WO2002022946A1 - Deaeration system for feeding stock into a headbox of a paper machine or equivalent - Google Patents

Deaeration system for feeding stock into a headbox of a paper machine or equivalent Download PDF

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Publication number
WO2002022946A1
WO2002022946A1 PCT/FI2001/000793 FI0100793W WO0222946A1 WO 2002022946 A1 WO2002022946 A1 WO 2002022946A1 FI 0100793 W FI0100793 W FI 0100793W WO 0222946 A1 WO0222946 A1 WO 0222946A1
Authority
WO
WIPO (PCT)
Prior art keywords
deaeration
duct
deaeration tank
stock
tank
Prior art date
Application number
PCT/FI2001/000793
Other languages
French (fr)
Inventor
Kari Kokkonen
Original Assignee
Metso Paper, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Metso Paper, Inc. filed Critical Metso Paper, Inc.
Priority to AU2001287767A priority Critical patent/AU2001287767A1/en
Publication of WO2002022946A1 publication Critical patent/WO2002022946A1/en

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Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21D—TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
    • D21D5/00—Purification of the pulp suspension by mechanical means; Apparatus therefor
    • D21D5/26—De-aeration of paper stock
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D19/00—Degasification of liquids
    • B01D19/0042—Degasification of liquids modifying the liquid flow
    • 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

Definitions

  • the invention relates to a deaeration system for feeding stock into a headbox of a paper machine or equivalent.
  • Air is particularly detrimental in machines which make coated grades because the air left in the stock increases the porosity of paper and causes instability in the feed system of the stock.
  • the deaerator is operated at a relatively low vacuum (30 to 60 kPa), in which connection the tank can be placed on a lower level, but a considerable part of air can nevertheless be removed from the fibre suspension.
  • a vacuum in the deaeration tank is produced by means of a blower.
  • the surface of the wire pit is lowered below the machine level, in which connection the level of the deaeration tank can be further lowered.
  • the deaeration tank is accomplished on the so-called multiple residence principle, in which connection it serves as an equaliser of stock consistency variations.
  • a machine screen is placed before the deaeration tank, in the inlet line of the stock passed into the deaeration tank.
  • the pressure of the headbox increases in the second power with increasing speed of the paper machine. If the screen is placed after the pump, then a machine screen of 10 bar would be needed at a speed of over 2000 m/min, i.e. because of speed, it is advantageous that the screen is placed before the deaeration tank.
  • the deaeration system according to the invention is characterised in that which is stated in the claims.
  • Figure 1 shows a simplified flow diagram of a deaeration system in accordance with the invention.
  • Figure 2 shows another advantageous embodiment of the deaeration system in accordance with the invention.
  • Fig. 1 is an illustration of principle of a deaeration system in accordance with the invention for feeding stock into a headbox of a paper machine.
  • the headbox is designated by the reference numeral 10.
  • the stock is passed from a wire pit 11 through ducts a l3 a to a deaeration tank 11 of a deaerator.
  • the stock is passed in the duct by means of a pump P 2 from the wire pit 12 first to a hydrocyclone unit 16 and therefrom along the duct a 2 through a machine screen 15 to the deaeration tank 11 of the deaerator.
  • the stock from which air has been removed is passed from the deaeration tank further along a duct a 3 by means of a feed pump Pi .
  • the deaeration tank 11 has been disposed at an elevation of up to 15 m from the surface level of the stock. In that connection, high steel structures have been needed to support the tank high above the machine level T.
  • the deaeration tank 11 of the deaerator is thus placed with respect to the machine level T such that the deaeration tank is located at an elevation h of about 3 m - 8 m from the machine level T.
  • the elevation h has been calculated from the machine level T to the surface level of the stock treated in the deaeration tank.
  • the height level of the deaeration tank 11 can be further lowered.
  • the difference of height H between the deaeration tank and the wire pit is in a range of 4 m - 8 m, in which connection the difference of height has been calculated from the surface level of the stock inside the wire pit to the surface level of the stock inside the deaeration tank 11.
  • the vacuum level within the deaeration tank 11 is in a range of 30 kPa - 60 kPa.
  • a vacuum is produced by means of a blower 13 and passed along a duct a 4 into the tank 11, in which connection by means of the vacuum produced in the tank the stock meets a vacuum space and air is released from the stock to said space and further through the duct a 4 to the blower 13 and further out of connection with the equipment.
  • the figure shows with broken lines a droplet separator designated by the reference numeral 14, which can be located between the deaeration tank 11 and the blower 13. From the deaeration tank 11 there is a duct a 5 from an overflow of the deaeration tank and back to the wire pit 12. Fresh stock is passed to the wire pit 12 through a duct bi. Wire water is passed to the wire pit 12 through a duct b 2 as a return circulation from a wire section 17 of a paper machine or equivalent.
  • the machine screen 15 is placed in the duct a 2 between the hydrocyclone unit 16 and the deaeration tank 11. Thus, the machine screen 15 will be located before the deaeration tank 11 of the deaerator when viewed in the flow direction Li of the stock which is being treated.
  • Fig. 2 shows an embodiment of the invention in which there is a duct ai comprising a pump P leading from a wire pit 12 directly to a deaeration tank 11 and there is further a duct a 2 leading from the deaeration tank 11 to a hydrocyclone unit 16, from which accept is passed, pumped by a pump Pi, along a duct a to a machine screen 15 and further to a headbox 10 of a paper machine or a board machine.
  • the duct a 3 comprises the pump Pi on the inlet side of the machine screen 15 with respect to the direction L ⁇ of the stock flow. Fresh stock is passed to the duct a 2 to the suction side of a pump P 3 .
  • a duct a 2 ' for wire water from the deaeration tank 11 leading to the duct a 3 between the pump Pi and the hydrocyclone unit 16.
  • a vacuum in a range of 30 kPa - 60 kPa is produced in the deaeration tank 11 in a manner corresponding to that of the embodiment of Fig. 1 where it is produced by means of the blower 13.
  • the deaeration tank 11 is placed with respect to the machine level T so that the deaeration tank 11 is located at an elevation h of 3 m - 10 m from the machine level T above it.
  • the wire pit 12 is additionally below the machine level T, and the difference of height H between the deaeration tank 11 and the wire pit 12 is in a range of 4 m - 8 m, in which connection the difference of height has been calculated between the surface levels of the stock or wire water in the deaeration tanlc and the wire water in the wire pit.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Paper (AREA)

Abstract

The invention relates to a deaeration system for feeding stock into a headbox (10) of a paper machine or equivalent. The deaeration system comprises a deaeration tank (11), to which a duct (a1, a2) leads from a wire pit (12) either directly or through a hydrocyclone unit (16). The deaeration system comprises a duct (a4) leading to the deaeration tank (11) from a device (13) producing a vacuum in order to produce a vacuum inside the deaeration tank (11). The vacuum in the deaeration tank (11) is in a range of 30 kPa - 60kPa.

Description

Deaeration system for feeding stock into a headbox of a paper machine or equivalent
The invention relates to a deaeration system for feeding stock into a headbox of a paper machine or equivalent.
Separation of the air dispersed in the stock and water from a fibre suspension is accomplished in deaerators, in which a vacuum corresponding to the temperature of the stock is provided. Air is particularly detrimental in machines which make coated grades because the air left in the stock increases the porosity of paper and causes instability in the feed system of the stock.
The investment costs of deaeration are high since, because of high vacuum, heavy tanks must be placed on an elevated level, often even on the roof of the building. Steel structures are high and situated as high as 15 m above the machine level. In that connection, pipes are long extending from the basement all the way up to deaerators.
Moreover, high vacuum evaporates plenty of water, wherefore the vacuum system of an deaerator is usually provided with a condenser to reduce pump capacity. More and more often, the consumption of raw water at new mills is restricted, wherefore cooling water has to be circulated and cooled in separate cooling towers.
The vacuum in today's systems is high, 90 kPa, and the separation of air from fibre suspension is almost complete. When vacuum is dropped to a level of 40 kPa, it is possible to - place the deaerator on a level which is about five metres lower than previously, - produce a vacuum by a blower instead of a vacuum pump because the vacuum level is lower,
- provide the vacuum system without a condenser.
Typical features of the proposed system are:
- The deaerator is operated at a relatively low vacuum (30 to 60 kPa), in which connection the tank can be placed on a lower level, but a considerable part of air can nevertheless be removed from the fibre suspension.
- A vacuum in the deaeration tank is produced by means of a blower. - The surface of the wire pit is lowered below the machine level, in which connection the level of the deaeration tank can be further lowered. The deaeration tank is accomplished on the so-called multiple residence principle, in which connection it serves as an equaliser of stock consistency variations. - A machine screen is placed before the deaeration tank, in the inlet line of the stock passed into the deaeration tank. The pressure of the headbox increases in the second power with increasing speed of the paper machine. If the screen is placed after the pump, then a machine screen of 10 bar would be needed at a speed of over 2000 m/min, i.e. because of speed, it is advantageous that the screen is placed before the deaeration tank.
The deaeration system according to the invention is characterised in that which is stated in the claims.
The invention will be described below with reference to one preferred embodiment of the invention shown in Fig. 1 of the appended drawing, to which embodiment the invention is, however, not meant to be exclusively confined.
Figure 1 shows a simplified flow diagram of a deaeration system in accordance with the invention. Figure 2 shows another advantageous embodiment of the deaeration system in accordance with the invention.
Fig. 1 is an illustration of principle of a deaeration system in accordance with the invention for feeding stock into a headbox of a paper machine. In Fig. 1, the headbox is designated by the reference numeral 10. The stock is passed from a wire pit 11 through ducts al3 a to a deaeration tank 11 of a deaerator. The stock is passed in the duct by means of a pump P2 from the wire pit 12 first to a hydrocyclone unit 16 and therefrom along the duct a2 through a machine screen 15 to the deaeration tank 11 of the deaerator. The stock from which air has been removed is passed from the deaeration tank further along a duct a3 by means of a feed pump Pi. to an inlet header J of the headbox 10. In the arrangements in accordance with the state of the art, the deaeration tank 11 has been disposed at an elevation of up to 15 m from the surface level of the stock. In that connection, high steel structures have been needed to support the tank high above the machine level T. In the system in accordance with the invention, the deaeration tank 11 of the deaerator is thus placed with respect to the machine level T such that the deaeration tank is located at an elevation h of about 3 m - 8 m from the machine level T. The elevation h has been calculated from the machine level T to the surface level of the stock treated in the deaeration tank. When the wire pit 12 is additionally placed below the machine level T, the height level of the deaeration tank 11 can be further lowered. Advantageously, the difference of height H between the deaeration tank and the wire pit is in a range of 4 m - 8 m, in which connection the difference of height has been calculated from the surface level of the stock inside the wire pit to the surface level of the stock inside the deaeration tank 11. The vacuum level within the deaeration tank 11 is in a range of 30 kPa - 60 kPa.
As shown in Fig. 1, a vacuum is produced by means of a blower 13 and passed along a duct a4 into the tank 11, in which connection by means of the vacuum produced in the tank the stock meets a vacuum space and air is released from the stock to said space and further through the duct a4 to the blower 13 and further out of connection with the equipment. The figure shows with broken lines a droplet separator designated by the reference numeral 14, which can be located between the deaeration tank 11 and the blower 13. From the deaeration tank 11 there is a duct a5 from an overflow of the deaeration tank and back to the wire pit 12. Fresh stock is passed to the wire pit 12 through a duct bi. Wire water is passed to the wire pit 12 through a duct b2 as a return circulation from a wire section 17 of a paper machine or equivalent.
The machine screen 15 is placed in the duct a2 between the hydrocyclone unit 16 and the deaeration tank 11. Thus, the machine screen 15 will be located before the deaeration tank 11 of the deaerator when viewed in the flow direction Li of the stock which is being treated.
Fig. 2 shows an embodiment of the invention in which there is a duct ai comprising a pump P leading from a wire pit 12 directly to a deaeration tank 11 and there is further a duct a2 leading from the deaeration tank 11 to a hydrocyclone unit 16, from which accept is passed, pumped by a pump Pi, along a duct a to a machine screen 15 and further to a headbox 10 of a paper machine or a board machine. The duct a3 comprises the pump Pi on the inlet side of the machine screen 15 with respect to the direction L\ of the stock flow. Fresh stock is passed to the duct a2 to the suction side of a pump P3. hi addition, there may be a duct a2' for wire water from the deaeration tank 11 leading to the duct a3 between the pump Pi and the hydrocyclone unit 16. A vacuum in a range of 30 kPa - 60 kPa is produced in the deaeration tank 11 in a manner corresponding to that of the embodiment of Fig. 1 where it is produced by means of the blower 13. As a water separator in a duct a4 there is only a droplet separator 14. The deaeration tank 11 is placed with respect to the machine level T so that the deaeration tank 11 is located at an elevation h of 3 m - 10 m from the machine level T above it. Advantageously, the wire pit 12 is additionally below the machine level T, and the difference of height H between the deaeration tank 11 and the wire pit 12 is in a range of 4 m - 8 m, in which connection the difference of height has been calculated between the surface levels of the stock or wire water in the deaeration tanlc and the wire water in the wire pit. There is a duct a5 provided for an overflow from the deaeration tank 11 back to the wire pit 12. Fresh stock is fed to the duct a2 to the suction side of the pump P3.

Claims

Claims
1. A deaeration system for feeding stock into a headbox (10) of a paper machine or equivalent, which deaeration system comprises a deaeration tank (11), to which a duct (a\, a ) leads from a wire pit (12) either directly or through a hydrocyclone unit (16), and which deaeration system comprises a duct (a4) leading to the deaeration tank (11) from a device (13) producing a vacuum in order to produce a vacuum inside the deaeration tank (11), and which system comprises a duct (a3) for passing the stock to the headbox (10), characterised in that the vacuum in the deaeration tank (11) is in a range of 30 kPa - 60 kPa.
2. A deaeration system according to claim 1, characterised in that the deaeration tank has been disposed at an elevation of 3 m - 10 m from the machine level (T), in which connection said elevation (h) is measured from the surface level of the stock in the deaeration tank (11) to the machine level (T).
3. A deaeration system according to claim 1 or 2, characterised in that the device producing a vacuum in the deaeration tank (11) is a blower (13) and that between the deaeration tank (11) and the blower (13) there is no condenser but there is only a droplet separator (14) as a water separator.
4. A deaeration system according to claim 1, 2 or 3, characterised in that there is a machine screen (15) which has been disposed between the wire pit (12) and the deaeration tank (11), advantageously in a duct (a2) between the hydrocyclone unit (16) and the deaeration tank (11).
5. A deaeration system according to any one of the preceding claims, characterised in that the wire pit (12) is disposed below the machine level (T) and that the difference of height (H) between the surface of the stock or wire water in the wire pit (12) and the surface of the stock or wire water in the deaeration tank (11) is in a range of 4 m - 8 m.
6. A deaeration system according to claim 1, characterised in that a duct (ai) leads from the wire pit (12) to the hydrocyclone unit (16) and from the hydrocyclone unit (16) there is a duct to the deaeration tank (11) for the stock from which air is removed by means of the vacuum produced in the deaeration tank, and that there is a duct (a5) for an overflow from the deaeration tank (11) back to the wire pit (12), and that wire water is passed from a wire section along a duct (b2) to the wire pit (12), and that fresh stock is passed from a duct (bi) to the wire pit (12).
7. A deaeration system according to claim 1, characterised in that there is a duct (ai) from the wire pit (12) directly to the deaeration tank (11) in which air is removed from wire water by means of vacuum, and that there is a duct (a2) from the deaeration tank (11) to the hydrocyclone unit (16) from which the stock is passed further as accept pumped by a pump (Pi) to a machine screen (15) and further to the headbox (10) of the paper machine, and that fresh stock is fed to the duct (a2) between the deaeration tank (11) and the hydrocyclone unit (16), to the suction side of a pump (P3).
PCT/FI2001/000793 2000-09-14 2001-09-12 Deaeration system for feeding stock into a headbox of a paper machine or equivalent WO2002022946A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2001287767A AU2001287767A1 (en) 2000-09-14 2001-09-12 Deaeration system for feeding stock into a headbox of a paper machine or equivalent

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI20002032 2000-09-14
FI20002032A FI110795B (en) 2000-09-14 2000-09-14 Venting arrangements for feeding pulp to the inlet box of a paper machine or equivalent

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WO2002022946A1 true WO2002022946A1 (en) 2002-03-21

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WO (1) WO2002022946A1 (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008119872A1 (en) * 2007-04-03 2008-10-09 Andritz Oy An apparatus for removing gas in connection with a paper machine or corresponding
WO2011081594A1 (en) * 2009-12-28 2011-07-07 Metso Paper Karlstad Ab A unit and method for deaeration of drainage water
WO2012056108A1 (en) * 2010-10-26 2012-05-03 Aikawa Fiber Technologies Oy Deaeration of stock in a pulp drying machine
US11015292B2 (en) * 2016-09-01 2021-05-25 Essity Hygiene And Health Aktiebolag Process and apparatus for wetlaying nonwovens

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4238208A (en) * 1977-11-24 1980-12-09 Ab Celleco Apparatus for degassing paper stock
US5268077A (en) * 1991-02-27 1993-12-07 Sulzer Esher Wyss Gmbh Apparatus and method for deaerating or degassing a paper stock suspension
DE4241770A1 (en) * 1992-12-11 1994-03-10 Escher Wyss Gmbh Paper pulp suspension air removal - uses underpressure from cleaner reject for air removal

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4238208A (en) * 1977-11-24 1980-12-09 Ab Celleco Apparatus for degassing paper stock
US5268077A (en) * 1991-02-27 1993-12-07 Sulzer Esher Wyss Gmbh Apparatus and method for deaerating or degassing a paper stock suspension
DE4241770A1 (en) * 1992-12-11 1994-03-10 Escher Wyss Gmbh Paper pulp suspension air removal - uses underpressure from cleaner reject for air removal

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008119872A1 (en) * 2007-04-03 2008-10-09 Andritz Oy An apparatus for removing gas in connection with a paper machine or corresponding
US8157966B2 (en) 2007-04-03 2012-04-17 Andritz Oy Apparatus for removing gas in connection with a paper machine or corresponding
WO2011081594A1 (en) * 2009-12-28 2011-07-07 Metso Paper Karlstad Ab A unit and method for deaeration of drainage water
CN102686796A (en) * 2009-12-28 2012-09-19 梅特索·佩珀·卡尔斯塔德公司 A unit and method for deaeration of drainage water
US8784538B2 (en) 2009-12-28 2014-07-22 Valmet Ab Unit and method for deaeration of drainage water
WO2012056108A1 (en) * 2010-10-26 2012-05-03 Aikawa Fiber Technologies Oy Deaeration of stock in a pulp drying machine
US11015292B2 (en) * 2016-09-01 2021-05-25 Essity Hygiene And Health Aktiebolag Process and apparatus for wetlaying nonwovens
US11807986B2 (en) 2016-09-01 2023-11-07 Essity Hygiene And Health Aktiebolag Process and apparatus for wetlaying nonwovens

Also Published As

Publication number Publication date
FI20002032A (en) 2002-03-15
FI110795B (en) 2003-03-31
AU2001287767A1 (en) 2002-03-26
FI20002032A0 (en) 2000-09-14

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