Steam Stripping of Contaminated Condensates from the Black Liquor Evaporation Plants, 1996 Minimum Effluent Mills Symposium Proceedings

Göran Danielsson

MoDo-Chemetics AB

Mattias Håkansson

Kvaerner Pulping Technologies AB

In-plant treatment of contaminated condensates from the digester and evaporation areas is an important method in order to reduce the discharge of COD compounds and to make it feasible to reuse condensates in a kraft mill. Kvaerner Pulping has in collaboration with MoDo-Chemetics AB made a study on a full scale steam stripper to investigate the possibility of treating the semi foul condensates from the evaporation plant. Condensates with COD-levels between 300 and 500 mg/l were treated and varying steam/condensate ratios were used to optimise the steam load to the stripper. The removal of methanol, TRS and COD was measured during the trials. Methanol and TRS showed high removal at steam/condensate ratios of about 0.15. Higher steam/condensate ratio were needed for high COD separation. Approx. 30% of the COD remained after treatment A second part of the study was to examine contaminants in condensate from a pilot black liquor concentrator. The results showed that the amount of methanol, ethanol and TRS compounds increased at higher temperature or at higher liquor dry solids content.