JPH045881B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fluidized bed boiler, and particularly to a means for preventing heating of heat transfer tubes in a steam heater installed in a fluidized bed.

[Prior Art] Heat transfer in general boiler equipment is performed mainly through radiation and contact with high-temperature gas. When starting up this boiler device, the amount of fuel supplied is controlled in advance so that the gas temperature at the outlet of the furnace and the inlet of the reheater is below a specified value in order to protect the superheater and reheater. Furthermore, when the boiler equipment is stopped or the plant trips, overheating of the heat exchanger tubes in the superheater and reheater is prevented by stopping the fuel supply.

[Problems to be Solved by the Invention] On the other hand, in a fluidized bed boiler, unlike a general boiler device, heat transfer to the heat transfer tubes is mainly performed through contact with a heat medium in the bed. Furthermore, since the bed temperature rises to over 750°C as soon as fuel is added during startup, cooling steam must be flowed into the superheater and reheater to protect the heat transfer tubes. Also, even if the fuel supply is stopped when the boiler is stopped or the plant trips,
Since the high temperature state within the bed is maintained for a long time, it is necessary to flow a fluid such as steam for cooling through the heat exchanger tubes embedded in the fluidized bed. Moreover, if there is a power outage, the flow of canned water stops, making it impossible to generate cooling steam and preventing overheating of the heat transfer tubes.

An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a fluidized bed boiler that can reliably prevent overheating of heat exchanger tubes even in a state where power supply is stopped such as a power outage.

[Means for Solving the Problems] In order to achieve this object, the present invention provides: an evaporator embedded in a fluidized bed and connected to a water supply device on the inlet side and a brackish water separator on the outlet side; A fluidized bed boiler that is buried and includes a steam heater whose inlet side is connected to the steam water separator and whose outlet side is connected to the steam using device, and a condenser that condenses exhaust gas from the steam using device, A steam relief valve provided between the steam path that supplies steam from the steam heater to the steam usage device and the condenser and that bypasses the steam usage device and connects the steam path and the condenser. A stop valve is provided between the connection position of the steam path to the steam relief pipe and the steam using device, and when the power supply to the water supply device is stopped, the stop valve is closed and the steam relief pipe is automatically closed. It is characterized by having a valve mechanism that opens automatically, and when the power supply to the water supply device is stopped, the brackish water separation device, the steam heater, and the condenser are communicated with each other. .

[Function] The present invention has the above-described configuration, and even if the pump stops due to power outage such as a power outage,
Since the boiler's self-generated steam can be used to cool steam heaters such as superheaters and reheaters, there is no need to provide a separate cooling steam generation and supply means, reducing the need for incidental equipment. An inexpensive fluidized bed boiler can be provided.

[Embodiments of the invention] Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram of a circulating fluidized bed boiler according to a first embodiment of the present invention.

An evaporator 2, a superheater 3, and a reheater 4 are each buried substantially horizontally in a fluidized bed 1 composed of heat medium particles. During normal operation, canned water supplied to the drum 9 by the water supply pump 8 is transferred to the circulation pump 10.
It is sent to the evaporator 2 through the fluidized bed 1, heated by the fluidized bed 1, boiled, and returned to the drum 9 again.

Here, the steam is separated, and the steam is superheated in a superheater 3 and guided to a turbine 5. The exhaust gas from the turbine 5 is reheated in the reheater 4 and used again to drive the turbine 5, and then the exhaust gas is introduced into the condenser 6 and condensed. After passing through the deaerator 7, this condensate is sent to the drum 9 again by the water supply pump 8.

From ignition of the boiler to ventilation of the turbine, it is necessary to flow steam to the superheater 3 and reheater 4 to prevent overheating of these heat transfer tubes. For cooling the superheater 3, a first steam relief pipe 20 is provided from the middle of the main steam pipe 19, which is piped from the outlet side of the superheater 3 to between the turbine 5, toward the condenser 6. A first steam relief valve 12 is attached in the middle of a steam relief pipe 20. Further, a stop valve 21 is provided between the attachment position of the first steam relief pipe 20 in the main steam pipe 19 and the turbine 5. From the boiler ignition to the turbine ventilation, if the stop valve 21 is closed and the first steam relief valve 12 is opened, the drum 9
Steam can be released from the first steam relief pipe 20 to the condenser 6 through the superheater 3 without passing through the turbine 5, and the superheater 3 can be cooled.

Furthermore, a steam passage pipe 23 extending from the drum 9 is connected in the middle of the reheat steam return pipe 22 which is piped between the turbine 5 and the inlet side of the reheater 4. A reheater vent valve 16 is provided in the middle. Further, a second steam relief pipe 25 with a second steam relief valve 13 attached thereto extends from the middle of the reheat steam supply pipe 24 piped between the outlet side of the reheater 4 and the turbine 5 toward the condenser 6. is located. A stop valve 26 is provided between the turbine 5 and the attachment position of the second steam relief pipe 25 in the reheat steam supply pipe 24 . Then, from the boiler ignition to the turbine ventilation, the stop valve 26 is closed and the second
If the steam relief valve 13 is opened, a portion of the steam from the drum 9 will flow through the steam passage pipe 23 and the reheat steam return pipe 2.
2 and the reheater 4, and the reheater 4 is cooled without being vented to the turbine 5.

The can water supply pipe 27 installed between the drum 9 and the inlet side of the evaporator 2 includes a bypass pipe 18 that can supply can water to the evaporator 2 without passing through the circulation pump 10.
A bypass valve 28 is attached to the bypass pipe 18. Said first steam relief valve 1
2. The second steam relief valve 13 and the bypass valve 28 are both valve mechanisms that automatically open when the power is turned off.

In this way, in the event of a power outage, etc., the superheater 3 and the reheater 4 can be cooled in the same line as the period from boiler ignition to turbine ventilation described above. Furthermore, even if the water supply pump 8 and the circulation pump 10 are stopped, the bypass valve 28 remains open, so the drum 9 located at a high position functions as a head tank, and the canned water in the drum 9 is removed from the bypass valve of the canned water supply pipe 27. 28 to the evaporator 2. Therefore, it is possible to prevent the heat transfer tubes of the evaporator 2 from being overheated due to the heat retained in the fluidized bed 1.

FIG. 2 is a schematic diagram of a once-through fluidized bed boiler according to a second embodiment of the present invention.

In this embodiment, a brackish water separator 11 is used in place of the drum of the first embodiment. Evaporator 2
A superheater stop valve 17 is provided on a pipe that communicates the outlet side of the evaporator 2 with the inlet side of the superheater 3, and a bypass pipe 2 is provided from the outlet side of the evaporator 2 toward the brackish water separator 11.
9 extends, and a bypass valve 14 is attached to the bypass 29. 15 is a brackish water separator 11
This is a superheater vent valve attached to the main steam passage pipe 30 that sends steam to the superheater 3.

As in the first embodiment, a first steam relief pipe 20 provided with a first steam relief valve 12 is piped from the middle of the main steam pipe 19 toward the condenser 6. In addition, a steam passage pipe 23 with a reheater vent valve 16 is connected from the steam separator 11 to the reheat steam return pipe 22.
is piped. Furthermore, a second steam relief valve 13 is connected from the middle of the reheat steam supply pipe 24 toward the condenser 6.
A second steam relief pipe 25 is installed.

From ignition of the boiler to turbine ventilation, the superheater stop valve 17, the stop valve 21 of the main steam pipe 19, and the stop valve 26 of the reheat steam supply pipe 24 are all closed, and the first steam relief valve 12 and the second steam Relief valve 13, bypass valve 1
4. Both the superheater vent valve 15 and the reheater vent valve 16 are open.

Water sent by the water supply pump 8 is boiled in the evaporator 2 and sent to the brackish water separator 11 through the bypass pipe 29. A part of the steam from which the brackish water has been separated passes from the main steam pipe 30 to the superheater 3, and then passes through the main steam pipe 1.
9 and a first steam relief pipe 20 to the condenser 6.

Further, the remaining steam from which the brackish water has been separated can be released from the steam passage pipe 23 through the reheater 4 and through the reheated steam supply pipe 24 and the second steam release pipe 25 to the condenser 6. By doing so, overheating of the heat transfer tubes in the evaporator 2, superheater 3, and reheater 4 can be prevented.

The first steam relief valve 12 and the second steam relief valve 1
3. The bypass valve 14, the superheater vent valve 15, and the reheater vent valve 16 are all valve mechanisms that automatically open when the power is turned off.
In this way, in the event of a power outage, the superheater 3 and the reheater 4 can be cooled in the same lines as when starting the boiler described above. Since there is supplied water in the evaporator 2, the retained water can prevent the heat transfer tubes from overheating.

[Effects of the Invention] The present invention has the above-described configuration, and even if the pump stops due to a power outage or other power outage,
Since the boiler's self-generated steam can be used to cool steam heaters such as superheaters and reheaters, there is no need to provide a separate cooling steam generation and supply means, reducing the need for incidental equipment. An inexpensive fluidized bed boiler can be provided.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are schematic configuration diagrams of fluidized bed boilers according to each embodiment of the present invention. 1... Fluidized bed, 2... Evaporator, 3... Superheater,
4... Reheater, 5... Turbine, 6... Condenser,
8...Water pump, 9...Drum, 10...Circulation pump, 11...Brackish water separator, 12...First steam relief valve, 13...Second steam relief valve, 19...Main steam pipe, 20 ...First steam relief pipe, 22... Reheating steam relief pipe, 23... Steam passing pipe, 24... Reheating steam supply pipe, 25... Second steam relief pipe, 27... Canned water, 30... ...Main steam pipe.

Claims (1)

[Scope of Claims] 1. An evaporator buried in a fluidized bed, whose inlet side is connected to the water supply device and whose outlet side is connected to the brackish water separator; In a fluidized bed boiler comprising a steam heater connected to each steam-using device and a condenser for condensing exhaust gas from the steam-using device, steam is supplied from the steam heater to the steam-using device. A steam relief pipe with a relief valve is provided between the steam path and the condenser, which bypasses the steam using equipment and connects the steam path and the condenser. A stop valve is provided between the connection position and the steam using device, and the valve mechanism is such that when power supply to the water supply device is stopped, the stop valve is closed and the steam relief pipe is automatically opened. A fluidized bed boiler characterized in that the steam water separation device, the steam heater, and the condenser are connected to each other when power supply to the device is stopped.