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US 2006/0213629 A1Published application
Impregnation of chips with an acid liquid prior to a sulphate pulping process
AssigneeMetso Fiber Karlstad AB
InventorsVidar Snekkenes, Krister Olsson
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Abstract
The method is for pre-treatment of chips that are fed to a sulphate cooking process. Through acidification of the chips in an acidic treatment fluid with a subsequent draining of free treatment fluid before subsequent steaming or wet-steaming, a high concentration of free hydrogen ions is established within the chip pieces. When the chips are subsequently formed into slurry with preferably a sulphide-rich alkali cooking fluid, H2S is formed locally in the chip pieces which gives a yield-increasing effect in the subsequent cooking step of 1-3%.
Claims12
A method for a pre-treatment of chips, comprising:
- exposing the chips to an acidic treatment device by adding an acidic treatment fluid to establish an acidic slurry having a fluid fraction exceeding 50%;
- draining the chips from the acidic slurry so that the drained chips obtain a remaining free acidic fluid fraction that does not exceed 10%;
- adding additional acidic treatment fluid to the acidic treatment device only in a replacement amount that corresponds to an amount of acidic fluid that is retained in the drained chips;
- heating the drained chips by steam to a first temperature;
- and
- heating the drained chins to a second temperature not exceeding 140° C. while adding an alkali impregnation liquid, the second temperature being higher than the first temperature.
3 more elements
Dependencies are inferred from the claim text.