Mechanical Pulp Quality and Fractionation. Part I: Upgrading Newsprint TMP for Value-Added Grades

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. When newsprint TMP was processed in the hydrocyclone fractionation system followed by APT and reject refining, the treated pulp was suitable for making a lightweight coated (LWC) grade with substantially less reinforcing chemical pulp. The overall specific energy consumption was also similar to 15% less than that of a typical commercial TMP 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.