Modern Bleach Plants Closure and Bleaching Strategies

摘要

A conventional ECF sequence is difficult to close without risk of process problems such as corrosion in the recovery system.With light ECF bleaching including a high consistency ozone stage followed by an alkaline stage without an intermediate washing stage,the water consumption and the COD discharge can be reduced considerably compared with a conventional ECF sequence.The use of ozone in the bleaching has also shown to be efficient to lower the brightness reversion of the bleached pulp.One cause of brightness reversion is hexenuronic acids,HexA,in pulp.Ozone reacts very selectively with HexA and therefore pulps with high HexA content are well suited for bleaching with ozone.