Reconfiguration of a Five-Stage Bleach Plant for Ultra-Low AOX Discharge, 1996 International Pulp Bleaching Conference Proceedings

Jack Histed

Jack Histed Consulting Ltd.

New Elemental Chlorine-Free (ECF) bleach plants equipped with an oxygen prebleach are capable of limiting adsorbable organic halogen (AOX) discharges to 0.2kg/t. This paper shows how existing five-stage conventional bleach plants can be reconfigured, at low capital cost, to achieve similar low AOX levels while producing high-brightness, high strength pulp without an increased load to the recovery furnace. A process known to minimize AOX formation and strength loss in the oxygen stage while maximizing oxygen delignification is combined with a process known to maximize in-plant destruction of AOX . This is followed by a process which features superb on-line chlorine dioxide stage control and is known to result in improved pulp strength. This combination of technologies will be of most interest to mills that wish to avoid conventional oxygen bleaching for either technical or financial reasons.