Patent ID: 6054019
Filing Date: 2000-04-25
Classification: D21C

Abstract:
A method for continuous cooking of cellulose containing fiber material, the method comprising the steps of:providing an Impregnation vessel having a first and a second concurrent impregnation zone, the second concurrent impregnation zone being subsequent to the first concurrent impregnation zone, the first impregnation zone having a HS.sup.- /OH.sup.- ratio that is greater than a HS.sup.- /OH.sup.- ratio in the second concurrent impregnation zone;providing a first impregnation liquid in a mixture with a steamed fiber material;feeding the mixture to the first concurrent impregnation zone;impregnating the fiber material with the first impregnation liquid in the first concurrent impregnation zone;extracting a recovery liquid at a first point that is at an end of the first concurrent impregnation zone;providing a second impregnation liquid to the second concurrent impregnation zone, the second impregnation liquid containing at least one liquid selected from the group consisting of black liquor, green liquor and washing liquid;impregnating the fiber material with the second impregnation liquid in the second concurrent impregnation zone;extracting a circulation liquid at a second point that is at a beginning of the second concurrent impregnation zone;circulating the circulation liquid in an impregnation circulation;feeding a white liquor to the impregnation circulation;discharging the circulation liquid at a center of the impregnation vessel at a third point that is disposed between the first point and the second point;establishing a free flow of the circulation liquid at the center of the impregnation vessel in a direction that is mainly radial; andcontinuously cooking the fiber material to form pulp fiber.