Removal of Chloride from Recovery Boiler Ash - Recent Results from Pilot Tests, 1998 International Chemical Recovery Conference Proceedings

Removal of chloride from recovery boiler ash has been considered an attractive possibility to remove chloride from mill’s recovery cycle. An essential part of chloride removal research project by Ahlstrom Machinery Corp. was made up of the experimental trials on millsite with a full scale unit. The main goal of the tests was to demonstrate the process chosen and to evaluate the potential restrictions of it. Na2 S04 was crystallized by concentrating recovery boiler ash water solution and crystals were separated from the solution. Chloride and most of potassium remained in liquid phase enabling dumping of these non-process elements. The overall results gamed in the pilot tests on millsite matched well with the theories and statements presented in the literature. Based on the results the concept fulfils the original goals set to the process. A Cl removal efficiency of 90% and degree of alkaline to be returned to recovery cycle of 80% are attainable.