Title
Soda pulping of rapeseed straw
Authors
FRANTISEK POTUCEK BIJAY GURUNG and KATERINA HAJKOVA

Received September 18, 2013
Published Volume 48 Issue 7-8 July-August
Keywords rapeseed straw, delignification, soda pulp, yield, anthraquinone

Abstract
The aim of this work was to conduct batch soda pulping of rapeseed straw (species Brassica napus L. convar. napus) without and with addition of anthraquinone as a catalyst in the cooking liquor. To characterize the chemical composition of rapeseed straw, cellulose, holocellulose, lignin, ash, and extractives were determined. The effect of anthraquinone addition upon the degree of delignification, total yield, and amounts of rejects was investigated. For selected samples of pulp, the fibre length, degree of polymerization, as well as strength properties of soda and soda-AQ pulps were measured as well. The results obtained showed that the content of lignin in rapeseed straw is lower than that in softwoods. The presence of anthraquinone in cooking liquor accelerates delignification, however, for a given H factor, lower kappa number and total yield were achieved, compared with cooking without anthraquinone. Also, anthraquinone in cooking liquor had a positive effect upon the decrease of rejects, mainly at a lower H-factor. The unbleached soda pulp comprising short fibres, below 1 mm, presented greater tensile strength in comparison with waste paper.