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US 6,203,662 B1Granted
Method for the continuous cooking of pulp in a digester system having a top separator
AssigneeKvaerner Pulping AB
InventorsVidar Snekkenes, Johan Engström, Krister Olsson, Mikael Lindström, Christofer Lindgren, Sören Gustavsson
Life of this patent
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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, achieving very good pulp properties.
Claims25
A method for continuously producing pulp, comprising the steps of:
- providing a finely divided fiber material, a transport liquid and an impregnation zone, the impregnation zone having an inlet portion and an outlet portion;
- providing a vessel to facilitate a cooking reaction, the vessel having at least one screen girdle section disposed therein, the vessel having a first concurrent cooking zone;
- providing a recovery unit for receiving spent liquor to be recovered;
- providing an amount of cooking liquor required for the cooking reaction;
- transporting the fiber material and the transport liquid to the impregnation zone;
- heating and impregnating the fiber material disposed in the impregnation zone;
- passing the heated and impregnated fiber material from the impregnation zone to a top separator of the vessel;
- separating the transport liquid from the fiber material in the top separator;
- withdrawing a substantial portion of the transport liquid in the top separator;
- supplying a first portion of the amount of cooking liquor to the top separator of the vessel;
- obtaining a first effective alkali concentration in the first concurrent cooking zone that is at least 35 grams per liter;
- passing the fiber material and the cooking liquor through the first concurrent cooking zone;
- withdrawing a hot black liquor from at least one of the screen girdle sections, the hot black liqueur having an effective alkali level of at least 13 grams per liter;
- transferring a substantial portion of the hot black liquor withdrawn from at least one of screen girdle sections to the inlet portion of the impregnation zone;
- separating and withdrawing a substantial portion of a spent impregnation liquor in the top separator;
- and
- conducting the spent impregnation liquor to the recovery unit.
14 more elements
A method for continuously producing pulp, comprising the steps of:
- providing a finely divided fiber material, a liquid and an impregnation zone, the impregnation zone maintaining a cooking pressure;
- providing a vessel having a top portion and a bottom portion and at least one strainer girdle disposed therein, the vessel being adapted to facilitate a cooking reaction, the vessel having a concurrent cooking zone at the top portion of the vessel, the concurrent cooking zone having a beginning and an end;
- providing a hot black liquor;
- providing an amount of cooking liquor required for the cooking reaction;
- mixing the finely divided fiber material with the liquid to form a slurry;
- while mixing the finely divided fiber material, transporting the slurry to the impregnation zone;
- while transporting the slurry, prevailing the cooking pressure in the impregnation zone;
- while prevailing the cooking pressure, transferring the hot black liquor to the impregnation zone;
- while transferring the hot black liquor, heating the fiber material disposed in the impregnation zone to a first temperature that is between about 140 degrees Celsius and 160 degrees Celsius and thoroughly impregnating the fiber material by exposing the fiber material to the hot black liquor;
- awhile heating the fiber material, passing the fiber material through the impregnation zone to a top separator at the toy portion of the vessel;
- separating and withdrawing a substantial portion of the liquid from the slurry in the top separator;
- supplying at least 60% of the cooking liquor to the top separator of the vessel and passing the cooking liquor together with the fiber material to the concurrent cooking zone of the vessel;
- obtaining a first level of effective alkaline that is at least 35 grams per liter at the beginning of the concurrent cooking zone;
- while obtaining the first level of effective alkaline, withdrawing spent liquor, that have passed through the concurrent cooking zone of the vessel, at the strainer girdle of the vessel, the spent liquor having an effective alkali level of at least 13 grams per liter;
- removing pulp from the bottom portion of the vessel;
- and
- maintaining a second temperature in the beginning of the concurrent cooking zone that is higher than the first temperature of the impregnation zone, the second temperature being above 160 degrees Celsius.
14 more elements
Dependencies are inferred from the claim text.