Patent ID: 6179958
Filing Date: 2001-01-30
Classification: D21C

Abstract:
A method for continuous cooking of cellulose-containing fiber material, comprising:providing a bottom circulation having a cooking liquid conduit connected thereto for carrying a cooking liquid therein;steaming a fiber material;impregnating the fiber material with an impregnating liquid in an impregnation vessel, the impregnation vessel containing a fresh cooking liquid and a first spent liquor extracting the first spent liquor from the impregnation vessel;looking the impregnated fiber material in a digester at a predetermined cooking temperature in the digester, the digester having a concurrent cooking zone and a counter-current cooking zone;extracting a first portion of a spent liquor from the digester at a position that is disposed between the concurrent cooking zone and the counter-current cooking zone;extracting a second portion from the first portion of the spent liquor and transferring a remaining third portion of the spent liquor to the impregnation vessel;passing the second portion of the spent liquor through a first heat exchanger;supplying the cooking liquid from the cooking liquid conduit to the bottom circulation;circulating the cooking liquid in the bottom circulation in operative engagement with the digester and the first heat exchanger;transferring heat from the second portion of the spent liquor to the cooking liquid in the bottom circulation at the first heat exchanger and increasing a temperature of the cooking liquid in the bottom circulation to a cooking temperature; andsupplying a wash liquid to a bottom portion of the digester the bottom portion being separate from the bottom circulation.