Improved Contaminant Removal in Deinking Systems, 1997 Pulping Conference Proceedings

Contaminant removal at Ponderosa’s two new facilities in Pennsylvania and Washington has focused on new systems and equipment to remove difficult contaminants from mixed office waste (MOW) and the processing of that waste into a high quality pulp to compete with bleached virgin pulps.

The first level of priority in the design of the two new facilities was to remove stickies and micro stickies. The second priority was to process groundwood content and unbleached waste papers found in MOW without it negatively impacting the final pulp quality. The third priority was to remove color, fluorescence and minimize shade variation. The fourth priority was to remove non-impact, UV treated, and impact inks. And the fifth priority was to remove micro poly particles.

Removal of difficult to remove contaminants was necessary to accomplish these objectives. This required the project team to challenge and make many changes in what had been “typical deink plant systems design” for new deinking facilities. Systems where major changes and new equipment were required included: pulping, cleaning, screening, washing, water clarification, kneading, dispersion, bleaching, flotation, and a much tighter control of process variables such as temperature.

Some unique features utilized within the new s ystems include: high consistency pulpers with 1/8” extraction holes, fine screening with .004 inch slotted baskets, all light weight contaminant removal prior to kneading, fluidized drum washers, cooling towers for process water, a combination kneading / dispersion plant, minimized flotation, filters for fiber reclamation, ozone bleaching, high temperature peroxide bleaching, sand and fine barrier disc filters utilized in water clarification, and ultra filtration for effluent treatment.