In contrast to the flotation de-inking process in which small air bubbles serve as ink collectors the new and more energy-efficient adsorption de-inking technique relies on the adsorption of detached ink particles on the surface of small plastic granules. The energy savings result from the fact that this process can be performed at much higher stock consistencies and thus largely dispenses with the utilization of huge amounts of water. There are — at least on lab level - strong indications that even higher energy savings might be achieved if this adsorption process is integrated in the pulping process. In this case the relative motion between the plastic granules and the paper pulp would exert mechanical and thus dispersing stresses similar to those acting in ball mills. This would not only support the pulping process but simultaneously the detachment of the ink particles from the fibres as well as their comminution which eventually facilitate both subsequent adsorption and flotation. The latter is usually achieved by high consistency dispersion or kneading — the most energy-intensive sub-processes in recovered paper stock preparation. Adsorption deinking, therefore, could possibly allow the implementation of basic sub-processes in just one step. Results of corresponding investigations, which have been carried out in the meantime and which underlined the potential of this new approach will be presented in this paper.
展开▼
