The Problems in Delignification of Dry Wood by Kraft Process
The objective of this study was to assess the causes of the problems arising in the CBC kraft cooking of several types of hardwood chips particularly in view of high dry matter but also in view of chip thickness and character of wood.High dry matter of processed chips influences negatively delignification. Similar effect on delignification is achieved by wood character (anatomic and morphological properties of cell elements, chemical composition, portion of heart and sapwood).Chips thickness has the most significant impact on delignification process comparing to other monitored characteristics. The increase of chips thickness by 1-2 mm has significant negative impact on monitored characteristics of kraft cooking – yield, Kappa number and amount of rejects.Displacement CBC kraft procedure is more sensitive on the deviation from standard conditions than conventional kraft cooking.The problems occurring during kraft cooking of different wood chips mixtures with high dry matter by CBC procedure are possible to resolve by technological and organizational precautions – separate chipping and storage of chips of heart and non-heart woods, preparation of thinner chips of heart wood, chips pre-vaporing before kraft cooking.