Low Consistency Refining of a Non-Conventionally Cooked Pulp, 1999 Papermakers Conference Proceedings

William Josephson, Ph.D., Ulla Jansson, Umit S. Sezgi, Ph.D., Kjell Fagerstrom, Ph.D.

Two refining studies that used non-conventionally cooked pulp are examined in detail. In the first, a TCF birch market pulp was refined under a range of conditions appropriate to the pulp. The pulp was found to behave in the same manner as a conventionally cooked pulp. The energy requirements to achieve a given drainage level were as expected and the refined pulp had good strength and printing characteristics.

The second study was a long term effort that compared the refining characteristics of an non-conventionally cooked ECF softwood pulp with the characteristics of the ECF Kraft softwood pulp produced at the same mill prior to its conversion to the new cooking process. Low consistency refining and PFI Mill studies were done. The studies showed that the non-conventionally cooked pulps refined in a manner comparable to that of the conventionally cooked pulps. When refined under appropriate conditions the non-conventionally cooked pulp had the same energy requirements as the kraft pulp and had mostly similar properties. The refined non-conventionally cooked pulps did have a higher tear strength; this was probably due to the greater fiber length of pulp produced in the cooking process.

All of the studies have shown that the non-conventionally cooked pulps behave in the same manner as conventionally cooked pulps when subjected to a low consistency refining operation. While the mode of cooking does have some importance in determining the refinability of a pulp, there are numerous other parameters that also influence the fiber’s susceptibility to refining. These include extent of cooking (i.e., pre-bleaching Kappa number), mode of bleaching and, perhaps most importantly, the raw materials supplied to the cooking process.