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1. (WO1986003236) PROCEDE D'EXTRACTION DE LIGNINE DES EFFLUENTS D'UNE INSTALLATION DE BLANCHIMENT
Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

We claim:

1. Method of removing lignin from bleach plant effluents, the method comprising an acidous phase during which a sludge containing cellulose fibres is acidified by acidous bleach plant effluent after which alkaline bleach water is added to the acidous effluent-sludge solution and the fraction containing the main portion of the fibres is separated, characterized in that a portion of the fraction containing fibres is recirculated to the acidous phase for reuse of the fibres.

2. Method according to claim 1 characterized in that the fraction containing fibres is separated by precipitation in a sedimentation basin.

3. Method according to claim 1 characterized in that the effluents are waste waters from displacement bleach plants or other concentrated waste waters.

4. Method according to claim 1 characterized in that the portion of the acidous effluent of the total effluent amount is approx. 2/3.

5. Method according to claim 1 characterized in that a cationic polymer is added to the solution in the alkaline phase.

6. Method according to claim 5 characterized in that the
3 amount of the cationic polymer added is 1 - 4 g/m effluent to be treated.

7. Method according to claim 1 characterized in that the amount of fibres supplied into the acidous phase is at
3
least 2 kg/m effluent to be treated.

8. Method according to claim 1 characterized in that the pH of the acidous effluent-sludge solution is 1,6 - 3,0.