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

Deinking of recycled pulps is an important operation intended to provide pu lps appropriate for making paper and paperboard products from recycled wast epaper. Conventionary, deinking of recycled pulp is conducted in a flotatio n cell equipped with an agitator. We have investigated the applicability of a new flotation cell based on a column without an agitator present to acco mplish the deinking of typical wastepaper feedstocks and also a feedstock c onsisting of rejects from a conventional deinking cell. Experimental result s on the deinking operation indicate that it is possible to achieve deinkin g of a mixture of photocopier and laserprinted paper in the column flotatio n 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 f lotation 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 p lant. We found that deinking of the rejected waste could yield significant usable fiber. This indicates the potential of the column flotation techniqu e in enhancing the reuse of a waste component thus reducing the volume of d einking waste rejected into the environment. (C) 2000 ACEEE Published by El sevier Science B.V. All rights reserved.