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PERFORMANCE OPTIMIZATION OF FORCED DRAFT FAN of UNIT #1 (BBGS)

Project Guide:Mr. Samir BandyopadhyaySenior Manager, Mechanical Maintenance DepartmentBudge Budge Generating StationCESC Limited

Presented By:Saikat Halder, Mechanical Engineering, IIEST, Shibpur

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Presentation layout

• Introduction• Fans• Air and Flue gas path• Governing Equations• Result and Discussion• Conclusion

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Introduction

• Forced Draft (FD) fans are used for supplying the combustion air into the furnace of a boiler.

• A good design of fan and its control system increases plant reliability by improving furnace pressure control and airflow control, which is most critical control part of combustion control system.

• In this report, the performance evolution, monitoring and optimization of Forced Draft fan of BBGS unit #1 has represented.

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Fans• Fans generate a pressure to move air (or gases) against a resistance caused

by ducts, dampers, or other components in a fan system.• Fans fall into two general categories: Centrifugal fan Axial flow fan• System characteristics• Fan characteristics

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Fan Characteristics Curve

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Air and Flue Gas path

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Measurement of various fan parameters

• Pressure of air at the discharge to each FD fan at different load.

• Flow of each FD fan at different load.

• Current requirement (Amps) of each FD fan at different load.

• Inlet damper position of each FD fan at different load.

• The average temperature of the air passing through the FD Fan.

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Governing equations

• The equation for determining total efficiency is:

• Power input to the motor

• Power input to the shaft

• Air density

( all the equations are taken from the documents of Bureau of

Energy Efficiency)

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Result

0 20 40 60 80 100 120 140 160 180 200 220 240 260 2800

50

100

150

200

250

300

350

400

450

500

550

600

650

70%80%

90% 100%

Discharge (mᵌ/sec)

50%

Design Point

Hea

d (m

m o

f WC

)

60%

H-Q Curve of FD Fan-A

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Result contd.

0 20 40 60 80 100 120 140 160 180 200 220 240 260 2800

50

100

150

200

250

300

350

400

450

500

550

600

650

Discharge ( mᵌ/sec)

Head

( m

m o

f WC

)

80%90%

100%

60%70%

Design Point

H-Q Curve of FD Fan-B

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Result contd.• Both fan operation

FD Fan-A

FD Fan-B

• Single fan operation FD Fan-A

Load (MW) Volume Flow Rate (mᵌ/sec) Head (mm of WC) Power (kW) Efficiency (%)

150 (60%) 97.8 256 840.8 29.2

175 (70%) 105.1 255 849.9 30.9

200 (80%) 115.7 274 877.3 35.4

225 (90%) 119.5 288 895.6 37.7

250 (100%) 129.0 303 913.9 40.8

Load (MW) Volume Flow Rate (mᵌ/sec) Head (mm of WC) Power (kW) Efficiency (%)

150 (60%) 113.5 260 831.6 34.8

175 (70%) 121.5 261 859.0 36.2

200 (80%) 136.1 289 886.4 43.5

225 (90%) 143.2 292 913.8 44.9

250 (100%) 143.0 299 913.8 45.9

Load (MW) Volume Flow Rate (mᵌ/sec) Head (mm of WC) Power (kW) Efficiency (%)

125(50%) 165.5 200 1017.9 31.9

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Result contd.• Design Efficiency of both the fan: 74.53%

• Both fan operating

FD Fan-A 28.3% to 41.9%

FD Fan-B 34. 8% to 47.6%

• Single fan operating (FD Fan-A) 30% to 35%

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Remedial suggestions

• Design modifications by consulting with the manufacturer or some consulting engineering firms.

• Use of Variable Frequency Drives(VFDs)

• Use of fluid coupling with variable speed

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Conclusion• The capacity of the FD Fan was considerably higher than required.

• The FD fans operated within a low power output area over a long period of time, thereby increasing power consumption and increasing costs of operating the unit.

• Constant speed of the motor creates inefficient operation.

• Use of dampers to control the air flow is a inefficient manner of flow control.

• Modification in the design of the fan, use of use of Variable Speed Drives (VFDs), use of fluid coupling with variable speed are some corrective measures for improvement.

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Thank You