Monday, May 5, 2008
11-08

Production of value added chemicals from xylan extraction in a Kraft pulp mill and the effect on pulp quality

Jonas Helmerius1, Jonas Vinblad von Walter2, Ulrika Rova1, Kris K. A. Berglund1, and David Hodge1. (1) Biochemical and Chemical Process Engineering, Luleå University of Technology, Luleå, 971 87, Sweden, (2) Techcenter, Smurfit Kappa Kraftliner AB, Piteå, 941 86, Sweden

In the Kraft process hemicelluloses are lost in the cooking procedure to the black liquor stream, which is subsequently burnt in the recovery boiler to recover cooking chemicals and to produce steam and energy. Hemicelluloses have a low heating value compared to lignin and therefore recovery of hemicelluloses at an earlier stage of the Kraft process followed by biochemical conversion into high value-added products might offer a much better economic opportunity. In collaboration with the research and development department of Smurfit Kappa Kraftliner AB, Piteå, Sweden, alkali and water extractions of birch wood were performed under conditions compatible with the Kraft process, at different times, temperatures and alkali charges. The extraction conditions were set in a range suitable with the current pulp process at Smurfit Kappa Kraftliner. The requirements for process configurations, based on either hot water or alkali extraction were also explored. The xylan yields from different extraction trials were measured and the chips from those extraction trials were cooked, refined and turned into sheets of paper. The effects on paper quality were compared with a reference pulp made from the same wooden chips. Recovered xylans from water extracted birch wood chips were subjected to secondary hydrolysis, enzymatic or sulphuric acid. Detoxification of the hydrolysate with active carbon and regulation of pH were performed before fermentation. Fermentation of the xylose hydrolysate to succinic acid was demonstrated by the use of the succinic acid producer Escherichia coli AFP184.


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