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Green liquor impregnation and Kraft pulping of South African Pinus Patula – "A practical approach to provide cost savings in a Kraft mill's pulping operation"

Jonas Johakimu , Tammy Bush and Lucian Lucia

The effect of green liquor pre-treatment (GLP) on Kraft pulping of Pinus Patula has been investigated. Wood chips were pre-treated with green liquor, and subsequently subjected to Kraft pulping to achieve a target Kappa number of 65-70.

The results here in have revealed that GLP has the potential to substantially improve the delignification rate during Kraft pulping. Compared to regular Kraft pulping; the H-Factor can be reduced by almost 52% when GLP is applied. In addition, if the H-Factor is maintained at the same level as was used during regular Kraft pulping, the liquor charge can be reduced by 33%. GLP followed by Kraft pulping produced pulp samples with superior strength properties to those produced by regular Kraft pulping.

The potential benefits of GLP technology to the Kraft pulping industry are; providing cost savings, increased digester productivity, and mitigation of some of environmental impacts. Depending on the process economics of the pulping process of a Kraft pulp mill, GLP can be used to shortening of the digester pulping time or down sizing the limekiln requirements.

Green liquor, Kraft pulping, H-Factor, pulping liquor, Kappa number, strength properties

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