Extending Delignification with AQ/Polysulfide, 1994 Pulping Conference Proceedings

H. Jameel, J. Gratzl, D. Y. Prasad, S. Chivukula

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 delignification can 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 cooing are proven technologies that can decrease the kappa number to the bleach plant, these two options require large capital investments and the lad to the recovery boiler is increased. The using of chemical additives (AQ, PS) is a low capital investment option for decreasing the kappa number and minimizing the impact on the recovery boiler load. Additionally, a higher bleached pulp yield is possible.