JPH11159702A - Method for controlling emergency of boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it unnecessary to set heating-up time longer and prevent abnormal increase in the temperature of piping of heat transfer device. SOLUTION: When troubles of fuel system or auxiliary machines occur, the supply of fuel to a burner is stopped and the inflow quantity of heat to a furnace is blocked instantaneously. In such an emergency stop of boiler, when a high-pressure turbine 19 is stopped and the steam inflow to the high-pressure turbine 19 is blocked, the bypass valve 18 of high-pressure turbine is closed, and main steam pressure is measured by a manometer 26 and the bypass valve 17 of superheater is made open if the main steam pressure exceeds the set value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an emergency stop control method for urgently stopping a boiler such as a variable-pressure once-through boiler.

[0002]

2. Description of the Related Art FIG. 2 is a schematic view showing a variable-pressure once-through boiler, and FIG. As shown in the figure, a furnace 35 is formed surrounded by a furnace water cooling wall 2, a burner 16 is disposed on the furnace water cooling wall 2 below the vicinity of the center of the furnace 35, and a duct 3 is provided in the furnace 35.
A rear wall 15 formed of a casing is connected to the rear wall 15 via the first wall. A suspended primary superheater 8 is installed above the furnace 35, and the duct 3
A suspended secondary superheater 9, a suspended tertiary superheater 10, and a suspended reheater 13 are installed toward zero. The rear wall 15 is divided into a reheater side and a superheater side, and a horizontal reheater 12 is installed on the rear wall 15 on the reheater side, and is horizontally mounted on the rear wall 15 on the superheater side. The superheater 7, the evaporator 3, and the economizer 1 are installed, and a gas distribution damper 36 is provided at an outlet of the rear wall 15. In addition, the water saving pump 1, the furnace water cooling wall 2, and the evaporator 3 are connected to the feed water pump 21, the brackish water separator 4 is connected to the evaporator 3, the brackish water separator drain tank 5 is connected to the brackish water separator 4, A steam separator drain tank 5 is connected to the economizer 1 via a boiler recirculation pump 6. In addition, a horizontal superheater 7, a suspended primary superheater 8, a suspended secondary superheater 9, and a suspended tertiary superheater 10 are placed on the brackish water separator 4.
And a high-pressure turbine 19 is connected to the suspended tertiary superheater 10 via the main steam pipe 11.
, A horizontal reheater 12 is connected to the high-pressure turbine 19, and an outlet of the suspended primary superheater 8 is connected to the condenser through a superheater bypass line 22. 20 and a superheater bypass line 22
The main steam pipe 11 and the condenser 20 are connected via a high-pressure turbine bypass line 23, and the high-pressure turbine bypass line 23 is provided with a high-pressure turbine bypass valve 18.

In this variable-pressure once-through boiler, the burner 1
The exhaust gas generated from 6 flows first to the suspended primary superheater 8 installed at the upper part of the furnace 35. The exhaust gas temperature at this time is about 500 ° C. at the time of startup, and is about 1200 ° C. at a rated load. Thereafter, the exhaust gas passes through the suspended secondary superheater 9, the suspended tertiary superheater 10, and the suspended reheater 13, is absorbed, and the exhaust gas temperature gradually decreases. By opening and closing the gas distribution damper 36, the exhaust gas flow flowing to the reheater side and the superheater side of the rear wall 15 is distributed. At the reheater side of the rear wall 15, heat is absorbed by the horizontal reheater 12 and The steam temperature at the outlet of the storage reheater 12 is controlled. At the superheater side of the rear wall 15, the heat is absorbed by the horizontal superheater 8, the evaporator 3, and the economizer 1. Exhaust gas temperature is about 30
It drops to near 0 ° C. The feedwater sent from the feedwater pump 21 is heated in the economizer 1 by preheating exhaust gas. The supply water temperature at this time is about 280 at the rated load.
° C. Thereafter, the steam passes through the furnace water-cooling wall 2 and the evaporator 3 and is heated by endothermic heat from the exhaust gas to be converted into steam, and the steam flows to the horizontal superheater 7 side by the steam separator 4. At the time of startup, since the feedwater temperature at the inlet of the economizer 1 is as low as about 60 ° C., steam is hardly generated, and the feedwater that has not turned into steam in the steam separator 4 is stored in the brackish water separation drain tank 5. The boiler recirculation pump 6 again circulates to the economizer 1, and the feedwater temperature gradually rises. The steam separated by the steam separator 4 passes through the horizontal superheater 7, the suspended primary superheater 8, the suspended secondary superheater 9, and the suspended tertiary superheater 10, and is gradually heated by the exhaust gas. It becomes high-temperature high-pressure steam and flows to the high-pressure turbine 19. At this time, the steam temperature at the inlet of the high-pressure turbine 19 becomes approximately 590 ° C. at the time of rated load. And the main steam pipe 1
1, the main steam pressure at the inlet of the high-pressure turbine 19 is measured by the pressure gauge 26. When the main steam pressure becomes higher than the main steam set pressure by 2 atg or more, the superheater bypass valve 17 is opened. The steam is released to the condenser 20, and when the main steam pressure becomes higher than the main steam set pressure by 15 atg or more, the high pressure turbine bypass valve 18 is opened to release the steam to the condenser 20. And the main steam pressure is 26at.
When the pressure becomes higher than g, the electromagnetic shutoff valve 25 is opened to release steam to the atmosphere, thereby preventing an abnormal increase in the main steam pressure.

In the conventional emergency stop control method for a boiler, fuel system troubles and auxiliary machine troubles occur during the operation of the boiler, so that the fuel supply to the burner 16 is stopped and the heat quantity in the furnace 35 is reduced. When the inflow is instantaneously shut off and the boiler is emergency-stopped, the high-pressure turbine 19 is also emergency-stopped. At this time, since the heat capacity of the furnace water cooling wall 2 is large, steam continues to be generated even after the fuel is cut off, and the steam flows into the horizontal superheater 7 by the steam separator 4. As a result, the steam pressure on the side of the horizontal superheater 7 tends to increase, so that the high-pressure turbine bypass valve 18 is opened and the condenser 2
Release vapor to zero.

[0005] Japanese Patent Application Laid-Open No. 57-210203 can be cited as a document describing this kind of prior art.

[0006]

However, in such an emergency stop control method for a boiler, the fuel supply to the burner 16 is stopped during the emergency stop of the boiler. Since the steam flowing to the side 7 has a low temperature, when the high-pressure turbine bypass valve 18 is opened, the low-temperature steam flows into the main steam pipe 11, and the main steam temperature decreases. Therefore, when the boiler is restarted, it is necessary to set a longer heating time for increasing the main steam temperature again. In order to prevent low-temperature steam from flowing into the main steam pipe 11, if the opening of the high-pressure turbine bypass valve 18 is reduced, the suspended primary superheater 8
Therefore, the amount of steam flowing through the suspended primary superheater 8 is reduced, and the suspended primary superheater 8 is disposed above the furnace 35, and Because of the radiation heat transfer, the temperature of the pipe of the suspended primary superheater 8 abnormally rises and exceeds the design temperature, and in the worst case, the pipe of the suspended primary superheater 8 may be blown out. is there.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and there is no need to set a longer heating time, and an emergency stop of a boiler in which the temperature of piping of a heat transfer device does not rise abnormally. It is an object to provide a control method.

[0008]

According to the present invention, a high-pressure turbine is connected to a main steam pipe, and a high-pressure turbine bypass valve is provided in a high-pressure turbine bypass line connected to the main steam pipe. In the emergency stop control method for a boiler provided with a heat transfer bypass valve in a heat transfer bypass line connected to the outlet of a heat transfer receiving radiant heat from the furnace, the fuel supply to the burner is stopped. Then, when the high-pressure turbine is stopped, the high-pressure turbine bypass valve is closed, and the heat transfer device bypass valve is opened when the pressure in the main steam pipe exceeds a set value.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An emergency stop control method for a boiler according to the present invention will be described. First, during the operation of the boiler, the supply of fuel to the burner 16 was stopped due to a trouble in the fuel system or a trouble in auxiliary equipment, and an operation for emergency stop of the boiler was performed so as to instantaneously shut off the flow of heat into the furnace 35. At times, the high-pressure turbine 19 is stopped, and the flow of steam into the high-pressure turbine 19 is shut off. At this time, as shown in FIG. 3, the high-pressure turbine bypass valve 18 is closed, the main steam pressure is measured by the pressure gauge 26, and when the main steam pressure exceeds a predetermined value, the superheater bypass valve 17 is opened. The main steam pressure is 13 until the boiler is ignited by the superheater bypass valve 17.
The main steam pressure is controlled so as to be 0 atg. The main steam pressure after ignition is controlled by the high pressure turbine bypass valve 18.
The high-pressure turbine bypass valve 18 controls the main steam pressure so that the main steam pressure becomes 85 atg.
When the main steam pressure becomes higher than the main steam set pressure by 26 atg or more, the electromagnetic shut-off valve 25 is opened to release the steam to the atmosphere, thereby preventing an abnormal increase in the main steam pressure.

In the emergency stop control method for the boiler, when the emergency stop operation of the boiler is performed, the high-pressure turbine bypass valve 18 is closed, so that low-temperature steam does not flow into the main steam pipe 11. The main steam temperature does not decrease. Therefore, when the boiler is restarted, it is not necessary to set a longer temperature raising time for raising the main steam temperature again. That is, since the high-pressure turbine bypass valve 18 is opened after ignition, the main steam pressure is slightly reduced. However, since the high-pressure turbine bypass valve 18 is closed when the boiler is stopped, the flow of steam into the main steam pipe 11 is suppressed. However, since it is possible to prevent a decrease in the main steam temperature when the boiler is stopped, the time for raising the temperature of the boiler at the time of restart can be shortened, and the restart time can be greatly reduced. In addition, when the main steam pressure exceeds the set value, the superheater bypass valve 17 is opened. Therefore, even if the high-pressure turbine bypass valve 18 is closed, the steam passes through the suspended primary superheater 8, so that Even if the suspended primary superheater 8 receives radiant heat transfer from inside the furnace 35, the temperature of the pipe of the suspended primary superheater 8 does not rise abnormally, and the pipe of the suspended primary superheater 8 blows up. It is possible to prevent the occurrence of an accident. That is, by opening the superheater bypass valve 17 and flowing low-temperature steam to the suspended primary superheater 8, the pipe temperature of the suspended primary superheater 8 installed on the upper part of the furnace 35 which becomes high when the boiler is restarted is controlled. It is possible to prevent abnormal rise.

In the above embodiment, the furnace 3
The superheater bypass valve 17 is provided in the superheater bypass line 22 connected to the outlet of the suspended primary superheater 8 receiving the radiant heat transfer from the inside of the furnace 5, but other heat transfer receiving the radiant heat transfer from the furnace A heat transfer device bypass valve may be provided in the heat transfer device bypass line connected to the outlet of the heat transfer device.

[0012]

In the emergency stop control method for a boiler according to the present invention, since low-temperature steam does not flow into the main steam pipe during an emergency stop of the boiler, the main steam temperature is increased again when the boiler is restarted. It is not necessary to set the temperature rise time longer, and since the steam passes through the heat transfer device that receives radiant heat transfer from the furnace, the temperature of the piping of the heat transfer device does not rise abnormally.

[Brief description of the drawings]

FIG. 1 is a view showing a gas flow path of the variable-pressure once-through boiler shown in FIG.

FIG. 2 is a schematic diagram showing a variable-pressure once-through boiler.

3 is a graph showing a temporal change of a main steam pressure and the like at the time of an emergency stop of the variable-pressure once-through boiler shown in FIG.

[Explanation of symbols]

 8 suspended primary superheater 11 main steam pipe 17 superheater bypass valve 18 high-pressure turbine bypass valve 19 high-pressure turbine 22 superheater bypass line 23 high-pressure turbine bypass line 35 furnace

Claims (1)

[Claims] A high-pressure turbine is connected to a main steam pipe, a high-pressure turbine bypass valve is provided in a high-pressure turbine bypass line connected to the main steam pipe, and an outlet of a heat exchanger that receives radiant heat transfer from the furnace. In the emergency stop control method for a boiler provided with a heat transfer device bypass valve in a heat transfer device bypass line connected to the fuel transfer device, the fuel supply to a burner is stopped, and when the high pressure turbine is stopped, the high pressure turbine bypass valve is turned off. A method for controlling emergency stop of a boiler, comprising closing and opening the heat transfer device bypass valve when the pressure in the main steam pipe exceeds a set value.