Microwave Pretreatment to Decrease Pulping Energy and Chemicals, 2004 Paper Summit, Spring Technical & International Environmental Conference, (including Papermakers; Process Control, Electrical & Information; Product & Product Quality)

This project is evaluating the feasibility of microwave pretreatment of softwood logs and chips to decrease the cooking chemicals and process energy required for conventional Kraft pulping. In previous years, it was established that the microwave pretreatment of hardwood coppice permitted simultaneous decreases of pulping chemicals and H-factor, a measure of process energy and time, by 30% with comparable kappa numbers and pulp strengths. Very large wood sections, such as 4 inch diameter by 4 inch long hardwood coppice sections, could be pulped under low chemical - low H-factor conditions to comparable kappa levels. These studies indicated that microwave pretreatment could greatly increase mill throughput while decreasing the energy required to produce a given amount of pulp. In the last year, studies have focused on the evaluation of microwave pretreatment of Southeastern softwood chips. Reductions in pulping chemicals and H-factor >45%, have been demonstrated for softwood chips in both low kappa and linerboard regimes. Additionally, pretreatment of oversized chips has been shown to permit up to 30% oversized chips to be pulped with mill-run mixed size chips. A prototype RF applicator, based on a robust, scaleable, 24/7 industrial system, but designed to treat both logs and chips has been developed, leased to ORNL, and is being used in this project. Future studies are targetted toward larger-scale pulping studies, evaluation of the use and economic benefits of this technology in mill situations, and evaluation of methods for further decreasing the chemicals and energy required to produce pulp.