Wspólnotowy Serwis Informacyjny Badan i Rozwoju - CORDIS

Setting of an extraction production line

The removal of knotwood from the chips prior to pulping and bleaching in pulp mills can provide considerable benefits in terms of pulping and bleaching costs (chemical consumption), pulp and paper quality, as well as water and energy consumption and effluent qualities. The recovery of bark from sawmills and pulp mills can also be considered. As TMP and CTMP mills are mostly concerned by the knot wood removal and bark recovery, an estimation of the benefit during mechanical pulping process has been made, based on a process data and quality of the raw materials and end-products, from a pulp mill. The economy and reliability of the exploitation of wood wastes have also been studied.

Thanks to CTP and AAU own research know-how, it has been emphasised that one of the main benefits of removing knotwood from chips in TMP or CTMP mills are better pulp strength and brighter pulp with less dark specks. The separated knots is a rich raw material for extraction of lignans and other polyphenols., depending on the tree species. The knotwood separation process was tested in large laboratory scale on over-sized chips of Abies alba obtained from the pulp and paper mill. The knotwood was enriched to a high degree in the fractions, giving knotwood material with a lignan content of 5-9% (50-90 kg/ton). Theoretically and considering that the studied pulp mill burns 1250 m3/year (1 100 T/year) of Abies alba knots, 6 tons of lignans could be extracted per year.

These results are promising and production of lignans from Abies alba should be explored further. Bark wastes and especially from poplar, common oak, fir and pines are materials rich in flavanoids and other phenolic compounds. A large-scale study was carried out with industrial barks of populus deltoides supplied by a French pulp mill. It was shown that populus deltoides bark contained 1% (10 kg/ton) of two strong anti-oxidants. In addition, specific phenolic compounds responsible for anti-adhesive activities were also quantified in poplar barks.

Theoretically and considering that the studied pulp mill releases 7 000 tons/year of bark wastes, 70 tons of flavanoids could be extracted per year. Barks are therefore interesting wastes for their high contact in phenolic compounds, which could reasonably well exploited in the future, without sorting.

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