Influence of the Diameter of Norway Spruce Thinning Logs on the Quantity and the Quality of Thermo-Mechanical Pulp, 1999 International Mechanical Pulping Conference Proceedings

Guillaume Chantre, Claude Couratier & Thierry Fauchon

AFOCEL

Michel Petit Conil

Centre Technique du Papier

In order to know whether average diameter of thinning logs can affect the production level and the properties of Norway spruce TMP, different stands representing contrasted sites are studied for both wood and TMP analysis. Two aspects are studied : the influence of diameter on (i) the yield of TMP considering the two reception units stere and fresh ton, and (ii) the TMP properties.

The wood sampling allows the establishment of relationships between wood basic density, bark content, moisture content (as dependent variables) and diameter log (as independent variable), taking also into account the influence of age and height. Combining these results with wood waste in the barking drum, calculations are made and prove TMP production per stere to vary from 180 oven-dry kg for an average diameter less than 10 cm to 220 kg for an average diameter of 15-20 cm. Evaluations are also made for the Yield of TMP per ton, depending mainly on the height of the log within the tree, and the duration between harvesting and pulping.

First prospecting is done on the influence of diameter and growth pattern on the TMP properties. TMP of 20 trees representing a rapid grown stand and a slow grown stand are obtained with the CTP high yield pilot plant with defibering under pressure, then refining at atmospheric pressure. The rapid grown stand gives a brightness higher than brightness of the slow grown stand, with shorter fibers, and higher coarseness, but log diameter is not a discriminate parameter.