U.S. patent application number 11/614516 was filed with the patent office on 2007-07-12 for method and plant for producing a fibrous web.
Invention is credited to Ulrich Begemann, Thomas Jaschinski, Rudolf Munch, Volker Schmidt-Rohr.
Application Number | 20070158044 11/614516 |
Document ID | / |
Family ID | 37808351 |
Filed Date | 2007-07-12 |
United States Patent
Application |
20070158044 |
Kind Code |
A1 |
Jaschinski; Thomas ; et
al. |
July 12, 2007 |
METHOD AND PLANT FOR PRODUCING A FIBROUS WEB
Abstract
The present invention relates to a method and a corresponding
plant for producing a fibrous web, in particular a paper web,
paperboard web or tissue web. The formation of the fibrous web is
defined online as a controlled variable and is held at a
preselectable set-point level by way of an automatic formation
control system.
Inventors: |
Jaschinski; Thomas;
(Heidenheim, DE) ; Begemann; Ulrich; (Heidenheim,
DE) ; Schmidt-Rohr; Volker; (Heidenheim, DE) ;
Munch; Rudolf; (Konigsbronn, DE) |
Correspondence
Address: |
TAYLOR & AUST, P.C.
142 SOUTH MAIN STREET
P. O. BOX 560
AVILLA
IN
46710
US
|
Family ID: |
37808351 |
Appl. No.: |
11/614516 |
Filed: |
December 21, 2006 |
Current U.S.
Class: |
162/198 ;
162/252; 700/127 |
Current CPC
Class: |
D21G 9/0027
20130101 |
Class at
Publication: |
162/198 ;
700/127; 162/252 |
International
Class: |
D21F 11/00 20060101
D21F011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 24, 2005 |
DE |
DE102005062304.2 |
Claims
1. A method for producing a fibrous web comprising the steps of:
defining a formation of the fibrous web online as a controlled
variable; and holding said formation of the fibrous web at a
preselectable set-point level using an automatic formation control
system.
2. The method according to claim 1, wherein said formation is
defined directly.
3. The method according to claim 2, wherein said formation is
defined by at least one formation sensor.
4. The method according to claim 1, wherein said formation is
defined indirectly by at least one auxiliary variable.
5. The method according to claim 4, wherein said at least one
auxiliary variable for indirectly defining said formation comprises
a water quantity in a bar section of a forming unit, said water
quantity being measured.
6. The method according to claim 1, wherein said formation is held
at said preselectable set-point level by a corresponding change of
at least one set-point variable.
7. The method according to claim 6, further comprising changing
accordingly at least a material density in order to hold said
formation at said preselectable set-point level.
8. The method according to claim 6, further comprising changing
accordingly at least a retention in order to hold said formation at
said preselectable set-point level.
9. The method according to claim 6, further comprising changing
accordingly at least an opening cross-section of an outlet gap of a
headbox nozzle in order to hold said formation at said
preselectable set-point level.
10. The method according to claim 6, further comprising changing
accordingly at least one vacua in a region of a forming unit in
order to hold said formation at said preselectable set-point
level.
11. The method according to claim 6, further comprising changing
accordingly at least one bar pressure in a region of a forming unit
in order to hold said formation at said preselectable set-point
level.
12. The method according to claim 6, further comprising changing
accordingly at least a wrap angle, through which the fibrous web is
conveyed over a curved surface, in order to hold said formation at
said preselectable set-point level.
13. The method according to claim 12, wherein said curved surface
comprises a forming roller.
14. The method according to claim 6, further comprising changing
accordingly at least a mesh tension, with which an outer lying
dewatering mesh is conveyed over a curved path, in order to hold
said formation at said preselectable set-point level.
15. The method according to claim 14, wherein said curved path
comprises a forming roller.
16. The method according to claim 6, wherein said at least one
set-point variable includes an actuating range, said actuating
range of said at least one set-point variable is limited to a
preselectable extent.
17. The method according to claim 16, further comprising measuring
a value of at least one auxiliary variable, wherein said actuating
range is limited as a factor of a measured value of said at least
one auxiliary variable.
18. The method according to claim 17, wherein said at least one
auxiliary variable which is measured comprises a dry content of the
fibrous web downstream from a forming unit.
19. The method according to claim 17, wherein said at least one
auxiliary variable which is measured comprises a value
representative of a web take-off.
20. The method according to claim 17, wherein said at least one
auxiliary variable which is measured comprises a value
representative of a web take-off from a central roller.
21. The method according to claim 16, further comprising triggering
an alarm upon reaching at least one preselectable limit of said
actuating range of said at least one set-point variable.
22. The method according to claim 1, wherein said formation of the
fibrous web is defined at an exit of a forming unit.
23. The method according to claim 1, further comprising entering at
least one formation value defined online into a controller for
controlling said formation, wherein said formation is held at said
preselectable set-point level by said controller through
accordingly changing at least one set-point variable.
24. The method according to claim 23, further comprising entering a
value of at least one auxiliary variable into said controller in
order to limit an actuating range of at least one set-point
variable as a factor thereof.
25. The method according to claim 1, further comprising providing
at least one Proportional-Integral-Derivative controller.
26. The method according to claim 1, further comprising providing
at least one state controller.
27. The method according to claim 1, further comprising providing
at least one controller with at least one self-learning control
algorithm.
28. The method according to claim 1, further comprising at least
one soft sensor at least one of to define said formation and to
measure at least one auxiliary variable.
29. An industrial plant for producing a fibrous web, said plant
comprising an automatic formation control system for defining a
formation of the fibrous web online as a controlled variable and
holding said formation of the fibrous web at a preselectable
set-point level.
30. The industrial plant according to claim 29, further comprising
a device for directly defining said formation.
31. The industrial plant according to claim 30, wherein said device
for directly defining said formation comprises at least one
formation sensor.
32. The industrial plant according to claim 29, further comprising
a device for indirectly defining said formation by an auxiliary
variable.
33. The industrial plant according to claim 32, wherein said device
for indirectly defining said formation is configured for measuring
a water quantity in a bar section of a forming unit.
34. The industrial plant according to claim 29, wherein said
automatic formation control system is configured for accordingly
changing at least one set-point variable in order to hold said
formation at said preselectable set-point level.
35. The industrial plant according to claim 34, wherein said
automatic formation control system is configured for accordingly
changing at least a material density in order to hold said
formation at said preselectable set-point level.
36. The industrial plant according to claim 34, wherein said
automatic formation control system is configured for accordingly
changing at least a retention in order to hold said formation at
said preselectable set-point level.
37. The industrial plant according to claim 34, further comprising
a headbox nozzle including an outlet gap having an opening
cross-section, wherein said automatic formation control system is
configured for accordingly changing at least said opening
cross-section of said outlet gap of said headbox nozzle in order to
hold said formation at said preselectable set-point level.
38. The industrial plant according to claim 34, further comprising
a forming unit, wherein said automatic formation control system is
configured for accordingly changing at least one vacua in a region
of a forming unit in order to hold said formation at said
preselectable set-point level.
39. The industrial plant according to claim 34, further comprising
a forming unit, wherein said automatic formation control system is
configured for accordingly changing at least one bar pressure in a
region of said forming unit in order to hold said formation at said
preselectable set-point level.
40. The industrial plant according to claim 34, further comprising
a curved surface, wherein said automatic formation control system
is configured for accordingly changing at least a wrap angle,
through which the fibrous web is conveyed over said curved surface,
in order to hold said formation at said preselectable set-point
level.
41. The industrial plant according to claim 40, wherein said curved
surface comprises a forming roller.
42. The industrial plant according to claim 34, further comprising
an outer lying dewatering mesh which is conveyed over a curved
path, wherein said automatic formation control system is configured
for accordingly changing at least a mesh tension, with which said
outer lying dewatering mesh is conveyed over said curved path, in
order to hold said formation at said preselectable set-point
level.
43. The industrial plant according to claim 42, wherein said curved
path comprises a forming roller.
44. The industrial plant according to claim 29, wherein the plant
includes at least one set-point variable having an actuating range,
said actuating range of said at least one set-point variable being
limitable to a preselectable extent.
45. The industrial plant according to claim 44, further comprising
a device configured for measuring a value of at least one auxiliary
variable, wherein said actuating range is accordingly limitable as
a factor of a measured value of said auxiliary variable.
46. The industrial plant according to claim 45, further comprising
a forming unit, wherein said device for measuring said value of
said at least one auxiliary variable is configured for measuring a
dry content of the fibrous web downstream from said forming
unit.
47. The industrial plant according to claim 45, wherein said device
for measuring said value of said at least one auxiliary variable is
configured for measuring a value representative of a web
take-off.
48. The industrial plant according to claim 45, further comprising
a central roller, wherein said device for measuring said value of
said at least one auxiliary variable is configured for measuring a
value representative of a web take-off from said central
roller.
49. The industrial plant according to claim 29, further comprising
a device for triggering an alarm upon reaching at least one
preselectable limit of an actuating range of at least one set-point
variable.
50. The industrial plant according to claim 29, further comprising
a forming unit including an exit, wherein said formation of the
fibrous web can be defined at said exit of said forming unit.
51. The industrial plant according to claim 29, further comprising
a controller configured for controlling said formation, for
entering into said controller at least one formation value defined
online, and for accordingly changing at least one set-point
variable in order to hold said formation at said preselectable
level.
52. The industrial plant according to claim 51, wherein said
controller is configured for entering into said controller a value
of at least one auxiliary variable in order to limit an actuating
range of at least one set-point variable as a factor thereof.
53. The industrial plant according to claim 29, further comprising
at least one Proportional-Integral-Derivative controller.
54. The industrial plant according to claim 29, further comprising
at least one state controller.
55. The industrial plant according to claim 29, further comprising
at least one controller with at least one self-learning control
algorithm.
56. The industrial plant according to claim 29, further comprising
at least one soft sensor at least one of for defining said
formation and for measuring at least one auxiliary variable.
Description
FIELD OF THE INVENTION
[0001] This invention relates to a method and an industrial plant
for the production of a fibrous web, which can be in particular a
paper web, paperboard web or tissue web.
DESCRIPTION OF THE RELATED ART
[0002] The formation of a paper web or paperboard web, for example,
is a decisive quality feature that influences the further
processing of the fibrous web in many different ways. An example is
the influence exerted by the formation on the strength and
printability of the finished product.
[0003] The formation of a paper web or paperboard web, for example,
is influenced on the one hand by the raw material used and on the
other hand, to a not inconsiderable extent, by the sheet forming.
In this case the sheet forming is defined by the headbox and the
forming unit. The forming unit can be a long mesh, a hybrid former
or a modern twin wire former.
[0004] The variables which influence the formation in this process
step can be the material density, vacua in the forming unit, the
retention and the water quantity for example, as was determined
during the operation of production and test paper machines for
example.
[0005] Experience indicates that even slight changes in the
composition and properties of the fibrous material used can exert
considerable influence on the formation. Also, every change to the
gsm mass of a paper web requires readjustment of the variables
which exert an influence on the formation.
[0006] For the reasons mentioned, the formation is subject to
constant fluctuations. These formation fluctuations are
particularly pronounced in particular on products containing old
paper, which is owed to the corresponding fluctuations of the raw
material composition.
[0007] A comparison of the formation producible on average over a
long period of time on production machines with that on test
machines reveals that it is nearly always possible to produce a far
better formation on the test machines. The reason for this lies in
the experience of the operating personnel and their constant
readiness to make optimizing interventions. Hence time and again
production machines have been shown to possess considerable
potential for improvement with regard to the formation.
[0008] What is needed in the art is an improved method and an
improved plant of the type initially referred to, with which the
formation, in particular on production machines, can be stabilized
at a higher level. In this case the results are to be optimized in
terms of an improved and more uniform printability, so-called
mottling for example, higher strength, etc.
SUMMARY OF THE INVENTION
[0009] The present invention provides a method for producing a
fibrous web, in particular a paper web, paperboard web or tissue
web, with which the formation of the fibrous web is defined online
as a controlled variable and is held at a preselectable set-point
level by way of an automatic formation control system.
[0010] On a practical embodiment of the method according to the
invention, the formation is defined directly. This is done by way
of at least one formation sensor.
[0011] Alternatively or in addition, it is advantageously possible
for the formation to be defined also indirectly by way of at least
one auxiliary variable. The water quantity in the bar section of
the forming unit can be measured as the auxiliary variable for
indirectly defining the formation.
[0012] It is expedient for the formation to be held at the
preselectable set-point level by a corresponding change of one or
more set-point variables.
[0013] In this case the material density is changed accordingly in
order to hold the formation at the preselectable set-point
level.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a schematic of a first embodiment of the automatic
formation control system according to the present invention;
and
[0015] FIG. 2 is a schematic of a second embodiment of the
automatic formation control system according to the present
invention.
[0016] Corresponding reference characters indicate corresponding
parts throughout the views. The exemplifications set out herein
illustrate two embodiments of the invention, and such
exemplifications are not to be construed as limiting the scope of
the invention in any manner.
DETAILED DESCRIPTION
[0017] According to an advantageous embodiment of the inventive
method it is possible, alternatively or in addition, for at least
the material density also to be changed accordingly in order to
hold the formation at the preselectable set-point level.
[0018] It can also be an advantage, alternatively or in addition,
for at least the retention to be changed accordingly in order to
maintain a preselectable set-point level of the formation.
[0019] According to another expedient embodiment it is possible,
alternatively or in addition, for the opening cross-section of the
outlet gap of the headbox nozzle also to be changed accordingly in
order to hold the formation at the preselectable set-point
level.
[0020] Alternatively or in addition it is advantageously possible
for one or more vacua in the region of the forming unit also to be
changed accordingly in order to maintain the preselectable
set-point level of the formation.
[0021] It is also an advantage, alternatively or in addition, for
one or more bar pressures in the region of the forming unit also to
be changed accordingly in order to hold the formation at the
preselectable set-point level.
[0022] According to another advantageous embodiment of the
inventive method, provision is made, alternatively or in addition,
for at least the wrap angle, through which the fibrous web is
conveyed over a curved surface such as in particular a forming
roller, to be changed accordingly in order to hold the formation at
the preselectable set-point level.
[0023] Alternatively or in addition it is advantageous for at least
the mesh tension, with which an in particular outer lying
dewatering mesh is conveyed over a curved path, such as a forming
roller or the like, to be changed accordingly in order to hold the
formation at the preselectable set-point level.
[0024] In particular in order to at least reduce any negative
influence on other important properties of the fibrous web, which
are closely related to the formation, it is advantageous for the
actuating range of at least one set-point variable to be limited to
a preselectable extent.
[0025] For this purpose, the value of at least one auxiliary
variable can be measured and the actuating range limited as a
factor of the measured value of this auxiliary variable.
[0026] For this purpose the dry content of the fibrous web
downstream from the forming unit is measured as the auxiliary
variable. Alternatively or in addition it is expediently possible
also for a value representative of the web take-off from in
particular a central roller to be measured as the auxiliary
variable.
[0027] An alarm is triggered upon reaching at least one
preselectable limit of the actuating range of at least one
set-point variable.
[0028] It is a particular advantage for formation of the fibrous
web to be defined at the exit of the forming unit. By the formation
being defined already at the exit of the forming unit and not until
at the end of the production machine, e.g. a paper machine, the
dynamic response of the control circuit is notably increased by the
correspondingly reduced dead time.
[0029] According to a practical embodiment of the inventive method,
at least one formation value defined online is entered into a
controller for controlling the formation, and the formation is held
at the preselectable set-point level by way of the controller
through accordingly changing one or more set-point variables.
[0030] Expediently the value of at least one auxiliary variable is
entered in addition into the controller in order to limit the
actuating range of at least one set-point variable as a factor
thereof.
[0031] Advantageously at least one PID controller is used.
[0032] Alternatively or in addition to the simple control concept,
for example on the basis of at least one PID controller, the use of
at least one state controller and/or the use of at least one
controller with at least one self-learning control algorithm is
advantageously possible, which particularly with regard to the
complexity of the relationships in the formation control in
question is a great advantage.
[0033] To improve the quality of the control, at least one
so-called soft sensor is used to define the formation and/or to
measure at least one auxiliary variable. Such a soft sensor is used
as a rule to calculate non-measurable variables by way of
measurable variables.
[0034] Furthermore, an industrial plant for producing a fibrous
web, in particular a paper web, paperboard web or tissue web, is
provided having an automatic formation control system with which
the formation of the fibrous web is defined online as a controlled
variable and is held at a preselectable set-point level.
[0035] The plant has a way for directly defining the formation. In
this case it is expediently possible for these ways to include in
particular at least one formation sensor.
[0036] Alternatively or in addition it is advantageously possible
also to provide a way for indirectly defining the formation by way
of at least one auxiliary variable. In this case these ways for
indirectly defining the formation include ways for measuring the
water quantity in the bar section of the forming unit.
[0037] Expediently one or more set-point variables can be changed
by way of the automatic formation control in order to hold the
formation at the preselectable set-point level.
[0038] In this case it is advantageous for at least the material
density to be accordingly changeable by way of the automatic
formation control in order to hold the formation at the
preselectable set-point level.
[0039] Alternatively or in addition it is expedient for at least
the retention also to be accordingly changeable by way of the
automatic formation control in order to hold the formation at the
preselectable set-point level.
[0040] It is also an advantage, alternatively or in addition, in
particular for at least the opening cross-section of the outlet gap
of the headbox nozzle also to be accordingly changeable by way of
the automatic formation control in order to maintain the
preselectable set-point level.
[0041] Alternatively or in addition it is expedient for one or more
vacua in the region of the forming unit also to be accordingly
changeable by way of the automatic formation control in order to
hold the formation at the preselectable set-point level.
[0042] Alternatively or in addition it can also be an advantage for
one or more bar pressures in the region of the forming unit to be
accordingly changeable by way of the automatic formation control in
order to maintain the preselectable set-point level.
[0043] Alternatively or in addition it is possible according to
another advantageous embodiment of the inventive method for at
least the wrap angle, through which the fibrous web is conveyed
over a curved surface such as in particular a forming roller or the
like, to be accordingly changeable in order to hold the formation
at the preselectable set-point level.
[0044] Alternatively or in addition it can also be an advantage for
at least the mesh tension, with which an in particular outer lying
dewatering mesh is conveyed over a curved path, such as a forming
roller or the like, to be accordingly changeable in order to hold
the formation at the preselectable set-point level
[0045] To reduce or prevent any negative influence on other
important properties of the fibrous web, which are closely related
to the formation, the actuating range of at least one set-point
variable can be limitable to a preselectable extent.
[0046] For this purpose, provision is made for ways for measuring
the value of at least one auxiliary variable, wherein the actuating
range is accordingly limitable as a factor of the measured value of
this auxiliary variable.
[0047] The ways for measuring the value of at least one auxiliary
variable include advantageously ways for measuring the dry content
of the fibrous web downstream from the forming unit.
[0048] Alternatively or in addition it is expediently possible for
these ways for measuring the value of at least one auxiliary
variable also to include in particular ways for measuring a value
representative of the web take-off from in particular a central
roller.
[0049] The plant can include ways for triggering an alarm upon
reaching at least one preselectable limit of the actuating range of
at least one set-point variable.
[0050] To increase the dynamic response of the control circuit, the
formation of the fibrous web can be defined by ways of the ways in
question at the exit of the forming unit.
[0051] According to a practical embodiment of the inventive plant,
the latter includes a controller for controlling the formation,
into which at least one formation value defined online can be
entered, wherein one or more set-point variables are accordingly
changeable by way of the controller in order to hold the formation
at the preselectable level.
[0052] The value of at least one auxiliary variable can be entered
in addition into the controller in order to limit the actuating
range of at least one set-point variable as a factor thereof.
[0053] Expediently the plant includes at least one PID
controller.
[0054] With regard to the complexity of the relationships in a
formation control system it is also advantageous in particular for
the plant to include at least one state controller and/or at least
one controller with at least one self-learning control
algorithm.
[0055] To improve the quality of the control the plant includes
advantageously at least one soft sensor for defining the formation
and/or for measuring at least one auxiliary variable. As previously
mentioned, such a soft sensor is used to determine non-measurable
variables from measurable variables by calculation.
[0056] Formation is generally understood to mean in particular the
structure and the degree of fiber distribution in the fibrous web,
e.g. paper, measured or assessed by way of transmitted light. The
formation is generally also referred to as the "look-through" of
the fibrous web or paper.
[0057] While this invention has been described with respect to at
least one embodiment, the present invention can be further modified
within the spirit and scope of this disclosure. This application is
therefore intended to cover any variations, uses, or adaptations of
the invention using its general principles. Further, this
application is intended to cover such departures from the present
disclosure as come within known or customary practice in the art to
which this invention pertains and which fall within the limits of
the appended claims.
LIST OF REFERENCE CHARACTERS
[0058] Automatic formation control system 10
[0059] Forming unit 12
[0060] Fibrous web 14
[0061] Headbox nozzle with outlet gap 16
[0062] Dewatering mesh 18
[0063] Forming mesh 20
[0064] Forming roller 22
[0065] Central roller 24
[0066] Controller 26
[0067] Sensor/device 28
[0068] Sensor/device 30
[0069] Suction box 32
[0070] Alarm 34
* * * * *