Kraft Delignification Kinetics Based on Liquor Analysis, 1993 Pulping Conference Proceedings

A mathematical model describing the delignification kinetics based on real time liquor analysis has been developed. The material balance model used, based on the on-line liquor analysis, predicts lignin content of the pulp every five minutes. This inferential method eliminates the difficulty of having to withdraw the pulp sample from high pressure and temperature cooking conditions for analysis. This method also has the advantage of collecting more data from a single cook. Effective alkali, sulfide concentration, total solids and the lignin content of cooking liquor were measured on-line using conductivity, ion-chromatography, refractive index and ultraviolet absorbance analysis, respectively. Kraft cooking experiments with several initial effective alkali and sulfidity levels were conducted in a laboratory digester on screened softwood chips for data collection and model development. This model incorporates initial and bulk delignification phases as these are the regions of industrial importance.