Low Capital, High Return Modifications to Kraft Pulping Operations, 2001 Pulping Conference Proceedings

W. Ban, A. J. Ragauskas, L. A. Lucia--The response of the pulp carbohydrates under various pretreatment conditions was investigated using ion exchange chromatography (IEC). The results indicated that an increase in pulp yield from a mill green liquor-pretreatment process is a function of the preservation of the glucose sugars of the cellulose as opposed to the hemicellulose sugars. The effects of sulfide absorption during impregnation on delignification and pulp properties were also studied and comprised the bulk of the present studies. The relationship of sulfide absorption to the fate of the pulp carbohydrates and residual lignin has been explored. The experimental results indicate that sulfide absorption plays a critical role in prohibiting lignin condensation reactions and stabilizing cellulose during the kraft pulping process; specifically, less condensed lignin and increasing amounts of glucose were observed by NMR and IEC spectral analyses. Furthermore, factors affecting sulfide absorption by pretreatment process were studied, including varying the ratio of liquor to wood, temperature, and hydroxide ion concentration. The latter factors were varied to assess their contribution to sulfide absorption, the level of delignification, improvement in pulp qualities, and the balance of chemicals in the cooking process.