Response of Eucalyptus camaldulensis and Acacia mangium kraft pulp in different ECF bleaching options

In this study, the response of Eucalyptus camaldulensis and Acacia mangium kraft pulp to different options of ECF bleaching was investigated. Oxygen-delignified pulps of both species having similar kappa number (c.a. 12) were used. Both the pulps were prebleached using conventional ClO2 stage (D-0), combined use of ClO2 and O-3 (DZ), hot acid treatment before D-0 (A(hot)D(0)) and hot acid treatment before (DZ) i.e., A(hot)(DZ), hot ClO2 treatment (D-HT) and A(hot) followed by D-HT (A(hot)D(HT)). All prebleached pulps were finally bleached to 90%+ ISO brightness using D-1 option. The overall benefits of other options were not considerable compared to D-0 and (DZ). From the ClO2 consumption point of view, for a certain species, the option A(hot)(DZ) was the best. Instead of D-1 in final bleaching, pressurized hydrogen peroxide (PO) was also investigated in the case of D-0 and (DZ) prebleached pulps. (PO)-bleached pulp produced higher brightness stability but lower viscosity compared to D-1.