Assessment of reaction kinetic models describing delignification fitted to well-defined kraft cooking data

Many different kinds of delignification models have been presented, but so far no model has been widely accepted. In this paper two different reaction kinetics models are assessed, a three-phase model and a continuous distribution of reactivity model. The two have been fitted to well-defined data obtained from kraft delignification of Scots pine wood meal. Besides temperature, hydroxide ion and hydrosulphide ion dependence the model also considers the concentration of sodium ions. The performance of the two models, when fitted to data, is very good and fairly similar. However, the continuous distribution of reactivity model is a less complicated model to use and renders a more probable description of the chemical and physical mechanisms during delignification than the three-phase model. The continuous distribution of reactivity model is recommended for modelling the reaction kinetics of delignification.