Improvement of Hardwood Pulp Yield in Continuous Kraft Cooking and Estimation of Pulp Yields (Part I)-Optimal Conditions for Yield Increase and Estimation Using Carbohydrate Analysis-

Abstract

The optimal conditions of isothermal cooking (ITC) for yield improvement of hardwood kraft pulp were established using Acacia mearnsii wood in a laboratory. The addition of both 1% sulfur and 0.04% soluble anthraquinone on wood gave an about 4.5-5% higher pulp yield at a kappa number of about 17. The highest yield was obtained when 70% of total active alkali and 100% of both PS and AQ were added at the beginning, and successively, black liquor was exchanged with fresh white liquor containing the remaining 30% of total active alkali just after the cooking temperature reached 135°C. A linear correlation was observed between pulp yields and ratios of xylose to glucose (X⁄G ratios) , liberated from the pulps by an acid hydrolysis. This result means that a pulp yield can be estimated by knowing an X⁄G ratio of the pulp. However, it was indicated that the linear correlation for Acacia mearnsii can not be applied to cooking of different wood species.