Recycling of Water in Bleached Kraft Pulp Mills by Using Electrodialsis

摘要

Conservation of water in bleached kraft pulp mills by recycling the bleach plant effluent directly without treatment will cause accumulation of inorganic "non-process elements" and serious operational problems. In htis work, an electrodialysis process is being developed for recycling the acidic bleach plant effluent of bleached kraft pulp mills. IN this process, electrodialysis functions as a selective kidney to remove inorganic NPEs from bleach plant effluents, before they reach the recovery cycle. Acidic bleach plant effluents from several mills using bleachign sequences based n chlorine dioxide were characterized. The total dissolved solids were mostly inorganic NPEs. Sodium was the predominat cation and chloride was present at significant levels in all these effluents. In laboratory electrodialysis experiments, selective removal of chloride and potentially harmful cations, such as potassium, calcium, and magnesium, were removed efficiently. Rejection of organic compounds was up to 98