Extending Delignification withAQ/Polysulfide, 2002 Kraft Pulp Yield Anthology

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The kappa number going into the bleach plant will have to be lowered to meet requirements for the new Cluster Rules being proposed by the EPA. The options proposed for decreasing the kappa number have included using oxygen delignification and/or extended digester delignification. Extended digester delignificationcan be implemented by modifying the cooking process (EMCC, RDH SuperBatch, EnerBatch) or by using chemical additives (anthraquinone (AQ),polysulfide (PS)). Even though oxygen bleaching and modified cooking are proven technologies that can decrease the kappa number to the bleach plant, these two options require large capital investments and the load to the recovery boiler is increased.