Method and apparatus for treatment of black liquor

Details Method and apparatus for treatment of black liquor Method and apparatus for treatment of black liquor

1995-07-10

1998-02-10

Kim, Christopher

Concentrating evaporators

Processes

Film

159 5, 159 131, 159DIG22, 162 43, 162 301, B01D 122

Patent

active

057164967

ABSTRACT:
A method and an apparatus are provided for controlling crystallization (and thus preventing harmful fouling of heat transfer surfaces) during the treatment of black liquor. The black liquor is concentrated to a high dry solids content (at least about 70%, e.g. about 75-90%) in a falling film crystallizing apparatus (e.g. falling film evaporator). A part of the liquor flowing from the heat transfer surfaces and collected in a retention vessel (e.g. an interior volume of the evaporator) is recirculated to the heat exchange surfaces and a part of the liquor is discharged for further treatment (e.g. combustion in a recovery boiler). A part of the black liquor in the recirculation system is returned directly to the retention vessel in order to facilitate mixing and thus to bring about, in the retention vessel, crystallization of inorganic salts of the black liquor that is as complete as possible. Some of the discharged black liquor also may be returned, and a mixer and/or baffles disposed in the retention tank, to further enhance mixing.

REFERENCES:
patent: 5143579 (1992-09-01), Field et al.
patent: 5382321 (1995-01-01), Fagerlind eet al.
patent: 5472568 (1995-12-01), Mullen et al.
Puumassan valmistus II (Manufacture of Woodpulp II), 1983, p. 1181 (the passage underlined has been translated into English).
Swann, C.E., "American Papermaker", Oct. 1990, pp. 24-25.
Hedrick, R.H. et al, Tappi Journal, Dec., 1992, pp. 107-111.
Ahlstrom Evaporators brochure, (date unknown).
"Evaporators", A. Ahlstrom Osakeyhitio brochure.
Osborne, "A Falling-Film Crystallizing Concentrator . . . ", May 1992 Tappi Journal, pp. 107-111.
Hedrick et al, "Crystallizing Sodium Salts From Black Liquor", Dec. 1992 Tappi Journal, pp. 107-111.

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