US3316141A - Process of dewatering sulphate pulp to contain less shives therein - Google Patents

Process of dewatering sulphate pulp to contain less shives therein Download PDF

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Publication number
US3316141A
US3316141A US401118A US40111864A US3316141A US 3316141 A US3316141 A US 3316141A US 401118 A US401118 A US 401118A US 40111864 A US40111864 A US 40111864A US 3316141 A US3316141 A US 3316141A
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Prior art keywords
pulp
shives
press
dewatering
pipe
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Expired - Lifetime
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US401118A
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English (en)
Inventor
Bergholm Carl Arne
Malm Gustaf Erik
Astrom Johan
Sylla Klaus Ferdinand
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Svenska Cellulosa AB
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Svenska Cellulosa AB
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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F1/00—Wet end of machines for making continuous webs of paper
    • D21F1/66—Pulp catching, de-watering, or recovering; Re-use of pulp-water
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S159/00—Concentrating evaporators
    • Y10S159/25—Decant, press, centrifuge

Definitions

  • shives which are more or less diflicult to defiber in connection with the pulping of the pulp in the paper mill.
  • shives are the cause of more or less conspicuous spots in the uncalendered paper, such spots, under unfavorable conditions, showing up in the calendered paper as greasy blotches, so-called fish eyes.
  • the present invention which relates to a method of dewatering cellulose pulp, especially unbleached sulphate pulp, it is possible to produce a flash dried pulp having a shives level which is acceptable to exacting customers.
  • This is achieved by dewatering, in one step in a press, -a pulp of at least 1% concentration, in such a manner that the pressed pulp will have a dry content of 40-60, preferentially 47-52, percent by weight, that the pressed material is subjected to a flufling operation and that the flufled material is caused, in at least one step, to accompany a heated gas until its average dry content amounts to 90-95, preferentially to 91.593.5, percent by weight.
  • FIGURE 1 shows, diagrammatically, a flash drying plant and FIGURE 2 shows a diagram of the number of shives in evenly and unevenly dried pulps.
  • the pulp consists of a sulphite-, a sulphateor a semichemical pulp, produced in any conventional manner. After washing and screening the pulp is subjected to mechanical treatment in Kollergangs or other equivalent devices. After dilution the pulp is transferred to a vat 1, from where it is, by means of a pump 2, caused to flow to a rotary drum filter 3. After the filter 3 the pulp is diluted with backwater from a press 4 of any optional kind. The backwater, which immediately after the press has a temperature of 5070 C., through a conduit 5 is transferred to a trough 6 arranged beside the filter 3, a feed screw 7 in said trough causing the pulp to move to a pipe 8.
  • the pulp is acidified by means of, for instance, a water solution of S0 which is supplied through a conduit 9.
  • the pulp is then transferred to a vat 10 from where it is, by means of a pump 11 and through a conduit 12 transferred to the trough 13 of the press.
  • a device (not shown) keeps the concentration of the pulp in the conduit 12 at the desired value.
  • a flow meter 14 which controls the motor of the pump 11 in such a manner that a predetermined amount of pulp is, per unit of time, supplied to the trough 13 of the press.
  • FIGURE 1 3316,141 Patented Apr. 25, 1967
  • the rolls are tight against the trough 13 in such a manner that the pulp suspension in the trough 13 will be under pressure.
  • the pressure of liquid in the trough 13 and the lineal pressure between the rolls of the press 4 are adjusted automatically to the desired values by means of adjusting means (not shown).
  • the web of pulp coming from the press 4 is roughly shredded [by a rough shredder, such as a spike roll 15.
  • a rough shredder such as a spike roll 15.
  • the pulp is conveyed to a vertical pipe 16-which conveying operation may be carried out by means of an endless belt (not shown)and at the bottom opening of said pipe 16 the pulp is suspended in air coming from a pipe 17, said air having seen heated up to a temperature of 11()-160 C., preferentially to 130-150 C.
  • a fan (not shown) transfers the material, suspended in air, to a separator 18, in which the main part (95% of the moist transportation air is separated from the pulp, which is then fiuffed by means of rotating fluffing rolls 19.
  • the pulp is conveyed through a pipe 20 and is caused to travel together with a current or" gas, which comes from a pipe 21 and which has been heated up to a temperature of between 250- 400 C., preferably to 275-315 C., preferentially to 280300 C.
  • a fan 22 transfers the pulp, suspended in the heated air, to a vertical pipe 23, which is surrounded by a pipe 24 closed at its upper end.
  • the suspended pulp is conveyed upwards within the pipe 23 until it is deflected by the upper closed end of the pipe 24 and caused to descend through the annular space between the two concentric pipes 23 and 24.
  • Through the pipe 20 there is conveyed 1.53.75 tons of pulp (calculated as 90% dry) per hour. This amount of pulp is suspended in 20,00060,000 cu. m, of gas per hour, said quantity of gas being conveyed through the pipe 21.
  • the suspended pulp After having passed through the drying tower, consisting of the pipes 23 and 24, the suspended pulp is conveyed through a pipe 25 to a separator 26, in which the major part (90-95%) of the gas is separated.
  • the gas leaves the separator 26 at a temperature of 125 160 C.
  • the pulp is conveyed through a pipe 27, at the mouth of which the pulp is suspended in air, heated up to 250 C., preferably to 160- 180 C., which is supplied in an amount of 20,000- 60,000 cu. m./hr. and which comes from a pipe 28.
  • This quantity of air is heated by vapor in a heat exchanger 29.
  • the quantity of gas conveyed through the pipe 21 is obtained partly from the heat exchanger 29, partly from a burner 30 which is fed with oil from a tank 31.
  • a fan 32 conveys the air-suspended pulp to a drying tower, consisting of two concentric pipes 33 and 34, from where the pulp, through a pipe 35, is conveyed to separators 36, where part (40-60%) of the air is separated at a temperature of -16() (1., preferably at 150 C.
  • the separated air is conveyed through the pipe 17 to the lower part of the pipe 16 where it will then serve as transportation air for the freely falling pulp coming from the pipe 16.
  • the pulp From the separators 36 the pulp, through pipes 37, is conveyed into a pipe 38 the free end of which is provided with a valve 39, controlling a supply of cold air to the pipe 38.
  • the mixture of pulp and air is then, by means of a fan 40, conveyed through a pipe 41 to separators 42.
  • the pulp is cooled in such a manner that during the temperature of the pulp is 25 -95 60 C. Should the pulp become too of cooling by the C., preferably 30- voluminous because cold air from the valve 39, said valve pressing operation in a sheet press 43 the j sulting in already formed shives the flow of pulp is laminar.
  • a shive causes a fish eye in the calendered paper it possesses a certain incompressibility and a certain thickness in relation to the thickness of the paper. In case a shive is thick enough and incompressible in relation to the thickness of the paper, it will fall out and make a hole in the calendered paper.
  • the shives are more or less uniformly distributed in the bale.
  • the pulp in the press trough 13 is freed from shives by screening et cetera.
  • the shives are not formed until in connection with the dewatering by pressing.
  • On cooking the pulp care should be taken that the chlorine number of the pulp will be as low as possible.
  • the binding power between the fibers, forming a shive and extending substantially parallel to each other due to the pressing operation will decrease with a sinking chlorine number of the pulp in the press trough 13.
  • the amount of shives in the finished pulp varies in relation to the temperature of the pulp while the same is being subjected to dewatering in the press 4. If the temperature of the pulp in the press trough 13 is increased then a higher dry content of the pulp will be obtained after the press 4. In case of one and the same dry content of the pulp after the press 4 this means that the lineal pressure and, hence, also the formation of shives between the rolls of the press 4 may be reduced according as the temperature of the pulp in the press trough 13 is increased.
  • the temperature of the pulp in the press trough 13 of the press 4 is kept at a temperature of 60- 100 C., preferably at -85 C.
  • the amount of shives in the finished pulp will be less, if the pulp is evenly distributed at the moment of pressing than if it were unevenly distributed.
  • said even distribution may be obtained by the use of certain insets controlling the flow of pulp in the nip between the rolls, or by subjecting the pulp in the press nip to vibrations, ultrasonics etc.
  • the amount of shives in the finished pulp increases in relation to the dry content of the pulp coming from the press 4. If the pulp is dewatered in the press 4 to such a high degree that after the pressing operation the dry content will be above 60% then there is obtained such a considerable amount of shives in the finished pulp that subsequent treatments of the pulp will not be able to reduce the number of shives to an acceptable level.
  • the dry content of the pulp immediately after the press is kept at 40-60, preferably at 47-52, percent by weight.
  • the flufl'ing of the pulp may also be combined with a separation treatment.
  • a fluffer (not shown)
  • those fibers which are disengaged in a higher degree fall down into a hopper located beside the fluft'er and the fibers which are not disengaged in such a high degree fall into a hopper, which is located farther on in the direction of said path and which is, moreover, located quite near said first-mentioned fluffer.
  • the fibers which are disengaged in a higher degree are subjected to flash drying, the less disengaged fibers being returned to the inlet opening of the fiutfer.
  • a selective, electric drying preferably dielectric drying, drying by radiation et cetera.
  • the temperature of the air, its humidity et cetera may be adjusted in such a manner that either the average dry content of the pulp is increased or also in such a manner that both the dry content of the bundles of fibers is increased and the dry content of the remaining fibers in the pulp is lowered.
  • a process for manufacturing sulphate cellulose pulp which comprises dewatering a pulp having a dry solids content of at least 1% by weight and not more than about 4.5% by weight by a pressing operation to a pressed pulp having a dry solids content of -60%, subjecting the resulting pressed pulp to a flufiing operation, and drying the resulting fiutfed pulp and contacting it cocurrently with a heated drying gas until its average dry content is to by weight, the pulp slurry prior Dr content, D content, Average dry Estimated amount Found amount of Shives weight, Shives weight, perc nt 80 parts per nt 20 parts content of the of shives acc. to the shives, number/ lug/100 gm.
  • FIGURE 2 illustrates the relationship between the t0 the dewaterlng p being fi d so that the pH of number of shives per 100 gm. of pulp and the average dry content of the final pulp.
  • the unbroken line indicates the values of pulps produced in accordance with point A and the dashed line indicates pulps produced in accordance with point B. From FIGURE 2 it will appear, inter alia, that the lower the average dry content of the pulp the greater the risks of having a great difference between the moistest and the driest parts of the pulp, which means that the pulp should be dried as evenly as possible.

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US401118A 1963-10-05 1964-10-02 Process of dewatering sulphate pulp to contain less shives therein Expired - Lifetime US3316141A (en)

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SE10927/63A SE317864B (enrdf_load_stackoverflow) 1963-10-05 1963-10-05

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GB (1) GB1033048A (enrdf_load_stackoverflow)
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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3414469A (en) * 1965-08-19 1968-12-03 West Virginia Pulp & Paper Co Treatment of flash dried pulp to reduce nodules therein
US3440135A (en) * 1965-12-13 1969-04-22 Kimberly Clark Co Process for crosslinking cellulosic fibers during gas suspension of fibers
US3492199A (en) * 1966-10-04 1970-01-27 Fmc Corp Bleaching fluffed mechanical wood pulp with hydrogen peroxide
US3497418A (en) * 1966-08-22 1970-02-24 Niro Atomizer As Method for drying fibrous masses
US3499823A (en) * 1965-08-24 1970-03-10 Mo Och Domsjoe Ab Method of inhibiting the formation of fiber-knots in paper pulp and product
US3627630A (en) * 1969-12-04 1971-12-14 Beloit Corp Method of flash drying pulp
US3655505A (en) * 1965-06-25 1972-04-11 Pulp Paper Res Inst Two-stage purification of fibrous cellulose material employing gaseous chlorine dioxide in one stage and a peroxygen compound in the other
US5314583A (en) * 1989-08-16 1994-05-24 Maschinenfabrik Andritz Actiengesellschaft Process for the comminution of materials and plant for carrying out the process
CN116876250A (zh) * 2023-07-07 2023-10-13 浙江金龙再生资源科技股份有限公司 一种提高松厚度的无露底灰纸板生产装置及其工艺

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1258568A (en) * 1916-05-29 1918-03-05 Guy C Howard Process and apparatus for treating paper-pulp.
US1861184A (en) * 1927-02-04 1932-05-31 American Voith Contact Co Method for converting liquid paper pulp into a consistent mass suitable for storage, etc., or into bales for shipment
US2409747A (en) * 1944-01-19 1946-10-22 American Viscose Corp Drying staple fibers
US2974420A (en) * 1956-10-02 1961-03-14 Courtaulds Ltd Preparation of wood pulp
US3055795A (en) * 1957-09-09 1962-09-25 Bauer Bros Co Handling of paper pulp
US3069784A (en) * 1958-05-19 1962-12-25 Courtaulds Ltd Preparation of wood pulp

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1258568A (en) * 1916-05-29 1918-03-05 Guy C Howard Process and apparatus for treating paper-pulp.
US1861184A (en) * 1927-02-04 1932-05-31 American Voith Contact Co Method for converting liquid paper pulp into a consistent mass suitable for storage, etc., or into bales for shipment
US2409747A (en) * 1944-01-19 1946-10-22 American Viscose Corp Drying staple fibers
US2974420A (en) * 1956-10-02 1961-03-14 Courtaulds Ltd Preparation of wood pulp
US3055795A (en) * 1957-09-09 1962-09-25 Bauer Bros Co Handling of paper pulp
US3069784A (en) * 1958-05-19 1962-12-25 Courtaulds Ltd Preparation of wood pulp

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3655505A (en) * 1965-06-25 1972-04-11 Pulp Paper Res Inst Two-stage purification of fibrous cellulose material employing gaseous chlorine dioxide in one stage and a peroxygen compound in the other
US3414469A (en) * 1965-08-19 1968-12-03 West Virginia Pulp & Paper Co Treatment of flash dried pulp to reduce nodules therein
US3499823A (en) * 1965-08-24 1970-03-10 Mo Och Domsjoe Ab Method of inhibiting the formation of fiber-knots in paper pulp and product
US3440135A (en) * 1965-12-13 1969-04-22 Kimberly Clark Co Process for crosslinking cellulosic fibers during gas suspension of fibers
US3497418A (en) * 1966-08-22 1970-02-24 Niro Atomizer As Method for drying fibrous masses
US3492199A (en) * 1966-10-04 1970-01-27 Fmc Corp Bleaching fluffed mechanical wood pulp with hydrogen peroxide
US3627630A (en) * 1969-12-04 1971-12-14 Beloit Corp Method of flash drying 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
CN116876250A (zh) * 2023-07-07 2023-10-13 浙江金龙再生资源科技股份有限公司 一种提高松厚度的无露底灰纸板生产装置及其工艺
CN116876250B (zh) * 2023-07-07 2024-05-17 浙江金龙再生资源科技股份有限公司 一种提高松厚度的无露底灰纸板生产装置及其工艺

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SE317864B (enrdf_load_stackoverflow) 1969-11-24
GB1033048A (en) 1966-06-15

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