Ash Formation and Partitioning in a Cyclone Fired...
Transcript of Ash Formation and Partitioning in a Cyclone Fired...
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Ash Formation and Partitioning in a Cyclone Fired Boiler
Steven A. Benson, Shuchita Patwardhan, and Art Ruud Microbeam Technologies Inc.
Andrew Freidt, Minnkota Power Cooperative
Jodey Houn, BNI Coal Ltd
Junior Nasah, University of North Dakota, Institute for Energy Studies
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Overview Background Project goal Field testing/sampling Coal, slag, entrained ash properties Partitioning of fuel impurities
between cyclone and fly ash Conclusions
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Minnkota MRY Plant Unit 1, 250 MW, 1970 Unit 2, 460 MW, 1977 Fired with lignite from ND 95% availability Ranked among lowest cost electricity producer in US
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Challenges Lignite variability Clay minerals Alkali and alkaline earth elements organically
associated
Slag freezing in cyclones Convective pass fouling Fine particulate
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Ash Behavior Indices
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Slag Flow Characteristics by Seam
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CCSEM (Wt% Minerals, Mineral Basis)BNI # 41-132HB 41-144KC 41-144 HA 41-144HB 41-168 KC 41-168 HA 41-168 HB 41-180 KC 41-180 HA 41-180 HB 41-192 KC 41-192 HA
Total Quartz Content
3.1 17 18.8 9.8 30.3 8.7 8.8 11.4 20 3.9 15 17.4
Quartz < 10 microns
2 10.8 9.7 6.4 24.6 4.4 4 6.8 3.3 2.6 9.7 12.7
Total Kaolinite Content
5.8 10.6 16.7 10.8 7.7 6.4 1.7 9.5 4.4 2.4 14.3 28
Kaolinite Content < 10 microns
2.6 5.1 8.4 6.3 4.5 2.6 0.9 4.8 1.1 0.9 10.2 20.8
Total Montmorillonite
1.8 10.7 6 2.7 6.5 1.7 6.1 7 2.3 2.4 7.6 5.1
Total Illite 10.2 14.1 0.7 9.3 6.6 0.2 28 19.1 10.2 1.6 6.8 1.9Total Pyrite 45.4 8 28.7 26.7 18.9 67.1 19.7 9.1 10.9 57.2 22.6 32.3
Pyrite Content < 10 microns
8.9 4.5 3.5 10.5 2.8 9.8 4.7 2.5 2.5 17 6.6 7
Gypsum Content 10.6 6.5 0.6 0 1.6 2.7 0.8 5.4 0 16.1 2.2 0
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Relationship to Slag Freezing
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1
2
3
4
5
0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00
Illite and Montmorillonite, lb/mBTU
Freezing
Good flow
Poor flow
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Ash Content and Cyclone Performance
0
5
10
15
20
25
30
35
40
45
0818
98 1
108
1898
13
0818
98 1
508
1898
17
1202
98 0
112
0298
09
1202
98 1
712
1598
07
1215
98 0
712
1598
07
1215
98 0
712
2698
07
1226
98 0
512
2798
19
1227
98 1
712
2798
15
0116
99 0
901
1699
09
0116
99 0
904
0699
09
0406
99 1
504
0699
21
0407
99 0
305
0499
15
0506
99 0
505
0599
07
0505
99 0
905
0499
17
0506
99 2
107
1199
21
0710
99 0
507
1299
09
0710
99 1
107
1299
21
0710
99 1
707
1399
09
Date
Ash
(moi
stur
e fr
ee)
5400
5600
5800
6000
6200
6400
6600
6800
7000
7200
Cyc
lone
Per
form
nace
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Base/Acid Ratio and Cyclone Performance
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
0818
98 1
108
1898
15
0818
98 1
9
0818
98 2
3
1202
98 0
912
0298
19
1201
98 2
3
1215
98 2
1
1215
98 2
312
1698
01
1216
98 0
3
1227
98 0
5
1227
98 0
512
2798
05
1227
98 0
5
0116
99 0
1
0116
99 0
301
1699
05
0406
99 0
7
0406
99 1
5
0406
99 2
304
0799
07
0504
99 2
1
0506
99 1
3
0505
99 1
705
0599
21
0505
99 1
1
0710
99 1
5
0713
99 0
907
1199
01
0714
99 0
5
0711
99 1
7
0710
99 0
507
1299
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Date
Base
/Aci
d
5400
5600
5800
6000
6200
6400
6600
6800
7000
7200
Cycl
one
Perfo
rman
ce
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Coal Sorting and Blending Criteria
Base-Acid RatioB/A= (CaO+MgO+Na2O+FeO+K2O)/(SiO2+Al2O3+TiO2)
Ash Content
Optimum coal for maintaining good slag flow Base-to-acid ratio > 0.6 to 0.7 Ash content < ~17 % (mf basis)
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Variability Challenge - Coal Mining and Blending
Three Seams
Upper – Low B/AHigh ash
Middle – moderate to high B/A,
moderate ash
Lower – High B/ALow ash high Na
PGNAA - elemental analysisAsh and moisture
meters
High B/ALow Ash
Moderate B/AModerate Ash
Low to ModerateB/A
High Ash
Low B/AHigh Ash
PGNAA - reclaimed coal from building
Transferred to Silos
Coal BuildingCoal Mine
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Goal To determine partitioning process
between slag and fly ash as a function of the inorganic composition of the lignite enable more accurate prediction of the slag
flow behavior, entrained ash composition, ash deposition on heat transfer surfaces, and fine particle properties.
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Plan – Unit 2 Test coals with three different B/A ratios.
High B/A Medium B/A Low B/A
Test each coal under 4 different O2 conditions. Sampling of coal, slag, ash and perform boiler
observations at each set of conditions.
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FIELD TEST UNIT 2• Coal Sampling• Boiler Operating Parameters• NOx Levels• Particulate Loadings – Dekati Impactor/bulk filter• ESP Hopper samples • Slag samples
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Field Test Matrix
Day Conditions Coal –as
fired
Slag Fly Ash Dekati
ESP Hopper
BoilerObservations
Day 1 Baseline x x x x x
Day 2 Med B/A x x x x x
Day 3 High B/A x x x x x
Day 4 Low B/A x x x x x
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Diagram of processes and tools
Coal Properties Cyclone – Ash partitioning
Entrained Ash
Coal Air Vent
Slag
Transport to water wall Slagging
Transport toConvective pass
surfaces
High temperature fouling – silicate
based
Low temperature fouling – sulfate
based
Slag flow
ESP particle capture –
resistivity and cohesivity
Boiler operating parameters – air
flow
Over fire air
Tools
Inputs/processes
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Schematic of Sampling Locations
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Sample AnalysisNo. Sample description Analysis
1 As-fired coal samples Proximate/Ult analysis, Ash composition, CCSEM
2 Slag samples Morphology/Composition/SEMPC
3 ESP Hopper samples Morphology/Composition/CCSEM
4 Dekati Fly Ash Samples Morphology/Composition
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Coal Analysis
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Coal analysis – Prox/Ult resultsDescription Total Moisture
Ash As Received
Volatile Matter As Received
Fixed Carbon As Received
BTU/lb As Received
Total Sulfur As Received
Carbon As Received
Hydrogen As Received
Nitrogen As Received
Coal As-fired D1 27.37 9.84 32.73 30.06 7627 0.95 47.26 6.23 0.73
Coal As-fired D2 28.65 9.40 32.87 29.08 7488 1.06 46.84 6.33 0.71
Coal As-fired D3 28.27 9.36 32.95 29.42 7616 1.10 47.53 6.29 0.73
Coal As-fired D4 27.75 12.12 32.12 28.01 7348 1.08 45.85 6.20 0.72
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Coal analysis – Ash composition results(Weight percent equivalent oxide)
Description Silicon DioxideAluminum
DioxideTitanium Dioxide Iron Oxide
Calcium Oxide
Magnesium Oxide
Potassium Oxide
Sodium Oxide P2O5
Coal As fired D1 39.81 14.71 0.63 11.47 16.61 5.44 1.81 8.09 0.12
Coal As fired D2 40.22 13.18 0.68 12.61 17.63 5.41 1.59 7.13 0.11
Coal As fired D3 37.65 12.58 0.65 14.28 18.94 5.53 1.41 7.24 0.13
Coal As fired D4 46.93 14.47 0.75 9.93 13.96 4.53 2.06 5.79 0.13
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B/A ratio – As fired coal – Unit 2
Description B/A Ratio Description
Coal As fired D1 0.79 Baseline operation
Coal As fired D2 0.82 Med B/A
Coal As fired D3 0.93 High B/A
Coal As fired D4 0.58 Low B/A
0.79 0.82
0.93
0.58
0.000.100.200.300.400.500.600.700.800.901.00
Coal As fired D1 Coal As fired D2 Coal As fired D3 Coal As fired D4
B/A Ratio
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Viscosity temperature – As fired coal
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
1200 1400 1600 1800 2000 2200 2400
Vis
cosi
ty, L
og1
0P
oise
Temperature, °F
Coal As fired D1 Coal As fired D2 Coal As fired D3 Coal As fired D4
T250 - flow begins
molten liquid
Day 4 Low B/ADay 3 High B/ADay 2 Med B/A
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CCSEM – Day 2 Composite Coal
1.24.6
2.4 4 1.53.31.4
6.5
3
5
2.8
8.6
0.6
1.7
2.2
4.7
3.2
15.3
0.1
0.2
0.1
0.4
0.4
4.3
2.2
4.6
1.8
2.8
1.2
5.3
0.7
0.7
0.3
0.7
0.3
0.9
0
5
10
15
20
25
30
35
40
1.0 - 2.2 2.2 - 4.6 4.6 - 10.0 10.0 - 22.0 22.0 - 46.0 46.0 - 400
Wei
ght
perc
ent,
min
eral
bas
is
Size Bin, µm
Others Unclassified Iron Oxide Pyrite/Pyrrhotite/Oxidized Pyrrhotite Silicate Minerals Quartz
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CCSEM – Day 3 Composite Coal
2.9
11.5
2.7 4.10.9
3
4.1
9.7
3.94.9
1.5
5.60.3
1.4
1.3
2.3
2.3
13.5
0.2
0
0.3
0.9
0.4
3.5
2.3
3.8
1.5
2
1.1
2
0.8
2.4
0.4
0.7
0.3
0.8
0
5
10
15
20
25
30
35
1.0 - 2.2 2.2 - 4.6 4.6 - 10.0 10.0 - 22.0 22.0 - 46.0 46.0 - 400
Wt
% M
iner
al B
asis
Size bin, µm
Others Unclassified Iron oxide Pyrite/Pyrrhotite/Oxidized Pyrrhotite Silicate Minerals Quartz
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CCSEM Day 4 – Composite Coal
2.4
5.83 4.3
1.2 1.8
3.5
7.1
5.4
7.7
3.1
100.3
0.4
1.3
3.9
2
4.6
0
0.2
0.2
1.4
0.4
2.7
2.5
3.2
2.9
4
1.4
4.8
1.4
1.9
1.2
2.4
0.7
0.8
0
5
10
15
20
25
30
1.0 - 2.2 2.2 - 4.6 4.6 - 10.0 10.0 - 22.0 22.0 - 46.0 46.0 - 400
Wt%
, Min
eral
Bas
is
Size bin, µm
Others Unclassified Iron Oxide Pyrite/Pyrrhotite/Oxidized Pyrrhotite Silicate Minerals Quartz
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Slag Samples Analysis
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Slag samples analysis resultsWt% equivalent oxide
Normalized Na2O MgO Al2O3 SiO2 SO3 K2O CaO TiO2 Fe2O3 BaO
D1C1 4.47 4.61 12.24 42.75 0.25 1.23 21.20 0.66 11.61 0.82
D2C1 5.15 5.32 12.27 42.03 0.18 0.88 22.73 0.56 9.83 0.88
D3C1 3.89 4.57 9.51 33.54 0.31 0.68 30.13 0.53 15.32 1.29
D4C1 3.49 3.65 11.07 46.78 0.23 1.39 19.60 0.62 11.80 1.25
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Fly Ash Entrained Ash – Dekati Mass Composition by size
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Dekati data – Total mass loadings
4.00E+05
2.76E+05
3.82E+05 3.85E+05
5.28E+05
6.96E+05
4.62E+05
5.71E+05
6.70E+05
5.93E+05
4.49E+05
5.17E+05
5.65E+05
4.17E+05
0.00E+00
1.00E+05
2.00E+05
3.00E+05
4.00E+05
5.00E+05
6.00E+05
7.00E+05
8.00E+05
D1C1 D2C1 D2C2 D2C3 D2C4 D3C1 D3C2 D3C3 D3C4 D3C5 D4C1 D4C2 D4C3 D4C4
Total Loading (µg/dscm)
Day 2 Med B/A Day 3 High B/A Day 4 Low B/A
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Coal-Slag-Fly Ash Comparison
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Day 4 Coal , Slag, Dekati data comparison (wt% equivalent oxide).
Na2O MgO Al2O3 SiO2 P2O5 SO3 K2O CaO TiO2 Fe2O3 BaO
Coal Day 4 5.79 4.53 14.47 46.93 0.13 0.00 2.06 13.96 0.75 9.93 0.98
D4C1 – Slag 3.49 3.65 11.07 46.78 0.00 0.23 1.39 19.60 0.62 11.80 1.25
D4C1 – Dekati 17.05 6.52 4.69 12.54 0.97 27.68 3.13 18.10 0.87 6.01 2.44
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Partitioning
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Partitioning Calculations Coal flow rate Ash content of coal (as received basis) Air flow rate at the inlet Air flow rate at the outlet Total mass loading
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Partitioning Between Slag and Fly Ash
65.6372.80
44.09
67.91
34.3727.20
55.91
32.09
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
90.00
100.00
D1C1 D2C1 D3C1 D4C1
Per
cent
as
slag
or
fly
ash
Fly ash
Slag
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Cyclone Partitioning – Day 2 Coal
Cyclone Wall
Solid Slag
Moderately thick Liquid Slag Layer
Twall
T250=2000 ºF
Slag – moderate viscosity slag –High ash retention – 73%
Low Particle Loading - ~27%
High coal/ash sticking
Coal particles –moderate B/A, low ash
Day 2 – B/A 0.82, Ash 9.4
Vaporization
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Cyclone Partitioning – Day 3 Coal
Cyclone Wall
Solid SlagThin Liquid Slag Layer
Twall
T250= 1900 ºF
Slag – Low viscosity slag –Low ash retention – 44%
High Particle Loading - ~56%
Low coal/ash sticking
Coal particles – high B/A, low ash
Day 3 – B/A 0.93, Ash 9.4
Vaporization
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Cyclone Partitioning – Day 4 Coal
Cyclone Wall
Solid Slag
Moderately thick Liquid Slag Layer
Twall
T250=2200 ºF
Slag – moderate viscosity slag –High ash retention – 50%
Low to moderate Particle Loading - ~50%
High coal/ash sticking coefficient – higher rebound – freezing potential
Coal particles – low B/A, high ash
Day 3 – B/A 0.58, Ash 12.1
Vaporization
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Partitioning Process Transport to cyclone slag
Gas flow rate Size and density of particle
Sticking in the slag Viscosity of the slag layer Slag layer thickness
Volatility of element Association of the element in the coal Element chemical properties
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Questions Thanks to:
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Ash Formation and Partitioning in a Cyclone Fired Boiler�OverviewMinnkota MRY PlantChallengesAsh Behavior IndicesSlag Flow Characteristics by SeamCCSEM (Wt% Minerals, Mineral Basis)Relationship to Slag FreezingAsh Content and Cyclone PerformanceBase/Acid Ratio and Cyclone PerformanceCoal Sorting and Blending CriteriaVariability Challenge - Coal Mining and BlendingGoalPlan – Unit 2 Field Test Unit 2Field Test MatrixDiagram of processes and toolsSchematic of Sampling LocationsSample AnalysisCoal AnalysisCoal analysis – Prox/Ult resultsCoal analysis – Ash composition results�(Weight percent equivalent oxide)B/A ratio – As fired coal – Unit 2Viscosity temperature – As fired coalCCSEM – Day 2 Composite CoalCCSEM – Day 3 Composite CoalCCSEM Day 4 – Composite CoalSlag Samples AnalysisSlag samples analysis results�Wt% equivalent oxideFly AshDekati data – Total mass loadingsCoal-Slag-Fly Ash ComparisonDay 4 Coal , Slag, Dekati data comparison (wt% equivalent oxide).PartitioningPartitioning CalculationsPartitioning Between Slag and Fly AshCyclone Partitioning – Day 2 CoalCyclone Partitioning – Day 3 CoalCyclone Partitioning – Day 4 CoalPartitioning ProcessQuestions