Avoidance of Adhesive Impurities by Mechanical Separation in Pressure Screens and Cleaners, 1999 Recycling Symposium Proceedings

Hubert Gaßmann

Adhesive disturbing substances entering the process through waste paper can cause all kinds of disruptions to and deficiencies in both the product and more importantly the production process itself. The production process should be understood as the complete process from the delivery of waste paper to reprocessing sewage. A multitude of preparing machines and chemical methods are available on the market which remove these adhesive disturbing substances, break them down mechanically so that they are no longer visible, bind them chemically or reduce their adhesiveness.

Seen from an economical standpoint it is still best to concentrate on removing the adhesive elements from the process. Dispersion and chemical neutralization have the disadvantage that the particles may restore themselves or agglomerate into even larger, disturbing particles during the subsequent process either due to their own activities or those of other materials acting as collectors. Where chemicals are used it is also possible that when interacting with other media and chemicals the initial deactivation of the adhesives may be cancelled.

The aggregates used for mechanical separation in pressure screens and cleaners must fulfill special requirements. Physical aspects must be taken into consideration, because if

acceleration is too strong the adhesive elements may significantly alter their form. When they change their form otherwise three-dimensional disturbing substances may stretch and become fiber-like. Many impurities are also comparable with fibers with regard to their density. Once the impurities have taken on a fiber-like form they are very difficult to separate.