Cooking of dry high-lignin Eucalyptus camaldulensis chips followed by TCF bleaching with hydrogen peroxide

This paper describes laboratory experiments with Eucalyptus camaldulensis grown in South Asia. Pulping of E. camaldulensis is known to be challenging because of its high lignin content. Moreover, E. camaldulensis chips originating from arid and semi-arid regions of South Asia have often a very low moisture content, which further complicates their pulping. In this research, chips with 5.5% moisture content were screened and the accept fraction underwent a pressurized soaking treatment, which seemingly dissolved carbohydrates, extractives and lignin. The rewetted chips were cooked to a kappa number of 18, oxygen delignified and bleached with hydrogen peroxide. The yield was 45.4% based on unbleached pulp. Pulp viscosities after cooking, oxygen delignification and bleaching were 830, 700, and 600 mL/g, respectively. The high active alkali charge in cooking apparently resulted in low pulp viscosities. In addition to lignin, E. camaldulensis probably contained other polyphenolic compounds, which further consumed alkali. The bleached pulp brightness was 85.5% ISO.