...Steam turbine, 21...Opening control circuit, n
...Low value priority circuit, 30...Drum temperature limit circuit, 3/. 3/'...Drum temperature detector, 32 river limit value output circuit, 33...Restrictor, 31t, 34'...Steam turbine temperature detector, 3j...Steam turbine temperature limit circuit. Applicant's agent Kiyoshi Muta

Claims (1)

[Claims] In a combined cycle turbine plant, a startup control circuit that controls startup, a speed control circuit that controls speed and load, a gas turbine combustion temperature control circuit, and a low value priority circuit that outputs the minimum value of the output of each of the above circuits. In a plant control device with
A drum temperature limiting circuit, a steam turbine temperature limiting circuit that inputs signals from a steam turbine temperature detector installed in the steam turbine, and a limiter that receives inputs from the upper and lower temperature limiting circuits and outputs a limit value. 1. A control device for a combined cycle plant, comprising a value output circuit and a limiter operated by the output from the limit value output circuit.