Abstract:This study describes
the optimization of a eucalyptus elemental
chlorine-free (ECF) bleach plant to reduce adsorbable organic halogen
(AOX). The correlations between operating conditions of each stage
and pulp quality indices as well as the AOX content in wastewater
are analyzed, taking an ECF bleaching technology (D0EpPD1) as an example. The calculation models of pulp quality indices
and AOX content in wastewater are established. Then, an optimization
model aiming at minimizing AOX emission is structured. The… Show more
Chlorine dioxide is used extensively as the bleaching agent in the clean pulp bleaching process. To further improve the efficiency of chlorine dioxide delignification, this study discusses the effect of a new system of a high proportion of chlorine dioxide on lignin removal. When the mass ratio of chlorine dioxide to lignin was 4 in this system, 50% of lignin was removed in a short time. To optimize the new bleaching system, the effects of temperature and pulp consistency on the new system were studied. The ratio of lignin removed was 50% when the reaction time was 30 min, temperature was 25 °C, and the pulp consistency was 5%. Compared with traditional chlorine dioxide bleaching, high proportion of chlorine dioxide bleaching can shorten the reaction time by 50%, reduce the reaction temperature to 25 °C, and greatly reduce energy consumption and adsorbable organic halogen (AOX) production by 45%. The new system provides a novel idea for clean bleaching of pulp.
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