JPS6069218A - Turbine bypass system - Google Patents

Abstract

PURPOSE:To enable to perform stable turbine bypass operation without changing the design of a deaerator, by utilizing steam having a higher enthalpy as a heating source for the deaerator, and taking out turbine bypass steam reheated by a reheater from a high-temperature reheat steam pipe. CONSTITUTION:Main steam supplied from a boiler 21 is carried to a high-pressure turbine 22 via a main steam pipe 23 and a stop valve 24 while exhaust gas of the boiler 21 is supplied to a mecium- and low-pressure turbine 27 via a low- temperature reheat steam pipe 26, a reheater 25, a high-temperature reheat steam pipe 28 and a stop valve 29. A low-pressure turbine bypass pipe 36 is extended between the steam pipe 28 and a condenser 35 while a high-pressure turbine bypass pipe 30 is extended between the main steam pipe 23 and the steam pipe 26. The condenser 35 is connected to the boiler 21 via a deaerator 41. At the time of turbine bypass operation, high-pressure turbine bypass reheat steam having a high enthalpy is introduced into the deaerator 41 as heated steam by opening a changeover valve 44 provided in an emergency heated-steam pipe.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in turbine bypass systems for thermal power plants with reheat turbines.

In a conventional thermal power plant of this kind, as shown in FIG. 1, when the turbine bypass system is used, the turbine main steam stop valve 1 and the reheat steam stop valve 2 are closed. Therefore, the main steam generated in the boiler 3 passes through the main steam pipe 4,
The steam is depressurized and heated by the high-pressure turbine bypass valve 5 and enters the low-temperature reheat steam pipe 6. This steam is heated in a reheater 7 to become reheated steam, passes through a high-temperature reheated steam pipe 8, is depressurized and temperature-reduced in a low-pressure turbine bypass valve 9, and enters a condenser 10.

The condensate condensed in this condenser 10 is transferred to a condensate pump 11.
The water is then sent to the deaerator 12 as low-pressure water and degassed. The deaerated low-pressure feed water is sent to the boiler 3 as high-pressure water supply by the boiler feed water pump 13.

Although auxiliary steam from elsewhere may be used for deaeration in the deaerator 12, high-pressure turbine bypass steam from the low-temperature reheat steam pipe 6 is often used via the emergency heating switching valve 14.

The deheated water from the high-pressure turbine bypass valve 5 and the low-pressure turbine bypass valve 9 is often taken out and used from the outlets of the boiler feed water pump 13 and condensate pump 11, respectively.

Therefore, during the turbine bypass operation, the amount of low-pressure water supplied to the deaerator 12 increases by the amount of deheated water in the high-pressure turbine bypass, compared to the normal operation (operation that does not use the turbine bypass). In addition, the low-pressure feed water temperature decreases to the condensate temperature at the outlet of the condenser 1o due to the disappearance of heating steam from the low-pressure feed water heater. Both of these changes in low pressure water supply conditions require an increase in the amount of steam for degassing.

However, there is a certain limit between the amount of low-pressure water supplied to the deaerator 12 and the amount of heated steam, as shown in FIG. 2, in order to prevent flooding of the low-pressure water supplied to the deaerator 12. In other words, at the same operating pressure, the increase in water supply amount is the ratio of (steam load) / (water supply load) allowed by the deaerator due to an increase in tray load.
- generally does not correspond to the increase in the allowable amount of heating steam.

Therefore, depending on the conditions of the turbine bypass, the amount of heating steam required by the deaerator may not be able to be input to the deaerator.

In view of the problems of the prior art, the present inventor conducted extensive research to solve the problems, and found that the operating characteristics of the deaerator during turbine bypass operation are as follows: While it is necessary to increase the amount of heating steam, it is possible to understand the contradictory characteristics that the amount of heating steam cannot be increased much due to deaerator performance. They found that the problem could be solved by using steam with higher enthalpy as the heating source for the deaerator, and based on this new knowledge, they completed the present invention.

That is, in order to solve the problems of the prior art, the present invention uses reheat turbine bypass steam heated by the reheater as a heating source for a steam total deaerator having a higher enthalpy, thereby increasing the temperature of the reheat turbine bypass steam heated by the reheater. The purpose is to provide a novel turbine bypass system that can be taken out from the reheat steam pipe.

In order to achieve this objective, the turbine bypass system of the present invention is provided with a main steam pipe 23 that guides main steam generated in the boiler 21 to the high-pressure turbine 22.
3 is provided with a turbine main steam stop valve 24, and a low temperature reheat steam pipe 2 that guides the exhaust gas of the high pressure turbine 22 to a reheater 25.
6 is provided, and a high temperature reheat steam pipe 28 is provided to guide reheat steam from the reheater to the medium/low pressure turbine 27, and the high temperature reheat steam pipe 28 is provided with a reheat steam stop valve 29. and a low pressure turbine bypass pipe 36 that connects the high temperature reheat steam pipe 28 and the condenser 35, and a high pressure turbine bypass pipe 30 that connects the main steam pipe 23 and the low temperature reheat steam pipe 26. , in a turbine bypass system in which the condenser 35 is connected to the boiler 21 via a deaerator 41, the high temperature reheat steam pipe 28 and the deaerator 41 are connected by an emergency heating steam pipe 43. The steam pipe 43 is characterized in that an emergency heating switching valve 44 is provided.

The invention will now be described in detail with reference to illustrative embodiments.

FIG. 3 shows the configuration of the turbine bypass system of the present invention. In the figure, a main steam pipe 23 is disposed between the two to guide main steam generated in a boiler 21 to a high-pressure turbine 22, and the main steam pipe 23 is provided with the high-pressure A turbine main steam stop valve 24 is provided to stop main steam from flowing into the turbine 22.

In order to guide the exhaust gas of the high pressure turbine 22 to the reheater 25, a low temperature reheat steam pipe 26 is disposed between the two.
A high-temperature reheat steam pipe 28 is provided to guide reheat steam to the medium/low pressure turbine 27, and a reheat steam stop valve 29 is installed in the high-temperature reheat steam pipe 28 for the same purpose as the main steam up valve 24. is provided.

In the figure, for high-pressure turbine bypass, a high-pressure turbine bypass valve 31 of the steam conversion valve type is installed in a high-pressure turbine bypass pipe 30 that connects the main steam pipe 23 and the low-temperature reheat steam pipe 26; Water supply pump 32
Higher pressure water supply is supplied as detemperature water via the high pressure spray regulating valve 33. This regulating valve 33 controls the high pressure turbine bypass steam temperature by a temperature regulator 34 provided downstream of the high pressure turbine bypass valve 31.

In the figure, a low-pressure turbine bypass valve 37 of the steam conversion valve type is installed in the low-pressure turbine bypass pipe 36 that connects the high-temperature reheat steam pipe 28 and the condenser 35 for the low-pressure turbine bypass 117). A part of the low-pressure feed water is supplied from the condensate pump 38 as reduced temperature water via the low-pressure spray regulating valve 39. This adjustment valve 3
Reference numeral 9 controls the low pressure turbine bypass steam temperature by a temperature regulator 40 provided downstream of the low pressure turbine bypass valve 37.

In the same figure, during the low pressure turbine bypass operation, the low pressure water supplied to the deaerator 41 has the condensate temperature of the condenser 35 because there is no turbine bleed air which is a heating source for the low pressure feed water heater 42. In order to heat and deaerate this low-temperature, low-pressure feed water, an emergency heating steam pipe 43 is provided from the high-temperature reheating steam pipe 28 to the deaerator 41 to supply reheating high-pressure turbine bypass steam, and this A switching valve 44 is provided.

According to the above-mentioned turbine bypass system I7, during turbine bypass operation, the heating steam of the deaerator 41 is lower than the high pressure turbine bypass steam (low pressure feed water temperature is lowered to the condensate temperature without heating steam). -C) By using reheated high-pressure turbine bypass steam with high enthalpy, the amount of steam used for the deaerator can be reduced.

As described above, in the turbine bypass of the present invention, a main steam pipe is provided to guide main steam generated in the boiler to the high pressure turbine, the main steam pipe is provided with a turbine main steam stop valve, and the high pressure turbine A low-temperature reheat steam pipe is installed to guide the exhaust gas from the reheater to the reheater, and a high-temperature reheat steam pipe is installed to lead the reheat steam from the reheater to the medium/low pressure turbine. is provided with a reheat steam stop valve, and is provided with a low pressure turbine bypass pipe that connects the high temperature reheat steam pipe and the condenser, and a high pressure turbine bypass pipe that connects the main steam pipe and the low temperature reheat steam pipe. In a turbine bypass system in which the condenser is connected to the boiler via a deaerator, the high temperature reheat steam pipe and the deaerator are connected to each other by an emergency heating steam pipe, and the emergency heating steam is connected to the high temperature reheat steam pipe and the deaerator. Since the pipe is equipped with an emergency heating switching valve, the heat balance (No. 4-1) during operation at maximum continuous evaporation rate (MCR) is
(Fig. 4-2), heat balance when all steam turbine is bypassed during operation in MCR, and deaerator heating steam is used as high-pressure turbine bypass steam (Fig. 4-2), As can be seen from the heat balance (Figure 4-3) when steam heating steam is used as reheated high-pressure turbine bypass steam, in the case of the conventional system,
About 560 TON/H of low-pressure water supply to the deaerator requires heating steam of about 124 TON/H, but with the new system (this invention), the low-pressure water supply of about 579 TON/H
On the other hand, heating steam only requires 109 TON/H.

This means that when the deaerator tray area to, c+375 (operating pressure f, 7 kg/cIlt), in the conventional system, the tray load is 51.2 TON/week and (steam load)/(feed water load) is 19 .8%, 110.9
TON/I (L) cannot be put into the deaerator, which means that the above-mentioned deaerator requirement of 124 TON/H cannot be met.

However, in the new system (the present invention), when the tray load is 53T ON /u/m, (steam load) / (feed water load) is 190%, and 110.0TON/H can be input to the deaerator. Yes, this is the deaerator required amount of 109T as mentioned above.
It exceeds ON/H.

Therefore, in the conventional system, the required amount of heating steam cannot be input to the deaerator, the heat balance shown in FIG. 4-2 cannot be maintained, and stable turbine bypass operation cannot be performed. In such cases, it is possible to increase the tray area of the deaerator to accommodate the necessary amount of steam input to the deaerator, but with the new system (this invention), it is possible to change the specifications of the deaerator. The necessary amount of heat can be input to the deaerator without any need for heating.

[Brief explanation of the drawing]

Figure 1 is a piping diagram of a conventional turbine bypass system.
Fig. 2 is a relationship diagram between the deaerator heating steam amount and low-pressure feed water, Fig. 3 is a piping diagram of the turbine bypass system of the present invention, and Fig. 4
Figure-1 is a pipe system diagram of heat balance during MCR [maximum continuous evaporation] normal operation, Figure 4-2 is a pipe system diagram of heat balance during conventional MCR, turbine bypass operation,
Figure 3 is a heat balance pipe diagram during bypass operation of the MCR turbine of the present invention. 21. Boiler, 22. High pressure turbine, 23. Main steam pipe, 24. Main steam stop valve, 25. Reheater, 26.
・Low-temperature reheat steam pipe, 27. Medium/low pressure turbine, 28.
・High temperature reheat steam pipe, 29... Reheat steam stop valve, 30...
High pressure turbine bypass pipe, 31... High pressure turbine bypass valve, 32... Boiler feed water pump, 33... High pressure spray adjustment valve, 34... Temperature regulator, 35... Condenser,
36...Low pressure turbine bypass pipe, 37...Low pressure turbine bypass valve, 38...Condensate pump, 39...Low pressure spray adjustment valve, 40...Temperature regulator, 41...Deaerator, 4
2...Low pressure water heater, 43...Emergency heating steam pipe,
44...Emergency heating switching valve. (11) (Z emotion nil <ay) IJ SoP 149” tlu One story story four songs magazine

Claims (1)

[Claims] A main steam pipe is provided to guide main steam generated in the boiler to a high-pressure turbine, a turbine main steam stop valve is provided in the main steam pipe, and a low-temperature reheat steam pipe guides exhaust gas from the high-pressure turbine to a reheater. A high-temperature reheat steam pipe is installed to guide reheat steam from the reheater to the medium/low pressure turbine, and the high-temperature reheat steam pipe is provided with a reheat steam stop valve. A low-pressure turbine bypass pipe connects the high-temperature reheat steam pipe and the condenser, and a high-pressure turbine bypass pipe connects the main steam pipe and the low-temperature reheat steam pipe. In the turbine bypass system connected to the boiler, the high temperature reheat steam pipe and the deaerator are connected by an emergency heating steam pipe, and the emergency heating steam pipe is provided with an emergency heating switching valve. A turbine bypass system characterized by: