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TheKappa number is an indication of the residuallignin content orbleachability ofwood pulp by a standardized analysis method.
The Kappa number is determined by ISO 302:2004.[1] ISO 302 is applicable to all kinds ofchemical and semi-chemical pulps and gives a Kappa number in the range of 1–100. The Kappa number is a measurement of standardpotassium permanganatesolution that the pulp will consume. The measurement is inflated by the presence ofhexenuronic acids in the pulp. These compounds are formed during the chemical pulping process, from thehemicelluloses.
The Kappa number can be monitored by online Kappa analysers in apulp mill, but these have to be calibrated with the ISO 302:2004 method.
The Kappa number estimates the amount of chemicals required during bleaching ofwood pulp to obtain a pulp with a given degree of whiteness. Since the amount ofbleach needed is related to the lignin content of the pulp, the Kappa number can be used to monitor the effectiveness of the lignin-extraction phase of thepulping process. It is approximately proportional to the residual lignin content of the pulp.
Where:
The Kappa number forbleachable pulps are in the range of 25–30,sack paper pulps in the range 45-55 and pulps forcorrugated fiberboard are in the range 60-110.
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