High Efficiency Magnetic Deinking: A New, Simple, and Effective Approach for Cleaning Difficult-to-Deink Recovered Fibers, 1996 Pulping Conference Proceedings

Nipun Marwah

Westvaco Corporation

A novel approach to deinking recovered papers containing laser, electrostatic, and other non-impact inks has been demonstrated in laboratory, pilot, and mill trials. This new process is designed to allow more extensive use of a growing low cost fiber source in high grade papers. The unique feature of this new and relatively simple process, for which patent claims have been allowed, is the attachment of ink particles to a magnetic carrier material followed by removal of the resulting ink-carrier agglomerates using a magnetic field. Unlike alternative approaches, where separation is generally based on size or density differences, the separation in this process is based on natural and induced magnetic character of ink agglomerates. Extended mill trials using a commercially available, high gradient magnetic separator have confirmed efficient deinking of recovered fibers using this process. High-quality fine papers have been manufactured incorporating, as a portion of the furnish, fiber recovered from non-impact printing using this new process. The level of Tappi ink particles (>220 microns in diameter) is readily reduced to acceptable levels of less than 5 ppm with virtually no fiber loss. Commercial approaches for deinking papers containing laser inks provide comparable ink removal only if 20-25% of the fiber resource is rejected. The magnetic deinking technique may be implemented rapidly and at relatively low capital cost for removing non-impact inks. Laboratory experiments indicate that this new process may be extended to recover fiber from reject streams in existing deinking lines and to remove sticky contaminants from recovered waste paper.