A proposed heterogeneous kinetic model for oxygen delignification of kraft pulps

A mathematical model is formulated to characterise the kinetics of oxygen delignification. The model is developed by assuming that the delignification is a heterogeneous process, and the density of lignin reactive sites and the growth rate of the reaction zone bl lignin structure are the factors controlling the delignification rate. The spreading rate of the reaction zones from these reactive sites is assumed to follow a power-law with respect to the reaction time. The effects of temperature, oxygen pressure, and alkali concentration on the model parameters. which also depend on pulp types, are determined using experimental results obtained from tests with different kraft pulps.