JP2020085287A - Drain recovery system and drain recovery method - Google Patents

Abstract

To prevent a water hammer phenomenon generated by switching a recovery destination of drain discharged from an air preheater from a deaerator to another recovery destination and elongate maintenance cycles of drain piping and its peripheral apparatuses.SOLUTION: A drain recovery system in the embodiment includes an air preheater, a drain tank, a deaerator, a distribution part, drain recovery piping and inclined piping. The air preheater discharges drain generated by preheating air of a boiler by heated steam at start of a plant. The drain tank stores drain discharged from the air preheater. The deaerator functions as one of drain recovery destinations of the drain tank. The distribution part distributes the drain in the drain tank to the deaerator or another recover destination. The drain recovery piping is provided as a drain recovery passage from the drain tank to the deaerator. The inclined piping connects an outlet of the drain recovery piping and a drain introduction port of the deaerator to the deaerator side with downward inclination.SELECTED DRAWING: Figure 1

Description

Embodiments of the present invention relate to a drain recovery system and a drain recovery method.

In thermal power generation facilities that use fossil fuels such as coal and heavy oil (hereinafter referred to as "power generation plant"), the temperature of combustion air used in the boiler is often changed by steam during startup of the power generation plant. An air preheater (also called a steam air heater) for preheating is installed.

The steam used for preheating the air in the air preheater exchanges heat by increasing the air temperature, becomes condensed water (drain), and is discharged to the outside of the air preheater system.

Since the drain generated in the air preheater has a high temperature and a large amount of it is generated, it is efficient to recover it in the boiler feed water system, which is one of the plant heat cycles.

In the plant heat cycle, it is effective to recover drainage to the deaerator, which is the equipment in the existing boiler water supply system, but the deaerator is usually installed at the top of the turbine building (above the drain tank). Therefore, the following equipment for drain collection is installed.

That is, a drain tank for primary recovery of the drain of the air preheater and a drain pump for pumping the drain of this drain tank to a deaerator through a pipe are provided, and the drain tank is drained by pressurizing the inside of the pipe with the drain pump. I try to collect it in the deaerator.

In the case of a coal-fired power plant, there are many plants that operate with heavy oil from the start of the plant to the intermediate load (when switching load to coal fuel is reached), especially when switching to coal fuel, the required air flow rate decreases, This leads to a reduction in the amount of steam, and the flow rate of drain is significantly reduced.

In this way, in an intermediate load state where fuel is switched from heavy oil to coal, a temperature reversal phenomenon occurs in which the internal temperature of the deaerator becomes higher than the drain temperature of the air preheater. A water hammer phenomenon (water hammer phenomenon) occurs due to the drain collected in.

In detail, as the drain flow rate decreases in the drain recovery pipe, a space is created in the pipe, and the vapor of the deaerator starts to flow backward to fill the space, and the low temperature of the air preheater drain Direct contact between the drain and the high temperature saturated steam inside the deaerator causes instantaneous condensation, causing the drain to move rapidly into the space inside the pipe, which is the source of the water hammer phenomenon. When the water hammer phenomenon occurs, the pipes and peripheral devices (valves, etc.) are damaged and damaged (for example, the pipes are cracked or fractured), which leads to the spouting of steam to the outside.

Japanese Patent No. 3455445 JP, 2010-48490, A

Conventionally, the drain recovery destination is switched from the deaerator to another recovery destination when an intermediate load is reached after the plant starts.At this time, the drain left in the pipe in the preceding stage of the deaerator is deaerated. Drain that mixes with the steam that flows back from the inside of the pipe rapidly moves in the space inside the pipe, and the water hammer phenomenon caused by this causes damage to the pipe and surrounding equipment (valves, etc.), There is a problem that maintenance work such as confirmation of the deterioration state of the part is required in a short cycle.

The problem to be solved by the present invention is to prevent a water hammer phenomenon caused by switching a recovery destination of drain discharged from an air preheater from a deaerator to another recovery destination, and to connect a drain pipe to the deaerator. It is to provide a drain recovery system and a drain recovery method that can prolong a maintenance cycle for equipment around and around it.

The drain recovery system of the embodiment includes an air preheater, a drain tank, a deaerator, a distribution unit, a drain recovery pipe, and an inclined pipe. The air preheater preheats the air in the boiler with heatable steam when the thermal power generation facility including the boiler is started with heavy fuel oil, thereby discharging the generated drain. The drain tank stores the drain discharged from the air preheater. The deaerator is one of the collection destinations of the drain in the drain tank. The distribution unit distributes the collection destination of the drain stored in the drain tank to the deaerator or another collection destination. The drain recovery pipe is provided as a drain recovery path between the drain tank and the deaerator. The inclined pipe connects the outlet of the drain recovery pipe and the drain introduction port of the deaerator to the deaerator side with a downward slope.

It is a figure which shows the structure of the air preheater drain recovery system in the thermal power plant of 1st Embodiment. It is a graph which shows the change timing by the measurement data in each measurement point. It is a figure which shows the structure of the air preheater drain recovery system in the thermal power plant of 2nd Embodiment.

Hereinafter, embodiments will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram showing a thermal power plant according to one embodiment including a drain recovery system.

The thermal power plant according to the first embodiment includes, as main equipment, an air preheater drain recovery system in addition to main equipment such as a boiler, a turbine, and a generator.

As shown in FIG. 1, the air preheater drain recovery system includes, for example, a steam type air preheater 1, a drain tank 9, a drain pump 11, a deaerator 20, and a pipe connecting these devices (air preheater drain pipe 8). , Drain pipe 16, drain water-filled pipe 22, etc.), detectors (detectors 4, 14, 24, 25, etc. for air temperature, steam temperature, water level, etc.) provided in each device, and these detectors and signal lines. The control device 15 is connected by.

The air preheater 1 preheats the air supplied to the boiler by exchanging heat between the air supplied to the boiler and the steam extracted from the turbine.

The air temperature detector 4 is installed in the air preheater outlet air duct 3. The air temperature detector 4 detects the temperature of the air preheater 1. The water level detector 14 detects the water level of the drain tank 9. The drain temperature detector 24 is provided in the pipe connected to the outlet of the drain tank 9. The drain temperature detector 24 detects the temperature of the drain of the drain tank 9. The deaerator temperature detector 25 detects the temperature of the deaerator.

The air preheater drain pipe 8 is a flow path for sending the drain from the air preheater 1 to the drain tank 9. The drain tank 9 collects the drain generated in the air preheater 1 through the air preheater drain pipe 8 and stores the primary water. The drain tank vent valve 10 discharges drain from the drain tank 9 to the outside under control.

The drain pump 11 discharges the drain stored in the drain tank 9 from the drain tank 9. The drain discharged from the drain tank 9 is sent to the plant heat cycle equipment (the deaerator 20 or other recovery destination 30) by the drain pump 11 and is recovered as water to be used in the plant heat cycle equipment. That is, the deaerator 20 or other recovery destination 30 is one of the drain recovery destinations of the drain tank 9.

The pump recirculation system 12 protects the minimum flow rate of the drain pump 11 by returning a part of the drain sent from the drain pump 11 to the drain tank 9 and circulating it. The pump recirculation system 12 includes pipes and valves.

The drain check valve 13 is a check valve for preventing the drain from flowing backward from the drain pipe 16 side to the drain pump 11 when the pump is stopped. The condensate check valve 29 is a check valve for preventing drain from flowing back to the condensate pipe 21.

The drain pipe 16 is a drain flow path for guiding the drain sent from the drain tank 9 by the drain pump 11 and passing through the check valve 13 to the deaerator 20 side.
The deaerator recovery adjustment valve 17 adjusts the drainage amount discharged from the drain tank 9 by changing the flow rate opening of the adjustment valve according to the control signal output from the control device 15. The deaerator recovery adjustment valve front valve 18 is an electrically operated valve that is provided in front of the deaerator recovery adjustment valve 17.

The drain water filling pipe 22 is connected to the deaerator recovery control valve 17, the deaerator recovery adjustment valve front valve 18, the drain pipe 19a immediately before the deaerator, and the condensate pipe 21 to connect the flow path (the drain pipe 16) near the deaerator 20. Fill with water.

The drain tank water level control valve 23 and the deaerator recovery control valve 17 control the flow of drain to the deaerator 20 or a recovery destination 30 other than the deaerator 20 according to a control signal output from the control device 15. Switch. That is, the drain tank water level control valve 23, the deaerator recovery control valve 17, and the like function as a distribution unit that distributes the drain recovery destination to the deaerator 20 or another recovery destination 30.

A drain recovery pipe 19 which is a drain recovery path connecting the drain water filling pipe 22 and the deaerator 20 is provided with a deaerator recovery control valve 17 and a deaerator recovery adjustment valve front valve 18 which is a front valve thereof. ing. The drain pipe 19a immediately before the deaerator is a part of the drain recovery pipe 19 and is a pipe portion leading to the deaerator 20 after the deaerator recovery control valve 17. The deaerator recovery adjustment valve front valve 18 is an electric valve.

The drain pipe 19a immediately before the deaerator is not a horizontal pipe or a vertical pipe, but is a tilt pipe installed in a range where the inclination angle of the downward gradient is 30° or more and less than 70° with respect to the horizontal direction. Depending on the positional relationship (height difference) between the drain water-filled pipe 22 and the drain introduction port 20a of the deaerator 20, if the height difference is large, for example, the installation angle of the drain pipe 19a immediately before the deaerator is set to the horizontal direction. Alternatively, the range may be 45° or more and less than 75°. Although the installation angle has been described based on the horizontal direction, it may be based on the vertical direction.

That is, the drain pipe 19a immediately before the deaerator is installed such that the range of the inclination angle thereof is 45 degrees or more and less than 75 degrees or 30 degrees or more and less than 70 degrees with respect to the horizontal direction. When the ranges of the two inclination angles are combined, it can be said that the inclination angle is preferably in the range of 30° or more and less than 75° with respect to the horizontal direction with a downward slope toward the deaerator 20 side.

By installing the drain pipe 19a immediately before the deaerator within such an inclination angle range, the drain remaining in the pipe after the deaerator recovery control valve 17 is removed by the deaerator before the vapor condensation phenomenon occurs. The whole amount can be collected by pouring into 20.

At this time, the drain remaining in the pipe flows down at the bottom of the pipe, and the saturated vapor flowing back from the deaerator 20 travels up the upper part of the pipe, so that they are replaced without being mixed with each other. The vapor condensation phenomenon due to the reverse flow of vapor in the drain recovery pipe 19 will not occur.

The control device 15 controls each device according to the detection value detected by each detector. Specifically, at plant startup, the controller 15 monitors the air temperature detected by the air temperature detector 4, and controls the air preheater 1 when the air temperature is lower than a preset temperature. Preheat the air with steam to raise the temperature of the air. At this time, the air preheater 1 discharges the condensed water (drain) generated by the steam to the drain tank 9 through the drain pipe 8.

Further, the control device 15 monitors the water level of the drain tank 9 detected by the water level detector 14, and controls the drain pump 11 according to the change (rise or fall) of the water level to adjust the drainage amount of the drain tank 9. .. At this time, when the water level (drain storage amount) of the drain tank 9 exceeds a certain value, the drain tank water level control valve is adjusted according to the plant load and the temperature of the air preheater 1, the drain tank 9, the deaerator 20, etc. 23 and the deaerator recovery control valve 17 are controlled to distribute the drainage to the deaerator 20 or another recovery destination 30 and recover it as water used in the plant heat cycle facility.

For example, the controller 15 monitors the temperature of the air preheater 1 or the drain tank 9 and the temperature of the deaerator 20 while the plant load is increasing after the plant is started, and before the temperature reversal phenomenon occurs between them. The drain tank water level control valve 23 and the deaerator recovery control valve 17 are controlled to distribute the drain collected in the deaerator 20 to another recovery destination 30. At this time, the control device 15 opens the drain tank water level control valve 23 and closes the deaerator recovery control valve 17.

Next, the operation of this thermal power plant will be described with reference to the graph of FIG. In the graph of FIG. 2, reference numeral 31 is the drain temperature of the air preheater 1, reference numeral 32 is the heavy oil usage amount, reference numeral 33 is the plant load, reference numeral 34 is the inside temperature of the deaerator 20, and reference numeral 35 is the coal usage amount. 36 is a drain recovery switching point, and 37 is a water hammer generation area.
When starting the thermal power plant, heavy oil is used as the fuel for the boiler, so heavy oil is used to raise the temperature of the air from the atmospheric temperature in the steam type air preheater 1. At this time, since the heat source used to raise the temperature of the air is steam, a large amount of drain is generated when the thermal power plant is started, and the pressure inside the air preheater 1 also rises.

Since the drain generated in the air preheater 1 reaches the saturation temperature of the air preheater 1, the high temperature drain flows into the drain tank 9. At this time, since the thermal power plant is a bear just started, the temperature inside the deaerator 20 (internal temperature) is 100° C. or lower.

Then, when the plant load (power generation load) 33 is increased, as shown in FIG. 2, the amount of heavy oil used 32 increases, the amount of steam consumed in the air preheater 1 also increases, and the generated drain amount also increases. However, when the plant load (power generation load) 33 rises as it is and it is time to switch from heavy oil fuel to coal fuel, the usage amount 32 of heavy oil decreases. Along with this, the amount of steam consumed decreases, the amount of drain generated decreases, and the drain temperature 31 of the air preheater 1 also decreases.

However, due to the increase in the plant load 33, when the plant load 33 is an intermediate load of about 50%, for example, the internal temperature 34 of the deaerator 20 has already exceeded 200° C. At the timing of switching between the fuel and the coal fuel, a reverse phenomenon occurs between the drain temperature 31 of the air preheater 1 and the internal temperature 34 of the deaerator 20.

Therefore, in the thermal power plant according to the first embodiment, the controller 15 controls the internal temperature of the deaerator 20 detected by the deaerator temperature detector 25 and the drain tank detected by the drain temperature detector 24. When the drain recovery switching point 36 (see FIG. 2) before the mutual temperatures are reversed (reversed) is being monitored while monitoring the temperature of the drain 9 of FIG. 9, the controller 15 is attached to the drain recovery branch pipe 26. By controlling the drain tank water level control valve 23 and the deaerator recovery control valve 17, the drain flow (drain recovery destination) is switched from the deaerator 20 to another recovery destination 30 (the drain recovery branch pipe 26 side). ..

More specifically, the control device 15 controls the drain tank water level control valve 23 to open and the deaerator recovery control valve 17 to close. The time before the temperature of the deaerator 20 and the temperature of the drain tank 9 reverse is also referred to as, for example, immediately before reaching the reversing timing or approaching the reversing timing.

As a result, the collection of the drain to the deaerator 20 is stopped, and the drain of the drain tank 9 is drained from the drain pump 11, the drain check valve 13, the drain recovery branch pipe 26, and the drain tank water level control valve 23 to another drain. It will be collected in the collection destination 30.

On the deaerator 20 side, the deaerator recovery control valve 17 is closed and the collection of drain to the deaerator 20 is stopped, so that the deaerator recovery control valve 17 reaches the deaerator 20. The drain remaining in the drain recovery pipe 19 flows to the deaerator 20 through the drain pipe 19a immediately before the deaerator having a downward slope, and the deaerator 20 collects the entire amount of the drain.

Therefore, even if the saturated vapor of the deaerator 20 flows back to the drain pipe 19a immediately before the deaerator, the residual drain does not mix with each other, and vapor condensation does not occur. Therefore, in the water hammer generation area 37 (see FIG. 2). , The water hammer phenomenon does not occur. In addition, the deaerator recovery control valve 17 and the deaerator recovery control valve front valve in the preceding stage thereof are arranged so that the drain does not remain in the pipe from the position of the deaerator recovery control valve 17 to the drain pipe 19a immediately before the deaerator. By using valves such as 18 as a ball valve or a gate valve, drain does not remain at a mechanical step of the valve, and vapor condensation at that portion can be eliminated.

As described above, according to the thermal power plant of the first embodiment, the drain pipe 19a immediately before the deaerator is arranged with a downward slope, and after the plant is started, the control device 15 detects the air detected by the drain temperature detector 24. Deaeration detected by the deaerator temperature detector 25 when the preheater drain temperature and the deaerator temperature detected by the deaerator temperature detector 25 are monitored, and when switching from crude oil fuel to coal fuel due to load increase When the temperature of the vessel and the temperature of the drain detected by the drain temperature detector 24 reach the drain recovery switching point 36 before reversing, the drain tank water level control valve 23 attached to the drain recovery branch pipe 26 is controlled. Then, by switching the drain recovery destination from the deaerator 20 to another recovery destination 30, the collection of the drain to the deaerator 20 is stopped, and at the time of the recovery stop, the flow path in the preceding stage of the deaerator 20 ( All the drain remaining in the drain recovery pipe 19) is recovered in the deaerator 20 through the descending slope immediately preceding the deaerator drain pipe 19a. Therefore, the water hammer phenomenon does not occur even if the steam backflow occurs in the drain pipe 19a immediately before the deaerator after the deaerator recovery control valve 17 (before the deaerator 20), and as a result, immediately before the deaerator. It is possible to delay the deterioration of the drain pipe 19a and the devices (valves and the like) around the drain pipe 19a and prolong the maintenance period.

Further, the drain pipe 19a immediately before the deaerator is not vertical but has a downward slope toward the deaerator 20 and an angle of inclination of 45° or more and less than 75° with respect to the horizontal direction, or 30° or more and less than 70° In this case, before the vapor condensation phenomenon occurs, the drain remaining in the pipe after the deaerator recovery control valve 17 is flown to the deaerator 20 to recover the whole amount, and the reverse flow from the deaerator 20 is performed. Since the saturated steam coming in is replaced, the steam condensation phenomenon due to the reverse flow of steam in the drain recovery pipe 19 does not occur. When the above range of the inclination angle is summed up, it can be said that the inclination angle is preferably in the range of 30° or more and less than 75° with respect to the horizontal direction with a downward slope toward the deaerator 20.

As a result, it is possible to prevent the occurrence of the water hammer phenomenon that occurs in the drain recovery pipe 19 including the deaerator immediately preceding drain pipe 19a after the deaerator recovery control valve 17. As a result, the deaerator recovery control valve 17 and the like attached to the drain recovery pipe 19 are prevented from being deteriorated or damaged, and the drain recovery pipe 19 is prevented from cracking or rupturing. It is possible to prevent the situation in which steam spouts outside.

Although the drain temperature of the air preheater 1 and the internal temperature of the deaerator 20 are compared in the above embodiment, the drain temperature of the drain tank 9 may be used instead of the drain temperature of the air preheater 1. Good.

Further, in the above-described embodiment, an example in which the deaerator recovery control valve front valve 18 and the like provided in front of the deaerator recovery control valve 17 of the drain recovery pipe 19 (horizontal pipe) are ball valves or gate valves has been described. However, even when a rear valve is provided behind the deaerator recovery control valve 17, it is better to use a ball valve or a gate valve thereafter.

(Second embodiment)
FIG. 3 is a diagram showing the configuration of the air preheater drain recovery system of the second embodiment. In describing the second embodiment, the same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 3, in the air preheater drain recovery system of the second embodiment, the deaerator recovery adjustment is performed in the drain recovery pipe 19 which is a drain recovery path connecting the drain water filling pipe 22 and the deaerator 20. Immediately before the deaerator, the drain pipe 19a immediately before the deaerator, which is an inclined pipe connected to the valve 17, is provided with a post-deaerator recovery control valve valve 27, and branches before the deaerator recovery control valve front valve 18. A bypass pipe 31 connected to the drain pipe 19a is provided with a deaerator recovery control valve bypass valve 28. The deaerator recovery control valve front valve 18 does not have to be an electrically operated valve.

In this case, the valves (such as the deaerator recovery control valve rear valve 27) provided in the deaerator immediately preceding drain pipe 19a after the deaerator recovery control valve 17 are ball valves or gate valves. By using a ball valve or a gate valve for the valves provided in the drain pipe 19a immediately before the deaerator, which is an inclined pipe, the drain is prevented from remaining in the valve itself due to the structure of the valve, and vapor condensation at that portion is prevented. It can be lost. As the valves, in addition to the deaerator recovery control valve rear valve 27, the deaerator recovery control valve bypass valve 28 and the deaerator recovery control valve front valve 18 that is the front valve of the deaerator recovery control valve 17 and A stop valve (not shown) or the like may be a ball valve or a gate valve.

According to the air preheater drain recovery system of the second embodiment, similar to the first embodiment, the drain temperature of the air preheater 1 and the internal temperature of the deaerator 20 are reversed (at the reversal point). When approaching), the drain tank water level control valve 23 and the deaerator recovery control valve 17 are controlled to switch the drain recovery destination from the deaerator 20 to the drain recovery branch pipe 26 side. Replacing the drain remaining between the deaerator recovery control valve 17 and the deaerator 20 with the saturated vapor flowing back from the deaerator 20 by stopping the drain recovery and stopping the drain recovery Is performed by the drain pipe 19a immediately before the deaerator having a slope of 45° or more and less than 75°, so that the residual drain of the drain recovery pipe 19 is transferred to the deaerator 20 before the vapor condensation phenomenon occurs. All can be collected.

Further, by using a ball valve or a gate valve for the valves (such as the deaerator recovery control valve rear valve 27) installed in the inclined deaerator immediately preceding drain pipe 19a, the drain does not remain in the valve itself.

Therefore, it is possible to prevent the occurrence of a water hammer that occurs in the drain recovery pipe 19 (including the drain pipe immediately before the deaerator) after the deaerator recovery control valve 17. This prevents damage to the deaerator recovery control valve 17 and the deaerator recovery control valve rear valve 27 attached to the drain recovery pipe 19, and eventually prevents the drain recovery pipe 19 from cracking or breaking. It is possible to prevent a situation in which steam is spouted from the inside.

That is, according to the present invention, the water hammer phenomenon caused by switching the recovery destination of the drain discharged from the air preheater 1 from the deaerator 20 to the other recovery destination 30 is prevented, and the drain recovery pipe 19 ( The maintenance cycle for the drain pipe 19a immediately before the deaerator and the devices (valves and the like) around the drain pipe 19a can be extended.

In the first embodiment, as in the second embodiment, the deaerator recovery control valve 17 of the drain recovery pipe 19 and valves provided in the flow path in the vicinity thereof (the deaerator recovery control valve front valve 18, etc.). ) May be a ball valve or a gate valve.

Further, in the first embodiment, the control device 15 monitors the drain temperature of the air preheater 1 and the internal temperature of the deaerator 20, and switches the drain recovery destination before the temperatures of the two are reversed. However, in addition to this, for example, in addition to the deaerator 20, in the thermal power generation plant having a condenser or a recovery destination in the plant cycle corresponding to the condenser, or a system for switching to the outside of the plant cycle system, the drain recovery destination is switched. In addition, the drain recovery destination may be switched using not only the temperature difference but also alternative information such as the plant load, the steam temperature, and the amount of heavy oil that can predict the drain temperature difference.

Although the embodiment of the present invention has been described, this embodiment is presented as an example and is not intended to limit the scope of the invention. The novel embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the scope equivalent thereto.

Further, each component of the control device 15 shown in the above embodiment may be realized by a program installed in a storage such as a hard disk device of a computer, and the above program may be stored in a computer-readable electronic medium: electronic media. Alternatively, the computer may realize the functions of the present invention by causing the computer to read the program from the electronic medium.

Examples of the electronic medium include a recording medium such as a CD-ROM, a flash memory, and a removable medium: Removable media. Further, it may be realized by distributing and storing the constituent elements in different computers connected via a network, and communicating between the computers operating the respective constituent elements.

1...Air preheater, 3...Air preheater outlet air duct, 4...Air temperature detector, 8...Air preheater drain pipe, 9...Drain tank, 10...Drain tank vent valve, 11...Drain pump, 12...Pump Recirculation system, 13... Drain check valve, 14... Water level detector, 15... Control device, 16... Drain pipe, 17... Deaerator recovery control valve, 17... Drain recovery control valve, 18... Deaerator recovery adjustment Valve front valve, 19... Drain collection pipe, 19a... Drain pipe immediately before deaerator, 20... Deaerator, 20a... Drain introduction port, 21... Condensate pipe, 22... Water filling pipe, 23... Drain tank water level control valve, 24... Drain temperature detector, 25... Deaerator temperature detector, 26... Drain recovery branch pipe, 27... Deaerator recovery control valve rear valve, 28... Deaerator recovery control valve bypass valve, 29... Condensate reverse Stop valve, 30... Other recovery destination, 31... Bypass piping.

Claims (5)

An air preheater that discharges the generated drain by preheating the air of the boiler when starting a thermal power generation facility including a boiler with heavy oil fuel,
A drain tank for storing the drain discharged from the air preheater;
A deaerator that is one of the drain recovery destinations of the drain tank,
Depending on the load of the thermal power generation facility, a distribution unit that distributes the collection destination of the drain stored in the drain tank to the deaerator or another collection destination,
A drain recovery pipe provided as a drain recovery path between the drain tank and the deaerator,
A drain recovery system, comprising: an inclined pipe connecting an outlet of the drain recovery pipe and a drain introduction port of the deaerator to the deaerator side with a downward slope. The drain recovery system according to claim 1, wherein an inclination angle of the inclined pipe is in a range of 30 degrees or more and less than 75 degrees with respect to a horizontal direction. A first temperature detector for detecting the temperature of the air preheater or the drain tank;
A second temperature detector for detecting the temperature of the deaerator,
While increasing the load after starting the thermal power generation facility, the first temperature detector and the second temperature detector are monitored, and when switching from heavy oil fuel to coal fuel with load increase, Before the temperature of the air preheater or the drain tank detected by the first temperature detector exceeds the temperature of the deaerator detected by the second temperature detector, the recovery destination of the drain is degassed. The drain recovery system according to claim 1, further comprising a control unit that controls the distribution unit so as to switch from the container to another recovery destination. The valve is a ball valve or a gate valve when a valve is provided in the drain recovery pipe or a bypass pipe branched from the drain recovery pipe and connected to the inclined pipe. The drain recovery system described in the item. When starting the thermal power generation equipment including the boiler with heavy fuel oil, the air preheater discharges the drain generated by preheating the air of the boiler with heated steam,
The drain discharged from the air preheater is stored in a drain tank,
Sorting to the deaerator, which is one of the drain recovery destinations of the drain tank,
With the load increase of the thermal power generation facility, when switching from heavy oil fuel to coal fuel, before the temperature of the deaerator exceeds the temperature of the air preheater or the drain tank, the drain tank and the deaerator The drain recovery control valve of the drain recovery pipe provided between the control unit and the drain recovery destination is distributed from the deaerator to another recovery destination,
The drain remaining in the drain recovery pipe on the deaerator side, through an inclined pipe connecting the outlet of the drain recovery pipe and the drain introduction port of the deaerator to the deaerator side with a downward slope, Drain recovery method to recover to the deaerator.

Images