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US 4,295,925 AGranted
Treating pulp with oxygen
AssigneeWeyerhaeuser Company
InventorsJozef M. Bentvelzen, Michael D. Meredith, Henry Bepple, Louis O. Torregrossa, Howard R. Battan, Dennis H. Justice
Life of this patent
Estimating the term…
Abstract
Washed wood pulp from a continuous digester is treated with oxygen in the blow line from the digester. Most of the treatment occurs within the mixer. The mixer has a mixing zone with a swept area of 10,000 to 1,000,000 square meters per metric ton of oven-dry pulp. A preferred range is 25,000 to 150,000 square meters per ton of oven-dry pulp and an optimum range is around 65,400 square meters per metric ton of oven-dry pulp. Following mixing, the pulp may be taken to a subsequent process, a diffusion washer, or to a storage tank.
Claims40
A wood pulp process comprising
- continuously digesting wood chips with chemicals under heat and pressure to form delignification products and delignified wood chips,
- removing at least a part of said delignification products,
- forming wood pulp from said delignified wood chips by partially releasing the pressure from said wood chips,
- transporting a slurry containing said wood pulp and remaining delignification products under pressure to a storage tank, and
- storing said slurry in said tank,
- prior to said storage, adjusting the pH of said slurry to a pH in the range of 8 to 14,
- between said pH adjustment and said storage, adding oxygen to said slurry,
- between said pH adjustment and said storage, mixing said oxygen with said slurry in a mixing zone in which a plurality of rotating members pass through said slurry in a direction transverse the direction of travel of said slurry,
- said members having a major axis extending in the direction of rotation,
- said members providing a swept area through said slurry of 10,000 to 1,000,000 square meters per metric ton of oven dry pulp,
- said members having leading and trailing edges, said leading edge having a radius of curvature in the range of 0.5 to 15 mm.
8 more elements
A wood pulp process comprising
- continuously digesting wood chips with chemicals under heat and pressure to form delignification products and delignified wood chips,
- removing at least a part of said delignification products,
- forming wood pulp from said delignified wood chips by partially releasing the pressure from said wood chips,
- transporting a slurry containing said wood pulp and remaining delignification products under pressure to a diffusion washer,
- washing said pulp in said diffusion washer,
- prior to said diffusion washing, adjusting the pH of said slurry to a pH in the range of 8 to 14,
- between said pH adjustment and said diffusion washing, adding oxygen to said slurry,
- between said pH adjustment and said diffusion washing, mixing said oxygen with said slurry in a mixing zone in which a plurality of rotating members pass through said slurry in a direction transverse the direction of travel of said slurry,
- said members having a major axis extending in the direction of rotation,
- said members providing a swept area through said slurry of 10,000 to 1,000,000 square meters per metric ton of oven dry pulp,
- said members having leading and trailing edges, said leading edge having a radius of curvature in the range of 0.5 to 15 mm.
8 more elements
A pulping apparatus comprising
- a continuous digester for continuously digesting wood chips to form delignification products and delignified wood chips, and
- a washer associated with said digester for removing at least a part of said delignification products,
- said digester having a pressure relief valve for forming wood pulp from said delignified wood chips by partially releasing the pressure from said wood chips,
- a pipe for transporting a slurry containing said wood pulp and remaining delignification products under pressure from said digester to a storage tank, and
- said storage tank,
- means, prior to said storage tank, for adding a pH adjustment chemical to said slurry,
- means, between said pH adjustment chemical addition means and said storage tank, for adding oxygen to said slurry, and
- means, prior to said storage tank, for mixing said oxygen with said slurry, said mixing means having
- a mixing zone,
- a plurality of rotors in said mixing zone,
- said rotors having leading and trailing edges, said leading edge having a radius of curvature in the range of 0.5 to 15 mm.
- said rotors having a major axis extending in the direction of rotation,
- said rotors being rotatable through said slurry in a direction transverse to the direction of travel of said slurry,
- means for rotating said rotors, and
- said rotors providing a swept area of from 10,000 to 1,000,000 square meters per metric ton of oven dry pulp.
12 more elements
A pulping apparatus comprising
- a continuous digester for continuously digesting wood chips to form delignification products and delignified wood chips, and
- a washer associated with said digester for removing at least a part of said delignification products,
- said digester having a pressure relief valve for forming wood pulp from said delignified wood chips by partially releasing the pressure from said wood chips,
- a pipe for transporting a slurry containing said wood pulp and remaining delignification products under pressure from said digester to a diffusion washer, and
- said diffusion washer,
- means, prior to said diffusion washer, for adding a pH adjustment chemical to said slurry,
- means, between said pH adjustment chemical addition means and said diffusion washer means, for adding oxygen to said slurry, and
- means, prior to said diffusion washer, for mixing said oxygen with said slurry, said mixing means having
- a mixing zone,
- a plurality of rotors in said mixing zone,
- said rotors having leading and trailing edges, said leading edge having a radius of curvature in the range of 0.5 to 15 mm,
- said rotors having a major axis extending in the direction of rotation,
- said rotors being rotatable through said slurry in a direction transverse to the direction of travel of said slurry,
- means for rotating said rotors, and
- said rotors providing a swept area of from 10,000 to 1,000,000 square meters per metric ton of oven dry pulp.
12 more elements
Dependencies are inferred from the claim text.