Modeling of Alkali Impregnation of Eucalyptus Wood

In wood pulping processes, the quality of the impregnation stage has a significant influence on the final pulp properties. In this work, a refined version of a previously published model is used to analyze this operation stage. For liquor containing NaOH and Na2S, the study considers the reaction of wood acetyls and acidic groups. The Donnan effect is applied for analysis of ion concentrations in the wood−liquid interphase. The predicted concentration profiles are in acceptable agreement with the experimental results. The model is used afterward to simulate a batch or a cocurrent continuous kraft impregnation process. In the impregnating liquor, the alkali concentration is gradually reduced due to chemical reactions and alkali accumulation in the wood chips. The level of impregnation is finally analyzed considering different chip thickness values corresponding to an industrial chip stock sample.