ABSTRACT
The bleached pulp market has been working to provide brightness levels at values of 92% ISO respecting, however, environmental standards and seeking for less aggressive processes. Then, the additional chlorine dioxide that would be necessary to lift brightness has been replaced by hydrogen peroxide. The present study aimed to evaluate the influence of hydrogen peroxide charge, pressure and temperature variation in the bleaching sequence D0(E+P)D1(P+O). It was used industrial kraft pulp, from hybrid of Eucalyptus urophylla X Eucalyptus grandis, oxygen-delignified, whose initial characteristics were: brightness 61.8% ISO, viscosity 36.9 cP and kappa number 8.9. The last stage (P+O) was performed varying the hydrogen peroxide charge (3 kg/t and 6 kg/t), temperature (95°C and 105°C) and pressure (0 atm and 5 atm). To evaluate the effect of such variations over cellulosic pulp, viscosity, brightness and brightness reversion tests were carried out according to TAPPI standards. In general, increase of hydrogen peroxide charge (from 3 kg/t to 6 kg/t) caused a small increasing on brightness values and a small viscosity decreasing on the cellulosic pulp. The increase of 10°C in temperature had a positive effect on brightness parameter, increasing the respective values, on the other hand, for the viscosity analysis the achieved values showed a reduction tendency. For the variation of oxygen pressure it was also observed brightness increasing and viscosity decreasing.
Keywords:
chlorine dioxide; pressurized peroxide; kappa number