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Sunday, September 23, 2012

PowerPoint Presentation On Air And Draft system

PPT On Air And Draft system

Air And Draft system Presentation Transcript:
1. Presentation Plan
Various auxiliary equipments in a boiler
Need for Draft System
Primary and secondary air system in Boiler and their fans
Other fans in a boiler
Basic of fans: Fan Types and selection
Fan laws and factors affecting fan performance
Performance curves

Ambient air is drawn into the primary air ducting by two 50% duty, motor driven axial reaction fans.
Air discharging from each fan is divided into two parts, one passes first through a air pre-heater then through a gate into the P.A bus duct. The second goes to the cold air duct. The mix of both is used to carry the pulverized coal to the boiler.

3. Components of PA Fan
Suction Bend With volume Measurement instruments
Fan housing with Guide Vanes
Main Bearings (Anti Friction)
Rotor with impeller with adjustable blade with pitch control
Guide vane housing with guide vanes
Diffuser with pressure measurement instruments

Ambient air is drawn into the secondary air system by two 50% duty, motor driven axial reaction forced draft fans with variable pitch control.
Air discharging from each fan passes first through a air preheated then through a isolating damper into the secondary air bust duct.
The cross over duct extends around to each side of the boiler furnace to form two secondary air to burner ducts.
At the sides of the furnace, the ducts split to supply air to two corners. Then split again to supply air to each of nineteen burner/air nozzle elevations in the burner box.

5. Burner Box Dampers
Coal/Air Dampers
Secondary Air Dampers
Oil/Secondary Air Dampers
Bottom Tier Secondary Air Damper
Over Fire Damper

6. Induced Draft System
There are three induced draught fans per boiler, two operating and one standby
 In 500 MW fans are single-stage, double-inlet centrifugal fans. Principal fan elements of the fan are:
Inlet dampers
Rotor with Bearing
Shaft Seal

7. ID Fan
The rotor consists of shaft and assembled impeller and runs in two sleeve bearings that are arranged outside of the housing.
The impeller consists of a centre disc and two cover discs that are reinforced by forged rings. The bent blades are welded into position between the impeller discs.
The blades are protected by screwed - on wear plates.
The shaft is of hollow design. The fan shaft has been rated so that max. operating speed is below the critical speed. Impeller and shaft are connected by means of a flange. This screwing is protected by wear plates. The fan housing is sealed by means of two-part labyrinth seals.
Bearings are lubricated with oil.

8. Other Fans in The System
Ignitor Air Fan: Provide combustion air to the ignitors. Take suction air from the atmosphere and supplies air to the ignitor wind box.
Scanner Air Fan: Supplies cooling air to flame scanners. Normally there are two fans taking suction from FD Fan discharge duct.
Mill Seal air fan: Seal air fans provide air for the sealing of Mill bearing. Suction is from cold Primary air and pressure is boosted up to maintain the differential pressure

9. Difference between fans, blowers and compressors
As per ASME the specific pressure, i.e, the ratio of the discharge pressure over the suction pressure is used for defining the fans, blowers and compressors as highlighted below :

10. For more please refer our PPT. Thank You.

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