JPH11166403A - Turbine bypass steam supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a turbine bypass steam supply device which can reduce plant starting loss or improve plant efficiency so as to use thermal energy effectively by recovering steam which is escaped to a condenser into other system so as to be reused during a turbine bypass operation. SOLUTION: A thermal electric power plant comprises the turbine bypass system consisting of two-stage bypass systems of a high pressure bypass system which bypasses a high pressure turbine 3 to flow main steam into a repeat steam pipe 4, and a low pressure bypass system which bypasses an intermediate pressure turbine 5 and a low pressure turbine 6 to reheat steam of the reheat steam pipe 4 into a desuperheater of a condenser 10 via a low pressure bypass valve 8, wherein a turbine bypass steam recovery system is provided between the low pressure bypass valve 8 and the desuperheater 9, and the tubine bypass steam recovery system is connected to an extraction steam pipe of a feed water heater 17 or an auxiliary steam base pipe, so that turbine bypass steam which is just recovered into the condenser 10 as an excess steam can be supplied as the extraction steam of the feed water heater 17 or the auxiliary steam so as to reuse thermal energy of the steam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention aims at reducing plant start-up loss or improving plant efficiency by recovering and reusing steam that escapes to a condenser during a turbine bypass operation, and reducing heat energy. The present invention relates to a turbine bypass steam supply device that can be used effectively.

[0002]

2. Description of the Related Art The prior art of the present invention will be described with reference to FIG.

FIG. 3 shows a turbine bypass system in a conventional thermal power plant.

In the thermal power plant shown in FIG. 1, the main steam generated in the boiler 1 is supplied to a high-pressure turbine 3 through a main steam pipe 2 to drive the high-pressure turbine 3.

The steam that has worked in the high-pressure turbine 3 passes through a reheat steam pipe 4 and is reheated in the boiler 1 to drive the medium-pressure turbine 5. The low-pressure turbine 6 is driven by exhaust gas from the medium-pressure turbine 5.

[0006] In such a thermal power plant,
In order to control the main steam pressure and the reheat steam pressure within a specified value according to the power generation output, when the main steam pressure exceeds the specified value, the high-pressure bypass valve 7 opens and a part of the main steam is sent to the reheat steam pipe 4. When the reheat steam pressure in the reheat steam pipe 4 becomes equal to or higher than a specified value, the low-pressure bypass valve 8 opens, and a part of the reheat steam flows as excess steam to the condenser 10 via the desuperheater 9. Pressure rise is prevented.

The check valve 11 provided in the reheat steam pipe 4 is for preventing the steam from the high pressure bypass valve 7 from flowing back to the high pressure turbine 3.

Such a phenomenon that the pressure of the reheat steam in the reheat steam pipe 4 becomes equal to or higher than a specified value occurs in a process of starting the plant or in a low load region.

[0009]

As described above, in the prior art, the steam that has bypassed the turbine by the low-pressure bypass valve 8 is only recovered as excess steam to the condenser 10 through the cooler 9. No particular consideration was given to reusing the heat energy of the steam.

According to the present invention, the condenser 10 is conventionally used as surplus steam.
The steam generated during the plant start-up process or low-load area that was only recovered to another system can be recovered and reused to reduce plant startup loss or improve plant efficiency and effectively use thermal energy It is an object of the present invention to provide a turbine bypass steam supply device that can be used.

[0011]

According to the present invention, there is provided a high-pressure bypass system for bypassing a high-pressure turbine and supplying main steam to a reheat steam pipe, and a re-heating steam pipe for bypassing an intermediate-pressure turbine and a low-pressure turbine. In a thermal power plant having a turbine bypass system composed of a two-stage bypass system of a low-pressure bypass system in which hot steam flows to a desuperheater of a condenser via a low-pressure bypass valve, between the low-pressure bypass valve and the desuperheater A turbine bypass steam supply pipe branched from the turbine bypass steam pipe and connected to the feed water heater extraction pipe; a turbine bypass steam supply valve interposed in the turbine bypass steam supply pipe; A turbine bypass steam switching valve for switching the mounted turbine bypass steam to the condenser side or the feedwater heater extraction pipe side. A high-pressure bypass system that bypasses a high-pressure turbine and passes main steam to a reheat steam pipe; and a low-pressure bypass that bypasses a medium-pressure turbine and a low-pressure turbine and reheats steam in the reheat steam pipe. Of a low-pressure bypass system flowing to the condenser's desuperheater via a valve,
In a thermal power plant having a turbine bypass system including a two-stage bypass system, a turbine bypass steam supply pipe branched from a turbine bypass steam pipe between the low-pressure bypass valve and the desuperheater and connected to an auxiliary steam mother pipe; A turbine bypass steam supply valve for adjusting the pressure of steam sent to an auxiliary steam mother pipe provided in the turbine bypass steam supply pipe, and a turbine bypass steam provided in the turbine bypass steam pipe to the condenser side. Or a turbine bypass steam switching valve for switching to the auxiliary steam mother pipe side.

(Operation) A high-pressure bypass system for bypassing a high-pressure turbine and allowing main steam to flow to a reheat steam pipe, and a low-pressure bypass valve for bypassing an intermediate-pressure turbine and a low-pressure turbine and passing reheat steam from the reheat steam pipe In a thermal power plant having a turbine bypass system composed of a two-stage bypass system of a low-pressure bypass system flowing to a desuperheater of a condenser via a turbine, turbine bypass steam is generated in a start-up process or a low load region.

In the conventional apparatus, the turbine bypass steam is recovered as surplus steam as it is in the condenser through the desuperheater.

In the turbine bypass steam supply apparatus of the present invention, the turbine bypass steam that is recovered to the condenser as surplus steam is supplied as bleed air for the feed water heater or as auxiliary steam, so that the heat energy of the steam is effectively re-used. Can be used.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIGS. 1 and 2 show the configuration of an embodiment of the present invention in which the turbine bypass steam supply device of the present invention is applied to a steam power plant. In the description of FIG. 2, the same components as those in FIG. 1 are denoted by the same reference numerals, and duplicate description will be omitted.

The present invention is not limited to the illustrated embodiment, and it goes without saying that constituent elements may be changed or added as appropriate without departing from the spirit of the present invention.

First Embodiment A first embodiment shown in FIG. 1 is a turbine bypass between a low-pressure bypass valve 8 and a desuperheater 9 of a condenser 10 in the conventional apparatus shown in FIG. A steam switching valve 12 is interposed, and a turbine bypass steam supply pipe 14 is branched from a turbine bypass steam pipe 13 between the low-pressure bypass valve 8 and the turbine bypass steam switching valve 12.
Is supplied to the bleed pipe of the feed water heater 17 through the turbine bypass steam supply valve 15 and the bleed inlet valve 16 to supply heat to the feed water, and drain generated in the feed water heater 17 is supplied to the feed water heater drain pipe. 18, the feed water heater drain valve 19
Through the condenser 10.

Next, the operation of this embodiment will be described.

The feed water heated by the feed water heater 17 is supplied to the boiler 1 by a main feed pipe 21 via a feed water outlet valve 20, and is heated by the boiler 1 to generate main steam. The main steam generated in the boiler 1 is supplied to the high-pressure turbine 3 through the main steam pipe 2 to drive the high-pressure turbine 3. Then, the intermediate pressure turbine 5 is driven. Low pressure turbine 6
Are driven by the exhaust from the intermediate pressure turbine 5. The high-pressure bypass valve 7 is provided to control the main steam pressure within a specified value according to the generator output. When the main steam pressure in the main steam pipe 2 becomes equal to or higher than the specified value, the high-pressure bypass valve 7 opens. To the reheat steam pipe 4. The low-pressure bypass valve 8 is provided to control the reheat steam pressure within a specified value according to the generator output, and opens when the reheat steam pressure in the reheat steam pipe 4 becomes equal to or higher than the specified value. Then, a part of the reheated steam flows to the condenser 10 via the turbine bypass steam switching valve 12 and the desuperheater 9.

At this time, if the turbine bypass steam supply valve 15 is closed, the bypass steam is recovered to the condenser 10. However, the bypass steam is not only recovered to the condenser 10 but also recovered to the turbine 10. By closing the bypass steam switching valve 12 and opening the turbine bypass steam supply valve 15, the thermal energy of the steam can be effectively used again as bleed air to the feed water heater 15 via the bleed inlet valve 16. Reference numeral 22 denotes a check valve.

The operation of closing the turbine bypass steam switching valve 12 and using the turbine bypass steam supply valve 15 to use the turbine bypass steam as bleed air of the feed water heater 17
Is continuously controlled so that changes in the flow rate and pressure of the bypass steam do not affect the downstream side. The turbine bypass steam switching valve 12 and the turbine bypass steam supply valve 15 each have a flow rate adjusting function, and the turbine bypass steam supply valve 15 is controlled so that the bypass steam is within the flow rate required by the feed water heater 17. The flow rate of the steam switching valve 12 is controlled to return the excess steam throttled by the turbine bypass steam supply valve 15 to the condenser 10 because the required flow rate of the feed water heater 17 has been exceeded.

As described above, the apparatus of this embodiment performs feedback control based on the flow rate on the downstream side, so that it is possible to supply a stable bleed air to the feed water heater 17.

In addition, since the bypass steam is reused as bleed air in the feed water heater 17, the temperature of the feed water flowing through the main feed pipe 21 through the feed water outlet valve 20 can be raised, and the feed water temperature at the inlet of the boiler 1 can be raised. Therefore, the amount of combustion in the boiler 1 can be suppressed, and therefore the amount of fuel input to the boiler 1 can be reduced, and the startup loss of the plant can be reduced.
-Second Embodiment A second embodiment shown in FIG. 2 is a turbine bypass steam switching valve 12 between the low-pressure bypass valve 8 and the condenser 9 in the conventional apparatus shown in FIG. From the turbine bypass steam pipe 13 between the low-pressure bypass valve 8 and the turbine bypass steam switching valve 12 to the turbine bypass steam supply pipe 14.
And the bleed air from the turbine bypass steam supply pipe 14 is supplied to the auxiliary steam mother pipe 23 via the turbine bypass steam supply valve 15.

Not only does the reheated steam extracted as described above flow to the condenser 10 through the bypass steam switching valve 12 and the desuperheater 9, but also the turbine bypass steam switching valve 12 is closed and the turbine bypass steam supply valve 15 is closed. Is opened, the heat energy of the steam can be effectively used again as the auxiliary steam to the auxiliary steam mother pipe 23.

The turbine bypass steam is supplied to the auxiliary steam mother pipe 23.
The operation of closing the turbine bypass steam switching valve 12 and the operation of opening the turbine bypass steam supply valve 15 for use as auxiliary steam to the turbine are continuously controlled so that changes in the flow rate and pressure of the bypass steam do not affect the downstream side. . The turbine bypass steam switching valve 12 and the turbine bypass steam supply valve 15 each have a pressure adjusting function, and the turbine bypass steam supply valve 15 is controlled so that the bypass steam keeps the pressure of the auxiliary steam mother pipe 23 constant. The flow rate of the switching valve 12 is controlled so as to exceed the pressure of the auxiliary steam mother pipe 23 and return the excess steam throttled by the turbine bypass steam supply valve 15 to the condenser 10. As described above, since the feedback control is performed based on the pressure on the downstream side, it is possible to supply a stable steam to the auxiliary steam mother pipe 23.

Further, by reusing bypass steam as auxiliary steam in the auxiliary steam mother pipe 23, as shown in FIG. 2, for example, as shown in FIG. Steam can be supplied to the gasifier 25. In the figure, reference numeral 26 denotes a bleed inlet valve, 27 denotes a bleed check valve, and the condensate sent from the condensate pipe 28 to the deaerator 25 is heated and degassed and supplied from the water supply pipe 29 to the boiler 1.

That is, conventionally, it has been difficult to secure the heating deaeration steam from the auxiliary boiler, and the deaeration in the deaerator 25 has not been sufficiently performed. By reusing energy, it is possible to stably supply steam for heating and degassing, which tends to be insufficient. Accordingly, since the feedwater flowing through the feed pipe 29 is sufficiently degassed, it is possible to supply the boiler 1 with good water quality with little dissolved oxygen, so that the problem of corrosion inside the piping of the boiler 1 can be solved.

[0029]

According to the present invention, it is possible to effectively utilize the heat energy of the turbine bypass steam generated in the plant start-up process or in the low load region, which has only been recovered to the condenser as excess steam. There is an effect that the startup loss of the plant can be reduced and the efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a first embodiment of the present invention.

FIG. 2 is a system diagram showing a second embodiment of the present invention.

FIG. 3 is a system diagram showing a conventional apparatus.

[Explanation of symbols]

1 ... boiler, 2 ... main steam pipe, 3 ... high-pressure turbine,
4 Reheat steam pipe, 5 Medium pressure turbine, 6 Low pressure high pressure turbine, 7 High pressure bypass valve, 8 Low pressure turbine, 9 Temperature reducer, 10 Condenser, 11 ……Check valve,
12 ... turbine bypass steam switching valve, 13 ... turbine bypass steam pipe, 14 ... turbine bypass steam supply pipe, 15 ... turbine bypass steam supply valve, 16 ... bleed inlet valve, 17 ... feed water heater, 18 ... Drain pipe for feed water heater 19, Drain valve for feed water heater 20, Water feed outlet valve 21, Main feed pipe 22, Check valve 23, Auxiliary steam mother pipe 24 Vapor heating steam pressure control valve, 25
... deaerator, 26 ... bleed inlet valve, 27 ... bleed check valve, 28 ... condensing pipe, 29 ... water supply pipe.

Claims (4)

[Claims] 1. A high-pressure bypass system for bypassing a high-pressure turbine and allowing main steam to flow to a reheat steam pipe, and bypassing an intermediate-pressure turbine and a low-pressure turbine to pass reheat steam from the reheat steam pipe via a low-pressure bypass valve. In a thermal power plant having a turbine bypass system consisting of a two-stage bypass system of a low-pressure bypass system flowing to a desuperheater of a condenser, a branch from a turbine bypass steam pipe between the low-pressure bypass valve and the desuperheater is provided. A turbine bypass steam supply pipe connected to the feedwater extraction pipe, a turbine bypass steam supply valve interposed in the turbine bypass steam supply pipe, and a turbine bypass steam interposed in the turbine bypass steam pipe. A turbine bypass steam switching valve for switching between a water heater side and a feed water heater extraction pipe side. Feeding device. 2. A low-pressure bypass valve, a low-pressure bypass valve, a low-pressure bypass valve, a low-pressure bypass valve, and a low-pressure bypass valve. The turbine bypass steam supply device according to claim 1, further comprising a control device that controls the turbine bypass steam switching valve. 3. A high-pressure bypass system for bypassing a high-pressure turbine and allowing main steam to flow to a reheat steam pipe, and bypassing an intermediate-pressure turbine and a low-pressure turbine to pass reheat steam from the reheat steam pipe via a low-pressure bypass valve. In a thermal power plant having a turbine bypass system consisting of a two-stage bypass system of a low-pressure bypass system flowing to a desuperheater of a condenser, a branch from a turbine bypass steam pipe between the low-pressure bypass valve and the desuperheater is provided. A turbine bypass steam supply pipe connected to the auxiliary steam mother pipe, a turbine bypass steam supply valve for regulating the pressure of steam sent to the auxiliary steam mother pipe interposed in the turbine bypass steam supply pipe, and the turbine bypass steam A turbine bypass steam switching valve for switching turbine bypass steam interposed in the pipe to the condenser side or the auxiliary steam mother pipe side; A turbine bypass steam supply device. 4. A low-pressure bypass valve, a turbine bypass steam supply valve, and a turbine bypass steam receiving command, in response to a turbine bypass steam switching command for reusing turbine bypass steam generated in a plant startup process or a low load region as auxiliary steam. The turbine bypass steam supply device according to claim 3, further comprising a control device that controls the steam switching valve.