Removal of color and organic matter from kraft process bleach ef

Details Removal of color and organic matter from kraft process bleach ef Removal of color and organic matter from kraft process bleach ef

1975-03-07

1976-12-28

Bashore, S. Leon

Paper making and fiber liberation

Processes of chemical liberation, recovery or purification...

With regeneration, reclamation, reuse, recycling or...

210 42R, 210 53, C02C 502

Patent

active

040000338

ABSTRACT:
In a typical pulp mill bleaching process, a pulp slurry is subjected to one or more chlorination treatments, each being followed by a caustic extraction stage. To decrease the volume of effluents, water re-use is practiced with a portion of the first caustic extraction stage filtrate being reused for direct countercurrent washing to increase the concentration of the filtrate and the balance thereof being removed as a concentrated caustic extraction effluent. According to the novel feature, the caustic extraction effluent removed, having a pH of about 9 to 12, is combined with an acidic solution having a pH of less than about 1.5 to form a combined effluent having a volume of less than about 2500 gallons per air dried ton of bleached pulp and a pH below about 2.8, whereby a precipitate is formed which removes organic color bodies from the combined effluent. Part or all of the acidic solution is preferably a concentrated chlorination effluent obtained by recycle of the chlorination stage washer filtrate. The thus treated effluent has reduced color and this significantly reduces the chemical requirements for further color removal by other processes, e.g., lime treatment, alum coagulation, carbon absorption, etc.

REFERENCES:
patent: 2043458 (1936-06-01), Windecker et al.
patent: 3652407 (1972-03-01), Paleous
patent: 3729375 (1973-04-01), Chappelle
patent: 3736254 (1973-05-01), Croom

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