for extraction of dry fly ash collected at Air Pre-Heater / Duct / Electrostatic Precipitator hoppers of PF type boilers.
Vacuum System is generally adopted when the extraction distance is less, numbers of ESP hoppers are more and plant layout demands two-stage conveying. Vacuum System includes conveying of fly ash from various fly ash hoppers up to the intermediate / buffer / surge hopper (ISH) located near ESP.
A second stage system - positive pressure system is employed to convey fly ash from ISH to main fly ash Silo(s). Vacuum system envisages conveying of dry fly ash from ash hoppers by vacuum pumps and collection in ISH. Each vacuum pump, dedicated to a stream, can convey both coarse and fine ash. The vacuum conveying system operates so as to allow sequential ash discharge from ash hoppers into conveying stream which is in continuous operation.
Vacuum System relies upon an air stream generated by partial vacuum drawn on the receiving station, by means of mechanical exhausters (vacuum pumps), material being dragged into the pipeline by vacuum created and moving in suspension. A bag filter unit with air lock unit, separates the fly ash from the air at the receiving station and collects Fly Ash in Intermediate Surge Hopper, for onward conveying to remote silos / for hydro sluicing. Dome Valves used as Ash Intake Valves, offer 100% sealing at ash hopper outlet.
Macawber Beekay specializes in Dense Phase Pneumatic Conveying System for collecting and conveying of dry coarse/fine fly ash collected at Economizer / Air Pre Heater / Duct / Electrostatic Precipitator hoppers. Dense Phase Pneumatic Conveying System is generally adopted on account of many of its advantages like positive pressure system, low material conveying velocity, lesser erosion rates, conveying of fine and coarse ash separately as collected (thus increasing utility of fly ash), capability to convey longer distances in a single stretch etc.
The system consists of installation of Ash Conveying Vessels directly below the fly ash hoppers. The conveying vessels are equipped with our unique Dome Valve at inlet. Expansion Joint and isolation valve are provided above dome valve. Numbers of conveying vessels are connected to conveying pipe. To reduce number of conveying pipes from ash hoppers, it is possible to join them together. There are different ways to join the conveying lines, either as directed by the Client/Consultant or in view of optimized design.
At fly ash Silo(s), suitable vent filters are provided to vent out clean air. Level sensors are provided in silos and ash hoppers. fly ash Silos are equipped with “dry” and “wet” unloading system for disposal of fly ash in trucks. The system operates on a batch mode for the first stage conveying system and on a continuous mode for second stage transportation system. Compressed air from compressors is used as medium of conveying. Instrument air from a separate source is required for dome valve operation and for instrumentation purpose.
For projects requiring Hydro-sluicing System for transfer of coarse ash/fly ash collected at Economiser / Air Pre-Heater / Electrostatic Precipitator hoppers or along vacuum system or at buffer hoppers/silo's of PF type boilers, we provide various modules like flushing apparatus system, wetting head-cum-slurrifier system, feeder ejector/hydro ejector system, etc. depending upon the application/Client’s requirement.
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