High-Density Kneading: An Alternative to Dispersion, 1993 Recycling Symposium Proceedings

Don McBride

Dispersion has become a permanent part of today’s deinking system technology, primarily because it helps improve the appearance of paper produced from deinked pulp.

Although there are various types of dispersion equipment available, including pressurized or non-pressurized units, disc-type or deflaker-type refiners, and single- or double-shaft kneader-type units, all dispersion units are designed to:

- Facilitate ink detachment and reduce the size of ink particles

- Improve the visual appearance of the final paper product

- Mix bleaching chemicals with fiber

Using a kneading system ensures maximum removal of ink and contaminants and provides an attractive alternative to dispersing them into the pulp.

Depending on the type of equipment used, the kind of wastepaper to be deinked, and the desired quality of the finished product, dispersion systems are generally placed near the end of a deinking system, while kneading systems are generally placed after pulping and

coarse screening, prior to flotation and washing.

Once the type of equipment has been chosen, pilot plant trials performed in a facility that provides complete water circulation can help a mill choose the best sequence and chemical application for its operation.