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ECF bleaching of eucalyptus kraft pulp: simulation of a mill with a high degree of closure
Akzo Nobel Pulp and Performance Chemicals.
RISE - Research Institutes of Sweden, Bioeconomy, Biorefinery and Energy.
Akzo Nobel Pulp and Performance Chemicals.
2017 (English)In: International pulp bleaching conference / [ed] Colodette J L, Gomes F J B, Suprema Grafica e Editora , 2017, p. 106-110Conference paper, Published paper (Other academic)
Abstract [en]

The composition of non-process elements (NPEs) in wood significantly affects the level of metals in the pulp in the bleach plant and contributes to the risk of forming precipitates. The possible degree of closure is often limited by calcium oxalate formation, mainly around the D0-stage, which can be prevented by increasing the temperature and/or decreasing the pH in this stage. This paper presents the effect of a decreased pH in the D0-stage when bleaching a eucalyptus kraft pulp as well as the influence it has on environmental parameters such as chemical oxygen demand (COD) and adsorbable organic halogens (AOX). The increased AOX measured when applying a low pH in the D0-stage was shown to be easily decomposed under process conditions. To be able to predict the effect on both the recovery cycle and the bleach plant itself as a consequence of increased closure of the bleach plant, a full mill simulation model (WinGEMS) was used based on a theoretical mill using the best available technology (BAT) in combination with data produced in laboratory trials. The model pulp mill was exclusively equipped with wash presses. According to the simulations, the effluent volume could be significantly decreased from 20.7 t/air dry tonne (ADt) pulp to 8.7 t/ADt in a D(EOP)DP sequence. Using a wood raw material with a calcium content of 520 mg/kg dry solids, no formation of calcium oxalate was predicted. However, for a wood raw material with a higher content, 800 mg/kg, calcium oxalate formation was likely to occur. By decreasing the final pH in the D0-stage from 3.0 to 2.5, formation of calcium oxalate could be avoided. At the effluent volume of 8.7 t/ADt, no fresh water was used in the bleach plant except for the water used for dilution of chemicals.

Place, publisher, year, edition, pages
Suprema Grafica e Editora , 2017. p. 106-110
Keywords [en]
Eucalyptus, ECF bleaching, water consumption, pulp mill, mill closure, modelling, scaling, non process element, AOX, COD, kraft pulp
National Category
Paper, Pulp and Fiber Technology
Identifiers
URN: urn:nbn:se:ri:diva-33017ISBN: 978-85-8179-134-0 (electronic)OAI: oai:DiVA.org:ri-33017DiVA, id: diva2:1172738
Conference
International pulp bleaching conference, August 28-30, 2017, Porto Seguro, Brazil
Available from: 2018-01-10 Created: 2018-01-10 Last updated: 2018-11-26Bibliographically approved

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CiteExportLink to record
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