Leaching Phenomena in Pulp - With and Without Oxygen Delignification, 2002 International Pulp Bleaching Conference Proceedings

Olli Joutsimo, Kati Vuorenvirta, Agneta Fuhrmann--To study the role of oxygen delignification versus alkaline leaching on lignin, the pulp and effluent samples were analyzed with respect to delignification rate, lignin structures, molar mass distribution, phenolic substances, and some fiber properties. Oxygen delignification experiments were performed .on line. at the mill using KCL’s specially designed DELFI laboratory reactor. This new reactor also allowed us to look more carefully at the delignification during one single oxygen stage, due to the sampling capability during the pressurized reaction stage. It was shown that the kappa number of the mill stage oxygen-delignified pulp is surprisingly close to the same pulp delignified in the laboratory reactor. According to the leaching experiments, the wash loss and easily leachable lignin were removed from the fibers during the first minutes. Little more lignin was removed when leaching was continued for several hours.