JPH0392507A - Turbine bypass device for steam turbine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to a turbine bypass device for a steam turbine. (Prior art) Turbine bypass devices are installed for the purpose of increasing the flexibility of plant operation by eliminating or relaxing the mutual constraints between the boiler and the turbine. It has functions such as absorbing differences and also functioning as a boiler safety valve.

FIG. 3 shows a conventional turbine bypass device for a reheat turbine. As a high-pressure turbine bypass device, there is a high-pressure steam bypass pipe 5 that connects a main steam pipe 3 and a low-temperature reheat steam pipe 4 to flow main steam generated from a boiler bypassing the high-pressure turbine 2, and a high-pressure steam bypass pipe 5 that connects the main steam pipe 3 and the low-temperature reheat steam pipe 4, and the steam of the high-pressure steam bypass pipe 5. It is composed of a high-pressure steam bypass valve 6 for controlling the flow rate and a desuperheater 7 for controlling the outlet temperature of the high-pressure steam/< Ipass valve 6. A valve 8 is installed. Also, as a low pressure turbine bypass device, a low pressure connecting high temperature reheat steam pipe 13 and condenser 12 is used to dump the steam that has passed through the reheater 9 to the condenser l2, bypassing the intermediate pressure turbine 10 and the low pressure turbine l1. It consists of a steam bypass pipe 14, a low pressure steam bypass valve 15 for controlling the steam flow rate of the low pressure steam bypass pipe 14, and a desuperheater 16 for controlling the outlet temperature of the low pressure steam bypass valve 15. ．． condenser l
The water condensed in step 2 is sent to the condensate pump 17 and the low-pressure feed water heating pipe 18.
, an air blower 19, a water supply pump 20, and a high-pressure feed water heating pipe 2l, the main steam is sent to the boiler 1, and the main steam that is heated there is again supplied to the high-pressure turbine 2, intermediate-pressure turbine 10, and low-pressure turbine 11. Ru. (Problems to be solved by the invention) This conventional turbine bypass device had the following problems. The first problem is the structure of the condenser 12. Typically, during turbine bypass operation, bypass steam flows horizontally into the upper body of the condenser 12. condenser l2
When a large amount of bypass steam expands inside the tank, the steam hits the condenser shell, internal structures, neck heater, upper part of the tube bundle, etc. at high speed and damages them, so consideration must be given to dispersing the steam inflow energy. Become. In particular, the amount of steam flowing into the condenser 12 is about 130% of the amount of steam at the outlet of the reheater due to the cooling water added to reduce the temperature during the process, and the energy is large. During normal operation, the amount of steam flowing into condenser l2 is distributed to each turbine 2, 10. to heat the boiler feed water.
The amount of steam extracted from No. 11 is about 30%, which is about 70% of the amount of steam at the outlet of the reheater. Therefore, in a turbine bypass device with a capacity of 100, during turbine bypass operation, 1.3/0.7 = 1.8 times as much bypass steam as in normal operation will flow into condenser l2, and from the viewpoint of heat load. Also, due to the steam flow velocity within the condenser 12, consideration in design and structure for overload operation may be necessary. The second problem is securing a large amount of cooling water.

Due to temperature restrictions on the condenser 12, low-pressure turbine 11, expansion joints, etc., the bypass steam must be cooled by the attemperator l6 before flowing into the condenser 12. Normally, condensate extracted from the discharge side of the condensate pump 17 is used as the cooling water for this cooling, but the condensate pump 17 also has a capacity of 1.
This results in an overload of about 8 times. Furthermore, the cooling water supplied to the desuperheater 16 needs to maintain a pressure commensurate with the bypass steam, and the condensate pump 17 needs to take care to meet the requirements for both flow rate and pressure. In some cases, it may be necessary to consider starting up a standby unit for the condensate pump 7 during turbine bypass operation. The third problem is equipment placement. The condenser l2 to which the low-pressure steam bypass pipe 14 is connected is originally connected to the neck heater and the exhaust pipe of the steam turbine for driving the boiler feedwater pump, and space for the connection of the low-pressure steam bypass pipe l4 is created in the condenser l2. There is also the problem of having to secure. It is necessary to secure a space inside the upper body of condenser l2 to allow bypass steam to flow in. For this reason, the dimensions of the upper body of the condenser I2 become large, requiring special consideration in equipment arrangement. Furthermore, since the low-pressure bypass steam has a small specific volume and a large weight flow rate, the low-pressure steam bypass pipe 14 has a large diameter, which also poses a problem in equipment arrangement.

An object of the present invention is to provide a turbine bypass device for a steam turbine that solves all of the above-mentioned problems through appropriate bypass steam processing. (Structure of the Invention) (Means for Solving the Problems) In order to achieve the above object, the present invention uses main steam generated in a boiler or reheated steam obtained by heating turbine exhaust gas in a reheater to In a turbine bypass device for a steam turbine that has a turbine bypass pipe that bypasses the turbine and leads directly to the condenser, a piping system is provided that connects the turbine bypass pipe and the feedwater heater or the oil air pipe that leads the turbine to the feedwater heater. It is characterized by (
Function) - During turbine bypass operation, a portion of the turbine bypass steam is guided to the feedwater heater and condensed through the piping system that connects the turbine bypass pipe and the feedwater heater. As a result, the amount of bypass steam flowing into the condenser is significantly reduced, and problems such as condenser overload, increased condenser size, and condensate pump overload can be resolved. (Example) Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 shows an example in which the present invention is specifically applied to a reheat turbine.

A branch pipe 22 is branched from the low-pressure steam bypass pipe 14 and connects to a high-pressure feed water heater 21 , a deaerator 19 , and a low-pressure feed water heater 18 .
The water is guided through check valves 23 to each feed water heater 1g, 21 and deaerator 19, where it is condensed. Orifice 24
is the amount of steam generated by the boiler during turbine bypass for each turbine 2, 10. The dimensions are determined so that the same pressure as the oil pressure for heating the feedwater obtained when flowing into 11 is obtained. A check valve 23 connects the intermediate and low pressure turbines 10, 1.1 to each feedwater heater 21.1 during normal operation. 18
It is installed in order to prevent the oil gas sent to the condenser 12 from flowing back through each branch pipe 22 to the condenser 12. Note that it is also possible to use other pressure reducing devices such as a throttle valve instead of the orifice 24.

Next, the effect of the above-mentioned W will be explained.

During turbine bypass operation, the low pressure steam bypass valve l5 is fully opened and bypass steam is released to the condenser 12 through the low pressure steam bypass pipe 14. At this time, a portion of the bypass steam is passed from the low pressure steam bypass pipe 14 through each branch pipe 22 to the high pressure feed water heater 21. It is discharged to the sharp air generator 19 and the low-pressure feed water heater 18, where it is cooled and condensed by the boiler feed water flowing therethrough.

In addition, as another effect of this embodiment, by adding a forced opening function to the check valve 23, when an abnormally high water level occurs in each feed water heater 21.18, it is forcibly opened, and each feed water heater 21. Vessel 21. 18 is discharged to condenser l2 via branch pipe 22 and low pressure steam bypass pipe 14, thereby draining each turbine 10. This makes it possible to avoid the worst situation where 11 hedren flows in. In this case, the low pressure steam bypass valve 15 is connected to each feedwater heater 21. The mechanism is such that it does not open due to a turbine trip caused by an abnormally high water level signal at 18, but remains closed.

Further, the present invention can be configured as follows instead of the above embodiment.

That is, the orifice 24 can be installed in the low pressure steam bypass pipe 14 as shown in FIG. Also,
The branch pipe 22 is connected to the feed water heater 21. Instead of connecting directly to 18, it is also possible to connect to an oil pipe.

〔Effect of the invention〕

As described above, according to the present invention, a part of the turbine bypass steam is recovered to a plurality of feed water heaters during turbine bypass operation, thereby preventing overload of the condenser, increase in condenser size, Problems in equipment placement due to overload, dog-mouthed turbine bypass pipes can be eliminated.

[Brief explanation of drawings]

Fig. 1 is a system diagram of a turbine bypass device showing one embodiment of the present invention, Fig. 2 is a system diagram of a turn bypass device showing another embodiment of the invention, and Fig. 3 is a diagram showing a conventional turbine bypass device. It is a system diagram. 1...Boiler 2...High pressure turbine 4
...Low temperature reheat steam pipe 5...High pressure steam bypass pipe 6...High pressure steam bypass valve 9...Reheater 10...Intermediate pressure turbine 1
1...Low pressure turbine 12...Condenser 13...
- High temperature reheat steam pipe 14...Low pressure steam bypass pipe 15...Low pressure steam bypass valve l8...Low pressure feed water heater 22...Branch pipe 24...Orifice 21...High pressure feed water heater 23... ··non-return valve

Claims (1)

[Claims] A turbine bypass device for a steam turbine having a turbine bypass pipe that directs main steam generated in a boiler or reheated steam obtained by heating turbine exhaust gas in a reheater to a condensing pipe bypassing a plurality of turbines. A turbine bypass device for a steam turbine, comprising a piping system connecting a bypass pipe and a feedwater heater or a bleed pipe from the turbine to the feedwater heater.