EP0653515A2 - Procédé pour le séchage d'une bande de papier et une section de séchage d'une machine à papier - Google Patents

Procédé pour le séchage d'une bande de papier et une section de séchage d'une machine à papier Download PDF

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Publication number
EP0653515A2
EP0653515A2 EP94850170A EP94850170A EP0653515A2 EP 0653515 A2 EP0653515 A2 EP 0653515A2 EP 94850170 A EP94850170 A EP 94850170A EP 94850170 A EP94850170 A EP 94850170A EP 0653515 A2 EP0653515 A2 EP 0653515A2
Authority
EP
European Patent Office
Prior art keywords
drying
cylinders
wire
paper web
group
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP94850170A
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German (de)
English (en)
Other versions
EP0653515A3 (fr
Inventor
Jouko Yli-Kauppila
Reima Kerttula
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.)
Valmet Paper Machinery Inc
Original Assignee
Valmet Paper Machinery 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 Valmet Paper Machinery Inc filed Critical Valmet Paper Machinery Inc
Publication of EP0653515A2 publication Critical patent/EP0653515A2/fr
Publication of EP0653515A3 publication Critical patent/EP0653515A3/fr
Withdrawn legal-status Critical Current

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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F5/00—Dryer section of machines for making continuous webs of paper
    • D21F5/02—Drying on cylinders
    • D21F5/04—Drying on cylinders on two or more drying cylinders

Definitions

  • the invention concerns a method in contact-drying of a paper web, wherein the paper web is dried by means of heated smooth-faced drying cylinders by using a number of successive so-called normal groups with single-wire draw, in which the drying cylinders are placed in the upper row and the reversing suction cylinders or corresponding reversing suction rolls in the lower row, in which method, after the press section of the paper machine, the paper web is dried initially in a number of successive groups with single-wire draw by pressing the paper web by means of the drying wire of the cylinder group against the heated faces of the drying cylinders and by, in each group with single-wire draw, passing the paper web on support of the same drying wire from one drying cylinder onto the next drying cylinder over reversing suction cylinders, and in which method, after the above drying steps, which were carried out exclusively by means of normal groups with single-wire draw, the paper web is dried immediately further by means of one single group with twin-wire draw to its ultimate dry solids content.
  • the invention concerns a dryer section of a paper machine, whose initial part is composed of a number of successive so-called normal groups with single-wire draw, in which the drying cylinders are placed in the upper row and the reversing suction cylinders or corresponding suction rolls are placed in the lower row, and between which said normal groups the paper web to be dried has closed draws over the group gaps, and which said reversing suction cylinders have been arranged to be subjected to negative pressure, at least at their drying-wire turning sectors, and in which dryer section, after the last group with single-wire draw, one single group with twin-wire draw is provided, in which there are two rows of drying cylinders, one row placed above the other.
  • twin-wire draw and/or single-wire draw is/are employed.
  • the groups of drying cylinders include two wires, which press the web, one from above and the other one from below, against the heated cylinder faces.
  • the web has free and unsupported draws, which are susceptible of fluttering, which may again cause web breaks, in particular since the web is still relatively moist and, therefore, of low strength.
  • each group of drying cylinders has one drying wire only, on whose support the web runs through the whole group so that the drying wire presses the web on the drying cylinders against the heated cylinder faces, whereas, on the reversing cylinders or rolls between the drying cylinders, the web remains at the side of the outside curve.
  • the drying cylinders are placed outside the wire loop and the reversing cylinders or rolls inside said loop.
  • An object of the present invention is also to reduce this problem, which occurs in the drying groups driven by the drying wire because of the considerable thickness of the drying wire.
  • the differences in speed mentioned above, together with a restricted drying shrinkage, have caused web breaks in the last groups when exclusively single-wire draw has been used, which problem is emphasized further if, in the groups with single-wire draw, small-diameter suction rolls proper are used that are provided with an inside suction box. In order to eliminate this problem, in some machines, it has been even necessary to open some group gaps and to lower the level of negative pressure in the suction rolls.
  • the dryer section in accordance with the invention is mainly characterized in that differences in pressure that disturb the support contact between the drying wire and the paper web on their joint runs from the drying cylinders onto the reversing suction cylinders in the groups with single-wire draw have been reduced or prevented by means of air-blow devices or equivalent, and/or that said reversing suction cylinders are reversing suction cylinders that are provided with a perforated mantle and with outside grooves subjected to a vacuum and which said cylinders have no inside suction box.
  • the transverse shrinkage of the web may be increased very little in comparison to a situation in which the web is dried by means of a dryer section exclusively consisting of groups with single-wire draw, but especially when a size press or a coating device is used after the dryer section, in the final product, in this respect, no disadvantageous difference is noticed that is unfavourable to the invention.
  • Figure 1 is a schematic side view of a dryer section in accordance with the invention that makes use of the method of the invention.
  • Figure 2 shows a closed draw between a group with single-wire draw and a group with twin-wire draw and an alternative embodiment of a single group with twin-wire draw.
  • Figure 3 shows such a final end of a dryer section in accordance with the invention in which two cylinder groups are employed that are fitted in inclined planes, in particular in view of reducing the length of the dryer section.
  • the paper web W in is brought into the dryer section from the press section (not shown) onto the drying wire 15 of the first group R1 with single-wire draw, to which wire it is fixed by the effect of the negative pressure in the suction boxes 13.
  • the dryer section includes N pieces of groups R1,R2...R N with single-wire draw, between which the web W has a closed draw.
  • All the groups R1...R N with single-wire draw are so-called normal groups, in which the, e.g., steam-heated smooth-faced drying cylinders 10 are placed in the upper horizontal row and the reversing suction cylinders 11 or equivalent suction rolls are placed in the lower horizontal row.
  • the last normal group R N the last two upper cylinders 10' and the single reversing suction cylinder 11' placed between them are placed at a level by the dimension H3 higher than in the preceding groups R1...R N-1 .
  • the dimension H3 is typically H3 ⁇ 400 mm.
  • the frame part 100 of the dryer section is illustrated quite schematically.
  • Each normal group R1...R N has a drying wire 15 of its own, which is guided by guide rolls 18.
  • the drying wires 15 press the web W to be dried on the drying cylinders 10 against their smooth heated face, and on the reversing cylinders 11 the web W remains at the side of the outside curve on the outside face of the wire 15.
  • the web W is kept reliably on support of the wire 15 against the effect of centrifugal forces by the effect of the negative pressure present in the grooved faces 12 of the reversing cylinders 11, whereby transverse shrinkage of the web W is also prevented.
  • the reversing suction cylinders 11 that are used are preferably suction cylinders 11 marketed by the applicant under the trade mark "VAC-ROLL" TM , which cylinders have no inside suction boxes, which cylinders are provided with a perforated mantle and with outside grooves that are subjected to a vacuum, and in respect with whose constructional details reference is made to the applicant's FI Patent No. 83,680 (equivalent to US Pat. No. 5,022,163 ).
  • the diameters D2 of these suction cylinders 11 are substantially larger than the diameters of normal suction rolls that are provided with an inside suction box and that are used in corresponding positions.
  • the remarkable advantage is obtained that, on the turning sectors on the reversing cylinders 11, the web W is subjected to lower centrifugal forces, whereby a more reliable transfer is achieved and/or it is possible to use a lower vacuum level in the grooved faces 12 of the reversing cylinders, compared with normal suction rolls.
  • the support contact between the web W and the drying wire 15 is also kept good on the straight runs between the drying cylinders 10 and the reversing cylinders 11, at least on the runs taking place from the drying cylinders 10 to the reversing cylinders 12, by using blow-suction boxes 17, by whose means formation of negative pressures induced by the wire 15 is prevented in the closing wedge-shaped nip spaces between the wire 15 and the cylinder 12 mantle.
  • blow-suction boxes 17 which are marketed by the applicant under the trade mark " UNO RUN BLOW BOX" TM , reference is made to the applicant's FI Patents Nos.
  • blow boxes 16 are also used in the gaps between the reversing cylinders 12, by means of which boxes said intermediate spaces are air-conditioned and evaporation from the web W is promoted.
  • the faces of the drying cylinders 10 are kept clean by the doctors 14.
  • broke removal by the force of gravity can be applied in the groups R1...R N with single-wire draw, which extend over the major part of the overall length L of the dryer section, for the groups R1...R N with single-wire draw are open towards the bottom so that the paper web WS that becomes broke can be removed without any particular arrangements onto the broke conveyor (not shown) placed in the basement space of the paper machine.
  • the web W has time to reach a certain, quite high dry solids content of k1 ⁇ 70 %...92 %, preferably k1 ⁇ 80 %...85 %, depending on the paper grade.
  • the web W is so strong that, for its further drying, it is possible to apply a group with twin-wire draw without a risk of detrimental breaks.
  • this single twin-wire group R TW there are two horizontal rows of contact-drying cylinders 20A and 20B, one row placed above the other, of which cylinders, in connection with the upper cylinders 20A, there is an upper wire 25A, which is guided by wire guide rolls 21A fitted in the gaps between the cylinders 20A and by other guide rolls 28.
  • the web W is pressed into a drying contact against the heated faces of the lower cylinders 20B by means of the lower wire 25B, which is guided by the wire guide rolls 21B fitted in the gaps between the cylinders 20B and by other guide rolls 28.
  • a draw arrangement marketed by the applicant under the trade mark "TWIN-RUN" TM is used, in which the guide rolls 21A and 21B are placed so that the drying wires 25A and 25B accompany the web from the drying cylinders 20A and 20B onto the next one so that the free draws W0 of the web W can be made shorter, as compared with free draws of full length.
  • air-blow boxes 22A,22B are used at the proximity of the wire guide rolls 21A and 21B and at the inlet side of the web W and the drying wire 25A and 25B.
  • blow boxes 22A,22B which are used in the "TWIN-RUN" TM concept and which are fitted in the gaps between the drying cylinders 20A,20B, air jets of suitable direction and blow velocity are applied to the vicinity of the runs of the drying wires 25A,25B placed at their proximity and to the vicinity of the free sectors of the wire guide rolls 21A,21B, by means of which jets the support contact between the drying wires 25A,25B and the web W is promoted, formation of detrimental differences in pressure and fluttering of the web W on the free draws W0 are prevented.
  • Said blowings can also be applied through the drying wires 25A,25B, whereby it is possible to promote the ventilation of the pocket spaces P formed in the gaps between the drying cylinders 20A,20B.
  • the last two cylinders 10' in the last normal group R N are placed in the same horizontal plane as the upper cylinders 20A in the single twin-wire group R TW , whereby it is possible to guarantee a transfer of the web W free of problems.
  • the web W is passed from the last cylinder in the last normal group R N onto the first lower cylinder 20B in the single twin-wire group R TW as an open draw W1, whose arrangement is similar to the free draws W0 of the web W in the twin-wire group R TW .
  • the length L TW of the twin-wire group R TW is about 14 % of the overall length.
  • the length of the single twin-wire group L TW is about 10...20 %, preferably 12...16 %, of the overall horizontal length L of the dryer section.
  • Fig. 2 shows an embodiment of the invention in which a closed draw W c of the web W is employed between the last normal group R N and the twin-wire group R TW , which closed draw has been achieved by passing the drying wire 15 and the web W supported on it into contact with the first upper cylinder 20A in the single twin-wire group R TW , to whose smooth face the web W adheres and is transferred, being pressed by the upper wire 25A guided by the guide roll 28a, over the first upper cylinder 20A in the group R TW .
  • Fig. 1 shows an embodiment of the invention in which a closed draw W c of the web W is employed between the last normal group R N and the twin-wire group R TW , which closed draw has been achieved by passing the drying wire 15 and the web W supported on it into contact with the first upper cylinder 20A in the single twin-wire group R TW , to whose smooth face the web W adheres and is transferred, being pressed by the upper wire 25A guided by the guide roll 28a, over the first upper cylinder
  • the guide rolls 21A and 21B placed in the gaps between the drying cylinders 20A and 20B are placed symmetrically in the centre plane passing through the centre axis of the adjacent drying cylinder, in which case the free draws W0 of the web W passing between the rows of cylinders 20A and 20B are of full length and unshortened, differing from the "TWIN-RUN" TM arrangement shown in Fig. 1.
  • This solution is also included in the scope of the present invention even though it is not in all cases equally advantageous as the shortened free gaps W0 shown in Fig. 1.
  • a drawback of the free draws W0 of full length is slightly higher tendency of fluttering of the web W, but, on the other hand, longer free gaps W0 allow more time for evaporation of water and for relaxing of the web tensions in the gaps W0 between the rows of cylinders 20A and 20B.
  • the drying cylinders 10 in the last normal group R N are placed in a plane slightly lower (dimension H4) than the upper cylinders 20A in the twin-wire group R TW .
  • the scope of the invention also includes embodiments in which the free gaps W0, described above, between the rows of cylinders 20A,20B in the single group R TW with twin-wire draw have been replaced fully or partially by fully closed draw arrangements which are in themselves known in prior art.
  • Figs. 3 and 4 reference is made to Figs. 3 and 4 in the applicant's FI Patent No. 68,279 (equivalent to US Patent 4,602,439 ), to US Patent 3,753,298, and to the paper mentioned above by Lindberg, Juppi, Eskelinen , "High Speed Dryer Section Developments for Sheet Stability", 78th Annual Meeting, Technical Section CPPA, 1992.
  • Ropeless threading can be applied in the normal groups R1...R N by means of the drying wires 15 and by means of the reversing suction cylinders 11 as well as on the straight runs of the wires placed in connection with them by means of blow boxes 17 and by means of negative pressure applied to the reversing suction cylinders 11.
  • Substantially similar arrangements can also be used in the single group R TW with twin-wire draw. If necessary, at the doctors 14 and 24, it is also possible to use blow arrangements by whose means the threading is promoted. With respect to these arrangements, reference is made to the applicant's FI Patent Application No. 904841 (equivalent to US Pat. Appl. No. 07/766,039 ).
  • the diameters D1 of the drying cylinders 10 in the normal groups R N are advantageously substantially equal to the diameters D0 of the cylinders 20A and 20B in the single twin-wire group R TW , i.e. D1 ⁇ D0.
  • said diameters D1 and D0 are chosen as D0 ⁇ D1 ⁇ 2.5 m, preferably D1 ⁇ D0 ⁇ 1.8...2.2 m.
  • the diameter D2 of the reversing suction cylinders 11 or of corresponding normal suction rolls is, as a rule, chosen in a range of D2 ⁇ 0.6...1.8 m.
  • reversing suction cylinders 11 which have no inside suction box, which are provided with perforated mantles and with outside grooves 12 that are subjected to a vacuum, and the diameter D2 of said cylinders is chosen in the range of D2 ⁇ 1.0 ... 1.8 m, preferably D2 ⁇ 1.2 ... 1.5 m.
  • Fig. 2 also shows the horizontal distance A between the cylinders in a normal group R N and the corresponding horizontal distance B in the single twin-wire group R TW , which distances are in Fig.
  • the diameter D3 of the guide rolls 18,28,21a,21b is typically in a range of D3 ⁇ 400...700 mm, depending on the width of the machine.
  • a regulation parameter that can be utilized in the invention and by whose means the symmetry of the drying of the opposite sides of the web W can be controlled is the tensions T N and T TW of the drying wires 15 and 25A,25B.
  • T N is chosen in a range of T N ⁇ 2...4 kN/m
  • T TW is chosen in a range of T TW ⁇ 4...8 kN/m.
  • the wire tensions T TWA and T TWB of the lower and upper wire 25A and 25B in the single twin-wire group R TW can also be chosen as different from each other if the symmetry of the drying of the web W should require that.
  • Such an embodiment is particularly advantageous in which the tension T TWB of the wire 25B of the lower cylinders 20B is higher than the tension T TWA of the upper wire 25A.
  • the symmetry of drying is promoted by in the single twin-wire group R TW drying the upper side of the web W to a greater extent.
  • the symmetry of drying can also be promoted by in the twin-wire group R TW using different steam pressures and cylinder-face temperatures in the upper cylinders 20A as compared with the lower cylinders 20B.
  • a higher steam pressure and cylinder-face temperature are employed than in the upper cylinders 20A, whereby, together with the difference in tension T TWB > T TWA between the wires 25A and 25B, the symmetry of the drying of the web W is promoted further by, in the single twin-wire group R TW drying the upper face of the wire W to a greater extent than the lower face, whose drying proportion was in the normal groups R 1...N , owing to the cylinders 10, higher than the drying of the upper face.
  • the above symmetry of drying can be promoted further by choosing the permeabilities of the upper wire 25A and the lower wire 25B different.
  • Fig. 3 shows such a modification of a dryer section as shown in Fig. 1 in which the last two groups RS N-1 and RS N in the single-wire groups R 1...N are particular groups of inclined alignments, in which the first three contact-drying cylinders 10S are placed in a plane T1 that is inclined downwards in the direction of running of the web W, and the next three corresponding cylinders 10S are placed in an upwards inclined plane T2.
  • the reversing cylinders in the groups RS N-1 and RS N are denoted with the reference 11S and the leading rolls with the reference 18S and the wires with the reference 15S.
  • Said inclined groups are preceded by normal single-wire groups R1...R N-3 similar to those shown in Fig.
  • the web W having closed draws between said normal single-wire groups and the inclined groups RS N-1 and RS N .
  • the inclined groups RS it is also possible to use vertical or almost vertical cylinder groups.
  • At least the lower parts of the inclined groups RS may extend to below the floor level of the paper machine hall into its basement space.
  • the scope of the invention also includes embodiments in which the overall length of the dryer section has been made shorter in respect of the groups R1...R N with single-wire draw by, in one or several groups R1...R N , fitting the drying cylinders 10 in two or more horizontal, vertical or inclined planes.

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  • Paper (AREA)
EP94850170A 1993-10-05 1994-10-04 Procédé pour le séchage d'une bande de papier et une section de séchage d'une machine à papier. Withdrawn EP0653515A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI934367 1993-10-05
FI934367A FI934367A (fi) 1993-10-05 1993-10-05 Menetelmä paperirainan kuivatuksessa sekä paperikoneen kuivatusosa

Publications (2)

Publication Number Publication Date
EP0653515A2 true EP0653515A2 (fr) 1995-05-17
EP0653515A3 EP0653515A3 (fr) 1996-02-21

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EP94850170A Withdrawn EP0653515A3 (fr) 1993-10-05 1994-10-04 Procédé pour le séchage d'une bande de papier et une section de séchage d'une machine à papier.

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EP (1) EP0653515A3 (fr)
CA (1) CA2133604A1 (fr)
FI (1) FI934367A (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0687768A3 (fr) * 1994-06-14 1998-01-07 Valmet Paper Machinery Inc. Section de séchage pour machine à papier
EP1355003A2 (fr) * 2002-04-19 2003-10-22 Voith Paper Patent GmbH Section de séchage
CN102888777A (zh) * 2012-10-23 2013-01-23 河南江河纸业股份有限公司 高速纸机干燥部

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5661911A (en) * 1994-02-17 1997-09-02 Valmet Corporation Dryer section of a paper machine
FI93875C (fi) * 1994-02-17 1995-06-12 Valmet Paper Machinery Inc Menetelmä paperirainan kuivatuksessa sekä paperikoneen kuivatusosa
FI93036C (fi) * 1994-03-29 1995-02-10 Valmet Paper Machinery Inc Menetelmä paperirainan kontaktikuivatuksessa sekä paperikoneen kuivatusosa
US5505006A (en) * 1994-09-08 1996-04-09 J.M. Voith Gmbh Device for drying a running web
FI98387C (fi) * 1995-02-01 1997-06-10 Valmet Corp Menetelmä pintakäsiteltävän paperin, etenkin hienopaperin, valmistamiseksi sekä paperikoneen kuivapää
US6126787A (en) 1995-02-01 2000-10-03 Valmet Corporation Dry end of a paper machine

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3828743A1 (de) * 1987-09-02 1989-03-23 Valmet Paper Machinery Inc Verfahren und vorrichtung in einer einsieb-trockengruppe einer papiermaschine
US4821429A (en) * 1987-11-30 1989-04-18 J. M. Voith, Gmbh Air guide box for stabilizing the run of a web, for instance a paper web
EP0332599A2 (fr) * 1988-03-09 1989-09-13 Valmet Corporation Procédé et dispositif dans la section de séchage à toile unique d'une machine à papier et un rouleau pour l'utilisation dans le procédé
US4967489A (en) * 1988-12-14 1990-11-06 Valmet Paper Machinery Inc. Multi-cylinder dryer with twin-wire draw and web transfer between the cylinder groups
DE9110134U1 (fr) * 1991-08-16 1991-09-26 J.M. Voith Gmbh, 7920 Heidenheim, De
WO1993022497A1 (fr) * 1992-04-24 1993-11-11 Beloit Technologies, Inc. Section de sechage a etage unique pour empecher le gondolage
DE9414963U1 (de) * 1994-09-16 1994-11-03 Voith Gmbh J M Trockenpartie

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3828743A1 (de) * 1987-09-02 1989-03-23 Valmet Paper Machinery Inc Verfahren und vorrichtung in einer einsieb-trockengruppe einer papiermaschine
US4821429A (en) * 1987-11-30 1989-04-18 J. M. Voith, Gmbh Air guide box for stabilizing the run of a web, for instance a paper web
EP0332599A2 (fr) * 1988-03-09 1989-09-13 Valmet Corporation Procédé et dispositif dans la section de séchage à toile unique d'une machine à papier et un rouleau pour l'utilisation dans le procédé
US4967489A (en) * 1988-12-14 1990-11-06 Valmet Paper Machinery Inc. Multi-cylinder dryer with twin-wire draw and web transfer between the cylinder groups
DE9110134U1 (fr) * 1991-08-16 1991-09-26 J.M. Voith Gmbh, 7920 Heidenheim, De
WO1993022497A1 (fr) * 1992-04-24 1993-11-11 Beloit Technologies, Inc. Section de sechage a etage unique pour empecher le gondolage
DE9414963U1 (de) * 1994-09-16 1994-11-03 Voith Gmbh J M Trockenpartie

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0687768A3 (fr) * 1994-06-14 1998-01-07 Valmet Paper Machinery Inc. Section de séchage pour machine à papier
EP1355003A2 (fr) * 2002-04-19 2003-10-22 Voith Paper Patent GmbH Section de séchage
EP1355003A3 (fr) * 2002-04-19 2004-04-14 Voith Paper Patent GmbH Section de séchage
CN102888777A (zh) * 2012-10-23 2013-01-23 河南江河纸业股份有限公司 高速纸机干燥部

Also Published As

Publication number Publication date
EP0653515A3 (fr) 1996-02-21
CA2133604A1 (fr) 1995-04-06
FI934367A0 (fi) 1993-10-05
FI934367A (fi) 1995-04-06

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