Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Including recovery of organic by-product
Patent
1997-05-02
2000-02-15
Alvo, Steven
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
Including recovery of organic by-product
162 301, 162 32, 162 37, 162 76, 159 473, 210712, 210737, 210928, D21C 1100, D21C 1104, D21C 1110
Patent
active
060248335
ABSTRACT:
Provided is a process for removing metals from a bleaching plant spent liquor and recovering a chelating agent which includes the steps of: heating a spent liquor containing a chelate comprising metals bound in a chelating agent to a temperature of at least about 140.degree. C. to break bonds in the chelate and release metals from the chelate; increasing the content of at least one of carbonate or sulphide in an alkaline material comprising at least one of green liquor or white liquor to form a carbonate or sulphide enhanced alkaline material; contacting the heated spent liquor with the alkaline material to form a solution containing precipitated metals, wherein the alkaline material is added in an amount sufficient to precipitate a majority of the released metals out of the solution; filtering the solution to separate the precipitated metals from the solution and form a filtrate containing recovered chelating agent; and supplying at least a portion of the recovered chelating agent to a chelating washing stage in a bleaching plant to bond with metals released from pulp and form a chelate. Also provided is a method of reducing encrustations.
REFERENCES:
patent: 5145557 (1992-09-01), Peter et al.
patent: 5509999 (1996-04-01), Lindberg
patent: 5540816 (1996-07-01), Andtbacka et al.
T. Grace, "Evaporator Scaling", Southern Pulp and Paper Manufacturer, vol. 40, No. 8, Aug. 1977.
R. Schleinkofer, "Overview of a Chlorine-Free Bleaching Process", Seminar Notes of the Technical Association of the Pulp and Paper Industry, Denver Hilton, Oct. 21,19981.
Lindberg, Strategies for Metal Removal Control in Closed Cycle Mills, 1994 International Pulp Bleaching Conference, Hyatt Regency Hotel, Vancouver, British Columbia, pp. 293-302.
Alvo Steven
Kvaerner Pulping AB
Melcher Jeffrey S.
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