1. 2 July 20151 Air & Draft system www.powerpointpresentationon.blogspot.com

2. 2 July 20152 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

3. 2 July 20153 Arrangement of Boiler Auxiliaries

4. 2 July 20154 Need of Draft System Boiler Combustion Air Flue Gases Air needed for combustion Flue are needed to be evacuated Losses due to flow need to be overcome

5. 2 July 20155 How to select a fan Air or Gas flow -Kg/hr Density (function of temperature and pressure) System resistance (losses) Major Fans in Boiler Draft System PA Fans FD Fans ID Fans

6. 2 July 20156 PRIMARY AIR/MILL SEAL AIR SYSTEM 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.

7. 2 July 20157 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

8. 2 July 20158 SECONDARY AIR SYSTEM 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.

9. 2 July 20159 Burner Box Dampers Coal/Air Dampers Secondary Air Dampers Oil/Secondary Air Dampers Bottom Tier Secondary Air Damper Over Fire Damper

10. 2 July 201510 Primary and Secondary air System in the Boiler

11. 2 July 201511 Axial Fans FD Application

12. 2 July 201512 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: Housing Inlet dampers Rotor with Bearing Shaft Seal

13. 2 July 201513 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.

14. 2 July 201514 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

15. 2 July 201515 PAPH-A SAPH-A SAPH-B PAPH-B FD FAN -B FD FAN-A PA FAN -A SCAPH-B PRIMARY SCAPH-B SECOND SCAPH-A PRIMARY SCAPH-A SECOND TO MILLS HOT PA HDR HOT SA HDR ECO BYPASS ECONOMISER-3 ECONOMISER -2 ECONOMISER -1 HORIZONTAL S.H RE HEATER PLATEN S.HDIVISION PANELETTE S.H COMBUSTION CHAMBER AEROFOIL COLD SEC. AIR COLD PRIM AIR HOT PRIMARY AIR HOT SEC. AIR FLUE GAS PNEUMATICALLY O/P KNIFE EDGE GATE MOTOR O/P LOUVER DAMPER PNEUMATICALLY O/P LOUVER DAMPER MOTOR O/P GATE BIPLANE DAMPER DIVERTER DAMPER AA201 AA202 AA203 AA204 AA205 AA201 AA202AA203 AA205 AA204 AIR AND FLUE GAS PATH TYPICAL 500 MW BOILER TO ESP

16. 2 July 201516 Scheme of Air and Gas Path

17. 2 July 201517 ID Fan at Location

18. 2 July 201518 Variation of Pressure in Boiler 1 FD Fan Inlet 2 FD Fan Outlet 3 Airheater Inlet 4 Airheater Outlet 5 Windbox Pressure 6 Furnace 7 Superheater Platen Inlet 8 Reheater Inlet 9 LTSH Inlet 10 Economiser Inlet 11 Airheater Inlet 12 E.P. Inlet 13 I.D. Fan Inlet 14 I.D. Fan Outlet

19. 2 July 201519 Basics on Fans

20. 2 July 201520 Difference between fans, blowers and compressors EquipmentSpecific RatioPressure rise (mm wcl) FansUp to 1.111136 Blowers1.11 to 1.201136 – 2066 Compressorsmore than 1.20- 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 :

21. 2 July 201521 Typical centrifugal fan operation

22. 2 July 201522 Fan types Centrifugal fan Axial fan

23. 2 July 201523 Centrifugal Fan: Types Paddle Blade (Radial blade) Forward Curved (Multi vane) Backward Curved

24. 2 July 201524 Axial Flow Fan: Types

25. 2 July 201525 Fan Types and Efficiencies

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27. 2 July 201527 System characteristic curve

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29. 2 July 201529 System curve

30. 2 July 201530 Fan Laws

31. 2 July 201531 Fan static pressure Fan Static Pressure  SP = SP (Fan outlet) – SP (Fan inlet) SP (Fan outlet) – Static pressure at fan outlet, mm WC SP (Fan inlet) – Static pressure at fan inlet, mm WC  SP = 0.05 – (-10) = 10.05 mm W.C.

32. 2 July 201532 Speed vs Power % Speed% Power 100 9073 8051 7034 6022 5013

33. 2 July 201533 Flow control  Damper - Most Popular  Variable Speed Drive Recirculation Damper VFC VFD Ideal Power Flow 25 7550100 75 50 25

34. 2 July 201534 Impact of speed reduction

35. 2 July 201535 Use of VSD: Boiler ID fan case study

36. 2 July 201536 Use of VSD: Boiler ID fan case study (contd.)

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40. 2 July 201540 THANK YOU