analysis of ink elimination in flotator

ANALYSIS OF INK ELIMINATION

IN FLOTATOR

Junsuke Kawana*1, Shintaro Sasada*2, Atsushi Watanabe*1*1: Oji Paper Co., Ltd. Pulp & Paper Research Laboratory*2: Oji Paper Co., Ltd. Technical Department

Requirements for DIP from ONPINTRODUCTION (1)

Uses a lot of energy and chemicals ! Energy consuming multi-step processHigh dosage of H2O2, NaOH, and Surfactant

High Brightness (70-78%)Lower dirt count Lower stickiesFl

otat

or

Kne

ader

Flot

ator

Ble

achi

ng

Kne

ader

Pulp

er

Scre

en

Scre

en

Was

her

INTRODUCTION (2)Improvement of current equipment efficiency

Pulper,Flotator,Disperser,Screen…

focused on Flotator

INTRODUCTION (3)Self-manufacturing of OK-flotator from 1984

Japanese Newspaper inks firmly bonded to fiber !- Resin- Vegetable oil ( quick-drying )

Kneader or Disperser (1 or 2 stage)

Fine dispersed inks

Background

Washer?But less water

Original flotator needed!

Many bound inksin Japanese newspaper

JAPANESE NEWSPAPER(Nikkei Shinbun)

CANADIAN NEWSPAPER(Vancouver Sun)

0

5000

10000

15000

20000

25000

30000

Japan Canada

Dirt sp

ec (pp

m)

(Disintegrated, and Completely washed)

FLOTATOR CELL (1)

Rotating with blowing air bubbles

Blower view

Rotary tube blower

FLOTATOR CELL (2)

Side viewFLOTATOR CELL (3)

Shower

Rotary tube blower

Shower

InletOutlet

PURPOSE OF THIS STUDY

First of all, we measured-Pulp quality before flotation-Conventional flotation efficiency

More ink removal and brightness gain in flotator

Flot

ator

Kne

ader

Flot

ator

Ble

achi

ng

Kne

ader

Pulp

er

Scre

en

Scre

en

Was

her

PULP BEFORE FLOTATION(1)

Inks detached and fragmented at the same time

5.74.1303607461AfterDisp.

7.05.4602906357BeforeDisp.

WashedNon-Washed

WashedNon-Washed

WashedNon-Washed

Ink diameter, um

ERICBrightness,%

Multi-step disperser

050

100150200250300350400

0 5 10 15 20Ink diameter,μ m

The

Num

ber o

fde

tach

ed in

k pa

rticl

es,

num

ber/

mm

2

PULP BEFORE FLOTATION(2)Detached inks before flotation

10um or smaller

CONVENTIONAL FLOTATION EFFICIENCY (1)

- Only 5 points Brightness gain- Leaving many inks after flotation

45040490187456FlotatorAcc.

79040830227351FlotatorIn

DifferenceWashedNon-Washed

DifferenceWashedNon-Washed

ERICBrightness,%

5Pts

405060708090

100

0 10 20

Ink diameter, u m

Rem

oval

rate

of d

etac

hed

inks

,%Removal rate fell rapidly below 7um(While small detached inks increased !)


SUMMARY OF CONVENTIONAL FLOTATION

Change operating conditions

Before Flotation-Most inks fragment smaller than 10um

Conventional Flotation-Only 5 points brightness gain-Left many ink particles smaller than 7um

Removal of 7um or smaller particles is required.

-Blower Rim Speed -Air Volume (G/L)

G/L= Air Flow Rate（m3/h）/ Pulp Slurry Flow Rate（m3/h）

4

5

6

7

8

9

5 10 15 20

Rotation speed of blower, m/s

Brig

htne

ss g

ain,

poi

nts

OPERATING CONDITIONS AND INK REMOVAL (1)

Blower Rim Speed

40

50

60

70

80

90

100

0 5 10 15 20Ink Diameter,u m

Rem

oval

ratio

of d

etac

hed

ink,

%8.7m/s12m/s16.5m/s

- More ink removal for 7um and less dia. due to higher rim speed- Higher brightness gain due to higher rim speed

Air Volume (G/L)

5

6

7

8

9

10

2 4 6 8 10

G/L

Brig

htne

ss g

ain,

poi

nts 12m/s

16.5m/s

Speed 16.5m/s : brightness gain improved due to higher air volumeSpeed 12m/s : not improved so much


6065707580859095

100


Rem

oval

ratio

of d

etac

hed

ink,

%

16.5m/s,G/L=4

16.5m/s,G/L=66065707580859095

100


Rem

oval

ratio

of d

etac

hed

ink,

%12m/s,G/L=6

12m/s,G/L=86065707580859095

100

0 5 10 15 20

Ink Diameter,u m

Rem

oval

ratio

of d

etac

hed

ink,

%12m/s,G/L=6

12m/s,G/L=8

*G/L= Air Flow Rate（m3/h）/Pulp Slurry Flow Rate（m3/h）

Air Volume (G/L) Speed 16.5m/s : More ink removal for 10um or smallerSpeed 12m/s : More ink removal for 10um or larger


SUMMARY OF OPERATING CONDITIONS

-Higher Rim Speed -Larger Air Volume (G/L) with High Rim Speed.

Why?

Higher brightness gain with . . .

Changing operating condition

Bubble size measured.

DEVICE FOR MEASURING BUBBLE SIZE DISTRIBUTION

- Fluid containing air passed through the measuring cell.- Pictures were taken with CCD Camera.- Bubble diameter was measured by image analysis.- Measured at different heights (lower, medium, and upper).

MEASUREMENT OF BUBBLE SIZEFactors which may influence the bubble size distribution

(1) Fluid

(2) Bubble growth

(3) Blower rim speed

(4) Air flow rate (G/L)

Water>Water with surfactant>Pulp Slurry with surfactant

0.4470.6811.4Average bubble diameter, mm

Pulp slurry with surfactant

Water with surfactantWater

(1) FluidBUBBLE SIZE DISTRIBUTION

Water Water with surfactant Pulp Slurry with surfactant

Water>Water with surfactant>Pulp Slurry with surfactant

(1) FluidBUBBLE SIZE DISTRIBUTION

01020304050607080

0 1 2 3 4 5 6Air bubble diameter, mm

Freq

uenc

y,%

WaterWater with surfactantPulp slurry with surfactant

Bubble growth may affect ink removal(2) Bubble growth

UPPER

LOWER

MEDIUM

BUBBLE SIZE DISTRIBUTION

01020304050607080

0 1 2 3 4 5 6

Air bubble diameter, mm

Freq

uenc

y,%

LowerMediumUpper

Water ; Bubbles grew at upper position.(2) Bubble growth


01020304050607080

0 1 2 3 4 5 6


Freq

uenc

y,%

Lower

Upper

Pulp Slurry ; No growth occured

BUBBLE SIZE DISTRIBUTION(2) Bubble growth

05

10152025303540

0 1 2


Freq

uenc

y,%

15m/s17m/s19m/s

The faster the rotation speed, the smaller the bubble diameter(3) Blower rim speed


0.59mm

0.42mm

0.45mm

Smaller bubbles led to higher brightness!

05

1015202530354045

0 1 2 3 4 5 6


Freq

uenc

y,%

15m/s,30m3/h15m/s,70m3/h

Air flow rate up ; bubbles smaller than 2mm decrease and bubbles larger than 2mm increase.

(4) Air Flow Rate-1BUBBLE SIZE DISTRIBUTION

Air flow rate up + rotation speed up ; Smaller bubbles increased

(4) Air Flow Rate-2BUBBLE SIZE DISTRIBUTION

05

1015202530354045

0 1 2 3 4 5 6


Freq

uenc

y,%

15m/s,30m3/h15m/s,70m3/h19ｍ/s,70m3/h

Smaller bubbles led to higher brightness!

CONCLUSIONS (1)

In the conventional stateBefore flotation-Most inks fragment into particles of less than 10um

Conventional flotation-Only 5 point brightness gain-Left many ink particles smaller than 7um

Operating conditions Higher brightness & removal of smaller ink particles at -Higher rim speed -Larger air volume (G/L) with high rim speed.

CONCLUSIONS (2)Air bubble size measurementSmall bubbles at…

-High rim speed-Large air volume with high rim speed

lead to higher brightness gain

By applying these findings, we could succeed in improving the deinking efficiency with our flotator

FUTURE TASKS

… More improvement in efficiency（Electricity consumption, Retention）

Optimal Cell structure

Optimal surfactant

Thank you for your kind attention!

FUTURE TASKS

Optimal Cell structure


Smaller inks significantly influence brightness!

R2 = 0.63

50

55

60

65

70

0.0 1.0 2.0

3-100um inks, %

ISO

brig

htne

ss % R2 = 0.93

50

55

60

65

70

0.0 0.5 1.03-10um inks, %

ISO

brig

htne

ss,% R2 = 0.99

50

55

60

65

70

0 500 1000ERIC

ISO

brig

htne

ss, %

analysis of ink elimination in flotator

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