Gradient Intensified Alkali Extraction of Kraft Pulp by Oxygen-Containing Bleaching Agents
The selectivity of delignification is disappointing in the conventional intensified alkali extraction by oxygen and H2O2. To improve the properties of the conventional intensified alkali extraction, the gradient intensified alkali extraction by oxygen-containing bleaching agents was presented, and effects of treatment conditions on properties of gradient intensified alkali extraction of kraft pulp by oxygen and/or H2O2 were investigated. In DEPD bleaching sequence, the optimal dosage of H2O2 in EP stage is 1.5% with higher brightness and lower loss in viscosity of bleached pulp. The addition time of H2O2 is better after 20 min of alkali extraction in DE/PD sequence to facilitate bleaching function of H2O2. In DP/ED sequence, the brightness is highest when alkali extraction carried through after 20 min of H2O2 bleaching. In EO stage, the optimal dosage of NaOH is 5.0% considering delignification and bleaching efficiency. As to alkali extraction intensified by oxygen and H2O2, the optimum dosage of H2O2 is 1.0%. Gadient intensified alkali extraction with oxygen and/or H2O2 was adopted for further bleaching and delignification, which can increase the brightness and selectivity of delignification by subtly adjusting the parameters.
Zhong Cao, Yinghe He, Lixian Sun and Xueqiang Cao
Z. Q. Pang et al., "Gradient Intensified Alkali Extraction of Kraft Pulp by Oxygen-Containing Bleaching Agents", Advanced Materials Research, Vols. 236-238, pp. 1293-1296, 2011