TANDA TPP - II (2 X 660 MW)
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Salient Technical Features
Ash Handling and Ash Water Recirculation System shall consist of the following sub systems:
Ash handling system shall consist of the following sub systems:
a) Bottom Ash and Economiser Ash Handling System
i) Jet pump and Water Impounded Hopper System – An intermittent system consisting of water impounded hoppers, clinker grinders, jet pumps etc.
OR
ii) Submerged Scrapper Conveyor and dry type hopper System – A continuous system consisting of dry type Bottom Ash hoppers, submerged scrapper conveyors, clinker grinders, bottom ash slurry trench etc.
Economiser/Air preheater ash shall be handled in wet form. Economiser ash slurry from economiser hoppers shall be led to bottom ash hopper and the same shall be discharged along with bottom ash slurry into slurry sump of the Bottom ash slurry disposal pump house. APH ash shall be removed in wet form and disposed as ash slurry into slurry sump of BA slurry disposal pump house.
b) Bottom Ash Hopper Over flow Water System
Over flow water from bottom ash hopper is to be reused in ash handling system. For this purpose overflow tank, settling tank and surge tanks, overflow water transfer pumps and sludge pumps shall be provided.
c) Dry Fly Ash Conveying system
Two alternatives for pneumatic conveying system have been specified for conveying of fly ash in dry form from ESP hoppers, i.e., vacuum conveying system or pressure conveying system.
i) Vacuum Conveying System
It shall consist of liquid ring vacuum pumps, material handling valves, cast iron and MS pipes, instrument air compressor etc.
OR
ii) Pressure Conveying System
It shall consist of screw compressors, air lock/pump tanks, ash intake & discharge valves, CI & MS pipes, instrument air compressors etc.
d) Ash Water System
For more information, please visit Ash-Flushing Pump.
Ash water system shall consist of bottom ash HP water pumps, BA LP water pumps, Flushing water pump, Fly ash HP water pumps, Economiser/Duct Hopper Ash Water pumps etc.
e) Ash Disposal System
i) Bottom ash, economizer/Duct Hopper and APH ash slurry disposal system
The bottom ash, economizer/Duct Hopper ash and APH hopper ash slurry from both the units shall be transported by BA slurry pumps from bottom ash slurry pump house to ash dyke – II.
ii) Fly ash slurry disposal system
The fly ash collected in HCSD silos shall be mixed with water in an agitator tank at controlled rate to obtain the desired high concentration. This high concentration slurry shall be further pumped to Ash dyke – I.
f) Dry Fly Ash Transportation system
The dry fly ash from the electrostatic precipitator hoppers shall be taken to buffer hoppers in each unit. The dry ash buffer hoppers shall be located adjacent to the ESP. Dry fly ash from buffer hoppers shall be transported either to HCSD silos or to storage silos located outside the plant boundary near existing dry ash silos. The dry fly ash transportation system shall be provided for each unit for transportation from buffer hoppers to the silos (HCSD/Storage). The user industries shall take the dry fly ash from storage silos either in closed tankers or in open tankers. The storage silos shall also have rail unloading facilities.
The system will consist of buffer hoppers, Conveying air compressors, CI pipes, Structural steel silo, buffer hopper & silo aeration blowers, hydromix dust conditioners, telescopic chutes, booster & wash water pumps etc.
g) Ash Water Recirculation System
Ash water recirculation system is also included in this package to reclaim the overflow water from bottom ash overflow lagoon in Ash Dyke – II area to the ash water pump house.
Fugitive dust suppression facilities for BA slurry disposal pond are considered comprising dust suppression water pumps, piping and nozzles.
Seepage water pumps are also provided.
B) Under electrical system, LT switchgears, LT power & control cables, lighting, cabling, earthling, lightning protection, VFD etc. are included in the package
C) Under C&I system, instrumentation cables are included in this package. DCS based control system shall be procured separately under station control and instrumentation package.
D) Civil works are excluded from the scope of AHS package.
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.
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.
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