1. Aerosol-Enhanced Deinking of Recycled Paper by Column Flotation

2. McGill University McMaster University
Cesar O. Gomez, Claudio Acuña* , James A. Finch, and
Department of Mining and Metallurgical Engineering
McGill University
Robert Pelton
McMaster Centre for Pulp and Paper Research
McMaster University
* Current address:Departamento de Ingeniería Química, Universidad Católica del Norte, Antofagasta, Chile

3. Abstract
Flotation de-inking has become the process of choice for removing ink from re-pulped paper. Hydrophobic ink particles are collected and carried by rising air bubbles which remove them from the paper pulp.
Coating air bubbles with an insoluble hydrophobic material (like silicone oil) increased the ability of the bubbles to remove carbon black particles from a dispersion in water. Forming a layer of hydrophobic material on the surface of bubbles was done by injecting small oil droplets into the air to form an aerosol.
This work describes tests designed to establish the effectiveness of aerosol-enhanced flotation in the de-inking of industrial pulps.

4. Stages involved in flotation
Transport: bubble-particle
aggregate moves to the top
Attachment: solid/water/air
interface forms
Collision: particle reaches
the bubble surface

5. Flotation with oil-coated bubbles
Oil-coated bubbles: attachment
requires a solid/water/oil or a
solid/oil/air contact line
Air bubbles: attachment
requires a solid/liquid/air
contact line

6. Schematics of testing equipment
Flotation column
REJECTS P F
FEED P F P
ACCEPTS
Aerosol
generator F
AIR
Venturi aerator F
OIL
RECYCLE
Syringe pump

7. Schematics of the system for generating and injecting aerosol into the column
To flotation column
Atomizing
chamber
AIR
Ultra-sonic
nozzle
OIL
FEED and RECYCLE

8. Plant results: effect of oil injection on brightness gain

9. Conclusions
Dispersing an aerosol (silicone oil) in wastepaper pulp is an effective method to generate oil-coated bubbles.
Gas holdup increases obtained when oil was injected indicated that bubbles were smaller or rose slower.
Oil-coated bubbles showed an enhanced deinking ability (larger brightness gains).
Use of silicone oil substantially reduced air requirements to match plant brightness gains.

10. Deinking flotation cells (Bowater) Ottawa