paper washing.pdf

8/17/2019 paper washing.pdf

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BL0055-000

Bleach Stage Washers, Pumps and Mixers;Bleach Stage Washers, Pumps and Mixers;

Putting the Components Together Putting the Components Together Bill Miller, MCBill Miller, MC®® Product Manager Product Manager

Sulzer Process Pumps (US) Inc.Sulzer Process Pumps (US) Inc.Easley,SCEasley,SC


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Bleach Stage ComponentsBleach Stage Components

Retention

time

Washer Pump Mixer Tower


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Bleach Stage Feed System:Bleach Stage Feed System:

Three Essential Components to Work as OneThree Essential Components to Work as One

Retention

time

Washer Pump Mixer Tower

Consistency

Steam usage

Water usage

Chemical usage

Brightness

ConsistencySteam usage

Even feed

System pressure

BrightnessConsistency

Chemical usage

Brightness

Uniform consistency

Even flowAccurate process control


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WashersWashers OperationOperation

DesignDesign PerformancePerformance


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Bleach Plant WasherBleach Plant Washer

PurposePurpose

Reduce carryover levels to bleach stage (organic and inorganic)Reduce carryover levels to bleach stage (organic and inorganic) Adjust pH and temperature of pulp Adjust pH and temperature of pulp

Thicken 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 showersUse filtrates from following bleach stage on upper showers(pH and temperature)(pH and temperature)

BL0055-031


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Bleach Plant Washers in North AmericaBleach Plant Washers in North America

Operate above design specific loadingOperate above design specific loading Older, original part of pulp mill operationOlder, original part of pulp mill operation

Primarily drum washers (vacuum and pressure)Primarily drum washers (vacuum and pressure)

reference 1BL0055-003

Vacuum Pressure Nip Pressure


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Displacement Ratio and Mat MechanicsDisplacement Ratio and Mat MechanicsPrinciples of Washing TheoryPrinciples of Washing Theory

Subscripts:Subscripts:

VV – – Inlet (vat)Inlet (vat)

SS – – Shower Shower

DD – – 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 of Concentration of

dissolved solidsdissolved solids

L =L = Weight unit of filtrateWeight unit of filtrate

Pulp mat Drum

SV

SD

SS

LLSS = kg shower/kg pulp= kg shower/kg pulp

LLDD = kg in pulp/kg pulp= kg in pulp/kg pulp

Reference 2 & 3BL0055-041

CD0001-005C


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Drum Washing StepsDrum Washing Steps

DilutionDilution

ExtractionExtraction DisplacementDisplacement

ExtractionExtraction



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Drum Washing StepsDrum Washing Steps

DilutionDilution


DisplDisplacaceementment


Lower Shower Lower Shower -- WW

Upper Shower Upper Shower --

Medium ExchanMedium Exchan

BL0055-046


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Bleach Plant WashingBleach Plant Washing

WasherLocation

WashingGoal

Wash FiltratesUtilized

D0 Stage Acids, organics,

inorganics (Ca, Mn, etc.), pH,temperature

D stage, fresh watercondensate, Eop stage

Eop Stage Alkali, organics, pH,temperature

D stage, fresh water,condensate,

D Stage Conductivity, chlorides,‘”anionic trash”

Fresh water, condensate


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Vacuum Drum DesignsVacuum Drum Designs

Center Drainage -Flat Valve - Drive Shaft

End Drainage -Radial Valve - Drive Trunnion


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End Drainage Vacuum Filter (GL&V)End Drainage Vacuum Filter (GL&V)

Radial Valve, Trunnion DriveRadial Valve, Trunnion Drive

VALVE

DRAINAGE BUCKET

CORRUGATED DECK

INLET BOX

DROPLEG

DISPLACEMENT SHOWER

FACE WIRE

DRUM ROTATION

TAKE-OFF ASSEMBLY

REPULPER

BL0055-010

CD0022-002

Worm Gear DriveWORM GEAR DRIVEWORM GEAR DRIVEWORM GEAR DRIVE


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Face Wire SupportFace Wire Support

CYLINDER

ROTATION

FACE

WIRE

WINDING

WIRE

INTERMEDIATE GRID

WITH CROSS DRAIN

OPENINGS

DIVISION

GRID

CYLINDER

SHELL

Traditional Wire Wound Anti-Rewet Corrugated Deck

CYLINDER

ROTATION

FACE

WIRE

REPLACEABLE

CORRUGATEDDECK

INTERMEDIATE GRID

WITH CROSS DRAIN

OPENINGS

DIVISION

GRID

CYLINDE

SHELL


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Bleach Washer Seal Tank/Dropleg DesignBleach Washer Seal Tank/Dropleg Design

Recommendedht. > 30 ft.

Pulp

Feed

To Shower or Effluent

Dropleg

SealChambe

BaffleVat

Dilution

FiltrateTank

DrumWashe

Vent

Dropleg Design:

Sized for 12 to 16

fps superficial

velocity Straight, vertical,

drop, no jogs

BL0055-016


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Increase Feed ConsistencyIncrease Feed Consistency

Dilution flow/pumpingDilution flow/pumping

requirementrequirement

Extraction requirementExtraction requirement

Filtrate volumeFiltrate volume

Seal tank sizeSeal tank size


From 1% to 4%From 1% to 4%

reducesreduces

Requires Inlet BoxDesign


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Comparison of Specific Loading RatesComparison of Specific Loading Rates

SWDSWD HWDHWD

Vacuum washer 0.75Vacuum washer 0.75--0.800.80 0.650.65--0.700.70

Pressure washerPressure washer 2.52.5--2.72.7 2.32.3--2.52.5

Wash PressWash Press 2.42.4--2.62.6 2.22.2--2.42.4

For various drum washer designs,For various drum washer designs,

units in ODTPD/ ftunits in ODTPD/ ft22

WA0027-009

Specific loading = ODTPD/(drum dia. x π)(drum length)


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Compaction Baffle (GL&V)Compaction Baffle (GL&V)

BL0055-021

CB0051-002

INLET BOX

DISPLACEMENT

SHOWER

DRUM ROTATION

TAKE-OFF

ASSEMBLY

REPULPER

EXTRACTION

PRESSURIZED AIR

End drainage, corrugated deck, deck plateEnd drainage, corrugated deck, deck plate


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Drum Displacer (Drum Displacer ( Andritz Andritz))

w a s h liq u id 1 w a sh l iq u id 1

w a s h li q u id 2

wash

filtrate 1

wash

filtrate

2

r e t u r n fi lt r a t e

e x t r a ct e d fil tr a t e

x - f il t ra t e

va cu um f ilt r a t e


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Displacement Press DP (Displacement Press DP (MetsoMetso))

HoodShredder Conveyor

PulpOutlet

PulpInlet

Shower Pipes

VatPressRoll

WashWater In

FiltrateOutletBL0055-022


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Bleach Stage Components with Wash PressBleach Stage Components with Wash Press

Wash press/conveyor

Pump Mixer Tower

Pulp

Filtrate

32% cs

12% cs


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Drum Utilization for Various Washer DesignsDrum Utilization for Various Washer Designs

BL0055-003

Pressure Nip PressureVacuum

4% feed 4% and 10% feed

Formation Extraction

DisplacementFinal Extraction


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Low Level ECF FiberlineLow Level ECF Fiberline

BL0055-027

CB0047-001

ODODooEEopopD SequenceD Sequence

Eff t f EEff t f E W hi D St B i htW hi D St B i ht


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Effect of EEffect of EOO Washing on D Stage BrightnessWashing on D Stage Brightness

DevelopmentDevelopment

45

50

55

60

65

70

75

80

85

0 0.2 0.4 0.6 0.8 1

ClO2 consumed in D stage, % on pulp

B r i g h t n

e s s ,

% I S O

100%

83% (EO) washer efficiency(CD)(EO) bleached,

2.7 kappa number

softwood kraft pulp

Reference 4


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Bleach Washing MeasurementsBleach Washing Measurements

D0 washer Displacement Ratio: Cl-, Ca++, TDS, cond.,

Eop stage: pH , chemical demand Discharge consistency

EOP washer Displacement Ratio: COD, TOC, cond., Na+

D stage: pH and pH control, chemical demand

Discharge consistency

D washer Displacement Ratio: Cl-, cond.,

Stock prep. chemicals

Discharge consistency BL0055-043


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Solids for Washing MeasurementSolids for Washing Measurement

SolubleSoluble

Easy to measureEasy to measure

Relevant to processRelevant to process

BL0055-043


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Penalty for Poor Bleach Plant Washer PerformancePenalty for Poor Bleach Plant Washer Performance Higher extracted kappa number and lower

final brightness Increased chemical usage

ClO2

Hydrogen peroxide (Eop)

NaOH

H2SO4

Scale and/or pitch deposition

BL0055-034


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Medium Consistency PumpsMedium Consistency Pumps


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Medium Consistency Pumps PurposeMedium Consistency Pumps Purpose

Deliver nonDeliver non--pulsing, stable pulp flowpulsing, stable pulp flow Remove air Remove air

Reduce mixer loadReduce mixer load Improve bleach chemical controlImprove bleach chemical control

Bleach Stage


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Positive Displacement PumpsPositive Displacement Pumps No pulp fluidization

No air removal Uneven pulp flow due

to lack of feed control

No speed control, beltdrive

Vibration

Low head requirements

at higher stock

consistency due to air

content, no CV

What goes in

is what comes

out


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Positive Displacement PumpsPositive Displacement Pumps

Screw feeders

Closed pocket rotors

Belt drive


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0902.cdr

FluidizationFluidization


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0903.cdr

Air Content in Stock Air Content in Stock

Five Functional Zones of MediumFive Functional Zones of Medium


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Five Functional Zones of MediumFive Functional Zones of Medium

Consistency PumpingConsistency Pumping

A. Fluidization Zone, fiber network disrupted by high shear

forces.

B. Gas Separation Zone, air is separated from the stock.

C. Pumping Zone, impeller vanes pump stock towards

discharge

D. Fiber Return Zone, fibers entrained with air from zone B a

returned to the pump discharge.

E. Degassing Zone, air is removed to the degassing unit.


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Medium Consistency PumpMedium Consistency Pump

0035.cdr


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Medium Consistency Pump Control SystemMedium Consistency Pump Control System


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Medium Consistency PumpingMedium Consistency Pumping -- VariablesVariables

• Raising consistency from 10% to 12% increasesfriction loss by 53%.

• Increasing production from 1000 to 1500 ADST/D increases friction loss by only 6%.

• Raising pH from 7 to 10 decreases friction lossby 43%.

• Dropping temperature from 200°F to 100°Fdoubles the friction loss.


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0904.cdr

Questions?Questions?


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MixersMixers

DesignDesign

OperationOperation

PerformancePerformance


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Mixer PurposeMixer Purpose

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 time

chemical prechemical pre--distributiondistribution proper metering of flowsproper metering of flows

eliminate stock flow pulsationeliminate stock flow pulsation

maintain uniform consistency and pressuremaintain uniform consistency and pressure

Three Basic Steps for Mixer LoadThree Basic Steps for Mixer Load


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OptimizationOptimization

PrePre--distributiondistribution

bulk flowbulk flow

macromacro--mixing, >10 mm scalemixing, >10 mm scale

Fiber mixingFiber mixing

turbulent shear, diffusionturbulent shear, diffusion 0.50.5--10 mm scale10 mm scale

MicroMicro--mixingmixing

Diffusion, small scale fluid motionDiffusion, small scale fluid motion


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Chemical Addition ConfigurationChemical Addition Configuration


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HighHigh--Shear/HighShear/High--Intensity MixersIntensity Mixers


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Viewed from Motor

Mixer and Liquid Chemical AdditionMixer and Liquid Chemical Addition


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ClO2

Pulp

Mixer

Pulp andClO2

ClO2

Mixer Variance Testing

Pre-distribution

Fiber

Mixing

Micro-

Mixing

Mixer


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2308ppt

Chemical MixerChemical Mixer -- Average Flow Field Average Flow Field

Mixing Index (M) MeasurementsMixing Index (M) Measurements


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Mixing Index (M) MeasurementsMixing Index (M) Measurements

M = s/xM = s/x

S S is standard deviation of measured quantityis standard deviation of measured quantity

X X is mean value of measured quantityis mean value of measured quantity

pipe surface temperature measurementspipe surface temperature measurements

also determines equivalent chemical chargesalso determines equivalent chemical charges

Mixing indexMixing index has same definition ashas same definition as inhomogeneityinhomogeneity

or varianceor variance

Liquid mixing only


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MixingMixing InhomogeneityInhomogeneity TestingTesting

Portable recorder Portable recorder

Eight (8) surface thermocouplesEight (8) surface thermocouples

InsulatedInsulated

CalibratedCalibrated

Eight (8) temperature data sets after ClOEight (8) temperature data sets after ClO22 Thirty (30) minute intervalsThirty (30) minute intervals

One (1) stock temperature reading before ClOOne (1) stock temperature reading before ClO22

One (1) ClOOne (1) ClO22 temperaturetemperature


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ClO2

Pulp

Mixer

Pulp andClO2

ClO2 Mixer Variance Testing

Mixer

T1T2

T3

T4T5

T6

T7

T8

TSTC

CB l C l l ti


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Balance CalculationsBalance Calculations

I h itI h it C l l tiC l l ti


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InhomogeneityInhomogeneity CalculationsCalculations

Importance of ClOImportance of ClO22 Line ConfigurationLine Configuration

O ti i d f PO ti i d f P Di t ib ti AdditiDi t ib ti Additi


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Optimized for PreOptimized for Pre--Distribution AdditionDistribution Addition

0

5

10

15

20

25

before before before before after after after

inhomog,%

#ClO2/T(act)

ConclusionConclusionS S CBl h St F d S t C t


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Bleach Stage Feed System ComponentsBleach Stage Feed System Components

Pulp consistencyPulp consistency Process flow stabilityProcess flow stability

Process control accuracyProcess control accuracy

Bleach chemical usageBleach chemical usage

Brightness ceilingBrightness ceiling

Will impactWill impact

BL0055-049

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