Tcf Bleaching Of Eucalyptus Kraft Pulp: The Selection Of The Sequence And The Best Conditions

Bleaching was conducted with conventionally oxygen-delignified pulp. The residual lignin was lowered either with an OAqZO or an OAqPeracidO treatment. Kappa numbers between 3 and 5 were achieved without any viscosity penalty. The bleachability was better after ozone activation. A concentration of 0.25% ozone was more effective than 1.5% peracetic acid. Final brightness was above 90% ISO at similar strength properties. Final bleaching with hydrogen peroxide was made with only one stage. The addition of magnesium sulphate and sodium silicate improved the results. The lowest hydrogen peroxide demand resulted at temperatures below 100°C with a retention time of up to 24 h. The 90% ISO brightness level needed an input of less than 2% H2O2. Bleaching at 110°C accelerates the reaction, but yields inferior results in terms of peroxide consumption and viscosity.2311J517J521Süss, H.U., Eul, W., Helmling, O., Semibleaching of Kraft Pulp Using Oxygen and Hydrogen Peroxide (1989) Papier, 43 (7), pp. 318-323Vuorinen, T., Buchert, J., Teleman, A., Tenkanen, M., Selective Hydrolysis of Hexenuronic Acid Groups and its Application in ECF and TCF Bleaching of Kraft Pulps Proc. 1996 Intl. Pulp Bleaching Conf., pp. 43-51Nimmerfroh, N., Suss, H.U., Generation and Application of Peracids for Chemical Pulp Bleaching - A Cost Comparison (1996) Intl. Non-Chlorine Conf., , Orlando, FLNimmerfroh, N., Süss, H.U., Hafner, V., Überlegungen zum großtechnischen Einsatz von Ozon zur Zellstoffbleiche (1992) Wochenblatt für Papierfabrikation, 120 (21), pp. 860-868Bouchard, J., Nugent, H.M., Berry, R.M., A Comparison between Acid Treatment and Chelation Prior to Hydrogen Peroxide Bleaching of Kraft Pulps (1995) J. Pulp Paper Sci., 21 (6), pp. J203-J208Takagi, J., Ishigure, K., Thermal Decomposition of Hydrogen Peroxide and its Effect on Reactor Water Monitoring of Boiling Water Reactors (1985) Nuclear Sci. Engin., 89, pp. 177-186Sjödin, L., Norden, S., Extended Delignification with Oxygen and Hydrogen Peroxide in ECF and TCF Sequences Proc. 1994 TAPPI Pulping Conf., pp. 21-27Stromberg, B., Szopinski, R., Pressurized Hydrogen Peroxide Bleaching for Improved TCF Bleaching Proc. 1994 TAPPI Bleaching Conf., pp. 199-209Basta, J., Holtinger, L., Lundgren, P., Persson, C., Emerging Technologies in TCF Bleaching Proc. 1995 TAPPI Pulping Conf., pp. 53-57Devenyns, J., Renders, A., Carlier, J., Optimal Use of Hydrogen Peroxide to Design Low AOX ECF Sequences Proc. 1995 TAPPI Pulping Conf., pp. 281-288Süss, H.U., Nimmerfroh, N., Kronis, J.D., The Naked Truth on Hot Peroxide Bleaching (1997) Preprints 83rd Ann. Mtg., pp. B129-136. , Tech. Sect. CPPAAnderson, J.R., Wilkinson, W.D., Process Characterization of High Temperature Hydrogen Peroxide Bleaching: Caustic Addition (1997) Preprints 83rd Ann. Mtg., pp. B175-184. , Tech. Sect., CPPASüss, H.U., Die Delignifizierung von Sulfitzellstoffen mit Sauerstoff und Wasserstoffperoxid (1986) Papier, 40 (1), pp. 10-1