Organic matter balance in ECF kraft mill fiberline.

Organic matter balances of an ECF kraft mill fiberline were studied in three different operational conditions of the oxygen delignification stage by implementing mill measurements, collecting routine mill data and combining them in a modified PROCELL steady state model. Dissolved volatile solids was the basic measurement for organic matter in liquid streams. Normal operation of the O2D0E(O)D1E(OP)D2 fiberline was described successfully. It was also possible to describe exceptional operating situations in the oxygen delignification stage and their effects on other parts of the production process reasonably well in order to focus studies on aspects requiring further attention. The existence of organic matter lost through complete degradation and volatile organic compounds in unit processes as well as its sensitivity to yield and operational situations is shown. The different perspectives of pulp production and wastewater treatment can be brought closer to each other using the approach in this study. The variation in the fractions discharged to wastewater treatment, although a relatively small share of the overall organic matter balance, will continue to become more important also for pulp production when effluent streams are increasingly turned back to the production line through further closure. Studies like the one presented here, can contribute to the evaluation of this development.