Removal of Sodium Chloride from the Recovery Boiler Salt Cake Using Aqueous-Aqueous Separation Technique, 1994 Environmental Conference Proceedings

T. S. Prakash, Brij M. Moudgil

Water conservation and reuse in the pulp and paper industry has lead to the development of closed system processes which result in increase of sodium chloride levels in the plant water system. Presence of sodium chloride in the recovery boiler smelt is known to pose a safety hazard in boiler operation. In order to prevent the chloride buildup in the plant water system, removal of sodium chloride from the recovery boiler salt cake has been attempted using an aqueous-aqueous separation technique. The dissimilar partitioning behavior of multivalent and monovalent chloride from bivalent sulfate and carbonate (the principal components of recovery boiler salt cake). A 68% reduction in the chloride content with more than 90% recovery of sodium sulfate and sodium carbonate, and 98% of recovery of the polymer has been achieved in a single step. Initial results indicate that the recovered polymer can be recycled in subsequent chloride reduction steps. Chloride removal from synthetic salt mixtures and recovery boiler salt cake is discussed.