Ash Deposition and Shedding in Straw and Wood Suspension … · Fly Ash Elemental Composition...
Transcript of Ash Deposition and Shedding in Straw and Wood Suspension … · Fly Ash Elemental Composition...
Ash Deposition and Shedding in Straw and Wood
Suspension-Fired Boilers :
Full-scale Measurements
Student: Muhammad S. BashirSupervisors: Professor Kim Dam-Johansen
Asso. Prof. Peter A. JensenAsso. Prof. Flemming FrandsenAsso. Prof. Stig Wedel
CHEC Research Centre, Technical University of Denmark
DTU Chemical Engineering Technical University of Denmark
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•Background
•Experiments• Experimental Objectives
• Materials and Methods
•Results and Discussion• Experimental Set Up
• Quantification of Deposit Buildup
• Deposit Shedding using Artificial Sootblowing
• Elemental Release of Major Ash Components
•Conclusions/Experimental Findings
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Presentation Outline
DTU Chemical Engineering Technical University of Denmark
Ash Deposition during Biomass Combustion
L. Tobiasen et al; Fuel Processing Technology, 88 (2007) 1108-1117.
Biomass (straw) K, Cl, S
Increased risk of fouling/slagging on heat exchange surfaces.
AMV2Superheater Region
Background Experiments Results and Discussion Conclusions Acknowledgment
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Boiler Configuration : AMV1
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Parameter AMV1
Capacity(wood, straw)
350, 320 MWth
Wood, Straw pellets
(full load)
20 kg/s
Steam DataSuperheater (oC) 540
Background Experiments Results and Discussion Conclusions Acknowledgment
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Boiler Configuration : AMV2
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Parameter AMV2
Capacity(wood, straw) 250 MWth
Wood, Straw pellets(full load) 60 t/h
Steam DataSuperheater (oC) 480
Background Experiments Results and Discussion Conclusions Acknowledgment
DTU Chemical Engineering Technical University of Denmark
Experiments
• Measurement of extent of boiler fouling/slagging by meansof an ash deposition/shedding probe.
• Influence of fuel type, boiler load, probe metaltemperature and probe exposure time on deposition rate,heat uptake and deposit characteristics.
• Investigation of PIP needed to remove the deposits ofdifferent exposure time and probe surface temperature.
• Investigation of residual ash and deposits chemistry.
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Background Experiments Results and Discussion Conclusions Acknowledgment
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Deposition/Shedding Probe
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600
Background Experiments Results and Discussion Conclusions Acknowledgment
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Experimental Setup Description (AMV 1)
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Background Experiments Results and Discussion Conclusions Acknowledgment
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Experimental Resume : AMV2
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Test No. 1 3 2 4 5
Straw (%) 35 65 80 100 0
Ash (%) 4.21 4.99 5.38 5.85 3.3
Probe Temp. (oC) 500 500 500 500 500
Exposure Time(h)
90 72 124 76 24
Boiler Load (%) 46 63 50 53 52
Background Experiments Results and Discussion Conclusions Acknowledgment
DTU Chemical Engineering Technical University of Denmark
Experimental Resume : AMV1
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Test No. 1 2 3 5 4
Straw (%) 80 65 35 50 50
App. Ash (%) 5.2 4.0 2.4 3.4 3.4
Probe Temp. (oC) 500 600 500500
(600)500
Exp. Time (h) 56 45 185 168 73
Boiler Load 66 57 62 64 86
Oil Share (%) 12.9 13.5 2.4 7.1 4.8
Background Experiments Results and Discussion Conclusions Acknowledgment
7 6 8
0-10 0-10 0-10
1.0 1.0 1.0
550 550 550
335 434 212
62 60 60
2.7 5.3 6.9
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AMV1: Primary Data (120 s): 50 % Straw (flue gas: 843 oC)
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0 20 40 60 80 100 120 140 160 180600
800
1000
Time [h]
Gas
Tem
p.(o C)
Thermocouple
0 20 40 60 80 100 120 140 160 1800
5000
10000
Time [h]
(g/m
2 )
Weight Uptake
0 20 40 60 80 100 120 140 160 1800
50
100
Time [h]
(kW
/m2 )
Heat Uptake0 20 40 60 80 100 120 140 160 180
80100120
Soot
blow
er
0 -185 h (500)
Background Experiments Results and Discussion Conclusions Acknowledgment
Actual flue gas temp. (suction pyrometer, Qualitative trend is same as of thermocouple)
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AMV1: Primary Data (120s): 50 % Straw (avg. flue gas: 880 oC)
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0 20 40 60 80 100 120 140 160600
800
1000
Time [h]
Gas
Tem
p.(o C)
Thermocouple
0 20 40 60 80 100 120 140 1600
1
2 x 104
Time [h]
(g/m
2 )
Weight Uptake
0 20 40 60 80 100 120 140 1600
40
80
Time [h]
(kW
/m2 )
Heat Uptake0 20 40 60 80 100 120 140 160
80100120
Soot
blow
er
0 -30 h (500) 30 -94 h (600) 94-145 h (500) 145 -168 h ( 600)
Background Experiments Results and Discussion Conclusions Acknowledgment
Actual flue gas temp. (suction pyrometer, Qualitative trend is same as of thermocouple)
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Flue Gas Temperature and Heat Uptake
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500 550 600 650 700 750 800 850 900 9500
10
20
30
40
50
60
70
80
90
100
Gas Temp.(oC)
(kW
/m2 )
y = 0.1247*x - 55.35
Heat Uptake linear
500 550 600 650 700 750 800 850 900 9500
10
20
30
40
50
60
70
80
90
100
Gas Temp.(oC)
(kW
/m2 )
y = 0.1427*x - 70.12
Heat Uptake linear
500 550 600 650 700 750 800 850 900 9500
10
20
30
40
50
60
70
80
90
100
Gas Temp.(oC)
(kW
/m2 )
y = 0.06928*x - 29.89
Heat Uptake linear
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Background Experiments Results and Discussion Conclusions Acknowledgment
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Brief Results of Tests
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Test No. 1 2 3 5 4
Straw (%) 80 70 50 50 30
Ash (%) 5.0 4.3 3.4 3.4 3.0
Probe Temp. (oC) 500 600 500500
(600)500
Exp. Time (h) 56 45 185 168 73
Boiler Load 66 57 62 64 86
Oil Share (%) 12.9 13.5 2.4 7.1 4.8
Flue Gas Temp.Mean (oC)
852 821 843 880 918
Weight Uptake Final (kg/m2)
3.78 4.95 3.07 16.26 7.34
Heat Uptake Mean(kW/m2)
34 21.1 35.0 23.3 41.1 14
Background Experiments Results and Discussion Conclusions Acknowledgment
7 6 8
10 5 0
1.0 0.8 0.7
550 550 550
335 434 212
62 60 60
2.7 5.3 6.9
774 724 788
1.95 1.82 --
-- 24.0 --
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Overall Comparison of Weight Uptake of Different Full Scale Measurements (45 h)
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Boiler Fuel AnalysisProbe
Temp.
Flue gas
Temp.
Final WeightSignal
Ref.
Tests Ash K Cl oC oC kg/m2
Avedøre Test 1 5.5 0.69 0.32 500 1020 9.50 [11]
Avedøre Test 2 4.7 0.92 0.35 500 784 1.50 [6]
Amager Unit 2 (Test 4)
5.9 0.83 0.40 500 830 1.70
Amager Unit 1 (Test 1)
5.0 -- -- 500 852 2.20
Amager Unit 1 (Test 3)
3.4 -- 0.25 500 843 0.45
Amager Unit 1 (Test 4)
3.0 -- -- 500 918 4.90
Background Experiments Results and Discussion Conclusions Acknowledgment
Amager Unit 1 (Test 2)
4.3 -- -- 600 821 4.95
Amager Unit 1 (Test 5)
3.4 -- -- 600 880 9.60
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Overall Comparison of Weight Uptake of Different Full Scale Measurements (72-77 h)
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Boiler Fuel AnalysisProbe
Temp.
Flue gas
Temp.
Final WeightSignal
Ref.
Tests Ash K Cl oC oC kg/m2
Avedøre Test 1 5.5 0.69 0.32 500 1022 15.0 [11]
Avedøre Test 2 4.7 0.92 0.35 500 784 2.40 [6]
Amager Unit 2 (Test 4)
5.9 0.83 0.40 500 830 1.67
Amager Unit 1 (Test 3)
3.4 -- 0.25 500 843 1.01
Amager Unit 1 (Test 4)
3.0 -- -- 500 918 7.34
Background Experiments Results and Discussion Conclusions Acknowledgment
Amager Unit 1 (Test 5)
3.4 -- -- 600 880 10.0
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Ash Deposit Removal using Artificial Sootblowing Probe (Example: Test 3 (500))
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60 70 80 90 100 110 120600
800
1000
Time [h]
Gas
Tem
p.(o C
)
Thermocouple60 70 80 90 100 110 120
600
800
1000
(o C)
Suction Pyrometer
60 70 80 90 100 110 1200
5000
10000
Time [h]
(g/m
2 )
Weight Uptake
60 70 80 90 100 110 1200
40
80
Time [h]
(kW
/m2 )
Heat Uptake60 70 80 90 100 110 120
80100120
Soo
tblo
wer
Shedding through artificial sootblowingShedding through plant sootblowing
Background Experiments Results and Discussion Conclusions Acknowledgment
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Artificial Deposit Removal: Image Analysis
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Weight Signal : 8747.18 g/m2 Weight Signal : 1584.83 g/m2
Probe Exposure Time : 91.2 hFlue gas temperature : 825 CTarget Probe Temperature : 500 oC
Straw Share : 50 %Boiler Load : 65 %
Background Experiments Results and Discussion Conclusions Acknowledgment
Image Before Deposit Removal
Image After Deposit Removal
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Air Pressure and PIP
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Background Experiments Results and Discussion Conclusions Acknowledgment
0
50
100
150
200
250
300
0 50 100 150 200 250 300 350 400 450 500
PIP
(kPa
)
Air Pressure (kPa)
20 cm 15 cm 13 cm 11 cm 9 cm 7 cm 5 cm
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Impact of Probe Exposure Time and Temperature on Deposit Removal
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Background Experiments Results and Discussion Conclusions Acknowledgment
0,1
1,0
10,0
100,0
0 50 100 150 200 250
% D
epos
it R
emov
ed
PIP (kPa)
500 oC (Probe Temperature)
30 h (1695 g/m2) 72 h (7100 g/m2) 91 h (9090 g/m2)
120 h (12750 g/m2) 144 h (15006 g/m2)
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Impact of Probe Exposure Time and Temperature on Deposit Removal
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Background Experiments Results and Discussion Conclusions Acknowledgment
0,1
1,0
10,0
100,0
0 50 100 150 200 250
% D
epos
it Re
mov
ed
PIP (kPa)
600 oC (Probe Temperature)
46 h (4494 g/m2) 76 h (500 C for initial 30 h) ( 11123 g/m2)
95 h (14024 g/m2) 167 h (17850 g/m2)
DTU Chemical Engineering Technical University of Denmark
Fly Ash Elemental Composition (AMV2)
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Background Experiments Results and Discussion Conclusions Acknowledgment
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10
20
30
40
50
60
10*Al2O3 10*Fe2O3 10*MgO 10*Na2O K2O P2O3 CaO SiO2 SO3 Cl
Com
posit
ion (
wt.
%)
Grate boiler (Fuel ash) Grate boiler (Fly ash) Suspension boiler (Fuel ash) Suspension boiler (Fly ash)
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Deposit Elemental Composition (AMV2)
0,0
5,0
10,0
15,0
20,0
25,0
30,0
Al Ca Fe K Mg Na P Si S Cl
wt %
Elements
35% Straw (Front Upper Layer)
100 % Straw (Upper Front Layer)
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Background Experiments Results and Discussion Conclusions Acknowledgment
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Preliminary Conclusions
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Deposits are more sintered in the windward directionduring pure straw-firing.
Deposits and fly ashes obtained during suspension-firingcontain significant amounts of Ca and Si.
The final deposit weight uptake is not higher compared tobiomass grate-firing at almost similar conditions.
Background Experiments Results and Discussion Conclusions Acknowledgment
DTU Chemical Engineering Technical University of Denmark
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Preliminary Conclusions
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Image analysis reveal that deposit shedding is primarilythrough debonding.
Deposits of less than 91 h exposure time are easy toremove and PIP needed is less than 55 kPa at 500oC temp.
With increase in probe surface temperature from 500 to600 oC, PIP needed to remove the deposits increases.
Natural shedding is possible at higher flue gastemperatures (> 940 oC), but temperature needs toremain higher as lower temperature fluctuations are nothelpful.
Background Experiments Results and Discussion Conclusions Acknowledgment
DTU Chemical Engineering Technical University of Denmark
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Acknowledgment
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• Dr. Johan Wadenbäck/Søren Thaaning., Vattenfall A/S
• Energinet.dk for PSO project funding
Background Experiments Results and Discussion Conclusions Acknowledgment
Questions?
Many Thanks!
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