Kinetic models for all chlorine dioxide and extraction stages in full ECF bleaching sequences of softwoods and hardwoods

Abstract

We present new and improved semi-empirical mathematical models for all the chlorine dioxide stages and extraction stages (including oxygen and/or peroxide reinforced) in a full elemental chlorine free (ECF) bleaching sequence. The models predict variations of kappa number, pH, brightness, and bleaching chemical consumption at each step of multistage ECF bleaching sequences. Our aims were to improve the kinetic and stoichio- metric equations involved in the chlorine dioxide stages [Do, D1, D2] for their predictability for different kinds of soft-wood and hardwood pulps and to model the extraction stages with or without oxygen and/or hydrogen peroxide reinforcement [E, (EO), (EOP), (EP)]. The predicted results fit very closely to a wide range of laboratory and literature data, and the predictability was extended to a greater variety of pulps (softwoods and hardwood pulps, kraft or other alkaline pulps).