SE543483C2

SE543483C2 - Apparatus and method for measuring suspension and controlling process of suspension

Info

Publication number: SE543483C2
Application number: SE1950661A
Authority: SE
Inventors: Heikki Kumpulainen; Lasse Kauppinen; Timo Rantala
Original assignee: Valmet Automation Oy
Priority date: 2016-12-05
Filing date: 2017-12-04
Publication date: 2021-03-02
Also published as: CA3045229C; FI20165924L; AT521088A5; SE1950661A1; AT521088B1; FI127895B; AT521088A2; CN110050100A; CA3045229A1; WO2018104580A1

Abstract

An apparatus for measuring suspension comprises an image capturing device (100) for capturing at least one measurement image (200) of the suspension (102), the at least one measurement image presenting at least one solid particle (202); an information processing unit (112) which receives the at least one measurement image (200) and determines a state of attachment of the solid particles (202) of the suspension (102) to each other on the basis of pattern recognition applied to the at least one measurement image (200). The information processing unit (112) determines, on the basis of the state of the attachment of the solid particles (202) of the suspension (102), suspension data associated with at least one of the following: at least one process control chemical, at least one fiber property, at least one fines property, a relation between solid particles of different sizes, formation, and water content.

Description

Apparatus and method for measuring suspension and controllingprocess of suspension Field The invention relates to an apparatus and method for measuring suspension and Controlling process of suspension.

Background Dosing paper machine wet end Chemicals has typically been based onconventional wet-end Chemistry measurements by a charge analyzer, aconductivity meter, a pH meter or the like. Additionally, the dosing ofthe processcontrol Chemicals may depend on measurements of paper properties and papermachine runnability. The assumed effect of the process Control Chemicals on theprocess is based on laboratory studies and theories which are actually not wellCorrelated with the effect in real industrial processes. This is why a Controller ofpaper machine doesn't actually have information about the state of the process,and thus Cannot determine whether the process is at, Close to or far from theOptimum. Laboratory testing for Checking the system performance is alsoperformed rather seldom.

Water removal is another Critical parameter of a paper manufacturingprocess. However, this information is normally available through pulp freenessmeasurements and later on from machine water removal measurements whichare too late for the ideal determination of the state of a process.

Due to the facts, process machines often end up in situations far fromoptimal. This may lead to overdosing of the process Control Chemicals which is aproblem to the environment. Additionally, overdosing and/or wrong waterremoval information may Cause a runnability problem and deteriorate the qualityofthe end product.

Hence, there is a need to improve the measurements and the Control.

Brief description The present invention seeks to provide an improvement in themeasurements. According to an aspect of the present invention, there is providedan apparatus for measuring suspension as specified in claim 1.

According to another aspect ofthe present invention, there is providedan apparatus for controlling a process of suspension in claim According to another aspect ofthe present invention, there is provided a method for a process associated with suspension including solid particles in The invention has advantages. The measurement of attachment offibers together on the basis of images leads to savings in chemical use anddrainage and retention can be optimized. The measurement also makes itpossible to determine real time water removal, for example, from a headbox and increase controllability of the process.

List of drawings Example embodiments of the present invention are described below,by way of example only, with reference to the accompanying drawings, in which Figure 1 illustrates an example of apparatus for measuringsuspension; Figure 2A illustrates an example of a measurement image ofsuspension; Figure 2B illustrates an example of a fraction including the largestsolid particles of four fractions having no process control chemical; Figure ZC illustrates an example of a fraction including the secondlargest solid particles of the four fractions having no process control chemical; Figure 2D illustrates an example of a fraction including the thirdlargest solid particles of the four fractions having no process control chemical; Figure ZE illustrates an example of a fraction including the smallest solid particles of the four fractions having no process control chemical; Figure 3A illustrates an example of a fraction including the largestsolid particles of four fractions having at least one process control chemical; Figure 3B illustrates an example of a fraction including the secondlargest solid particles of the four fractions having at least one process controlchemical; Figure BC illustrates an example of a fraction including the thirdlargest solid particles of the four fractions having at least one process controlchemical; Figure 3D illustrates an example of a fraction including the smallestsolid particles ofthe four fractions having at least one process control chemical; Figure 4 illustrates an example of a block chart of at least oneprocessor and at least one memory; Figure 5 illustrates an example ofa dilution sub-process; Figure 6 illustrates an example of a fractionator; Figure 7 illustrates an example of fiber widths without process controlchemicals and with eleven different process control chemicals; Figure 8 illustrates an example of sizes of large and small ﬂocs withoutprocess control chemicals and under the effect of eleven different process controlchemicals; Figure 9 illustrates an example of sizes of fines and fillers ﬂocs withoutprocess control chemicals and under the effect of eleven different process controlchemicals; Figure 10 illustrates an example of distributions of solid particle sizesin five fractions without process control chemicals and under the effect of elevendifferent process control chemicals; Figure 11 illustrates an example of a paper machine; and Figure 12 illustrates of an example of a ﬂow chart of a measuring method of suspension.

Description of embodiments The following embodiments are only examples. Although thespecification may refer to "an" embodiment in several locations, this does notnecessarily mean that each such reference is to the same embodiment(s), or thatthe feature only applies to a single embodiment. Single features of differentembodiments may also be combined to provide other embodiments.Furthermore, words "comprising" and "including" should be understood as notlimiting the described embodiments to consist of only those features that havebeen mentioned and such embodiments may contain also features/structuresthat have not been specifically mentioned. lt should be noted that while Figures illustrate various embodiments,they are simplified diagrams that only show some structures and/or functionalentities. The operational connections shown in the Figures may refer to logical orphysical connections. lt is apparent to a person skilled in the art that thedescribed apparatus may also comprise other functions and structures than thosedescribed in Figures and text. lt should be appreciated that details of somefunctions, structures, and the signalling used for measurement and/or controllingare irrelevant to the actual invention. Therefore, they need not be discussed inmore detail here.

Figure 1 illustrates an example of an apparatus for measuringsuspension 102. The suspension 102 has water as medium which has minutesolid particles dispersed within the medium of water. The solid particles areseparate from each other but they may aggregate together. However, theaggregates or ﬂocks may then, in turn, become solid particles and be separateﬂocks. The fact that the solid particles are separate, means that they have aphysical distance therebetween. The solid particles may include at least one of thefollowing: fibers; fines; fillers, minerals; solids of sewage; any combinationthereof or the like. The suspension 102 may be paper stock, sewage water or suspension of a mineral process, for example. The fibers may be natural fibers, such as plant fibers or animal fibers, or synthetic fibers. Additionally, the solid particles may include fines, fillers and/or at least one kind of process controlchemical. The one kind of process control chemical may be an aggregatingadditive or a ﬂocculating agent, for example, which makes the solid particles tocombine in ﬂocks, ﬂocculates, aggregates or clusters.

An image capturing device 100 captures at least one measurementimage 200 (examples of the images are shown in Figure 2A to 3D) of thesuspension 102. An example of the measurement image 200 is shown in Figure 2.The measurement image of Figure 2A shows wood fibers and fines as the solidparticles 202. There may also be fillers. Additionally, the measurement image ofsuspension 102 shown in Figure 2A may also include at least one process controlchemical. One of the wood fibers is a vessel which is much thicker than the otherfibers. The at least one measurement image 200 may refer to one or more stillimage. The at least one image may also refer to video images. The image capturingdevice 100 may comprise one or more cameras (note that Figure 1 shows onlyone camera). The at least one camera may be a high-definition camera. Thecamera may be a charge-couple device (CCD) camera or a complementary metaloxide semiconductor (CMOS) camera, for example. ln an embodiment, the at leastone camera may be a visually visible light camera. ln an embodiment, the at leastone camera may be an infra-red camera. ln an embodiment, the at least onecamera may be an ultraviolet camera. ln an embodiment, the image capturingdevice 100 may include any combination of the visually visible light camera, theinfra-red camera, and the ultraviolet camera. The ratio between the largestresolvable or detectable object in the measurement image and the smallestresolvable object in the measurement image of the image capturing device 100may be 1000000:1 or higher, for example. For determining the ratio, it may beassumed that the largest resolvable or detectable object fills the whole image areaof the image capturing device 100 while the smallest resolvable object has thesize of one pixel. That is, the ratio between the largest resolvable or detectableobject in the measurement image and the smallest resolvable object in themeasurement image is Pmax:1, where Pmax is the maximum number of pixels of the measurement image.

An information processing unit 112 then receives the at least onemeasurement image 200 and determines a state of attachment of the solidparticles 202 of the suspension 102 to each other. The determination of the stateof attachment of the solid particles 202 to each other may be performed using atleast one pattern recognition algorithm applied to the at least one measurementimage 200. The attachment of solid particles 202 to each other may result in aﬂock or a ﬂoccule both of which are loose or dense aggregates of the solidparticles ofthe suspension 102.

The information processing unit 112 may be implemented as aprocessor and software. Likewise, the information processing unit 112 canalternatively be implemented in the form of a hardware configuration by meansof separate logic components or one or more Application-Specific IntegratedCircuits (ASIC). Also a hybrid of these different implementations is possible.

The information processing unit 112 determines, on the basis of thestate of the attachment of the particles 202 of the suspension 102, suspensiondata associated with at least one of the following: at least one process controlchemical, a fiber property, a fines property, a relation between particles ofdifferent sizes, formation, and water content. The suspension data related to theat least one process control chemical may refer to an amount of at least oneprocess control chemical. Here the term content refers to a proportion of thenamed substance in the suspension 102. Additionally, the information processingunit 112 may determine a fiber type content, stock type content, and/or waterremoval potential for example. The information processing unit 112 maycomprise an image processing sub-unit 104, which determines the state ofattachment of the solid particles 202 together on the basis of pattern recognitionapplied to the at least one measurement image 200 (see Figure 2A). Furthermore,the information processing unit 112 may comprise a data processing sub-unit 106which determines the suspension data associated with at least one of thefollowing: at least one process control chemical, fiber content, fines content, stock type content, relation between particles of different sizes, and water content.

The suspension data associated with the amount of at least oneprocess control chemical may refer to an amount of the at least one processcontrol chemical present in the suspension 102 or an amount of the at least oneprocess control chemical to be added in the suspension 102.

The suspension data associated with the fiber property may refer to anamount of the fiber content present in the suspension 102 or an amount of thefibers to be added in the suspension 102.

The suspension data associated with the fiber property may refer to aquality of the fiber present in the suspension 102 or a quality of the fibers to beadded in the suspension 102.

The suspension data associated with the fiber property may refer to atype of the fiber present in the suspension 102 or a type of the fibers to be addedin the suspension 102.

The suspension data associated with the fines property may refer to anamount ofthe fines present in the suspension 102 or an amount ofthe fines to beadded in the suspension 102. The fines property may also be understood as finesand filler property.

The suspension data associated with the fines property may refer to asize or a size distribution of the fines present in the suspension 102 or a size or asize distribution ofthe fines to be added in the suspension 102.

The suspension data associated with the stock type content may referto an amount of the stock type present in the suspension 102 or an amount of thestock type to be added in the suspension 102. The suspension 102 may includeone paper stock type or the suspension 102 may include a plurality of paper stocktypes. A stock type refers to a tree, in general a fiber source or even moregenerally a particle source from which the stock has been made of and/or to themanufacturing method of the stock. ln general, the stock may be manufacturedusing chemical processing or mechanical processing. Additionally or alternatively,a stock may have recycled or non-recycled fibers. The recycled fibers, in turn, vary largely in stock types. A fiber type of a paper stock may determine the stocktype. ln an embodiment, the information processing unit 112 maydetermine, on the basis of the state of the attachment of the particles 202 of thesuspension 102, the suspension data associated with at least one ofthe following:deviation of the amount of at least one process control chemical from a chemicalreference or from a chemical target, deviation of the fiber property from a fiberreference or from a fiber target, deviation of the fines property from a finesreference or from a fines target, deviation of the stock type content from a stocktype reference or from a stock type target, deviation of the relation betweenparticle of different sizes from a particle reference or from a particle target,deviation of ﬂocking from a ﬂocking reference or from ﬂocking target, anddeviation of the water content from a water reference or from a water target.These targets refer to set-point values of the suspension 102. The target maymean a set-point of the process 110 which itself refers to a desired value of acontrolled variable.

Figures 2B to ZE illustrate examples of four reference fractions of thesuspension 102 which have no aggregating additives i.e. process controlchemicals. ln general, the solid particles 202 without process control chemicalsmay represent solid particle references for the measurement. ln Figure 2B thereare the largest solid particles 202 and thus the solid particles 202 of Figure 2Bmay represent a first fiber reference. Figure ZC has the second largest particles202. Also the solid particles 202 in this figure may represent a second fiberreference, for example. Figure 2D has the third largest particles. The solidparticles 202 in this figure may represent a solid particle reference somewherebetween fibers and fines, for example. Figure ZE has the smallest particles whichmay mainly include fines and/or fillers. The solid particles 202 in this figure mayrepresent a fines reference, for example. The fines reference may also beconsidered a fines and fillers reference. ln an embodiment, the deviation of the amount of at least one processcontrol chemical from a chemical reference may be determined by comparing thestate of attachment of the solid particles 202 to each other in a measurement image with a state of attachment of solid particles to each other in a reference image. The reference images, with which the image of the suspension 102 iscompared, may have the same particle content and the same kind of particleswith varying amount of the same process control chemical or chemicals, theamount of the process control chemical or chemicals being known. The referenceimage which has a highest correlation or similarity with the measurement imageof the suspension 102 may be used to determine the amount of the at least oneprocess control chemical present in the solution 102 or the amount ofthe at leastone process control chemical to be added in the solution 102. The correlationC(r), which measures similarity between objects, may mathematically be calculated for variables x(t) and y(t) in the following manner, for example: bC(t) = Ix(z')y(z' + t)dz' , (1where a and b represent the calculation period of the correlation. Digitally,correlation row C may be calculated as a cross product for sequences X and Y in the following manner: NCm) = Zxy. í=l where each C(n) corresponds to an element of correlation row C.

Figures 3A to 3D illustrate examples of four fractions ofthe suspension102 which have at least one process control chemical. The process controlchemical in this case is polymer and silica as a ﬂocking agent. Figures 3A to 3Dmay illustrate examples of measurement images of a suspension 102, the state ofwhich is to be determined. Alternatively, Figures 3A to 3D may be considered toillustrate examples of target images, which have the target or set-point values ofthe solid particles 202. Although Figures 3A to 3D show suspensions includingwood fibers and fines&fillings, suspensions including mineral particles or sewageincluding solid particles from domestic households, agriculture and/or industrymay form aggregates or clusters from the solid particles in the presence of process control chemicals. ln Figure 3A there are the largest solid particles 202 and themeasurement image of Figure 3A may be compared with the fiber referenceFigure 2B. Figure 3B has the second largest particles 202, and the measurementimage of Figure 3B may be compared with the fiber reference image of Figure 2C.Figure 3C has the third largest particles 202, and the measurement image ofFigure 3C may be compared with the solid particle reference image of Figure 2D.Figure 3D has the smallest particles 202, and the measurement image of Figure3D may be compared with the fines reference image of Figure 2E. According tothis kind of comparison the deviation indicates how much effect at least oneaggregate additive has had on the suspension 102. ln an embodiment, the deviation of the fiber property from the fiberreference may refer to a deviation of the fiber type from a fiber type reference. lnan embodiment, the deviation of the fiber property from the fiber target mayrefer to a deviation of the fiber type from a fiber type target. The fiber type maybe based on fiber length, fiber thickness, ratio of fiber length and thickness, fibercurliness, thickness of the wall of a fiber, branching of a fiber, any combinationthereof or the like.

The length of a fiber may be determined on the basis of a length of amidline in the image of the fiber. The curliness C of an object can be defined, for example, by means of the following equation: C = 100-(1 - ö/l), where ö is the shortest distance between the fiber of an object and l is the lengthof the midline of the object. The thickness of a fiber may be determined on thebasis of a length between outer surface ofthe fiber in a perpendicular direction tothe midline in the image of the fiber. The thickness of a fiber wall may bedetermined on the basis of a length from the midline to the outer surface of thefiber in the perpendicular direction to the midline in the image ofthe fiber. Thesemeasurement principles can be applied to any kind, shape or form of solidparticles, not only fibers. An image processing algorithm can perform the required operations and form these values. 11 ln an embodiment, the information processing unit 112 maydetermine data associated with a zeta potential value of the suspension directlyor indirectly on the basis of the suspension data. When a value of the zetapotential is below zero, ﬂocculation may continue and the at least one processcontrol chemical may be input to the suspension in order to have more ﬂocks,make particles thicker, or increase the size of ﬂocks. When a value of the zetapotential is at zero, ﬂocculation comes to an end, and an increase in the at leastone process control chemical will not provide more ﬂocks or increase the size ofﬂocks.

The at least one process control chemical may be input gradually inthe suspension 102, and the state of the attachment of the solid particles 202 toeach other may be determined as a function of the gradual increase of the at leastone process control chemical. The input may be performed in a discrete manneror in a continuous manner. By observing from the at least one image that thelatest addition ofthe at least one process control chemical doesn't cause a changein the state of the attachment of the solid particles 202 to each other, theinformation processing unit 112 may determine that the zeta potential hasreached the value 0. The zeta potential may actually have crossed the zero valuesomewhat, but still a huge overdose may be avoided.

On the other hand, by observing from the at least one image that thelatest addition of the at least one process control chemical causes a change in thestate of the attachment of the solid particles 202 to each other, the informationprocessing unit 112 may determine that the zeta potential has not yet reached thevalue 0. That may be a reason to continue the addition of the at least one processcontrol chemical. By observing a speed at which the state ofthe attachment ofthesolid particles 202 to each other develops with respect to the addition of the atleast one process control chemical, the information processing unit 112 maydetermine a value ofthe zeta potential.

The zeta potential is an electrokinetic potential in the suspension. Thezeta-potential thus refers to ionic concentration and a difference in electric potential as a function of distance from a solid particle 202 in the suspension 102. 12 The zeta-potential is formed because charged solid particles of the same chargegather around a solid particle 202. When the electric repulsion of the chargedsolid particles 202 of the same charge is the same as the attraction towards thesolid particle 202, no more charged solid particles will gather around the solidparticle 202. At this point, the value ofthe zeta potential is zero. The phenomenoncan be seen or detected in the captured images. A fiber attracts a certain numberof smaller solid particles 202 such as fines and/or fillers around it. The fibers orother large solid particles also attract each other which results in ﬂocks. Aﬂocculating agent may increase the number of smaller solid particles 202 aroundthe fiber but inevitably there is a certain limit. The length and thickness of thefiber seems to increase when smaller solid particles 202 are attached to the fiber.A ﬂocculating agent also increases the number of ﬂocks and/or the size of theﬂocks. One ﬂocculating agent may have a different effect on the zeta potentialthan another ﬂocculating agent. A suspension 102 with a high zeta-potential iselectrically less attracting and thus such a suspension has no ﬂocks, few ﬂocks oronly small ﬂocks. A suspension 102 with a low zeta-potential is electrically moreattracting and thus such a suspension has ﬂocks. The lower the zeta potential is,the more ﬂocculates or ﬂocks there are, and vice versa. ln an embodiment, the deviation of the amount of at least one processcontrol chemical from a chemical target may be determined by comparing thestate of attachment of the solid particles 202 to each other in a measurementimage with a state of attachment of the particles 202 to each other in a targetimage. The target image shows a set-point condition for the suspension 102. Thetarget images, which may be similar to those in Figures 3A to 3D and with whichthe measurement image of the suspension 102 is compared, may have the sameparticle content and the same kind of solid particles with varying amount of thesame process control chemical or chemicals, the amount of the process controlchemical or chemicals being known. The deviation in a correlation between themeasurement image of the suspension 102 and the target image may be used todetermine the amount of the at least one process control chemical present in the solution 102 or the amount of the at least one process control chemical to be 13 added in the solution 102. According to this kind of comparison the deviationindicates how much the at least one process control chemical should change thepresent condition of the suspension 102. ln an embodiment, the information processing unit 112 may comprisean artificial neural network which may determine the suspension data on thebasis of supervised or non-supervised pre-training ofthe pattern recognition. ln the supervised classification, the information processing unit 112 ismanually taught to distinguish different solid particles and classify them indifferent classes.

The pattern recognition of the non-supervised neural network mayuse, for instance, a self-organizing map (SOM) of neural computing. ln an embodiment, the information processing unit 112 may classifyand organize automatically and in a unsupervised or supervised manner theimages on the basis of at least one clustering algorithm. The unsupervisedclassification may automatically organize the images on the basis of at least one ofthe following: self-organizing map of neural computing, t-distributed stochasticneighbor embedding, principal component analysis, sammon mapping method,GTM (General Topographic Mapping), LLE (Locally Linear Embedding) mapping,lsomap, agglomerative or hierarchial hierarchal clustering, including single-link-,complete-link-, average-link clustering, clustering error minimization, distanceerror minimization, K-means clustering, K-method, and graph-based methods likesingle-or complete link clustering, density based method, density-based spatialcluster of applications with noise (DBSCAN), AUTOCLASS, SNOB, BIRCH, MCLUST,or model based clustering COBWEB or CLASSIT, simulated annealing forclustering, genetic algorithms, Bayesian method, Kernel method,Multidimensional scaling, principal curve, T-SNE, some of their combination orthe like. ln an embodiment, the processing unit 112 using unsupervisedclassification or supervised classification may optimize the number ofpredetermined features measured from the images. The optimization of the features may be automatized or it may require a user input. 14 ln an embodiment an example of which is illustrated in Figure 4, theinformation processing unit 112 may comprise one or more processors 400 andone or more memories 402. The one or more memories 402 may include acomputer program code. The one or more memories 402 and the computerprogram code may cause, with the one or more processors 400, the apparatus toperform the following steps. Pattern recognition is performed to themeasurement image 200 on the basis of at least one pattern recognitionalgorithm. The state of the attachment of the particles 202 of the suspension 102to each other is determined on the basis ofthe pattern recognition. On the basis ofthe state of the attachment of the particles 202 of the suspension 200, thesuspension data is determined. The comparison between the reference image andthe measurement image or the comparison between the target image and themeasurement image may also be performed with the one or more processors 400,the one or more memories 402 and the computer program code. ln an embodiment, an example of which is illustrated in Figure 5, theapparatus may comprise a dilution sub-process 500. The dilution sub-process500 may take a sample from the process 110, dilute the sample to a desiredconsistency range or to a desired consistency with water, and provide, for theimage capture performed by the image capturing device 100, the diluted sampleofthe suspension 102. The dilution sub-process 500 may comprise a sampler 502which takes a suspension sample from the process 110. The sampler 502 maycomprise a valve the operation of which may be controlled by the informationprocessing unit 112. The dilution sub-process 500 may also comprise ameasurement chamber 504. The sample may ﬂow through the measurementchamber 504 or the measurement chamber 504 may be a closed container whichmay be emptied back to the process 110 or elsewhere. The measurementchamber 504 is transparent to the optical radiation with which the measurementimage is captured with the image capturing device 100. The whole measurementchamber 504 may be transparent for capture of image and for potential illumination from a light source 506. Alternatively, the measurement chamber 504 may be sectionally transparent i.e. the measurement chamber 504 may have a window through which the measurement image is captured and potentiallyilluminated by the light source 506. The reference image and the target imagemay also be captured similarly. ln an embodiment, an example of which is illustrated in Figure 6, thedilution sub-process 500 may comprise a fractionator 600 which may provide atleast one fraction which includes a desired size range of the solid particles 202 ofthe suspension 102 for the image capture by the image capturing device 100. Thefractionator may have a tube for fractionating the solid particles of the suspension102 ﬂowing in the tube. The image capturing device 100 may capture imagesdirectly from the tube which then acts as the measurement chamber. Additionallyor alternatively, different fractions may be separated in different containers 602,604, 606, 608. One or more of the fractions may then be fed from the containers602 to 608 in to the separate measurement chamber 504 and the image capturingdevice 100 may then capture an image of the one or more fractions. ln anembodiment, at least two fractions from the suspension 102 are formed. ln an embodiment, the information processing unit 112 maydetermine, on the basis of the states of the attachment of the particles 202 in aplurality of fractions of the suspension 102, the suspension data. By observingfrom the at least one image that the latest addition of the at least one processcontrol chemical causes a change in the state of the attachment of the solidparticles 202 to each other in one or more fractions, the information processingunit 112 may determine that the zeta potential has not yet reached the value 0.For example, it may be more informative to monitor the state of fines fractionthan a fiber fraction in some cases because the development in the fines fractionmay be faster (there may be more fines particles than fiber particles in a unitvolume). That may be a reason to continue the addition of the at least one processcontrol chemical.

The information processing unit 112 may also control on the basis ofsaid suspension data whether to increase, keep unchanged or change a propertyrelated to one of the following in the process: process control chemical, fibers, fines, stock type, particles of one size with respect to particles of at least one other 16 size, formation, and water. The information processing unit 112 may also controlwhether to increase, keep unchanged, decrease or increase one ofthe following inthe process: the process control chemical, the fibers, the fines, the stock type, theparticles of one size with respect to particles of at least one other size, and water. ln an embodiment, the information processing unit 112 may controlthe input of the at least one process control chemical to the process 110 usingsolid particle actuators 120. Each solid particle actuator SOLID 1 SOLID M ofthe solid particle actuators 120 may feed one kind of solid particles 202 to theprocess 110. The solid particles 202 of one actuator 120 may differ from the solidparticles 202 of at least one other actuator 120. The solid particles may differfrom each other on the basis of length, thickness, wall thickness, a type of stock orthe like. ln an embodiment, the information processing unit 112 may controlthe solid particle actuator SOLID 1 SOLID M which input of at least two types ofstock to the process 110, where M is an integer equal to or larger than one. Thetype of stocks may differ from each other on the basis of recycling, for example.One ofthe types of stocks may be recycled stock and another type of stock may benon-recycled stock, for example. ln an embodiment, the information processing unit 112 may control atleast one chemical actuator 122 which inputs the at least one ﬂocculant foroptimizing ﬂocking of the particles in the process 102. lf there are more than onechemical actuator CHEMICAL 1 CHEMICAL N in use, one of the process controlchemical may differ from at least one other process control chemical, where N isan integer equal to or larger than one,. The process control chemical may refer toa ﬂocculant or a ﬂocculating agent. The purpose of the at least one ﬂocculant asthe process control chemical is to cause the solid particles 202 of the suspension102 to aggregate in ﬂocs. Flocculants may comprise inorganic salts or water-soluble organic polymers. ln an embodiment, the information processing unit 112 may controlthe chemical actuator CHEMICAL 1 CHEMICAL N which input the at least one retention agent. The at least one retention agent may optimize the operational 17 efficiency of the process 102. The at least one retention agent may include acationic or anionic acrylamide copolymer. A retention agent may also be aﬂocculant. ln an embodiment, the information processing unit 112 may controlthe chemical actuator CHEMICAL l CHEMICAL N which input the at least onedeinking agent for optimizing deinking in the process 102. ln an embodiment, the information processing unit ll2 may control atleast one mechanical actuator 124 which inputs operational power formechanical processing of the suspension 102. ln an embodiment, the mechanicalprocessing may be refining. The mechanical actuator may have an electric motorfor which less, equal or more electrical power may be supplied on the basis ofthemanipulated variable from the information processing unit 112, for example. ln an embodiment, the information processing unit ll2 may control atleast one water removal actuator 126 which is associated with removal of waterfrom the process 110. Water may be removed through a wire, by a press or in adrying section (see Figure ll).

Figure 7 illustrates an example of a dependence of fiber widths insuspensions having various process control chemicals Cl to Cll. The widths arein the vertical axis in micrometers, and the reference R and the suspensions withthe process control chemicals Cl to Cll are in the horizontal axis. The suspension202, which is the reference R, has no process control chemical. The processcontrol chemicals Cl to Cll has been dosed the same amount to the same volumeof identical samples of suspension which is similar to the suspension of thereference R. lt can be seen that different process control chemicals Cl to Cllcause different increase in widths of the fibers. The width may change becausesmaller solid particles attach to the fibers. ln general, the width of solid particlesmay change because smaller solid particles attach to larger solid particles becauseof the effect of the process control chemicals Cl to Cll. Thus, to control theprocess ll0, the controller may select a suitable process control chemical Cl toCll on the basis of the state ofthe attachment ofthe solid particles 202. Typically the controller may also have the reference size ofthe solid particles available. The 18 state of the attachment of the solid particles may be measured as the width of thesolid particles 202. Any of the fiber widths caused by various process controlchemicals C1 to C11 may be used as a target or a set-point. Alternatively, any ofthe fiber widths caused by various process control chemicals Cl to C11 may beused as the fiber reference.

Figure 8 illustrates an example of formulation of fiber ﬂocks withrespect to the process control chemicals Cl to C11. The number of fiber ﬂocks isin the vertical axis, and the reference R and the suspensions with the processcontrol chemicals C1 to C11 are in the horizontal axis. The continuous line 800illustrates a size category of large fiber ﬂocks which are larger than 1.3 mm, andthe dashed line 802 refers to a size category of small fiber ﬂocks which aresmaller than 1.3 mm. lt can be seen that different process control chemicals C1 toC11 cause different changes in the fiber ﬂock sizes. lt can also be seen thatdifferent process control chemicals C1 to C11 cause different changes in thedifferent fiber ﬂock size categories. Thus, to control the process 110, thecontroller may select a suitable process control chemical C1 to C11 on the basis ofthe state of the attachment of the solid particles 202. Typically the controller mayalso have the target size of the solid particles which may be the set valueavailable. The state of the attachment of the solid particles may be measuredusing at least one size category of the fiber ﬂocks which are in this embodimentthe solid particles 202. Any of the fiber ﬂock sizes caused by various processcontrol chemicals C1 to C11 may be used as a target or a set-point.

Figure 9 illustrates an example of formulation of fines and filler ﬂockswith respect to the process control chemicals C1 to C11. The number of fines andfiller ﬂocks is in the vertical axis, and the reference R and the suspensions withthe process control chemicals C1 to C11 are in the horizontal axis. lt can be seenthat different process control chemicals C1 to C11 cause different changes in thefines and filler ﬂock sizes. Thus, to control the process, the controller may select asuitable process control chemical C1 to C11 on the basis of the state of theattachment of the solid particles 202 and the target size of the solid particles which may be the set value. The state of the attachment ofthe solid particles may 19 be measured using at least one size category of the fines and filler ﬂocks whichare in this embodiment the solid particles 202. Any of the fines and filler ﬂocks'sizes caused by various process control chemicals C1 to C11 may be used as atarget or a set-point.

Figure 10 illustrates an example of distribution of different sized solidparticles in five fractions with respect to the process control chemicals Cl to C11.The vertical axis denotes a percentage (%) of particles in each fraction, and thereference R and the suspensions with the process control chemicals Cl to C11 arein the horizontal axis. The fractions at each process control chemical C1 to C11are from the left to right: fraction 1, fraction 2, fraction 3, fraction 4 and fraction 5.The fraction 1 includes ﬂocks and long fibers. The fraction 2 includes long fibers.The fraction 3 includes fibers. The fraction 4 includes short fibers and fines. Thefraction 5 includes fines and fillers. lt can be seen that different process controlchemicals C1 to C11 cause different changes in different fractions. Any of thedistributions of different sized solid particles in the fractions caused by variousprocess control chemicals C1 to C11 may be used as a target or a set-point. ln an embodiment, the controller may control the deviation of therelation between percentages of the particles of the different sizes from theparticle ratio target by selecting at least one suitable process control chemical tomodify the distribution of at least one fraction in the suspension 102. Here thedifferent sizes refer to different fractions, for example.

Figure 11 shows an example of a structure ofa paper machine. One ormore stocks are fed onto a paper machine through a wire pit silo 1106, which isusually preceded by a blending chest 1102 for partial stocks and a machine chest1104. The machine stock is dispensed for a short circulation, for instance,controlled by a basis weight control or a grade change program. The blendingchest 1102 and the machine chest 1104 may also be replaced by a separatemixing reactor (not shown in Figure 11), and the dispensing ofthe machine stockis controlled by feeding each partial stock separately by means of valves oranother ﬂow control means 1100. Different stocks may be monitored with the image capturing device 100 and the state of each of the stock suspension may be measured with the information processing unit 112. ln the wire pit silo 1106,water is mixed into the machine stock to obtain a desired consistency for theshort circulation (dashed line from a former 1120 to the wire pit silo 1106). Fromthe obtained stock it is possible to remove sand (centrifugal cleaners), air(deculator) and other coarse material (pressure filter) using cleaning devices1108, and the stock is pumped with a pump 1110 to a headbox 1116. Prior to theheadbox 1116, for improving the quality of the end product, it is possible to addto the stock, through valves 1112, 514, a filling agent TA and/or a retention agentRA, which are process control chemicals and affect the ﬂocking.

From the headbox 1116 the suspension is fed via a slice opening 1118to a former 1120. ln the former 1120, water drains out of the web 10 andadditionally solids, such as ash, fines and fibres, are led to the short circulation. lnthe former 1120, the stock is fed as a web 10 onto a wire, and the web 10 ispreliminarily dried and pressed in a press 1122. Formation refers to non-uniformdistribution of the solid particles when the stock is fed on the wire. Formationmay also be defined as variation in the basis weight of the end product which, inturn, is based on the variation of solid material per area unit (i.e. “basis weight")in the web 10. Formation depends on ﬂocculation. Formation may be adjusted, inaddition to or alternatively from a direct ﬂocculation regulation with the at leastone process control chemical, by the former 1120 which may be controlled by thecontroller 1124. The amount of water of the web 10 on the wire may be adjustedwith a slice opening 1118 of the headbox 1116 which may be controlled by thecontroller 1124. That is, water may be removed in advance from the web 10 withthe slice opening 1118 ofthe headbox 1116.

The amount of solid and the moisture content are directlyinterdependent variables. lf the moisture content is 45%, the amount of solid is100% - 45% = 65%, for example. ln this application, the web 10 is considered a suspension until thewater content in the web 10 has decreased excessively. Water may be removedfrom the web 10 using the press 1122 which may be controlled by the controller 1124. Generally, the web 10 is not actually suspension after the press 1122, and 21 consequently the measurement method presented in this application may nolonger be applicable after the press 1122. However, the control of the end productmay be performed also after the press 1122. For example, water may be removedfrom the web 10 at a drying section (not shown in Figures) which may becontrolled by the controller 1124. The drying section may be after the press1122.The paper machine may comprise at least one measuring part 1134 which,in turn, may comprise the image capturing device 100. The measuring part 1134may also comprise the dilution sub-process 500.

Figure 11 also shows a control arrangement of a paper machine.Factors affecting the quality and grade change include, inter alia, the amount andmutual proportion of partial stocks, the amount of filler, the amount of retentionagent, machine speed, the amount of white water and drying capacity. Thecontroller 1124, which may include or be operatively coupled with theinformation processing unit 112, may control the dispensing of partial stocks bymeans ofvalves 1100, the dispensing of each filler TA by means ofthe valve 1112,the dispensing of the retention agent RA by means of the valve 1114, adjust thesize of the slice opening 1118, control the machine speed, control the amount ofwhite water and the drying process. The controller 1124 may utilize the at leastone measuring part 1134 so as to measure the suspension 102 for making theweb 10 on the wire. The controller 1124 may receive data on the stock, processcontrol chemicals and/or the web also from elsewhere.

The process controller 1124 may comprise, for instance, a PID(Proportional-lntegral-Derivative), a fuzzy logic controller, an MPC (ModelPredictive Control) or a GPC (General Predictive Control) controller.

The advanced process controller 1124 may form sets of controlactions for a plurality of actuators including the solid particle actuators 120,chemical actuators 122, mechanical actuators 124 and water removal actuators126, 1120, 1122 in order to regulate various properties of the process 110 and tohave the end product with desired quality. The advanced process controller 1124may form the control actions repeatedly in an iterative manner. The control actions are meant to give new operating settings to the plurality of actuators. The 22 new operating settings may be the same as the previous ones or the newoperating settings may be different from the previous ones. New control actionsmay carry information about a deviation with respect the present settings. ln addition to this, it is clear that the operation of a paper machine isknown per se to a person skilled in the art, and therefore, it need not be presentedin greater detail in this context.

The apparatus may help maintain paper quality, allow faster gradechanges and result in optimization of drainage and retention in the papermanufacturing process. ln general, the apparatus may increase production in theprocess 110.

Figure 12 is a flow chart of the measurement method. ln step 1200, atleast one measurement image 200 of suspension 102 is captured by an imagecapturing device 100. ln step 1202, the at least one measurement image 200 isreceived 1202, and a state of attachment of the solid particles 202 of thesuspension 102 together is determined on the basis of pattern recognitionapplied to the at least one measurement image 200 by an image processing sub-unit 104. ln step 1204, suspension data associated with at least one of thefollowing: at least one process control chemical, fiber content, fines content, stocktype content, relation between particles of different sizes, and water content, isdetermined by a data processing sub-unit 106 on the basis of the state of theattachment ofthe particles 202 ofthe suspension 102.

The method shown in Figure 12 may be implemented as a logic circuitsolution or computer program. The computer program may be placed on acomputer program distribution means for the distribution thereof. The computerprogram distribution means is readable by a data processing device, and itencodes the computer program commands, carries out the measurements andoptionally controls the processes on the basis ofthe measurements.

The computer program may be distributed using a distributionmedium which may be any medium readable by the controller. The medium maybe a program storage medium, a memory, a software distribution package, or a compressed software package. ln some cases, the distribution may be performed 23 using at least one of the following: a near field communication signal, a shortdistance signal, and a telecommunications signal. lt will be obvious to a person skilled in the art that, as technologyadvances, the inventive concept can be implemented in various ways. Theinvention and its embodiments are not limited to the example embodiments described above but may vary within the scope of the claims.

Claims

23 Claims

1. An apparatus for measuring suspension, wherein the apparatuscomprises an image capturing device (100) configured to capture at least onemeasurement image (200) ofthe suspension (102), the at least one measurementimage presenting at least one solid particle (202), c h a r a c t e r i z e d in that theapparatus further comprises a dilution sub-process (500) which comprises a fractionator (600)configured to provide at least one fraction which includes a desired size range ofthe particles ofthe suspension (102) for the image capture by the image capturingdevice (100); an information processing unit (112) configured to receive the at leastone measurement image (200) and determine a state of attachment of the solidparticles (202) of the suspension (102) to each other on the basis of patternrecognition applied to the at least one measurement image (200); and the information processing unit (1 12) is configured to determine, on thebasis of the state of the attachment of the solid particles (202) of the suspension(102), suspension data associated with at least one of the following: at least oneprocess control chemical, at least one fiber property, at least one fines property, a relation between solid particles of different sizes, formation, and water content.

2. The apparatus of claim 1, c h a r a c t e r i z e d in that theinformation processing unit (112) is configured to determine, on the basis of thestate of the attachment of the solid particles (202) of the suspension (102), thedata associated with at least one of the following: deviation of an amount of at leastone process control chemical from a chemical reference or from a chemical target,deviation of the fiber property from a fiber reference or from a fiber target,deviation of the fines property from a fines reference or from a fines target,deviation of the relation between particles of different sizes from a particle reference or from a particle target, deviation of ﬂocking from a ﬂocking reference 24 or from a ﬂocking target, and deviation of the water content from a water reference OI' fFOITI a Watel' tafget.

3. The apparatus of claim 1 or 2, ch a ra cte riz e d in that theinformation processing unit (112) is configured to determine data associated witha zeta potential value of the suspension (102) directly or indirectly on the basis of the suspension data.

4. The apparatus of any preceding claim, c h a r a c t e r i z e d in thatthe information processing unit (112) comprises one or more processors (300); one or more memories (302) including computer program code; and the one or more memories (302) and the computer program codeconfigured to, with the one or more processors (300), cause apparatus at least to: perform the pattern recognition to the measurement image (200) onthe basis of at least one pattern recognition algorithm; determine the state of the attachment ofthe solid particles (202) ofthesuspension (102) to each other on the basis ofthe pattern recognition; and determine the suspension data.

5. The apparatus of claim 1, c h a r a c t e r i z e d in that the dilutionsub-process (500) is configured to take a sample from the process (110), dilute thesample to a desired consistency, and provide, for the image capture by the image capturing device (100), the diluted sample.

6. The apparatus of claim 1, c h a r a c t e r i z e d in that theinformation processing unit (112) is configured to determine, on the basis of thestates of the attachment of the particles (202) in a plurality of fractions of the suspension (102), the suspension data.

7. An apparatus for controlling a process of suspension, c h a r a c t e r i z e d in that the apparatus comprises the apparatus of claim 1 for measuring a process associated with water suspension including the solid particles(202) ; and the information processing unit (112) is configured to control, on thebasis of said suspension data, whether to keep unchanged or change propertyrelated to at least one of the following in the process: at least one process controlchemical, fibers, fines, stock type, solid particles of one size with respect to solid particles of at least one other size, formation, and water.

8. The apparatus of claim 7, c h a r a c t e r i z e d in that theinformation processing unit (112) is configured to control the input ofthe at least one process control chemical to the process (110).

9. The apparatus of claim 8, c h a r a c t e r i z e d in that theinformation processing unit (112) is configured to control the input ofthe at least one ﬂocculant for optimizing ﬂocking ofthe solid particles in the process (110).

10. The apparatus of claim 8, c h a r a c t e r i z e d in that theinformation processing unit (112) is configured to control the input of the at least one retention agent for optimizing the operational efficiency ofthe process (110).

11. The apparatus of claim 7, c h a r a c t e r i z e d in that theinformation processing unit (112) is configured to control the input of at least two types of stock to the process (110).

12. The apparatus of claim 7, c h a r a c t e r i z e d in that theinformation processing unit (112) is configured to control the input of operational power for mechanical processing of the suspension.

13. The apparatus of claim 7, c h a r a c t e r i z e d in that theinformation processing unit (112) is configured to control removal of water from the process (110).

14. The apparatus of claim 7, c h a r a c t e r i z e d in that the information processing unit (112) comprises 26 one or more processors (300): one or more memories (302) including computer program code; and the one or more memories (302) and the computer program codeconfigured to, with the one or more processors (300), cause the informationprocessing unit (112) at least to: perform the pattern recognition to the image (200); determine the state of the attachment of the particles (202) of thesuspension (102) together on the basis of at least one algorithm of the patternrecognition, and control the input to and/or the output from the process (110) on the basis of said suspension data.

15. A method for a process associated with suspension including solidparticles, the method comprising capturing (1200) at least one measurement image (200) of suspension(102) by an image capturing device (100), c h a r a c t e r i z e d by providing, by a fractionator (600), at least one diluted fraction whichincludes a desired size range of the particles ofthe suspension (102) for the imagecapture by the image capturing device (100) ; receiving (1202) the at least one measurement image (200) anddetermining, by an image processing sub-unit (104), a state of attachment of thesolid particles (202) of the suspension (102) together on the basis of patternrecognition applied to the at least one measurement image (200); and determining (1204), by a data processing sub-unit (106) on the basis ofthe state of the attachment of the particles (202) of the suspension (102),suspension data associated with at least one ofthe following: at least one processcontrol chemical, fiber content, fines content, stock type content, relation between particles of different sizes, formation , and water content.

16. The method of claim 15, c h a r a c t e r i z e d by determining, onthe basis of the state of the attachment of the particles (202) of the suspension (102), the suspension data associated with at least one ofthe following: deviation 27 of the amount of at least one process control chemical from a chemical referenceor from a chemical target, deviation ofthe fiber property from a fiber reference orfrom a fiber target, deviation of the fines property from a fines reference or from afines target, deviation of the relation between particles of different sizes from aparticle reference or from a solid particle target, and deviation of the water content from a water reference or from a water target.

17. The method ofclaim 15, c h a r a c t e r i z e d by determining a zeta potential value ofthe suspension (102) on the basis ofthe suspension data.

18. The method of claim 15, c h a r a c t e r i z e d by controlling, by acontrolling unit (108), an input to and/or an output from the process (110) on the basis of said suspension data.

19. The method of claim 15, c h a r a c t e r i z e d by taking a samplefrom the process (110), diluting the sample and providing the diluted sample for the image capture.

20. The method of claim 19, c h a r a c t e r i z e d by forming at leasttwo fractions from the suspension (102), and determining, on the basis ofthe statesof the attachment of the particles (202) in a plurality of different fractions of the suspension (102), the suspension data.

21. The method ofclaim 15, c h a r a c t e r i z e d by controlling, by theinformation processing unit (112), on the basis of said suspension data, whether tokeep unchanged, or change property related to at least one of the following in theprocess: at least one process control chemical, fibers, fines, stock type, solidparticles of one size with respect to solid particles of at least one other size, formation, and water.