EP2370628A1 - Procédure et système de commande d'un raffineur afin d'améliorer le rendement en énergie et la qualité de pâte - Google Patents

Procédure et système de commande d'un raffineur afin d'améliorer le rendement en énergie et la qualité de pâte

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Publication number
EP2370628A1
EP2370628A1 EP08875398A EP08875398A EP2370628A1 EP 2370628 A1 EP2370628 A1 EP 2370628A1 EP 08875398 A EP08875398 A EP 08875398A EP 08875398 A EP08875398 A EP 08875398A EP 2370628 A1 EP2370628 A1 EP 2370628A1
Authority
EP
European Patent Office
Prior art keywords
refiner
process section
measurement
pulp
variables
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.)
Granted
Application number
EP08875398A
Other languages
German (de)
English (en)
Other versions
EP2370628B1 (fr
Inventor
Alf Isaksson
Anders Karlström
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ABB Research Ltd Switzerland
ABB Research Ltd Sweden
Original Assignee
ABB Research Ltd Switzerland
ABB Research Ltd Sweden
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Filing date
Publication date
Application filed by ABB Research Ltd Switzerland, ABB Research Ltd Sweden filed Critical ABB Research Ltd Switzerland
Publication of EP2370628A1 publication Critical patent/EP2370628A1/fr
Application granted granted Critical
Publication of EP2370628B1 publication Critical patent/EP2370628B1/fr
Active legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21D—TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
    • D21D1/00—Methods of beating or refining; Beaters of the Hollander type
    • D21D1/002—Control devices
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21D—TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
    • D21D1/00—Methods of beating or refining; Beaters of the Hollander type
    • D21D1/20—Methods of refining
    • D21D1/30—Disc mills

Definitions

  • the invention relates to an improved method for controlling one or more refiners in a process section for thermo-mechanical pulp (TMP) refining.
  • TMP thermo-mechanical pulp
  • the present invention is applicable in all technical areas where refiners are used, such as pulp and paper industry as well as related industries.
  • Refiners of one sort or another play a central role in the production of high yield pulp for the pulp and paper industry and related industries through grinding, for example, thermo- mechanical pulp (TMP) or chemical thermo-mechanical pulp (CTMP) starting from lignin- cellulose material such as wood chips.
  • TMP thermo- mechanical pulp
  • CMP chemical thermo-mechanical pulp
  • Two types of refiners are important to mention here; low consistency (LC) refining where the pulp is refined at about 4 per cent consistency (dry content), and high consistency (HC) refining where the consistency is commonly about 40 per cent.
  • LC refining is done in a two-phase system chips/pulp and water, while HC refining has three phases; chips/pulp, water and steam.
  • Refiners are also used in other industrial applications, such as for example manufacturing of wood fiber board.
  • refiners consist of two circular plates, in between which the material to be treated passes from the inner part to the periphery of the plates.
  • static refiner plate usually there is one static refiner plate and one rotating refiner plate, rotating at a very high speed.
  • FIG. 4 A more complete schematic illustration of a known refiner 1 is given in Figure 4.
  • the raw material which may consist of wood chips 5 or already treated pulp for a previous stage enters at the center C of the refiner.
  • the material is transported via one or more screw feeders 7.
  • the raw material is normally mixed with dilution water 2 whose flow is usually measured and controlled. Alternatively water may be added directly in the refiner.
  • the material is then treated on its way to the periphery of the refiner plates.
  • the static refiner plate 3, or stator is usually pushed towards the rotating one 4, or rotor, either electro-mechanically or hydraulically.
  • the rotating disc or discs are driven by one or two motors 10.
  • the grinding zone or as it is often called the refining zone may also have a variable gap along the radius dependent on the design of the plates.
  • the figure also shows the outlet position 6 where the pressure Poutlet is measured, and the point where production inlet pressure Pinlet 8 may be measured.
  • the diameter of the refiner plates differ dependent on size (production capacity) of the refiner and brand.
  • the plates also called segments
  • These segments have grinding patterns, see Figure 5, with bars 15, 15' and troughs 16 that differ dependent on supplier.
  • the bars act as knives that defibrillate chips or further refine the already produced pulp.
  • fibers, water and steam is also transported in the troughs between the bars.
  • the amount of steam is spatially dependent, why both water and steam may exist together with chips/pulp in the refining zone.
  • water will normally be bound to the fibres.
  • Dependent on the segment design will occur in the refiner.
  • no steam is generated.
  • refiners there are also other types of refiners such as double disc, where both plates rotate counter to each other, or conic refiners. Yet another type are called twin refiners, where there are four refiner plates. A centrally placed rotor has two refiner plates mounted one on either side, and then there are two static refiner plates that are pushed against each other using, for example, hydraulic cylinders thus creating two refining zones.
  • refiner plates When refining wood chips or previously refined pulp the refiner plates are typically pushed against each other to obtain a plate gap of approximately 0.2-0.7 mm dependent on what type of refiner is used.
  • the controlled variables consist of the specific energy (i.e. the ratio between the refiner motor load and the pulp production), alternatively just the motor load, the pulp consistency out of the refiner, and best case also at least one variable describing the quality of the pulp (e.g. Canadian Standard Freeness, CSF).
  • CSF Canadian Standard Freeness
  • a typical refiner line consists of two refiners in series; a primary refiner (PR) and a secondary refiner (SR). Often there is also a processing step called reject refining.
  • thermo and/or pressure are measured along the refining zone for the purpose of visualizing a temperature profile, and/or a pressure profile.
  • a temperature profile For example gap, production or dilution water the temperature changes and can thus be controlled.
  • temperature and/or pressure sensors are used placed directly in the plate or may be encapsulated in a measurement strip, also called sensor array, along the active radius of the refiner, see EP0788407[3].
  • the aim of the present invention is to remedy one or more of the above mentioned problems.
  • this and other aims are obtained by a method according to claim 1.
  • a method for controlling a process section for thermo-mechanical pulp (TMP) refining, the process section comprising at least one first refiner having a plurality of sensors arranged in a predetermined position on a refiner plate of said at least one first refiner, the method comprising measuring, alternatively estimating, one or more process variables representing external states outside of the refiner for the process section and measuring, alternatively estimating, one or more values representing one or more internal states inside said at least one first refiner, and the possibility to manipulate one ore more variables, wherein a change is calculated for said at least one manipulated variable for said at least one refiner using said measurement of an internal state of said at least one refiner and a measurement of said one or more process external states for said process section by means of a mathematical process model.
  • a method for controlling a process section for thermo-mechanical pulp refining, the process section comprising at least one first refiner having a plurality of sensors arranged in a predetermined position on a refiner plate of said at least one first refiner, the method comprising measuring, alternatively estimating, one or more process variables representing external states outside of the refiner for the process section and measuring, alternatively estimating, one or more values representing one or more internal states inside said at least one first refiner, and the possibility to manipulate one ore more variables by means of a mathematical process model, and wherein a change is calculated for said at least one manipulated variable for said at least one refiner using a mathematical process model which is described by a set of nonlinear differential equations or difference equations with a vector valued non linear function.
  • a method for controlling a process section for thermo-mechanical pulp refining, the process section comprising at least one first refiner having a plurality of sensors arranged in a predetermined position on a refiner plate of said at least one first refiner, the method comprising measuring, alternatively estimating, one or more process variables representing external states outside of the refiner for the process section and measuring, alternatively estimating, one or more values representing one or more internal states inside said at least one first refiner, and the possibility to manipulate one ore more variables using a mathematical process model, wherein the mathematical process model is described by a set of linear differential equations or difference equations.
  • a method for controlling a process section for thermo-mechanical pulp refining, the process section comprising at least one first refiner having a plurality of sensors arranged in a predetermined position on a refiner plate of said at least one first refiner, the method comprising measuring, alternatively estimating, one or more process variables representing external states outside of the refiner for the process section and measuring, alternatively estimating, one or more values representing one or more internal states inside said at least one first refiner, and the possibility to manipulate one ore more variables using a mathematical process model, wherein the mathematical process model is described by Laplace transforms and transfer functions.
  • a method for controlling a process section for thermo-mechanical pulp refining, the process section comprising at least one first refiner having a plurality of sensors arranged in a predetermined position on a refiner plate of said at least one first refiner, the method comprising measuring, alternatively estimating, one or more process variables representing external states outside of the refiner for the process section and measuring, alternatively estimating, one or more values representing one or more internal states inside said at least one first refiner, and the possibility to manipulate one ore more variables using a mathematical process model, by calculating a process change using a measurement in which said internal state is temperature which is calculated using an array of temperature measurements along the radius of a disc inside said at least one refiner.
  • a method for controlling a process section for thermo-mechanical pulp refining, the process section comprising at least one first refiner having a plurality of sensors arranged in a predetermined position on a refiner plate of said at least one first refiner, the method comprising measuring, alternatively estimating, one or more process variables representing external states outside of the refiner for the process section and measuring, alternatively estimating, one or more values representing one or more internal states inside said at least one first refiner, and the possibility to manipulate one ore more variables using a mathematical process model, by calculating a process change and changing at least one manipulated variable to affect a change in a measure or estimate of pulp quality.
  • a method for controlling a process section for thermo-mechanical pulp refining, the process section comprising at least one first refiner having a plurality of sensors arranged in a predetermined position on a refiner plate of said at least one first refiner, the method comprising measuring, alternatively estimating, one or more process variables representing external states outside of the refiner for the process section and measuring, alternatively estimating, one or more values representing one or more internal states inside said at least one first refiner, and the possibility to manipulate one ore more variables using a mathematical process model, by using the mathematical process model to mimimize the deviation between reference values and measured values, or functions, of internal and/or external states).
  • a method for controlling a process section for thermo-mechanical pulp refining, the process section comprising at least one first refiner having a plurality of sensors arranged in a predetermined position on a refiner plate of said at least one first refiner, the method comprising measuring, alternatively estimating, one or more process variables representing external states outside of the refiner for the process section and measuring, alternatively estimating, one or more values representing one or more internal states inside said at least one first refiner, and the possibility to manipulate one ore more variables using a mathematical process model, by using the mathematical process model to mimimize the deviation between reference values and estimated values of internal and/or external states.
  • a method for controlling a process section for thermo-mechanical pulp refining, the process section comprising at least one first refiner having a plurality of sensors arranged in a predetermined position on a refiner plate of said at least one first refiner, the method comprising measuring, alternatively estimating, one or more process variables representing external states outside of the refiner for the process section and measuring, alternatively estimating, one or more values representing one or more internal states inside said at least one first refiner, and the possibility to manipulate one ore more variables using a mathematical process model, and by feeding the output from said at least one first refiner into a second refiner such that said process section comprises a two stage refiner.
  • a method for controlling a process section for thermo-mechanical pulp refining, the process section comprising at least one first refiner having a plurality of sensors arranged in a predetermined position on a refiner plate of said at least one first refiner, the method comprising measuring, alternatively estimating, one or more process variables representing external states outside of the refiner for the process section and measuring, alternatively estimating, one or more values representing one or more internal states inside said at least one first refiner, and the possibility to manipulate one ore more variables using a mathematical process model, by calculating a process change for at least one manipulated variable for the second refiner using said measurement of an internal state of the second refiner and a measurement of said one or more external states for said process section by means of a mathematical model.
  • a method for controlling a process section for thermo-mechanical pulp refining, the process section comprising at least one first refiner having a plurality of sensors arranged in a predetermined position on a refiner plate of said at least one first refiner, the method comprising measuring, alternatively estimating, one or more process variables representing external states outside of the refiner for the process section and measuring, alternatively estimating, one or more values representing one or more internal states inside said at least one first refiner, and the possibility to manipulate one ore more variables using a mathematical process model, by calculating a process change for at least one manipulated variable of a process section comprising two or more refiners using said at least one measurement of an internal state for each refiner and a measurement of an external state for each refiner and at least a quality measurement after the second refiner.
  • a method for controlling a process section for thermo-mechanical pulp refining, the process section comprising at least one first refiner having a plurality of sensors arranged in a predetermined position on a refiner plate of said at least one first refiner, the method comprising measuring, alternatively estimating, one or more process variables representing external states outside of the refiner for the process section and measuring, alternatively estimating, one or more values representing one or more internal states inside said at least one first refiner, and the possibility to manipulate one ore more variables using a mathematical process model, by calculating a process change for at least one manipulated variable of a process section comprising two or more refiners using said measurement of an internal state for each refiner and a measurement of an external state for each refiner and a quality measurement of the second refiner in order to optimize energy input to said process section.
  • a method for controlling a process section for thermo-mechanical pulp refining, the process section comprising at least one first refiner having a plurality of sensors arranged in a predetermined position on a refiner plate of said at least one first refiner, the method comprising measuring, alternatively estimating, one or more process variables representing external states outside of the refiner for the process section and measuring, alternatively estimating, one or more values representing one or more internal states inside said at least one first refiner, and the possibility to manipulate one ore more variables using a mathematical process model, by calculating a process change using a measurement in which said internal state is pressure (P / ) which is calculated using an array of measurements along the radius of a disc inside said at least one refiner.
  • P / internal state
  • a system including a process section for thermo-mechanical pulp (TMP) refining, the process section comprising at least one first refiner having a plurality of sensors arranged in a predetermined position on a refiner plate of said at least one first refiner, the method comprising measuring one or more process variables for said process section and measuring one or more internal states in said at least one first refiner wherein the system further comprises apparatus for applying a process change calculated on at least one manipulated variable for said at least one refiner using said measurement or estimate of an internal state of said at least one refiner and a measurement of said one or more process variables for said process section by means of a mathematical model to monitor and control said at least one first refiner.
  • TMP thermo-mechanical pulp
  • a system including a process section for thermo-mechanical pulp refining, the process section comprising at least one first refiner having a plurality of sensors arranged in a predetermined position on a refiner plate of said at least one first refiner, the method comprising measuring one or more process variables for said process section and measuring one or more internal states in said at least one first refiner wherein the system further comprises apparatus for applying a process change calculated on at least one manipulated variable for said at least one refiner using said measurement or estimate of an internal state of said at least one refiner and a measurement of said one or more process variables for said process section by means of a mathematical model to control said at least one first refiner wherein one or more of said plurality of sensors are arranged on an active radius of a beating disc of a refiner in said process section.
  • a system including a process section for thermo-mechanical pulp refining, the process section comprising at least one first refiner having a plurality of sensors arranged in a predetermined position on a refiner plate of said at least one first refiner, the method comprising measuring one or more process variables for said process section and measuring one or more internal states in said at least one first refiner wherein the system further comprises apparatus for applying a process change calculated on at least one manipulated variable for said at least one refiner using said measurement or estimate of an internal state of said at least one refiner and a measurement of said one or more process variables for said process section by means of a mathematical model to control said at least one first refiner wherein said process section comprises two or more refiners which are arranged connected in series, alternatively in parallel.
  • a system including a process section for thermo-mechanical pulp refining, the process section comprising at least one first refiner having a plurality of sensors arranged in a predetermined position on a refiner plate of said at least one first refiner, the method comprising measuring one or more process variables for said process section and measuring one or more internal states in said at least one first refiner wherein the system further comprises apparatus for applying a process change calculated on at least one manipulated variable for said at least one refiner using said measurement or estimate of an internal state of said at least one refiner and a measurement of said one or more process variables for said process section by means of a mathematical model to control said at least one first refiner wherein the system further comprises one or more control units arranged as a control optimiser.
  • a system including a process section for thermo-mechanical pulp refining, the process section comprising at least one first refiner having a plurality of sensors arranged in a predetermined position on a refiner plate of said at least one first refiner, the method comprising measuring one or more process variables for said process section and measuring one or more internal states in said at least one first refiner wherein the system further comprises apparatus for applying a process change calculated on at least one manipulated variable for said at least one refiner using said measurement or estimate of an internal state of said at least one refiner and a measurement of said one or more process variables for said process section by means of a mathematical model to control said at least one first refiner wherein the system further comprises one or more control units arranged as a state estimator.
  • a system including a process section for thermo-mechanical pulp refining, the process section comprising at least one first refiner having a plurality of sensors arranged in a predetermined position on a refiner plate of said at least one first refiner, the method comprising measuring one or more process variables for said process section and measuring one or more internal states in said at least one first refiner wherein the system further comprises apparatus for applying a process change calculated on at least one manipulated variable for said at least one refiner using said measurement or estimate of an internal state of said at least one refiner and a measurement of said one or more process variables for said process section by means of a mathematical model to control said at least one first refiner wherein the system further comprises a memory storage device in which are stored one or more computer programs for carrying out a method according to claim 1.
  • the aim with all refiner control systems is to secure the pulp quality at a specified energy input to the refiners.
  • the problem is that existing control systems on the market are slow which results in difficulties to guarantee a specific pulp quality to a minimum energy input demand.
  • process control systems for refiners have no information from the true refining process, i.e. the process which occurs in the refining zone and the process descriptions are normally based on outputs to be controlled such as, specific energy E or the motor load M and if available also the measured consistency C in the blowline.
  • outputs are normally manipulated by changing e.g. the plate gap (controlled by the applied hydraulic pressure P hydr which results in a force on the plates or e.g. a electro-mechanically based force on the plates) and the dilution water flow F D to the refiners as described by
  • Y represents the vector to be controlled and G a transfer function matrix which describes the process dynamics by the elements g,y.
  • the vector U describes an input vector with variables possible to manipulate.
  • the internal states, ⁇ i.e. information (estimated or measured) directly from the refining zone plays a vital role to describe how to find improved strategies for process control.
  • Tf states obtained from measurement devices outside the refiners or estimated from mathematical models. These states are normally possible to sample relatively fast but still at a slower sampling rate compared with the internal states.
  • Other external states, Q typically representing measured pulp quality that may only be sampled at a much slower sampling rate, will be important to follow as well. All states which can be controlled are elements in the state vector x, Le.
  • each component of the state vector x may in turn be a vector.
  • the relationship between the input vector «, and the state vector x,- may be described by a set of nonlinear differential equations characterized by a vector valued nonlinear function/-;
  • the input vector can vary in size dependent on the type of refiner studied but could typically be represented by chip or pulp production flow, dilution water flow, and plate gap (or means to influence the plate gap such as hydraulic pressure or alternatively an electro- mechanic force).
  • the inlet pressure in the pulp feeding system is possible to manipulate.
  • typical internal states to be used in this invention can be described as e.g. temperature in the refining zone, pressure or force measurements in the refining zone or states estimated from physical or empirical models by using different software solvers. Examples of that is the predicted forces along the radius in the refining zone, estimated consistency in the zone, mean fiber residence time in different regions of the zone, plate gap, pulp quality from the refining zone et cetera. Pulp quality estimations can be valuable when comparing them with the measured pulp quality from the downstream analyzers.
  • the variables can refer to a set of soft sensors (or estimates from the models) describing the hidden process variables in the refining zone. In this model e.g.
  • temperature measurements can be used to get proper estimates of the energy balance which indirectly together with zone specific data give information normally difficult to measure directly, like the residence time, defibration/fibrillation work et cetera.
  • the variables can also be referred to as estimates obtained from an algorithm which uses spatial refining zone measurements to find some optimum, like the position for the maximum temperature in the refining zone which can be controlled by e.g. P in ⁇ et as described by Sikter [6].
  • Typical examples of external states which may be measured relatively fast outside the refining zone but slower than the internal states, will be the blow-line consistency, pressure, motor load et cetera. Such external states can also be estimated by a mathematical model. Other typical external states, which are only possible to sample much more slowly are placed in the vector Q. Such states are naturally the pulp quality variables CSF, the mean fiber length and shives et cetera which are measured downstream the refiners. If pulp quality variables are estimated from ordinary system identification procedures, e.g. using ARMAX models, to be used as input to the feedback control, such estimated variables will be placed in the vector ⁇ as the sampling rate will be fast enough.
  • the main variables to be controlled are obtained from the refining zone, i.e. not from the traditional concepts based on motor load or specific energy control.
  • the essence will be that compared with the traditional concept soft sensors and measurements from the refining zone provide information which can be used almost momentarily.
  • the consistency measured in the blow line can be used, if available, but the spatial consistency, which is available from the models, is to be preferred.
  • a model for the whole line can be constructed by combining the individual refiner models. For example, neglecting the mixing effect of the blow-line and only taking the time-delay D 1 into account (which is typically in the order of 5-10 s) we have
  • the present invention describes a way, using among other things temperature and/or pressure measurements directly in the refining zone, to control and optimize process conditions in refiners to improve energy efficiency and pulp quality.
  • the procedure means that the internal states, represented by temperature and/or pressure measurements, are primarily used to minimize the variations in pulp quality or energy consumption. Thanks to the availability of the internal states for use in the feedback system, the number of interaction elements can be minimized in the model based control.
  • the present invention presents the solution to the problems described, and concerns use of robust temperature and/or pressure measurements in combination with available measurement signals from the process together with a mathematical model to control both pulp quality and energy input to refiners much faster than what is the case today.
  • the principle advantage of the present invention is that thanks to measuring internal states such as temperature and/or pressure directly in the refining zone a faster control response may be produced of variables that better correlate to the final pulp quality than in traditional refiner control concepts.
  • the present invention also provides a significant improvement over the prior art by introducing model based optimization involving internal states of the refiner.
  • the method a) involves the temperature (and possibly force) measurements in the refiner, but not necessarily the motor load. More importantly b) it treats the whole two-stage refiner line as one (multi-rate) optimal control problem, which is described in more detail below.
  • a computer program, and a computer program recorded on a computer-readable medium is disclosed in another aspect of the invention.
  • Figure 1 shows a schematic block diagram of a method and system for controlling a TMP pulp refining process comprising a first refiner, according to an embodiment of the invention
  • Figure 2 shows the invention according to Figure 1 in which the diagram also shows a process comprising two refiners, according to an embodiment of the invention
  • Figure 3 shows a schematic flowchart of the invention according to Figure 1 or Figure 2 and in particular steps for carrying out a method according to an embodiment of the invention.
  • Figure 4 shows a schematic diagram for a known primary refiner
  • Figure 5 shows a known refiner grinding plate arranged with temperature or pressure sensors
  • Figure 6 shows a known array of temperature sensors (or pressure sensors) arranged on a refiner plate.
  • FIG. 1 shows a schematic diagram for a method of controlling a TMP pulp refiner.
  • the diagram shows a process with a single refiner 33, and a first control unit 32.
  • One or more setpoints 30 are input to the first control unit or control optimiser 32, or similar device with the same function.
  • the first control unit, the control optimiser is arranged to manipulate external process variables such as the hydraulic pressure P hy ⁇ - pressing together the refiner plates, flow of wood chips 5fl 0W , indicated as F p and dilution water 2' indicated as F D ,as inputs to the process 33.
  • Refined pulp is produced from the process 33.
  • External variables 37 representing pulp consistency 37 from the process and quality Q from sampling unit 35 are input to a second control unit, a state estimator 39.
  • ⁇ ⁇ is the force (or soft sensor of force) measured inside the refiner, Ti an array of temperature measurements along the radius inside the refiner, C; the blow-line consistency and Q] a vector of pulp quality variables such as Canadian standard freeness CSF and mean fiber length MFL.
  • ⁇ i or 7 / is to use the pressure Pi inside the refiner as a state variable.
  • uj and xj may be described by a set of nonlinear differential equations characterized by a vector valued nonlinear function/; ;
  • the main dynamics of the refiner are those for the actuation and sensing (more about sensing further below). Denoting the output from the controller by u !c the following linear differential equations approximately describe the inputs to the refining zone
  • the time constant ⁇ is roughly equal for all inputs and typically in the order of 1-5 seconds.
  • the relationship may be described by Laplace transforms and transfer functions as
  • FIG. 2 shows a schematic block diagram for a method of controlling a TMP pulp refiner line.
  • the diagram shows a process with a first refiner 33, and a second refiner 34, which are preferably arranged as a primary and a secondary refiner.
  • a first control unit or control optimiser 32 is supplied with one or more setpoints 30 to the first control unit or, or similar device with the same function.
  • the first control unit, the control optimiser is arranged to manipulate external process variables such as the hydraulic pressure P hyd r- pressing together the refiner plates, flow of wood chips 5 f i ow , and dilution water 2' as inputs to the first refiner 33; and hydraulic pressure P h y dr and dilution water 2' to the secondary refiner.
  • Pulp from the first refiner is led to the second refiner 34 through a blowline (not shown).
  • Refined pulp P is produced from the secondary refiner 34.
  • the refined pulp is sampled to measure one or more quality parameters Q.
  • External variables 37 representing pulp consistency (C) from the primary refiner and quality 38 (Q) from sampling unit 35 are input to a second control unit, a state estimator 39.
  • Internal values representing a temperature profile or a pressure profile from inside the refiner at Tl (primary) 36 and T2 (secondary) 36" using a sensors as shown 21 in Fig 6, are fed to the state estimator 39.
  • the state estimator calculates and sends a state estimation x to the first control unit, the control optimiser 32.
  • control optimisation the estimated state is used as a starting point to calculate the future trajectories of all state variables based on the process model.
  • the setpoints are then compared with the model outputs to obtain a control error. This control error is minimised with the future changes of the manipulated variables as free variables in the optimisation.
  • blow-line between the primary and secondary refiners is considered static
  • T 1 and T 2 are the temperature measurements (possibly vector valued) in primary and secondary refiner, respectively, C 1 the measured blow-line consistency out of the primary refiner and Q 2 the pulp quality after the secondary refiner.
  • all signals may be measured every second except the final pulp quality Q 2 which is measured using a sampling analyzer equipment, typically needing 5 minutes per sample.
  • the same equipment may serve several measurement points why a sampling interval in practice often is 20-30 minutes. The measurement is often preceded by a latency chest, which then acts like an anti-aliasing filter.
  • DAE Differential and Algebraic Equations
  • the optimization target is to the best estimate of all states of the refiner using the available measurements. This can be done using a Kalman filter [7] (or if the model is nonlinear extended Kalman filter) where a stochastic modelling of the process and measurement noises is deployed. Alternatively we may apply so-called moving horizon estimation [8].
  • moving horizon estimation corresponds to minimizing
  • R 1 and R 2 are weight matrices used for tuning of the estimator, which have a similar interpretation and importance as the estimate and noise covariance matrices in Kalman filtering.
  • this optimization is typically done over a horizon [ t - MT S , t ], if t is the current measurement time. Since this time interval is in the past we assume access to historic values of the applied manipulated variables u k .
  • the first penalty term in the criterion is to create a link from one optimization window to the next, where x k _ M denotes the estimate for this particular time instant from the optimization run at the previous cycle. What makes this problem nonstandard, though, is that not all elements of y k will be available at all sampling instants, creating a multi-rate state estimation problem.
  • the state estimation produces a starting point for the optimization of future manipulated variables, where future setpoints r k are compared with some subset or combination of the state variables m(x k ) calculated by use of the mathematical process model.
  • a formulation of the optimization objective may be, for example,
  • nonlinear model is used as an equality constraint, leading to a nonlinear model predictive control problem.
  • model is linearized, resulting in a model of the form
  • Figure 3 shows a simplified flowchart for one or more methods according to another aspect of the invention.
  • the figure shows that the method begins 50 by initializing the time t. Each cycle starts by retrieving the measured values from the sensors 52. These measured values (and possibly also historic values in a window of length M) are then used together with the process model to calculate 53 a state estimate x . This state estimate is then used as a starting point in the forward optimisation which produces a sequence of changes 55 to the manipulated variables over a future horizon of length N u . Applying the receding horizon principle only the first change of manipulated variables is sent to the actuators 57; after which the time is incremented 58 and the procedure (52-57) is repeated.
  • the methods of condition monitoring as described above and elsewhere in this specification may be carried out by a computer application comprising computer program elements or software code which, when loaded in a processor or computer, causes the computer or processor to carry out the method steps.
  • the method may be described as comprising:
  • the methods of controlling and optimizing as described above and elsewhere in this specification may be carried out by a computer application comprising computer program elements or software code which, when loaded in a processor or computer, causes the computer or processor to carry out the method steps.
  • the functions of the methods such as the method shown in Figure 3, may be carried out by processing digital functions, algorithms and/or computer programs and/or by analogue components or analogue circuits or by a combination of both digital and analogue functions.
  • the methods of the invention may, as previously described, be carried out by means of one or more computer programs comprising computer program code or software portions running on a computer or a processor.
  • the microprocessor (or processors) comprises a central processing unit CPU performing the steps of the method according to one or more facets of the invention. This is performed with the aid of one or more said computer programs, such as, which are stored at least in part in memory and/or and as such accessible by the one or more processors.
  • the or each processor may be in a control unit, or as a separate control optimizer unit or in a state estimator unit or part thereof, or may as well run in a local or central control system in a local or distributed computerised control system. It is to be understood that said computer programs may also be run on one or more general purpose industrial microprocessors or computers instead of one or more specially adapted computers or processors.
  • the computer program comprises computer program code elements or software code portions that make the computer perform the method using equations, algorithms, data, stored values and calculations previously described.
  • a part of the program may be stored in a processor as above, but also in a ROM, RAM, PROM, EPROM or EEPROM chip or similar memory means.
  • the program in part or in whole may also be stored on, or in, other suitable computer readable medium such as a magnetic disk, CD-ROM or DVD disk, hard disk, magneto-optical memory storage means, in volatile memory, in flash memory, as firmware, stored on a data server or on one or more arrays of data servers.
  • Other known and suitable media, including removable memory media and other removable flash memories, hard drives etc. may also be used.
  • the computer programs described may also be arranged in part as a distributed application capable of running on several different computers or computer systems at more or less the same time.
  • Programs as well as data such as start positions, or flag-related information may be made available for retrieval, delivery or, in the case of programs, execution over the Internet.
  • Data may be accessed by means of any of: OPC, OPC servers, an Object Request Broker such as COM, DCOM or CORBA, a web service.

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  • Paper (AREA)

Abstract

L'invention porte sur un procédé de commande d'une section de raffinage thermomécanique de pâte (TMP). La section de traitement comporte au moins un premier raffineur comportant une pluralité de capteurs disposés dans une position prédéterminée sur une plaque de raffineur de l'au moins un premier raffineur. Le procédé comprend la mesure ou différemment l'estimation d'une ou plusieurs variables de traitement représentant des états externes à l'extérieur du raffineur, selon la formule (I) pour ladite section de traitement et la mesure ou différemment l'estimation d'une ou plusieurs valeurs représentant un ou plusieurs états internes, selon la formule (II) à l'intérieur dudit au moins un premier raffineur, et le calcul d'une modification pour ladite au moins une variable manipulée (u 1) pour ledit au moins un raffineur à l'aide de ladite mesure d'un état interne selon la formule (II) dudit au moins un raffineur, et une mesure desdits au moins un état externe de traitement selon la formule (I), pour ladite section de traitement à l'aide d'un modèle de traitement mathématique.
EP08875398.3A 2008-12-01 2008-12-01 Procédure et système de commande d'un raffineur afin d'améliorer le rendement en énergie et la qualité de pâte Active EP2370628B1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2008/066556 WO2010063310A1 (fr) 2008-12-01 2008-12-01 Procédure et système de commande d'un raffineur afin d'améliorer le rendement en énergie et la qualité de pâte

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EP2370628A1 true EP2370628A1 (fr) 2011-10-05
EP2370628B1 EP2370628B1 (fr) 2014-07-02

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EP (1) EP2370628B1 (fr)
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CN104155958A (zh) * 2014-08-25 2014-11-19 理程自动化技术（天津）有限公司 化学机械浆工艺的优化控制系统
CN112547293B (zh) * 2020-11-04 2022-05-17 宜春钽铌矿有限公司 一种棒磨机负荷智能控制的方法
CN113435781A (zh) * 2021-07-14 2021-09-24 国网福建省电力有限公司检修分公司 设备运行状态辅助判断方法及系统

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SE407952B (sv) * 1976-01-30 1979-04-30 Defibrator Ab Sett och anordning for malning av fiberhaltiga material
US4661911A (en) * 1985-01-31 1987-04-28 Beloit Corporation Adaptive constant refiner intensity control
SE9403743L (sv) * 1994-11-02 1996-05-03 Anders Karlstroem System för att kontinuerligt mäta tryck och temperatur i malzonen hos raffinörer
SE506687C2 (sv) * 1996-04-15 1998-02-02 Anders Karlstroem Förfarande och anordning för styrning av malningsförloppet i en raffinör
JP4245272B2 (ja) * 1997-10-09 2009-03-25 サーモ・ブラック・クローソン・インコーポレーテッド 製紙用パルプ精製機制御装置および方法
US7381303B2 (en) * 2004-04-27 2008-06-03 Honeywell International Inc. System and method for controlling a thermo-mechanical wood pulp refiner

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Title
See references of WO2010063310A1 *

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CN102227532A (zh) 2011-10-26
EP2370628B1 (fr) 2014-07-02
WO2010063310A1 (fr) 2010-06-10
CN102227532B (zh) 2014-03-19
CA2744638C (fr) 2016-01-26
CA2744638A1 (fr) 2010-06-10

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