JPH0128281B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fluidized bed boiler, and particularly to prevention of overheating of heat exchanger tubes installed in a fluidized bed.

Heat transfer in general boiler equipment is performed mainly by 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 furnace outlet and reheater inlet is below a specified value to protect the superheater and reheater. Furthermore, when the boiler equipment is stopped or the plant trips, overheating of the heat transfer tubes in the superheater and reheater is prevented by stopping the fuel supply.

Unlike general boiler equipment, in the case of a fluidized bed boiler, heat transfer to the heat transfer tubes is mainly performed through contact with the 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. Furthermore, even if the fuel supply is stopped when the boiler is shut down or the plant is tripped, the high temperature inside the bed remains for a long time. Fluid needs to flow. Moreover, if there is a power outage, the water supply pump, circulation pump, etc. will stop and the flow of canned water will stop, so prepare an emergency power source to prevent the heat transfer tubes from overheating, and switch to the emergency power source at the same time as the power outage. Although the pumps are operated using the same equipment, incidental equipment such as an emergency power supply is required. As a result, there are problems such as the operation of the boiler being complicated, the need for a separate device for generating cooling steam, and the need to prepare an emergency power source.

An object of the present invention is to eliminate the drawbacks of the prior art described above, ensure the prevention of overheating of heat exchanger tubes, and provide an inexpensive fluidized bed boiler that requires few incidental equipment.

To achieve this objective, the present invention provides an evaporator that is embedded in a fluidized bed and has an inlet side connected to a water supply device and an outlet side connected to a brackish water separator; In a fluidized bed boiler equipped with a steam heater connected to each of the steam usage devices and a condenser that condenses exhaust gas from the steam usage device, steam is supplied from the steam heater to the steam usage device. A steam relief pipe with a relief valve is provided between the passage and the condenser, bypassing the steam usage means and connecting the steam passage and the condensing waterway, and providing ventilation from the ignition of the boiler to the steam usage equipment. At the time of starting up the operation, stopping the boiler, and tripping the plant, the relief valve is opened and the steam supplied from the brackish water separation device to the steam heater is passed through the steam relief pipe to the recovery valve. It is characterized by being led to a water container.

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 embedded in the fluidized bed 1, respectively. During normal operation, canned water supplied to the drum 9 by the water supply pump 8 is sent to the evaporator 2 via the circulation pump 10, heated by the fluidized bed 1, boiled, and returned to the drum 9 again.
Here, the brackish water is separated, and the steam is superheated in superheater 3.
It is guided to 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 condensed in the condenser 6.
After the condensate passes through the deaerator 7, it is returned to the supply pump 8.
is sent to drum 9.

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, the turbine 5 is connected from the outlet side of the superheater 3.
A first steam relief pipe 20 is provided halfway to the condenser 6 from the main steam pipe 19 that is piped between the two, and a first steam relief valve 12 is installed in the middle of the first steam relief pipe 20.
Add. 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. If the stop valve 21 is closed and the first relief valve 12 is opened between the boiler ignition and the turbine ventilation, the steam from the drum 9 will pass through the superheater 3 without passing through the turbine 5. Steam can be released from the steam relief pipe 20 to the condenser 6, and the superheater 3 is 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 attached 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 installed. 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 . If the stop valve 26 is closed and the second steam relief valve 13 is opened from boiler ignition to turbine ventilation, a portion of the steam from the drum 9 will be transferred to the steam passage pipe 23 and the reheated steam return pipe 22. The steam passes through the reheater 4 and is not vented to the turbine 5, but can be released from the second steam relief pipe 25 to the condenser 6, and the reheater 4 is cooled.

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.

If you do this, you can use the superheater 3 in the event of a power outage.
Cooling of the reheater 4 and the reheater 4 can be performed in the same line as the period from boiler ignition to turbine ventilation described above. In addition, during a power outage, the water supply pump 8 and circulation pump 10 are stopped, but since the bypass valve 28 is open, the drum 9 located at a high position serves as a head tank, and the canned water in the drum 9 is replaced with canned water. It is supplied to the evaporator 2 through the bypass valve 28 of the supply pipe 27. 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. The heat transfer tubes are similarly prevented from overheating when the boiler is stopped.

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. Outlet side of evaporator 2 and superheater 3
There is a superheater stop valve 17 on the pipe communicating with the inlet side of the
A bypass pipe 29 extends from the outlet side of the evaporator 2 toward the brackish water separator 11, and a bypass valve 14 is attached to the bypass pipe 29. 15 transfers the steam from the steam separator 11 to the superheater 3
This is a superheater vent valve attached to the main steam pipe 30 that sends the steam to the main steam pipe.

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 can be released from the main steam pipe 30 through the superheater 3, through the main steam pipe 19 and the first steam relief pipe 20, and into the condenser 6. Further, the remainder of the steam separated from the brackish water can be released from the steam passage pipe 23 to the reheater 4, via the reheated steam supply pipe 24 and the second steam release pipe 25, to the condenser 6. By doing so, the heat transfer tubes in the evaporator 2, superheater 3, and reheater 4 can be prevented from being overheated.

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, the superheater 3 and the reheater 4 can be cooled during a power outage using the same lines as those used when starting the boiler, respectively.
Since there is supplied water in the evaporator 2, the retained water can prevent the heat transfer tubes from overheating.

The present invention has the above-described configuration, and since the self-generated steam of the boiler can be used to cool steam heaters such as superheaters and reheaters, it is not necessary to separately generate and supply cooling steam. There is no need to provide any means, the number of ancillary equipment can be reduced, and 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... Reheated steam return pipe, 23... Steam passage pipe, 24... Reheated steam supply pipe, 25... Second steam relief pipe, 27... Canned water supply pipe, 30...Main steam pipe.

Claims (1)

[Claims] 1. An evaporator embedded in a fluidized bed and connected to a water supply device on its inlet side and a brackish water separation device on its outlet side, respectively;
A fluidized bed boiler comprising a steam heater buried in a fluidized bed and connected to the steam water separation device on the inlet side and to the steam using device on the outlet side, and a condenser for condensing 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 means and connects the steam path and the condenser. In addition to providing a pipe, the relief valve is opened at the time of start-up of the operation from ignition of the boiler to ventilation to the steam-using equipment, when the boiler is stopped, and during a plant trip, so that the pipe is opened from the steam water separation equipment to the steam heater. A fluidized bed boiler characterized in that steam supplied to the fluidized bed boiler is guided to the condenser via the steam relief pipe. 2. The fluidized bed boiler according to claim 1, wherein the relief valve has a valve mechanism that automatically opens when power supply is stopped.