Interaction of Flotation Cell Operating Variables Henry Peters and - - PowerPoint PPT Presentation

Interaction of Flotation Cell Operating Variables

Henry Peters and Tom Remigio Tim Evans and Marc Dagenais

Purpose of Study

• Previous Abitibi-Consolidated deinking plant

benchmarking had shown large variation in ink removal performance between mills

• Chemistry and cell design had been identified as the

major variables affecting ink removal efficiency and yield losses

• Flotation cells were being operated over a range of

conditions where consistency and air input were used as a means to control performance, but the relationship between these variables was not well understood

• This laboratory study was initiated to better define the

effects of changes to the operating handles available to operators

ACI Deinking Plant Total Yield Loss Comparison

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 50 75 100 125 150 175 200 225 250 FREE INK, ERIC TOTAL YIELD LOSSES

% of Feed Solids

Test Methods

• Experimental design at varying

consistencies and specific air volumes

Experimental Conditions

100 200 300 400 500 600 700 800 0.5 1 1.5 2 Flotation Cell Consistency, % Specific Air Volume, l/kg

Test Methods

• Pulping in Hobart mixer at 45C, 20%

consistency and at 8 kWhr/T SE, standard alkaline chemistry

• Flotation in Voith E-18 lab cell with soap, and

hardness at 180 ppm, controlled air input

• Measurement of yield losses, both

combustible and inorganic

• Measurement of ink removal performance

ASH test for yield analysis

Sample ashed At 525C

• Combustible materials
• Inks
• Stickies
• Fibers
• Plastics
• Inorganic Ash
• Fillers
• Minerals in wood

fiber

Specific Air Volume (SAV)

• Litres of air applied over cell line per kg solids

in cell feed

• Changes with operating consistency
• Some cells allow control of air input
• As a generality, as more air is applied, bubble

surface area available for removal of ink increases

• Determines relative potential rejects rate of

the cell line. Increased SAV increases yield losses as a % of feed solids.

Specific Air Volume vs. Consistency

50 100 150 200 250 0.5 0.7 0.9 1.1 1.3 1.5

Cell Operating Consistency % Increase in Specific Air Volume

Specific air volume increases as cell consistency is lowered

Higher SAV increases % yield losses

Mill Operating Data

100 200 300 400 500 600 50 100 150 200 Specific Air Volume, l/kg Free Ink, ppm 2 4 6 8 10 12 14

Yield Loss, % of feed solids FREE INK YIELD LOSSES

Air holdup and bubble size is dynamic in an

• perating flotation cell

Changes in Indicated Level with Air Holdup

36 37 38 39 40 41 42 43 44 45 46

9:36 10:48 12:00 13:12 14:24 15:36 16:48 18:00 19:12 20:24 21:36 22:48 0:00 1:12 2:24 3:36 4:48 6:00 7:12 8:24 9:36 10:48 12:00 13:12 14:24 15:36 16:48 18:00 19:12 20:24 21:36 22:48 0:00

Time Indicated Level, %

0.5 0.6 0.7 0.8 0.9 1

Measured Consistency

Cell level Consistency

Results of Laboratory Study

Previous Benchmarking study showed that Filler Losses are unique to each System

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 0.0 2.0 4.0 6.0 8.0 10.0 12.0 COMBUSTIBLE LOSSES, % of cell feed FILLER LOSSES, % of feed filler content

MILL A MILL B MILL C MILL D

Laboratory study showed that filler losses are independent of cell operating consistency

Filler Losses at Different Operating Consistencies

10 20 30 40 50 60 200 400 600 800 SAV, l/kg Filler Losses, % of Cell Feed Ash 0.50% 1% 1.50%

Ink removal efficiency and Yield Losses

• Operators are always trying to optimize
• perating costs by improving ink removal and

reducing yield losses, which seem to be

• pposing goals

– Choice of system chemistry – Waste paper grades with lower ash levels – Pulper specific energy – Cell operating consistency – Specific air volume – Rejects rate control – Disperging conditions

Lowest SAV to achieve a target ink removal efficiency is at 0.8% consistency

SVA vs Cell Consistency

300 400 500 600 700 800 900 1000 0.4 0.6 0.8 1 1.2 1.4 1.6

Cell Feed Consistency, % SAV, l/kg

Free Ink=100 Free Ink=150 Free Ink=200

For cells with fixed air input, best ink removal can be achieved at about 0.8% operating consistency

Ink Removal vs. Cell Consistency

150 200 250 300 350 400 0.5 0.7 0.9 1.1 1.3 1.5 Cell Feed Consistency Free Ink in Cell Accepts, ERIC

SAV=200 l/kg SAV=300 l/kg SAV=400 l/kg

Yield Losses

• Increased rejects rates are typically

viewed as necessary for increased ink removal

• Work showed that at higher operating

consistencies, equivalent ink removal can be achieved with reduced losses

Ink is a major component of combustible losses – as losses increase, pulp brightness improves

Brightness/Yield Loss at Different Operating Consistencies

50 51 52 53 54 55 56 57 58 2 4 6 8 10

% Combustible Solids Loss Brightness

0.50% 1% 1.50%

At higher operating consistencies, yield losses necessary to achieve a given ink removal are reduced

Yield Losses

at Different Operating Consistencies

2 4 6 8 10 100 200 300 400 500

Free Ink in Cell Accepts, ERIC

Combustible Losses, % of Cell Feed

0.50% 1% 1.50%

Yield Losses in Relation to SAV and Ink Removal

50 100 150 200 250 300 350 400 450 500 2 4 6 8 10 Combustible Losses, % of cell feed Free Ink in Cell Accepts, ERIC

SAV = 150 l/kg SAV = 425 l/kg SAV = 700 l/kg Cell Feed Consistency 0.5% 1.0% 1.5%

Conclusions

• There is a relationship between ink removal,

specific air volume, consistency, and yield losses

• Filler losses are independent of cell operating

consistency

• Combustible (fiber) losses can be reduced at

higher operating consistencies, with higher specific air volumes