BL0055-000 Bleach Stage Washers, Pumps and Mixers; Bleach Stage Washers, Pumps and Mixers; Putting the Components Together Putting the Components Together Bill Miller, MC Bill Miller, MC ® ® Product Manager Product Manager Sulzer Process Pumps (US) Inc. Sulzer Process Pumps (US) Inc. Easley,SC Easley,SC
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BL0055-000
Bleach Stage Washers, Pumps and Mixers; Bleach Stage Washers, Pumps and Mixers; Putting the Components TogetherPutting the Components TogetherBill Miller, MCBill Miller, MC®® Product ManagerProduct ManagerSulzer Process Pumps (US) Inc.Sulzer Process Pumps (US) Inc.Easley,SCEasley,SC
Bleach Stage Components Bleach Stage Components
Retentiontime
Washer Pump Mixer Tower
Bleach Stage Feed System:Bleach Stage Feed System:Three Essential Components to Work as One Three Essential Components to Work as One
PurposePurposeReduce carryover levels to bleach stage (organic and inorganic)Reduce carryover levels to bleach stage (organic and inorganic)Adjust pH and temperature of pulpAdjust pH and temperature of pulpThicken pulpThicken pulp
Method (with filtrate recycle)Method (with filtrate recycle)Use cleaner filtrates or warm fresh water on lower showers (washUse cleaner filtrates or warm fresh water on lower showers (wash))Use filtrates from following bleach stage on upper showers Use filtrates from following bleach stage on upper showers (pH and temperature)(pH and temperature)
BL0055-031
Bleach Plant Washers in North AmericaBleach Plant Washers in North America
Operate above design specific loadingOperate above design specific loadingOlder, original part of pulp mill operationOlder, original part of pulp mill operationPrimarily drum washers (vacuum and pressure)Primarily drum washers (vacuum and pressure)
reference 1BL0055-003
Vacuum Pressure Nip Pressure
Displacement Ratio and Mat MechanicsDisplacement Ratio and Mat MechanicsPrinciples of Washing TheoryPrinciples of Washing Theory
Subscripts:Subscripts:
V V –– Inlet (vat)Inlet (vat)
S S –– ShowerShower
D D –– Discharge (mat)Discharge (mat)
Displacement ratio = DR =Displacement ratio = DR =
Wash ratio = RW= LWash ratio = RW= Lss/L/LDD
SSVV -- SSDD
SSVV -- SSSS
S =S = Concentration ofConcentration ofdissolved solidsdissolved solids
L =L = Weight unit of filtrateWeight unit of filtrate
No pulp fluidizationNo air removalUneven pulp flow dueto lack of feed controlNo speed control, beltdriveVibration Low head requirementsat higher stockconsistency due to air content, no CV
Reduce degree of non uniformity in chemical/pulp distribution. Reduce degree of non uniformity in chemical/pulp distribution. Assure each fiber sees equal chemical concentration.Assure each fiber sees equal chemical concentration.Reduce non uniformity by:Reduce non uniformity by:
larger mixer retention timelarger mixer retention timechemical prechemical pre--distributiondistributionproper metering of flowsproper metering of flowseliminate stock flow pulsationeliminate stock flow pulsationmaintain uniform consistency and pressuremaintain uniform consistency and pressure
Three Basic Steps for Mixer Load Three Basic Steps for Mixer Load OptimizationOptimization
PrePre--distributiondistributionbulk flowbulk flowmacromacro--mixing, >10 mm scalemixing, >10 mm scale
Fiber mixing Fiber mixing turbulent shear, diffusionturbulent shear, diffusion0.50.5--10 mm scale10 mm scale
MicroMicro--mixing mixing Diffusion, small scale fluid motionDiffusion, small scale fluid motion<0.05 mm scale<0.05 mm scale
Chemical Addition ConfigurationChemical Addition Configuration
Mixer and Liquid Chemical AdditionMixer and Liquid Chemical Addition
ClO2
Pulp
Mixer
Pulp and
ClO2
ClO2 Mixer Variance Testing
Pre-distribution
FiberMixing
Micro-Mixing
Mixer
2308ppt
Chemical Mixer Chemical Mixer -- Average Flow FieldAverage Flow Field
Mixing Index (M) MeasurementsMixing Index (M) Measurements
M = s/xM = s/x
SS is standard deviation of measured quantityis standard deviation of measured quantityX X is mean value of measured quantityis mean value of measured quantitypipe surface temperature measurementspipe surface temperature measurementsalso determines equivalent chemical chargesalso determines equivalent chemical charges
Mixing indexMixing index has same definition as has same definition as inhomogeneity inhomogeneity or varianceor variance
Importance of ClOImportance of ClO22 Line Configuration Line Configuration Optimized for PreOptimized for Pre--Distribution Addition Distribution Addition
0
5
10
15
20
25
before before before before after after after
inhomog,%#ClO2/T(act)
ConclusionConclusionBleach Stage Feed System ComponentsBleach Stage Feed System Components
Pulp consistencyPulp consistencyProcess flow stabilityProcess flow stabilityProcess control accuracyProcess control accuracyBleach chemical usageBleach chemical usageBrightness ceilingBrightness ceiling