Soda-anthraquinone pulping of sorghum stalks

Soda-AQ pulping of sorghum stalks increased the rate of delignification and the pulp yield and improved the strength properties compared to soda pulping, but the effect of AQ addition (0·13% on oven-dry raw material) was less pronounced than for tropical hardwoods. The wet-depithing of the stalks contributed considerably to the yield and strength properties, while the alkali consumption and rejects were decreased. Addition of guar gum (0·5% on oven-dry pulp), after beating, as wet-end/dry-strength agent, improved the drainage and strength properties. The soda-AQ pulping makes pulping of sorghum stalks much more attractive and feasible, once the other technical constraints are overcome by employing the recent techniques developed for other agricultural residues.