The boiler raw flue gas is educed in two way from the main duct after the ID fan, boosted through 2
booster fans of 50% capacity and joins into one way, then enters into the absorber for desulphurization. With outlet temperature of about 50℃, the clean flue gas directly enters into main flue duct and is discharged into the atmosphere through stack.
One bypass damper (with two actuators A and B) is installed on the main flue duct of each unit. The flue gas will go through the bypass damper and is discharged through the chimney when the boiler is in starting period, or the flue gas entering into the FGD is overflowing or FGD device in malfunction.
The emergency spray device is installed onto absorber inlet flue duct. When emergency, When the inlet gas temperature reach 160℃ (the maximum design temperature of FGD device inlet gas is 180℃) or the three absorber slurry recirculation pumps all have stopped and flue gas temperature reaches 90℃, the emergency spray device will be started (ABSORBER INLET SPRAY WATER VALVE) to reduce the temperature. When the inlet flue gas temperature reaches 170℃, FGD be stopped by protection and the full-flow bypass damper should be opened immediately.
On FGD inlet and outlet flue duct, flue gas dampers are set for FGD device isolation and maintenance. For flue gas system of each FGD device, 6 flue gas dampers (2 booster fan inlet dampers, 2 booster fan outlet dampers, 1 clean gas damper, 1 bypass flue gas damper) are set.When the FGD system operates normally, the bypass damper is closed, booster fan inlet damper,booster fan outlet damper and clean gas damper are opened, and the raw flue gas enters into FGD device for desulphurization. When FGD system is requested to be shutdown, the bypass damper will open automatically and instantly, while the booster fan inlet damper and booster fan outlet damper and clean gas damper automatically close, then the flue gas can directly go through the chimney. When one booster fan needs to be shutdown for maintenance or the units is in low-load (≤50% loading) operation, the other booster fan can operate singly. In such case, one booster fan can be stopped and inlet and outlet dampers of this booster fan can be closed, and keep the other 9 booster fan in operation.
The air sealing system is set for damper sealing, which can induct the sealing air between closed damper vanes, block flue gas circulation and ensure zero leakage of flue gas. The air sealing system includes sealing fan and electrical heater, and the sealing air pressure keeps at least 5 mbar higher than maximum pressure of flue gas.
Each FGD device has 2 sets (1 in operation and 1 for standby) of high-pressure air sealing fans for booster fan outlet dampers sealing; 2 sets (1 in operation and 1 for standby) of low-pressure air sealing fans for other dampers sealing.
Each booster fan has 1 set of independent lubrication station and 2 cooling fans to ensure continuous and safe operation of booster fan. When the boiler operation condition changes from 25%BMCR to BMCR, the flue gas system of FGD can operate normally and can keep continuous and safe operation. Under the condition of BMCR and inlet flue gas temperature is 10℃ higher than design value. It can also operate continuously and safety.
One bypass damper (with two actuators A and B) is installed on the main flue duct of each unit. The flue gas will go through the bypass damper and is discharged through the chimney when the boiler is in starting period, or the flue gas entering into the FGD is overflowing or FGD device in malfunction.
The emergency spray device is installed onto absorber inlet flue duct. When emergency, When the inlet gas temperature reach 160℃ (the maximum design temperature of FGD device inlet gas is 180℃) or the three absorber slurry recirculation pumps all have stopped and flue gas temperature reaches 90℃, the emergency spray device will be started (ABSORBER INLET SPRAY WATER VALVE) to reduce the temperature. When the inlet flue gas temperature reaches 170℃, FGD be stopped by protection and the full-flow bypass damper should be opened immediately.
On FGD inlet and outlet flue duct, flue gas dampers are set for FGD device isolation and maintenance. For flue gas system of each FGD device, 6 flue gas dampers (2 booster fan inlet dampers, 2 booster fan outlet dampers, 1 clean gas damper, 1 bypass flue gas damper) are set.When the FGD system operates normally, the bypass damper is closed, booster fan inlet damper,booster fan outlet damper and clean gas damper are opened, and the raw flue gas enters into FGD device for desulphurization. When FGD system is requested to be shutdown, the bypass damper will open automatically and instantly, while the booster fan inlet damper and booster fan outlet damper and clean gas damper automatically close, then the flue gas can directly go through the chimney. When one booster fan needs to be shutdown for maintenance or the units is in low-load (≤50% loading) operation, the other booster fan can operate singly. In such case, one booster fan can be stopped and inlet and outlet dampers of this booster fan can be closed, and keep the other 9 booster fan in operation.
The air sealing system is set for damper sealing, which can induct the sealing air between closed damper vanes, block flue gas circulation and ensure zero leakage of flue gas. The air sealing system includes sealing fan and electrical heater, and the sealing air pressure keeps at least 5 mbar higher than maximum pressure of flue gas.
Each FGD device has 2 sets (1 in operation and 1 for standby) of high-pressure air sealing fans for booster fan outlet dampers sealing; 2 sets (1 in operation and 1 for standby) of low-pressure air sealing fans for other dampers sealing.
Each booster fan has 1 set of independent lubrication station and 2 cooling fans to ensure continuous and safe operation of booster fan. When the boiler operation condition changes from 25%BMCR to BMCR, the flue gas system of FGD can operate normally and can keep continuous and safe operation. Under the condition of BMCR and inlet flue gas temperature is 10℃ higher than design value. It can also operate continuously and safety.
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