The use of calcium hydroxide as alkali source in peroxide bleaching of kraft pulp

Anders Strand, Ekaterina Korotkova, Juuso Hakala, Erja Lindstedt, Stefan Willför

Research output: Contribution to journalArticleScientificpeer-review

Abstract

The feasibility of replacing sodium hydroxide with calcium hydroxide in peroxide bleaching of kraft pulp was assessed. The bleaching experiments were carried out in small scale on two different starting pulps, with a preliminary study and a more narrow follow-up study. The preliminary study showed that the required amount of Ca(OH)(2) was quite low compared to NaOH. The follow-up study showed that the same brightness gain and decrease in yellowness as 1% NaOH were achieved with 0.25% Ca(OH)(2), which could result in savings of 80-85% on the cost of bleaching alkali. Replacing NaOH with Ca(OH)(2) resulted in similar optical and mechanical properties as the reference pulp. The concentration of total organic carbon in the bleaching waters was in the same size range with NaOH and Ca(OH)(2). This study indicates that alternative alkali sources can be used in the peroxide bleaching stage of kraft pulp.
Original languageUndefined/Unknown
Pages (from-to)444–451
Number of pages8
JournalNordic Pulp and Paper Research Journal
Volume32
Issue number3
DOIs
Publication statusPublished - 2017
MoE publication typeA1 Journal article-refereed

Keywords

  • Calcium hydroxide
  • Alternative alkali
  • Brightness
  • Peroxide bleaching
  • Kraft pulp

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