US3492199A - Bleaching fluffed mechanical wood pulp with hydrogen peroxide - Google Patents

Bleaching fluffed mechanical wood pulp with hydrogen peroxide Download PDF

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Publication number
US3492199A
US3492199A US584078A US3492199DA US3492199A US 3492199 A US3492199 A US 3492199A US 584078 A US584078 A US 584078A US 3492199D A US3492199D A US 3492199DA US 3492199 A US3492199 A US 3492199A
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United States
Prior art keywords
pulp
bleaching
hydrogen peroxide
brightness
drying
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Expired - Lifetime
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US584078A
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English (en)
Inventor
Robert R Kindron
Frederick J Rosebush
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FMC Corp
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FMC Corp
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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/1026—Other features in bleaching processes

Definitions

  • a method for simultaneously drying and bleaching mechanical wood pulp high in non-cellulose ingredients comprises introducing the pulp at a solids concentration of 20 to 50% by weight, fluffing the pulp to provide separate to loosely agglomerated pulp fibers, introducing an aqueous alkaline hydrogen peroxide solution into the fiuffed pulp, passing the treated fluffed pulp together with a gas at a temperature of 500 to 1000 F. and substantially free of reducing agents into a drying and bleaching zone and contacting the treated fluffed pulp in the drying and bleaching zone with the heated gas stream for 2 seconds to 10 minutes to bleach the pulp and dry it to a solids content of 65 to 95% by weight.
  • This invention relates to the processing of mechanical wood pulps, and particularly to the simultaneous and rapid drying and bleaching of such pulps.
  • This value is determined by drying the pulp to a constant weight in a circulating air oven at 105 C.
  • a very effective method involves mechanically pressing water out to provide a pulp solids of 20 to 50%, flufling the mechanically dried pulp to a subdivided or loose condition, and drying the pulp in a gas heated dryer to 800 to 900 F. In several seconds to 5 minutes to a solids content of to This method has a very serious drawback. Tne noncellulosic materials in the pulp cause it to darken at the drying temperatures employed, and ultimately costly bleaching processes must be carried out on the pulp to cause the pulp to have a satisfactory brightness for many end uses.
  • the heating gas drops in temperature to about to 250 F.
  • the pulps treated by our process are the socalled mechanical pulps. These pulps typically are prepared by the groundwood process in which logs are ground on a grinding stone to provide the pulp, or by the refiner process in which wood chips are shredded into pulp by attrition mills or disc refiners. These pulps generally contain about 30 to 50% of lignin and other non-cellulosic materials. Chemical pulps, on the other hand, generally contain less than about 5 to on the order of 12% of such non-cellulosic materials.
  • Mechanical pulps are normally prepared from the coniferous and deciduous woods, for example spruce, fir, hemlock, pine, poplar, cottonwood and aspen, and these various pulps all are dried and bleached effectively by our process.
  • the mechanical pulps are in the form of slurries in water.
  • Such slurries have solids concentrations of about 1 to 30%.
  • they can be dewatered to a solids content of 6 to 30% and bleached with active oxygen bleaching agents, and in some cases with chlorine-based bleaching agents, and the like, and then used.
  • the mechanical dewatering step is readily carried out in any equipment which mechanically expresses water from the pulp slurry.
  • Typical kinds of apparatus for use in dewatering are filters, vacuum thickeners, pulp presses, Wet lap machines and the like.
  • the drying operation may be carried out efiiciently the dewatered pulp is fiuffed, or broken up into essentially free or loosely agglomerated pulp crumbs prior to being contacted with the heated gas.
  • the flufiing operation is conveniently carried out in a disc mill, a hammer mill, rod mill or the like, in which the nodules or tightly agglomerated bundles of fibers which are formed in the mechanical dewatering step are subdivided.
  • the fiufr'ed pulp resulting from this operation can be brought into intimate contact with the drying gas.
  • the drying step is carried out by contacting the pulp with a heated gas, generally oil or gas combustion products, or hot air introduced at a temperature of 500 to 1000 F.
  • a heated gas generally oil or gas combustion products, or hot air introduced at a temperature of 500 to 1000 F.
  • Such treatment drys the pulp to 65 to 95% solids in as little as about 2 seconds to 10 minutes. Obviously at higher temperatures in our range the drying takes place at shorter times, and vice versa.
  • the gas and pulp are contacted in any zone which provides for passage of the gas over and through the fluffed pulp and for removal of the gas and the water vapor resulting from drying.
  • the heating gas be substantially free of reducing agents such as the 80;, formed when some fuels are burned.
  • reducing agents such as the 80;, formed when some fuels are burned.
  • the high sulfur contents of such oils as Bunker C petroleum-derived fuel oil causes the formation of sufiicient sulfur dioxide to destroy the hydrogen peroxide used in our process.
  • our bleaching agent into the mechanically dewatered pulp during the flut'fing operation.
  • it may be introduced before or after fiufiing provided it is present on the pulp during the heating stage. It can be introduced in liquid form or as a mist or vapor, at any desired concentration which will provide the amount of bleaching agent necessary for bleaching.
  • Our bleaching agent is hydrogen peroxide, which is assisted in its bleaching action by an alkali, preferably a polyphosphate such as sodium or potassium tripolyphosphate, a sodium or potassium pyrophosphate, metaphosphate or the like.
  • alkalies for example trisodium or tripotassium phosphate or other alkali orthophosphate, sodium silicate, sodium hydroxide or sodium carbonate, or combinations of alkalies, may be used.
  • sodium hydroxide or sodium carbonate alone is not recommended, because at the high temperatures used in our process these strong alkalies tend to speckle the pulp, that is, to cause localized or spotty darkening of it.
  • the hydrogen peroxide may be introduced as such, or as sodium peroxide, sodium perborate or other source of active oxygen which forms an aqueous alkaline hydrogen peroxide solution. It is used in an amount of 0.1 to 4%, and preferably of 0.5 to 2%, based on the dry weight of the pulp. That is, 0.1 to 4 grams, and preferably 0.5 to 2 grams, per 100 grams of dry pulp, expressed, as hydrogen peroxide. Use of more is not harmful, but is not justified economically.
  • the alkali is used in an amount of about 0.5 to 5% based on dry pulp weight.
  • sodium peroxide When sodium peroxide is used, it supplies alkalinity which should be taken into account when determining the desired alkalinity of the system.
  • Additional bleaching aids may also be used in our bleaching system.
  • sequestering agents such as ethylene diamine tetraacetic acid, diethylene triamine pentaacetic acid or their salts, and other additives commonly used in bleaching may be employed.
  • Example 1 A stone groundwood pulp comprising 23% of spruce, 60% of northern fir and 17% of hemlock having a brightness of 63.0%, was obtained as a slurry in Water. This pulp was dewatered and mechanically thickened to a solids concentration of 40% and fluffed or disintegrated into discrete particles resembling moist breadcrumbs, in a disc refiner. During the treatment in the refiner an aqueous solution of 1.0% of hydrogen peroxide and 1.0% of sodium tripolyphosphate was introduced into the pulp in an amount to provide 1% by weight of hydrogen peroxide and 1% by weight of sodium tripolyphosphate on the dry weight of the pulp.
  • the resulting treated pulp crumbs were then passed into a hot air stream, entering the air stream at the inlet side of the drier where the air was at a temperature of 800 F.
  • the pulp was carried in the hot air stream until it was dried to a solids concentration of This required a residence time of 4 minutes.
  • the pulp was then separated from the gas stream in a cyclone separator, the air as it left the drier being at a temperature of 200 F.
  • the dried pulp was collected.
  • the pulp brightness following this treatment was 65.4%, whereas a sample which was treated in the same way as this except that our alkaline hydrogen peroxide bleaching agent was not used, following drying had a brightness of only 60.5%, or 2.5% lower than the brightness of the initial pulp.
  • Example 16 (comparative) (a) A stone groundwood pulp comprising 60% spruce and balsam fir, having an unbleached brightness of 58%, was obtained as a slurry. The slurry was dewatered and mechanically thickened to a solids concentration of 50%, and flufied in a disc refiner. During fluffing an aqueous solution containing 1.0% of hydrogen peroxide, 2.5% of sodium silicate (41 B.), 1.0% of sodium tripolyphosphate and 1.0% of sodium hydroxide was fed into the pulp to provide 0.3% of hydrogen peroxide, 0.75% of the sodium silicate, 0.3% of sodium tripoly phosphate and 0.3% of sodium hydroxide based on dry pulp weight.
  • the pulp was dried by this process to a solids content of 85%. Its brightness was lowered by the treatment to 57.5%.
  • Example 16(b) The process of this Example 16(a) was repeated with the exception that the oil burned to produce the hot gas was a Grade 1 fuel oil having a sulfur content of less than 0.5%.
  • the pulp dried with this essentially sulfur-free hot gas had a brightness of 63
  • Example 17 A refiner groundwood pulp comprising cottonwood and pine and having a brightness of 63% was obtained as a slurry in water. It was dewatered and mechanically thickened to a solids concentration of and fiuffed in a disc refiner.
  • a bleach liquor comprising an aqueous solution of 3.0% of hydrogen peroxide and 6.0% of sodium tripolyphosphate was introduced into the pulp at the entry point of the disc refiner in an amount to provide 0.85% of hydrogen peroxide and 1.75% of sodium tripolyphosphate in the pulp.
  • a method of simultaneously rapidly drying and bleaching mechanical wood pulp having a high content of lignin and other non-cellulosic matter comprising, dewatering said pulp to a solids concentration of 20 to 50% by weight and a water content of to 50% by weight, flufiing said pulpto provide essentially separate to loosely agglomerated pulp fibers, introducing an aqueous alkaline hydrogen peroxide solution containing 0.1 to 4% of hydrogen peroxide into said fluffed pulp, passing said treated fluffed pulp together with a heated gas stream which is at a temperature of 500 to 1000 F.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)
US584078A 1966-10-04 1966-10-04 Bleaching fluffed mechanical wood pulp with hydrogen peroxide Expired - Lifetime US3492199A (en)

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US58407866A 1966-10-04 1966-10-04

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US (1) US3492199A (es)
CH (1) CH483518A (es)
DE (1) DE1621692A1 (es)
ES (1) ES345665A1 (es)
FR (1) FR1542837A (es)
NO (1) NO120217B (es)
SE (1) SE341519B (es)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3627630A (en) * 1969-12-04 1971-12-14 Beloit Corp Method of flash drying pulp
US3630828A (en) * 1968-05-13 1971-12-28 Pulp Paper Res Inst Bleaching of a low-density, substantially uncompacted, porous fluffed cellulosic pulp
US3650887A (en) * 1969-04-21 1972-03-21 Kimberly Clark Co Wood pulp bleaching process utilizing peroxide-silicate bleaching solution
US3660225A (en) * 1968-07-11 1972-05-02 South African Pulp Paper Delignification and bleaching of cellulose pulp layers with oxygen gas
US3663357A (en) * 1969-11-27 1972-05-16 Pulp Paper Res Inst Bleaching of mechanical cellulosic pulp with ozone in the presence of a peroxygen compound
US4022965A (en) * 1975-01-13 1977-05-10 Crown Zellerbach Corporation Process for producing reactive, homogeneous, self-bondable lignocellulose fibers
US4065347A (en) * 1975-02-26 1977-12-27 Molnlycke Ab Method of producing fluffed pulp
US5314583A (en) * 1989-08-16 1994-05-24 Maschinenfabrik Andritz Actiengesellschaft Process for the comminution of materials and plant for carrying out the process
US20040231811A1 (en) * 2001-06-21 2004-11-25 Per Engstrand Method of producing bleached thermomechanical pulp (tmp) or bleached chemithermomechanical pulp (ctmp)
US20050279467A1 (en) * 2004-06-22 2005-12-22 Fort James Corporation Process for high temperature peroxide bleaching of pulp with cool discharge

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB624244A (en) * 1946-03-30 1949-05-31 Du Pont Improvements in bleaching wood pulps
US3055795A (en) * 1957-09-09 1962-09-25 Bauer Bros Co Handling of paper pulp
US3316141A (en) * 1963-10-05 1967-04-25 Svenska Cellulosa Ab Process of dewatering sulphate pulp to contain less shives therein

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB624244A (en) * 1946-03-30 1949-05-31 Du Pont Improvements in bleaching wood pulps
US2492047A (en) * 1946-03-30 1949-12-20 Du Pont Bleaching wood pulp
US3055795A (en) * 1957-09-09 1962-09-25 Bauer Bros Co Handling of paper pulp
US3316141A (en) * 1963-10-05 1967-04-25 Svenska Cellulosa Ab Process of dewatering sulphate pulp to contain less shives therein

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3630828A (en) * 1968-05-13 1971-12-28 Pulp Paper Res Inst Bleaching of a low-density, substantially uncompacted, porous fluffed cellulosic pulp
US3660225A (en) * 1968-07-11 1972-05-02 South African Pulp Paper Delignification and bleaching of cellulose pulp layers with oxygen gas
US3650887A (en) * 1969-04-21 1972-03-21 Kimberly Clark Co Wood pulp bleaching process utilizing peroxide-silicate bleaching solution
US3663357A (en) * 1969-11-27 1972-05-16 Pulp Paper Res Inst Bleaching of mechanical cellulosic pulp with ozone in the presence of a peroxygen compound
US3627630A (en) * 1969-12-04 1971-12-14 Beloit Corp Method of flash drying pulp
US4022965A (en) * 1975-01-13 1977-05-10 Crown Zellerbach Corporation Process for producing reactive, homogeneous, self-bondable lignocellulose fibers
US4065347A (en) * 1975-02-26 1977-12-27 Molnlycke Ab Method of producing fluffed pulp
US5314583A (en) * 1989-08-16 1994-05-24 Maschinenfabrik Andritz Actiengesellschaft Process for the comminution of materials and plant for carrying out the process
USRE36033E (en) * 1989-08-16 1999-01-12 Maschinenfabrik Andritz Actiengesellschaft Process for the comminution of materials and plants for carrying out the process
US20040231811A1 (en) * 2001-06-21 2004-11-25 Per Engstrand Method of producing bleached thermomechanical pulp (tmp) or bleached chemithermomechanical pulp (ctmp)
US20050279467A1 (en) * 2004-06-22 2005-12-22 Fort James Corporation Process for high temperature peroxide bleaching of pulp with cool discharge
US7297225B2 (en) 2004-06-22 2007-11-20 Georgia-Pacific Consumer Products Lp Process for high temperature peroxide bleaching of pulp with cool discharge

Also Published As

Publication number Publication date
ES345665A1 (es) 1968-11-16
NO120217B (es) 1970-09-14
FR1542837A (fr) 1968-10-18
DE1621692A1 (de) 1971-06-03
SE341519B (es) 1971-12-27
CH483518A (de) 1969-12-31

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