Deinking of recycled pulps using column flotation: energy and environmental benefits

Deinking of recycled pulps is an important operation intended to provide pulps appropriate for making paper and paperboard products from recycled wastepaper. Conventionary, deinking of recycled pulp is conducted in a flotation cell equipped with an agitator. We have investigated the applicability of a new flotation cell based on a column without an agitator present to accomplish the deinking of typical wastepaper feedstocks and also a feedstock consisting of rejects from a conventional deinking cell. Experimental results on the deinking operation indicate that it is possible to achieve deinking of a mixture of photocopier and laserprinted paper in the column flotation cell. The performance of the column, as measured by the resultant pulp's brightness and ink particle size distributions, is comparable to that of a conventional laboratory cell which incorporates severe agitation regimens. Thus, it is found that the agitator can be eliminated by using the column flotation design which could yield significant electrical energy savings in addition to savings in capital costs and other operational and maintenance costs. A series of deinking experiments were also performed on a feedstock consisting of rejected waste obtained from a conventional cell in a pilot plant. We found that deinking of the rejected waste could yield significant usable fiber. This indicates the potential of the column flotation technique in enhancing the reuse of a waste component thus reducing the volume of deinking waste rejected into the environment. (C) 2000 ACEEE Published by Elsevier Science B.V. All rights reserved.