BULK DELIGNIFICATION KINETICS AT SELECTED VERTICAL HEIGHTS WITHIN JACK PINE PLUS TREES

Pulping kinetics of extractive-free wood from jack pine trees sampled from the Fort Frances, the Atikokan and the Thunder Bay districts of O ntario, Canada, were investigated. Wood samples were cooked at three d ifferent temperatures: 140 degrees C, 155 degrees C and 170 degrees C with a white liquor concentration of 32 g/L sodium hydroxide and 10.4 g/L sodium sulphide (25% sulphidity). The results indicated that the a verage activation energy for pulping of trees from the Fort Frances, t he Atikokan and the Thunder Bay districts were 91.0, 81.0 and 81.4 kJ/ mol, respectively. The differences of activation energy for pulping be tween sapwood and heartwood were insignificant. Activation energy for pulping of wood increased from top to bottom of the tree.