Refiner peroxide bleaching at Daishowa Port Angeles

Daishowa America's Port Angeles, WA mill produces RMP for use in directory paper. Higher brightness pulp is occasionally required for producing special grades. After evaluations were made of various tower brightening approaches, refiner bleaching with peroxide was ultimately chosen, avoiding large capital expenditures. This paper will outline the options considered for brightening, and the reasons for selecting refiner bleaching. The necessary equipment required to retrofit an older mill is described, with considerations for both safety and efficiency. Results of the first trials using peroxide are covered along with how problems encountered in the mill and on the papermachine were resolved. Finally the current situation is described including process conditions, achieved brightness gains and optimization.