Method for overall regulation of the headbox of a paper machine or equivalent

• US 5,812,404 A
• Filed: 04/18/1996
• Issued: 09/22/1998
• Est. Priority Date: 04/18/1996
• Status: Expired due to Term

• Current Assignee: Valmet Incorporated (Metso Corporation)
• Original Assignee: Valmet Incorporated (Metso Corporation)
• Inventors: Hamalainen, Jari, Nyberg, Petri
• Primary Examiner(s): Voeltz, Emanuel Todd
• Assistant Examiner(s): COLE, TONY MITCHELL
• Application Number:
  US08/634,465
• Time in Patent Office: 887 Days
• Field of Search: 364/148, 364/149, 364/152, 364/471.01, 364/471.02, 366/160.1, 264/517, 264/518, 162/258, 162/259, 162/336, 162/262, 162/216, 162/252, 162/253, 162/198, 162/DIG. 10, 162/212, 162/338, 162/343
• US Class Current: 700/128
• CPC Class Codes: D21F 1/06 Regulating pulp flow
• CPC Class Codes: D21G 9/0027 controlling the forming section
• CPC Class Codes: H01L 21/568 Temporary substrate used as encapsulation process aid H01L21/4832 and H01L21/566 take precedence
• CPC Class Codes: H01L 21/6835 using temporarily an auxiliary support
• CPC Class Codes: H01L 2221/68377 with parts of the auxiliary support remaining in the finished device
• CPC Class Codes: H01L 24/97 the devices being connected to a common substrate, e.g. interposer, said common substrate being separable into individual assemblies after connecting
• CPC Class Codes: H01L 2924/01005 Boron [B]
• CPC Class Codes: H01L 2924/01006 Carbon [C]
• CPC Class Codes: H01L 2924/01015 Phosphorus [P]
• CPC Class Codes: H01L 2924/01019 Potassium [K]
• CPC Class Codes: H01L 2924/01023 Vanadium [V]
• CPC Class Codes: H01L 2924/01033 Arsenic [As]
• CPC Class Codes: H01L 2924/01039 Yttrium [Y]
• CPC Class Codes: H01L 2924/01074 Tungsten [W]
• CPC Class Codes: H01L 2924/01078 Platinum [Pt]

Abstract

A method for the continuous overall regulation of a single-layer or multi-layer headbox of a paper, board or pulp-draining machine. A physical fluid flow model of a pulp suspension flow discharged from the headbox to be regulated is formed and solved to obtain a simulated flow state based, e.g., on data on the geometry of the headbox and initial and boundary conditions related to the headbox. A target flow state based on the quality requirements of the paper produced from the pulp suspension flow and the costs of operation and runnability of the machine is obtained and a difference between the simulated flow state obtained as the solution of the flow model and the target flow state is determined. This difference constitutes a cost function which is optimized to determine optimal regulation values and set values for instrumentation devices and actuators of the headbox which affect the pulp suspension flow. The optimal regulation and set values are provided to the devices and actuators of the headbox such that the devices and actuators of the headbox may operate at the optimal regulation and set values.

Claims

1. A method for the continuous overall regulation of a single-layer or multi-layer headbox of a paper, board or pulp-draining machine, comprising the steps of:

(a.) forming a physical fluid flow model of a pulp suspension flow to be regulated in the headbox and upon discharge from the headbox, the pulp suspension flow being processed after discharge from the headbox to produce paper;

(b.) solving the flow model to obtain a simulated flow state based on data on a geometry of the headbox and initial and boundary conditions related to the headbox;

(c.) obtaining a target flow state based on quality requirements of the paper produced from the pulp suspension flow and costs of operation and runnability of the machine;

(d.) determining a difference between the simulated flow state obtained as the solution of the flow model and the target flow state, the difference constituting a cost function;

(e.) optimizing the cost function and then determining optimal regulation values for regulation devices of the headbox which affect the pulp suspension flow in view of the cost function; and

thereafter;

(f.) providing the optimal regulation values to the regulation devices of the headbox such that the regulation devices of the headbox operate at the optimal regulation values to thereby realize the optimization of the cost function,

the step of optimizing the cost function and then determining optimal regulation values for the regulation devices of the headbox being carried out in accordance with the following algorithm;

(1) a necessary flow-rate, stock-grade and geometry data of the headbox are read, and the optimizing is started from a first set of regulation values α

.sup.(i), i=0, and a value F.sup.(i) of the cost function is computed by solving the flow model of the headbox,

(2) a gradient ∇

F.sup.(i) of the cost function with the first set of regulation values α

.sup.(i) concerned is computed,

(3) a direction p.sup.(i) is determined by means of the gradient ∇

F.sup.(i) and indicates the direction the first set of regulation values must change in order to lower the value of the cost function, a sensitivity of the cost function F in relation to a regulation quantity α

_k based on the first set of regulation values being computed by means of a difference quotient ##EQU6## or by solving an adjoint state equation corresponding to the flow model of the headbox,

(4) a second set of regulation values (α

.sup.(i+1) are determined by varying the first set of regulation values in the direction determined in the preceding step (3) optimally

space="preserve" listing-type="equation">α

.sup.(i+1) =α

.sup.(i) +λ

.sup.(i) p.sup.(i),

in which connection a step length λ

.sup.(i) is determined so that the cost function receives a lower value than with the preceding iteration, F.sup.(i+1) <

F.sup.(i), and the second set of regulation values (α

.sup.(i+1) are admissible, and

(5) if the value of the cost function obtained in the preceding steps is not yet sufficiently low, an index for iteration step is increased, i=i+1, the second set of regulation values becomes the first set of regulation values and optimizing is continued from the above stage (2), and in a contrary case when the value of the cost function obtained in the preceding steps is sufficiently low, performing of the algorithm is discontinued, and the optimal values of regulation devices are set equal to the second set of regulation values α

.sup.(i+1) and they are transmitted to the regulation devices of the headbox.

2. The method of claim 1, wherein the step of forming the flow model comprises the steps of:

forming the flow model on the basis of fluid dynamics relationship or on the basis of simplified equations derived from fluid dynamics relationships which are solved numerically by means of a computer, and

utilizing on-line or laboratory measurements and information provided by an operator of the paper machine as the initial and boundary values of the flow model.

3. The method of claim 1, further comprising the steps of:

computing a plurality of flow states by means of a physical model,

adapting a statistical model from the plurality of flow states to illustrate the flow state of the headbox and/or the dependency of the cost function from regulation quantities based on the regulation values, or instructing a neural network to illustrate the flow state of the headbox and/or the dependency of the cost function from regulation quantities based on the regulation values from the plurality of flow states, and

utilizing the statistical model or the neural network for optimizing the cost function.

4. The method of claim 1, wherein the step of solving the flow model comprises the steps of:

using a computer having a high computing capacity and comprising at least one processor, and

directing the computer to use numerical methods of solution.

5. The method of claim 4, further comprising the step of selecting the numerical methods of solution from a group consisting of finite-element, finite-difference, finite-volume methods, spectral and spectral-element methods.

6. The method of claim 1, wherein the step of optimizing the cost function is determined by an algorithm and is not based on computing the gradient of the cost function.

7. The method of claim 1, further comprising the step of selecting measurement and regulation quantities of the headbox to be regulated based on the optimal regulation values from a group consisting of static pressure, consistency, and flow rate of the stock flow into the header;

velocity profile of the flow into the header;

profile of cross-sectional area of header;

profiles of consistency and flow rate of dilution feed;

pressure-loss profile of turbulence generator, consistency profile produced by dilution at the outlet end of turbulence generator;

recirculation flow rate and edge feed flow rates at forward edge and rear edge;

measured/regulated shape of slice channel in machine and cross direction;

velocity components of slice jet;

consistency, thickness and turbulence-energy profiles of the slice jet; and

overall flow rate of the slice jet.

8. The method of claim 1, wherein the cost function comprises at least the target profile of finished paper selected from a group consisting of a basis weight profile, a formation profile and a fiber-orientation profile, or a function of at least one target profile selected from a group consisting of the basis weight profile, the formation profile and the fiber-orientation profile.

9. The method of claim 8, wherein besides the at least one target profile, the cost function also comprises components related to runnability and/or energy consumption of the paper machine.

10. The method of claim 1, wherein the cost function is optimized by selecting a quality level for the paper, and determining at least one of a lowest possible overall flow rate and energy consumption at which the selected quality level for the paper is reached by minimizing a recirculation flow rate of the pulp suspension flow until the selected quality level for the paper is reached.

11. The method of claim 1, further comprising the step of weighting different parts of the cost function, the parts being quality of the paper, runnability of the machine and energy consumption of the machine.

12. The method of claim 11, wherein the step of weighting different parts of the cost function comprises the steps of assigning the quality of the paper with a highest weight and thus most important part, and assigning the runnability of the machine and energy consumption of the machine lesser weights that the weight assigned to the quality of the paper such that the runability of the machine is improved and energy is saved only if improvement in the runnability of the machine and saving of energy does not cause a deterioration in the quality of the paper.

13. The method of claim 1, wherein the cost function includes quality quantities which are expressed by means of a velocity profile and turbulence of a slice jet of the pulp suspension flow being discharged from the headbox.

14. The method of claim 1, wherein the step of solving the flow model comprises the steps of:

using a computer having a high computing capacity and comprising at least one processor, and

increasing a speed in which the computer solves the flow model by performing computations in parallel.

15. The method of claim 14, wherein the computer comprises a plurality of processors and the speed of the computer is increased by computing each of a plurality of sensitivities of changes in the cost function in relation to different regulation devices of the headbox by means of a separate processor in the computer.

16. The method of claim 15, wherein the sensitivities of the cost function in relation to different regulation devices are determined by means of a sensitivity analysis carried out in an environment of linearized solution so that the flow model is solved by means of a perturbation theory by determining the gradient of the cost function, wherein for the optimization of the cost function, in other respects, a real non-linear model is used such that the optimization is based on a real flow model, and any faults arising from the perturbation theory do not have a substantial effect on the final result of the optimization.

17. The method of claim 1, wherein the step of solving the flow model comprises the steps of:

composing the flow model of the headbox from several sub-models,

simultaneously solving the sub-models by means of processors of a computer, each of the sub-models being solved by means of a respective one of the processors and

directing data from each of the processors to other ones of the processors.

18. The method of claim 1, wherein the step of solving the flow model comprises the step of:

using a computer; and

enhancing operation of the computer by dividing the optimizing into parts so that regulation quantities based on the regulation values that have the greatest effect on quality of the paper are optimized more frequently while reacting to the changes rapidly, whereas other regulation quantities are optimized less frequently, and that for optimizing of the regulation quantities for which all of the flow model is not needed a suitable sub-model is used.

19. A method for the continuous overall regulation of a single-layer or multi-layer headbox of a paper, board or pulp-draining machine, comprising the steps of:

(a.) forming a physical fluid flow model of a pulp suspension flow to be regulated in the headbox and upon discharge from the headbox, the pulp suspension flow being processed after discharge from the headbox to produce paper;

(b.) solving the flow model to obtain a simulated flow state based on data on a geometry of the headbox and initial and boundary conditions related to the headbox;

(c.) obtaining a target flow state based on quality requirements of the paper produced from the pulp suspension flow and costs of operation and runnability of the machine

(d.) determining a difference between the simulated flow state obtained as the solution of the flow model and the target flow state, the difference constituting a cost function, the cost function comprising at least one target profile of the paper selected from a group consisting of a basis weight profile, a formation profile and a fiber-orientation profile, or a function of at least one target profile selected from a group consisting of a basis weight profile, a formation profile and a fiber-orientation profile;

(e.) optimizing the cost function and then determining optimal regulation values for regulation devices of the headbox which affect the pulp suspension flow in view of the cost function; and

thereafter

(f.) providing the optimal regulation values to the regulation devices of the headbox such that the regulation devices of the headbox operate at the optimal regulation values to thereby realize the optimization of the cost function.

20. The method of claim 19, wherein besides the at least one target profile, the cost function also comprises components related to runnability and/or energy consumption of the paper machine.

21. A method for the continuous overall regulation of a single-layer or multi-layer headbox of a paper, board or pulp-draining machine, comprising the steps of:

(a.) forming a physical fluid flow model of a pulp suspension flow to be regulated in the headbox and upon discharge from the headbox, the pulp suspension flow being processed after discharge from the headbox to produce paper;

(b.) solving the flow model to obtain a simulated flow state based on data on a geometry of the headbox and initial and boundary conditions related to the headbox;

(c.) obtaining a target flow state based on quality requirements of the paper produced from the pulp suspension flow and costs of operation and runnability of the machine

(d.) determining a difference between the simulated flow state obtained as the solution of the flow model and the target flow state, the difference constituting a cost function;

(e.) optimizing the cost function and then determining optimal regulation values for regulation devices of the headbox which affect the pulp suspension flow in view of the cost function, the cost function being optimized by selecting a quality level for the paper, and determining at least one of a lowest possible overall flow rate and energy consumption at which the selected quality level for the paper is reached by minimizing a recirculation flow rate of the pulp suspension flow until the selected quality level for the paper is reached; and

thereafter

(f.) providing the optimal regulation values to the regulation devices of the headbox such that the regulation devices of the headbox operate at the optimal regulation values to thereby realize the optimization of the cost function.

22. A method for the continuous overall regulation of a single-layer or multi-layer headbox of a paper, board or pulp-draining machine, comprising the steps of:

(a.) forming a physical fluid flow model of a pulp suspension flow to be regulated in the headbox and upon discharge from the headbox, the pulp suspension flow being processed after discharge from the headbox to produce paper;

(b.) solving the flow model to obtain a simulated flow state based on data on a geometry of the headbox and initial and boundary conditions related to the headbox;

(c.) obtaining a target flow state based on quality requirements of the paper produced from the pulp suspension flow and costs of operation and runnability of the machine

(d.) determining a difference between the simulated flow state obtained as the solution of the flow model and the target flow state, the difference constituting a cost function;

(e.) weighting different parts of the cost function, the parts being quality of the paper, runnability of the machine and energy consumption of the machine;

(f.) optimizing the cost function and then determining optimal regulation values for regulation devices of the headbox which affect the pulp suspension flow in view of the cost function; and

thereafter

(g.) providing the optimal regulation values to the regulation devices of the headbox such that the regulation devices of the headbox operate at the optimal regulation values to thereby realize the optimization of the cost function.

23. The method of claim 22, wherein the step of weighting different parts of the cost function comprises the steps of assigning the quality of the paper with a highest weight and thus most important part, and assigning the runnability of the machine and energy consumption of the machine lesser weights than the weight assigned to the quality of the paper such that the runnability of the machine is improved and energy is saved only if improvement in the runnability of the machine and saving of energy does not cause a deterioration in the quality of the paper.

24. A method for the continuous overall regulation of a single-layer or multi-layer headbox of a paper, board or pulp-draining machine, comprising the steps of:

(a.) forming a physical fluid flow model of a pulp suspension flow to be regulated in the headbox and upon discharge from the headbox, the pulp suspension flow being processed after discharge from the headbox to produce paper;

(b.) solving the flow model to obtain a simulated flow state based on data on a geometry of the headbox and initial and boundary conditions related to the headbox, the step of solving the flow model comprising the steps of using a computer having a high computing capacity and a plurality of processors, and increasing a speed at which the computer solves the flow model by performing computations in parallel;

(c.) obtaining a target flow state based on quality requirements of the paper produced from the pulp suspension flow and costs of operation and runnability of the machine

(d.) determining a difference between the simulated flow state obtained as the solution of the flow model and the target flow state, the difference constituting a cost function;

(e.) optimizing the cost function and then determining optimal regulation values for regulation devices of the headbox which affect the pulp suspension flow in view of the cost function;

thereafter

(f.) providing the optimal regulation values to the regulation devices of the headbox such that the regulation devices of the headbox operate at the optimal regulation values to thereby realize the optimization of the cost function; and

(g.) increasing the speed of the computer by computing each of a plurality of sensitivities of changes in the cost function in relation to different regulation devices of the headbox by means of a separate one of the processors in the computer.

25. The method of claim 24, wherein the sensitivities of the cost function in relation to different regulation devices are determined by means of a sensitivity analysis carried out in an environment of linearized solution so that the flow model is solved by means of a perturbation theory by determining the gradient of the cost function, wherein for the optimization of the cost function, in other respects, a real non-linear model is used such that the optimization is based on a real flow model, and any faults arising from the perturbation theory do not have a substantial effort on the final result of the optimization.

26. A method for the continuous overall regulation of a single-layer or multi-layer headbox of a paper, board or pulp-draining machine, comprising the steps of:

(a.) forming a physical fluid flow model of a pulp suspension flow to be regulated in the headbox and upon discharge from the headbox, the pulp suspension flow being processed after discharge from the headbox to produce paper;

(b.) solving the flow model to obtain a simulated flow state based on data on a geometry of the headbox and initial and boundary conditions related to the headbox;

(c.) obtaining a target flow state based on quality requirements of the paper produced from the pulp suspension flow and costs of operation and runnability of the machine

(d.) determining a difference between the simulated flow state obtained as the solution of the flow model and the target flow state, the difference constituting a cost function;

(e.) optimizing the cost function and then determining optimal regulation values for regulation devices of the headbox which affect the pulp suspension flow in view of the cost function; and

thereafter

(f.) providing the optimal regulation values to the regulation devices of the headbox such that the regulation devices of the headbox operate at the optimal regulation values to thereby realize the optimization of the cost function;

the step of solving the flow model comprising the steps of using a computer, and

enhancing operation of the computer by dividing the optimizing into parts so that regulation quantities based on the regulation values that have the greatest effect on quality of the paper are optimized more frequently while reacting to the changes rapidly, whereas other regulation quantities are optimized less frequently, and that for optimizing of the regulation quantities for which all of the flow model is not needed a suitable sub-model is used.

27. A method for the continuous overall regulation of a single-layer or multi-layer headbox of a paper, board or pulp-draining machine, comprising the steps of:

(a.) forming a physical fluid flow model of a pulp suspension flow to be regulated in the headbox and upon discharge from the headbox, the pulp suspension flow being processed after discharge from the headbox to produce paper;

(b.) solving the flow model to obtain a simulated flow state based on data on a geometry of the headbox and initial and boundary conditions related to the headbox;

(c.) obtaining a target flow state based on quality requirements of the paper produced from the pulp suspension flow and costs of operation and runnability of the machine

(d.) determining a difference between the simulated flow state obtained as the solution of the flow model and the target flow state, the difference constituting a cost function;

(e.) optimizing the cost function and then determining optimal regulation values for regulation devices of the headbox which affect the pulp suspension flow in view of the cost function;

thereafter

(f.) providing the optimal regulation values to the regulation devices of the headbox such that the regulation devices of the headbox operate at the optimal regulation values to thereby realize the optimization of the cost function; and

(g.) selecting measurement and regulation quantities of the headbox to be regulated based on the optimal regulation values from a group consisting of static pressure, consistency, and flow rate of the stock flow into the headbox;

profiles of consistency and flow rate of feed of a dilution liquid into the headbox;

recirculation flow rate and edge feed flow rates at forward edge and rear edge of the headbox;

measured/regulated shape of a slice channel of the headbox in machine and cross directions;

velocity components of a slice jet of the headbox;

consistency, thickness and turbulence-energy profiles of the slice jet; and

overall flow rate of the slice jet.