Abstract
The aim of this research project was to investigate the scientific and technical feasibility of making unbleached pulp by cooking bagasse with anthraquinone (AQ) in conjunction with KOH or KOH and NH4OH. The NH4OH could be used as a pretreatment or in the cooking stage. The design called for recovery of some NH4OH by distillation but no recovery of KOH. Bagasse was delignified much more rapidly by KAQ (KOH + AQ) or SAQ (NaOH +AQ) cooking as compared to most hardwoods. When 15 mesh, solvent extracted bagasse and sugar maple were treated to SAQ delignification to a H factor of 441, bagasse pulp was obtained with kappa number 10.1 as compared to 44.5 for sugar maple. The non-syringyl fraction of bagasse lignin was found to contain 67% more uncondensed β-O-4' dimeric units compared to sugar maple. It was observed that if 23% KOH on depithed bagasse was used at 12:1 liquor to biomass ratio, a pulp with unbleached kappa number of 12.6 and excellent bleachability was obtained. Pretreatments were investigated and an ANKAQ sequence merits further investigation (A=acid treatment to end pH 4.04.5; N= NH4OH). The preliminary results obtained indicated that the A stage could be used to extract xylan (MW 10,000), Ca and Mg. The xylan could be converted to bio-products in the future while Ca and Mg removal should decrease the scaling problems associated with alkaline silica. Strength and drainage data were minimally affected when bagasse KAQ pulp was mixed into eucalyptus kraft pulp at 10 wt% but significantly affected at 20% substitution.