Wet Storage of Hickory Pulpwood in the Southern United States and Its Impact On Bark Removal Efficiency, 1995 Pulping Conference Proceedings

M. L. Belli

Mississippi State University

Compared to other hardwood species, true hickory (Carya sp.) is extremely difficult to debark during much of the year. Ease of bark removal is a direct function of the shear strength of the cambium. The strength of this layer in true hickories is such that the forces generated in a debarking drum are not sufficient to overcome it for much of the year. This study, in cooperation with Gulf States Paper and Coker Chip Mill of Tuscaloosa, Alabama, investigated the effect wet storage has on facilitating bark removal of hickory using an existing drum debarker. A total of 700 tonnes of hickory logs were collected and placed in two piles, one under a sprinkler system and the other in dry storage. Cambial strength was monitored over time by taking increment cores and performing a mechanical shear test at the wood bark interface. When average cambial shear strength in the wet pile dropped below 1000 kPa, both piles were recovered and processed through the debarking drum. Chip samples were collected and bark content determined through hand separation. Accepts bark content for unscreened material was 3.9 percent for dry storage, 2.5 percent for wet stored material. A subsample of about 115 tonnes of the wet stored material and a few tonnes of the dry were debarked using a flail debarker. Accepts bark content for unscreened wood chips was 0.5 for wet stored material. The flail removed very little bark from the dry logs.