JPH0282003A - Vent system of supply water heater of power plant by steam turbine - Google Patents

Abstract

PURPOSE:To prevent the trip during the time of transition to independent operation in a power plant and reduce the cost of its construction by providing an orifice that is installed in a vent line of a supply water heater which goes from a supply water heater to deaerator with a bypass line with an orifice bypass valve. CONSTITUTION:During the transition to independent load operation in a power plant an orifice bypass valves 17a, 17b, and 17c open automatically, and the steam in supply water heaters 11a, 11b, and 11c is poured into a deaerator 4 instantaneously. When the pressure in the deaerator 4 rises with this flow of steam into it, orifice bypass valves 17a, 17b, and 17c are closed in this order from the side of a supply water heater 11a on the side of high pressure by the operation of a pressure switch 18. This eliminates the waste of discharging the steam out of the system; at the same time it is possible to prevent the generation of useless external disturbances to a system of limitation such as operation of the safety valve of the deaerator 4, etc.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a feed water heating system to a boiler of a steam turbine power generation facility, and in particular, the present invention relates to a feed water heating system for a boiler of a steam turbine power generation facility, and in particular, the present invention relates to a system for heating feed water to a boiler of a steam turbine power generation facility, and in particular, to deaeration from a feed water heater on a higher pressure side than a deaerator. Regarding the feed water heater vent system that is led to the water heater.

(Prior Art) Generally, the feed water heating equipment from the deaerator to the boiler inlet is configured as shown in FIG.

In the figure, the steam that has completed its work in steam turbine 1 is
The deaerator is introduced into the deaerator 4 through a deaerator heating steam pipe 3 equipped with a forced closure check valve 2, and the condensate introduced via the condensate pipe 5 is heated and degassed.

The degassed hot water stored in the deaerator water storage tank 6 is pressurized by a water supply booster pump 8 and a water supply pump 9 inserted into the deaerator downcomer pipe 7, and then passed through a water supply pipe 10 to a boiler (not shown). ).

In this water supply pipe 10, a feed water heater 11 is installed in order from the boiler side.
．． a, 1.1b, llc are inserted to gradually heat the hot water supplied to the boiler. The piping connecting between the feed water heaters 11a and llb, between the feed water heaters 11b and llc, and between the feed water heater 11C and the deaerator water storage tank 6 includes:
Feed water heater drain adjustment valves 12a, 12b, 12, respectively
c is inserted.

Each feed water heater 11 a, 1 l b, 11 c
and the deaerator 4.
.

Orifices 14a, 14b, and 14c for restricting the flow rate are inserted into the holes 13b and 13c, respectively.

15 indicates an atmospheric discharge pipe.

In the feedwater heating equipment configured as described above, the bleed air from the middle stage of the steam turbine 1 is passed through the bleed pipe (not shown) to the feed water heaters 11a and 11 in order from the side with the highest bleed pressure.
b, llc and used for heat exchange with the feed water passing through them.

Gas bodies such as non-condensable gases present in the extracted air of the steam turbine 1 accumulate in the upper portions of the bodies of the feedwater heaters 11a, 11b, and 11c, reducing their heat exchange efficiency and reducing the heat exchange efficiency of the feedwater heaters 11a, llb, and llc. It condenses in the water, mixes into the condensed drain, and is carried into the deaerator water storage tank 6, causing a deterioration in the quality of water supplied to the boiler.

Therefore, as described above, the feed water heaters 11a, 11b, l
Vent pipes 13a, 13b, and 13c are provided in the lc to remove noncondensable gas that has accumulated in each water heater.

Note that steam as well as non-condensable gas enters each of the vent pipes 13a, 13b, and 13c, so these vent pipes are connected to the deaerator 4, and the energy of the non-condensable gas and steam is transferred to the deaerator. The heating and degassing of the condensate flowing into the vessel 4 is effectively utilized.

The flow rate passing through the vent pipes 13a, 13b, 13c is restricted by flow rate limiting orifices 14a, 14b, 14C. By the way, these orifices 14a, 14
b, 14c limit flow rate to feed water heaters 11a, 1 l
By setting the extraction rate to about 0.5x, it is possible to obtain an effective effect in limiting the amount of non-condensable gas and steam as described above.

(Problem to be solved by the invention) By the way, if an accident occurs on the power transmission side from the generator driven by the steam turbine, the isolated load within the power plant can be operation (hereinafter referred to as PCB).

In such a case, in conventional feed water heating equipment, the steam pressure in the deaerator heating steam pipe 3 drops sharply due to a sudden decrease in turbine load, so the effective suction head of the feed water pump 9 sharply decreases transiently. Cavitation occurs in the impeller suction part (not shown) of the water supply pump 9, which not only damages the impeller of the water supply pump 9, but also causes the water supply pump 9 to trip due to a decrease in the suction pressure of the water supply pump 9, resulting in damage to the PCB.
This may result in a failure to transition to, ie, a power plant trip.

If this power plant trip occurs, it will take a long time to restart the power plant, and there is a possibility that the operating rate of the plant will decrease.

In addition, in the case of power generation equipment having an auxiliary steam system for heating the deaerator (not shown), the pressure inside the deaerator can be reduced by injecting auxiliary steam for heating the deaerator into the deaerator during the PCB described above. It is possible to suppress the power plant trip and prevent the power plant from tripping.
The disadvantage is that the equipment configuration becomes complicated.

It is an object of the present invention to provide a feed water heater vent for steam turbine power generation equipment that improves the problems of the prior art as described above and also has the effect of saving equipment.

[Structure of the Invention] (Means for Solving the Problems) The feed water heater vent of the steam turbine power generation equipment of the present invention has the following features:
In order to achieve the above objectives, a deaerator and a deaerator water storage tank, a feed water booster pump and a feed water pump that force-feed the hot water in the deaerator water tank to the boiler, and a feed water heater that heats the hot water from the feed water pump are installed. In the feedwater heating equipment, an orifice is installed in the feedwater heater vent system leading from the feedwater heater on the high pressure side to the deaerator to the deaerator to limit the vent flow rate during steady turbine load operation,
A bypass pipe equipped with an orifice bypass valve is provided as a bypass line for the orifice, and a means is provided for abruptly opening the orifice bypass valve in the event that some kind of accident occurs on the power transmission side from the generator. That is.

(Function) In the feedwater heater vent system of the steam turbine power generation equipment of the present invention having such a configuration, a bypass line is provided in the orifice provided in the vent line of the feedwater heater leading from the feedwater heater to the deaerator. Since these bypass lines are equipped with orifice bypass valves, during transition to PCB, the steam held in the feedwater heater can be released by instantly opening the orifice bypass valves, which are closed during normal operation of the turbine. It can be quickly introduced into the deaerator.

Therefore, even if the steam pressure for heating the deaerator decreases during PCB transition, the steam held in the feed water heater is rapidly injected into the deaerator, which alleviates the reduction in the deaerator. As a result, it is possible to prevent the effective suction head of the water supply pump from drastically decreasing, and it is possible to prevent a situation such as failure of transition to PCB due to a drop in suction pressure of the water supply pump, and even a trip to the power plant.

It is empirically known that a sudden drop in the effective suction head of the water supply pump during PCB transition usually occurs within about 3 minutes, and after that, the value of the effective suction head gradually increases. According to the system design of a typical thermal power plant, the steam pressure and amount of steam retained in the feedwater heater are sufficient to be used for the above purpose within the above time.

Also, during normal load operation, the steam pressure held by the high-pressure side feed water heater is more than twice the steam pressure held by the deaerator, so the steam passing through the orifice bypass valve becomes a choked flow. The flow rate necessary for the above purpose can be secured in a short time.

(Example) Next, the present invention will be described in detail with reference to FIGS. 1 and 2. In FIG. 1, the same parts as in FIG. 3 are given the same reference numerals, and explanations of overlapping parts will be omitted unless necessary.

FIG. 1 is a system diagram showing an embodiment of the feed water heater vent system of the steam turbine power generation equipment according to the present invention, in which vent pipes 13 = 1, 13b of the feed water addition parts 511a, llb, llc
, 13c are provided with orifices 14a, 14b, and 14c for limiting vent A fA during normal load operation.

Bypass pipes 16a, 16b, as bypass lines that bypass these orifices 14a, 14b, 14c,
16C, and each bypass pipe is provided with orifice bypass valves 17a, 1, each consisting of an air-operated piston valve or the like.
7b and 17c are inserted. Further, a pressure switch 18 is attached to the deaerator 4.

In the feedwater heater vent system of the present invention having such a configuration, the orifice bypass valves 17a, 17b, 17c are closed during normal load operation, and the feedwater heaters 11a, l
lb, llc vents are orifices 14a, 14b,
It is guided to the deaerator 4 via the tube 4c. The vent that has flowed into the deaerator 4 is discharged into the atmosphere via the atmosphere discharge pipe 15.

On the other hand, at the time of PCB transition, the orifice bypass valves 17a, 17b, 17c are automatically engaged by the PCB operation signal, and the steam in the feed water heaters 11a, llb, 11c is immediately injected into the deaerator 4.

FIG. 2 shows the above-mentioned orifice bypass valves 17a, 17.
The orifice bypass valves 17a, 17b, 17c are fully opened by the FCB operation signal, and steam flows in from the feed water heaters 11a11b, llc. When the internal pressure becomes extremely high, the pressure switch 18 is activated to open the orifice bypass valve 1 in order from the high-pressure feed water heater 11a side.
7a→17b→17c are closed, eliminating wasteful discharge of steam to the outside of the system, and preventing unnecessary disturbances in the restriction system due to the operation of the safety valve of the deaerator 4, etc.

[Effects of the Invention] As explained above, according to the present invention, the operation of the water supply pump can be safely continued even during PCB transition, and a power plant trip can be prevented. construction costs can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing an embodiment of the feed water heater vent system of the present invention, Fig. 2 is a schematic block diagram showing the operation of the bypass valve in the system of the present invention, and Fig. 3 is a conventional feed water heater vent system. It is a system diagram illustrating. 1... Steam turbine 2... Forced closing check valve 3... Deaerator heating steam pipe 4... Deaerator 5... Condensation pipe 6... Deaerator water storage tank 7... - Deaerator downpipe 8...Water supply booster pump 9...Water supply pump 10...Water supply pipes 11a, llb, 11cm...Water heater 12a,
12b, 12c... Feed water heater drain adjustment valve 13a, 13b, 13c... Feed water heater vent pipe 14
a, 14b, 14c...Flow rate restriction orifice 15.
... Atmospheric discharge pipes 16a, 16b, 16c... Orifice bypass pipe 1
7a, 17b, 17c... Orifice bypass valve 18
...Pressure switch agent Patent attorney Nori Chika Ken Yudo Daishimaru Kendai

Claims (1)

[Claims] Feed water heating equipment consisting of a deaerator and a deaerator water storage tank, a feed water booster pump and a feed water pump that force-feed the hot water in the deaerator water tank to the boiler, and a feed water heater that heats the hot water from the water feed pump. An orifice is provided in the feedwater heater vent system that leads from the feedwater heater on the high pressure side of the deaerator to the deaerator to limit the vent flow rate during steady turbine load operation, and this orifice is bypassed. A steam turbine characterized in that an orifice bypass pipe equipped with an orifice bypass valve is provided as a line, and a means is provided to abruptly open the orifice bypass valve in the event that some kind of accident occurs on the power transmission side from the generator. Feed water heater vent system for power generation equipment.