JPS59110811A - Steam turbine plant - 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 [Technical Field of the Invention] The present invention relates to a steam turbine plant having a turbine bypass device.

[Technical background of the invention and its problems] Fig. 1 is a schematic diagram of a general steam turbine plant having a turbine-by-unit device, in which the steam generated in the boiler 1 is passed through one smoke pipe. 2 through the main steam stop valve 3 and steam control f
It is supplied to the high pressure turbine 5 via f41. After the steam supplied to the high pressure turbine 5 performs work there,
Low temperature reheat tube6. Reheater 7 and high temperature reheat tube 8. It is then sequentially introduced into an intermediate pressure turbine 10 and a low pressure turbine 11 via an intercept valve 9 and the like, performs work in the intermediate pressure turbine 9 and the low pressure turbine 11, and drives a generator (not shown) together with the high pressure turbine 5. On the other hand, the steam that has worked in the low-pressure turbine 1 is introduced into the condenser 12 and condensed, and the condensed water is passed through the deaerator water level control valve 14 by the condensate pump 13 and sent to the low-pressure feed water heater 15. The air is sent there, and after being preheated, it is introduced into the deaerator 16. The water degassed by the deaerator 16 is returned to the boiler 1 as feed water via a high-pressure feed water heater 18 by a feed water pump 17.

Further, the main steam pipe 2 is provided with a high pressure turbine bypass valve 19.
The high-pressure turbine output pipe 20 (D-end) is connected to the high-pressure turbine output pipe 20 (D-end), the bent end of the high-pressure turbine bypass pipe 20 is connected to the low-temperature reheat pipe 6, and the high-temperature reheat pipe 8 has a low-pressure turbine bypass valve 21. A low-pressure turbine bivan tube 22 is connected thereto, and its bent end is connected to the condenser 12 via a temperature reduction device 23.

A part of the condensate discharged from the condensate pump 13 can be supplied to the temperature reduction device 23 as cooling water via a cooling water nupley valve 24, and the steam that has passed through the low pressure turbine bybanu valve 21 After the water has been sufficiently cooled, it is stored in the condenser 13.

Therefore, when the turbine output needs to be lower than the boiler output, by opening the high-pressure turbine bypass valve 19 and the low-pressure turbine bypass valve 21, surplus steam can be supplied to both the turbine bypass valves 120 and 22. is introduced into the condenser 12 after its temperature is reduced by the temperature reducing device 23.

Incidentally, the high-pressure feedwater heater 18 and the low-pressure feedwater heater 15 are supplied with bleed air appropriately extracted from the intermediate stage of each turbine as heating steam.
The drain generated in step 8 is collected in a deaerator 16.

Therefore, during normal operation, the feed water flow rate 'eQ,B sent to the boiler, the drain flow from the feed water heater flowing into the deaerator 16, tteQds, and the deaerator water level control valve 14'i by the condensate pump are degassed. If the condensate flow 1tkQ0 is fed to the gas tank 16, then QB=Qo+Qd, which is 1.13: Qd? Q0=1:
The ratio is about 0.4:0.6, and the flow rate of condensate passing through the deaerator water level control valve is about 60 times the flow rate of water supply.

On the other hand, during turbine bypass operation, the amount of air extracted from the turbine is zero, and almost all of the steam generated in the boiler is introduced into the condenser 12 through the low-pressure turbine bypass pipe 22.

Therefore, in this case, water corresponding to the flow rate of steam generated by the boiler, that is, an amount of condensate equal to the flow rate of feed water, is transferred to the deaerator water level control valve 14.
It is necessary to introduce the gas into the deaerator 16 through the process. Roughly speaking, in this case, a part of the water discharged from the condensate pump 12 is supplied to the temperature reducing device 23 as cooling water in order to reduce the temperature of the Vaibanu steam, so the flow rate through the condensate pump is equal to this cooling water. only more. By the way, since the flow rate of this cooling water is generally about V2 of the steam amount, the condensate flow flowing through the condensate pump -
i? :=, , and the flow rate flowing through the deaerator water level control valve during this turbine bypass operation is Q. 1, QB=Qo1 (4) and Q p =Q Ql + 2 QB =t, s
Qc+, and the respective flow rate ratios when two turbines are bypassed are: QB:Q, d:Q. +: Qp = 1: 0:
1: 1.5.

From this, the flow rate ratio of the condensate pump section during normal operation and turbine bypass operation in order to establish a balance between the inflow and outflow of water in the deaerator and condenser is: Qo: Q, p = 1 : 2. s and 9, and the flow rate ratio of condensate flowing through the deaerator water level control valve is CLo:Q. + = 1: 1. ? Therefore, it is necessary to greatly increase the condensate flow rate during turbine bypass.

Furthermore, in the case of a coal-fired boiler, the rate of decrease in boiler output is small, so after switching to plant power plant operation or switching to boiler standalone operation due to an accident in the power system, the amount of evaporation in the boiler is reduced. It takes a long time for this to occur, and during this time it is necessary to flow a larger amount of condensate than during normal operation, as described above.

In addition, the water level in the condensate box is controlled to be kept constant by outflow to the outside of the system and supply from outside the system, but the maximum amount of water supplied is generally 10% of the flow rate flowing through the deaerator water level control valve. However, since the condensate pump and condensate line are only planned with a margin for the flow rate and pressure at 100% power generation load, the deaerator water level control valve Even when fully opened, the maximum flow rate that can flow through this part is about 110 to 130 inches, which is the flow rate when loaded with 100 inches.

Therefore, if the plant is operating under a high load such as 1oo1 output, and the turbine is operated alone or within the plant alone due to a system accident or the like, resulting in turbine bypass operation, the condenser is transferred from the condenser to the deaerator as described above. Although a large amount of condensate must be supplied, the required flow rate cannot be supplied, and the water level in the deaerator drops as shown by the dotted line in Figure 2, while the water level in the condenser drops to the solid line. It rises as shown in . Thereafter, as the boiler output decreases, the feed water flow rate a decreases, and when it becomes lower than the condensate flow rate, the water level in the deaerator starts to rise. Since the flow rate of condensate flowing into this beriberi machine is controlled only by the water level of the deaerator, the water level of the deaerator becomes the set value, and the flow rate of condensate flows at the maximum amount that the system can flow. During this time, the deaerator water level control valve is kept fully open.

Since a large amount of water is sent to the deaerator even after the boiler output is reduced in this way, the water level in the water reservoir continues to drop due to the head weight that stabilizes the water level in the beriberi after the water supply and condensate flow rates are reversed.

In addition, the deaerator atomizes the inflowing condensate, and also includes a deaeration heating chamber that separates and removes non-condensable GANU in the feed water by directly heating the incoming condensate to saturation temperature with the bleed air of the turbine. It consists of a water storage tank that stores water supply,
The water stored in the tank is always mixed with the degassed supply water in the deaeration heating chamber through the internal piping, and the water stored in the tank is usually kept close to the saturation temperature. For this reason, when the temperature inside the deaerator decreased due to the turbine extraction being stopped or cooled condensate flowing into the deaerator, the pressure inside the deaerator simultaneously decreased, and the pressure inside the deaerator was no longer lower than the saturation pressure of the stored water. In some cases, a boiling phenomenon of stored water occurs, and the water level fluctuates rapidly.

By the way, a deaerator has a water storage tank that stores most of the water, and has a large tolerance for a drop in water level, whereas a condenser has a large tolerance for a rise in water level. , there is little margin for the lower limit of the water level. Therefore, as described above, when the condenser water level decreases, it may reach its lower limit, which may lead to the condensate pump being stopped and, therefore, the plant being stopped.

In addition, during turbine-by-vanu operation, the steam flowing through the turbine decreases, and in some cases reaches zero.The air extracted to the p1 deaerator and feed water heater decreases, and in some cases reaches zero, so the temperature inside the deaerator decreases. decreases due to decrease in deaerator bleed air, -1
ft, and at the same time, the feed water also flows into the deaerator at a lower temperature due to the reduced bleed air to the feed water heater. Therefore, the temperature inside the deaerator decreases rapidly, and the pressure inside the deaerator decreases accordingly. Therefore, when the internal pressure becomes lower than the saturation pressure of the stored water, a boiling phenomenon of the stored water occurs, and the water level fluctuates rapidly, making it impossible to control the water level.

In this way, in conventional turbine plants, the entire amount of bypass steam flows into the condenser during turbine bypass operation, so the condensation occurs after bypass operation starts.

An unbalance occurs in the feed water flow rate, and the condensate pump, piping, and deaerator water level control device cannot cope with it, and a large amount of condensate is taken until the water level in the deaerator recovers, resulting in a drop in the water level in the condenser. This may cause water pump stoppage and even plant stoppage. Further, when the pressure inside the deaerator decreases and becomes equal to or lower than the saturation pressure of the stored water, a boiling phenomenon occurs, which causes problems such as making it impossible to control the water level in the deaerator.

[Purpose of the invention]

In view of these points, the present invention prevents an abnormal drop in the condenser water level by controlling the deaerator water level during turbine-by-vanu operation, and prevents the occurrence of abnormal situations such as stopping the condensate pump or stopping plant operation. The purpose is to obtain a steam turbine plant that can prevent

[Summary of the invention]

The present invention provides a steam turbine plant equipped with a turbine bypass system W for introducing surplus steam generated in a boiler into a condenser by bypassing a boiler. A bypass steam supply pipe is installed to supply the water to the feed water heater or deaerator, etc., to prevent the occurrence of unbalanced condensate and feed water during turbine bypass operation. be.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 3 to 6. Note that the same parts as in FIG. 1 are given the same reference numerals, and detailed explanation thereof will be omitted.

FIG. 3 is a system diagram showing one embodiment of the steam turbine plant of the present invention, in which a bypass steam supply pipe 25 is branched and led out from a position immediately downstream of the low-pressure turbine valve 21 to the low-pressure turbine valve 22. The bypass steam supply pipe 25 is further branched into a first bypass steam supply pipe 25a and a second bypass steam supply pipe 25b, and the first bypass steam supply pipe 25a is used for high-pressure feed water heating. The second steam supply pipe 25b is connected to the feedwater heaters of each stage of the low-pressure feedwater heater 15.

The first bypass steam supply pipe 25a is provided with a high-pressure feedwater heater desuperheater 26, and steam flow rate control valves 27a, 27b are provided at the entrance to each high-pressure feedwater heater 18.
and decompression orifices 28a, 28b are provided, respectively. Similarly, the second bypass steam supply pipe 2
5b is also provided with a desuperheater 29 for the low-pressure feedwater heater, and is also provided with steam flow rate control valves 30a, 3(lD) and orifice dogs 31a, 31b for pressure reduction.

Further, a portion of the condensate discharged from the condensate pump 13 is supplied to the high-pressure feedwater heater attemperator 26 and the low-pressure feedwater heater attemperator 29 through the cooling water nupley control valve 32 .
33 as cooling water.

However, when the turbine bypass is activated, the turbine bleed air to the deaerator and feedwater heater is reduced or completely eliminated, resulting in water level fluctuations due to a drop in temperature and pressure inside the deaerator and feedwater heater. try However, each bypass steam supply pipe 25a due to the turbine bypass signal.

25b steam flow rate control valves 27a, 27b,
30a and 311b are opened, and a portion of the condensate is transferred as cooling water to the high-pressure feedwater heater attemperator 26 and the low-pressure feedwater heater attemperator 29 via the cooling water spray control valve 32°33'ft. Supplied. Therefore, part of the turbine bypass steam is reduced in temperature by the attemperators 26 and 29, and each steam flow rate adjustment 5p27a, 27b, 30a, 30
b, and each orifice canine 28a, 2
8b, 31a, 31b to a predetermined pressure and flows into each feedwater heater 18.15, thereby preventing a temperature drop and pressure drop in the feedwater heater, and at the same time, the feedwater heater drain is transferred to the deaerator 16. Since the water also flows into the deaerator 16, a drop in temperature and pressure in the deaerator 16 can be prevented, and a fluctuation in the water level in the deaerator 16 can be prevented.

In addition, the steam flow rate control valves 27 a , 27 b , 30 a , 30 are activated due to a low signal of main steam pressure, a low signal of cooling water pressure, a high signal of water supply jn heater internal pressure, etc.
b and the cooling water drop valves 30a, 30b are closed,
The supply of Pipa 3 steam to each feedwater heater is stopped.

By the way, the condensate feedwater balanne at the time when the vaipane steam is being supplied to each of the feedwater heaters mentioned above has a flow rate of steam flowing from the boiler to the condenser bypassing the turbine, Qs, and flowing into the high pressure feedwater heater side. Assuming that the steam flow rate is QIIll, the steam flow fund flowing into the low pressure feed water heater side is Q,8'', and the feed water flow rate sent to the boiler is QIB, the ratio of each flow rate is as follows when there is no turbine extraction air .

"B; Qs "s' :Q n-1:0,4:0.3
:0,3 Also, each cooling water flow rate is about 50 times the steam flow rate, so the flow rate through the condensate pump is k Q p z The flow rate through the deaerator water level control valve is Q. Assuming that I, the respective flow rate ratios are as follows.

QB: Qp: Q. ＋＝”l
: 0.6 : 0.1 With this, the deaerator,
In order to establish the inflow and outflow balanne in the condenser,
The ratio of flow rates through the condensate pump during normal operation and turbine bypass operation is: Qo=C1l, p=1:
1 Also, the flow rate ratio flowing through the deaerator water level control valve is Qo:
Qa+ = 170.17. In this way, the flow rate that can cure the condensate line during turbine bypass operation is unchanged from that during normal operation for the condensate pump, and can be set to V6 for the deaerator water level control valve. By changing the ratio of the steam flow rate flowing into the condenser and the steam flow rate flowing into the feed water heater, the condensate pump flow rate is 0.83 to 2.5 times the normal flow rate, and the deaerator water level is also increased. For control valves, it can be increased from 0 to 1.7 times.

In the above embodiment, the bypass steam supply pipe is provided with a desuperheater, but as shown in FIG. It is also possible to branch out from the downstream side.

In this case, the feed water heater side attenuators 26, 29 and the cooling water droplet control valves 32, 33 can be omitted, and the same effects as in the first embodiment can be obtained with no wasp-free equipment.

FIG. 5 is a system diagram showing an embodiment of the present invention, in which the low-pressure turbine bypass pipe 22 includes an on-off valve 34 and a deaerator-side reducer on the upstream side of the low-pressure turbine bypass valve 2. A bi-buff steam supply pipe 36 having a warmer 35 is branched out, and the tip of the bi-buff steam supply pipe 36 is connected to the deaerator 16. A part of the condensate discharged from the condensate pump 13 is supplied as cooling water to the deaerator-side desuperheater 35 via the cooling water nupure control valve 37'jk, and further deaerator The deaerator 16 is provided with a pressure nullch 38, and the on/off valve 34 is controlled to open or close based on the pressure inside the deaerator detected by the pressure switch 38.

During turbine bypass operation, when the temperature inside the deaerator decreases and the positive pressure inside the deaerator further decreases, the pressure canut 38 is activated, the on/off valve 34 is opened, and at the same time, the deaerator desuperheater 35 is activated. The cooling water 7 brake control valve 37 opens. Therefore, the Vyvanu steam whose temperature has been reduced in the deaerator-side desuperheater 35 is introduced into the deaerator 16, and a drop in the temperature inside the deaerator is prevented. The boiling phenomenon of the internally stored water is prevented, and abnormal fluctuations in the water level within the deaerator can be prevented.

On the other hand, when the internal pressure exceeds the set value or when the turbine-by type 2 operation ends, the on-off valve 34 (15) and the cooling water nubray control valve 37 close. If the main steam pressure is low or the cooling water pressure is low, the above-mentioned valves will be closed and the normal operating state will be restored.

Further, instead of the on-off valve 340, a continuous control valve based on the pressure inside the deaerator may be provided.

In this case, when the pressure inside the deaerator falls below the set value, the controller is activated due to the deviation between the detector signal and the set value, and the continuous control valve adjusts the steam flow rate to restore the pressure inside the deaerator. .

Also, during turbine bypass operation, the pressure setting value is set high.
Normally, by setting it lower, the operating conditions of the continuous control valve can be changed.

For this reason, during turbine-by-gas operation, the pressure setting value in the deaerator is raised from the normal state by the turbine-by-gas operation signal. When the bleed air runs out, the temperature inside the deaerator decreases, and the pressure inside the deaerator falls below the set value, the continuous control valve and the cooling spray control valve for the deaerator side desuperheater open, and the boiler steam flow rate decreases. (16) At the same time, by supplying steam to the deaerator, it is possible to prevent water boiling and water level fluctuations due to a drop in the pressure inside the deaerator.

In addition, since the turbine bipanu steam and cooling water are sent directly to the deaerator, the water supply flow rate can be greater than the condensate flow rate, which prevents unbalanced water supply flow rate, that is, a rise in the condenser water level and a fall in the deaerator water level. It can be prevented. Also, this eliminates insufficient capacity of the condensate pump and piping during turbine recovery. Furthermore, even when the pressure inside the deaerator is abnormally low, the pressure inside the deaerator can be restored by the by-buff steam supply pipe even when the pressure inside the deaerator is abnormally low. In this way, the pressure inside the deaerator can be controlled stably and continuously, and an abnormal drop in the internal pressure of the deaerator can be coped with even during normal operation.

Further, in the above embodiment, the bypass steam supply pipe 36
Although shown as being branched out from the upstream side of the turbine bipanu valve 21, it may be branched out from the downstream side of the desuperheater 23, as shown in FIG. In this case, the deaerator side desuperheater 35 and the cooling water drain control valve 37 can be omitted.

〔Effect of the invention〕

As explained above, in a steam turbine plant equipped with a turbine bypass device, the present invention is equipped with a bypass steam supply pipe that supplies turbine bypass valve air into a water supply line via a desuperheater. To reduce the temperature drop, pressure drop, and water level fluctuation of the feed water heater and deaerator caused by the loss of turbine bleed air during operation,
This can be prevented by introducing Vaibaku steam into the water supply line, which prevents an imbalance between condensate and water supply, prevents the condensate pump from stopping due to an abnormal drop in the condenser water level, and ultimately prevents the plant from stopping. I can do it. Moreover, since there is no need to increase the flow rate of condensate during turbine backup operation, the condensate pump can be economically designed considering only normal operation.

[Brief explanation of the drawing]

Figure 1 is a schematic system diagram of a conventional turbine plant, Figure 2 is a diagram of changes in the water level, feed water flow rate, and condensate flow rate of the deaerator and condenser during turbine bypass operation, and Figures 3 to 6 Each figure is a schematic system diagram of a steam turbine plant of the present invention. 1... Boiler, 13... Condensate pump, 14... Deaerator water level control valve, 15... Low pressure feed water heater, 16...
- Deaerator, 17... Water supply pump, 18... High pressure feed water heater, 21... Low pressure turbine bypass valve, 22...
- Low-pressure turbine bypass pipe, 25... Vaibaku steam supply pipe, 26... High-pressure feedwater heater desuperheater, 29...
Desuperheater for low pressure feed water heater, 35...deaerator side desuperheater. Applicant's agent Kiyomi Inomata 1st and 2nd

Claims (1)

[Scope of Claims] 1. In a steam turbine plant equipped with a turbine bypass device for introducing surplus steam generated in a boiler into a condenser through a turbine bath, the turbine bypass steam is passed through a desuperheater. A steam turbine plant, characterized in that it has a bypass steam supply pipe that feeds into the water supply line via a girder. 1. The steam turbine plant according to claim 1, wherein the Hibanu steam supply pipe is branched out from the downstream side of the low-pressure turbine bypass valve, and a desuperheater is provided in the middle thereof. 2. The steam turbine plant according to claim 1, wherein the steam supply pipe is branched out from the downstream side of the attemperator provided in the low-pressure turbine pipe. 4. According to any one of claims 1 to 3, the Vaibanu steam supply pipe is connected to a feed water heater, and the Vai Banu steam is supplied as feed water heating steam. steam turbine plant. 5. The steam turbine plant according to any one of claims 1 to 3, characterized in that the paivanu steam supply pipe is connected to a deaerator.