Comparison of enmonoethanolamineMEA / enanthraquinoneAQ , soda and soda/ enanthraquinoneAQ pulping of wheat and rye straw

MEA (monoethanolamine)/AQ pulping of wheat and rye straw and bleaching of the produced pulps were investigated. The delignification behaviour of wheat and rye straw using varying MEA/water and liquor/straw ratios was studied. Furthermore, the impacts of mono-, di-, tri-ethanolamine/water mixtures and addition of KOH to the cooking liquor were monitored. The best results were achieved with a MEA/water ratio of 50/50 at a liquor/straw ratio between 3:1 and 4:1. The use of the mixture of mono-, di-, tri-ethanolamine instead of MEA only was not effective for straw pulping. The effect of adding KOH to the MEA pulping liquor was negligible. The results of MEA pulping of both straw species were compared with results for production and bleaching of soda and soda/AQ reference pulps. At similar degree of delignification, the MEA pulps showed 10% higher yield (based on straw), which demonstrates the unusually high selectivity of MEA in straw pulping. The MEA straw pulps showed fairly low brightness and were more difficult to bleach than the corresponding soda pulps. Nevertheless, it is possible to bleach MEA pulps to more than 80% ISO brightness, applying an ECF bleaching sequences (O-Q-OP-DQ-P). With regard to bleachability, yield and strength properties the rye straw pulp sample performed much better than wheat straw pulp sample.