Method of producing dissolving pulp
AssigneeAndritz Inc.
InventorsAuvo KETTUNEN, Sampsa LAAKSO, Tiina HAATAINEN, Markus PAANANEN
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Abstract
A process for producing dissolving pulp from comminuted wood-based fibrous material. The process includes the following consecutive stages: cooking comminuted fibrous material with alkaline cooking liquor in a kraft cooking process to produce pulp; treating the cooked pulp in caustic extraction at a temperature of 70-110° C. and in an effective alkali concentration of 60-120 g/l for at least 5 minutes, and washing and oxygen delignifying the caustic extracted pulp.
Claims16
A method for dissolving pulp from comminuted hardwood-based fibrous material, the method comprises:
- treating comminuted fibrous material under acidic conditions in which a P factor is in a range of 5 to 250;
- cooking the treated comminuted fibrous material with an alkaline cooking liquor at a temperature in a range of 120° C. to 175° C. in a kraft cooking process to produce pulp;
- treating the pulp in caustic extraction at a temperature is in a range of 70° C. to 110° C. for at least 5 minutes to produce caustic extracted pulp, wherein the caustic extraction includes a liquid phase in which the pulp is in suspension and an alkali concentration of the liquid phase is in a range of 60g/l to −120 g/l,
- washing the caustic extracted pulp, and
- oxygen delignifying the caustic extracted pulp after the washing.
A method comprising:
- a) treating comminuted fibrous material under acidic conditions in which a P factor is in a range of 5 to 250;
- b) cooking the treated comminuted fibrous material with alkaline cooking liquor at a cooking temperature in a range of 120° C. to 175° C. to produce pulp,
- c) feeding alkaline wash liquor to the pulp to cool and/or wash the pulp;
- d) feeding white liquor to the pulp to form a mixture of the white liquor and the pulp, after step c;
- e) treating the mixture of the white liquor and the pulp at a temperature of 70° C. to 110° C. for 5 to 120 minutes;
- f) removing a first filtrate from the mixture and delivering the first filtrate as a pulp wash liquor flowing counter-currently to a pulp flow;
- and
- g) separating a second filtrate from the mixture, and using the second filtrate as at least a portion of the alkaline cooking liquor;
- and
- h) delivering the pulp to further processing after step g).
A method comprising:
- treating comminuted hardwood based fibrous material under acidic conditions in which a P factor is in a range of 5 to 250;
- producing pulp by a cooking the treated comminuted fibrous material with an alkaline cooking liquor at a temperature to a range of 120° C. to 175° C. in a kraft cooking process;
- adding the pulp to a caustic extraction vessel in which the pulp is suspended in a liquid, controlling a temperature of the liquid with the suspended pulp is in a range of 70° C. to 110° C. for at least 5 minutes to produce caustic pulp, wherein an alkali concentration of the liquid with the suspended pulp is in a range of 60g/l to 120 g/l,
- washing the caustic pulp after discharge from the caustic extraction vessel, and
- oxygen delignifying the washed caustic pulp.
Dependencies are inferred from the claim text.