State of the Art ECF: Pulping and Bleaching with Oxygen, Ozone, and Chlorine Dioxide Part 2, 1996 Pulping Conference Proceedings

Gordon Homer

Scott Johnson

Michel Epiney

Air Liquide Canada

The combination of oxygen, ozone and chlorine dioxide in the pulping and bleaching processes will enhance the overall mill performance and will deliver a very cost effective ECF pulp product. Aside from its inherent environmental and marketing advantages, such a combination reduces significantly the consumption of chlo-rine dioxide over standard ECF pulp and could be the basis of the “closed” mill without having to go the TCF route. The use of oxygen delignification has significant yield advantages over extended cooking. The combination of ozone and chlorine dioxide in a single stage gives a powerful bleach sequence that can accommodate much higher Kappa #‘s with corresponding yield increases than the ac-cepted 10 Kappa for TCF bleaching. The mill implementation of ozone with chlorine dioxide can be done at low, medium or high consistency. Three mills in Finland, Brazil and South Africa are proceeding with two of the three processes. This paper will review oxygen delignification and the impact on yield and loads to the boiler. The combination of ozone and chlorine dioxide in high and medium consistency will be revis-ited in existing applications, and a process to accommodate a low consistency application will be introduced. Uses of the oxygen rich vent gas from an ozone stage previously presented will be mentioned so that the over all concept can be economically reviewed on a mill by mill basis.