CA1131440A - Method for drying moist webs of paper or cardboard - Google Patents
Method for drying moist webs of paper or cardboardInfo
- Publication number
- CA1131440A CA1131440A CA343,497A CA343497A CA1131440A CA 1131440 A CA1131440 A CA 1131440A CA 343497 A CA343497 A CA 343497A CA 1131440 A CA1131440 A CA 1131440A
- Authority
- CA
- Canada
- Prior art keywords
- drying
- moisture content
- paper
- frequency
- dryer
- 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
- D21F5/00—Dryer section of machines for making continuous webs of paper
-
- 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
- D21F5/048—Drying on cylinders on two or more drying cylinders in combination with other heating means
Landscapes
- Drying Of Solid Materials (AREA)
- Paper (AREA)
Abstract
ABSTRACT OF THE INVENTION
In a method for drying moist webs of paper or cardboard, the moisture profile is optimally equalized by first drying the paper web to a moisture content of 10 to 20% with conventional cylinder drying machines.
Subsequently, capacitive high-frequency drying is performed to a moisture content of about 6 to 10%. Drying to the desired final moisture content of, for example, 4% is carried out with a cylinder dryer. The limits of use of the high-frequency dryer are given, among other things, by the cost of high-frequency energy and by the danger of breakdowns.
In a method for drying moist webs of paper or cardboard, the moisture profile is optimally equalized by first drying the paper web to a moisture content of 10 to 20% with conventional cylinder drying machines.
Subsequently, capacitive high-frequency drying is performed to a moisture content of about 6 to 10%. Drying to the desired final moisture content of, for example, 4% is carried out with a cylinder dryer. The limits of use of the high-frequency dryer are given, among other things, by the cost of high-frequency energy and by the danger of breakdowns.
Description
BACKGROUND OF THE INVENTION
This invention relates to a method for drying moist webs of paper or cardboard, especially those which are to be coated subsequently, to a moisture content of 2 to 9% by combined capacitive high-frequency and cylin-der drying.
At present, capacitive high-frequency dryers are used to advantage, following the conventional cylinder dryers of paper-making machines, for dry-ing webs of paper. By the use of these capacitive dryers, great economy and a very high degree of uniformity can be achieved at the same time.
If such a high-frequency dryer is followed by additional drying cylinders, the moister paper surface caused by the high-frequency heating leads to a distinctly effective after-drying by the drying cylinders.
It is an object of the present invention to provide a method for coordinating the individual drying cycles by which, in the case of paper and car(lboard, optimal equalization of the moisture profile can be achieved.
SUMMARY OF THE INVENTION
According to the present invention, the above problem is solved by the provision that the web is first dried, by means of cylinder drying, to a n~oisture content of 10 to 20%. The web is then dried, with high-frequency, to ~n a moisture content of about 6 to 10%. Subsequently, by means of cylinder dry-ing, the web is dried to the desired final moisture content of between 2 and 8~. Thus, each dryer is used in the range in which it produces its optimum effect with respect to equalizing the moisture profile and with respect to necessary investment cost.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a block diagram of the design of a drying facility for paper according to the teachings of the invention; and ,: , ~':, . `'-, :
., , , : , , :
~13~440 Figure 2 is a chart showing the disturbance deviation control in percent for cylinder and high-frequency dryers as a function of the desired final moisture content of the paper in percent.
DETAILED DESCRIPTION OF THE INVENTION
. . _ In Figure 1, a web of paper 1 which comes, moving at constant speeds in the direction of arrow 2, from a paper-making machine, not shown~
~irst passes through a conventional s~eam-operated cylinder dryer 3. Dryer 3 may havc, for example, 60 drying cylinders and pre-dries the paper to a mois-turc content of about 15%. This is followed by a capacitive high-frequency l~ dryer ~, in wllich the web is dried to a moisture content of about 7%. The remaining drying, to about 4% residual moisture content, is then performed in a cylinder dryer 5 having, for instance, eight drying cylinders.
The capacities of the individual drying devices are regulated here hy a control device 6, for instance, a process computer, according to measured ~at~ ~ppli~d by measuring devices known in the art and not shown.
In Figure 2, the abscissa gives the humidity UA of a paper web 1 ~t th~ ~nd of a drying process and the ordinate gives the attainable mean ~vi~tion UA of the moisture content from the value UA. Curve I applies to a ~ylind~r dryer and curve II to a capacitive high-frequency dryer, the elec-trod~ voltage bein~ considered as constant. The curves, furthermore relate to thc case whcre, due to a change in the area weight of the web, a distur-~nc~ o~ about 2.5~ occurs at the entrance of the drying device.
As is evident from curve I, a mean deviation of 1% is attainable with the cylinder dryer for a desired exit moisture content UA of 15%, but a ~ean deviation of 0.25% is attainable for a desired exit moisture content of, s.~y, 3%~
As is evident, curve II for the high-frequency dryer is subs~an-ti~lly lower, except in the range of 1 to 3%; i.e., the high-frequency dryer - .. ,. .. - ;, , : . , :: : ;, . . . .
i4'~
provides much better equalization for a given disturbance at the input.
As can further be seen from the curve, however, the difference below UA 6% is not so large as to make the use of the relatively expensive high-frequency energy worthwhile. On the other hand, above a desired final moisture content of 10%, the share of the moisture to be evaporated with high frequency, i.e., the power N (dashed curve), increases. Limits are thus set for the capacitive high-frequency dryer in this direction, both for invest-ment reasons and by reason of increasing danger of breakdowns.
For the moisture content that can be attained with the high-fre-quency dryer is it therefore advantageous for the values to be in the range marked B. Drying to values in the ranges marked A and C, on the other hand, is advantageously performed by cylinder dryers. The boundaries between the individual regions are naturally somewhat fluid.
Overall, the following ranges of operating moisture content valuesare therefore preferably obtained with the individual drying processes: Pre-drying to 10-20% with a cylinder dryer; subsequent capacitive high-frequency drying to 6-10%; and, if desired, a final drying operation by means of a cylinder dryer to a final moisture content between ~ and 8~
:~;
.
,.: :: . ..... . . : . ........ .,.. .. : .. .,, . : .
!. , . , ' , ' . ' ' i' '.' ' ' ' . . ' : . ' .
This invention relates to a method for drying moist webs of paper or cardboard, especially those which are to be coated subsequently, to a moisture content of 2 to 9% by combined capacitive high-frequency and cylin-der drying.
At present, capacitive high-frequency dryers are used to advantage, following the conventional cylinder dryers of paper-making machines, for dry-ing webs of paper. By the use of these capacitive dryers, great economy and a very high degree of uniformity can be achieved at the same time.
If such a high-frequency dryer is followed by additional drying cylinders, the moister paper surface caused by the high-frequency heating leads to a distinctly effective after-drying by the drying cylinders.
It is an object of the present invention to provide a method for coordinating the individual drying cycles by which, in the case of paper and car(lboard, optimal equalization of the moisture profile can be achieved.
SUMMARY OF THE INVENTION
According to the present invention, the above problem is solved by the provision that the web is first dried, by means of cylinder drying, to a n~oisture content of 10 to 20%. The web is then dried, with high-frequency, to ~n a moisture content of about 6 to 10%. Subsequently, by means of cylinder dry-ing, the web is dried to the desired final moisture content of between 2 and 8~. Thus, each dryer is used in the range in which it produces its optimum effect with respect to equalizing the moisture profile and with respect to necessary investment cost.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a block diagram of the design of a drying facility for paper according to the teachings of the invention; and ,: , ~':, . `'-, :
., , , : , , :
~13~440 Figure 2 is a chart showing the disturbance deviation control in percent for cylinder and high-frequency dryers as a function of the desired final moisture content of the paper in percent.
DETAILED DESCRIPTION OF THE INVENTION
. . _ In Figure 1, a web of paper 1 which comes, moving at constant speeds in the direction of arrow 2, from a paper-making machine, not shown~
~irst passes through a conventional s~eam-operated cylinder dryer 3. Dryer 3 may havc, for example, 60 drying cylinders and pre-dries the paper to a mois-turc content of about 15%. This is followed by a capacitive high-frequency l~ dryer ~, in wllich the web is dried to a moisture content of about 7%. The remaining drying, to about 4% residual moisture content, is then performed in a cylinder dryer 5 having, for instance, eight drying cylinders.
The capacities of the individual drying devices are regulated here hy a control device 6, for instance, a process computer, according to measured ~at~ ~ppli~d by measuring devices known in the art and not shown.
In Figure 2, the abscissa gives the humidity UA of a paper web 1 ~t th~ ~nd of a drying process and the ordinate gives the attainable mean ~vi~tion UA of the moisture content from the value UA. Curve I applies to a ~ylind~r dryer and curve II to a capacitive high-frequency dryer, the elec-trod~ voltage bein~ considered as constant. The curves, furthermore relate to thc case whcre, due to a change in the area weight of the web, a distur-~nc~ o~ about 2.5~ occurs at the entrance of the drying device.
As is evident from curve I, a mean deviation of 1% is attainable with the cylinder dryer for a desired exit moisture content UA of 15%, but a ~ean deviation of 0.25% is attainable for a desired exit moisture content of, s.~y, 3%~
As is evident, curve II for the high-frequency dryer is subs~an-ti~lly lower, except in the range of 1 to 3%; i.e., the high-frequency dryer - .. ,. .. - ;, , : . , :: : ;, . . . .
i4'~
provides much better equalization for a given disturbance at the input.
As can further be seen from the curve, however, the difference below UA 6% is not so large as to make the use of the relatively expensive high-frequency energy worthwhile. On the other hand, above a desired final moisture content of 10%, the share of the moisture to be evaporated with high frequency, i.e., the power N (dashed curve), increases. Limits are thus set for the capacitive high-frequency dryer in this direction, both for invest-ment reasons and by reason of increasing danger of breakdowns.
For the moisture content that can be attained with the high-fre-quency dryer is it therefore advantageous for the values to be in the range marked B. Drying to values in the ranges marked A and C, on the other hand, is advantageously performed by cylinder dryers. The boundaries between the individual regions are naturally somewhat fluid.
Overall, the following ranges of operating moisture content valuesare therefore preferably obtained with the individual drying processes: Pre-drying to 10-20% with a cylinder dryer; subsequent capacitive high-frequency drying to 6-10%; and, if desired, a final drying operation by means of a cylinder dryer to a final moisture content between ~ and 8~
:~;
.
,.: :: . ..... . . : . ........ .,.. .. : .. .,, . : .
!. , . , ' , ' . ' ' i' '.' ' ' ' . . ' : . ' .
Claims
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a method for drying moist webs of paper or cardboard, es-pecially webs which are to be subsequently coated, to a moisture content of 2 to 8% by combined capacitive high-frequency and cylinder drying, the im-provement comprising the steps of first drying the web, by means of a cyl-inder dryer, to a moisture content of 10 to 20%, then drying the web, with high-frequency, to a moisture content of about 6 to 10%, and) subsequently, drying the web, by means of a cylinder dryer, to the desired final moisture content of between 2 and 8%.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP2901332.9 | 1979-01-15 | ||
| DE2901332A DE2901332C2 (en) | 1979-01-15 | 1979-01-15 | Process for drying damp webs made of paper or cardboard |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1131440A true CA1131440A (en) | 1982-09-14 |
Family
ID=6060588
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA343,497A Expired CA1131440A (en) | 1979-01-15 | 1980-01-11 | Method for drying moist webs of paper or cardboard |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0013400B1 (en) |
| JP (1) | JPS5598994A (en) |
| AT (1) | ATE1392T1 (en) |
| CA (1) | CA1131440A (en) |
| DE (2) | DE2901332C2 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63126990A (en) * | 1986-11-17 | 1988-05-30 | 三菱重工業株式会社 | Drying apparatus |
| JPH07194205A (en) * | 1995-01-19 | 1995-08-01 | Iseki & Co Ltd | Hydraulic lifting-controlling device for tractor |
| JP2707238B2 (en) * | 1996-04-20 | 1998-01-28 | セイレイ工業株式会社 | Work machine lifting control |
| FI101986B1 (en) * | 1996-12-10 | 1998-09-30 | Valmet Corp | Method and apparatus for drying a fibrous web |
| DE102008062320B3 (en) * | 2008-12-15 | 2010-04-15 | Siemens Aktiengesellschaft | Drying chamber for the dielectric drying of a material, in particular a paper web |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE697509C (en) * | 1936-06-11 | 1940-10-16 | Siemens Schuckertwerke Akt Ges | Drying device for paper webs on paper machines |
-
1979
- 1979-01-15 DE DE2901332A patent/DE2901332C2/en not_active Expired
- 1979-12-20 DE DE7979105294T patent/DE2963459D1/en not_active Expired
- 1979-12-20 AT AT79105294T patent/ATE1392T1/en active
- 1979-12-20 EP EP79105294A patent/EP0013400B1/en not_active Expired
-
1980
- 1980-01-11 CA CA343,497A patent/CA1131440A/en not_active Expired
- 1980-01-16 JP JP345480A patent/JPS5598994A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| DE2901332A1 (en) | 1980-07-17 |
| EP0013400A1 (en) | 1980-07-23 |
| JPS5598994A (en) | 1980-07-28 |
| EP0013400B1 (en) | 1982-07-28 |
| ATE1392T1 (en) | 1982-08-15 |
| DE2901332C2 (en) | 1981-10-15 |
| DE2963459D1 (en) | 1982-09-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |