Importance

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Abstract

Volatile compounds, such as methanol, are separated from secondary condensates formed in multi-effect evaporation of waste liquor, such as black liquor, from cellulose pulp processes. The condensable secondary vapor is condensed into first and second condensate flows, the first of which, smaller in volume, contains the majority of the volatile compounds condensed in the evaporating effect. The first condensate flows from one or more first evaporation effects, and/or condensers of the evaporation plant, are directed for cleaning into a first steam stripping column. At least some of the second flows are directed to a second steam stripping column to be recovered as very clean condensate, cleaner than the condensate flow from the first stripping column and typically have a methanol concentration of less than 25 ppm, preferably about 10 ppm or less.

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First Claim