US3497418A - Method for drying fibrous masses - Google Patents

Method for drying fibrous masses Download PDF

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Publication number
US3497418A
US3497418A US661889A US3497418DA US3497418A US 3497418 A US3497418 A US 3497418A US 661889 A US661889 A US 661889A US 3497418D A US3497418D A US 3497418DA US 3497418 A US3497418 A US 3497418A
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United States
Prior art keywords
pulp
nodules
air
drying
paper
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Expired - Lifetime
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US661889A
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English (en)
Inventor
Allan Thale
Olav Bjorn Hovstad
Lennart Ivnas
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
GEA Process Engineering AS
Fiskeby AB
Original Assignee
Niro Atomizer AS
Fiskeby AB
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Publication of US3497418A publication Critical patent/US3497418A/en
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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
    • D21C9/18—De-watering; Elimination of cooking or pulp-treating liquors from the pulp
    • D21C9/185—De-watering; Elimination of cooking or pulp-treating liquors from the pulp comprising at least one step where the pulp is suspended in a gaseous medium, e.g. flash drying

Definitions

  • This invention relates to a method of drying fibrous pulps, such as groundwood, sulphate, sulphite or semichemical pulps where, subsequent to dehydration to a maximum dry-matter content of 65 percent, the pulp is treated in a device for fiuifing the pulp and then dried, for example by pneumatical means.
  • fibrous pulps such as groundwood, sulphate, sulphite or semichemical pulps
  • Such method forms, by way of example, a stage in the treatment of fibrous material used for the manufacture of paper. Particularly in this case it is of importance to avoid the formation of knots or nodules (in the following the term nodules will be used) in the fibrous material to the highest possible degree, as such nodules will appear as spots or so-called fish eyes in the finished paper.
  • nodules are due to many different reasons, mechanical as well as chemical, and before as well as after the flufiing process, and various methods have been suggested for reducing the effect of the various reasons, or for wholly or partially removing said reasons, as well as for removing or dissolving nodules already formed. Since it is not possible to observe with any certainty the nodules until the paper is finished, it is difficult to safely judge the individual reasons for the formation of nodules, or the effects of the measures taken with a view to avoiding such formation of nodules.
  • This invention is based on the recognition that the particle size and density produced during the fiuffing process are of decisive importance for the formation of nodules, not only directly but also indirectly during the subsequent drying process, as well as during the possible subsequent storing process which, as is known, involves certain ageing processes, during which nodules may develop in the pulp, probably as a consequence of an equalization of a certain irregularity in the distribution of moisture.
  • the characteristic of the method according to the invention consists in the fiuifing process being carried out in such a way that the modified Stoke diameter d of the particles produced by the fluffing process, is for all 3,497,418 Patented Feb. 24, 1970 of the particles subsequent to drying not more than 2.0- 10- preferably not more than 17-10" g./cm.
  • the two factors of the product which in the .usual manner is deignated as the modified Stoke diameter can hardly be determined in a simple way, but by means of well-known formulae it can be seen that the stated limit of the product means that the terminal falling velocity of the particles must be about 600 cm./ see. as a maximum, preferably 500 cm./sec. as a maximum.
  • nodules in the pulp involves deterior'ation of the quality of the paper manufactured.
  • the effect is to a very high degree dependent on the type of paper, notably the thickness of the paper.
  • Dependent on the dimensions of the nodules, the defects may vary from slight blemishes to the complete destruction of the functional qualities of the paper.
  • a nodule may be defined as an accumulation of fibres which, structurally, differs from the surrounding fibres and is visible in the paper manufactured.
  • the pulp was heat-treated at C. for 12 hours, enclosed in a plastic bag, whereby the building up of latent nodules was completed. After the heat-treatment the pulp was slushed in a defibrator in the standardized way, and subsequently a sheet of paper was produced and the number of nodules determined. Fibre nodules visible to the eye in a sheet of paper so produced are then defined in an unequivocal manner.
  • EXAMPLE 1 Wet sulphate pulp was pressed to contain 50 percent of dry matter, whereupon the pulp was fluffed in a mechanical shredder which was so set as to deliver five different densities and particle sizes. The five different samples were later dried in the laboratory in a standardized way to contain percent of dry matter. Next, the terminal falling velocity was determined at room temperature in respect of the five samples, and the velocity was found to be 7.3 m./sec., 6.7 m./sec., 6.0 m./sec., 5.6 m./sec. and 4.9 m./sec.
  • a suitable pneumatical fiuffer can be designed as a tube, wherein mechanical obstacles, such as inclined plates or screens are arranged in spaced-apart relationship, or the tube may be provided with restrictions. With such a fiuffer it is possible when applying the required air velocity to obtain a satisfactory defibration of the pulp, without any resulting compression of the fibres, in such a Way that the requirements made in conjunction with the present invention can without difficulty be complied with.
  • Cellulose pulp in the form of a 3.5 percent suspension is fed through conduit 1 to a dewatering press 2 at a rate of 160,000 kg. per hour corresponding to 6,250 kg. of air-dry matter per hour.
  • Press 2 may be of any appr0- priate type, as for instance the well-known Impco press manufactured by Messrs. Improved Machinery Inc., Nashua, NH.
  • the pulp is dewatered or preconcentrated to a concentration of 48 percent in press 2.
  • the concentrated pulp leaves the press through pipe 3 delivering the pulp to a shredder or flufier 4 in which the pulp is shredded or fiuffed so as to obtain the particle size desired, which means that the particles, when subsequently dried to an air-dry condition, i.e. to a content of dry matter of 90 percent, attain a Stokes diameter not exceeding 2.0- 10 g./cm., preferably not more than 1.7-10 g./cm.
  • a shredder such as described in our co-pending patent application mentioned above can be used, by means of which any desired particle size, within practical limits, can be obtained by adjusting the depth of engagement between the toothed rollers and their speed of rotation.
  • the pulp is conveyed through pipes 5 and 7 by means of a conveying fan or blower 6, which draws in conveying air through a pipe 8 connected to the pipe 5 at a point between the shredder 4 and the fan 6.
  • the air passes through pipe 8 at a rate of 36,000 kg. per hour, moreover, a certain amount of air is drawn in through the shredder, so that the rate of the air conveying the pulp through pipe 7 amounts to about 40,000 kg. per hour.
  • the drying duct 11 is a vertical tube having e.g. a diameter of 2 metres and a height of 10 metres.
  • the drying air is supplied at a rate of 60,000 kg. .per hour and at a temperature of 150 C.
  • the pulp is dried to a concentration of approximately 55 percent and is separated from the air in a cyclone 14.
  • the air and the vapour leave the cyclone 14 through a pipe 15 at a temperature of C.
  • the concentrated pulp is removed from the cyclone 14 through an air lock 16 by means of drying air supplied at a rate of 60,000 kg. per hour and at a temperature of 350 C. and passes through a pipe 17 and a fan 18 to a second drying duct 19 which is similar to the first drying duct 11.
  • the pulp is dried to a concentration of percent corresponding to what is termed air-dry.
  • the air-dry matter is separated from the drying air in a cyclone 20 from which the air and vapour leave through the above-mentioned pipe 12 leading to the first drying duct 11.
  • the air-dry matter is removed from the cyclone 20 through an air lock 21 by means of conveying air supplied by a fan 22 and fed through a conveying tube 23 to a cyclone 24.
  • the air locks 16 and 21 may be of the type described in U.S. patent specification No. 3,195,241.
  • a method of drying fibrous pulps comprising ground- Wood, sulphate, sulphite, or semichemical pulps comprising- (a) dehydrating the pulp to a maximum dry-matter content of 65 percent;

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Paper (AREA)
US661889A 1966-08-22 1967-08-21 Method for drying fibrous masses Expired - Lifetime US3497418A (en)

Applications Claiming Priority (1)

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SE11317/66A SE311590B (enrdf_load_html_response) 1966-08-22 1966-08-22

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FI (1) FI45249C (enrdf_load_html_response)
SE (1) SE311590B (enrdf_load_html_response)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3770575A (en) * 1972-05-26 1973-11-06 Westavco Corp Method of making a hydrophobic fibrous product
US3812595A (en) * 1972-06-21 1974-05-28 D Engelhart Method of and means for flash drying naturally occurring oilseeds
US4343680A (en) * 1981-03-06 1982-08-10 International Paper Company Hydrophobic oleophilic wood pulp
US4474949A (en) * 1983-05-06 1984-10-02 Personal Products Company Freeze dried microfibrilar cellulose
US4557800A (en) * 1982-06-04 1985-12-10 James River Corporation Process of forming a porous cellulosic paper from a thermal treated cellulosic non-bonding pulp
US20040203308A1 (en) * 2003-04-09 2004-10-14 Ko Young Chan Process for making absorbent material
US6837970B2 (en) 2001-12-18 2005-01-04 Kimberly-Clark Worldwide, Inc. Wood pulp fiber morphology modifications through thermal drying

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2474314A (en) * 1944-11-28 1949-06-28 Johns Manville Method and apparatus for size reduction and fiberizing of crude fibrous materials
US2627375A (en) * 1948-01-05 1953-02-03 Weyerhaeuser Timber Co Separation of bark components
US3055795A (en) * 1957-09-09 1962-09-25 Bauer Bros Co Handling of paper pulp
US3195241A (en) * 1961-05-18 1965-07-20 Niro Atomizer As Air lock arrangement and method for transferring a powder from a chamber maintaininga rotary flow of gas, to pneumatic conveyor plant
US3316141A (en) * 1963-10-05 1967-04-25 Svenska Cellulosa Ab Process of dewatering sulphate pulp to contain less shives therein
US3364101A (en) * 1961-12-07 1968-01-16 Niro Atomizer As Method and apparatus for the agglom-eration of resins and crills in the production of paper pulp
US3414469A (en) * 1965-08-19 1968-12-03 West Virginia Pulp & Paper Co Treatment of flash dried pulp to reduce nodules therein

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2474314A (en) * 1944-11-28 1949-06-28 Johns Manville Method and apparatus for size reduction and fiberizing of crude fibrous materials
US2627375A (en) * 1948-01-05 1953-02-03 Weyerhaeuser Timber Co Separation of bark components
US3055795A (en) * 1957-09-09 1962-09-25 Bauer Bros Co Handling of paper pulp
US3195241A (en) * 1961-05-18 1965-07-20 Niro Atomizer As Air lock arrangement and method for transferring a powder from a chamber maintaininga rotary flow of gas, to pneumatic conveyor plant
US3364101A (en) * 1961-12-07 1968-01-16 Niro Atomizer As Method and apparatus for the agglom-eration of resins and crills in the production of paper pulp
US3316141A (en) * 1963-10-05 1967-04-25 Svenska Cellulosa Ab Process of dewatering sulphate pulp to contain less shives therein
US3414469A (en) * 1965-08-19 1968-12-03 West Virginia Pulp & Paper Co Treatment of flash dried pulp to reduce nodules therein

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3770575A (en) * 1972-05-26 1973-11-06 Westavco Corp Method of making a hydrophobic fibrous product
US3812595A (en) * 1972-06-21 1974-05-28 D Engelhart Method of and means for flash drying naturally occurring oilseeds
US4343680A (en) * 1981-03-06 1982-08-10 International Paper Company Hydrophobic oleophilic wood pulp
US4557800A (en) * 1982-06-04 1985-12-10 James River Corporation Process of forming a porous cellulosic paper from a thermal treated cellulosic non-bonding pulp
US4474949A (en) * 1983-05-06 1984-10-02 Personal Products Company Freeze dried microfibrilar cellulose
US6837970B2 (en) 2001-12-18 2005-01-04 Kimberly-Clark Worldwide, Inc. Wood pulp fiber morphology modifications through thermal drying
US20050045289A1 (en) * 2001-12-18 2005-03-03 Ko Young Chan Wood pulp fiber morphology modifications through thermal drying
US20040203308A1 (en) * 2003-04-09 2004-10-14 Ko Young Chan Process for making absorbent material

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Publication number Publication date
FI45249B (enrdf_load_html_response) 1971-12-31
SE311590B (enrdf_load_html_response) 1969-06-16
FI45249C (fi) 1972-04-10

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