IMPROVEMENTS IN PULP PROPERTIES BY ALKALI PRE-EXTRACTION AND SUBSEQUENT KRAFT PULPING WITH CONTROLLING H-FACTOR AND ALKALI CHARGE

Kyujeong Sim, Hye Jung Youn, Hwi Cho, Heenae Shin, Hak Lae Lee

Abstract


The objective of this study was to determine the processing conditions for obtaining improved pulp properties from the kraft pulping process with an alkali pre-extraction stage. Before the kraft pulping, a pre-extraction of hemicelluloses from mixed hardwood chips was performed with two different alkali concentrations (3% and 12% as Na2O) at 150 °C for 90 minutes. The kraft pulping of the pre-extracted chips was then conducted in two ways: with either the H-factor alone controlled or with both the H-factor and the alkali charge controlled. When the chips were pre-extracted with the 3% alkali charge and with the kraft pulping controlled to an H-factor of 500, the yield and properties of the pulp were higher than those of the reference kraft pulp. The 12% alkali pre-extraction and kraft pulping resulted in a low yield of screened pulp. However, when the alkali charge and the H-factor were adjusted together, the pulp yield remained constant and the pulp properties improved in comparison to the reference pulp for both the 3 and 12% cases.

Keywords


Hemicelluloses; H-factor; Kraft pulping; Pre-extraction; Pulp properties

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