JPH0454204A - Control device for gas-extraction and condensation type turbine - Google Patents

Abstract

PURPOSE:To allow only the lower pressure side of a turbine to absorb variations in power demand caused by increases and decreases in flow rate of extracted gas, by providing a means for increasing and decreasing the flow rate of extracted gas in response to variations in power demand so as to absorb variations in power demand caused. CONSTITUTION:In a power plant having an gas-extraction and condensation type turbine 5, a governor 21 is provided for controlling the pressure at the extraction port 7 of the turbine 5 and the output of a generator 22. With respect to the extraction pressure, the pressure at the extraction port which is detected by a pressure detector 23 provided in an extracted gas line 9 is compared with a desired value, and a correction signal is delivered from the governor 21 to an extracted 988 adjusting valve 8 so as to control the pressure of the pressure at the extraction port 7 in order to make the pressure at the extraction port 7 coincident with the desired value. Meanwhile, as to the power demand, a demand signal is compared, at the governor 21, with an generator output delivered from a power meter 24 so as to deliver a correction signal from the governor 21 to a main stream adjusting valve 4 in order to make the output power of the generator which can code with the power demand signal, thereby it is possible to control the output power of the generator.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a control device for an extraction condensate turbine installed in a steam power generation facility.

Conventional technology The operating status of a bleed condensate turbine is determined by the steam demand (the amount of extracted air required) and the power demand (the amount of electric power required), but the steam demand and power demand are not always constant, and the turbine user Depending on the circumstances, rapid fluctuations may occur over and over again; for example, as shown in FIG. 3, sudden changes in steam or power demand may occur eight times a day.

In the conventional technology, fluctuations in steam demand are dealt with mainly by operating the extraction control valve, and fluctuations in power demand are handled by operating the main steam control valve.

In other words, fluctuations in steam demand can be absorbed by the low-pressure turbine section of the extraction condensation turbine, but this operation alone will cause the turbine output to fluctuate, so fluctuations in turbine load and power demand can be absorbed. For this reason, fluctuations are absorbed by both the high pressure and low pressure turbine sections of the extraction condensate turbine, and ultimately fluctuations in power demand are absorbed by adjusting the boiler load (amount of evaporation).

Problems to be Solved by the Invention As mentioned above, in the prior art, extraction and condensation turbines (high-pressure and low-pressure turbines) and
It is necessary to respond by changing the operating conditions of the boiler.

However, in general, in power generation equipment such as boilers, steam turbines, and piping, sudden load changes are accompanied by sudden temperature changes in each part of the equipment, causing thermal stress (the larger the temperature change, the greater the thermal stress generated). Therefore, as shown in FIG. 3, under operating conditions in which rapid load changes are repeated, the life of the equipment is significantly shortened. In particular, in the high-temperature parts of a steam turbine (near the governor stage), the stress that constantly acts on each part is high and the temperature is high, so the creep strength of the material is required.
In general, there is a tendency for there to be little margin in terms of strength. If thermal stress due to load fluctuations is repeatedly applied to such locations, cracks may occur, which is a serious problem.

The present invention has been made in order to solve the problems of the prior art, and provides a bleed air recovery system that can safely handle severe operations with repeated sudden changes in power demand without causing cracks or the like due to thermal stress. The present invention aims to provide a water turbine control device.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a control device for an extraction condensate turbine with means for increasing or decreasing the extraction flow rate in response to fluctuations in power demand. It is designed to absorb fluctuations in power demand through increases and decreases.

Effect: According to the above means, fluctuations in power demand are converted into increases and decreases in the flow rate of extracted air, so fluctuations in power demand are absorbed only on the low-pressure turbine side without changing the operating conditions on the high-pressure turbine side. becomes possible.

EXAMPLE Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an example of a power plant having an extraction condensate turbine equipped with a control device according to the present embodiment.

In FIG. 1, steam generated from a boiler 1 passes through a main steam pipe 2, a main steam stop valve 3, and a main steam control valve 4, and flows into a high-pressure turbine section 6 of an extraction condensate turbine 5. and,
In this high-pressure turbine section 6, the steam expands to the pressure of the extraction lower air and performs work. The pressure of this bleed air lower is controlled to be constant at all times by a bleed air regulating valve 8, and the pressure of the bleed air lower
An amount of steam corresponding to the amount used on the process side of the process air supply line 10 branched from and extending from is extracted. The remaining steam flows into the low pressure turbine section 11 of the extraction condensation turbine 5 through the extraction control valve 8 and does work while being thermally expanded to the vacuum of the condenser 13. The exhaust gas from the low pressure turbine section 11 is supplied to the condenser 13 through the line 12, where it is cooled and condensed by cooling water, and the condensed water (condensate) is passed through the line 15 by the condensate pump 14. is supplied to the deaerator 16 through. A portion of the bleed air is blown into the deaerator 16 through a line 17 that branches off from the bleed line 9 and extends. The feed water thus heated and freed of dissolved gases is then pumped into line 1 by feed water pump 18.
It is supplied to the boiler 1 through 9 and becomes steam again.

In the power plant described above, the governor 21 also controls the pressure in the bleed lower of the bleed condensate turbine 5 and the output of the generator 22.

That is, regarding the bleed pressure, the bleed port pressure detected via the pressure detector 23 provided in the bleed line 9 is compared with a predetermined target value, and the bleed port pressure is adjusted to match the target value. A correction signal is sent from the governor 21 to the bleed air control valve 8 to control the pressure of the bleed air lower. Also,
Regarding power demand, power demand signal and generator 2
The governor 21 compares the output of the generator input via the wattmeter 24 attached to the power meter 2 and sends a correction signal to the main steam control valve 4 so that the output of the generator matches the power demand signal. and controls the generator output.

The above operation mode is the operation mode when the power demand is high in FIG. 3.

Next, the operation mode when the power demand suddenly decreases will be explained.

In this case, when a sudden decrease in the power demand is detected by the power demand signal, the system is installed in the relief line 25 which is arranged to branch off and extend from the process air supply line (air bleed line) 10 according to the present embodiment. Relief valve 2
At 6, an open signal is issued from the governor 21. Then, when the relief valve 26 opens, the amount of bleed air increases, so the pressure in the bleed air lower decreases. Then, the governor 21 moves the extraction control valve 8 in the closing direction to restore the extraction pressure, and as a result, the amount of steam flowing into the low pressure turbine section 11 of the extraction condensation turbine 15 decreases, and the output of the generator 22 decreases. do.

At this time, the relief valve 26 is controlled by the governor 21 so as to have a valve opening degree that realizes an increase in the amount of extracted air that causes a decrease in the generator output equal to the decrease in the power demand. The magnitude of the signal output to the relief valve 22 is adjusted in the governor 21 so that the relief valve 26 performs the above operation in response to the signal, and the main steam control valve 4 adjusts the generator output to the power demand by the above operation. Since the governor 21 does not issue a correction signal to compensate for the change, the opening is maintained at the same level as before the sudden decrease in power demand, so the turbine operating state shifts to trajectory B shown in Figure 2. .

Further, when the power demand increases rapidly, the governor 21 issues a close signal to the relief valve 26, contrary to the above.

As a result, the relief valve 26 closes and the amount of extracted air decreases, so the pressure in the extracted air lower rises, and in order to restore this, the extracted air control valve 8 opens, so the low pressure turbine section 1 of the extracted air condensate turbine 5
1 increases, resulting in an increase in generator output corresponding to the increase in power demand.

In addition, in FIG. 2, solid lines (■), (2), and (2) each indicate an operating state in which the amount of extracted air is constant. Further, the solid line ■ indicates the maximum amount of condensate, and the solid line ■ indicates the minimum amount of condensate. Furthermore, a solid line ■ indicates a change in generator output.

In addition, the chain line A indicates a change in the operating state with constant extraction (
(change in generator output).

As described above, according to the present invention, the bleed air flow rate is increased in response to a sudden decrease in power demand, so that the operating state changes from point A to point ＼ along the trajectory of chain line B shown in FIG. Transition. On the other hand, conventionally, in an extraction condensing turbine operated at point A, the operating state is shifted to the point inlet position along the trajectory of chain line A in order to throttle the turbine inlet flow rate in response to a decrease in power demand.

That is, in the present invention, in FIG. 2, the operating state of the turbine is changed from the conventional path shown by A to the path shown by B in response to fluctuations in power demand.

If the operating state of the extraction condensate turbine is changed in response to fluctuations in power demand along the trajectory shown in B in Figure 2, the flow rate at the turbine inlet will change on the high-pressure turbine side before and after the change in operating state. Since there is no change, the operating condition does not change, and therefore, there is no temperature change that causes thermal stress.

On the other hand, since the amount of steam flowing inside the low-pressure turbine section changes, temperature changes occur inside the low-pressure turbine section, but since the steam temperature is in the low temperature range, the temperature change is small, and the pressure is high even with respect to the creep strength of the material. There is no influence from the high temperature part of the turbine section.

In addition, in order to realize the change in the operating state of trajectory B shown in Fig. 2, it may be necessary to increase the amount of extracted air from the turbine beyond the amount of steam used (required amount of steam) on the process side. By guiding surplus steam to a heat storage device such as sensible heat, latent heat, or chemical heat storage, it is possible to avoid the situation where steam is wasted.

As can be seen from Figure 2, there is a limit to the amount of power demand that can be absorbed by the low-pressure turbine section alone due to operational limitations of the low-pressure turbine section, and for any further fluctuations, the turbine inlet It is necessary to deal with this by adjusting the flow rate.

Furthermore, in FIG. 1, even if the controlled objects of the bleed air control valve 8 and the relief valve 26 are switched, that is, the bleed air control valve 8 controls the output of the generator 22, and the relief valve 26 controls the pressure of the bleed air lower. As described above, the operating state can be changed along the trajectory B in FIG. 2.

Effects of the Invention As described above, according to the present invention, a control device for an bleed condensing turbine is provided with means for increasing or decreasing the bleed air flow rate in response to fluctuations in power demand, and the power demand is increased or decreased by increasing or decreasing the bleed air flow rate. We try to absorb fluctuations, so
It is possible to absorb fluctuations in power demand only on the low-pressure turbine side without changing the operating status of the high-pressure turbine side, thereby eliminating temperature changes that cause thermal stress in the high-pressure turbine side. In addition, even if temperature changes occur in the low-pressure turbine section, the width is small, so even if thermal stress is repeated, cracks will not occur, and various other excellent effects can be achieved.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a power generation plant showing an example of a control device for an extraction condensate turbine according to the present invention, FIG. 2 is a diagram showing the operating range of an extraction condensate turbine according to the present invention and a conventional example, and FIG.
The figure is a diagram showing an example of daily fluctuations in steam or electric power demand of an extraction condensate turbine. 1. Boiler, 5. Air extraction condensation turbine, 6. High pressure turbine section, 7. Air extraction port, 8. Air extraction control valve, 9. Air extraction line, 10. Process air supply line, 11.. Low pressure turbine section, 13. Condenser, 16. Deaerator, 21.
・Governor, 25..Relief line, 26..Relief valve.

Claims (1)

[Claims] A control device for an bleed condensate turbine, characterized in that a means for increasing or decreasing the bleed air flow rate in response to fluctuations in power demand is provided, and the fluctuations in the power demand are absorbed by increasing or decreasing the bleed air flow rate.