New Chipping Technique For Kraft Pulping, 1998 Breaking the Pulp Yield Barrier Symposium Proceedings

Chip quality is always the first mportant factor in kraft pulping. According to modern penetration and diffusion theory, chips should ideally be long and thin. A new chipping technique has been developed to meet this requirement, in which chip thickness and length can be freely chosen. With this new chipping technique chips can be cut to any preset thickness and length without a size profile. Screening is not needed before cooking.

In this study, the effects of disk speed and cutting (spout) angle on pulp properties were investigated by laboratory cooking and beating. Sawmill chips containing no pins were used as reference. It was found that disk speed from 350 to 750 rpm and a cutting angle consisting of the regular angle plus two degrees are the optimum choice for mill operations. Under these chipping conditions, the new chips result in pulp properties that are comparable to those produced by reference chips, or better. All new chips were found to be superior to the reference chips in tear strength at comparable tensile strength.These results imply that more uniform pulping was achieved.

This new chipping technique offers a great opportunity for the maximum utilisation of raw materials, simplification of the woodhandling process and more uniform kraft pulping.