JPS6229603Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fluidized bed boiler, and more particularly to a protection device for steam pipes disposed within the fluidized bed boiler during emergency shutdown.

The temperature inside the bed of a fluidized bed boiler that uses heavy oil, coal, etc. as fuel is usually 800 to 900°C.
The amount of heat transfer (heat transfer coefficient) in the layer of these heat transfer tubes and steam tubes is about 5 to 10 times greater than the amount of heat transferred only from the gas flow of a conventional boiler, and is characterized by a large amount of heat transfer.

Furthermore, since fluidized bed boilers have excellent heat transfer characteristics in the bed, even low-grade coal such as sludge coal, which was traditionally dumped into piles, can be effectively used as fuel for fluidized bed boilers. In recent years, fluidized bed boilers have been attracting attention because they can reduce the volume of low-grade coal by incinerating these low-grade coals.

However, in a fluidized bed boiler, the temperature inside the bed is 800 to 900℃.
Although the amount of heat transferred in the layer is large compared to the amount of heat transferred only from the gas flow in conventional boilers, for example, if the steam turbine breaks down,
Alternatively, in the event of an emergency shutdown of the boiler plant due to a power outage, the steam supply to the turbine will be stopped, and the fuel supply, water supply, etc. to the fluidized bed boiler will also be immediately stopped. is problematic.

This is because the heat exchanger tubes and steam tubes of the fluidized bed boiler are placed inside the fluidized bed, where the temperature inside the bed is 800 to 900℃ when the water supply to the fluidized bed boiler is stopped.
This is because these heat transfer tubes and steam tubes are unilaterally heated by the amount of heat held in the fluidized bed, which eventually leads to thermal deformation and burnout accidents.

The present invention attempts to eliminate such conventional drawbacks, and its purpose is to prevent thermal deformation and burnout of steam pipes buried in the fluidized bed that occur during emergency shutdowns.

To achieve this objective, the present invention comprises a fluidized bed, a heat exchanger tube for evaporating feed water, a drum connected to the heat exchanger tube, and a drum disposed within the fluidized bed to superheat steam fed from the drum. a communication pipe that connects the drum and the steam pipe and has a regulating valve in the middle, a main steam pipe that supplies superheated steam from the steam pipe to the turbine via a main steam valve, and the steam pipe. turbine bypass piping that can supply superheated steam from the turbine to the condenser via a regulating valve;
A transmitter is provided that outputs a signal to the regulating valve of the communication pipe and the regulating valve of the turbine bypass piping in the event of an emergency shutdown of the main steam pipe.

When the main steam valve is shut off in an emergency, the regulating valve of the communicating pipe and the regulating valve of the turbine bypass pipe are opened to predetermined states based on the signal output from the transmitter, and the steam accumulated in the drum is transferred to the communicating pipe. The steam pipe in the fluidized bed is ventilated through the steam pipe, and the steam pipe is cooled from inside by the flowing steam, thereby protecting the steam pipe.

The outline of a fluidized bed boiler will be explained below using FIG. 1.

A perforated plate 2 is arranged at the bottom of the fluidized bed boiler 1,
A fluidized bed 4 is formed on the perforated plate 2 by the fluidized medium introduced from the medium input pipe 3. A steam pipe 5 and a heat transfer tube 7 are disposed within the fluidized bed 4, and a heat transfer tube 7 is disposed in the empty tower section 6 above the fluidized bed 4 for the purpose of recovering waste heat.

On the other hand, the fluidizing air and combustion air supplied by the fan 8 are preheated by the air preheater 9, and the fluidizing air is sent from the air passage 10 through the air passage 11 to the air chamber 12 of the fluidized bed boiler 1. On the other hand, the combustion air is mixed with fuel from the fuel pipe 14 from the air passage 10 through the air passage 13, and is supplied into the fluidized bed 4 from the bottom of the perforated plate 2.

On the other hand, the fuel combusted in the fluidized bed 4 and the powdered fluidized medium are heat-recovered in the fluidized bed 4, the sky section 6, the steam pipe 5, and the heat transfer tube 7, become exhaust gas, reach the flue 15, and pass through the dust collector. At 16, dust and unburned substances are collected and discharged from a fan 17 to a chimney 18.

Note that 19 is a fluidized bed boiler for incinerating unburned matter and dust, and a heat exchanger tube 21 is arranged in the fluidized bed 20.

The flow of water supply during normal operation of the fluidized bed boiler 1 in such a structure will be explained using FIG. 2.

Water from a boiler circulation pump (not shown) is supplied from a water supply pipe 21 to a drum 22, and the hollow cylinder 6
and the heat exchanger tubes 7 of the fluidized bed 4 from the inlet communication pipe 23a.

The feed water heated by this heat transfer tube 7 is transferred to the outlet connecting tube 2.
3b to the drum 22, separated into steam and water by the drum 22, and the water is supplied again to the heat transfer tube 7, while the steam is supplied to the steam tube 5 from the steam communication tube 24 and is transferred in the fluidized bed 4. The steam is superheated by the heat and is supplied to the turbine 26 through the main steam pipe 25.

This steam releases energy in the turbine 26, is condensed in the condenser 28, and is again supplied to the water supply pipe 21 through the condensate pipe 29.

Note that 27 is a generator and 31 is a main steam valve.

In this way, during normal operation of the fluidized bed boiler 1, water supply and steam flow into the steam pipes 5 and heat transfer tubes 7, but when the turbine 26 fails, the water supply and steam to the steam pipes 5 and heat transfer tubes 7 are temporarily stopped. Ru.

The operation when the turbine 26 fails will be explained below using FIG. 2.

If the turbine 26 fails, the main steam valve 3
1 is fully closed to completely stop the supply of steam to the turbine 26, and the regulating valve 32 of the steam communication pipe 24 is also fully closed to temporarily stop the supply of steam to the steam pipe 5.

Of course, at this point, the fuel supply from the fuel pipe 14 and the water supply from the water supply pipe 21 to the fluidized bed boiler 1 are also completely stopped.

In this way, the water supply from the water supply pipe 21 and the steam communication pipe 2
If the steam from the fluidized bed boiler 1 is temporarily stopped, the evaporation tube 5 and the heat transfer tube 7 of the fluidized bed boiler 1 will be unilaterally overheated by the waste heat of the fluidized bed 4 and heat transfer in the bed. The heat exchanger tube 7 is connected to the drum 22 and the inlet communication tube 23a,
Since the drum 22 is connected by the outlet connecting pipe 23b, the water supplied in the drum 22 flows to the heat transfer tube 7 and is cooled, thereby protecting the drum 22 from thermal deformation and burnout.

Furthermore, even if the boiler circulation pump (not shown) stops due to a power outage, the water supply pipe 2 is replaced by a steam-driven Worthington pump, steam turbine pump, etc. in place of the boiler circulation pump.
1 to the drum 22, the heat exchanger tubes 7 can be protected.

However, the regulating valve 3 is connected to the steam pipe 5 in the fluidized bed 4.
2 is completely closed and steam is stopped, and the steam pipe 5 is unilaterally overheated by the intralayer heat transfer of the fluidized bed 4.

Therefore, in the present invention, as shown in FIG. 2, when the fluidized bed boiler 1 is stopped in an emergency, the main steam valve 31 is fully closed, and the regulating valves 32 and 33 are opened to a half-open degree to direct the steam held by the drum 22 into the fluidized bed 4. Supplied to steam pipe 5,
This steam cools the steam pipe 5 from inside the pipe. Note that the steam that has cooled the steam pipe 5 is passed from upstream of the main steam valve 31 to the turbine bypass piping 30 having a regulating valve 33 to the condenser 28.
flow to

That is, in the event of an emergency stop of the fluidized bed boiler 1, the main steam valve 31 is fully closed to stop the steam flowing to the steam turbine 26, and the regulating valves 32 and 33 are opened by the signal 35 from the transmitter 34 to supply the drum 22. (vapor having a temperature lower than the temperature inside the fluidized bed 4) is transferred to the steam pipe 5 buried in the fluidized bed 4.
It flows to

In other words, the minimum flow rate (of the rated steam amount) to the steam pipe 5 is
25 to 50% capacity) from the drum 22 through the steam communication pipe 24, the steam pipe 5, the main steam pipe 25, and the turbine bypass pipe 30 to the condenser 28. 5 is cooled by this steam, and can be protected from thermal deformation and burnout caused by unilateral overheating due to heat transfer in the layer.

According to the present invention, even during an emergency shutdown of the boiler, the steam pipes in the fluidized bed are cooled by the amount of steam retained in the boiler, so it is possible to prevent thermal deformation and burnout of the steam pipes. can effectively utilize the amount of heat it has.

[Brief explanation of the drawing]

Figure 1 shows the flow sheet of a fluidized bed boiler.
FIG. 2 is a detailed diagram of a fluidized bed boiler showing an embodiment of the present invention. 1...Fluidized bed boiler, 4...Fluidized bed, 5...Steam pipe, 7...Heat transfer tube, 25...Main steam pipe, 26...
... Turbine, 28 ... Condenser, 30 ... Turbine bypass piping, 31 ... Main steam valve, 32, 33 ...
...Adjustment valve, 34...Transmitter, 35...Signal.

Claims (1)

[Claims for Utility Model Registration] A fluidized bed, a heat exchanger tube for evaporating feed water, a drum connected to the heat exchanger tube, and a steam tube disposed within the fluidized bed for superheating steam sent from the drum. a connecting pipe that connects the drum and the steam pipe and has a regulating valve in the middle; a main steam pipe that supplies superheated steam from the steam pipe to the turbine via a main steam valve; It includes a turbine bypass pipe that can supply steam to the condenser via a regulating valve, and a transmitter that outputs a signal to the regulating valve of the communication pipe and the regulating valve of the turbine bypass pipe in the event of an emergency shutdown of the main steam valve. In the event of an emergency shutdown of the main steam valve, the regulating valve of the communicating pipe and the regulating valve of the turbine bypass piping are opened to predetermined states based on the signal output from the transmitter, and the steam accumulated in the drum is diverted to the communicating pipe. A fluidized bed boiler, characterized in that the steam pipe in the fluidized bed is ventilated through the steam pipe, and the steam pipe is cooled from inside the pipe by the steam flowing through the pipe.