Defects and extractive amount in pulp

Abstract

A method and apparatus (100) capable of predicting an amount of defects in final pulp (58) or extractive amount in final pulp (58) of a pulp production process based on measured hydrophobicity of a filtrate at a brown stock washing stage (21) and / or a filtrate upstream of a bleaching stage (31-33), and capable of recommending an action to be taken to alter the amount of defects or extractive amount in final pulp (58) based on said predicting.

Description

[0001] DEFECTS AND EXTRACTIVE AMOUNT IN PULP

[0002] TECHNICAL FIELD

[0003] The present disclosure generally relates to pulp mills. The disclosure relates particularly, though not exclusively, to a method and apparatus which enable monitoring and controlling an amount of defects or extractive amount in pulp.

[0004] BACKGROUND

[0005] This section illustrates useful background information without admission of any technique described herein representative of the state of the art.

[0006] Pulp is typically used as the main ingredient in paper and board making processes. The quality of pulp used in paper or board mills has a major impact on the paper or board quality. It is therefore desirable to provide methods enabling monitoring and control of pulp quality.

[0007] SUMMARY

[0008] The appended claims define the scope of protection. Any examples and technical descriptions of apparatuses, products and / or methods in the description and / or drawings not covered by the claims are presented not as embodiments of the invention but as background art or examples useful for understanding the invention.

[0009] It is an object of certain embodiments of the invention to improve methods that enable controlling an amount of defects or extractive amount in pulp or at least to provide an alternative solution to existing technology.

[0010] According to a first example aspect of the invention there is provided a method, comprising: predicting an amount of defects in final pulp or extractive amount in final pulp of a pulp production process based on measured or monitored hydrophobicity of a filtrate at a brown stock washing stage and / or a filtrate upstream of a bleaching stage; and recommending an action to be taken to alter the amount of defects or extractive amount in final pulp based on said predicting.

[0011] Accordingly, in certain embodiments, the prediction is obtained based on measurement(s) at a brown stock washing stage. Depending on the implementation, a pulp mill comprises a plurality of brown stock washing stages. The said measurement(s) is / are then performed, at least, at one of the brown stock washing stages. It has been observed that mere measurement of hydrophobicity at the brown stock washing section correlates with the amount of defects and extractive amount of final pulp. Further, it has been observed that the amount of defects and extractive amount of final pulp can be most influenced if the predicting is performed on the basis of early measurements, preferably from the brown stock washing section. In further embodiments, it has been observed that the amount of defects and extractive amount of final pulp can still be greatly influenced if the predicting is performed on the basis of early measurements during bleaching, most preferably from a filtrate of a bleaching stage upstream of at least one further bleaching stage.

[0012] The final pulp herein refers for example to the final pulp product that the pulp mill produces, such as dried pulp obtained from a drying machine section in certain embodiments.

[0013] In certain embodiments, the method comprises: using historical data of the pulp production process (in question) in the predicting of an amount of defects in final pulp or extractive amount in final pulp.

[0014] The historical data in these embodiments, comprises e.g. a previously observed (stored) correlation between measured hydrophobicity at the point of interest (for example, at the brown stock washing stage) and respective observed amount of defects in final pulp or between measured hydrophobicity at the point of interest and respective observed extractive amount in final pulp.

[0015] In certain embodiments, the method comprises: measuring hydrophobicity from a sample of the filtrate or side stream originating from the filtrate (in question) in an online analysis apparatus.

[0016] Accordingly, the actual measurement is performed by the online analysis apparatus in certain embodiments. In certain embodiments, the method comprises: predicting an amount of defects in final pulp based together on hydrophobicity and particle count(s).

[0017] In certain embodiments, a total particle count of a sample is applied. In other embodiments, a particle count of particles of a predetermined size (such as agglomerates) is applied. In certain embodiments, the method comprises fractioning a sample (of the filtrate in question) to obtain particle fractions of different size. In certain embodiments, a particle count of particles of a predetermined mass is applied. In certain such embodiments, instead of particle size, the mass of the particles is used as the basis for fractionating.

[0018] In certain embodiments, the method comprises: predicting an amount of defects in final pulp or extractive amount in final pulp of a pulp production process based on measured hydrophobicity of a filtrate at a brown stock washing stage; and recommending the action to be taken at the brown stock washing stage or at a bleaching stage.

[0019] In certain embodiments, the recommended action is subject to the prediction exceeding or falling below a threshold limit.

[0020] In certain embodiments, the method comprises: timing the recommended action to focus on the exact pulp whose filtrate was used as a basis for the predicting. It is understood that the pulp in the pulp production process has a defined or determinable lead time. By taking this into account, it can be confirmed that the recommended action will focus on the pulp at an implementation point at a correct time (thus taking into account a delay between a point of measurement and a point at which the recommended action is implemented).

[0021] In certain embodiments, the method comprises: further predicting the amount of defects in the final pulp or extractive amount in the final pulp based on measured hydrophobicity of a filtrate at a (further) point of the pulp production process where the pulp has already undergone the recommended action; and indicating whether a further action needs to be taken to alter the amount of defects or extractive amount in final pulp based on said further predicting.

[0022] In this way a two-phase (converging) prediction is implemented. A rough adjustment may be implemented based on a “first prediction”, and fine-tuning based on the further prediction.

[0023] In certain embodiments, if a certain predetermined condition is fulfilled, it is indicated that a further action needs to be taken (and preferably, the particular action is specified). In certain embodiments, if a certain predetermined condition is not fulfilled, it is indicated that no further action needs to be taken.

[0024] As an example, when the predicted extractive amount (or, similarly, the predicted amount of defects) exceeds a desired value, a further action needs to be taken (e.g., chemical addition increased). When the predicted extractive amount (the predicted amount of defects) is at the desired value or slightly below (within a predetermined range), no further action is needed. In certain embodiments, when the predicted extractive amount (the predicted amount of defects) falls further below the desired value, an opposite action is recommended (e.g., chemical addition reduced). Similar conditions and actions may be applied when actions are recommended based on the “first prediction”.

[0025] In certain embodiments, the further prediction at the further point in the pulp production process is conducted by measuring hydrophobicity from a filtrate of the corresponding (“same”) pulp whose filtrate was used as a basis for the preceding (“original”) prediction (taking a process delay between measurement points into account).

[0026] In certain embodiments, the further predicting is performed based on measured hydrophobicity of a filtrate from a drying machine section of the pulp production process (the further point is at a drying machine section of the pulp production process).

[0027] In this way, hydrophobicity of a filtrate at a brown stock washing stage and / or a filtrate upstream of a bleaching stage is measured (monitored) concerning (or at) a first point in the pulp production process, and the method further comprises: additionally measuring (monitoring) hydrophobicity in the pulp production process concerning (or at) another point (preferably at a drying machine section) downstream of said first point (and predicting concerning (or at) both points). Herein downstream means process-wise downstream (wherein “process” means the pulp production process).

[0028] In certain embodiments, a first prediction is performed based on measurement(s) at the brown stock washing section, and a further prediction based on measurement(s) at the bleaching section. In certain embodiments, a first prediction is performed based on measurement(s) at the brown stock washing section, and a further prediction based on measurement(s) at the drying machine section. In certain embodiments, a first prediction is performed based on measurement(s) at a bleaching stage, and a further prediction based on measurement(s) at a further (process-wise later) bleaching stage. In certain embodiments, a first prediction is performed based on measurement(s) at a bleaching stage, and a further prediction based on measurement(s) at the drying machine section.

[0029] In certain embodiments, the recommended or further action comprises:

[0030] - controlling the addition of a chemical into a phase of the pulp production process (said phase may be upstream or downstream from the process phase or stage whose filtrate is used as a basis for the prediction) or adjusting said controlling; or

[0031] - changing a process parameter or process conditions of the pulp production process.

[0032] In certain embodiments, the recommended or further actions may be corrective or opposite actions.

[0033] Certain particular examples of recommended or further actions to be taken are:

[0034] - adding dispersing agent to a washer (brown stock washer or washer at a bleaching stage);

[0035] - adding more dilution water to a washer (brown stock washer or washer at a bleaching stage).

[0036] In certain embodiments, predicting an amount of defects in final pulp or extractive amount in final pulp comprises predicting an amount of defects in dried pulp or extractive amount in dried pulp (final pulp product). According to a second example aspect of the invention there is provided a method, comprising: monitoring hydrophobicity at two points of a pulp production process and predicting an amount of defects in final pulp or extractive amount in final pulp based on said monitoring.

[0037] In certain embodiments, the method comprises: recommending an action to be taken to alter the amount of defects or extractive amount in final pulp based on predicting on the basis of monitoring hydrophobicity at a first (earlier) point of the two points of the pulp production process.

[0038] In certain embodiments, the method comprises: verifying the effect of the recommended action based on predicting on the basis of monitoring hydrophobicity at a second (later) point of the two points of the pulp production process.

[0039] In certain embodiments, the method comprises: indicating whether there is a need for a further action to be taken to alter the amount of defects or extractive amount in final pulp based on the verifying.

[0040] According to a third example aspect of the invention there is provided an apparatus, comprising: at least one processor; and at least one memory including computer program code, the at least one memory and the computer program code being configured, with the at least one processor, to cause the apparatus to perform the method of the first or second aspect or any of their embodiments.

[0041] According to a fourth example aspect of the invention there is provided a computer program comprising computer executable program code which when executed by a processor causes an apparatus to perform the method of the first or second aspect or any of their embodiments.

[0042] According to a fifth example aspect there is provided a computer program product comprising a non-transitory computer readable medium having the computer program of the third example aspect stored thereon. According to a sixth example aspect there is provided an apparatus comprising means for performing the method of the first aspect or any related embodiment.

[0043] Any foregoing memory medium may comprise a digital data storage such as a data disc or diskette, optical storage, magnetic storage, holographic storage, opto- magnetic storage, phase-change memory, resistive random-access memory, magnetic random access memory, solid-electrolyte memory, ferroelectric random access memory, organic memory or polymer memory. The memory medium may be formed into a device without other substantial functions than storing memory or it may be formed as part of a device with other functions, including but not limited to a memory of a computer, a chip set, and a sub assembly of an electronic device.

[0044] Different non-binding example aspects and embodiments have been illustrated in the foregoing. The embodiments in the foregoing are used merely to explain selected aspects or steps that may be utilized in different implementations. Some embodiments may be presented only with reference to certain example aspects. It should be appreciated that corresponding embodiments apply to other example aspects as well.

[0045] BRIEF DESCRIPTION OF THE FIGURES

[0046] Some example embodiments will be described with reference to the accompanying figures, in which:

[0047] Fig. 1 shows certain sections of a pulp production process;

[0048] Fig. 2 shows a measurement point in accordance with certain example embodiments;

[0049] Fig. 3 shows a block diagram of a control apparatus in accordance with certain embodiments;

[0050] Fig. 4 shows a two-phase prediction in accordance with certain embodiments;

[0051] Fig. 5 shows measurement points in accordance with certain embodiments;

[0052] Fig. 6 shows measurement points in accordance with certain further embodiments;

[0053] Figs. 7-9 show certain observed correlations between hydrophobicity measurements and extractive amounts; Figs. 10-11 show certain observed correlations between hydrophobicity measurements and amount of defects over time;

[0054] Fig. 12 shows an observed correlation between the amount of defects, hydrophobicity and particle count over time; and

[0055] Fig. 13 shows another block diagram of a control apparatus in accordance with certain embodiments.

[0056] DETAILED DESCRIPTION

[0057] In the following description, like reference signs denote like elements or steps.

[0058] Fig. 1 shows certain sections of a pulp production process. A brown stock washing section 20 comprises one or more brown stock washing stages 21 . Pulp washed at the brown stock washing section 20 then enters a bleaching section 30 typically comprising a plurality of subsequent bleaching stages 31 -33. Fig. 1 shows in machine direction a first bleaching stage 31 , a second bleaching stage 32 and a final bleaching stage 33. Accordingly, in machine direction, the second bleaching stage 32 follows the first bleaching stage 31 , and the final bleaching stage 33 follows the second bleaching stage 32. It should be noted, however, that the number of bleaching stages depends on the implementation, and therefore there may be more than three or less than three bleaching stages.

[0059] The cleanliness of pulp improves in machine direction. The bleaching section 30 is followed by a drying machine section 40 wherein the pulp undergoes a dewatering process to produce dried pulp, which is herein considered as the final product of the pulp mill, i.e., final pulp. Certain features of the drying machine section 40 relating to water circulation(s) at the drying machine section 40 are denoted as numerals 41 , 42 and 43. The reference numeral 41 denotes a circulation water tank, the reference numeral 42 a circulation water tower, and the reference numeral 43 denotes felt water.

[0060] In certain embodiments, measured hydrophobicity of a filtrate at a brown stock washing stage 21 is used to predict an amount of defects in final pulp or extractive amount in final pulp. For this purpose, a sample of filtrate from a brown stock washing stage 21 is obtained (e.g. pumped) into an online analysis apparatus (herein denotes as a control apparatus) 100 as shown in Fig. 2. Fig. 3 shows a block diagram of a control apparatus in accordance with certain embodiments. Hydrophobicity of a received sample is measured by an optical measurement device 103 (e.g. by a fluorescence measurement). A hydrophobic dye may have been applied to the sample in a preceding phase 101 if the apparatus 100 comprises a dye adding section 101. Optionally, the sample is fractioned into fraction(s) based on particle size in an optional fractionator 102 prior to the hydrophobicity measurement. In this way, particle counts of different fractions can be determined. In certain embodiments, the control apparatus 100 further comprises an analyzer 104 for analyzing the hydrophobic measurement(s).

[0061] The analyzer 104 (or a separate analyzer depending on the implementation) knows a correlation between hydrophobicity measurements and defects or extractive amount (amount of extractives) in final pulp. The correlation may be based on historical data of the pulp production process in question.

[0062] The analyzer 104 then uses the hydrophobicity measurements in predicting defects or extractive amount in final pulp. In the event the prediction fulfills a predetermined condition, an action to be taken to alter the amount of defects or extractive amount in final pulp is recommended. The predetermined condition in certain embodiments is selected from a group comprising: exceeding a limit, falling below a limit, and falling out of range.

[0063] In certain embodiments, the recommendation is in the form of indicating a value, indicating an action (e.g., a corrective or an opposite action), or providing a control signal. In certain embodiments, the indication(s) or the control signal is provided to a responsible automation system of the pulp mill or to an operator for manual or automatic operation.

[0064] It has been observed that major corrective actions are enabled when predicting is performed based on measurements from the brown stock washing section 20 from which it will take about 6 to 20 hours for the pulp to advance to final pulp. Yet, is has been observed that accurate actions can be performed based on measurements at such an early stage, and that hydrophobicity measurements correlate to the amount of defects and extractive amount already at that stage.

[0065] In further embodiments, instead of predicting based on measurements at the brown stock washing stage 21 , predicting is performed based on later measurement(s). This will still enable predicting the amount of defects or extractive amount several hours in advance. In these embodiments, it has been observed that the amount of defects and extractive amount of final pulp can still be greatly influenced if the predicting is performed on the basis of early measurements during bleaching, most preferably from a filtrate of a bleaching stage upstream of at least one further bleaching stage (here: from a filtrate at a first or second bleaching stage 31 or 32).

[0066] In further embodiments, as shown in Fig. 4, a two-phase prediction is performed. In these embodiments, hydrophobicity is monitored (or measured) at two points of a pulp production process, and an amount of defects or extractive amount in final pulp 58 is predicted based on said monitoring. Hydrophobicity is measured from a filtrate at a first monitoring point in step 51 . The first monitoring point may be at the brown stock washing section 20 (at a brown stock washing stage 21 ) or at one of the bleaching stages 31 -33. A first prediction 52 of an amount of defects or extractive amount in final pulp 58 is made based on measured hydrophobicity at the first monitoring point. If required, a first action 53 to be taken to alter the amount of defects or extractive amount in final pulp 58 is recommended based on said first prediction (if a predetermined condition is fulfilled). To verify the effect of the first action, hydrophobicity is further measured from a filtrate at a second monitoring point in step 54 (wherein the second monitoring point is downstream of the first monitoring point, at the bleaching section 30 or at the drying machine section 40). At this point the pulp has already undergone the first action 53. A second prediction 55 of an amount of defects or extractive amount in final pulp 58 is made based on measured hydrophobicity at the second monitoring point. If required, a second action 56 to be taken to alter the amount of defects or extractive amount in final pulp 58 is recommended based on said second prediction (if a predetermined condition is fulfilled). In this way, a rough adjustment to alter the quality of final pulp 58 may be implemented based on the first prediction 52, and fine-tuning may be performed based on the second prediction 55.

[0067] Fig. 5 shows measurement points in accordance with certain embodiments. A first measurement point is at the brown stock washing stage 21 and a further measurement point can be at any or all of the bleaching stages 31 -33 or at the drying machine section 40.

[0068] Fig. 6 shows measurement points in accordance with certain further embodiments. In these embodiments, a first measurement point is at one bleaching stage 31 -33 and a further measurement point can be at a remaining (later) bleaching stage or at the drying machine section 40.

[0069] Figs. 7-9 show observed correlations between hydrophobicity measurements and extractive amounts. Fig. 7 shows the extractive amount in final pulp (in scaled values) as a function of hydrophobicity measured from a filtrate at the brown stock washing section. Fig. 8 shows the extractive amount in final pulp (in scaled values) as a function of hydrophobicity measured from a filtrate at a first bleaching stage. Fig. 9 shows the extractive amount in final pulp (in scaled values) as a function of hydrophobicity measured from felt water at the drying machine section. It can be concluded that there is a correlation between hydrophobicity measured at the drying machine section and extractive amounts in final pulp. It can be further concluded that there is a correlation between hydrophobicity measured at the bleaching section and extractive amounts in final pulp. The correlation between hydrophobicity measured at the brown stock washing section and extractive amount in final pulp is weaker but still usable. The correlation(s) can be used in predicting the extractive amount in final pulp, and corrective actions recommended or performed based on the prediction (e.g., open circulation, increase chemical dosing). The recommended action need not be corrective actions in all instances. For example, if the pulp production process produces pulp of excessively good quality, opposite actions may be recommended or performed (e.g., close circulation, reduce chemical dosing) for environmental reasons or for saving resources.

[0070] Figs. 10 and 11 show observed correlations between hydrophobicity measurements and defects. Fig. 10 shows the correlation between hydrophobicity measured at the first bleaching stage and the amount of defects (scale value) in final pulp. Fig. 11 shows the correlation between hydrophobicity measured at the drying machine section and the amount of defects (scaled value) in final pulp. There is a clear correlation in both cases. When the hydrophobicity increases, the amount of defects increases. The correlation(s) can be used in predicting the defects in final pulp, and corrective (or opposite) actions recommended or performed based on the prediction. Fig. 12 shows an observed correlation between the amount of defects in final pulp, and hydrophobicity and particle count (of agglomerates) at the drying machine section. In more detail, the correlation is between the amount of defects and an index that is obtained by taking into account the measured hydrophobicity and the particle count (the index is presented as a scaled value). There is a strong correlation between the amount of defects in final pulp and said index at the drying machine section. By using the particle count in addition to the measured hydrophobicity, the prediction can therefore be made more accurate in certain embodiments.

[0071] Fig. 13 schematically shows a block diagram of an apparatus according to certain example embodiments. In particular, Fig. 13 shows another presentation of blocks of an apparatus such as a control apparatus (or online analysis apparatus) 100 capable of performing the aspects and various embodiments of the present disclosure. The apparatus 100 comprises for example a general-purpose computer or server or some other electronic data processing apparatus. In certain embodiments, the apparatus 100 comprises a sample processing unit 150, although in other embodiments, a sample processing unit 150 is implemented as a separate element. In certain embodiments, the sample processing unit 150 comprises the optical measurement device 103. In certain embodiments, the sample processing unit 150 comprises the dye adding section 101 depending on the implementation, the optional fractionator 102, and the analyzer 104. In other embodiments, the analyzer 104 is implemented at least partly by other blocks of the apparatus 100. In certain embodiments, the apparatus 100 is integrated with an automation system of the pulp mill.

[0072] The apparatus 100 comprises a communication interface 155, a processor 151 , a user interface 154, and a memory 152.

[0073] The communication interface 155 comprises in an embodiment a wired and / or wireless communication circuitry, such as Ethernet, Wireless LAN, Bluetooth, GSM, CDMA, WCDMA, LTE, and / or 5G circuitry. The communication interface can be integrated in the apparatus 100 or provided as a part of an adapter, card or the like, that is attachable to the apparatus 100. The communication interface 155 may support one or more different communication technologies. The apparatus 100 may also or alternatively comprise more than one communication interface 155.

[0074] The processor 151 may be a central processing unit (CPU), a microprocessor, a digital signal processor (DSP), a graphics processing unit, an application specific integrated circuit (ASIC), a field programmable gate array, a microcontroller or a combination of such elements.

[0075] The user interface 154 may comprise a circuitry for receiving input from a user of the apparatus 100, e.g., via a keyboard, graphical user interface shown on a display of the apparatus 100, speech recognition circuitry, or an accessory device, such as a headset, and for providing output to the user via, e.g., a graphical user interface or a loudspeaker.

[0076] The memory 152 comprises a work memory 153 and a persistent (non-volatile, NA / ) memory 156 configured to store computer program code 157 and data 158. The memory 156 may comprise any one or more of: a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), a random-access memory (RAM), a flash memory, a data disk, an optical storage, a magnetic storage, a smart card, a solid state drive (SSD), or the like.

[0077] The apparatus 100 may comprise a plurality of memories 156. The memory 156 may be constructed as a part of the apparatus 100 or as an attachment to be inserted into a slot, port, or the like of the apparatus 100 by a user or by another person or by a robot. The memory 156 may serve the sole purpose of storing data, or be constructed as a part of an apparatus 100 serving other purposes, such as processing data.

[0078] A skilled person appreciates that in addition to the elements shown in Fig. 13, the apparatus 100 may comprise other elements, such as microphones, displays, as well as additional circuitry such as an input / output (I / O) circuitry, memory chips, application-specific integrated circuits (ASIC), a processing circuitry for specific purposes such as a source coding / decoding circuitry, a channel coding / decoding circuitry, a ciphering / deciphering circuitry, and the like. Additionally, the apparatus 100 may comprise a disposable or rechargeable battery (not shown) for powering the apparatus 100 if an external power supply is not available. Further, it is noted that only one apparatus 100 is shown in Fig. 13, but certain embodiments may equally be implemented in a cluster of shown apparatuses, or the apparatus 100 may comprises remote parts operated over a network, or by using a cloud service.

[0079] The apparatus 100 comprises the (at least one) processor 151 and (at least one) memory 152 including computer program code 157, the memory 152 and the computer program code 157 being configured, with the processor 151 , to cause the apparatus 100 to perform the operations as disclosed in the preceding disclosure. These operations include, inter alia, predicting an amount of defects or extractive amount in final pulp based on measured hydrophobicity of a filtrate at a brown stock washing stage and / or a filtrate upstream of a bleaching stage, and recommending an action to be taken to alter the amount of defects or extractive amount in final pulp based on said predicting.

[0080] In the embodiments presented above, an amount of defects or extractive amount in final pulp is predicted. In certain embodiments, hydrophobicity is measured from a sample or side stream originating from the filtrate (in question) in an online analysis apparatus.

[0081] In certain embodiments, an amount of defects in final pulp is predicted based on both hydrophobicity and particle count(s) which will improve accuracy of the prediction in some embodiments. In certain embodiments, a total particle count of a sample is applied. In other embodiments, a particle count of particles of a predetermined size (such as agglomerates) is applied. In certain embodiments, the method comprises fractioning a sample (of the filtrate in question) to obtain particle fractions of different size. In certain embodiments, a particle count of particles of a predetermined mass is applied. In certain such embodiments, instead of particle size, the mass of the particles is used as the basis for fractionating.

[0082] Examples of recommended or further actions in embodiments of the present disclosure are as follows:

[0083] - controlling the addition of a chemical into a phase of the pulp production process (said phase may be upstream or downstream from the process phase or stage whose filtrate is used as a basis for the prediction) or adjusting said controlling changing a process parameter or process conditions of the pulp production process.

[0084] Examples of the chemicals are fixatives, dispersing agents, defoamers, and process chemicals.

[0085] More specific examples of afore-mentioned actions to be taken are:

[0086] - adding dispersing agent to a washer (brown stock washer or washer at a bleaching stage);

[0087] - adding more dilution water to a washer (brown stock washer or washer at a bleaching stage).

[0088] Examples of afore-mentioned actions at the drying machine section are:

[0089] - modifying water circulation (e.g., freshwater usage, opening water loop from specific point(s)), dosing of deposit control chemicals

[0090] At the drying machine section, hydrophobicity can be measured and corrective (or opposite) actions performed, e.g., at the circulation water tank 41 , at the circulation water tower 42 or at felt water 43.

[0091] Depending on the implementation, brown stock washing stage(s) each comprises a washer and bleaching stage(s) each comprises a reactor and a washer. In preceding embodiments, when it has been disclosed that e.g. hydrophobicity of a filtrate is measured, the measurement is preferably performed from a filtrate of a washer concerned.

[0092] In certain embodiments, the recommended action is subject to the prediction exceeding or falling below a threshold limit.

[0093] In certain embodiments, the method comprises: timing the recommended action to focus on the exact pulp whose filtrate was used as a basis for the predicting. It is understood that the pulp in the pulp production process has a predetermined lead time. By taking this into account, it can be confirmed that the recommended action will focus on the pulp at an implementation point at a correct time (thus taking into account a delay between a point of measurement and a point at which the recommended action is implemented).

[0094] The hydrophobicity measurements, predicting, and recommending actions may be performed continuously or repeated as needed (e.g., at certain intervals).

[0095] In certain cases, the pulp mill lacks certain process features, e.g., the bleaching section altogether and / or some features of the drying machine section or the drying machine section altogether. In those cases, the final pulp may be e.g. wet pulp (for use at a subsequent paper mill). However, the presented disclose is also applicable to those cases.

[0096] It is understood that the pulp production process is composed of a plurality of process stages (or steps). In yet further embodiments, the term final pulp refers, depending on the interpretation, to pulp that is output from a process stage and will enter a next process stage (e.g., during bleaching or during brown stock washing) the pulp therefore being “final” as far as the process stage in question is concerned. In these embodiments, when an amount of defects or extractive amount in final pulp is predicted in accordance with the present disclosure, the subject of the prediction is an intermediate product rather than a final product of the whole pulp mill. What has been described in the previously presented embodiments apply to these embodiments as well.

[0097] EXAMPLES

[0098] Certain examples illustrating the usage of the presented disclosure are explained as follows.

[0099] Example 1

[0100] Hydrophobicity is measured from washing filtrate(s) of brown stock

[0101] - Wood extractive concentration of dried pulp (end product of drying machine) is predicted (forecast of wood extractives is obtained ~ 6-20 hours in advance time to react)

[0102] - Wood extractive concentration of dried pulp is controlled by: o e.g., controlling dispersing agent addition and / or controlling dilution water addition to the process stage(s) (in brown stock washing or in bleaching stages) if the prediction exceeds a threshold limit or the prediction is under a threshold limit. Optionally, hydrophobicity is measured from bleaching filtrates (from the washers)

[0103] - Wood extractive concentration of dried pulp is predicted (the forecast of wood extractives several hours in advance)

[0104] - The wood extractive concentration of dried pulp is controlled (finetuning if needed, to check the response of the first control action to the wood extractive of dried pulp). Control action(s) to the brown stock and / or bleaching stages are performed.

[0105] Optionally, hydrophobicity is measured from drying machine filtrates

[0106] - Wood extractive concentration of dried pulp is predicted (the forecast of wood extractives few hours in advance)

[0107] - The wood extractive concentration of dried pulp is controlled (finetuning if needed, to check the response of the first and / or second control action to the wood extractive of dried pulp). Control action(s) to the drying machine, e.g., open the water circulation are performed.

[0108] Example 1 is well suited for anticipating major disturbances. Primarily, there are provided possibilities to influence the amount of extractives in brown stock processing. Fine-tuning can be made during bleaching and yet at the drying machine section.

[0109] Example 2

[0110] Hydrophobicity is measured from washing filtrates of one or more bleaching stages

[0111] - Wood extractive concentration of dried pulp is predicted (forecast of wood extractives is obtained several hours in advance time to react)

[0112] - The wood extractive concentration of dried pulp is controlled by: o e.g., controlling dispersing agent addition and / or controlling dilution water addition to the process stage(s) (in brown stock washing or in bleaching stages) if the prediction exceeds a threshold limit or the prediction is under a threshold limit.

[0113] Optionally, hydrophobicity is measured from drying machine filtrates

[0114] - Wood extractive concentration of dried pulp is predicted (the forecast of wood extractives few hours in advance)

[0115] - The wood extractive concentration of dried pulp is controlled (finetuning if needed, to check the response of the first control action to the wood extractive of dried pulp). Control action(s) to the drying machine, e.g., open the water circulation are performed.

[0116] Hydrophobicity is measured from washing filtrate(s) of brown stock

[0117] - Defects of dried pulp (end product of drying machine) are predicted (forecast of defects is obtained ~ 6-20 hours in advance time to react)

[0118] - The amount of defects of dried pulp is controlled by: o e.g., controlling dispersing agent addition and / or controlling dilution water addition to the process stage(s) (in brown stock washing or in bleaching stages) if the prediction exceeds a threshold limit or the prediction is under a threshold limit.

[0119] Optionally, hydrophobicity is measured from bleaching filtrates (from the washers)

[0120] - Defects of dried pulp are predicted (the forecast of defects several hours in advance)

[0121] - The amount of defects of dried pulp is controlled (finetuning if needed, to check the response of the first control action to defects of dried pulp). Control action(s) to the brown stock and / or bleaching stages are performed.

[0122] Optionally, hydrophobicity and particle counts (e.g., total, agglomerates) are measured from drying machine filtrates

[0123] - Defects of dried pulp are predicted (the forecast of defects few hours in advance)

[0124] - The defects of dried pulp are controlled (finetuning if needed, to check the response of the first and / or second control action to defects of dried pulp). Control action(s) to the drying machine, e.g., open the water circulation are performed.

[0125] Hydrophobicity and optionally particle counts are measured from washing filtrate(s) of brown stock

[0126] - Defects of dried pulp are predicted (forecast of defects is obtained ~ 6-20 hours in advance time to react)

[0127] - The amount of defects of dried pulp is controlled by: o e.g., controlling dispersing agent addition and / or controlling dilution water addition to the process stage(s) (in brown stock washing or in bleaching stages) if the prediction exceeds a threshold limit or the prediction is under a threshold limit.

[0128] Optionally, hydrophobicity and optionally particle counts are measured from bleaching filtrates (from the washers)

[0129] - Defects of dried pulp are predicted (the forecast of defects several hours in advance)

[0130] - The amount of defects of dried pulp is controlled (finetuning if needed, to check the response of the first control action to defects of dried pulp). Control action(s) to the brown stock and / or bleaching stages are performed.

[0131] Optionally, hydrophobicity and particle counts (e.g., total, agglomerates) are measured from drying machine filtrates

[0132] - Defects of dried pulp are predicted (the forecast of defects few hours in advance)

[0133] - The defects of dried pulp are controlled (finetuning if needed, to check the response of the first and / or second control action to defects of dried pulp). Control action(s) to the drying machine, e.g., open the water circulation are performed.

[0134] Example 5

[0135] Hydrophobicity and optionally particle counts are measured from bleaching filtrates (from the washers)

[0136] - Defects of dried pulp are predicted (the forecast of defects several hours in advance)

[0137] - The amount of defects of dried pulp is controlled by: o e.g., controlling dispersing agent addition and / or controlling dilution water addition to the process stage(s) (in brown stock washing or in bleaching stages) if the prediction exceeds a threshold limit or the prediction is under a threshold limit. Optionally, hydrophobicity and particle counts (e.g., total, agglomerates) are measured from drying machine filtrates

[0138] - Defects of dried pulp are predicted (the forecast of defects few hours in advance)

[0139] - The defects of dried pulp are controlled (finetuning if needed, to check the response of the first control action to defects of dried pulp). Control action(s) to the drying machine, e.g., open the water circulation are performed.

[0140] Without limiting the scope and interpretation of the patent claims, certain technical effects of one or more of the example embodiments disclosed herein are listed in the following. A technical effect is improved control of hydrophobic components in a pulp production process. A further technical effect is improved possibilities to influence the quality of final pulp through predicting the amount of defect or extractive amount at an early stage of the pulp production process.

[0141] Various embodiments have been presented. It should be appreciated that in this document, words comprise, include and contain are each used as open-ended expressions with no intended exclusivity.

[0142] The foregoing description has provided by way of non-limiting examples of particular implementations and embodiments a full and informative description of the best mode presently contemplated by the inventors for carrying out the invention. It is however clear to a person skilled in the art that the invention is not restricted to details of the embodiments presented in the foregoing, but that it can be implemented in other embodiments using equivalent means or in different combinations of embodiments without deviating from the characteristics of the invention.

[0143] Furthermore, some of the features of the afore-disclosed example embodiments may be used to advantage without the corresponding use of other features. As such, the foregoing description shall be considered as merely illustrative of the principles of the present invention, and not in limitation thereof. Hence, the scope of the invention is only restricted by the appended patent claims.

Claims

CLAIMS1 . A method, comprising: predicting an amount of defects in final pulp or extractive amount in final pulp of a pulp production process based on measured hydrophobicity of a filtrate at a brown stock washing stage and / or a filtrate upstream of a bleaching stage; and recommending an action to be taken to alter the amount of defects or extractive amount in final pulp based on said predicting.

2. The method of claim 1 , comprising: using historical data of the pulp production process in the predicting of an amount of defects in final pulp or extractive amount in final pulp.

3. The method of claim 1 or 2, comprising: measuring hydrophobicity from a sample or side stream originating from the filtrate in an online analysis apparatus.

4. The method of claim 3, comprising: predicting an amount of defects in final pulp based together on hydrophobicity and particle count(s).

5. The method of any preceding claim, comprising: predicting an amount of defects in final pulp or extractive amount in final pulp of a pulp production process based on measured hydrophobicity of a filtrate at a brown stock washing stage; and recommending the action to be taken at the brown stock washing stage or at a bleaching stage.

6. The method of any preceding claim, comprising: timing the recommended action to focus on the exact pulp whose filtrate was used as a basis for the predicting.

7. The method of any preceding claim, comprising:further predicting the amount of defects in the final pulp or extractive amount in the final pulp based on measured hydrophobicity of a filtrate at a point of the pulp production process where the pulp has already undergone the recommended action; and indicating whether a further action needs to be taken to alter the amount of defects or extractive amount in final pulp based on said further predicting.

8. The method of claim 7, wherein the further predicting is performed based on measured hydrophobicity of a filtrate from a drying machine section of the pulp production process.

9. The method of any preceding claim, wherein predicting an amount of defects in final pulp or extractive amount in final pulp comprises predicting an amount of defects in dried pulp or extractive amount in dried pulp.

10. A method, comprising: monitoring hydrophobicity at two points of a pulp production process and predicting an amount of defects in final pulp or extractive amount in final pulp based on said monitoring.11 . The method of claim 10, comprising: recommending an action to be taken to alter the amount of defects or extractive amount in final pulp based on predicting on the basis of monitoring hydrophobicity at a first point of the two points of the pulp production process.

12. The method of claim 11 , comprising: verifying the effect of the recommended action based on predicting on the basis of monitoring hydrophobicity at a second point of the two points of the pulp production process.

13. The method of claim 12, comprising: indicating whether there is a need for a further action to be taken to alter the amount of defects or extractive amount in final pulp based on the verifying.

14. An apparatus, comprising: at least one processor; and at least one memory including computer program code, the at least one memory and the computer program code being configured, with the at least one processor, to cause the apparatus to perform the method of any of claims 1-13.

15. A computer program comprising computer executable program code which when executed by a processor causes an apparatus to perform the method of any of claims 1-13.

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