MECHANICAL PULP QUALITY AND FRACTIONATION. PART I: UPGRADING NEWSPRINT TMP FOR VALUE-ADDED GRADES

摘要

Previously developed technologies involving fractionation and the alkaline peroxide treatment (APT) of rejects were used to produce pulps for value-added grades using TMP from the latency tank of a newsprint mill. Hydrocyclones were able to selectively fractionate and remove undeveloped fibres from a blend of long, medium, and short fibres. Savings of 18% in reject refining specific energy were achieved when hydrocyclone rejects were treated with alkaline peroxide before refining. We showed that when newsprint TMP is processed in the hydrocyclone fractionation system followed by APT and reject refining, the produced pulp was suitable for making a lightweight coated (LWC) grade with substantially less reinforcing chemical pulp. The physical, optical, and surface properties were similar to those of a commercial LWC grade. Test results of fibre rising, coating uniformity, and holdout, as well as printability analysis, also showed that the performance of the experimental paper was comparable to that of the commercial reference LWC grade. The overall specific energy consumption was also approximately 15% less than that of a typical commercial TMP pulp for LWC grades. With the implementation of technologies involving fractionation and the alkaline peroxide treatment of rejects, an existing newsprint refining installation could be maintained and used to produce pulp for value-added grades with minimal capital investment.