Method of oxygen delignifying wood pulp with between stage washing

摘要

The viscosity of paper pulp is maximized, while chlorine bleaching is minimized or eliminated, by subjecting the pulp suspension to multiple consecutive oxygen bleaching stages, with a countercurrent wash between O2 stages. A chelating agent-such as EDTA-may be added to the countercurrent wash liquid, and/or another chelating agent-such as DTPA-may be used to pretreat the pulp.