ENZYME PRETREATMENT OF KRAFT PULP TO REDUCE CONSUMPTION OF BLEACH CHEMICALS

The use of chlorine in the bleaching of chemical pulps has to be minim ized to meet environmental requirements for the disposal of adsorbable organic halogens (AOX). The study deals with the production and chara cterization of the enzyme preparation used and the optimization of enz yme pretreatment prior to the bleaching sequence is discussed. The res ults show that pH has the greatest effect on enzyme effectiveness comp ared to time and temperature. Optimum conditions improved the enzyme e fficiency by 9.4%. The study describes the effect of the enzymes on va rious bleaching sequences such as (C/D)EDED, DEDED, ODED, OZEQP and OA QPAP. For sequences containing chlorine compounds, the use of enzymes decreases Kappa number but with a lower effectiveness of 5% on average and enhances final brightness, with a slight reduction in chlorine di oxide consumption.