Minimizing fouling in spiral heat exchangers at a BCTMP mill

This paper investigates the cause of calcium oxalate (CaC2O4) fouling in spiral heat exchangers. CaC2O4 Solubility decreases with lowering temperature. The predicted precipitation rate due to temperature difference was consistent with the observed fouling rate. This observation suggests that the effluent supersaturates and forms precipitate (scale) upon contact with the cold heat exchanger surface. Suspended particles then accumulate and cause rapid fouling. This Study recommends using physical separation methods and partial replacement of NaOH with Mg(OH)(2) during alkaline bleaching to reduce CaC2O4 content and minimize fouling.