an application of dynamic classifiers in pulverized coal ... · pdf fileinitial loesche coal...
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An Application of Dynamic Classifiers An Application of Dynamic Classifiers in Pulverized Coalin Pulverized Coal--Fired Boilers to Fired Boilers to Enhance Combustion Performance Enhance Combustion Performance
and reduce and reduce NONOxx, CO, and , CO, and Unburned Carbon Unburned Carbon
EmissionsEmissions
Electric Electric PowerPowerGeorgia World Congress CenterGeorgia World Congress CenterAtlanta, GAAtlanta, GAMay 3, 2006May 3, 2006
22
AuthorsAuthors
Kevin L. Dugdale, Loesche Energy Kevin L. Dugdale, Loesche Energy Systems, Ltd., UKSystems, Ltd., UK
David Miller, Power Technology, E.ONDavid Miller, Power Technology, E.ON--UK PLCUK PLC
Robert E. Sommerlad, Loesche Robert E. Sommerlad, Loesche America, Inc.America, Inc.
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Preview of PresentationPreview of Presentation•• EC Large Combustion Plants DirectiveEC Large Combustion Plants Directive
-- NONOxx, SO, SO22, and Particulates by 2008, and Particulates by 2008•• Proposed Solution at RatcliffeProposed Solution at Ratcliffe--onon--Soar Power Soar Power
Station, E.ONStation, E.ON--UK PLCUK PLC-- Combustion Mods Combustion Mods –– Overfire Air and Overfire Air and Dynamic Classifiers Dynamic Classifiers
•• Four 500Four 500--MW Front Wall Fired BoilersMW Front Wall Fired Boilers•• Initial resultsInitial results
-- Dynamic Classifiers and impacts on Dynamic Classifiers and impacts on Unburned Carbon, NOUnburned Carbon, NOxx, and CO, and CO
•• Future PlansFuture Plans
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Compliance Compliance ConsiderationsConsiderations
•• SOSO22 –– Wet scrubbers already in operationWet scrubbers already in operation•• Particulate Particulate –– Electrostatic precipitators Electrostatic precipitators
already in operation and fly ash soldalready in operation and fly ash sold•• NONOxx and LOI Considerations for 2008and LOI Considerations for 2008
–– ~35% Reduction required for ~35% Reduction required for compliance of 0.42 lb/MMBtucompliance of 0.42 lb/MMBtu
–– SCR and new LNBs considered and SCR and new LNBs considered and rejectedrejected
–– OFA selected for NOOFA selected for NOxx and DCs selected and DCs selected for LOIfor LOI
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Installation ProgramInstallation Program
•• Dynamic classifiersDynamic classifiers-- Single DC installed in July 2003 and Single DC installed in July 2003 and testedtested-- Additional 6 DCs installed in Additional 6 DCs installed in Summer 2004 and testedSummer 2004 and tested-- Overfire Air System installed in and Overfire Air System installed in and commissioning in progresscommissioning in progress
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Ratcliffe BoilersRatcliffe Boilers
•• Four 500Four 500--MW Babcock single MW Babcock single furnace, dry bottom, natural furnace, dry bottom, natural circulation boilercirculation boiler
•• Eight B&W 10E10 ring and ball mills Eight B&W 10E10 ring and ball mills normally using six mills for full loadnormally using six mills for full load
•• Two coal outlet pipes per mill with Two coal outlet pipes per mill with each split into 3 smaller pipes each each split into 3 smaller pipes each feeding a Babcock Mark 3 LNB for a feeding a Babcock Mark 3 LNB for a total of 48 burners in 4 rows of 12.total of 48 burners in 4 rows of 12.
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Ratcliffe BoilerRatcliffe Boiler
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Burner & Windbox Burner & Windbox PositioningPositioning
Burner Elevation
Wing Center Center Wing
73’ 6”(top)
G1-3 E4-6 E7-9 G10-12
66’O” B13-15 C16-18 C19-21 B22-24
52’ 0” A25-27 F28-30 F31-33 A34-36
44’ 6”(bottom)
H37-39 D40-42 D43-45 H46-48
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DefinitionsDefinitions
•• ClassifierClassifier is a device that separates is a device that separates coarse and fine coal, allowing fine coal to coarse and fine coal, allowing fine coal to pass, while rejecting the coarse coal for pass, while rejecting the coarse coal for regrindingregrinding
•• Dynamic ClassifierDynamic Classifier is a device with an is a device with an inner rotating cage and outer stationary inner rotating cage and outer stationary vanes, which provides centrifugal and vanes, which provides centrifugal and impinging classificationimpinging classification
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Dynamic Classifier Dynamic Classifier CapabilitiesCapabilities
•• Enhance grinding performanceEnhance grinding performance•• Improve boiler performance (Efficiency and Improve boiler performance (Efficiency and
Slagging/Fouling)Slagging/Fouling)•• Reduce Unburned Carbon and increase fly ash Reduce Unburned Carbon and increase fly ash
salabilitysalability•• Reduce LOI, NOReduce LOI, NOxx, and CO , and CO
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EnhancementEnhancement
Enhancement of grinding performance is Enhancement of grinding performance is achieved by one of three ways:achieved by one of three ways:
•• Increasing fineness and thus reduce Increasing fineness and thus reduce coarse particles,coarse particles,
•• Increasing pulverizer capacity, orIncreasing pulverizer capacity, or•• Increasing both fineness and capacityIncreasing both fineness and capacity
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ImprovementsImprovements
•• Steeper fineness distribution slope angle Steeper fineness distribution slope angle (Rosin(Rosin--Rammler Plot)Rammler Plot)
•• Reduced amount of superfine and of Reduced amount of superfine and of coarse materialcoarse material
•• Reduced internal product recirculationReduced internal product recirculation•• Reduced overReduced over--grinding and reduced wear, grinding and reduced wear,
power absorption and mill vibrationpower absorption and mill vibration•• Reduced differential pressure across the Reduced differential pressure across the
mill and classifier potential for reduced mill and classifier potential for reduced mill gas flowmill gas flow
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FinenessFineness
Dynamic Classifiers can increase fineness Dynamic Classifiers can increase fineness and decrease coarse particles leading toand decrease coarse particles leading to
•• Better burnout (lower Unburned Carbon)Better burnout (lower Unburned Carbon)•• Reduced Slagging and FoulingReduced Slagging and Fouling•• Reduced Excess Air operation resulting inReduced Excess Air operation resulting in
-- Increased boiler efficiencyIncreased boiler efficiency-- Decrease in emissions Decrease in emissions –– NONOxx, CO, CO
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CapacityCapacity
Dynamic Classifiers can increase capacity Dynamic Classifiers can increase capacity while while maintainingmaintaining fineness fineness
•• Applicable to high volatile coals such as Applicable to high volatile coals such as PRB coals where burnout is not a problem PRB coals where burnout is not a problem but where lower heating value, higher ash but where lower heating value, higher ash and moisture content limit the coal and moisture content limit the coal throughputthroughput
•• Increase the blend ratio of PRB where Increase the blend ratio of PRB where higher HHV coals are blended to maintain higher HHV coals are blended to maintain capacitycapacity
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Fineness & CapacityFineness & Capacity
Dynamic Classifiers can increase both Dynamic Classifiers can increase both fineness and capacity, each to a lesser fineness and capacity, each to a lesser degree when each requires incremental degree when each requires incremental increasesincreases
•• Benefits accrue from both fineness and Benefits accrue from both fineness and capacitycapacity
•• Flexibility of operation allows maximum Flexibility of operation allows maximum application of benefits across load rangeapplication of benefits across load range
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Brief History & DevelopmentBrief History & Development
Classification technology R&D Classification technology R&D
underway since 1906, when the underway since 1906, when the
initial Loesche coal mill was initial Loesche coal mill was
patented.patented.
The experiences in grinding coal, The experiences in grinding coal,
petcoke, minerals, cement clinker, petcoke, minerals, cement clinker,
limestone, etc., contributed to the limestone, etc., contributed to the
successful development of the successful development of the
LSKS Dynamic Classifier.LSKS Dynamic Classifier.
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How does it work?How does it work?
The newly developed Loesche The newly developed Loesche
LSKS High Efficiency Dynamic LSKS High Efficiency Dynamic
Classifier improves the Classifier improves the
performance of vertical roller performance of vertical roller
mills.mills.
–– Redesigned air and product Redesigned air and product
flow velocitiesflow velocities
–– New flow characteristics New flow characteristics
within the classifierwithin the classifier
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Arrangement of Dynamic Classifier for Ratcliffe
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Dynamic Classifiers as Dynamic Classifiers as Retrofits for Existing MillsRetrofits for Existing Mills
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Comparison of Fineness Comparison of Fineness Ratcliffe Rosin Rammler Size Distribution - 36 t/h
10 100 1000
Sieve Size - micron
% P
assi
ng S
ieve
GuaranteeGuarantee, Mean R-R Slope = 50.8°Preconversion - Loesche Sieve ResultsPreconversion - Loesche Sieve Results, Mean R-R Slope = 31.7°Postconversion - Loesche Sieve ResultsPostconversion - Loesche Sieve Results, Mean R-R Slope = 52.7°
60
90
99
70
80
99.9
99.98
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Test MatrixTest Matrix
•• Load Load –– 510 to 520 MW510 to 520 MW•• Three different OThree different O22 levelslevels•• Three different DC speeds (100 rpm would Three different DC speeds (100 rpm would
be normal speed)be normal speed)-- 65 rpm (Static classifier ~75 rpm)65 rpm (Static classifier ~75 rpm)-- 90 rpm90 rpm-- 110 rpm110 rpm
•• Six mills in service Six mills in service –– 5 with DCs & 1 with 5 with DCs & 1 with SCSC
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DC Speed vs LOIDC Speed vs LOI
R2 = 0.8894
R2 = 0.9944
R2 = 0.246
0.00
2.00
4.00
6.00
8.00
10.00
12.00
5.00 5.20 5.40 5.60 5.80 6.00 6.20 6.40 6.60 6.80
Oxygen % (Stack)
LOI (
%)
110 RPM - LOI (%)
90 RPM - LOI (%)
65 RPM - LOI (%)
Expon. (110 RPM - LOI (%))
Expon. (90 RPM - LOI (%))
Expon. (65 RPM - LOI (%))
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DC Speed vs NODC Speed vs NOxx
R2 = 0.9573
R2 = 0.9528
R2 = 0.9994
0.45
0.50
0.55
0.60
0.65
0.70
0.75
5.00 5.20 5.40 5.60 5.80 6.00 6.20 6.40 6.60
Oxygen % (Stack)
NO
x (lb
/106 B
tu) 110 RPM - NOx
90 RPM -NOx
65 RPM - NOx
Linear (65 RPM - NOx)
Linear (90 RPM -NOx)
Linear (110 RPM - NOx)
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DC Speed vs CODC Speed vs CO
R2 = 0.9986
R2 = 0.9999
R2 = 0.976
0.00
200.00
400.00
600.00
800.00
1000.00
1200.00
5.00 5.20 5.40 5.60 5.80 6.00 6.20 6.40 6.60
Oxygen % (Stack)
CO
(ppm
)
110 RPM - CO (ppm)
90 RPM - CO (ppm)
65 RPM - CO (ppm)
Expon. (110 RPM - CO (ppm))
Expon. (90 RPM - CO (ppm))
Expon. (65 RPM - CO (ppm))
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ResultsResults
•• LOI reduced by 61%LOI reduced by 61%•• NONOxx reduced by 15%reduced by 15%•• Window of operation before Window of operation before
excessive CO produced increasedexcessive CO produced increased•• Operation at lower OOperation at lower O22 level possible level possible
while holding CO and potential for while holding CO and potential for further NOfurther NOx x reduction of about 20%reduction of about 20%
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Future PlansFuture Plans
•• Overfire Air System with booster Overfire Air System with booster fansfans-- Installed and in commissioningInstalled and in commissioning-- Testing in Summer 2006Testing in Summer 2006-- Install DCs and OFA on other unitsInstall DCs and OFA on other units
•• Dynamic Classifiers installed on other Dynamic Classifiers installed on other similar boilers in the UK including similar boilers in the UK including ball mills and arch furnace boilersball mills and arch furnace boilers