Scaling and Bleaching Chemicals Consumption: A Mill Case, 2002 International Pulp Bleaching Conference Proceedings
Paulo A. Barata and Isabel S. Marques
Portucel changed the filtrate washing circuit in bleach plant from separate acidic/alkaline lines to a countercurrent system with a jump from the last to the first chlorine dioxide stage. This modification resulted in a decrease in scaling in wash diffusers of the Eop stage, improvements in final bleached pulp brightness (0.7% increase), and reduction of bleaching chemical consumption (7-8% less oxidant and a 25% reduction of soda in extraction stages). The pulp acidification prior to D1 stage is no longer needed, which resulted in a decrease of 60% in sulfuric acid consumption. With an investment of 250 thousand euros, an annual return of around 2 million euros was achieved.