TOWARDS EFFLUENT FREE NONWOOD PULPING -RECYCLING OF BLEACHING FILTRATES

摘要

The article describes methods to completely recover chemicals and water in a nonwood pulping process based on formic acid. Because acidic cooking conditions prevent silicates from dissolving, the recovery of chemicals, dissolved solids and water from spent cooking liquor and washing filtrates is straightforward by evaporation and distillation.TCF-bleaching of the process makes it possible to recover and recycle the water from bleaching filtrates by evaporation, which is further facilitated by the low water demand for water (10～15 m~3/Adt_(pulp)) in bleaching. The present article reports experimental results regarding evaporation of bleaching filtrates. According to results, over 95% of the water can be recovered and demand for fresh water in bleaching can be reduced below one m~3/Adt pulp.