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8th Research Forum on RecyclingNiagara Falls, ON Canada, 9/2007

Fine particles separation inrecovered paper suspensions

Wagner, J.; Putz, H.-J.; Schabel, S.*

* Technische Universität DarmstadtChair for Paper Science and Mechanical Process Engineering (PMV)

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Introduction:Why separating organic from anorganic fines?

How to quantify progress:Why lack of measurement techniques is a major problem

Our approach for measurement:- particle size distribution- settling velocity- image analysis

Separation results

Overview

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recovered paper56%

chemical pulp20%

mechanical pulp7%

fillers and coating pigments

13%

chemical additives4%

Raw materials for paper production

Raw material consumption in 2005 in Germany:25.5 million tons for 21.7 million tons paper production

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Recovered paper suspensions to be considered

• Packaging paper- Pulp - Filtrate from thickeners- Filtrate from paper machine wire

• Graphic paper- Flotation foam and sludge

• Tissue paper- Washer filtrate

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Inorganic and organic components in a flotation foam of a stock preparation for graphic recycling paper

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• Inorganic fines from fillers and coating pigments cause lowerstrength properties

• Effect of organic fines depends on surface condition:

degree of fibrillation strength properties

• Flotation and washingseparate both components from longer fibre material

low selectivity, losses during paper production

Fines in recovered paper suspensions

binding area inorganic components

fibre

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How to quantify progress

• Sedimentation-Balance

• Sedi-Graph (X-Ray)

• Manometer-Centrifuge

• Laser-Diffraction

• FiberLab

h

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Observing sedimentation of virgincomponents

250 ml

120 ml

38 ml

Cylinder height in ml

chemical pulp fines chemical pulp fines+

calcium carbonate

calcium carbonate

w3

Slide 8

w3 Sedimentationsgeschwindigkeiten ausrechnen und dazuschreibenwimi, 11/18/2006

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Sedimentation balance

coated paper fines

80 % inorganic

uncoated paper fines

50 % inorganic

mechanical pulp fines

0 % inorganic

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Particle size distributionsmeasured with laser diffraction

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0.1 1 10 100 1000 10000

äquivalenter Kugeldurchmesser in micrometer

Volu

men

in %

gestrichenes Papiergestrichenes Papier + SchliffSchliffTMPCaCO3

Size of equivalent sphere in µm

Rel

. fre

quen

cy in

%

Equivalent particle diameter in µm

GWCoated paper + GWCoated paper

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Measuring sedimentation of componentswith a sedimentation balance

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0,001 0,01 0,1 1 10

Sedimentation velocity in mm/s

Mas

s di

strib

utio

n su

m

CaCO3 + Fines I

CaCO3 + Fines II

CaCO3 + Fines III

CaCO3

Chem. Pulp Fines

Difference should beUtilizable forseparation

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Uncoated paper fines’ settling velocities

Sinkgeschwindigkeit, Papier ungestrichen, normiert auf g

0,00,10,20,30,40,50,60,70,80,91,0

1,00E-07 1,00E-06 1,00E-05 1,00E-04 1,00E-03 1,00E-02Sinkgeschwindigkeit [m/s]

Q3

0,5 Ma% 50g1 Ma% 50 g2 Ma% 50 g3 Ma% 50 gSediwaage 3,7 Ma%

Normalised on acceleration due to gravity g

Mas

s di

strib

utio

nsu

m

Sedimentation velocity in m/s

sedimentation balance at 3.7 % consistency

manometer centrifuge at x % consistency

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Coated paper fines’ settling velocities

0,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

1,00E-07 1,00E-06 1,00E-05 1,00E-04 1,00E-03 1,00E-02Sinkgeschwindigkeit [m/s]

Q3 1 Ma% 50 g

2 Ma% 50 g

3 Ma% 50 g

Sediwaage 3,7 Ma%

Sedimentation velocity in m/s

Mas

s di

strib

utio

n su

m

sedimentation balance at 3.7 % consistency

manometer centrifuge at x % consistency

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Comparison of Sed. Balance and Sedigraph

0102030405060708090

100

0.1 1.0 10.0 100.0

Equivalent spheric diameter in µm

Mas

s di

strib

utio

n su

m in

% SedimentationbalanceSedigraph

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Image analysis forsedimentation evaluation

lumino

usso

urce

cameraPCO 4000

observation window:• width: 30 mm• height: 20 mm

sedimentation cell

single picture → particle size

series of pictures → sedimentation velocity

technical data camera:•resolution: 4008 x 2672•frame rate: 5 frames/s•illumination time: 5 µs –

5 days

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Sequence

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Sedimentation test rig

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Separation results

0

10

20

30

40

50

60

model suspension sediment overflow

ash

cont

ent i

n %

model suspension (fitrate coatedpaper + filtrate groundwood)

-10,6 %

+ 20,1 %

36,4

%

25,8

%

56,5

%

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Latest Results with MechnicalTreatment

0

10

20

30

40

50

60

70

80

90

startsuspension sediment

ash

cont

ent i

n %

filtrate flotation sludge untreated filtrate flotation sludge treated with ultrasonic

81,3 %

74,8

%

70,5

%

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Latest Results: Visual Impression

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Conclusions

• Sedimentation of fines in pulp suspensions iscomplex and measurement difficult

• Combinations of measurement methods arenecessary for evaluating all relevant effects

• Most promising: combination of sedimentaion camera(organic particles) with sedimentation device (all particles)

• Still open questions and unsolved problemsremaining – disintegration and stabilisation seems to be essential