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Detailed analysis of the dewatering processon a CrescentFormer tissue machineon a CrescentFormer tissue machine

by Brian ChristiansenApplications Manager

PaperCon 2011 913

Detailed analysis of the dewatering processContents

Background

Contents

Background

Trial data collectionMeasuring approachMeasuring approachMethodologyExperimental findings

ModelingImpact of variables

Conclusions

PaperCon 2011 Page 1914

Detailed analysis of the dewatering processBackgroundBackground

Starting pointCrescent formerSingle side dewatering

Papermaker issuesWater handling wire

Optimized white water tray designSpeed up capability

Dewatering performance of different fabrics

felt

paper

Fabric characteristics = dewatering capacity


Detailed analysis of the dewatering processBackgroundBackground

ApproachLi dLiterature studySelection measurement equipmentTrial methodologyModeling as part of master thesis


Detailed analysis of the dewatering processTrial data collection

What to measure

Trial data collection

Dewatering pressure through processForming length

Variableswire tension, basis weight, consistencyspeed, furnish, forming fabric design

How to measureRadiAnalyzerX (ultra thin pressure sensing)Physical measurementPhysical measurementStrobe & camera


Detailed analysis of the dewatering processLine measurementLine measurement


Detailed analysis of the dewatering processPressure measurementPressure measurement


Detailed analysis of the dewatering processTrial data collection

How to measure

Trial data collection

How to measureRadiAnalyzerXPhysical measurementStrobe & camera e

[Pa]

Strobe & camera

A B C

Pres

sure

Forming length

g le

ngth

[cm

]Fo

rmin

g

Trial #


Detailed analysis of the dewatering processExperimental findingsExperimental findings

Dewatering pressure2 wire tension levelsGood correlation with theoretical model(p=T/r)

ssur

e [P

a]P

res

Distance from dry line [cm]



Forming lengthWire tension

Forming length vs. machine speed and wire tension

Low High

one

[m]

th m

easu

red

[m]

Leng

th fo

rmin

g zo

Form

ing

leng

t

Combination #



Forming lengthFabric comparison

A B C

A…triple layer, 500 cfmB…triple layer, 530 cfmC…triple layer, 440 cfm ng

leng

th [c

m]

Form

i

Trial #


Detailed analysis of the dewatering processExperimental findings

Forming length

Experimental findings

Forming lengthFurnish, wire tensionSpeed, basis weight A B C

min

g le

ngth

[cm

]Trial # Wire tension

V jet[m/min]

v wire[m/min]

BW Y.[g/m²)

0-1 Low Low Low Water

1 Low Low Low Low

2 High Low Low Low

Form

g

3 High Middle Middle Low

4 Low Middle Middle Low

5 High High High Low

0 -11 High High High Water

Trial #6 High Low Low High

7 Low Low Low High

8 High Middle Middle High


Detailed analysis of the dewatering processModelingModeling

Creation of a dewatering calculation tool based on fundamental physics

Good correlation of measured and calculated values

ulat

ed [m

]or

min

g le

ngth

cal

cuFo

Forming length measured [m]


Detailed analysis of the dewatering processModel outputs - limitsModel outputs limits

Consistency

c = 0.4%

c = 0.3%

c = 0.2%


Detailed analysis of the dewatering processModel outputs - limitsModel outputs limits

Wire tension

T = 9 kN/m

T = 7.5 kN/m

T = 6 kN/m


Detailed analysis of the dewatering processConclusionsConclusions

Insight to the crescent dewatering characteristicsMeasured dewatering pressure fits conventional theory for roll forming

Increased: required forming length:Wire tension (↓)Speed (↑)BW (↑)Freeness (↓) Retention (↓)Consistency for given BW (↓)


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