Abstract: This invention relates to a new and improved way of continuously cooking fiber material, wherein temperatures and alkaline levels are controlled to be maintained within specific levels in different zones of the digesting process in order to optimize chemical consumption and heat-economy and at the same time achieve very good pulp properties.

Abstract: This invention relates to a new and improved way of continuously cooking fiber material in an over loaded digester, wherein temperatures and alkaline levels are controlled to be maintained within specific levels in different zones of the digesting process in order to optimize chemical consumption and heat economy and, at the same time, to achieve very good pulp properties.

Abstract: The present invention relates to a digester and a method for continuously cooking kraft pulp in a single-vessel system (1), preferably a single-vessel hydraulic digester, with chips (2) being fed in at a first end (3) of the digester (1), white liquor (4) being added at at least one position at or near the said first end (3), the chips being impregnated in a cocurrent impregnation zone (5), the chips being cooked in a cooking zone (6) downstream of the impregnation zone, hot black liquor (7) being extracted from at least one extraction strainer section (8), and cooked pulp being discharged (9) at the other end of the digester, and hot black liquor (7) being added (11), (12) to the said impregnation zone (5), and the extract (13) from the first strainer section (14), which is arranged downstream of the position of addition (11a) of the said hot black liquor (7), being largely removed from the digester.

Abstract: A method for cooking chips which are impregnated, in a vessel (3), with liquid in first and second concurrent impregnation zones (A, B), impregnation liquid being supplied, in a mixture with steamed chips, through a feeding system to the first impregnation zone, and liquid for recovery being extracted at a first point (41) at the end of the first impregnation zone, and further liquid being supplied to the second impregnation zone (B). According to the invention, liquid is extracted at a second point (43) at the start of the second impregnation zone (B) and is circulated in an impregnation circulation (44, 45) which empties out at the center of the vessel at a point between the first and second points (41, 43) for extraction of liquid so that a flow of liquid is established from the center of the vessel in a radial direction. The further liquid is supplied to the impregnation circulation for continued impregnation of the chips in the second impregnation zone.

Abstract: The present invention provides a method for continuously cooking kraft pulp in a digester having the steps of:feeding chips into an inlet of a digester;supplying black liquor to an impregnation zone of the digester in an amount such that the black liquor makes up greater than 40% by volume of the total volume of liquid present in the impregnation zone;extracting liquor from a screen girdle downstream of where the black liquor is added to the digester, in the direction the wood chips flow through the digester, in an amount greater than 50% by volume of the total volume of liquor present at the location of the screen girdle;maintaining a liquor:wood ratio in the impregnation zone of greater than 3:1; anddischarging cooked pulp from the digester.

Abstract: A penetration (51) through the bottom of a pool in the reactor containment below a reactor vessel is protected against the effects of a core meltdown, by the penetration (51) being surrounded by a pipe (60) having an inlet (61) located below the surface (31) of the water and above the highest level (41) which the bed (4) of granulate formed by the descending molten core material could be expected to reach. The pipe (60) has an outlet (62) at its lower end, located in the bed (4). The gap (64) between the penetration (51) and the pipe (60) is covered by a screen (7) which prevents granulate from entering. Granulate is also prevented from entering the outlet (62). The pool water flows in through the inlet (61), down through the gap (64), out through the outlet (62) and into the particle bed (4) where the water is vaporized and rises through the bed without obstructing the flow of water through the gap for cooling the penetration.