Method of producing chemical pulp
AssigneeAndritz Inc.
InventorsJanne Vehmaa, Kari Kovasin, Ismo Reilama
Life of this patent
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Abstract
A method of producing chemical pulp including at least the following steps: a) wood chips or other comminuted ligno-cellulosic fibrous material is treated with a polysulfide-containing cooking liquor in an impregnation stage at a temperature of 90-145° C., and b) slurry of fibrous material from step a) is heated into cooking temperature and cooked for producing pulp having a desired kappa number. After step a) mercaptide ions are added into the slurry of fibrous material and the fibrous material is treated at cooking temperature in step b).
Claims15
A method of producing chemical pulp, said method comprising at least the following steps:
- a) treating wood chips and/or other comminuted lignocellulosic fibrous material with a polysulfide-containing cooking liquor in an impregnation stage at a temperature in a range of 90° C. to 145° C., and
- b) heating and cooking in a digester vessel a slurry of the treated wood chips and/or other comminuted lignocellulosic fibrous material obtained from step a) to produce pulp;
- c) extracting cooking liquor from screens of the digester vessel;
- d) cooling the extracted cooking liquor;
- e) adding mercaptide ions to the extracted cooking liquor by adsorbing a mercaptan-containing gas into the extracted cooking liquor, and
- f) adding the extracted and cooled cooking liquor with the mercaptide ions to the slurry of the treated wood chips and/or other comminuted lignocellulosic fibrous material before and/or during step b).
A method of producing chemical pulp comprising:
- impregnating comminuted lignocellulosic fibrous material with a polysulfide-containing cooking liquor in an impregnation vessel at a temperature in a range of 90° C. to 145° C. to produce a slurry containing the comminuted lignocellulosic fibrous material and the polysulfide;
- conveying the slurry from the impregnation vessel to a digester vessel by a liquor circulation conduit extending from the impregnation vessel to the digester vessel;
- cooking the slurry in the digester vessel at a temperature above 145° C. to produce a chemical pulp;
- extracting a cooking liquor from a screen in the digester vessel;
- cooling the extracted cooking liquor;
- adding mercaptide into the extracted and cooled cooking liquor;
- and
- adding the extracted and cooled cooking liquor with the mercaptide into the slurry during the conveyance of the slurry and/or the cooking of the slurry.
Dependencies are inferred from the claim text.