JPH0486308A - Steam-cooling gas turbine combined plant - Google Patents

Abstract

PURPOSE:To secure a minimum required cooling steam flow rate by selecting the higher value signal out of a control signal according to a deviation between a cooling steam requiring value and a cooling steam flow rate signal, and a control signal according to a deviation between a steam pressure setting signal and a cooling steam pressure signal, and thereby controlling a cooling steam adjusting means. CONSTITUTION:In a control device 20, in which a part of steam is introduced into a gas turbine cooler 14 through a cooling steam adjusting valve 13 for controlling an opening of the cooling steam adjusting valve 13 at the time of cooling inside parts of moving and static blades of high temperature parts of a gas turbine, a control signal 26 for securing a steam pressure is obtained through a PI controller 25 from deviation between a steam pressure setting signal 23 calculated through addition 22 of an output signal from a compressor output pressure detector 15 to a bias signal from a bias setter 21, and a cooling steam pressure signal from a detector 17. A control signal 32 for attaining a required minimum cooling steam flow rate through a PI controller 31 is obtained from a deviation between a cooling steam requiring value 29 output from a function generator 28 and a cooling steam flow rate signal from a detector 16. The higher value signal out of the control signals 26, 32 is selected by a higher value selector 27 to be output.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a steam-cooled gas turbine combined plant that uses steam as a cooling medium for moving and stationary blades of a gas turbine, and particularly relates to a steam-cooled gas turbine combined plant that uses steam as a cooling medium for moving and stationary blades of a gas turbine. The present invention relates to a cooling steam control device when using steam as cooling steam.

(Prior art) Generally, improvement in thermal efficiency of combined cycle power generation is achieved by increasing the temperature of the gas turbine.
°C.

On the other hand, the rotor and stationary blades in the turbine passage have conventionally been cooled by flowing compressor discharge air or bleed air from an intermediate stage of the compressor into the turbine rotor and stationary blades, thereby maintaining their strength in high-temperature gas.

Incidentally, it is expected that the turbine inlet temperature will continue to rise in the future, and as a result, cooling of the turbine rotor and stationary blades must be further strengthened, which will require a large amount of cooling air. However, since the cooling air joins the mainstream gas of the turbine after cooling the blades, there is a problem in that the temperature of the mainstream gas in an intermediate stage of the turbine is lowered, resulting in a decrease in plant efficiency.

In other words, when increasing the temperature of the turbine, both factors coexist: efficiency increases due to an increase in the turbine inlet temperature, and efficiency decreases due to a decrease in the mainstream gas temperature due to cooling air, so it is necessary to gradually increase the turbine inlet temperature. If you raise it to 1
The influence of the latter becomes large near 300°C, and in the case of air cooling methods, at high temperatures of 1300°C or higher, the thermal efficiency conversely decreases. Figure 7 shows an example. At turbine inlet temperatures of 1300°C and 1400°C, the combined plant thermal efficiency is 47°C, respectively.
．． 2%, 47.0%.

As a countermeasure to this problem, a method has been proposed in which steam is used as a cooling medium to flow inside the rotor and stationary blades of the turbine.The steam source for this method is an exhaust heat recovery boiler (which generates steam by recovering the exhaust heat of the gas turbine). It is preferable to use steam produced by a steam generator (hereinafter referred to as HR3G) from the viewpoint of efficiency, reliability, and system configuration.

In addition, since the steam after cooling the high-temperature components is itself heated and has high enthalpy, it can be collected as power by flowing into the steam turbine of the compound cycle.
This is also preferable from the viewpoint of improving overall thermal efficiency.

(Problem to be Solved by the Invention) By the way, when considering that in a steam-cooled gas turbine combined plant, the steam generated by HR3G is used for cooling the gas turbine, and the steam after cooling is recovered to the steam turbine. , it is required that the flow rate of the cooling steam is appropriate and the pressure of the cooling steam is appropriate.

In other words, the cooling steam flow rate is determined by the pressure difference between the steam pressure at the take-out section of HR8G and the pressure at the steam recovery section (inflow section to the steam turbine). Therefore, the cooling steam flow rate is automatically determined. Therefore, under any gas turbine load, the HR
Since the steam extraction site of the 8G and the steam recovery site of the steam turbine are determined based on the design pressure balance, the system design results in a cooling steam flow rate that is higher than the design flow rate throughout the load zone.

In this method, is it possible to protect the high-temperature components of the gas turbine? Unnecessarily cooling the components causes non-uniform thermal stress on the high-temperature components due to the load band, resulting in a reduction in overall efficiency.

From the standpoint of overall thermal efficiency, it is preferable to flow only the minimum amount of cooling steam necessary and to let the surplus steam do work in the steam turbine.

In addition, cooling steam flows inside high-temperature components such as the moving and stationary blades of a gas turbine and cools the high-temperature components from the inside, so in principle it does not come into contact with the gas of the gas turbine. It cannot be said that there is no leakage from small gaps such as parts or sliding parts between stationary parts and rotating parts. and,
If the steam pressure is lower than the gas pressure and the gas mixes into the steam flow path, impure gas components will dissolve or mix in the recovered steam, which will pass through the steam turbine and become f(
Because it circulates through the R8G's steam system, internal corrosion becomes a problem. For this reason, it is necessary to always maintain the pressure on the steam side higher than the gas pressure so that even if a leak occurs, the steam will leak to the gas side.

The present invention has been developed in view of the current situation, and is capable of supplying the minimum necessary cooling steam flow rate without excess or deficiency at each operating load, and is capable of always maintaining the pressure on the steam side higher than the gas pressure. The purpose is to provide a steam-cooled gas turbine combined plant that can

[Structure of the invention]

(Means for Solving the Problem) As a means for achieving the above object, the present invention cools a gas turbine high temperature member with steam supplied from an exhaust heat recovery wheeler through a cooling steam regulating means, and In a steam-cooled gas turbine combined plant that recovers steam to a steam turbine, there is a heat load detection means for detecting a parameter representing a heat load on high-temperature components of the gas turbine, and a cooling steam request value based on a signal from the heat load detection means. a first control means for outputting a control signal according to a deviation between the cooling steam request value and a cooling steam flow rate signal from the cooling steam flow rate detection means; and a first control means for detecting an operating parameter representing gas path pressure. a pressure detector; an adder that adds a bias value to the signal from the pressure detector and outputs it as a steam pressure setting signal; and a high value selection means for controlling the cooling steam adjusting means using a signal having a higher value among the control signals from both the control means. .

(Function) In the steam-cooled gas turbine combined plant according to the present invention, a parameter representing the heat load on the gas turbine high-temperature components is detected by the heat load detector, and based on this signal, the calculation means uses the minimum amount necessary for cooling. The maximum cooling steam requirement is calculated. A control signal corresponding to the deviation between this cooling steam request value and the actual cooling steam flow rate is output from the first control means. Therefore, by controlling the cooling steam adjusting means using this control signal, the minimum necessary cooling steam flow rate can be obtained according to the heat load of the gas turbine.

On the other hand, the pressure detector detects an operating parameter representing the gas path pressure, and the addition means adds a bias value to this signal and outputs it as a steam pressure setting signal. A control signal corresponding to the deviation between this steam pressure setting signal and the actual cooling steam pressure is output from the second control means.

Therefore, by controlling the cooling steam adjusting means using this control signal, it is possible to always maintain the pressure of the cooling steam higher than the gas pressure by the bias value.

By the way, if the cooling steam regulating means is controlled only by the control signal from the first control means, although it is optimal for cooling, there is a risk that the pressure will be insufficient; When controlling the cooling steam regulating means, the pressure may be adequate but the flow rate may be insufficient.

Therefore, in the present invention, such a problem is solved by selecting the higher value signal of both control signals by the high value selection means and controlling the cooling steam adjustment means using this signal.

(Example) Hereinafter, a first example of the present invention will be described with reference to FIGS. 1 to 4.

Fig. 2 shows an example of a steam-cooled gas turbine combined plant according to the present invention. The air thus generated and the fuel whose flow rate is controlled by the fuel control valve 4 are mixed and burned in the combustor 3 to drive the turbine 2 and generate electricity. As shown in Figure 2, the exhaust gas from the gas turbine is sent to HR8G5, where it exchanges heat with steam or water, and then is discharged.
The high temperature steam generated by R8G5 flows into the steam turbine 6 to generate electricity.

As shown in FIG.
The gas is sent to G 5 , where it exchanges heat with the gas turbine exhaust gas in the economizer 9 to raise its temperature, and then flows into the steam drum 10 .

As shown in FIG. 2, this steam drum 10 is provided with an evaporator 11, which receives heat from the exhaust gas of the gas turbine to raise the temperature of the drum water and evaporate it. The generated saturated steam is further heated by the high temperature exhaust gas of the gas turbine in the heater 1-2, and is sent to the steam turbine 6 as superheated steam.

As shown in FIG. 2, a part of the steam from the heater 12 side is supplied to the gas turbine cooler 1 via the cooling steam control valve 1-3.
4 to cool the inside of the dynamic and stationary blades in the high temperature section of the gas turbine, and the cooling steam heated by this cooling is recovered to the low pressure stage of the steam turbine 6.

As shown in FIG. 2, the cooling steam control valve 13 receives output signals from the compressor output L1 pressure detector 15, the cooling steam flow rate detector 16, and the cooling steam pressure detector J7 as feedback elements. control device 2
0, the opening degree is controlled.

As shown in FIG. 1, the control device 20 includes an adder 22 that adds the output signal from the compressor outlet pressure detector 15 and the bias signal from the bias setting device 21.
The steam pressure setting signal 23 output from the adder 22 is input to the subtracter 24 together with the actual cooling steam pressure signal from the cooling steam pressure detector 17,
The deviation is calculated. After this deviation is processed by the P controller 25, it is sent to the high value selector 2, which will be described later, as a control signal 26 for ensuring steam pressure.
7 is input.

The pressure signal from the compressor outlet pressure detector 15 is also input to a function generator 28 as a parameter that accurately represents the operating load of the gas turbine, as shown in FIG. The cooling steam demand value 29 output from the function generator 28 is input to the subtractor 3o together with the actual cooling steam flow rate signal from the cooling steam flow rate detector 16.
The deviation is calculated.

After this deviation is processed by the PI controller 31, a control signal 3 is sent to obtain the minimum necessary cooling steam flow rate.
2 and is input to the high price selector 27.

As shown in FIG. 1, this high value selector 27 compares both input control signals 26 and 32 and always selects the signal with the higher value among them, and selects the selected signal. is applied to the cooling steam control valve 13 as a valve opening degree control signal 33.

As a result, the flow rate of cooling steam to the high-temperature components of the gas turbine is controlled, and even when the flow rate of cooling steam may be small, the steam pressure is controlled so as not to drop below the gas pressure element bias signal. ing.

Next, the operation of this embodiment will be explained.

The pressure signal from the compressor outlet pressure detector 15 is added to the bias signal from the bias setter 21 in an adder 22, and the steam pressure setting signal 23 from the adder 22 and the cooling steam pressure from the cooling steam pressure detector 17 are added. The deviation of the signal is determined by a subtracter 24. And this deviation is
Via the PI controller 23, it is input to the high value selector 27 as a control signal 26 for ensuring steam pressure.

On the other hand, the cooling steam flow rate request value is obtained by inputting the compressor output [-1 pressure signal, which accurately represents the operating load of the gas turbine, to the function generator 28. A subtracter 30 calculates the deviation between the value 29 and the cooling steam flow rate signal from the cooling steam flow rate detector 1-6, and this deviation is converted into a control signal for controlling the cooling steam flow rate via the PI controller 31. 32
It is input to the high price selector 27 as a high price selector 27.

The high value selector 27 compares both input control signals 26 and 32, always selects the signal with the higher value, and supplies it to the cooling steam control valve 13 as a valve opening degree control signal 33. The opening of the cooling steam control valve 13 is controlled by the valve opening control signal 33, and the flow rate of cooling steam to the high temperature components of the gas turbine is controlled.

FIG. 3 shows an example of a curve for the function generator 28, which curve is determined from the combustion gas temperature increase and the amount of steam required to cool the hot gas turbine components.

Figure 4 shows the relationship between the combustion gas temperature and the amount of steam required for cooling with respect to the gas turbine load. In the figure, symbol A is the combustion gas temperature, and symbol B is the average of the high temperature section of the gas turbine without cooling. The metal temperature, symbol C, is the limit value of the blade metal temperature, symbol is the average metal temperature of the high temperature part of the gas turbine when cooled, symbol E is the required exchange heat, and symbol F is the required steam amount for cooling.

As is clear from Figure 4, the blade metal temperature is at the limit value C.
Cooling steam is required from point X beyond the point X, and the amount increases as the gas turbine load increases. Due to the increase in cooling steam, the average metal temperature B of the gas turbine high temperature section in the case of no cooling is limited to a limit value C, as shown by the symbol, by starting cooling at point X.

Since the compressor outlet pressure is approximately equivalent to the gas turbine load, the curve in FIG. 3 determines the required cooling steam amount F in FIG. 4 with the horizontal axis as the compressor outlet pressure.

As mentioned above, under the X intention in Fig. 4, the blade metal temperature is below the allowable value, so steam cooling is not necessary, but if the cooling steam control valve 13 is fully closed, the gas turbine The cooling steam pressure in the cooler 14 decreases and becomes lower than the gas pressure. Therefore, in this embodiment, the high value selector 27 prevents the cooling steam pressure from becoming lower than the gas pressure plus the bias value.

As a result, the flow rate of cooling steam can be supplied in just the right amount, and IF can be prevented from reducing efficiency due to surplus supply and damage to the gas turbine blades due to insufficient cooling. Further, it is also possible to reliably prevent gas from entering the steam line.

5 and 6 show a second embodiment of the present invention, in which a control device uses an exhaust gas temperature signal from an exhaust gas temperature detector 41 as a feedback element instead of the control device 20 in the first embodiment. 40 is used.

That is, this control device 40, as shown in FIG.
The calculator 42 calculates the gas turbine inlet temperature using the exhaust gas temperature signal from the exhaust gas temperature detector 41 and the pressure ratio signal from the compressor outlet pressure detector 15. Convert temperature (
For example, the estimated value of the blade metal temperature is obtained by converting the temperature using a coefficient.

As shown in FIG. 5, the estimated value obtained by the calculator 42 is calculated by a subtracter 44, and the deviation from the control limit target temperature of the blade metal from the setting device 43 is obtained by the subtractor 44. 45 and multiplier 46 with the output signal from the PI controller 31 to form one control signal 32, which is then input to the high value selector 27.

An example of a calculation formula in the arithmetic unit 42 is shown below.

(Output of the calculator 42) - (Coefficient K1) x (Exhaust gas temperature) x (Compressor outlet pressure) x (2 for the coefficient) ...... (1) For other points, It has the same configuration as the embodiment, and the operation is also the same.

Even with this configuration, the same effects as in the first embodiment described in Aif can be expected.

In both of the above embodiments, the case where the control valve 13 is used as the cooling steam control means has been described, but other control means such as an electric valve, a piston valve, a variable orifice, etc. may be used. Further, the required amount of cooler air is not determined by the compressor outlet pressure, but any parameter representing the operating load of the gas turbine, such as fuel flow rate or gas turbine load, may be used.

Furthermore, in both of the above embodiments, as a means for detecting the steam flow rate,
Although we have described the case where the detector 16 that directly detects the steam flow rate is used, the actual steam flow rate is estimated and calculated from the steam pressure and temperature before and after the cooling section and the resistance coefficient of the cooling steam flow path section, and this signal is used as the feedback signal. It may be done as follows.

In addition, the compressor output [1 pressure is not used as a waste pressure signal,
Gas pass pressure may also be used.

In addition, in both embodiments described in ■I, regarding the setting of the steam flow rate,
The steam flow rate may be controlled to match the steam flow rate, or as shown in FIG. 4, since the required exchange heat amount is given by the gas turbine load, the steam flow rate may be controlled using the required exchange heat amount as a set value. The amount of feedback in this case must be the amount of heat exchanged, so the actual amount of heat exchanged is
It is calculated from the steam pressure at the inlet and outlet I of the cooler using the gontal py and the steam flow rate.

In both of the above embodiments, the case where the cooling steam control valve is calculated is explained, or the directly measured blade metal temperature of the high temperature part or the temperature in the vicinity where this temperature can be estimated is
The steam flow rate may be controlled so as to reach a set temperature (control limit target temperature of the blade metal).

〔Effect of the invention〕

As described above, according to the present invention, the cooling steam flow rate of the steam-cooled gas turbine can be controlled optimally and reliably, and efficiency and reliability can be improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a control device for a steam-cooled gas turbine combined plant according to a first embodiment of the present invention;
Figure 2 is a diagram of the overall plant configuration, Figure 3 is a graph showing an example of the curve of the function generator, and Figure 4 is the combustion gas temperature, cooling steam requirement, heat exchange amount, and average high-temperature section for the gas turbine load. A graph showing the transition of metal temperature, Fig. 5 is a diagram corresponding to Fig. 1 showing the second embodiment of the present invention, Fig. 6 is a similar diagram corresponding to Fig. 2, and Fig. 7 is a graph showing the turbine inlet temperature and combined cycle thermal efficiency. It is a graph showing the relationship between 1...Compressor, 2...Turbine, 5...H
R8G, 6... Steam turbine, 13... Cooling steam control valve, 14... Gas turbine cooler, 15... Compressor outlet pressure detector, 16... Cooling steam flow rate detector, 1-7 ...Cooling steam pressure detector, 20.40...
- Control device, 21... Bias setting device, 22. 24
．． 30. 44... Subtractor, 23... Steam pressure setting signal, 25. 31°45...PI controller,
26.32... Control signal, 27... High value selector, 2
8...Function generator, 29...Cooling steam request value, 33
...Valve opening control signal, 41...Exhaust gas temperature detector,
42... Arithmetic unit, 43... Metal control limit target temperature setter, 46... Multiplier.

Claims (1)

[Claims] In a steam-cooled gas turbine combined plant in which the gas turbine high-temperature components are cooled by steam supplied from an exhaust heat recovery boiler via a cooling steam regulating means, and the cooled steam is recovered to the steam turbine, the gas turbine high-temperature components are cooled. heat load detection means for detecting a parameter representing the heat load of the heat load; calculation means for calculating a cooling steam request value based on a signal from the heat load detection means; a first control means that outputs a control signal according to the deviation from the steam flow rate signal;
a pressure detector for detecting an operating parameter representing the gas pass pressure; an addition means for adding a bias value to the signal from the pressure detector and outputting it as a steam pressure setting signal; A second control means for outputting a control signal according to a deviation from a cooling steam pressure signal, and a high value selection means for controlling the cooling steam adjusting means with a signal having a higher value among the control signals from both the control means. A steam-cooled gas turbine combined plant characterized by: