JPS62106207A - Feedwater supply system in 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 water supply system in a steam turbine plant, and more particularly to a water supply system that can stabilize the operation of condensate equipment in the event of an abnormality in drain equipment. .

(Technical disadvantages and problems with the invention) Generally, in a steam turbine plant, a large number of feed water heaters are installed to improve plant efficiency, and the steam extracted from the middle stage of the steam turbine indirectly supplies condensate. Heating is being done. On the other hand, the condensate condensed through heat exchange with the feed water in the feed water heater is sequentially collected in the feed water heater on the low pressure side, and then partially collected in a drain tank to improve thermal efficiency. A method of heating condensate by directly injecting it into the water has recently been adopted.

In other words, FIG. 3 is a schematic system diagram of a conventional steam turbine plant, in which steam generated in a steam generator 1 is sequentially fed to a high-pressure turbine 2 and a low-pressure turbine 3, and each turbine performs work as shown in the figure. Do not drive the generator. By the way, the steam that has worked in the low-pressure turbine 3 is condensed in a condenser 4, passed through a condensate pump 5 and a condensate purification device 6, and is sequentially sent to a plurality of feed water heaters 7a, 7b, 7cl, etc. be done. The above feed water heating iW7 a, 7 b,
7c, the extracted air extracted from the low-pressure turbine 3 or the high-pressure turbine 2 is supplied as heated steam, and exchanges heat with the condensate that sequentially flows through each feedwater heater 7a, 7b, and 7c. Heating takes place. The condensate heated by each of the feed water heaters 7a, 7b, and 7c is pressurized by the feed water pump 8 and then returned to the steam generator 1.

On the other hand, the steam that has exchanged heat with the C condensate in each of the feed water heaters 7a, 7b, and 7c is condensed there and becomes drain, and this drain is sequentially collected in the feed water heater on the low pressure side, and finally in the drain tank 9. After being collected, drain pump 10
It is directly injected into the condensate fed by the condensate pump 5 on the downstream side of the condensate purification device 6.

Thus, in such an installation, the thermal efficiency is considerably improved because condensate, which is hotter than the condensate, is injected into the condensate on the -L flow side of the feedwater heater.

However, in general, the condensate generated in the feed water heater accounts for tens of percent of the water supplied to the steam generator, and in the case of nuclear power plants in particular, the condensate flow rate exceeds the condensation rate in the condenser. The darkness is almost the same as the amount of condensed water. Therefore, if an abnormality occurs in the drain pump or the like and the amount of water injected into the condensate 61 decreases or becomes O, this will directly affect the amount of water supplied, and the steam generator 1 will be seriously affected. There are problems such as having a serious impact on the operation of the turbine plant itself, and causing a major hindrance to the continued stable operation of the plant.

[Purpose of the invention]

In view of these points, the present invention minimizes the impact on the water supply system even if an abnormality occurs in the drain system, makes it possible to secure the water supply to the steam generator, and improves the reliability of the turbine plant. The purpose is to obtain a water supply device that can.

[Summary of the invention]

The present invention supplies oil and gas extracted from a steam turbine to a feedwater heater, which heats the feedwater to the steam generator, and also supplies drain generated in the feedwater heater to the feedwater heater using a condensate pump. In a water supply system for a steam turbine plant that allows the drain to flow directly into the feed water supplied to the drain tank, a plurality of drain pumps connected in parallel are used to prevent the drain from flowing into the feed water, and to connect the drain tank to the drain tank. An overflow drain line is provided between the water tank and the condensate pump, and the condensate pump is configured with a plurality of condensate pumps connected in parallel, and the entire water supply capacity is transferred to the condenser during rated operation of the plant. It is characterized by a flow rate that is greater than the sum of the inflow flow rate and the amount of water sent by one drain pump, and in the event that a part of the drain pump malfunctions, the remainder of the drain is returned to the condenser and This IC is designed to increase the time between water supply by the condensate pump and minimize fluctuations in the flow rate of water supplied to the steam generator.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. Note that the same parts as in FIG. 3 are denoted by the same reference numerals, and detailed explanation thereof will be omitted.

In FIG. 1, the drain tank 9 includes two drain pumps 10a, each having a capacity capable of handling 50% of the drain during rated plant operation, and arranged in parallel with each other.
10b is connected, and its drain pumps 10a, 1
The discharge side of 0b is connected via a drain pipe 11 to a water supply pipe upstream of the feed water heater 7a. The drain pipe 11 is provided with a water level regulating valve 13 whose opening degree is controlled by a detection signal from the water level detector 12 of the drain tank 9, and a drain flow rate detector 14 is provided downstream of the water level regulating valve 13. It has been set up. Further, an overflow drain line 15 is connected to the drain tank 9 to return excess drain to the condenser 4.

On the other hand, immediately downstream of the condenser 4, a plurality of (three in the figure) condensate pumps 5a, 5b, 5 are connected in parallel to each other.
c is provided. These condensate pumps 5a, 5b, 5c
The total water supply capacity of the plant is such that it is equal to or greater than the sum of the flow rate flowing into the condenser and the water supply of one drain pump during rated operation of the plant.

In other words, a condensate pump normally has a discharge rate of 120% or more of its rated capacity, while in the case of a nuclear power plant, the maximum condensate flow rate is about 40% of the water supplied to the steam generator 1.
Since it is about 7%, the condensate pumps 5a, 5b, 5c
The sum of the rated capacities of the condensate pumps 5a and 5b is set to be about 120% of the inflow amount to the condenser 4 during rated plant operation, and the condensate pumps 5a, 5b are further controlled by the detection signal from the drain flow rate detector 14. , 5c is adjusted.

Therefore, during normal operation of the plant, the drain generated in the feed water heaters 7a, 7b, and 7c and flowing into the drain tank 9 is pumped to the drain pump 10a.

10b into the water supply pipe on the inlet side of the feed water heater 7a, and the condensate pumps 5a, 5b.

5C, and the mixed flow is sent to the steam generator 1 via the feedwater heater.

By the way, during the operation of the plant, the drain pump 10a
, if one of 10b has an abnormality and stops,
The detection signal from the drain flow rate detector 14 controls the condensate pump so that the discharge exceeds its rated capacity, and the decrease in the drain flow supplied from the drain pump is covered by the increase in the discharge amount by the condensate pump. , the water supply to the steam generator is secured. On the other hand, at this time, the excess drain in the tank 9 is sent to the condenser 4 via the bypass drain line 15, and joins with the water stored in the hot well installed at the bottom of the condenser 4. It can adequately handle the flow rate pumped by the water pump.

In this way, even in the event of an abnormality in the drain system such as a failure of the drain pump, there is almost no effect on the water supply system, and a sufficient water supply to the steam generator is ensured.

By the way, the drain ■ flowing into the drain tank 9 is
As shown in the figure, it increases or decreases in proportion to the plant output. Therefore, when detecting and transmitting an abnormality in the drain system using the drain flow rate detector 14, the old value of the drain is set in advance in comparison with the plant output, and when the difference from this set value exceeds the allowable value, an abnormality occurs. By doing so, prompt control is possible regardless of factors such as the number of drain pumps in operation or an abnormality in the water level control valve 13. Also, for example, if plant operation suddenly shifts to partial load due to some reason, control can be performed quickly. There is no risk of erroneous control even if there is a problem.

Note that as a plant output signal, there are methods that rely on the output of the generator, the pressure of the turbine first stage nozzle box, the back air pressure of the high-pressure turbine, etc., but it is also possible to use changes in the flow rate of water sent to the steam generator. It is also possible by Also,
Even if the rate of change of the flow 1 detector changes suddenly, this is due to an abnormality in the drain system, except when the plant operating state suddenly shifts to partial load.The present invention can also be achieved by controlling the rate of change. The effect remains intact. In this case, a sudden change in the plant operating state due to the output of the generator, the pressure of the turbine first stage nozzle box, the back pressure of the high pressure turbine, etc. is detected, and the drain flow is detected. By preventing the transmission of false alarms 8 from the equipment, it becomes possible to continue stable operation of the plant.

By the way, if the condensate purification device 6 (desalination device) installed to deal with seawater leakage from the condenser 4 is unable to treat the condensate of human body compared to the rated operation of the plant, A bypass pipe line 17 having a bypass valve 16 is connected to the condensate purification device 6, and the drain flow rate detector 1
By opening the bypass valve 16 in response to a signal from the steam generator 4, it is possible to secure the time between water supply to the steam generator 1.

In addition, in order to protect the condenser 4 from seawater leakage by chance, a salinity meter 18 is provided at the outlet of the condenser 4, and a signal from the salinity meter 18 is used to operate the bypass valve. Prevent 16 from listening.

Furthermore, by installing a backup pump in the condensate pump, the drain flow can be automatically activated in response to a signal from the detector 14, thereby ensuring a period of water supply to the steam generator.

[Summary of the invention]

Since the present invention is constructed as described above, the feed water heater drain equipment can be constructed without any loss of the effect of the prior art, which is to directly inject the drain of the feed water heater into the condensate to significantly improve thermal efficiency. Even during normal operation, water can be continuously supplied to the steam generator without significantly affecting the water supply, and a highly reliable steam turbine plant can be achieved.

[Brief explanation of drawings]

FIG. 1 is a schematic system diagram of the water supply system of the present invention, FIG. 2 is a diagram showing the relationship between drain flow rate and plant operating status, and FIG. 3 is a schematic system diagram of a conventional steam turbine plant. 1... Steam generator, 4... Condenser, 5a, 5b. 5C... Condensate pump, 6... Condensate purification device, 7a,
7b, 7c... Water supply heater, 9... Drain tank,
10a, 10b...Drain pump, 14...Drain flow rate detection each, 15...Overflow drain line. Applicant's agent Mr. Sato Figure 1

Claims (1)

[Claims] 1. The extracted air extracted from the steam turbine is supplied to the feedwater heater, where the feedwater to the steam generator is heated, and the condensate generated in the feedwater heater is transferred to the In a water supply system in a steam turbine plant that allows the drain water to directly flow into the feed water supplied to the feed water heater, a plurality of drain pumps connected in parallel are used to cause the drain water to flow directly into the feed water, and An overflow drain line is provided between the tank and the condenser, and the condensate pump is configured by a plurality of condensate pumps connected in parallel, and the total water supply capacity is
A water supply system for a steam turbine plant, characterized in that the flow rate is greater than or equal to the sum of the flow rate flowing into a condenser during rated operation of the plant and the water flow rate of one drain pump. 2. A water supply system for a steam turbine plant according to claim 1, characterized in that two common drain pumps are connected in parallel to each other. 3. 5 of the flow rate flowing into the condenser during rated operation of the plant
The water supply system for a steam turbine plant according to claim 1, characterized in that two or more condensate pumps having a capacity exceeding 0% are connected in parallel to each other. 4. The steam according to claim 1, wherein one of the plurality of condensate pumps is a spare pump, and the spare condensate pump is automatically started in the event of an abnormality in the drain system. Water supply equipment in turbine plants.