Upgrading High Kappa Recycle Fibers Via Gas Phase Chlorine Dioxide Delignification, 1995 Pulping Conference Proceedings

Rene Ward, Sudhir K. Mendiratta, Ph.D., and Philip E. Quinnett

Charleston Technology Center,

Olin Chlor-Alkali Products

The use of high kappa recycle fibers in the production of high quality paper is increasing rapidly. For this application, the recycle fibers must be delignified prior to bleaching. Processes such as extended delignification and/or oxygen delignification may not be technically or economically feasible for a stand alone mini mill. The chemical recovery system and major equipment associated with aggressive delignification processes will limit the number of mills that can take advantage of the expanding uses of high kappa recycle fibers. In this paper, we will discuss a gas phase chlorine dioxide delignification process that results in greater than 70% reduction in kappa number. This delignification is achieved at kappa factors ranging from 0.04 to 0.09. Specifically, a 43 kappa fiber sample recovered from municipal solid waste and an 89 kappa fiber sample obtained from a local paperboard manufacturer are extracted to kappa numbers of 13 and 6.4, respectively. The extracted pulps are bleached to 80 - 84 ISO brightness in a DP or DED sequence. The AOX generated in the gas phase delignification process is compared to the AOX predicted by the NCASI model and the AOX measured for a medium consistency Dl00Epo stage. The BOD, COD and color data for the gas phase delignification stage are also presented.