EP1785525A1

EP1785525A1 - Measurement of paper/board process

Info

Publication number: EP1785525A1
Application number: EP05110706A
Authority: EP
Inventors: Juan Carlos Cecchini; Petri Jetsu; Antti Poikolainen
Original assignee: Metso Automation Oy
Current assignee: Valmet Automation Oy
Priority date: 2005-11-14
Filing date: 2005-11-14
Publication date: 2007-05-16
Anticipated expiration: 2025-11-14
Also published as: EP1785525B1

Abstract

A method of estimating a quality of suspension with solid elements in water in a process of paper/board production is presented. At least one sub-process in the process of paper/board production is performed, each sub-process adjusting at least one property of the suspension. A measurement of a distribution of solid elements in the suspension before and after a sub-process is performed using a measurement unit (220). The measurement unit (220) may estimate and control a quality of the suspension as a function of the distribution of solid elements in the suspension before and after the sub-process.

Description

Field

The invention relates to a process of paper/board production.

Background

In a paper mill, samples of furnish can be taken from various places of the process for measurements to be made on-line, in-line, based on sampling or in a laboratory (off-line). The measurement results show certain properties of the furnish and if the furnish does not meet the desired target properties, the process can be adjusted.
However, the present measurements do not give good enough pieces of information on solid elements and their size distributions in furnish to be utilized, for example, in the prediction of formation and the quality of the end product in the process of paper/board production. Formation, for instance, depends on several factors such as raw material characteristics, mechanical actions on furnish and chemical treatments. Still, present solutions are poor to predict and control the formation.
The control of many sub-processes is also poor, since the effects of various additions of substances, such as chemicals and stocks, to furnish are not accurately known nor measured.

Brief description of the invention

An object of the invention is to provide improved methods and improved apparatuses for measurement of a paper/board process.
According to an aspect of the invention, there is provided a method of estimating a quality of suspension with solid elements in water in a process of paper/board production, the method comprising performing at least one sub-process in the process of paper/board production, each sub-process adjusting at least one property of the suspension. The method further comprises performing a measurement of a distribution of solid elements in the suspension before a sub-process; performing a measurement of a distribution of solid elements in the suspension after the sub-process; and estimating a quality of the suspension as a function of the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process.
According to another aspect of the invention, there is provided a method of predicting formation in a process of paper/board production, the method comprising performing at least one sub-process in the process of paper/board production, each sub-process adjusting at least one property of a suspension with solid elements in water. The method further comprises performing a measurement of a distribution of solid elements in the suspension before a sub-process; performing a measurement of a distribution of solid elements in the suspension after the sub-process; and predicting formation to be formed in a former as a function of the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process.
According to another aspect of the invention, there is provided a method of predicting floc strength in a process of paper/board production, the method comprising performing at least one sub-process in the process of paper/board production, each sub-process adjusting at least one property of a suspension with solid elements in water. The method further comprises performing a measurement of a distribution of solid elements in the suspension before a sub-process; performing a measurement of a distribution of solid elements in the suspension after the sub-process; and predicting floc strength to be formed as a function of the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process.
According to another aspect of the invention, there is provided a method of controlling a process of paper/board production, the method comprising performing at least one sub-process of the process of paper/board production on suspension with solid elements in water, each sub-process adjusting at least one property of the suspension. The method further comprises performing a measurement of a distribution of solid elements in the suspension before a sub-process; performing a measurement of a distribution of solid elements in the suspension after the sub-process; and controlling at least one sub-process as a function of a difference between the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process.
According to another aspect of the invention, there is provided a method of predicting porosity in a process of paper/board production, the method comprising performing at least one sub-process in the process of paper/board production, each sub-process adjusting at least one property of a suspension with solid elements in water. The method further comprises performing a measurement of a distribution of solid elements in the suspension before a sub-process; performing a measurement of a distribution of solid elements in the suspension after the sub-process; and predicting porosity to be formed as a function of the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process.
According to another aspect of the invention, there is provided an apparatus for estimating a quality of suspension with solid elements in water in a process of paper/board production, the process comprising at least one sub-process adjusting at least one property of the suspension. The apparatus comprises a measuring unit configured to perform a measurement of a distribution of solid elements in the suspension before a sub-process, to perform a measurement of a distribution of solid elements in the suspension after the sub-process, and to estimate a quality of the suspension as a function of the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process.
According to another aspect of the invention, there is provided an apparatus for predicting formation of suspension with solid elements in water in a process of paper/board production, the process comprising at least one sub-process adjusting at least one property of the suspension. The apparatus comprises a measuring unit configured to perform a measurement of a distribution of solid elements in the suspension before a sub-process, to perform a measurement of a distribution of solid elements in the suspension after the sub-process, and to predict formation to be formed in a former as a function of the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process. According to another aspect of the invention, there is provided an apparatus for predicting floc strength of suspension with solid elements in water in a process of paper/board production, the process comprising at least one sub-process adjusting at least one property of the suspension. The apparatus comprises a measuring unit configured to perform a measurement of a distribution of solid elements in the suspension before a sub-process, to perform a measurement of a distribution of solid elements in the suspension after the sub-process, and to predict floc strength to be formed as a function of the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process.
According to another aspect of the invention, there is provided an apparatus for controlling a process of paper/board production where suspension with solid elements in water is processed in at least one sub-process adjusting at least one property of the suspension. The apparatus comprises a measuring unit configured to perform a measurement of a distribution of solid elements in the suspension before a sub-process, to perform a measurement of a distribution of solid elements in the suspension after the sub-process, and a controller configured to control at least one sub-process as a function of a difference between the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process.
According to another aspect of the invention, there is provided an apparatus for predicting porosity of suspension with solid elements in water in a process of paper/board production, the process comprising at least one sub-process adjusting at least one property of the suspension. The apparatus comprises a measuring unit configured to perform a measurement of a distribution of solid elements in the suspension before a sub-process, to perform a measurement of a distribution of solid elements in the suspension after the sub-process, and to predict porosity to be formed in the end product as a function of the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process.
The invention provides several advantages. The distribution of solid elements of the suspension can be measured effectively in a plurality of sections of the process of paper/board production and the measurement results can be, if so desired, used to predict or control the quality of the web and the end product.

List of drawings

In the following, the invention will be described in greater detail with reference to the embodiments and the accompanying drawings, in which

Figure 1 shows a block diagram of a paper machine;
Figure 2 illustrates measurements made before and after a sub-process.
Figure 3 illustrates measurements relating to a blending chest,
Figure 4 illustrates measurements made in a former,
Figure 5 illustrates a shift in size distribution of large solid elements in suspension treated with a refiner,
Figure 6 illustrates a shift in size distribution of small solid elements in suspension treated with a refiner,
Figure 7 illustrates a flow chart of a method of estimating quality.
Figure 8 illustrates a flow chart of a method of predicting formation.
Figure 9 illustrates a flow chart of a method of controlling a process.
Figure 10 illustrates a flow chart of a method of predicting floc strength, and
Figure 11 illustrates a flow chart of a method of predicting porosity.

Description of embodiments

With reference to Figure 1, examine an example of a general structure of a paper machine. Each type of pulp fed to the paper making process can be refined in separate refiners 100 to 104. The refiners can be cylindrical refiners or conical/double discs. After a desired treatment in each refiner 100 to 104, the output may be fed further into the paper making process through valves 106 to 110. The valves may be adjusted adaptively such that a desired amount of each type of pulp can be metered to the process. The amount of pulp metered may be controlled, for example, by a basis weight control or a grade change program.
If many kinds of pulp are fed into the process, the combination of each pulp proceeds further to a blending chest 112 and a machine chest 114. In the blending chest 112 kraft and broke may be added to the pulp. Broke and kraft can be determined as papers that are re-pulped in this manner. In the machine chest 114, an optional dosage of fillers like PCC and/or GCC (PCC = Precipitated Calcium Carbonate, GCC = Ground Calcium Carbonate) as well as kaolin or clay according to the paper grade may be added to the pulp, for example, for improving formation, having effect on porosity and/or increasing floc strength and possibly enhancing optical properties of the end product. The blending chest 112 and the machine chest 114 can also be replaced by a separate mixing reactor (not shown in Figure 1).
After the machine chest 114, the name of pulp often changes to furnish which may proceed into a wire pit 116, where water may be mixed from the short circulation into the furnish to achieve the required consistency (dashed line from a former 126 to the wire pit silo 116). However, both pulp and furnish can be considered to be suspension with solid elements in water. The solid elements may be fibers such as wood fibers, fiber fines, particles or fillers. Dissolved colloids promote the conformation of flocs which are enhanced with dosage of chemical additives.
Sand, air and other coarse materials can be removed from the furnish using cleaning devices 118, such as a sentrifugal cleaner, a deculator and a machine screen, and the furnish can pumped by a pump 120 to the headbox 122.
After the deculator and before the pump 120 of an optional dosage/addition point for micro/nano particles, TA, such as kaolin, calcium carbonate, talc, chalk, titanium dioxide, diatomite, can be added to the furnish. In the same referred location or after the pump and before the screen or after the screen and before the headbox, a retention aid RA, such as inorganic, inartificial organic or synthetic water-soluble polymers to name a few of TA and RA, can be added and mixed to the furnish in a desired manner. Metering each of these can be controlled by adaptively adjustable valves 124 to 126 or by adaptive adjustable dosing pumps.
The purpose of the micro/nano particles is to improve, for example, the formation, surface properties, opacity, brightness, lightness and printing quality as well as to reduce the manufacturing costs. Retention aids RA, for their part, may improve, for instance, the retention of the fines and fillers as well as speed up dewatering in a desired manner.
From the headbox 122, the furnish may be fed through the slice opening 128 of the headbox to a former 130, which may be a fourdrinier in slow paper machines, a hybrid former in medium speed paper machines and a gap former in fast paper machines. In the former 130, water drains out of the web, and ash, fines and fibres are led to the short circulation. In the former 130, the furnish is fed as a fibre web onto a wire, and the web can be preliminarily formed by fast water removal and pressed in a press 132. The fibre web can also be primarily dried in dryers 134 and 136. In addition, there is usually at least one measuring beam (not shown in Figure 1) for measuring, for instance, the moisture MOI of the fibre web, the ash content ASH and basis weight BW of the paper being made. The paper machine, which in this application refers to both paper and board machines, may also comprise a reel and size presses or a calender, for instance, but these parts are not shown in Figure 1. The general operation of a paper machine is known per se to a person skilled in the art.
In the present solution, measurements can be made in at least two different places in the process of paper/board production. Between these at least two places, the suspension with solid elements in water is processed by a sub-process of the process of paper/board production. The measurement points are marked with letter "M or M_F" in Figure 1.
Figure 2 illustrates the measurements made before the head box 122. Let us assume that two components of retention aids are added somewhere after the deculator and before the headbox 116. In general, the order and the number of the added substances may be arbitrary.
Each addition can be considered a sub-process in the process of paper/board production. The number of sub-processes may be one or vary from 1 to N, where N is a positive integer larger than one. The furnish is measured before the addition of retention aids and/or micro particles. The measurement 200 may measure a distribution of solid elements in the suspension before the sub-process(es). Then a first sub-process 202 relating to an addition of a first component of the retention aid is performed. The first component may be a polymer or micro particles. A pump 204 may be used to proceed and mix the furnish. The first component may be added before or after the pump 204. A measurement 206 measures a distribution of solid elements in the suspension after the first sub-process.
Screening by a screen 208 may improve the mixing of the first component of the retention aid system as well reduce the size of the flocs by shear forces rate at this stage.
Then a second sub-process 210 relating to an addition of a second component of the retention aid is performed (if dual component or micro particle retention aid system is in use). The second component may be a polymer or micro particles. If a polymer is added first, micro particles may be added second. A measurement 212 measures a distribution of solid elements in the suspension after the second sub-process.
The measurements 200, 206 and 212 may be on-line measurements where a sample from the furnish in a pipe 218 is taken using a sampler 250 and fed to a measuring unit 220, which may output a signal to a control unit 222.
The measuring unit 220 may have several operational principles. In an embodiment, the measuring unit may form an image of the sample of the furnish such that the solid elements included in the suspension can be recognized in the image. A numerical value, which may be called a parameter, for each processable property of the solid elements can be formed by an image processing program run in the measuring unit. Additionally to a parameter describing a distribution of the sizes of the solid elements, a parameter describing entanglement of fibers, such as the number of crossing points, may be formed. The sample may be diluted in a possible sampler 250 before forming the image such that the consistency of the sample is proper for the image. The image can be formed by taking a picture, for example, using a CCD-camera (Charge Coupled Device) or the like.
In an embodiment the measuring unit 220 may have a fractionating hose 250 to separate solid elements of different sizes into fractions with a good performance. The fractionating hose 250 can be used to separate different fractions such as shives, flocs, fibers, fines and fillers.
In an embodiment, the measuring unit 220 may be an optical apparatus which utilizes absorption, attenuation, scattering and/or depolarisation of optical radiation interacting with small particles. Similarly to the previous example, a numerical value for each processable property of the solid elements can be formed by an image processing program run in the measuring unit 220. A typical parameter in this kind of measurement is a parameter describing the size distribution of the solid elements.
In an embodiment, the measuring unit 220 may also measure consistency of small samples such that a possible agglomeration of solid material in the suspension, such as a floc, may be recognized from the average consistency of the sample. This kind of measurement can give an estimate of distribution of the solid elements in the suspension. A shift in the particle distribution indicates that particles may change their sizes by growing or shrinking in the sub-process (depending on the type of retention aid component added, polymer or micro particles respectively). The measurement can be an optical measurement. If the consistency measurement is complemented with a CCD camera, an image analysis is required to characterize the flocs conformation.
The measuring unit 220 may predict formation and/or porosity to be formed in a former 130 as a function of the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process. The distributions before and after a sub-process can be parameters in a prediction model, which may be a mathematical expression describing dependency between distributions and the formation and/or porosity. The prediction model may also take into account the number of crossing points in a floc.
It can be assumed that cationic polymer enhance retention of fines as well as promote further entanglement of fibers resulting in flocculation. The flocs are assumed to become stronger when water is removed and tighter when a suitable polymer or a combination of polymer and micro/nano-particle is added. If shear forces (i.e. mechanical refining) are applied, flocs tend to become smaller or smoother.
A base of a model describing the behaviour of flocs with respect to certain sub-processes can be as follows. When a suitable polymer is added to suspension, flocs increase in size.
When a suitable polymer is added to suspension and shear forces are applied, flocs decrease in size.
When a suitable polymer and microparticles are added to suspension, flocs decrease in size but also increase in number.
When a suitable polymer and microparticles are added and shear forces are applied, flocs decrease strongly in size (more than without shear forces) but increase in number.
When floc diameters and structures are measured, it is possible to predict or to estimate formation, floc strength and/or porosity. The floc structure may relate, for example, to fiber crossings. These measurements also enable to predict or to estimate the quality of the end product (paper or board). The measurements further enable control of formation, floc strength and/or porosity and the quality of the end product.
The measured floc sizes and structures can be linked to formation patterns, such as cloudy, granny, smooth, etc., and their numerical values. For example, beta formation decreases when formation improves.
The mathematical expression of the prediction model can be related to a formation factor FF which describes the quality of formation and is also related to the quality of the end product (paper or board). The expression may be of the form: $FF = K * f (dfloc, fibfloc, fibcross, Ncr, ChDF),$

where K is a constant of proportion to correct units and lead the FF to a numerical range between 1 and 0, f is a function whose the arguments are the parameters dfloc, fibfloc, fibcross, Ncr, ChDF, dfloc is a floc diameter (may be limited to 1.5 times the fiber length), fibfloc is the number of fibers included in the conformation of a floc, fibcross is the number of crossing points in a floc, Ncr is a crowding number (π/6)*C*(L²/w), ChDF is a chemical dosage factor (k(Pd/MPd)), π is about 3.1415926, C is a sample consistency, L is a weighted fiber length, w is a wall thickness, k is a factor correcting the rate of polymer to micro/nano-particle dosage according to a system defined reference, Pd is a polymer dosage, MPd is a micro/nano-particle dosage. The prediction of formation can be notified to the operator of the paper mill.
Alternatively or additionally, the information on distributions before and after each sub-process can be utilized to control at least one sub-process in the process of paper/board production. The sub-process that is controlled can be the same as the measured one or a different one.
Figure 3 illustrates an embodiment relating to the blending chest 112. In this example, kraft and broke are added to the pulp in the blending chest 112. The main pulp could be considered to form from one fresh pulp feed or M fresh pulps feeds to the machine chest, where M is a positive integer larger than 2. Similarly to the example in Figure 2, the measuring unit 220 may perform on-line measurements 300 to 306 of pulp, kraft and broke before and after they enter the sub-processes (addition of kraft can be considered one sub-process and addition of broke can be considered another sub-process) in the blending chest 112. The measurements relate to a distribution of solid elements in the suspension in a similar manner to that described in Figure 2. Finally, a quality of the suspension may be estimated as a function of the distribution of solid elements in the suspension before and after the sub-process(es). At least one sub-process can be taken into account but also many or all sub-processes can be utilized. The estimation of quality can be based on a mathematical model which includes the superposition of mass fractions and the rates of fibre fines included in each component or sub-process. A mass fraction and fibre fines amount can be defined as a reference and the blending can be controlled according to the reference and the measurements.
The model can be presented as follows: $M_{T} = \sum_{i = 1}^{P} M_{i},$
$Q_{T} = \sum_{i = 1}^{P} Q_{i},$
$G_{T} = \sum_{i = 1}^{P} Q_{i},$

where M_i is a mass flow of current i, Q_i is a volumetric flow of a current i, G_T is C_iQ_i, where C_i is consistency of current i. ${Abs}_{T} = \sum_{i = 1}^{P} F (G_{i}) {Abs}_{i},$
${Depo}_{T} = \sum_{i = 1}^{P} F (G_{i}) {Depo}_{i},$

where Abs_i is a fines fraction distribution in a current i and Depo_i is a long/coarse fraction distribution in a current i. In a similar manner, Abs_m is a fines fraction distribution is a measured current i and Depo_m is a long/coarse fraction distribution is a measured current i. The measurement can take place after the blending chest 112. A difference between a target fraction distribution Abs_T and a measured fraction distribution Abs_m can be expressed as error E which can be expressed, for example, as follows: $E = {Abs}_{T} - {Abs}_{m},$

which can be utilized in the control.
Also in this example, the information on distributions before and after each sub-process can be utilized to control at least one sub-process in the process of paper/board production. The sub-process that is controlled by the controller 222 receiving a signal relating to measurements from the measurement unit 220 can be the same as the measured one or a different one.
In Figure 3 there is also shown a sub-process of adding and mixing polymer to a sample of the furnish. The effect of this sub-process can be determined from measurements 306 and 308 made before and after the sub-process. For example, the flocculation tendency of the sample can be determined before or after mixing the furnish with filler(s) in the machine chest 114. Thus, the machine chest 114 operation can be controlled by these measurements, which also indicates the possible range of retention aid dosage.
The control may be performed such that a retention polymer can be added according to the retention needs and the ratio between retention polymer and micro particles can be formed according to the formation needs. As formation can be predicted, the additions of the components to the furnish can be determined using the predicting model. If predicted formation and measured formation in the ready made paper do not meet, the model can be modified (model may be adaptive) or a feedback is used to correct the model prediction methods in a similar manner to a known MP (Model Predictive) control technology.
Figure 4 illustrates measurements M_F made in the former 130. A heavy drainage and particle losses take place in the former 130. Moreover, filler distribution changes and a considerable filler loss takes place at different vacuum units and loadable blade area. By measuring these changes and losses it is possible to control, for example, the dosage of retention aids.
In this example, the measuring unit measures the drainage from at least two places in a multifoil shoe (or a vacuum chamber) 400, a loadable blade unit 402, a wire 404 and between a forming roll 406 and a breast roll 408. The rolls and their configuration/arrangement are not limited to those shown in Figure 4. The former 130 may not necessarily include a forming/sucking roll (BelBaie configuration BBV or a belshoe or an equivalent). The measurements made in at least two places may give information on distribution and changes in distribution of solid elements in the suspension on the wire 404. This information can be utilized in a similar manner as in the examples explained relating to the previous figures. For example, formation can be predicted, the quality of suspension and/or the end product can be estimated or at least one of the sub-processes can be controlled for achieving a proper papermaking suspension to evaluate fibre fines and filler particle losses. This may be utilized in a proper z-profile control of a paper web.
Figure 5 illustrates a possible kind of shift in the size distribution of large solid elements (mainly fibers) in suspension treated with a refiner. The signal strength is in y-axis and size is in x-axis, both in arbitrary scale. The depolarisation curve 500 measured before the treatment indicates a distribution that refers to larger solid elements in average than the depolarisation curve 502 relating to a distribution measured after the treatment. Note that the size of solid elements tend to decrease when the sub-process is an addition of a single polymer.
Figure 6 illustrates a possible kind of shift in the size distribution of small solid elements (mainly fines and other micro particles) in suspension treated with a refiner. The signal strength is in y-axis and size is in x-axis, both in arbitrary scale. The scattering curve 600 measured before the treatment indicates a distribution that refers to larger solid elements in average than the scattering curve 602 relating to a distribution measured after the treatment. Note also here that the size of solid elements tend to decrease when the sub-process is an addition of a single polymer.
Figure 7 illustrates a method of estimating a quality of suspension. In step 700, an on-line measurement of a distribution of solid elements in the suspension before a sub-process is performed. In step 702, an on-line measurement of a distribution of solid elements in the suspension after the sub-process is performed. In step 704, a quality of the suspension is estimated as a function of the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process.
Figure 8 illustrates a method of predicting formation. In step 800, an on-line measurement of a distribution of solid elements in the suspension before a sub-process is performed. In step 802, an on-line measurement of a distribution of solid elements in the suspension after the sub-process is performed. In step 804, formation to be formed in a former is predicted as a function of the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process.
Figure 9 illustrates a method of predicting floc strength in a process of paper/board production. In step 900, an on-line measurement of a distribution of solid elements in the suspension before a sub-process is performed. In step 902, an on-line measurement of a distribution of solid elements in the suspension after the sub-process is performed. In step 904, floc strength to be formed is predicted as a function of the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process.
Figure 10 illustrates a method of controlling a process of paper/board production. In step 1000, an on-line measurement of a distribution of solid elements in the suspension before a sub-process is performed. In step 1002, an on-line measurement of a distribution of solid elements in the suspension after the sub-process is performed. In step 1004, at least one sub-process is controlled as a function of a difference between the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process.
Figure 11 illustrates a method of predicting porosity in a process of paper/board production. In step 1100, an on-line measurement of a distribution of solid elements in the suspension before a sub-process is performed. In step 1102, an on-line measurement of a distribution of solid elements in the suspension after the sub-process is performed. In step 1104, porosity to be formed in the end product is predicted as a function of the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process.
The prediction model, the estimation and the control operations illustrated in Figures 7, 8, 9, 10 and 11 may be realized as a computer program. The computer program may be stored on a computer program distribution medium readable by a computer or a processor. The computer program medium may be, for example but not limited to, an electric, magnetic, optical, infrared or semiconductor system, device or transmission medium. The medium may be a computer readable medium, a program storage medium, a record medium, a computer readable memory, a random access memory, an erasable programmable read-only memory, a computer readable software distribution package, a computer readable signal, a computer readable telecommunications signal, and a computer readable compressed software package. Even though the invention is described above with reference to an example according to the accompanying drawings, it is clear that the invention is not restricted thereto but it can be modified in several ways within the scope of the appended claims.

Claims

A method of estimating a quality of suspension with solid elements in water in a process of paper/board production, the method comprising
performing at least one sub-process in the process of paper/board production, each sub-process adjusting at least one property of the suspension, characterized by
performing (700) a measurement (200, 206, 212, 300 to 308, 420 to 430) of a distribution of solid elements in the suspension before a sub-process;
performing (702) a measurement (200, 206, 212, 300 to 308, 420 to 430) of a distribution of solid elements in the suspension after the sub-process; and
estimating (704) a quality of the suspension as a function of the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process.
The method of claim 1, characterized by performing estimation of the quality by performing measurements (200, 206, 212, 300 to 308, 420 to 430) in at least two of the following sections of the paper/board production process: before refining, after refining, before a blending chest, after a blending chest, before polymer addition, after polymer addition, before adding micro particles, after adding micro particles, before a former, in at least one place in the former.
A method of predicting formation in a process of paper/board production, the method comprising
performing at least one sub-process in the process of paper/board production, each sub-process adjusting at least one property of a suspension with solid elements in water, characterized by
performing (800) a measurement of a distribution of solid elements in the suspension before a sub-process;
performing (802) a measurement of a distribution of solid elements in the suspension after the sub-process; and
predicting (804) formation to be formed in a former as a function of the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process.
The method of claim 3, characterized by performing prediction of formation by performing measurements in at least two of the following sections of paper/board production process: before refining, after refining, before blending chest, after blending chest, before polymer addition, after polymer addition, before adding micro particles, after adding micro particles, before a former, in at least one place in the former.
A method of predicting floc strength in a process of paper/board production, the method comprising
performing at least one sub-process in the process of paper/board production, each sub-process adjusting at least one property of a suspension with solid elements in water, characterized by
performing (900) a measurement of a distribution of solid elements in the suspension before a sub-process;
performing (902) a measurement of a distribution of solid elements in the suspension after the sub-process; and
predicting (904) floc strength to be formed as a function of the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process.
The method of claim 5, characterized by performing prediction of the floc strength by performing measurements in at least two of the following sections of the paper/board production process: before refining, after refining, before a blending chest, after a blending chest, before polymer addition, after polymer addition, before adding micro particles, after adding micro particles, before a former, in at least one place in the former.
A method of controlling a process of paper/board production, the method comprising
performing at least one sub-process of the process of paper/board production on suspension with solid elements in water, each sub-process adjusting at least one property of the suspension, characterized by
performing (1000) a measurement (200, 206, 212, 300 to 308, 420 to 430) of a distribution of solid elements in the suspension before a sub-process;
performing (1002) a measurement (200, 206, 212, 300 to 308, 420 to 430) of a distribution of solid elements in the suspension after the sub-process; and
controlling (1004) at least one sub-process as a function of a difference between the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process.
The method of claim 7, characterized by performing estimation of the quality by performing measurements (200, 206, 212, 300 to 308, 420 to 430) in at least two of the following sections of the paper/board production process: before refining, after refining, before a blending chest, after a blending chest, before polymer addition, after polymer addition, before adding micro particles, after adding micro particles, before a former, in at least one place in the former.
A method of predicting porosity in a process of paper/board production, the method comprising
performing at least one sub-process in the process of paper/board production, each sub-process adjusting at least one property of a suspension with solid elements in water, characterized by
performing (1100) a measurement of a distribution of solid elements in the suspension before a sub-process;
performing (1102) a measurement of a distribution of solid elements in the suspension after the sub-process; and
predicting (1104) porosity to be formed as a function of the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process.
The method of claim 8, characterized by performing prediction of the porosity by performing measurements in at least two of the following sections of the paper/board production process: before refining, after refining, before a blending chest, after a blending chest, before polymer addition, after polymer addition, before adding micro particles, after adding micro particles, before a former, in at least one place in the former.
The method of claim 7, characterized by performing a control of a sub-process which is the same as the sub-process measured before and after.
The method of claim 9, characterized by performing a sub-process in a blending chest (112) and controlling the sub-process blending raw material in the blending chest (112).
The method of claim 7, characterized by performing a control of a sub-process which is different from the sub-process measured before and after.
The method of claim 13, characterized by performing a sub-process of adding a polymer in the furnish and controlling a sub-process of metering micro particles in the furnish.
The method of claim 1, 3, 5, 7 or 9, characterized by separating solid elements in a fractionating hose (250) for the measurement (200, 206, 212, 300 to 308, 420 to 430) of a distribution of solid elements in the suspension.
The method of claim 1, 3, 5, 7 or 9, characterized by taking a sample from the suspension before and after a sub-process and diluting the samples to a desired consistency for the measurement.
The method of claim 1, 3, 5, 7 or 9, characterized by performing measurements (200, 206, 212, 300 to 308, 420 to 430) on the distribution of size of at least one of the following: flocs, fibers, fines.
An apparatus for estimating a quality of suspension with solid elements in water in a process of paper/board production, the process comprising at least one sub-process adjusting at least one property of the suspension, characterized in that the apparatus comprises
a measuring unit (220) configured to perform a measurement (200, 206, 212, 300 to 308, 420 to 430) of a distribution of solid elements in the suspension before a sub-process, to perform a measurement (200, 206, 212, 300 to 308, 420 to 430) of a distribution of solid elements in the suspension after the sub-process, and to estimate a quality of the suspension as a function of the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process.
The apparatus of claim 18, characterized in that the measuring unit (220) is configured to perform estimation of the quality by performing measurements (200, 206, 212, 300 to 308, 420 to 430) in at least two of the following sections of the paper/board production process: before refining, after refining, before a blending chest, after a blending chest, before polymer addition, after polymer addition, before adding micro particles, after adding micro particles, before a former, in at least one place in the former.
An apparatus for predicting formation of suspension with solid elements in water in a process of paper/board production, the process comprising at least one sub-process adjusting at least one property of the suspension, characterized in that the apparatus comprises
a measuring unit (220) configured to perform a measurement of a distribution of solid elements in the suspension before a sub-process, to perform a measurement of a distribution of solid elements in the suspension after the sub-process, and to predict formation to be formed in a former as a function of the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process.
The apparatus of claim 20, characterized in that the measuring unit (220) is configured to perform prediction of formation by performing measurements in at least two of the following sections of the paper/board production process: before refining, after refining, before a blending chest, after a blending chest, before polymer addition, after polymer addition, before adding micro particles, after adding micro particles, before a former, in at least one place in the former.
An apparatus for predicting floc strength of suspension with solid elements in water in a process of paper/board production, the process comprising at least one sub-process adjusting at least one property of the suspension, characterized in that the apparatus comprises
a measuring unit (220) configured to perform a measurement of a distribution of solid elements in the suspension before a sub-process, to perform a measurement of a distribution of solid elements in the suspension after the sub-process, and to predict floc strength to be formed as a function of the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process.
The apparatus of claim 22, characterized in that the measuring unit (220) is configured to perform predicting floc strength by performing measurements in at least two of the following sections of the paper/board production process: before refining, after refining, before a blending chest, after a blending chest, before polymer addition, after polymer addition, before adding micro particles, after adding micro particles, before a former, in at least one place in the former.
An apparatus for controlling a process of paper/board production where suspension with solid elements in water is processed in at least one sub-process adjusting at least one property of the suspension, characterized in that the apparatus comprises
a measuring unit (220) configured to perform a measurement (200, 206, 212, 300 to 308, 420 to 430) of a distribution of solid elements in the suspension before a sub-process, to perform a measurement (200, 206, 212, 300 to 308, 420 to 430) of a distribution of solid elements in the suspension after the sub-process, and
a controller (222) configured to control at least one sub-process as a function of a difference between the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process.
The apparatus of claim 22, characterized in that the measuring unit (220) is configured to perform estimation of the quality by performing measurements (200, 206, 212, 300 to 308, 420 to 430) in at least two of the following sections of the paper/board production process: before refining, after refining, before a blending chest, after a blending chest, before polymer addition, after polymer addition, before adding micro particles, after adding micro particles, before a former, in at least one place in the former.
An apparatus for predicting porosity of suspension with solid elements in water in a process of paper/board production, the process comprising at least one sub-process adjusting at least one property of the suspension, characterized in that the apparatus comprises
a measuring unit (220) configured to perform a measurement of a distribution of solid elements in the suspension before a sub-process, to perform a measurement of a distribution of solid elements in the suspension after the sub-process, and to predict porosity to be formed in the end product as a function of the distribution of solid elements in the suspension before the sub-process and the distribution of solid elements in the suspension after the sub-process.
The apparatus of claim 22, characterized in that the measuring unit (220) is configured to perform estimation of the quality by performing measurements (200, 206, 212, 300 to 308, 420 to 430) in at least two of the following sections of the paper/board production process: before refining, after refining, before a blending chest, after a blending chest, before polymer addition, after polymer addition, before adding micro particles, after adding micro particles, before a former, in at least one place in the former.
The apparatus of claim 22, characterized in that the controller (222) is configured to perform controlling a sub-process which is the same as the sub-process measured before and after.
The apparatus of claim 28, characterized in that the controller (222) is configured to perform a sub-process in a blending chest (112) and controlling the sub-process blending raw material in the blending chest (112).
The apparatus of claim 22, characterized in that the controller (222) is configured to perform controlling a sub-process which is different from the sub-process measured before and after.
The apparatus of claim 30, characterized in that the sub-process is adding a polymer in the furnish and the sub-process to be controlled is a sub-process of metering micro particles in the furnish.
The apparatus of claim 18, 20, 22, 24 or 26, characterized in that the measuring unit (220) includes a fractionating hose (250) for separating solid elements for the measurement (200, 206, 212, 300 to 308, 420 to 430) of a distribution of solid elements in the suspension.
The apparatus of claim 18, 20, 22, 24 or 26, characterized in that the apparatus includes a sampler (250) for taking a sample from the suspension before and after a sub-process and the sampler (250) is configured to dilute the samples to a desired consistency for the measurement.
The apparatus of claim 18, 20, 22, 24 or 26, characterized in that the measuring unit (220) is configured to perform measurements (200, 206, 212, 300 to 308, 420 to 430) on the distribution of size of at least one of the following: flocs, fibers, fines.