THE STOICHIOMETRY OF CHLORINE DIOXIDE DELIGNIFICATION OF SOFTWOOD PULPS AFTER OXIDANT-REINFORCED EXTRACTION, 2011 International Pulp Bleaching Conference

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A generalized, steady-state model has been developed for estimating bleaching delignification and/or chlorine dioxide consumption for sequences that employ oxidant-reinforced extraction. The model is based on Germgård’s stoichiometric model for the D0E1 sequence, which relates chlorine dioxide consumption to post-extracted kappa number. The inte-grated stoichiometric model of Germgård’s was modified, in which the extracted kappa number was normalized to the incoming kappa number. This mathematical transformation allows for various brownstocks with different kappa num-bers to be model as a single curve whereby the shape of the consumption curve is related to the stoichiometric parameter. It was determined from analyzing various softwood bleaching studies that this stoichiometric parameter could be ex-pressed as a simple function of oxidant-reinforced extraction conditions (e.g, extraction temperature and peroxide do-sage). The generalized delignification model forecasts chlorine dioxide consumption with small relative deviations from the reported experimental values, typically ±3% to ±10%. This model is relatively simple with a minimum number of equation parameters to determined, and could be used with other steady-state brightening stage models to predict bleach consumption.