OXZP sequence. Influence of the ozone bleaching on the hydrogen peroxide stage properties

An OXZP bleaching sequence has proved to be a good choice in order to control both viscosity and brightness of the bleached pulp. The Z stage has been optimized applying a four variable statistical sequential plan. The variables and applied ranges were: mass of dry pulp (10-20 g), ozone inlet concentration (20-50 mg/l), bleaching flow (80-220 Al/h), ozone dose (0.25-0.65 % o.d.p.). The influence of these variables on brightness, viscosity and kappa number was examined in the Z stage as well as P stage. The resulting models in the Z stage predicts variations for brightness, viscosity and kappa number respectively, from 74.6 to 85.6 % ISO, from 496 to 876 cm(3)/g and 0.44 to 2.27. The resulting models in the P stage predicts variations for brightness and viscosity respectively from 84.2 to 92.7 % ISO and 568 to 857 cm(3)/g. Kappa number was not studied in this stage because the values in all the experiences were very similar.