Wastepaper Quality Development for Packaging Papers - Fractionation or Whole Stock Refining?, 1998 Recycling Symposium Proceedings

Whether or not to use fractionation technology will become an issue of increasing importance to New Zealand’s paperboard packaging industry as impending changes occur in the nature of the wastepaper used, moving from a predominantly OCC base towards lower grade mixtures due to increasing demand. In this study, the potential for fibre fractionation and reject refining to improve the quality of a possible future wastepaper stock has been compared to the gains achieved by whole stock refining. Pressure screens were used to fractionate a wastepaper stock into short (accepts) and long fibre (rejects) streams; effective fibre separations were achieved and found to be highly dependent on the screen basket/rotor combination used and to a lesser degree on operating variables. The rejects were relined using a pilot scale refiner before being recombined with the accepts. Upon recombination, limited increases in short span compression strength were observed with minimal effect on other strength properties and freeness relative to the feed stock. At common energy inputs, superior short span compression strength improvement was achieved with whole stock refining, although with the expected loss of freeness. The work tends to support the view that whole stock refining can be as effective as fractionation with reject refining in developing wastepaper quality.