Boiler ea case study 16 jan 2012 varanasi

CASE STUDY ON AS RUN BOILER ENERGY AUDIT AND REPORTING

D PAWAN KUMAR & R VIRENDRANATIONAL PRODUCTIVITY COUNCIL,

INDIA(16 January 2012)

OBJECTIVES

Efficiency of Boiler

As run Boiler efficiency, at three representative load setting over 9 trials

Assessment of Boiler Loss Profile and Heat rate during trial conditions

Assessment of Heat Exchangers Effectiveness of Heat Exchangers such as Air Preheaters, Economisers, Condensers etc

INSTRUMENTS REQUIRED

Flue gas analysers Portable temperature indicator On-line instruments of boiler control room. Facilities of the chemistry lab or outside lab for coal /

ash / water analysis. (coal proximate or ultimate analysis, un-burnt in bottom and fly ash, TDS, pH of feed water / blow-down / condensate.

Power analyser for power measurement of ID fan, FD fan, ESP, crushers, BFP (boiler feed water pump) cool handling plant/ash handling plant, etc.

METHODOLOGY Boiler Efficiency trials are normally conducted at three

representative typical load ranges namely, 100% of NCR, 80% of NCR and 60% of NCR

Performance assessment chosen is the indirect method of heat loss and Boiler Efficiency calculation, drawn from Indian Standard (IS-8753/1977) and the deployed relations are presented as follows

During the Boiler trials, following key parameters are monitored as Power Generation, Coal Consumption, GCV of Coal, Total Air Flow, Mill rejects, GCV of Mill rejects, Combustibles in bottom ash, Bottom ash Quantity, Combustibles in ECO/APH ash, ECO/APH ash Quantity, Combustibles in Fly ash, Fly ash Quantity, Flue gas analysis APH outlet for %CO2, %O2 and temperature, Ambient air dbt, wbt and RH%, P.A. (Proximate Analysis) of coal, V.A. (Ultimate Analysis) of coal, various flows, pressure and temperature in steam, water, air, flue gas path, power measurement at key auxiliaries.

BASIS FOR HEAT LOSS CALCULATIONS:

BOILER PARAMETERS THE LIST OF NEARLY 136 BOILER PARAMETERS

MONITORED AND THE CORRESPONDING TRASNDUCER REFERENCES VIS-À-VIS THE DAS SYSTEM ARE ALSO TO BE REPORTED.

DESIGN OPERATING PARAMETERS(Reference values) are also to be reported Design Flow, Temperatures and Pressures for

Steam, Water, Fuel & air and Flue gas along with Pressure drops as relevant are also reported. Design heat balance is also reported as reference basis.

Present case is of a 200 MW boiler AS RUN AUDIT FINDINGS PLANT ROAD

Available data is for 100%, 80%, 60% NCR. The three typical load ranges at which the

Boiler Performance could be assessed was

Load SettingNo of Trials

a) > 90% of NCR 6b) > 80% of NCR 1

c) > 70% of NCR 2Total: 9

KEY BOILER TRIAL FINDINGS

The Key Boiler trial findings in respect of Auxiliary Consumption, Feeder wise Coal Consumption, Coal GCV, DM Water Consumption, Power Generation, Specific Coal Consumption and Overall Heat Rate are presented in the following tables.

SUMMARY OF KEY BOILER TRIAL FINDINGS

S.NO.

PARAMETERS UNITS TRIAL 1 TRIAL 2 TRIAL 3 TRIAL 4 TRIAL 5 TRIAL 6 TRIAL 7 TRIAL 8 TRIAL 9

1 DATE

2 DURATION HRS 0900-13001445-

1845

0915-1315

1015-1415

1500-1900

1915-1315

1430-1830

1430-1830

1430-1830

3 TORAL DURATION HRS 4.00 4.00 4.00 3.75 3.50 3.75 3.00 3.00 3.00

4 TOTAL GENERATION MWH 776.40 779.70 768.00 570.50 531.00 701.00 499.00 545.00 542.00

5TOTAL AUXILIARY

CONSUMN.-1MWH 26.15 26.23 26.04 18.35 16.75 26.75 16.70 17.40 18.40

6TOTAL AUXILIARY

CONSUMN.-2MWH 27.05 27.07 27.21 24.50 22.60 25.27 16.30 16.80 17.60

7TOTAL AUXILIARY

CONSUMN. (ITEM5+ITEM6)

MWH 53.20 53.30 53.25 42.85 39.35 52.02 33.00 34.20 36.00

8COAL FEEDER-A

CONSUMN.MT 81.70 97.90 87.80 97.50 91.20 - 63.90 68.80 67. 50

9COAL FEEDER-B

CONSUMN.MT 96.30 95.90 97.80 94.60 88.10 91.60 65.50 66.90 65.'00

10COAL FEEDER-C

CONSUMN.MT - - 95.40 - - 93.50 66.50 70.90 73.20

11COAL FEEDER-D

CONSUMN.MT 89.00 90.90 89.90 94.60 85.40 88.80 60.00 56.70 59.80

12COAL FEEDER-E

CONSUMN.MT 89.40 90.90 - - - 85.80 - - -

13COAL FEEDER-F

CONSUMN.MT 90.20 93.30 91.60 95.40 87.60 91.30 66.10 72.50 72:50

14OM WATER

CONSUMN.MT 40.85 35.80 40.85 30.80 28.55 37.05 37.35 33.05 29.30

15 G CVOFCOAL KCAUKG 4597.00 4090.00 4450.00 3986.00 4018.00 3863.00 3502.00 3955.00 3973.00

SUMMARY:

16AVERAGE POWER GENERATION

MW 194.10 194.93 192.00 152.13151.71

186.93

166.33

181.67

180.67

17 % OF NCR % 97.05 97.46 96.00 76.0775.86

93.47

83.17

90.83

90.33

18 AUXILIARY CONSUMN. MW 13.30 13.33 13.31 11.4311.24

13.87

11.00

11.40

12.00

19% AUXILIARY CONSUMN.

% 6.85 6.84 6.93 7.517.4

17.4

26.6

16.2

86.6

4

20 COAL CONSUMN.RATE MT/HR 11.65 117.23 115.63 101.89100.66

120.27

107.33

111.93

112.67

21OM WATER CONSUMN. RATE

MTIHR 10.21 8.95 10.21 8.218.1

69.8

812.45

11.02

9.77

22 OM WATER CONSUMN. KGIKWH 0.05 0.05 0.05 0.050.0

50.0

50.0

70.0

60.0

5

23 SP. COAL CONSUMN. KGIKWH 0.58 0.60 0.60 0.670.6

60.6

40.6

50.6

20,6

2

24 OVERALL HEAT RATE KCAUKWH 2644.28 2549.67 9.85 2669.682665.8

0

2485.3

3

2259.8

1

2436.8

6

2477.6

3

KEY PARAMETERS DURING TRIALS VIS-A-VIS DESIGN

The key Boiler parameters, pertinent to Thermal Efficiency, namely the MW Generation (Load), Coal Consumption, GCV of Coal, Total Air Flow, Mill Rejects, GCV of Mill Rejects, Combustibles in Bottom Ash, Fly Ash, Flue Gas Anal1ysis at APH Out, Ambient conditions, Proximate Analysis of Coal, alongside the design values, are reported as under.

BOILER PERFORMANCE EVALUATION: SUMMARY OF KEY PARAMETERS DURING BOILER TRIALS

S.No

Operating Parameters Unit Design Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 Trial 6 Trial 7 Trial 8 Trial 9

1. POWER GENERATION MW 200.00 194.07 194.95 191.98 153.33 153.15 185.92 166.30 181.67 180.67

2. % OF NCR % 100.00 97.04 97.48 95.99 76.67 76.58 92.96 83.15 90.84 90.34

3. COAL CONSUMPTION TPH 103.00 117.94 116.55 118.18 104.11 103.11 123.04 107.26 111 .90 112.67

4. G C V OF COAL KJ/KG 17974.00 19215.46 17096.20 18601.00 16661.4816795.

2416147.34 14638.36 16531.90

16607.14

5. TOTAL AIR FLOW TPH 725.40 773.92 769.30 738.56 706.29 691.94 743.79 598.50 615.40 703.00

6 MILL REJECTS KG/HR 339.90 389.20 384.62 389.99 343.56 340.26 406.03 353.96 369.27 371.81

7. G C V OF MILL REJECTS KCAUKG 1800.00 2610.00 2660.00 2550.00 2420.002500.0

02150.00 1860.00 1880.00

1800.00

8. COMB. IN BOTTOM ASH % 2.01 5.10 5.00 4.10 3.70 2.59 3.60 2.50 2.65 2.25

9. C V OF CARBON KJ/KG 33766.04 33766.04 33766.04 33766.04 33766.0433766.

0433766.04 33766.04 33766.04

33766.04

10.

BOTTOM ASH QTY. (Dry basis) KG/KG 0.05 0.04 0.04 0.04 0.05 0.05 0.05 0.06 0.05 0.05

11.

COMB. IN ECO/APH ASH % 0.23 5.00 4.00 2.10 1.00 1.22 2.35 1.38 1.70 1.20

12.

ECO/APH ASH QTY. (Dry basis) KG/KG 0.04 0.03 0.04 0.03 0.04 0.04 0.04 0.05 0.04 0.04

13.

COMB. IN FLY ASH % 0.46 3.45 2.00 3.30 1.30 1.49 2.40 1.04 1.20 0.70

14.

FLY ASH QTY. (Dry basis) KG/KG 0.23 0.17 0.21 0.19 0.24 0.24 0.24 0.29 0.24 0.24

15.

FLUE GAS ANAL YSIS (APH OUT)

CARBON DIOX!DE (CO2) % 15.00 15.20 14.79 15.00 13.18 12.68 14.26 15.70 16.10 15.97

OXYGEN (02) % 4.00 3.80 4.21 4.00 5.82 6:32 4.74 3.30 2.90 3.03

TEMPERATURE DEGC 138.00 132.50 148.06 142.00 133.65147.0

0135.50 144.60 151:80

152.50

16.

AMBIENT CONDITIONS

DRY BULB TEMP DEGC 28.00 34.00 34.00 34.00 34.00 34.00 34.00 40.00 40.00 40.00

WET BULB TEMP DEGC 0.00

RELATIVE HUMIDITY % 0.00 52.00 52.00 61.50

MOISTURE LOAD (/100)# KG/KG 2.50 2.50 2.50 2.50 2.50 2.50 2.50 2.50 2.50 2.50

17.

PROXIMA TE ANAL YSIS OF COAL

FIXED. CARBON % 32.54 8.14 33.29 37.12 32.11 32.44 30.71 24.17 30.57 30.85

VOLATILE MATTER % 21.46 24.05 24.10 23.11 22.34 22.43 22.53 24.21 24.84 24.35

TOTAL MOISTURE % 10.00 13.'60 13.85 12.70 12:65 12.40 13.00 11.66 10.68 11.25

ASH % 32.00 24.21 28.76 27.00 32.90 32.73 33.76 39.96 33.91 33.51

G C V OF COALKCAUK

G4300.00 4597.00 4090.00 4450.00 3986.00

4018.00

3863.00 3502.00 3955.003973.

00

18.

ULTIMATE ANALYSIS OF COAL

CARBON (C) % 45.00 49.08 44.07 47.71 42.81 43.16 41.53 37.16 42.45 42.60

HYDROGEN (H) % 2.82 3.18 2.99 3.09 2.91 2.93 2.88 2.91 3.03 3.02

MINERAL MATTER % 32.00 24.21 28.76 27.00 32.90 32.73 33.76 39.96 33.91 33.51

NITROGEN (N) % 0.95 1.81 1.81 1.82 1.83 1.83 1.83 1.81 1.80 1.81

SULPHUR (S) % 0.38 0.38 0.38 0.38 0.38 0.38 0.38 0.38 0.38 0.38

MOISTURE (H2O) % 10.00 13.60 13.85 12.70 12.65 12.40 13.00 11.66 10.68 11.25

OXYGEN (02) [Balance] % 8.85 7.74 8.13 7.31 6.51 6.57 6.62 6.12 7.74 7.44

BOILER HEAT LOSSES PROFILE

S. No

Operating Parameters Unit Design Trial1 Trial2 Trial3 Trial4 Trial5 Trial6 Trial7 Trial8 Trial9

A. HEAT INPUT TO BOILER KCal/Hr 4422.885411.5

44756.66

5249.07

4141.51

4134.45

4744.31

3749.66

4418.70

4469.69

B.HEAT LOSSES IN THE SYSTEM :

i) UNBURNTS IN ASH

BOTTOM ASH % 0.19 0.33 0.44 0.31 0.38 0.26 0.39 0.35 0.28 0.24

ECO/APH ASH % 0.02 0.27 0.28 0.13 0.08 0.10 0.21 0.16 0.15 0.10

FLY ASH % 0.20 1.06 0.82 1.17 0.62 0.71 1.22 0.69 0.60 0.34

ii) SENSIBLE HEAT IN FLUE GAS

% 4.67 4.15 5.00 4.64 4.91 5.79 4.59 4.27 4.51 4.59

iii) MOISTURE IN FLUE GAS

% 5.20 5.73 6.28 5.71 6.09 6.08 6.29 6.74 6.01 6.06

iv) MOISTURE IN COMB. AIR

% 0.20 0.16 0.21 0.17 0.19 0.21 0.18 0.19 0.17 0.20

v) RADIATION & UNACCOUNT

& 0.85 0.85 0.85 0.85 0.95 0.95 0.85 1.25 1.25 1.25

TOTAL LOSSES % 11.33 12.54 13.88 12.97 13.22 14.10 13.73 13.65 12.9812.7

7

C.

BOILER EFFICIENCY (100 - TOTAL LOSSES)

% 88.67 87.46 86.12 87.03 86.78 85.90 86.27 86.35 87.0287.2

3

D.EXCESS AIR % 23.53 22.09 25.07 23.53 38.34 43.05 29.15 18.64 16.02

16.86

E. OVERALL HEAT RATE

KCal/kWh

2211.44

2788.45

2439.94

2734.17

2701.04

2699.61

2551.80

2254.76

2432.27

2473.

95

STATEMENT OF BOILER EFFICIENCY A Comprehensive Statement of as run

Boiler Thermal Efficiency presenting the Boiler Load, Heat Balance, Thermal Efficiency and Overall Heat Rate for the nine trials conducted is presented in following tables:'

SUMMARY STATEMENT OF BOILER EFFICIENCY

S.No

Parameters UnitsDesign

Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 Trial 6 Trial 7 Trial 8 Trial 9

1 DATE

2 DURATION HRS0900-1300

1445-1845

0915-1315

1015-1415

1500-1900

1915-1315

1430-1830

1430-1830

1430-1830

3 POWER GENERATION MW 200 194.07 194.95 191.98 153.33 153.15 185.92 166.3 181.67 180.67

4 % LOAD % 100 97.04 97.48 95.99 76.67 76.58 92.96 83.15 90.84 90.34

5 G C V OF COALKCAUK

G4300 4597 4090 4450 3986 4018 3863 3502 3955 3973

6 FLUE GAS TEMP. AFTER APH DEGC 138 132.5 148.06 142 133.65 147 135.5 144.6 151.8 152.5

7 % EXCESS AIR %23.5

322.09 25.07 23.53 38.34 43.05 29.15 18.64 16.02 16.86

8 HEAT LOSSES IN THE SYSTEM

i) UNBURNTS IN ASH

BOTTOM ASH % 0.19 0.33 0.44 0.31 0.38 0.26 0.39 0.35 0.28 0.24

ECO/APH ASH % 0.02 0.27 0.28 0.13 0.08 0.1 0.21 0.16 0.15 0.1

FLY ASH % 0.2 1.06 0.82 1.17 0.62 0.71 1.22 0.69 0.6 0.34

ii) SENSIBLE HEAT IN FLUE GAS % 4.67 4.15 5.00 4.64 4.91 5.79 4.59 4.27 4.51 4.59

iii) MOISTURE & HYDROGEN IN FUEL

% 5.2 5.73 6.28 5.71 6.09 6.08 6.29 6.74 6.01 6.06

iv) MOISTURE IN COMB. AIR % 0.2 0.16 0.21 0.17 O 19 0.21 0.18 0.19 0.17 0.2

v) RADIATION & UNACCOUNTED % 0.85 0.85 0.85 0.85 0.85 0.85 0.85 1.25 1.25 1.25

TOTAL LOSSES %11.3

312.54 13.88 12.97 13.22 14.10 13.73 13.65 12.98 12.77

9 BOILER EFFICIENCY %88.6

787.46 86.12 87.03 86.78 85.90 86.27 86.35 87.02 87.23

10 OVERALL HEAT RATE

KCal/kWh

2211.

44

2788.45 2439.94 2734.17 2701.04 2699.61 2551.802254.7

62432.27 2473.95

DISCUSSION:

The Controllable losses, include Sensible heat lost in Dry flue gases & Unburnts in Carbon (in Fly ash, Bottom ash and Economiser / APH hopper ash) account for 5.08% of Overall Input heat to Boiler or 44.80% of the Total Heat losses. The losses due to Radiation, Moisture & Hydrogen in Coal and Moisture in Combustion air account for the uncontrollable losses.

Trial findings indicate the range of total losses to be as under

Total losses in Boiler

  Range (%) Average (%)

Unit data 12.54 to 14.1 13.32

Design 11.33

Share of controllable losses in total

  Range (%) Average (%)

Unit data 5.27 to 6.86 6.00

Design 5.08

SENSIBLE HEAT LOSS IN DRY FLUE GASES Heat losses in Dry flue gases, are characteristically influenced by Excess Air Quantity and Exit Flue Gas Temperature, which in turn, are variant with, Coal Quality (GCV, Fineness, Ash content) and Air In leaks. The profile of Sensible heat in Dry flue gases during trials is summarized as under.

  Range (%) Average (%)

Unit data 4.15 to 5.79 4.74

Design 4.67

% loss due to sensible heat in dry flue gases

VARIATION OF SENSIBLE HEAT LOSSES IN DRY FLUE GAS

S. No.

Item Reference Unit Design T1 T2 T3 T4 T5 T6 T7 T8 T9

1 G C V of Coal Kcal Kg 4300 4597 4090 4450 3986 4018 3563 3502 3955 3973

2% of excess air level

% 23.5 22.1 25.1 23.5 38.3 43.1 29.1 18.6 16 16.9

3FGT at APH outlet

°C 138 132.5 148 142 133.6 147 135.5 144.6 151.8 152.5

4% loss due to S.H. in DFG

% 4.67 4.15 5 4.64 4.91 5.79 4.59 4.27 4.51 4.59

EXCESS AIR Excess air is crucial factor in Boiler Thermal

efficiency. Excess Air levels depends to a large extent on variants like, GCV of Coal, Ash Content, Fineness of Pulverized Coal, Moisture in Coal and Air In leaks especially before and after APH.

The Excess Air quantity admitted to Boiler during the trials was seen to vary as under.

  Range (%) Average (%)

Unit data 16.00 to 43.10 25.90

Design 23.50

EXIT FLUE GAS TEMPERATURE

The flue gas temperature after Air pre heater is a key Factor affecting Boiler Efficiency

  Range (%) Average (%)

Unit data 132.5 to 152.5 143.1

Design 138.0

INLEAK AIR In leak Air, especially in the Air Preheated Flue gas

path, has the detrimental effects of reducing heat Transfer Effectiveness of APH, shifting the draft levels in the Flue gas path and increasing ID Fan duty in terms of Capacity

 % In leak Range Across

APH

% In leak Range from APH to ID Fan in

Unit data 4.73 to 16.94 9.41 to 21.40

Continuous upkeep of APH Seals, Monitoring and Strict control of Inleak Air is recommended, to minimize the Inleak Air quantities and losses thereof

AIR PROFILE IN FLUE GAS PATH AND AIR INLEAK ASSESSMENT

S. No.

Item Reference Unit T1 T2 T3 T4 T5 T6 T7 T8 T9

1 O2 APH-A in % 2.68 3.50 3.55 5.50 6.18 3.05 2.25 2.96 3.00

2 O2 APH-B in % 2.08 2.18 2.28 4.58 4.95 2.10 2.85 2.83 3.06

3 O2 APH-A out % 4.18 4.85 4.53 6.20 688 5.65 327 3.96 4.10

4 O2 APH-B out % 3.43 3.58 3.48 5.45 5.78 3.93 4.12 3.76 4.03

5 O2 ID Fan-A in % 5.65 6.25 5.83 7.48 7.45 6.25 5.47 5.96 5.83

6 O2 ID Fan-B in % 5.10 4.75 4.98 6.65 6.73 5.20 6.05 5.80 5.66

7 Total air level at APH-A in (Theoretical +Inleak) % 114.60 120.00 120.34 135.48 141.65 116.99 112.00116.41

116.67

8 Total air level at APH -B in (Theoretical +Inleak) % 110.96 111.55 112.15 127.85 130.84 111.11 115.70115.58

117.06

9 Total air level at APH-A in (Theoretical +Inleak) % 124.81 130.03 127.47 141.89 148.67 136.81 118.44123.24

124.26

10 Total air level at APH-B in (Theoretical +Inleak) % 119.49 120.52 119.83 135.05 137.93 122.99 124.41121.81

123.75

11 Total air level at ID Fan-A in (Theoretical +Inleak) % 136.81 142.37 138.39 155.27 154.98 142.37 135.22139.63

138.43

12 Total air level at ID Fan-A in (Theoretical +Inleak) % 132.08 129.23 131.05 146.34 147.11 132.91 140.47138.16

136.90

13 Inleak Across APH-A (wrt APH-A in) % 8.92 8.36 5.92 4.73 4.96 16.94 5.75 5.87 6.51

14 Inleak Across APH-B (wrt APH-B in) % 7.68 8.03 6.85 5.63 5.42 10.69 7.52 5.39 5.72

15 Inleak After APH-A (wrt APH-A in) % 19.38 18.64 14.99 14.60 9.41 21.69 20.7319.9

518.66

16 Inleak After APH-B (wrt. APH-B in) % 19.03 15.85 16.85 14.46 12.43 19.62 21.4019.5

416.95

COAL QUALITY The GCV of Coal, against the design

requirement of 4300 Kcal/Kg was seen to range from 3502 to 4597Kcal/Kg as under, during the trial period

Range (%)

Unit data 3502 to 4597

Design 4300

Ash % in Coal

Increase of Ash Content leads to Increased un burnts, Loss due to Sensible heat in ash, Increased Soot blowing frequency, Increased mill load for same useful output

  % Ash in Coal

  Range (%) Average (%)

Unit data 24.21 to 39.96 31.90

Design 32.00

M & H LOSSES IN FLUE GASES S.

No.

Item Reference Unit Design T1 T2 T3 T4 T5 T6 T7 T8 T9

1 FGT APH out OC 138 132.5 148.06 142 133.65 147 135.5144.0

6151.

8152.

5

2Heat loss in fluegases due to M&H

KCal/Kg 223.6 263.4 256.85 254.1 242.74 244.29242.9

8236.0 237.

240.76

3 M in Coal % 10 13.6 13.85 12.7 12.65 12.4 13 11.66 10.611.2

5

4 H in Coal % 2.82 3.18 2.99 3.09 2.91 2.93 2.88 2.91 3.03 3.02

5 GCV of Coal KCal/Kg 4300 45.97 4090 4450 3986 4018 3863 3502395

53973

6Loss due to M & H in Coal

% 5.2 5.73 6.28 5.71 6.09 6.08 6.29 6.74 6.01 6.06

7Corrected loss due toM & H in Coal

% Ref (5.20) 5.48 5.83 5.49 5.62 5.73 5.84 6.13 5.66 5.71

COAL FINENESS Against the design Coal Fineness requirement of 70%

passing through 200 mesh, the decreased fineness is known to affect the Boiler Efficiency detrimentally through Increased Excess Air requirements as well as Higher percent Unburnts in Ash.

Unit data Fineness rejects across 200 mesh

48 to 63 %

It is our considered opinion that improvements in Mill operations towards achieving rated Coal Fineness should be a prime area of concern. The results would be manifest as reduced Excess Air Losses and Reduced Unburned in Ash Loss.

HEAT LOSS DUE TO UNBURNTS IN ASH

Heat loss due to un burnts in ash is a manifestation of fuel Combustion efficiency and is known to depend upon operational factors like % Ash, Fineness of Coal, Excess Air level, Wind box Pressure, Primary & Secondary Air Distribution and Hot Air temperature, condition of burners, as also Ash fusion temperatures

  Percentage Loss Due to Unburnts in Ash

  Range (%) Average (%)

Unit data 0.68 to 1.82 1.29

Design 0.41

FD AIR FLOW & PA/SA DISTRIBUTION FD Air constitutes one of the influencing factors on Combustion Efficiency. The FD Air flow, Air to Coal ratio, Primary Air flow, Primary Air to Secondary Air ratios and Primary Air to Coal ratio during all the Boiler trials are assessed, vis-a-vis the design values for the Boiler and the findings indicate satisfactory performance levels in all these respects. The findings are presented in following tables.

F.D. AIR FLOW INDICATORS

S. No.

Item Reference Unit Design

T1 T2 T3 T4 T5 T6 T7 T8 T9

1 Total Air Flow TPH725.

4773.9 769.3 738.5 726.3 691.4 743.8 598.5 615.4 703

2Total Air to Coal Ration

Kg/Kg 7 6.56 6.6 6.25 6.78 6.7 6 5.58 5.5 6.24

3 Mills Run 5A,B,D,

E,F

A,B,D,E, F

ABC D,F

AB,DF

A,B,D,F

BC,D,E,F

A,B.C 0 F

A.B C,D,F

A,B,C,D F

4 Primary Air Flow TPH 216.2 232.9 233.5 241 198 201246.3

5229 222 229.3

5 Secondary Air Flow TPH 509.2 541 535.8 497.5508.

3490.

4497.5 369.4 393.4 473.7

6 Primary Air Flow % 29.8 30.1 30.4 32.6 28.1 29.1 33 38 36 32.6

7 Secondary Air Flow % 70.2 69.9 69.6 . 67.4 "71.9 70.9 67 62 64 67.4

8Primary Air to Coal

RatioKg/Kg 2.09 1.97 2 2.04 1.9 1.95 2 2.13 1.98 2.03

WIND BOX PRESSURE

Wind Box pressure is known to be one of the key factors affecting Combustion Efficiency. Trial findings indicate the actual Wind Box pressure to be less than 50 mmWC as against 160 mmWC design value.

Significant power savings potential exists in FD Fans by incorporating Variable speed drives, etc

SECONDARY AIR TEMPERATURE Combustion Efficiency is closely linked with temperature of

Secondary Air and effects of temperature drop (Secondary Combustion Air) are normally manifest as commensurate

rise in % Unburnts in Ash.

  Range (OC) Average (OC)

Unit data 210.9 to 240.0 225.0

Design 263.0

The Secondary Air temperature being lower from design value is expected to effect

Mill performance in terms of Moisture removal and final Coal Output Fineness

Unburnts in Ash

The main influencing factor for low Secondary Air temperature is felt to be the lower Flue Gas temperature at APH inlet as shown below

  Range (OC) Average (OC)

Data 241.0 to 290.0 270.0

Design 337.0

Focus areas for improvement are felt to be

Wind Box pressure APH Effectiveness (Inleak Air at APH inlet) Coal Mill performance

Thank you