CA1148735A - Press-drying a cellulosic web - Google Patents
Press-drying a cellulosic webInfo
- Publication number
- CA1148735A CA1148735A CA000352122A CA352122A CA1148735A CA 1148735 A CA1148735 A CA 1148735A CA 000352122 A CA000352122 A CA 000352122A CA 352122 A CA352122 A CA 352122A CA 1148735 A CA1148735 A CA 1148735A
- Authority
- CA
- Canada
- Prior art keywords
- web
- drying
- drying cylinders
- pressure
- nips
- 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.)
- Expired
Links
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
- D21F3/00—Press section of machines for making continuous webs of paper
- D21F3/02—Wet presses
- D21F3/0281—Wet presses in combination with a dryer roll
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
- D21F11/00—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
Landscapes
- Paper (AREA)
Abstract
Abstract A sheet of paper or paperboard is made by wet-forming a web of cellulosic fibrous material, increasing the solids content of the web to 40-70% by weight, and passing the resulting web through a plurality of pressure nips at a temperature of 115-205°C and a pressure of 8.5-180 kg per linear cm.
Description
~1~8735 The present invention concerns the drying of a wet-laid web of cellulosic fibrous stock in the manufacture of paper or paperkoard.
In the conventional wet-forming process for the manufacture of paper the largest single consumption of energy lies in the drying of the wet-formed web.
Typically, the drying is achieved by passing the wet web over a large number of drying cylinders which are usually steam heated. mis drying section of the paper-making machine typically extends over several scores of metres. In this, the conventional process, the rate of removal of water from the web during the drying process is of the order of 14 kg per square metre of effective drying surface per hour. Such a drying rate is expensive and inefficient in terms of energy consumption, utilization of space, and rate of production of the final sheet.
me method of the invention may generally be defined as comprising the following steps:
(a) wet-forming a web of fibrous cellulosic material, (b) partially dewatering said web, (c) advancing the partially dewatered web through a succession of pressure nips provided by a plurality of heated drying cylinders and sets of pressure rollers spaced respectively around said drying cylinders, and (d) maintaining said web in contact with said drying cylinders during travel of said web between the pressure nips associated with each respective drying cylinder by a ccmmon permeable backing band advanced through said nips and about said drying cylinders together with said web.
. ~ ,, `'`~ " ' -' ~ ` "
' ' : ' ~8735 The temperature of the or each heated cylinder is preferably at least 115 C and may extend to 205C. The pressure exerted by each nip is preferably 8.5 - 72 kg/linear cm (Klc) but may extend to 180 Klc.
The method of the invention enables a drying rate of at least 73 kg per square metre of effective drying surface per hour to be attained, and provides a greater overall reduction in the energy requirements for drying the web and inthe space required for drying than is provided for in present paper making machines.
The invention will now be described by way of example with reference to the accompanying diagrammatic drawings in which Figures 1-4 are side views offour alternative forms of machines for drying wet-laid sheets of cellulosic fibrous materials~
Referring to Figure 1, a wet-laid web 10 of cellulosic fibres is made in the forming section of a multi-former board machine in a known fashion, and is subsequently dewatered to a solids content of about 35% by weight. The forming section together with the subsequent partial dewatering is indicated diagrammatically by box 11. The partial dewatering may be achieved for example by known primary presses. The partially dewatered web is then passed through a nip between two press rolls 12, 13 at ambient temperature and a pressure of 53.5 Klc. This nip increases the solids content of the web to about 40~ by weight. The web is now passed successively round steam-heated cylinders
In the conventional wet-forming process for the manufacture of paper the largest single consumption of energy lies in the drying of the wet-formed web.
Typically, the drying is achieved by passing the wet web over a large number of drying cylinders which are usually steam heated. mis drying section of the paper-making machine typically extends over several scores of metres. In this, the conventional process, the rate of removal of water from the web during the drying process is of the order of 14 kg per square metre of effective drying surface per hour. Such a drying rate is expensive and inefficient in terms of energy consumption, utilization of space, and rate of production of the final sheet.
me method of the invention may generally be defined as comprising the following steps:
(a) wet-forming a web of fibrous cellulosic material, (b) partially dewatering said web, (c) advancing the partially dewatered web through a succession of pressure nips provided by a plurality of heated drying cylinders and sets of pressure rollers spaced respectively around said drying cylinders, and (d) maintaining said web in contact with said drying cylinders during travel of said web between the pressure nips associated with each respective drying cylinder by a ccmmon permeable backing band advanced through said nips and about said drying cylinders together with said web.
. ~ ,, `'`~ " ' -' ~ ` "
' ' : ' ~8735 The temperature of the or each heated cylinder is preferably at least 115 C and may extend to 205C. The pressure exerted by each nip is preferably 8.5 - 72 kg/linear cm (Klc) but may extend to 180 Klc.
The method of the invention enables a drying rate of at least 73 kg per square metre of effective drying surface per hour to be attained, and provides a greater overall reduction in the energy requirements for drying the web and inthe space required for drying than is provided for in present paper making machines.
The invention will now be described by way of example with reference to the accompanying diagrammatic drawings in which Figures 1-4 are side views offour alternative forms of machines for drying wet-laid sheets of cellulosic fibrous materials~
Referring to Figure 1, a wet-laid web 10 of cellulosic fibres is made in the forming section of a multi-former board machine in a known fashion, and is subsequently dewatered to a solids content of about 35% by weight. The forming section together with the subsequent partial dewatering is indicated diagrammatically by box 11. The partial dewatering may be achieved for example by known primary presses. The partially dewatered web is then passed through a nip between two press rolls 12, 13 at ambient temperature and a pressure of 53.5 Klc. This nip increases the solids content of the web to about 40~ by weight. The web is now passed successively round steam-heated cylinders
2 -
- 3 -11fl~8735 ~ 19 whose ~urface temperature3 increa~e from 38 C at cylinder 15 to 120C
at cylinder 19. On leaving cylinder 19 the web has a solids content of about 50% by weight.
The web is now passed round a 3 metre diameter drying cylinder 20 heated by steam at 2.1. kg/sq. cm. pressure giving a surface temperature of about 115C.
Spaced around the cylinder 20 are five nip rolls 21 each applying a nip pressure of 35 Elc. The nip rolls 21 also provide guides for a continuous permeable backing band 22 which passes through the nips between rolls 21 and the cylinder 20. ~he web 10 passes through these nips spaced round the cylinder 20 and, while it is in contact with the cylinder 20 at the nips and between the nips, is backed by the backing band 22 which thus maintains the web in close contact with the cylinder 20 between the nips.
'.
On leaving the final nip the web 10 is substantially completely dewatered, having a isture content of about 10% by weight, and passes to cslendering snd smoothing sections (not shown).
.
In Figure 2 there is shown an alternative configuration of drying cylinders 15 - 19, heated cylinder 20, nip rolls 21, and backing band 22 as in Figure 1 exoept that on leaving the final nip roll 21 the web 10 i9 passed round a second heated cylinder 201 having nip rolls 211 and a backing band 221 similar to those in Figure 1. This configuration can be useful if it is desired to apply a slower rate of drying to the web 10. In this case it will be expected that the nip pressures and temperatures with reference to Figure 2 will be lower than those with reference to Figure 1.
In Figure ~, the wet-laid web 10, containing about 40 - 70%, typically 50%
solids and which may have already passed round the drying cylinderQ 15 - 19 !
of Figure 1, passes through a gerieg of single heated pressure nips each defined by a steam-heated cylinder 30 and a nip roll ~1. The nip pressures .._. .
, ~ .
" ~ ` ' ' ` ' - ` `
~' :
:
~8735 ~ temperatures are typically similar to tho~e described with reference to Figure 1, but may be varied in accordance with individual web requirements and the number of nips usedO The advantage of this particular configuration i~ that the web i8 unbacked (i.e. unsupported) and open on both sides to the atmosphere between succe~sive cylinders 30. ~ith this system there is less chance of ply delamination taking place, and further evaporation of moisture from the web is encouraged.
In Figure 4 there is shown a config~ration of cylinders and nip rolls which combines features of Figure 1 and Figure 3. The web 10, initially containing 40 - 70%, typically 50% solids, is fed to a series of heated cylinders 40 each of which is provided with two nip rolls 41. Permeable backing bands 42 pass only through the nips and round that portion of each cylinder defined between the nips. Hence, the web 10 is supported on each cylinder 40 between the nip rolls 41 by the backing band but is unsupported in its travel between successivecylinders 40. Nip pressures and temperatures are typically similar to those described with reference to ~igure 1 but can be varied in accordance with individual web requirements. The length of the "free run" between successive cylinders may be two metres or more in order to allow evaporation to take place.
In any of the above embodiments the temperature of any heated cylinder 20, 201, 30 or 40 can be varied between 115C and 205 C (or even higher) and nip pressures can be varied between 8.5 - 180 Klc, according to individual web requirements.
, The above embodied configurations of cylinders, nip rolls and backing bands are but a few of many configurations that are possible within the scope of this invention.
,'' ~
It is found by this invention th&t the overall rate of water removal from the _ . .
,,,, , ~
.
' ~er effective unit area of drier surfaee per unit time ean be improved by at least four times compared with the conventional drying methods. Drying rates of at least 73 kg/sq. metre effective drying surface/hour can be expected.
Webs made aeeording to this invention are expeeted to have characteristie physieal properties hitherto either unattainable or attainable only with difficulty by known wet-forming techniques. For instanee the web may be expeeted to have very good eross-maehine stiffness; inter-ply bonding ean be improved, and web strengths inereased. At the same time, some of the above eonfigurations ean produce improved surface smoothness.
, :
,, ~ ' '
at cylinder 19. On leaving cylinder 19 the web has a solids content of about 50% by weight.
The web is now passed round a 3 metre diameter drying cylinder 20 heated by steam at 2.1. kg/sq. cm. pressure giving a surface temperature of about 115C.
Spaced around the cylinder 20 are five nip rolls 21 each applying a nip pressure of 35 Elc. The nip rolls 21 also provide guides for a continuous permeable backing band 22 which passes through the nips between rolls 21 and the cylinder 20. ~he web 10 passes through these nips spaced round the cylinder 20 and, while it is in contact with the cylinder 20 at the nips and between the nips, is backed by the backing band 22 which thus maintains the web in close contact with the cylinder 20 between the nips.
'.
On leaving the final nip the web 10 is substantially completely dewatered, having a isture content of about 10% by weight, and passes to cslendering snd smoothing sections (not shown).
.
In Figure 2 there is shown an alternative configuration of drying cylinders 15 - 19, heated cylinder 20, nip rolls 21, and backing band 22 as in Figure 1 exoept that on leaving the final nip roll 21 the web 10 i9 passed round a second heated cylinder 201 having nip rolls 211 and a backing band 221 similar to those in Figure 1. This configuration can be useful if it is desired to apply a slower rate of drying to the web 10. In this case it will be expected that the nip pressures and temperatures with reference to Figure 2 will be lower than those with reference to Figure 1.
In Figure ~, the wet-laid web 10, containing about 40 - 70%, typically 50%
solids and which may have already passed round the drying cylinderQ 15 - 19 !
of Figure 1, passes through a gerieg of single heated pressure nips each defined by a steam-heated cylinder 30 and a nip roll ~1. The nip pressures .._. .
, ~ .
" ~ ` ' ' ` ' - ` `
~' :
:
~8735 ~ temperatures are typically similar to tho~e described with reference to Figure 1, but may be varied in accordance with individual web requirements and the number of nips usedO The advantage of this particular configuration i~ that the web i8 unbacked (i.e. unsupported) and open on both sides to the atmosphere between succe~sive cylinders 30. ~ith this system there is less chance of ply delamination taking place, and further evaporation of moisture from the web is encouraged.
In Figure 4 there is shown a config~ration of cylinders and nip rolls which combines features of Figure 1 and Figure 3. The web 10, initially containing 40 - 70%, typically 50% solids, is fed to a series of heated cylinders 40 each of which is provided with two nip rolls 41. Permeable backing bands 42 pass only through the nips and round that portion of each cylinder defined between the nips. Hence, the web 10 is supported on each cylinder 40 between the nip rolls 41 by the backing band but is unsupported in its travel between successivecylinders 40. Nip pressures and temperatures are typically similar to those described with reference to ~igure 1 but can be varied in accordance with individual web requirements. The length of the "free run" between successive cylinders may be two metres or more in order to allow evaporation to take place.
In any of the above embodiments the temperature of any heated cylinder 20, 201, 30 or 40 can be varied between 115C and 205 C (or even higher) and nip pressures can be varied between 8.5 - 180 Klc, according to individual web requirements.
, The above embodied configurations of cylinders, nip rolls and backing bands are but a few of many configurations that are possible within the scope of this invention.
,'' ~
It is found by this invention th&t the overall rate of water removal from the _ . .
,,,, , ~
.
' ~er effective unit area of drier surfaee per unit time ean be improved by at least four times compared with the conventional drying methods. Drying rates of at least 73 kg/sq. metre effective drying surface/hour can be expected.
Webs made aeeording to this invention are expeeted to have characteristie physieal properties hitherto either unattainable or attainable only with difficulty by known wet-forming techniques. For instanee the web may be expeeted to have very good eross-maehine stiffness; inter-ply bonding ean be improved, and web strengths inereased. At the same time, some of the above eonfigurations ean produce improved surface smoothness.
, :
,, ~ ' '
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:-
1. A method of manufacturing paper or paperboard comprising the steps of:-a) wet-forming a web of fibrous cellulosic material, b) partially dewatering said web, c) advancing the partially dewatered web through a succession of pressure nips provided by a plurality of heated drying cylinders and sets of pressure rollers spaced respectively around said drying cylinders, and d) maintaining said web in contact with said drying cylinders during travel of said web between the pressure nips associated with each respective drying cylinder by a common permeable backing band advanced through said nips and about said drying cylinders together with said web.
2. A method as claimed in claim 1, wherein said plurality of heated drying cylinders are disposed in a row and contact with said web by said drying cylinders is on one side only of said web.
3. A method as claimed in claim 2, including the step of advancing said web about at least one further heated drying cylinder during travel of said web between successive ones of said first-mentioned drying cylinders.
4. A method as claimed in claim 3, including the steps of advancing said web through a further plurality of pressure nips provided between a plurality of said further heated drying cylinders and sets of pressure rollers spaced respectively around said further drying cylinders, and holding said web in contact with said further drying cylinders during travel thereof between the pressure nips associated with each respective further drying cylinder by a further common permeable backing band advanced through said nips and about said further cylinders together with said web.
5. A method as claimed in claim 1, 2 or 3, including the step of advancing said web from one of said drying cylinders to a successive drying cylinder in an unsupported condition 80 as to permit moisture to evaporate therefrom.
6. A method according to claim 1, 2 or 4, wherein the temperature of each pressure nip is in the range of 115-205°C and the linear pressure applied by each nip is in the range from 8.5-180 kg/cm.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7917522A GB2052586B (en) | 1979-05-19 | 1979-05-19 | Drying paper |
| GB7917522 | 1979-05-19 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1148735A true CA1148735A (en) | 1983-06-28 |
Family
ID=10505294
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000352122A Expired CA1148735A (en) | 1979-05-19 | 1980-05-16 | Press-drying a cellulosic web |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS5626092A (en) |
| CA (1) | CA1148735A (en) |
| DE (1) | DE3017446A1 (en) |
| FI (1) | FI801533A (en) |
| GB (1) | GB2052586B (en) |
| SE (1) | SE8003675L (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FI812060L (en) * | 1980-07-02 | 1982-01-03 | Black Clawson Int | FOER REFRIGERATION FOER FRAMSTAELLNING AV PAPPER OCH KARTONG |
| BR8303858A (en) * | 1982-07-22 | 1984-02-28 | Wiggins Teape Group Ltd | PROCESS FOR DRYING AND CONSOLIDATING A PAPER MANUFACTURING SHEET |
| JPS5930987A (en) * | 1982-07-22 | 1984-02-18 | ザ・ウイギンズ・テイ−プ・グル−プ・リミテツド | Porous endless belt |
| JPH0826519B2 (en) * | 1987-03-24 | 1996-03-13 | 三菱重工業株式会社 | Dryer |
| JPH03504399A (en) * | 1988-05-20 | 1991-09-26 | ヨット エム フォイト ゲーエムベーハー | Method of pressing moving wet strips, especially webs |
| ES2011381A6 (en) * | 1988-08-17 | 1990-01-01 | Garcia Pastor Daniel | Mechanical drying process applicable to papermaking. |
| FI85733C (en) * | 1989-05-02 | 1992-05-25 | Valmet Paper Machinery Inc | KOMBINATION AV PRESSPARTIET OCH BEGYNNELSEDELEN AV TORKNINGSPARTIET I EN PAPPERSMASKIN. |
| CA2062983C (en) * | 1989-07-20 | 1995-06-20 | Ivan I. Pikulik | Method and apparatus for manufacture of smooth and glossy papers |
| FI89524C (en) * | 1992-05-15 | 1993-10-11 | Yhtyneet Paperitehtaat Oy | Procedure for treating a paper web in the drying section of a paper machine |
| CN104120617B (en) * | 2014-07-18 | 2017-01-18 | 宏祥新材料股份有限公司 | Non-woven fabric wet process net forming technology |
| CN114294927B (en) * | 2021-11-28 | 2024-02-20 | 苏珠弟 | Dewatering device is used in corrugated paper production |
-
1979
- 1979-05-19 GB GB7917522A patent/GB2052586B/en not_active Expired
-
1980
- 1980-05-07 DE DE19803017446 patent/DE3017446A1/en not_active Ceased
- 1980-05-12 FI FI801533A patent/FI801533A/en not_active Application Discontinuation
- 1980-05-14 JP JP6384080A patent/JPS5626092A/en active Pending
- 1980-05-16 CA CA000352122A patent/CA1148735A/en not_active Expired
- 1980-05-16 SE SE8003675A patent/SE8003675L/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| GB2052586B (en) | 1984-03-14 |
| JPS5626092A (en) | 1981-03-13 |
| GB2052586A (en) | 1981-01-28 |
| SE8003675L (en) | 1980-11-20 |
| FI801533A (en) | 1980-11-20 |
| DE3017446A1 (en) | 1980-11-27 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |