Environmentally Friendly Bleaching on Bamboo (Neosinocalamus) Kraft Pulp Cooked by Displacement Digester System

The bleaching of pulp prepared by a displacement digester system (DDS) for displacement cooking of bamboo (Neosinocalamus) was established by comparing the results from elemental chlorine-free (ECF) bleaching and totally chlorine-free (TCF) bleaching. This process produced the optimal performance of obtained pulp via O-D0-EOP-D1 bleaching, where the Kappa number of DDS pulp was 18 to 22, and the Kappa number of oxygen delignified pulp was 10 to 12. The brightness of the obtained pulp was over 86% ISO, the yield was up to 46%, and the viscosity was approximately 800 mL·g-1. In contrast, O-Q-P1-P2 bleaching was advantageous for pulp with kappa number less than 5 after oxygen delignification. The brightness of obtained pulp was up to 81% ISO, the yield was over 40%, and the viscosity was about 650 mL·g-1. In TCF bleaching, the water consumption was 20 m3·t-1, the chemical oxygen demand (COD) content was 30 kg·t-1, and the absorbable organic halogen (AOX) content was zero. The water consumption of ECF bleaching was 4 times that of TCF bleaching, while the COD content was 16 kg·t-1 and the AOX content was 2 kg·t-1.