TRANSITION-METAL PROFILES IN OPEN AND CLOSED KRAFT FIBER LINES

Transition metals exert a profoundly negative impact on ozone and pero xide bleaching of kraft pulps. This report presents the results of a c omprehensive study of metal profiles throughout the fiber lines of two mills. One mill ran a TCF (totally chlorine free) bleaching trial and metal profiles obtained during this trial are compared with profiles obtained during conventional (CD)(EO)DED bleaching Mill and laboratory data suggest that closure of ozone or peroxide bleach stages by cycli ng their effluent streams back to the brownstock washers could signifi cantly increase concentrations of Mn and Fe in the bleach plant.