Model-based kraft cooking optimisation

Abstract

A recently proposed model for kraft delignification kinetics is used to generate optimum operating conditions for the production of kraft pulp. In contrast to previous models, the optimal profiles for temperature, [OH] and [HS] support the current operating practice in mill digesters. The optimisation results suggest coupling as high a [HS] as possible with a low [OH] but not below 0.2 M, at a low temperature for as long a cooking time as practical. It is also shown that the optimal [OH] conditions depends on whether the [HS] or the sulfidity is kept constant. These optimisation findings are summarised in a set of updated recommended procedures for industrial digester operation in order to maximise yield and selectivity.