Evaporation of Acidic Effluent From ECF Bleaching, Reuse of the Condensate and Further Processing of the Concentrate, 2000 Environmental Conference Proceedings

- O. Dahl, J. Niinimaki -- Environmental concern and tighter public regulations have created new pressures to reduce effluent loading from kraft pulp bleaching during the past decades. This trend has forced both pulp mills and the related engineering industries to develop and optimize equipment for the pulping processes, which fulfils these demands. New pulp washers and washing systems connected with the introduction of new oxygen-based reagents have in particular provided considerably improved tools for reusing process water and thereby essentially reducing effluent discharge or even allowing the implementation of a totally closed water circulation system in kraft pulp bleaching. The study was performed mainly on a laboratory scale at the University of Oulu, but some pilot-scale tests were also performed to confirm the findings of the laboratory-scale evaporation test. Another aim of the pilot-scale tests was to produce enough concentrate for further processing.