Practical Mill Experience With The Use of Hydrogen Peroxide Reinforced Extraction Stages to Reduce and/or Eliminate the Use of Elemental Chlorine in Hard, 1992 Environmental Conference Proceedings

Because the use of elemental chlorine in the bleaching of kraft pulps is the major contributor to the total level of AOX generated in the mill, this paper outlines practical mill experience showing that the level of chlorine can be significantly reduced or eliminated by the addition of hydrogen peroxide to the first and maybe second extraction stage(s) while maintaining brightness targets for hardwood kraft pulps.

For every kilogram of hydrogen peroxide (as 100%) added to the first extraction stage, the level of elemental chlorine can be reduced by 2 to 3 kilograms. To completely eliminate the use of chlorine, it may be necessary to increase the level of chlorine dioxide used in the chlorination stage. This extra ClO2 requirement can be achieved by the addition of hydrogen peroxide to the second extraction stage thereby reducing ClO2 requirement in both Dl and D2 without the additional cost of increasing Cl02 generating capacity.

To summarize, the level of elemental chlorine used, and hence the amount of AOX generated, can be significantly reduced, with minimal capital investment, by the addition of hydrogen peroxide to the first and maybe second extraction stage(s) for hardwood kraft pulps.