Influence of Acid Leaching of Chips on Environmental and Process Performance of Eucalypt Pulp Production, 2009 TAPPI Engineering, Pulping, Environmental Conference

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Acid leaching of chips is a promising technology for reducing non-process elements in kraft pulp manufacturing. The technique consists of pre-treating chips with an acid solution, under appropriate time and temperature conditions prior to kraft pulping. The purpose of this study was to evaluate acid leaching of two eucalyptus woods exhibiting very different characteristics prior to modified kraft pulping. The effects of acid leaching on oxygen delignification performance, pulp bleaching, physical and mechanical properties of bleached pulps and on characteristics and treatability of effluents generated were determined. Unleached chips (reference), those leached with sulfuric acid and those leached with effluent from the acid stage (A) were cooked by a modified kraft process and the pulps obtained were oxygen-delignified and ECF bleached by A/D(PO)DP and A(PO)DP sequences. Acid leaching considerably reduced metals contents in the chips. Pulps produced from leached chips showed improved performance during oxygen delignification and ECF bleaching over reference pulps. Bleaching effluents after leaching had similar treatabilities to those of reference pulps. Treated effluents from A(PO)DP bleaching presented slightly higher organic loads and lower AOX than the treated effluents from A/D(PO)DP bleaching.