| 摘要 |
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 (at 11), passed to a treatment vessel (13, 113, 213), and then introduced into the top of a continuous digester (24, 124, 224). Black liquor is withdrawn from the digester (at 32, 132, 232) and heated (in 35, 135, 235) about 20-40 degrees C above cooking temperature (e. g. to about 170 degrees C), and then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 After the material is treated with the black liquor, it is withdrawn from the treatment vessel (at 17, 117, 217), and passed to the recovery or disposal stage. White liquor may be introduced into the treatment vessel (at 18, 118, 218) after black liquor withdrawal, after passing in heat exchange relationship (119, 219) with liquid recirculated from an impregnation vessel to a high pressure feeder (21, 121, 221). Alkali may be added to the black liquor withdrawn from the digester (at 34), prior to heating, and after heating it may be passed to a reaction vessel (36, 136, 236). <IMAGE> |
