Refining Variables Relating to OCC Property Development, 1991 Pulping Conference Proceedings

Pilot plant trials were carried out to determine the optimal conditions for refining of OCC. Two pulps were studied. One Pulp was a commercially produced OCC collected from an operating mill system. The other pulp (in order to have an abundant supply of uniform material for pilot plant trials) was produced in the pilot plant by blending rolls of liner and corrugating medium produced at the same mill. The liner and medium were manufactured from approximately 30% OCC and 70% virgin pulp. For both OCC pulps three plate patterns were run in a conventional low consistency (3.5%) refiner, and resulting pulp properties and energy requirements were compared to those of a high speed single disk refiner operated at high consistency 100%.

In the low consistency refiner, plate pattern was determined to have a slight effect with the mill pulp but not with the pilot plant made pulp. This is believed to be related to the overall level of fiber quality.

The higher consistency operation of the single disk refiner generally produced results that were at best equal to or slightly inferior than those from the low consistency process. Burst and compressive strength at equal freeness levels were equal or lower for the high consistency process while much more energy was consumed. Tear and porosity were higher at a given freeness level for the high consistency refined pulps.

Low consistency refining was concluded to be the best unit operation for enhancing occ properties, with the sensitivity of the operation being dependent on the furnish quality. The response of OCC to this type of treatment in the future will likely be affected by the general trend of increased recycling and the resulting furnish degradation.