U.S. patent application number 14/432242 was filed with the patent office on 2015-10-15 for method for controlling the formation of a fiber web of a fiber or paper producing process.
The applicant listed for this patent is VOITH PATENT GMBH. Invention is credited to Jens Haag, Oliver Kaufmann.
Application Number | 20150292158 14/432242 |
Document ID | / |
Family ID | 49232280 |
Filed Date | 2015-10-15 |
United States Patent
Application |
20150292158 |
Kind Code |
A1 |
Kaufmann; Oliver ; et
al. |
October 15, 2015 |
METHOD FOR CONTROLLING THE FORMATION OF A FIBER WEB OF A FIBER OR
PAPER PRODUCING PROCESS
Abstract
A method for controlling the formation of a fiber web of a fiber
or paper producing process includes a plurality of successive
individual method steps in which controllable chemical and/or
physical sequences or process steps are carried out in dependence
on measured values. The materials required for the formation of the
fiber web are treated, combined, and/or dewatered in the sequences
or process steps. At least some of the measured values are detected
inline and directly or indirectly used in order to control the
formation. At least the manipulated variables, which influence the
formation in a relevant manner, of the individual sequences or
processes are formed dependent on definable secondary conditions
during the entire process.
Inventors: |
Kaufmann; Oliver; (Nattheim,
DE) ; Haag; Jens; (Heidenheim, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
VOITH PATENT GMBH |
Heidenheim |
|
DE |
|
|
Family ID: |
49232280 |
Appl. No.: |
14/432242 |
Filed: |
September 18, 2012 |
PCT Filed: |
September 18, 2012 |
PCT NO: |
PCT/EP2013/069370 |
371 Date: |
March 30, 2015 |
Current U.S.
Class: |
162/198 |
Current CPC
Class: |
D21F 1/66 20130101; D21G
9/0018 20130101; D21G 9/0027 20130101; D21G 9/0054 20130101; D21G
9/0009 20130101 |
International
Class: |
D21G 9/00 20060101
D21G009/00; D21F 1/66 20060101 D21F001/66 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 28, 2012 |
DE |
10 2012 217 729.9 |
Claims
1-15. (canceled)
16. A method for controlling the formation of a fiber web in a
production process (fiber or paper-production), the method
comprising: performing a plurality of successive individual method
steps and thereby acquiring measured values; carrying out
controllable chemical and/or physical sequences or process steps,
respectively, in which materials required for generating the fiber
web are treated, combined, and/or dewatered in dependence on the
measured values, and thereby detecting at least some of the
measured values inline and directly or indirectly using the
measured values for controlling the formation; and generating at
least manipulated variables of the individual sequences or
processes, respectively, which influence the formation in a
relevant manner in the entire process in dependence on definable
secondary conditions.
17. The method according to claim 16, which comprises generating
the manipulated variables depending on a definable costing
function.
18. The method according to claim 17, wherein the costing function
evaluates a cost of expenditures arising as a result of a
modification of the manipulated variables.
19. The method according to claim 17, wherein the costing function
evaluates consequential costs arising as a result of a modification
of the manipulated variables.
20. The method according to claim 16, wherein one of the secondary
conditions is an equality condition.
21. The method according to claim 16, wherein one of the secondary
conditions is an inequality.
22. The method according to claim 16, which comprises generating
the secondary conditions depending on the initial materials or raw
materials, respectively, and/or on the chemicals, auxiliaries, and
energy supplied in the successive method steps, as well as on the
materials and emissions to be disposed of.
23. The method according to claim 17, which comprises minimizing
the costs with the costing function by way of an optimizing
algorithm while adhering to the secondary conditions.
24. The method according to claim 23, wherein the optimizing
algorithm, in order to adhere to the secondary formation
conditions, influences the manipulated variables influencing the
individual sequences or processes, respectively, in the entire
process so as to minimize a value of a potential deviation of the
formation from a nominal value.
25. The method according to claim 23, which comprises assigning the
optimizing algorithm a stored model which, either by way of
a-priori knowledge or by way of interpretation of effects of
previous re-adjustments, reproduces an influence of the manipulated
variables on the formation in a qualitative manner.
26. The method according to claim 16, which comprises implementing
the individual methods substantially in a stock preparation, a
headbox feed, and at a wet end of a fiber-web production
machine.
27. The method according to claim 26, which comprises using at
least one of the following manipulated variables in the stock
preparation for controlling the formation: a type of retention
agent; a dosing point of retention agent; an amount of retention
agent; a grinding performance; a dispersion performance; a material
composition; and an amount of fixing agent.
28. The method according to claim 26, which comprises using at
least one of the following manipulated variables in the headbox
feed for controlling the formation: a suspension jet geometry; a
lip opening; an aperture position; a lamella position; inserts
position; and a speed differential between jet and wire.
29. The method according to claim 26, which comprises using at
least one of the following manipulated variables at the wet end for
controlling the formation: a dewatering strip geometry; dewatering
strip pressures; a vacuum; and a wire tension.
30. The method according to claim 16, wherein one of the
manipulated variables is a machine speed.
Description
[0001] The invention relates to a method for controlling the
formation of a fiber web of a fiber or paper-producing process.
[0002] Fiber webs inter alia may also be a tissue or a cardboard
web.
[0003] The process of fiber or paper production substantially is
composed of a plurality of successive individual method steps in
which controllable chemical and/or physical sequences or process
steps, respectively, take place depending on measured values. In
this fashion, the materials required for generating the fiber web
are treated, combined, and/or dewatered in the individual process
steps. The measured values may be detected inline and directly or
indirectly used for controlling the formation. Besides, the
measured values may however also be determined offline in a
laboratory.
[0004] A particularly important measured variable in judging the
quality of the fiber web is the formation, that is to say the
distribution and composition of the fibers in the web. By employing
powerful quality-measuring technology it is possible to obtain an
exact online evaluation of the structure and the uniformity of the
internal fiber distribution (paper formation) in the paper. With
this, further quality parameters, such as printability, surface
finish, strength, rigidity, optical quality, etc. may be
improved.
[0005] The formation is influenced by various modifiable essential
variables or manipulated variables, respectively, such as vacuum,
wire tension, etc.. However, each re-adjustment of a manipulated
variable not only influences the process said manipulated variable
is intended to influence, but also downstream processes.
Re-adjustments of a process thus cause consequential effects, such
as, for example, increased wire wear, higher usage of chemicals,
etc.. These effects thus always also affect the total costs.
[0006] A number of publications pertaining to controlling the
formation are known from the prior art. In this fashion, a method
for optimizing the formation by modifying the headbox feed
consistency by way of the lip opening is known, for example.
Further controls are disclosed in EP 1 454 012 A1 or WO
00/34575.
[0007] It is one of the objects of the invention to propose a
formation control which improves the formation in the fiber
web.
[0008] It is a further object of the invention to provide a method
for controlling the formation, which enables the operation of the
paper machine to be stabilized.
[0009] According to the invention a method for controlling the
formation of a fiber web of the type mentioned at the outset is
proposed, in which at least the manipulated variables of the
individual sequences or processes, respectively, which influence
the formation in a relevant manner in the entire process are
generated depending on definable secondary conditions.
[0010] The formation is influenced by a plurality of successive
individual method steps in which controllable chemical and/or
physical sequences or process steps, respectively, take place
depending on measured values, wherein at least some of the measured
values are detected inline and directly or indirectly used for
controlling the formation.
[0011] The materials required for generating the fiber web are
treated, combined, and/or dewatered in successive individual method
steps. In order for the entire process to be controlled, all
measured values are processed in a data processing system, and
manipulated values according to defined specifications are
generated therefrom.
[0012] In turn, consequential effects which are undesirable arise
when the control values are re-adjusted. In this fashion the
formation may indeed be improved by re-adjusting a control value,
but increased wire wear may arise as a consequential effect on
account thereof, for example when the vacuum is set to be too
high.
[0013] If, as proposed, the manipulated values of the individual
sequences or processes, respectively, in the entire process are
generated depending on definable secondary conditions, negative
effects of this type may be prevented.
[0014] Secondary conditions in the sense of the invention are thus
understood to be conditions which defines value ranges which must
not be departed from or which permit a re-adjustment of the control
values only within a defined range, respectively, such that the
measured values at the measuring points which are assigned to the
process do not overshoot and/or undershoot certain limits.
[0015] Furthermore, the manipulated variables may be generated
depending on definable costing functions. One consequential effect
may be the costs. In this fashion the formation or the entire
process, respectively, may be additionally optimized with a view
toward reducing costs, wherein at all times also the other
secondary conditions and ultimately also the formation has to be
within certain limits.
[0016] In this fashion, the costs of expenditure which arise as a
result of the modification of the manipulated variables may also be
evaluated by means of the costing function. Furthermore, the
costing function however may also evaluate the consequential
costs.
[0017] The secondary condition may be included in generating the
limit values as an equality condition, for example
formation=constant, or else as an inequality, for example
increasing vacua in the wire station along the dewatering section,
such as p1>p2>p3.
[0018] Furthermore, the secondary conditions may be generated
depending on the initial materials or raw materials, respectively,
and/or on the chemicals, auxiliaries, and energy supplied in the
successive method steps, as well as on the materials and emissions
to be disposed of.
[0019] In order to minimize the costs, an optimizing algorithm by
means of which the costing functions may be optimized while
adhering to the secondary conditions may be employed, in that,
while considering the secondary conditions and the consequential
effects, all decisive manipulated variables are only re-adjusted to
the extent that the formation achieves a target value or a
formation value, respectively.
[0020] In this fashion the optimizing algorithm, in order to adhere
to the secondary formation conditions, may influence the
manipulated variables influencing the individual sequences or
processes, respectively, in the entire process such that the value
of a potential deviation of the formation from the nominal value is
minimized.
[0021] On the other hand, the optimizing algorithm may also be
assigned a stored model which either by way of a-priori knowledge
or by way of interpretation of the effects of previous
re-adjustments reproduces the influence of the manipulated
variables on the formation in a qualitative manner, on account of
which the down times of the processes are advantageously conjointly
considered.
[0022] However, both procedures may also be combined with each
other, such that further optimization takes place.
[0023] The individual methods in the sense of the invention
substantially take place in the stock preparation, the headbox
feed, and the wet end of a fiber-web production machine; that is to
say in those regions of a production machine for fiber webs where
modifying or influencing the formation may take place.
[0024] In this fashion, at least one of the following manipulated
variables may be used for controlling the formation in the stock
preparation: [0025] type of retention agent [0026] dosing point of
retention agent [0027] amount of retention agent [0028] grinding
performance [0029] dispersion performance [0030] material
composition [0031] amount of fixing agent.
[0032] In this fashion, at least one of the following manipulated
variables may be used for controlling the formation in the headbox
feed: [0033] suspension jet geometry [0034] lip opening [0035]
aperture position [0036] lamella position [0037] inserts position
[0038] speed differential between jet and wire.
[0039] Furthermore, at least one of the following manipulated
variables may be used for controlling the formation in the wet end:
[0040] dewatering strip geometry [0041] dewatering strip pressures
[0042] vacuum [0043] wire tension.
[0044] However, the wire characteristics as well as the wire
running time, in particular the change in the CFM value, have an
influence on the stable running of the machines, as well as on the
costs, and may be included in the secondary conditions as a
function, for example.
[0045] In this fashion it is, however, also possible for the
formation to be optimized in that the machine speed is modified, on
account of which the risk of web rupturing is reduced, in
particular in the case of raw materials which are difficult to
process or else in the case of variable climatic conditions. Web
rupturing has a great influence on the total costs.
[0046] It is one of the particular advantages of the invention that
operational stability and the formation can be stabilized in such a
manner that the costs of the entire process can be reduced to an
optimal minimum.
[0047] Further features of the method according to the invention
and further advantages of the invention are derived from the
following description with reference to the drawing.
[0048] The invention will be explained in more detail in the
following by means of diagrams, in which:
[0049] FIG. 1 shows a block diagram for illustrating the formation
control,
[0050] FIG. 2 shows a line chart for illustrating the correlations
between manipulated variables, secondary conditions, and costs
relative to a constant formation.
[0051] FIG. 1 shows a block diagram for illustrating the formation
control with the aid of which functioning of the system or of the
control, respectively, of the formation may be described.
[0052] The system or the control 1, respectively, of the formation
of a fiber web of a fiber or paper producing process depends on a
multiplicity of successive individual method steps. In this
fashion, various controllable chemical and/or physical sequences or
process steps, respectively, take place in the individual methods
steps, depending on measured values, in order to treat, combine,
and/or to dewater the material required for the formation of the
fiber web.
[0053] The individual method steps which are responsible for
generating the formation have been compiled in FIG. 1 in block 3.
The methods or processes may take place in the stock preparation,
the wet end process, the headbox feed, and the former, wherein each
process is capable of being influenced by at least one manipulated
variable 2. Referring to the possible manipulated variables a1, a2,
. . . , reference is made to those already mentioned, this not
being a complete enumeration.
[0054] Besides the manipulated variables, the secondary conditions
have an influence on the formation in that individual relevant
manipulated variables are generated depending on definable
secondary conditions.
[0055] The secondary conditions are defined in such a manner that a
particularly stable operation of the paper machine is ensured.
Certain measured values thus must not exceed certain limits which
must be mandatorily adhered to in order for the formation to be
optimized.
[0056] The control strategy may be implemented with the aid of an
optimizing algorithm which minimizes the costing function and
thereby adheres to the secondary conditions. These secondary
conditions may be present as an equality condition (for example,
formation=constant), as limit values (control limits, for example,
0.9<jet-wire ratio<1.1) or as an inequality (increasing vacua
along dewatering, for example, p1>p2>p3).
[0057] The consequential effects 5 are derived from the individual
re-adjustments of the manipulated variables of the processes. The
consequential effects may be measured online or in the laboratory,
and are directly or indirectly included in the secondary
conditions. In other words, the limits of the secondary conditions
are influenced by the consequential conditions. Consequential
effects may include wear, energy consumption, consumption of
chemicals, etc..
[0058] A line diagram for illustrating the correlations between
manipulated variables, secondary conditions, and costs relative to
a constant formation is illustrated in FIG. 2.
[0059] The essential variables (expenditure) which are
re-adjustable by the control are evaluated as expenditure costs by
way of a corresponding pricing function. The consequential costs
which arise on account of the re-adjustable essential variables are
likewise determined. The costing function thus calculates from the
total cost from the expenditure and consequential costs of the
setting of the manipulated variables which are relevant to the
formation. This costing function is minimized by way of an
optimizing algorithm, while adhering to the secondary conditions
defined above, such that an (iterative) step-by-step modification
of the setting takes place up to a cost-optimized operating point,
wherein the formation remains as a variable within a permissible
tolerance range.
[0060] In order to adhere to the secondary conditions of the
formation, the optimizing algorithm does/can design re-adjusting
such that the value of a potential deviation of the formation from
the nominal value (range) is minimized (in an ideal case to 0).
This may take place by way of a model which either by way of
a-priori knowledge or by way of interpretation of the effects of
the previous re-adjustments reproduces the influence of the
manipulated variables on the formation in a quantitative
manner.
LIST OF REFERENCE SIGNS
[0061] 1 Block diagram [0062] 2 Manipulated variables [0063] 3
Method steps [0064] 4 Secondary conditions [0065] 4a Limit values
of secondary conditions for manipulated variable Y [0066] 4b Limit
values of secondary conditions for manipulated variable X [0067] 5
Consequential effects [0068] 6 Target value of formation [0069] 8
Range of validity [0070] 9 Cost expenditure
* * * * *