The smoke shutoff door is primarily used at the inlet, outlet, or bypass ducts of the flue gas desulfurization system's absorption tower to isolate flue gas flow. It can also be applied to other flue gas pipelines with high isolation requirements. The smoke shutoff door plays a crucial role in ensuring the normal and stable operation of the boiler and desulfurization system, as well as the safety of the system equipment.
Design Principles and Technical Requirements for Smoke Shutter Doors
The FGD import flue gas damper doors are installed inside the import flue duct of the FGD system, while the wet electrostatic precipitator (WESP) outlet flue gas damper doors are installed inside the WESP outlet flue duct. Both are composed of double-layer flue gas damper doors. When the doors are closed, an air seal is created between the double-layer doors to prevent flue gas from leaking into the FGD and WESP systems, thereby ensuring that protective linings and linings within the FGD and WESP systems remain undamaged. To ensure that all damper doors maintain 100% airtightness under design pressure and temperature, they are equipped with a sealing air gap, along with a sealing air station (including a sealing fan and a backup fan). It is generally required to maintain the pressure of the sealing gas above the flue gas side pressure by 500 to 1250 Pa.
The smoke damper doors are mainly of several types, including double-blade louvered damper doors, double louvered damper doors, and double-sealed louvered damper doors.
Double-blade louver door
The type of smoke damper door consists of a louver, which is made up of two blades, and is equipped with an airtight air system that allows sealed air to enter between the blades. The advantage of this smoke damper door lies in its self-cleaning sealing blade, which operates effectively.
2. Double-hung shutter door
The type of shutter door consists of two louvers, each connected to several bearings, with the two blades fixed on the same shaft. The sealing strips of this shutter door are made of a special nickel-based alloy and installed around the door blades, setting up a sealing air system that allows air to enter between the two louvers. The sealing gas systems of currently designed double-louver shutter doors generally ensure zero leakage rates for chimney pipelines and are equipped with safety precautions under system loads.
3. Double-sealed louver door
The type of shutter door consists of a louver, with each louver featuring only one blade. Two sealing strips are positioned between the upper and lower blades, as well as between the blade and the frame. Air can be sealed into the frame by the sealing strips, maintaining a seal even under corrosive conditions through thermal sealing air.
To ensure the safe operation of boilers, there are stringent requirements for the opening and closing of flue dampers. Electric actuators for damper doors must be safe and reliable, with speeds that meet the operational needs of power plants and fans. Generally, the opening time for flue dampers should be between 16 to 70 seconds, with the damper doors requiring operation that is flexible, reliable, and easy to maintain. Routine maintenance focuses on the agility and reliability of the mechanical parts, which involves clearing dust inside the dampers, cleaning seals, shaft sleeves, gears, and bearings. It also includes calibration of controllers, regulators, and lubrication devices, among others.
