Clean Bleaching Engineering Practice for Bagasse Pulp: Totally Chlorine-Free and Elemental Chlorine-Free Bleaching Realized with the Same Production Line

Zhi Li, Jun Li, Jun Xu, Li-huan Mo

Abstract


The experimental research, process design principles, and engineering practice of a bagasse pulp production line that could run both totally chlorine-free (OP)Q(PO) and elemental chlorine-free (OP)D(EOP) bleaching sequences are discussed in this paper. Under specified process conditions, the oxygen delignification rate was up to 50% and the brightness of unbleached pulp increased. The (OP)Q(PO) sequence bleached pulp had a brightness of 83.1% ISO and an intrinsic viscosity of 888 mL/g, and the (OP)D(EOP) sequence bleached pulp had a brightness of 85.7% ISO and an intrinsic viscosity of 905 mL/g. Pulp quality produced from both bleaching sequences was better than pulp bleached by the chlorination, alkaline extraction, and hypochlorite (CEH) sequence. The wastewater was discharged only from the Q or D stage, and the chemical oxygen demand (COD) of Q or D stage was about 650 mg/L or 1100 mg/L, respectively. It was easy to alternate between these two bleaching sequences, and the bleached pulp quality from these sequences was stable.

Keywords


Sugarcane bagasse; Clean bleaching; Totally chlorine-free; Elemental chlorine-free; Oxygen delignification; Peroxide bleaching; Chlorine dioxide bleaching

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