Effect of Chlorine Charge on Delignification in the (CD), E and (EO) Stages, 1990 Pulping Conference Proceedings

A model for the percent of the Kappa number of an unbleached pulp which remains after chlorination (CD), conventional extraction E, and oxidative extraction (EO) has been developed. The model is based on the kappa numbers after the (CD), E and (EO) stages when three unbleached pulps, covering the kappa number range 24 to 35, were chlorinated at 8 equally spaced kappa factors in the range from 0.015 to 0.260. The percent kappa number remaining after chlorination is a linear function of the kappa factor consumed and is independent of the kappa number of the unbleached pulp. The percent kappa number remaining after extraction E is also a linear function of the kappa factor consumed up to kappa factor 0.13, where a break occurs beyond which delignification is less efficient. The percent kappa number remaining after an (EO) stage parallels that of the E stage up to kappa factor 0.13, beyond which the lines converge. The model increases understanding of the delignification stages of bleaching, and presents mills with a new method for diagnostics and control. It also gives researchers a basis for comparison of the delignification properties of other chlorination and delignification chemicals such as chlorine dioxide, nitrogen dioxide, ozone, oxygen and peroxide.