Treatment of chips with high temperature black liquor to reduce

Details Treatment of chips with high temperature black liquor to reduce Treatment of chips with high temperature black liquor to reduce

1991-08-14

1993-05-25

Jones, W. Gary

Paper making and fiber liberation

Processes of chemical liberation, recovery or purification...

Continuous chemical treatment or continuous charging or...

162 37, 162 68, 162 39, D21C 326

Patent

active

052136620

ABSTRACT:
A method and apparatus provide for the production of low kappa number (e.g. below 20) kraft paper pulp, and a low viscosity black liquor which is easily transported to a recovery or disposal stage. Comminuted cellulosic fibrous material is steamed, passed to a treatment vessel, and then introduced into the top of a continuous digester. Black liquor is withdrawn from the digester and heated about 20-40 degrees C. above cooking temperature (e.g. about 170 degrees C.), and then introduced into contact with the material in the treatment vessel. After the material is treated with the black liquor, it is withdrawn from the treatment vessel, and passed to the recovery or disposal stage. White liquor may be introduced into the treatment vessel after black liquor withdrawal, after passing in heat exchange relationship with liquid recirculated from an impregnation vessel to a high pressure feeder. Alkali may be added to the black liquor withdrawn from the digester, prior to heating, and after heating it may be passed to a reaction vessel.

REFERENCES:
patent: 3578554 (1968-09-01), Richter
patent: 3849247 (1974-11-01), Richter
patent: 4929307 (1990-05-01), Kiiskila et al.
patent: 4953607 (1990-09-01), Erkki et al.
patent: 5080755 (1992-01-01), Backlund
Svensk Papperstidning Nr. 5, 1991, pp. 24-29; Hiljanen et al.
Ryham, "High Solids Evaporation Through Thermal Depolymerization of Black Liquor", 1989 Chemical Recovery, pp. 157-160.

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