ANALYSIS OF INK ELIMINATION IN FLOTATOR Junsuke Kawana*1, - - PowerPoint PPT Presentation

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 ONP

INTRODUCTION (1)

Uses a lot of energy and chemicals !

Energy consuming multi-step process High dosage of H2O2, NaOH, and Surfactant High Brightness (70-78%) Lower dirt count Lower stickies

Flotator Kneader Flotator Bleaching Kneader Pulper Screen Screen Washer

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 inks in Japanese newspaper

JAPANESE NEWSPAPER (Nikkei Shinbun) CANADIAN NEWSPAPER (Vancouver Sun)

5000 10000 15000 20000 25000 30000

Japan Canada Dirt spec (ppm)

(Disintegrated, and Completely washed)

FLOTATOR CELL (1)

Rotating with blowing air bubbles

Blower view Rotary tube blower

FLOTATOR CELL (2)

Side view

FLOTATOR CELL (3)

Shower Rotary tube blower Shower Inlet Outlet

PURPOSE OF THIS STUDY

First of all, we measured

• Pulp quality before flotation
• Conventional flotation efficiency

More ink removal and brightness gain in flotator

Flotator Kneader Flotator Bleaching Kneader Pulper Screen Screen Washer

PULP BEFORE FLOTATION(1)

Inks detached and fragmented at the same time

5.7 4.1 4.1 30 360 360 74 74 61

After Disp.

7.0 5.4 60 290 63 57

Before Disp. Washed Non- Washed Washed Non- Washed Washed Non- Washed

Ink diameter,

um

ERIC Brightness,% Multi-step disperser

50 100 150 200 250 300 350 400 5 10 15 20 Ink diameter,μ m

The Number of detached ink particles, number/ 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

450 450 40 490 490 18 18 74 56 56

Flotator Acc.

790 40 830 22 73 51 51

Flotator In Difference Washed Non- Washed Difference Washed Non- Washed

ERIC Brightness,%

5

Pts

40 50 60 70 80 90 100 10 20 Ink diameter, u m Removal rate

• f detached inks,%

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

CONVENTIONAL FLOTATION EFFICIENCY (2)

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 Brightness gain, points

OPERATING CONDITIONS AND INK REMOVAL (1) Blower Rim Speed

40 50 60 70 80 90 100 5 10 15 20 Ink Diameter,u m Removal ratio of detached ink, % 8.7m/s 12m/s 16.5m/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 Brightness gain, points 12m/s 16.5m/s

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

OPERATING CONDITIONS AND INK REMOVAL (2)

60 65 70 75 80 85 90 95 100 5 10 15 20 Ink Diameter,u m Removal ratio of detached ink, % 16.5m/s,G/L=4 16.5m/s,G/L=6 60 65 70 75 80 85 90 95 100 5 10 15 20 Ink Diameter,u m Removal ratio of detached ink, % 12m/s,G/L=6 12m/s,G/L=8 60 65 70 75 80 85 90 95 100 5 10 15 20 Ink Diameter,u m Removal ratio of detached 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 smaller Speed 12m/s : More ink removal for 10um or larger

OPERATING CONDITIONS AND INK REMOVAL (3)

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 SIZE

Factors 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

0.447 0.681 1.4

Average bubble diameter, mm

Pulp slurry with surfactant Water with surfactant Water

(1) Fluid

BUBBLE SIZE DISTRIBUTION

Water Water with surfactant Pulp Slurry with surfactant

Water>Water with surfactant>Pulp Slurry with surfactant

(1) Fluid

BUBBLE SIZE DISTRIBUTION

10 20 30 40 50 60 70 80 1 2 3 4 5 6 Air bubble diameter, mm Frequency,% Water Water with surfactant Pulp slurry with surfactant

Bubble growth may affect ink removal

(2) Bubble growth

UPPER LOWER MEDIUM

BUBBLE SIZE DISTRIBUTION

10 20 30 40 50 60 70 80 1 2 3 4 5 6 Air bubble diameter, mm Frequency,% Lower Medium Upper

Water ; Bubbles grew at upper position.

(2) Bubble growth

BUBBLE SIZE DISTRIBUTION

10 20 30 40 50 60 70 80 1 2 3 4 5 6 Air bubble diameter, mm Frequency,% Lower Upper

Pulp Slurry ; No growth occured

BUBBLE SIZE DISTRIBUTION

(2) Bubble growth

5 10 15 20 25 30 35 40 1 2 Air bubble diameter, mm Frequency,% 15m/s 17m/s 19m/s

The faster the rotation speed, the smaller the bubble diameter

(3) Blower rim speed

BUBBLE SIZE DISTRIBUTION

0.59mm 0.42mm 0.45mm

Smaller bubbles led to higher brightness!

5 10 15 20 25 30 35 40 45 1 2 3 4 5 6 Air bubble diameter, mm Frequency,% 15m/s,30m3/h 15m/s,70m3/h

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

(4) Air Flow Rate-1

BUBBLE SIZE DISTRIBUTION

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

(4) Air Flow Rate-2

BUBBLE SIZE DISTRIBUTION

5 10 15 20 25 30 35 40 45 1 2 3 4 5 6 Air bubble diameter, mm Frequency,% 15m/s,30m3/h 15m/s,70m3/h 19ｍ/s,70m3/h

Smaller bubbles led to higher brightness!

CONCLUSIONS (1)

In the conventional state Before 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 measurement Small 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

CONVENTIONAL FLOTATION EFFICIENCY (3)

Smaller inks significantly influence brightness!

R2 = 0.63 50 55 60 65 70 0.0 1.0 2.0 3-100um inks, % ISO brightness % R2 = 0.93 50 55 60 65 70 0.0 0.5 1.0 3-10um inks, % ISO brightness,% R2 = 0.99 50 55 60 65 70 500 1000 ERIC ISO brightness, %