JPH06281103A - Emergency water supplying device for fluidized bed type boiler - Google Patents

Abstract

PURPOSE:To enable a heat transfer pipe part to be cooled easily, in less-expensive manner and rapidly in the case of emergency state without requiring any special pressurizing device and the like by a method wherein a hot water tank for heating stored water is installed, and the hot water stored in the hot water tank is supplied to a heat transfer pipe in a fluidized bed type boiler due to a difference in gravity. CONSTITUTION:Air compressed by an air compressor 1 is supplied to a pressure container 2. Combustion gas generated by a fludized bed type furnace 3 installed within the pressurized container 2 is supplied to a gas turbine 4, thereafter passes through a discharged gas heat exchanger 5 and is discharged from a chimney 6. On the other hand, water supplied from a boiler water supplying pump 7 is heated by a discharged gas heat exchanger 5, thereafter the water is supplied from a water supplying pipe 8 to an evaporator 9 within the furnace 3 so as to generate steam. The steam passes through a gas-water separator 10 and an over-heating pipe 11 and is supplied to a steam turbine 14. In this case, if the emergency case occurs, hot water stored in an emergency hot water tank 39 is supplied under a difference in gravity. With such an arrangement as above, the hot water is immediately evaporated so as to generate steam and then the over-heating pipe 11 is cooled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluidized bed boiler, and more particularly to a fluidized bed boiler equipped with a water supply device suitable for supplying combustion boiler feed water in an emergency.

[0002]

2. Description of the Related Art FIG. 3 shows a water supply system diagram including an emergency water supply of a conventional pressurized fluidized bed boiler which is a representative example of the fluidized bed boiler disclosed in Japanese Patent Laid-Open No. 1-211624. In the pressurized fluidized bed boiler, the air compressed by the compressor 51 passes through the air passage 52 and the air volume control valve 53, and then the pressure container 54.
Is supplied to. A fluidized bed furnace 55 is installed in the pressure vessel 54, and a bed material (BM) is contained therein, and fuel is supplied to the furnace 55 through a route (not shown) and is supplied from a lower portion of the furnace 55. BM by compressed air
It is burning while being fluidized with it. A heat transfer tube 56 is arranged in a region where the fluidized bed is formed, and the water in the heat transfer tube 56 is heated to generate steam. Further, the combustion gas generated in the furnace 55 is guided to the gas turbine 62 via the dust collector 57, the flues 58 and 59, and the opening / closing valve 60.

During operation of the pressurized fluidized bed boiler,
For example, if the power supply to all the equipment in the power plant is lost for some reason and the operation is stopped, the boiler water supply pump (not shown) also trips and the water supply to the furnace 55 is stopped. Therefore, water is not supplied to the heat transfer tube 56 that is in contact with the BM, so that the wall surface of the furnace 55 and the heat transfer tube 56 may be burned. In order to avoid this, first, the air from the compressor 51 is stopped, the flow of the fluidized bed is stopped, the heat conduction from the fluidized bed is suppressed, and then the fluidized bed is cooled. In addition, it is necessary to secure a water supply amount of 10 to 20% of the rated value within about 1 minute after stopping the water supply, and to generate steam in the heat transfer tube 56 for cooling to prevent burnout.

At the time of an emergency stop of all the equipment in the power plant, the gas turbine 62 is also stopped. Therefore, both valves 53 and 60 are closed to guide the exhaust gas in the furnace 55 from the flue 58 to the flow passage 63, and the heat exchanger 64. Then, the BM is cooled and supplied into the furnace 55 together with the nitrogen gas supplied from the nitrogen gas tank 65 through the nitrogen gas supply pipe and the nitrogen gas control valves 66 and 67 to fluidize the BM and cool the BM.

Until the BM is cooled to a predetermined temperature,
An emergency water supply facility is required to protect the wall surface of the furnace 55 and the heat transfer tubes 56 from burnout. In this emergency water supply system, an on-site emergency diesel generator (not shown) is started, and an emergency water supply pump (not shown) that operates by receiving power supply is also started. It is necessary to have an initial water supply facility that supplies water for about 5 minutes (including the allowance time). Since some initial water supply facilities are required to supply water to the boiler within one minute, in order to push out water from the water storage tank using high-pressure inert gas, for example, nitrogen gas of about 250 kg / cm ^2. It is necessary to install the equipment of. Therefore, the nitrogen gas tank 65 is a thick container with a high-pressure design (about 250 kg / cm ² ), and needs a capacity of about 60 m ³ , which is a problem in that its manufacturing and inspection at the time of periodic inspection are expensive. there were. Further, if cold water is supplied, the amount of steam generated is insufficient, and there is a problem that steam necessary for preventing burnout of the heat transfer tubes 56 and the like cannot be obtained.

Further, as shown in FIG. 4 of Japanese Patent Laid-Open No. 61-22103, a fluidized bed in which boiler water is forcedly circulated between a boiler drum 71 and a heat transfer tube 72 in a fluidized bed by a boiler circulation pump 70. A boiler is disclosed, and in the case of an emergency stop of the boiler, the canister water is naturally circulated by the emergency makeup water system 73 and the bypass pipe 75 that bypasses the pump 70 for forced circulation. Is intended to prevent the heat transfer tubes 72 in the fluidized bed furnace 74 and the furnace wall from being burned. At this time, the steam generated by the natural circulation is discharged to the outside of the system to maintain the natural circulation force, but when the canned water in the boiler drum 71 decreases and the natural circulation force disappears, the pump operated by the emergency power system. 76
The can water can be replenished by. In FIG. 4, the water supply is supplied to the boiler drum 71 through the condenser 77, the deaerator 78, the boiler water supply pump 79 and the economizer 80. The emergency water supply device of the present invention requires an emergency water supply pump 76 which is supplied with power from a separately installed on-site emergency diesel generator or the like. In order to start this diesel generator, at least about 5 minutes are required. There was a problem that startup time was required.

[0007]

The first prior art described above does not take into consideration a large increase in the manufacturing cost of the capacity (about 60 m ³ ) of the nitrogen gas tank 65 in the emergency water supply device, There was a problem that equipment cost increased and maintenance and inspection range expanded. The second prior art described above is insufficient as an emergency measure because the starting time of the diesel generator of the emergency water supply device is too long. It is an object of the present invention to provide an emergency water supply system for a fluidized bed boiler, which starts quickly and reduces the facility cost, maintenance and inspection range.

[0008]

The above objects of the present invention can be achieved by the following constitutions. That is, an emergency water supply device for a fluidized bed boiler having a hot water tank for heating the water stored inside by the heating means and a structure for supplying the hot water in the hot water tank to the heat transfer pipe section of the fluidized bed boiler by a gravity difference. Is. At this time, it is desirable that the hot water tank is connected to a steam separator connected to the outlet of the heat transfer tube of the fluidized bed boiler.

[0009]

[Operation] During an emergency stop of all the equipment in the power plant, secure a 10 to 20% of the rated water supply within about 1 minute after the water supply is stopped, and generate steam in the heat transfer tube to cool the furnace wall and the heat transfer tube. However, it is necessary to prevent burnout. According to the configuration of the present invention, when the stored water in the hot water tank is poured into the evaporator of the fluidized bed boiler, steam is immediately produced, and the steam can reach the saturation temperature of the steam pressure so as to cool the superheater. It is constantly heated by a heating means (for example, an electric heater). And
At the time of emergency stop of the boiler, hot water in the hot water tank can be supplied to the heat transfer tube of the fluidized bed boiler by gravity difference without relying on a special power source such as an electric power source, so the heat transfer tube and the furnace wall may be burned out. Disappears.

If this hot water tank is connected to a steam separator connected to the outlet of the heat transfer tube of the fluidized bed boiler,
Hot water is smoothly supplied to the heat transfer tubes without depressurizing the inside of the hot water tank. When the heat transfer tube of the present invention has a function as an evaporator or a superheater, the hot water supplied from the hot water tank cools the evaporator while first generating steam in the evaporator, and the generated steam is the superheater. Sent to and used to cool the superheater. Thus, according to the present invention, the conventional nitrogen gas pressurizing system is unnecessary, and the manufacturing cost, maintenance, and inspection range can be reduced.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A fluidized bed boiler system diagram of an embodiment of the present invention will be described with reference to the system diagrams of FIGS. 1 and 2 by taking a pressurized fluidized bed boiler as an example. Figure 1 shows the overall system diagram of the fluidized bed boiler.
Figure 2 shows only the water injection system of the emergency hot water tank part. The air compressed by the air compressor 1 is supplied to the pressure vessel 2 via the compressor outlet valve 1a. A fluidized bed furnace 3 is installed in the pressure vessel 2, and BM is contained therein, and fuel is supplied to the furnace 3 by a fuel pipe (not shown) to flow. The combustion gas generated in the furnace 3 is guided to the gas turbine inlet valve 4a, and after the work in the gas turbine 4, the heat is recovered in the exhaust gas heat exchanger 5 and discharged from the chimney 6 to the atmosphere.

In the steam system, the boiler feedwater from the boiler feedwater pump 7 is heated by the exhaust gas in the exhaust gas heat exchanger 5, and then supplied from the feedwater pipe 8 to the evaporator 9 in the furnace 3 to generate steam. After the steam is separated into steam and water by the steam separator 10,
It becomes superheated steam in the superheater 11, and is supplied to the steam turbine 14 via the steam cutoff valve 13. The steam used in the steam turbine 14 passes through the condenser 16 and is reused for boiler water supply. A generator 15 is coaxially provided in each of the gas turbine 4 and the steam turbine 14. Also,
The turbine bypass valve 17 is used while the superheated steam is not sufficiently generated when the boiler is started.

At startup of the fluidized bed furnace 3 and at low load,
Since the inside of the evaporator 9 is in a steam-water mixed state, the steam-water separator 10
The boiler water separated from the gas in the boiler circulation pump 18
After that, water is again supplied to the furnace 3. An evaporator 9 and a superheater 11 are attached to the bed material (BM) in the furnace 3, and the BM in the BM tank 37 is used to evaporate the feed water and superheat the generated steam by absorbing heat in proportion to the amount of water supplied. Is taken in and out to change the bed height of the BM in the furnace 3. An exhaust valve 38 is connected to the empty tower portion of the BM tank 37 and is used for exhausting carrier air when the BM is transported from the extraction hopper 21 to the BM tank 37.

In the furnace 3, if all the equipment in the power plant is stopped during normal operation, steam cannot be put into the condenser 16, so the boiler feed pump 7 also trips, and the furnace 3
The water supply to the furnace is stopped, and the furnace 3 and the gas turbine 4 are stopped. At that time, it is necessary to cool the furnace 3, the evaporator 9, and the superheater 11 which are in contact with the BM in order to avoid burning. In other words, within about 1 minute after stopping water supply
A 0% water supply amount is secured, and steam is generated in the furnace 3 and the evaporator 9 for cooling, and the generated steam is ventilated to the superheater 11 by opening the atmosphere release valve 12, and this It should be cooled to prevent burnout.

The emergency water supply device supplies the following water to the evaporator 9. (1) First, the hot water for emergency 39 provided at a position higher than the furnace 3 supplies the water to the evaporator 9. This will be described in detail with reference to FIG. (2) Water is supplied from the pure water tank 27 to the evaporator 9 of the furnace from the water supply pipe 8 via the emergency water supply valve 35 and the exhaust gas heat exchanger 5 by the emergency water supply pump 28.

The emergency water supply system for supplying the evaporator 9 from the emergency hot water tank 39 of (1) is described in detail in FIG. Although the emergency pump 28 and the like do not immediately start up in an emergency such as a power failure in the office, the valve 40 immediately operates and opens in an emergency. Therefore, first, the emergency hot water tank 39 is provided with hot water in the tank 39. Is poured into the evaporator 9 through the valve 40, and immediately evaporates to produce steam, which is cooled, and the superheated tube 11 can be cooled by the steam. Therefore, the stored water in the emergency hot water tank 39 is always heated and kept by the electric heater 42 and its control device 43 up to the saturation temperature of the steam pressure ((saturation temperature) − (10 to 30 ° C.)). In addition, the emergency hot water tank 39 is about 2 times larger than the evaporator 9 of the furnace 3.
Install it about 0m above to secure a static head of hot water for supply. In this way, the water injection pressure to the evaporator 9 is about 2 kg / cm.
It can be ² . Further, at the time of an emergency stop of the boiler, the equalizing valve 44 provided in the pipe 41 connecting the empty tower part of the hot water tank 39 and the empty tower part of the steam separator 10 is opened, and the hot water is smoothly injected into the evaporator 9. To do. The valves 40 and 44 are normally closed.

As described above, in this embodiment, the emergency hot water tank 39 is installed about 20 m above the evaporator 9 of the furnace 3 to secure the static head of the hot water for supply. It is not necessary to provide a nitrogen gas tank (about 250 kg / cm ² ). In an emergency, the water in the steam separator 10 is transferred from the water supply pump 29 for an emergency to the evaporator 9
Can also be supplied to. Further, at the time of an emergency stop of the boiler, it is necessary to extract the BM in the furnace 3, but as shown in FIG. 1, the BM is extracted to the BM cooler 19 via the BM extraction valve 31, and after the BM is cooled, the BM is uniformly cooled. Pressure hopper 20 and B
Send to M extraction hopper 21. This BM cooling water supply is BM
From the cooling water pump 22 to the BM cooler 19 via the valve 34 by the emergency pump 23. Also, the BM cooler 1
Cooling water from the pure water tank 27 is also supplied to the valve 9 through the valve 30. In the above configuration, the pumps 23, 28, 29, which are the drive sources for the emergency, are supplied with power from a separately installed emergency diesel generator or the like.

[0018]

According to the present invention, since the nitrogen gas tank and the nitrogen gas supply device for pressurizing the emergency water supply tank to the pressurized fluidized bed boiler can be reduced, the facility cost, maintenance cost, and inspection range can be reduced. effective.

[Brief description of drawings]

FIG. 1 is a system diagram of an emergency water supply system for a pressurized fluidized bed boiler according to an embodiment of the present invention.

2 is a detailed view of the emergency hot water tank portion of FIG. 1. FIG.

FIG. 3 is a system diagram including a water supply device for a pressurized fluidized bed boiler of the related art.

FIG. 4 is a system diagram including a water supply device of a conventional fluidized bed boiler.

[Explanation of symbols]

2 ... Pressure vessel, 3 ... Fluidized bed furnace, 4 ... Gas turbine, 9
... Evaporator, 10 ... Steam separator, 11 ... Superheat pipe, 14 ... Steam turbine, 19 ... BM cooler, 27 ... Pure water tank, 3
9 ... Emergency hot water tank, 42 ... Electric heater

Claims (2)

[Claims] 1. A hot water tank for heating stored water stored therein by a heating means, and a structure for supplying hot water in the hot water tank to a heat transfer pipe section of a fluidized bed boiler by a gravity difference. Emergency water supply system for fluidized bed boiler. 2. The emergency water supply system for a fluidized bed boiler according to claim 1, wherein the hot water tank is connected to a steam separator connected to the outlet of the heat transfer tube of the fluidized bed boiler.