Electrodialysis field test for selective chloride removal from the chemical recovery cycle of a kraft pulp mill

Chloride accumulation is a serious issue in the kraft pulping process. Chlo ride can be selectively removed from dissolved electrostatic precipitator d ust (ESP dust) in the kraft chemical recovery cycle by electrodialysis with monovalent-selective anion-exchange membranes. In a pilot-scale field test , this process was investigated (total run time, 750 h). The test was perfo rmed at about 3.5% of full scale. The process showed outstanding performanc e and no significant membrane fouling. In feed-and-bleed operation, chlorid e removal levels of 94% and 61% were tested. The energy consumption for ele ctrodialysis is low (120 kWh per metric ton of chloride removed at a 63% ch loride removal level). The process performed very well even with no feed pr etreatment, polarity reversal, or membrane cleaning.