JP2000266307A - Method and apparatus for protecting pressurized fluidized-bed boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent backflow of a furnace side to an air side by pressure reducing and exhausting high pressure air and high temperature gas, when a boiler is emergency stopped so that the ratio of relief capacity of the air to that of the gas becomes equal to the ratio of the weight of the air to that of the gas. SOLUTION: An emergency pressure reduced mixed gas relief valve 22 is opened fully, after being equalized at emergency stop. A high temperature gas from emergency pressure reducing high temperature gas relief piping 18 and a high pressure air from emergency pressure reducing air relief piping 20 are mixed, temperature lowered by an emergency pressure reducing air high temperature gas mixer 21, and pressure reduced by an emergency pressure reducing mixed gas pressure reducing orifice 24. The mixed gas is reduced for noise by a silencer 25, dust removed by a dust removing tower 26, and then discharged from an discharge port 27 of the tower into the atmosphere. Here, a discharge ratio A:G of high pressure air A to high temperature gas G of the emergency pressure reducing system is set equal to a ratio Wa:Wg of the high pressure air weight Wa in the air system from high pressure air piping 3 to a wind case 8 to the high temperature gas weight Wg in the gas system from a flow layer 9 to a gas turbine inlet valve 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for protecting a pressurized fluidized-bed boiler, and more particularly to a method and an apparatus for emergency depressurization of a high-pressure air and hot gas system during an emergency stop.

[0002]

2. Description of the Related Art A pressurized fluidized-bed boiler includes a piping system for supplying high-pressure air into a fluidized bed, a high-temperature gas piping system for discharging high-temperature combustion exhaust gas from a furnace of the boiler, and water supply and steam piping for the boiler. System.

FIG. 2 is a diagram showing a basic configuration of a pressurized fluidized-bed boiler apparatus. The air pressurized to about 10 kg / cm ² by the compressor 2 is supplied to the pressure vessel 4 through the air pipe 3, the flow rate of the air is further adjusted, and the air enters the furnace 10 to fluidize the fluidized medium layer 9. Coal fuel is introduced into the fluidized medium bed 9, where fluidized combustion occurs. Pressurized combustion gas (for example, about 10 kg / cm ² , 950 ° C.) generated in the furnace 10 is supplied to a gas turbine 15 through a high-temperature gas pipe 11 to drive the compressor 2 and a power source of a generator (not shown). Becomes

On the other hand, in the water supply system, water supplied from a water heater not shown flows through a water supply pipe 39 to the furnace 10.
After passing through the heat transfer tube 40, evaporating and superheating are performed, passing through the main steam pipe 11, working in the high-pressure turbine 43, and further supplied from the low-temperature reheat steam pipe 44 to the reheater pipe 45,
The steam is reheated. The steam that has exited the reheater tube 45 passes through the high-temperature reheat steam tube 46, is supplied to the low-pressure turbine 48, performs work, and is exhausted to the condenser 49.

When the plant is stopped, the load is reduced, the main shut-off valve 42 and the reheat shut-off valve 47 installed at the inlets of the high-pressure turbine 43 and the low-pressure turbine 48 are closed, steam is shut off, and then the reheat pipe drain valve 50 is shut off. And connect it to the condenser 49,
Dry the reheater system. The air and gas systems stop depressurizing as the load decreases, and reach atmospheric pressure.

When the boiler is stopped in an emergency, the above operation is performed promptly. However, there is a danger that unburned components remaining in the fluidized bed will burn and generate heat, and air will flow backward from the furnace side. Also, in the steam system, in the event that the reheater 45 punctures due to friction with the flowing medium, the outside of the pipe is at atmospheric pressure, so the flowing medium is sucked into the pipe. While the vacuum of the condenser 49 is maintained, there is a problem that the scattering range of the flowing medium is increased.

[0007]

An object of the present invention is to provide a high-pressure air and high-temperature gas system for a pressurized fluidized-bed boiler,
In order to minimize the combustion heat generated in the unburned portion remaining in the fluidized bed at the time of an emergency stop, the air flow in the fluidized bed is minutely suppressed, and the backflow from the furnace side to the air side is prevented. An object of the present invention is to provide a method and an apparatus for protecting a pressurized fluidized-bed boiler capable of coping with troubles such as damage in a system.

[0008]

The invention claimed in the present application to achieve the above object is as follows. (1) In the high-pressure air and high-temperature gas system of a pressurized fluidized-bed boiler, when the boiler is stopped in an emergency, the ratio of the high-pressure air release capacity to the high-temperature gas release capacity is changed to the high pressure A method for protecting a pressurized fluidized-bed boiler, comprising discharging under reduced pressure so as to have the same ratio as the weight of air in the system and the weight of hot gas in the system. (2) In a pressurized fluidized-bed boiler having a high-pressure air piping system for supplying high-pressure air to a pressurized fluidized-bed boiler and a high-temperature gas piping system for discharging hot gas from the boiler, an emergency depressurized high-temperature A branch pipe having a gas release orifice and a branch pipe having an emergency depressurized air release valve are provided on the high-pressure air pipe, and these branch pipes are further connected to an emergency depressurized air hot gas mixer. And a discharge device for discharging the mixed gas through the pressure vessel. (3) In order to adjust the flow rate in the fluidized bed in the boiler, a differential pressure gauge is provided in the fluidized bed, and an emergency depressurized air release flow control valve is provided in a high pressure air pipe between the boiler and the branch pipe. (2) The apparatus according to (2), wherein a branch pipe is provided, and the emergency depressurized air release flow control valve is adjusted so that the differential pressure in the fluidized bed becomes a predetermined value. (4) The pressurized fluidized bed boiler has an emergency hot water tank, a brackish water separator, and a boiler recirculation pump, and connects the boiler recirculation pump and the emergency hot water tank with a boiler recirculation pump minimum flow pipe. The emergency hot water tank and the brackish water separator are connected by an emergency hot water overflow pipe, and the protection device for a pressurized fluidized bed boiler according to (2) or (3), (5) In the steam piping system of the pressurized fluidized-bed boiler, when the piping system in the fluidized bed is damaged, a pressure fluctuation in the piping is detected, and a pressurized gas is injected from the outside and provided in the piping. The method for protecting a pressurized fluidized-bed boiler according to (1), wherein the pressure in the pipe is maintained higher than the pressure in the fluidized bed by a pressure regulating valve.

In order to discharge air and high-temperature gas at a constant ratio, a depressurizing orifice is installed in a high-pressure gas emergency depressurizing piping system. This is achieved by installing an orifice that mixes and cools with air before reducing the pressure to atmospheric pressure.

In normal operation, in order to shut off the emergency pressure reducing system, a shutoff valve is installed in the high pressure air pressure reducing pipe, and a shutoff valve is installed in a pipe in which high pressure air and high temperature gas are mixed. Also,
In order to suppress the flow in the fluidized bed as much as possible, an emergency depressurized air release flow control valve that detects the pressure difference in the fluidized bed and decompresses the high-pressure air and releases it to the atmosphere so that this pressure difference does not occur is installed. Is achieved by

[0011]

The discharge capacity of the air and the hot gas in the emergency pressure reducing system is adjusted to the ratio of the weight of the air in the high-pressure air piping system to the weight of the high-temperature gas in the high-temperature gas piping system. That is,
High-pressure air release capacity A: High-temperature gas release capacity G = High-pressure air system weight Wa: By determining the capacity of the decompression orifice so as to satisfy the high-temperature gas system weight Wg, an air flow or backflow occurs in the fluidized bed. The pressure can be reduced without any pressure.

Further, when the amount of gas leak from the gas turbine inlet valve increases or decreases due to the effect of ash adhering to the seat surface of the gas turbine inlet valve at the time of an emergency stop, and an abnormality where a leak occurs in the boiler heat transfer tube in the pressure vessel. Sometimes, in order to avoid air flow in the fluidized bed due to fluctuations in the decompression ratio of air and gas, apart from the above-mentioned system for decompressing air and gas at a constant ratio, the differential pressure in the fluidized bed is The turbulence in the fluidized bed can be eliminated by controlling the flow rate of the air discharged to the atmosphere by reducing the pressure of the high-pressure air so as not to cause the occurrence.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Based on the system diagram of FIG. 1, a high-pressure air and high-temperature gas piping system in a pressurized fluidized-bed boiler;
The overall configuration of the emergency pressure reducing system will be described.

(1) The high-pressure air system includes an air compressor 2, a high-pressure air pipe 3, a pressure vessel 4, a hot-air generator inlet air pipe 5, a hot-air generator 6, a hot-air generator outlet pipe 7, and a wind box 8.
It consists of.

(2) The high temperature gas system is a fluidized bed 9 and a furnace 1
0, a high-temperature gas pipe 11, a primary cyclone 12 and a secondary cyclone 13.
In 5, the temperature is reduced and the gas is discharged from the gas turbine exhaust duct 16 to the low-pressure duct system.

(3) The emergency pressure reducing system includes an emergency pressure reducing hot gas release orifice 17, an emergency pressure reducing hot gas release pipe 18, an emergency pressure reducing air release valve 19, an emergency pressure reducing air release pipe 20, an emergency pressure reducing air high temperature gas mixer 21, It comprises a pressure-reducing air-fuel mixture relief valve 22, a seal air pipe 23, an emergency pressure-reducing air-fuel mixture pressure reducing orifice 24, a silencer 25, a dust removing tower 26, and a dust removing outlet 27.

The seal air pipe 23 shuts off the emergency pressure reducing system during normal operation, but supplies seal air between the emergency pressure reducing mixture release valve 22 (double valve) in order to prevent leakage of high-temperature gas. .

(4) When the decompression ratio of air and gas fluctuates, the system for suppressing the flow in the fluidized bed includes a differential pressure gauge 28 in the fluidized bed, an emergency depressurized air release flow control valve 29, and an emergency depressurized air release. It comprises a flow control valve 30 and a silencer 31.

In the above system, the air compressor 2 draws in air required for combustion in the fluidized bed 9 and the furnace 10 from the air compressor intake port 1, pressurizes the air, and passes through the high-pressure air pipe 3 to the wind box 8. Supplied from The hot-air generating furnace 6 supplies hot air when the fluidized bed 9 is heated at the time of startup, and is used as a part of a pipe for supplying combustion air from the pressure vessel 4 to the wind box during normal operation.

The high-temperature gas burned in the fluidized bed 9 and the furnace 10 passes through a high-temperature gas pipe 11, is dedusted in a primary cyclone 12 and a secondary cyclone 13, passes through a gas turbine inlet valve 14, and passes through a gas turbine 15. The pressure is reduced and the temperature is reduced, and the gas is discharged from the gas turbine exhaust duct 16 to a low-pressure duct system.

At the time of an emergency stop, the air compressor 2 and the gas turbine 15 are stopped. At the same time, the air compressor outlet valve is fully closed, the supply of high-pressure air to the pressure vessel 4 is stopped, and the gas turbine inlet valve 14 is fully closed. The discharge of the high-temperature gas to the gas turbine 15 is stopped. Immediately after the emergency stop, the pressure of the high-pressure air system is higher than the pressure of the high-temperature gas system. Due to this pressure difference, the high-pressure air flows through the fluidized bed 9 and flows into the high-temperature gas system. Also, by fully opening the emergency depressurized air release valve 19 in a short time of about 10 seconds or less, the high pressure air pipe 3 is connected to the valve 19 and the pipe 2.
0, high-pressure air is passed through the mixer 21, the pipe 18, and the orifice 17 to the high-temperature gas pipe 11 to equalize the pressure. After the pressure equalization, the emergency pressure-reducing mixture release valve 22 is fully opened, and the high-pressure gas from the emergency pressure-reducing high-temperature gas releasing pipe 18 and the high-pressure air from the emergency pressure-reducing air releasing pipe 20 are used for the emergency reduced-pressure air high-temperature gas mixer 2.
1 to reduce the temperature of the mixture,
To reduce the noise in the silencer 25 and the dust removal tower 2
After the dust removal in step 6, the dust is exhausted to the atmosphere from a dust removal tower exhaust port 27.

The discharge ratio A: G of the high-pressure air A and the high-temperature gas G in the emergency depressurizing system flows to the high-pressure air weight Wa (= air volume × specific gravity) in the high-pressure air system from the high-pressure air pipe 3 to the wind box 8. Ratio W of hot gas weight Wg (= hot gas volume × specific gravity) in the hot gas system from layer 9 to gas turbine inlet valve 14
a: Same as Wg, that is, A: G = Wa: Wg
By doing so, the air flow inside the fluidized bed 9 and the backflow from the furnace side to the wind box side can be suppressed as small as possible, and the combustion of the remaining unburned components in the fluidized bed can be suppressed as much as possible.

The constant discharge ratio between high-pressure air and high-temperature gas is achieved by selecting the capacity of the orifice to the following ratio. 1) The capacity of the emergency depressurized high-temperature gas relief orifice 17 G = K · Wg 2) The capacity of the emergency depressurized air-fuel mixture decompression orifice 24 (A + G) = K · (Wa + Wg) 3) K: The capacity of the emergency depressurization system and the high-pressure air and high temperature Coefficient based on weight in gas system Leakage occurs when the amount of gas leak from the gas turbine inlet valve increases or decreases due to the effect of ash adhering to the gas turbine inlet valve seat during an emergency stop, and in the boiler heat transfer tube inside the pressure vessel In the event of an abnormality, the opening of the emergency depressurized air release flow control valve 30 is controlled so that the differential pressure of the differential pressure gauge 28 in the fluidized bed is controlled to a positive pressure and as low as possible.
By releasing the sound to the atmosphere, the flow in the fluidized bed 9 can be suppressed. At this time, the emergency depressurized air release flow control source valve 2
9 is fully open and fully closed during normal operation.

According to the invention shown in FIG. 1, the flow in the fluidized bed can be reduced as much as possible, and the high-pressure air and the high-temperature gas can be discharged under reduced pressure.
In addition, backflow of air into the fluidized bed can be prevented.

FIG. 2 is a system diagram of a pressurized fluidized-bed boiler showing another embodiment of the present invention. This apparatus is provided with a steam injection pipe 51 for injecting steam from the outside, a pressure regulating valve 52, and a pressure detection device 53 in the middle of a pipe from a high-pressure turbine 43 of a conventional system to a reheater pipe 45. is there. As the pressurizing gas, nitrogen, clean air or the like can be used in addition to steam. When the reheater tube 45 is damaged due to contact with a fluid medium or the like, the pressure detecting device 5 detects a change in pressure, and injects steam from the steam injection tube 51 by the pressure adjusting valve 52 to maintain the inside of the tube at a predetermined pressure or higher. Hold to prevent the ingress of fluid media and the like.

According to the embodiment shown in FIG. 2, it is possible to prevent the fluid medium from entering the heat transfer tube when the reheat steam pipe is damaged. Inspection of the inside of the high-temperature reheat steam pipe, or cleaning, cutting of the pipe for cleaning, restoration or chemical cleaning, etc., and avoiding the prolonged downtime of the plant due to the work, and the stable supply of electric power can be achieved. .

The apparatus shown in FIG. 2 is applicable to a general pressurized fluidized bed boiler in addition to being used in combination with the apparatus shown in FIG.

FIG. 3 is a view showing a steam system of a pressurized fluidized-bed boiler showing still another embodiment of the present invention. In the figure, boiler water is supplied from a main water supply pump 61 to a main water supply pipe 62.
Is supplied to a furnace 63 and an evaporator 64 in the furnace. The brackish water mixed fluid that has exited the evaporator is separated into steam and water by a steam separator 65, and the steam is superheated by a superheater 70 in a furnace 63, and then is passed through a high-pressure turbine 77. on the other hand,
The water is returned to the main water supply pipe 62 by the boiler recirculation pump 76 and supplied again to the furnace 63 and the evaporator 64 as a part of the boiler water supply. In an emergency such as a stop at the station, the main water supply pump 61 stops and the boiler water supply stops. Therefore, the hot water in the emergency hot water tank 68 is supplied to the main water supply pipe 62 by opening the emergency hot water stop valve 74. The emergency hot water is supplied only from the head because the emergency hot water tank 68 is connected to the outlet of the steam separator by the equalizing pipe 69. Below the minimum flow through load, the boiler water separated by the steam separator 65 is returned to the furnace 63 by the boiler recirculation pump 66.

It is desirable that the emergency hot water reach the predetermined temperature before reaching the rated operation and be maintained at that temperature. In the conventional system, the emergency hot water is made up of makeup water before starting the boiler. The system is heated after being filled with water from the pipe 15. Since the heating source is only the electric heater, no consideration is given to the electric capacity, the heating time, and the like.

In the present invention, during the operation of the boiler recirculation pump 66 from the start-up to the minimum flow-through load, the minimum flow of the boiler recirculation pump is transferred to the emergency hot water tank 68 via the minimum flow pipe 77 of the boiler recirculation pump. After the emergency hot water tank 68 is filled to a predetermined volume, the emergency hot water overflow pipe 77 returns to the brackish water separator 65.

In the steam system of the pressurized fluidized-bed boiler shown in FIG. 3, the outlet of the brackish water separator 65 and the emergency hot water tank 6
8 are connected by an equalizing pipe 69, and an emergency hot water tank and a furnace 6 are connected.
3. In addition to having a head difference between the evaporators 64, a head difference is also provided between the emergency hot water tank 68 and the brackish water separator 65, so that the brackish water by the emergency hot water overflow piping 77 The flow to the separator 65 can be secured, and the water level in the emergency hot water tank 68 can be prevented from rising.

Further, the minimum flow is poured into the emergency hot water tank 78 as close to the bottom as possible, and the emergency hot water overflow pipe 77 is kept as far away as possible so that the emergency hot water tank 78 can be uniformly filled in the emergency hot water tank 78 at a predetermined rate. It can be kept warm to the temperature.

In the prior art, the boiler body is filled with water,
After the filling of the emergency hot water tank is completed, the boiler is started, and the heating source of the emergency hot water is only an electric heater due to its system configuration.
Although a large electric capacity and a long heating time were required to raise the temperature to the saturation temperature (10 to 30 ° C.) of the brackish water separator pressure, in the present invention, after the boiler is filled with water, the boiler is started up, and the boiler is started up at least. The emergency hot water tank is filled with water using the minimum flow of the boiler recirculation pump that operates up to the once-through load.At this time, since the minimum flow is heated by the boiler recirculation pump, warm boiler water is discharged from the point of water filling. Since it flows into the hot water tank, there is no need to heat it again. However, after the boiler once-through operation, the hot water in the emergency hot water tank must be maintained at the above-mentioned predetermined temperature. Therefore, the capacity of the electric heater can be considerably reduced because only the predetermined temperature needs to be maintained without the need for heating.

The hot water capacity in the emergency hot water tank is, for example, 30.
In the prior art, an electric capacity of, for example, about 3 megawatts was required because of the large size of m ^3. However, in the present invention, an electric heater having a capacity of about 100 kilowatts is sufficient, so that the efficiency and the economical effect are low. Very large.

The apparatus system shown in FIG. 3 can be used not only in combination with the apparatus shown in FIG. 1 or 2 but also in a general pressurized fluidized bed boiler.

[0036]

According to the present invention, at the time of an emergency stop, the air flow in the fluidized bed is minutely suppressed, the combustion heat generated in the unburned portion remaining in the fluidized bed is suppressed as much as possible, and the furnace is moved from the furnace side to the air side. It is possible to provide a method and an apparatus for protecting a pressurized fluidized-bed boiler that can prevent backflow and can cope with troubles such as damage in a steam system.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of an emergency depressurization method for a high-pressure air and high-temperature gas system of a pressurized fluidized-bed boiler of the present invention.

FIG. 2 is a system diagram showing an improved example of a steam system of the pressurized fluidized-bed boiler protection device of the present invention.

FIG. 3 is a system diagram showing another improved example of the steam system of the protection device for the pressurized fluidized-bed boiler of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Air compressor inlet, 2 ... Air compressor, 3 ... High pressure air piping, 4 ... Pressure vessel, 5 ... Hot air generating furnace inlet air piping, 6
... hot-air generating furnace, 7 ... hot-air generating furnace outlet piping, 8 ... intercept valve, 9 ... fluidized bed, 10 ... furnace, 11 ... high-temperature gas piping, 12 ... primary cyclone, 13 ... secondary cyclone, 1
4 ... Gas turbine inlet valve, 15 ... Gas turbine, 16 ...
Gas turbine exhaust duct, 17 ... Emergency depressurized hot gas escape orifice, 18 ... Emergency depressurized hot gas escape pipe, 19 ...
Emergency depressurized air release valve, 20 ... Emergency depressurized air release piping, 2
1 Emergency decompressed air high-temperature gas mixer, 22 Emergency depressurized air-fuel mixture relief valve, 23 Sealed air piping, 24 Emergency depressurized air-fuel mixture decompression orifice, 25 Silencer, 26 Dust tower, 27 Evacuation tower exhaust Mouth, 28 ... Differential pressure gauge in fluidized bed, 2
9: Emergency depressurized air release flow control valve, 30: Emergency depressurized air release flow control valve, 31: Silencer.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigenobu Oshima 6-9 Takaracho, Kure-shi, Hiroshima Pref. Inside the Kure Factory (72) Inventor Taro Sakata 6-9 Takaracho, Kure-shi, Hiroshima Pref. Babcock Hitachi, Ltd. Inside the Kure Factory (72) Shuhei Akimoto Inventor 6-9, Takara-cho, Kure-shi, Hiroshima Babcock Hitachi Kure Factory F-term (reference) 3K064 AA06 AA12 AB01 AC05 AC13 AE02 BA17 BA24

Claims (5)

[Claims] In a high-pressure air and high-temperature gas system of a pressurized fluidized-bed boiler, when an emergency stop of the boiler is performed, the high-pressure air and high-temperature gas in the system have a ratio of a high-pressure air release capacity to a high-temperature gas release capacity. A method for protecting a pressurized fluidized-bed boiler, wherein the pressure is reduced so as to be equal to the ratio of the system weight of high-pressure air to the system weight of high-temperature gas. 2. In a pressurized fluidized-bed boiler having a high-pressure air piping system for supplying high-pressure air to a pressurized fluidized-bed boiler and a high-temperature gas piping system for discharging hot gas from the boiler, an emergency A branch pipe having a reduced-pressure high-temperature gas release orifice and a branch pipe having an emergency reduced-pressure air release valve are provided on the high-pressure air pipe, and these branch pipes are further connected to an emergency reduced-pressure air high-temperature gas mixer. The apparatus according to claim 1, wherein the mixed gas is discharged through a reduced pressure orifice. 3. A pressure difference gauge is provided in the fluidized bed for adjusting a flow rate in the fluidized bed in the boiler, and an emergency depressurized air release flow rate is adjusted to a high pressure air pipe between the boiler and the branch pipe. 3. The apparatus according to claim 2, wherein a branch pipe having a valve is provided, and the emergency pressure-reducing air release flow control valve is adjusted so that a differential pressure in the fluidized bed becomes a predetermined value. 4. The pressurized fluidized bed boiler has an emergency hot water tank, a steam separator, and a boiler recirculation pump,
The boiler recirculation pump and the emergency hot water tank are connected by a boiler recirculation pump minimum flow pipe, and the emergency hot water tank and the brackish water separator are connected by an emergency hot water overflow pipe. 4. The protection device for a pressurized fluidized-bed boiler according to 2 or 3. 5. In a steam piping system of a pressurized fluidized-bed boiler, when the piping system in a fluidized bed is damaged, a pressure fluctuation in the piping is detected, and a pressurized gas is injected from the outside, and the gas is injected into the piping. The pressure in the pipe is maintained higher than the pressure in the fluidized bed by a pressure regulating valve provided.
The method for protecting a pressurized fluidized-bed boiler according to the above.