Biocide management in papermaking

Abstract

A method for controlling papermaking, comprising: monitoring the liquid level of a fibrous suspension in a reservoir (302); identifying that the liquid level has dropped so as to meet at least one empty criterion (303), and then identifying that the liquid level has risen so as to meet at least one replenishment criterion; and starting to administer a biocide to the fibrous suspension flowing into the reservoir in response to identifying that the liquid level has risen so as to meet at least one replenishment criterion. A corresponding device and computer program are also disclosed.

Description

Technical Field

[0001] The disclosure of this specification (hereinafter referred to as "this disclosure") generally relates to biocide control in papermaking. In particular, this disclosure relates to (but is not limited to) biocide control in papermaking using recycled fibers. Background

[0002] Note that this section describes useful background information, but it is not to be construed as admitting that the techniques described herein represent the state of the art.

[0003] Recycled fibers, i.e., secondary fibers, can be obtained as raw materials from, for example, recycled cardboard boxes. Such recycled fiber raw materials often contain a lot of starch, which is a common strength additive. Starch can cause the growth of microorganisms together with various impurities resulting from, for example, the recycling of food packages. Liners and flutes are components of cardboard. In the manufacturing process of using recycled fibers for the production of liners and flutes, microbiological problems such as the inadvertent generation of volatile fatty acids often plague the process. As a result, foul odors are likely to occur in the manufacturing environment and the final board. At the same time, the pH generally decreases and the conductivity increases. Due to the effects of these microbial activities, the wet end becomes unstable, leading to problems in operability or the generation of explosive gases. In large storage towers for process water, fiber suspensions, and brokes, the residence time tends to be long, so the above problems may become more serious. Storage towers for recycled fiber suspensions are particularly vulnerable to these problems. The volume of such towers is usually huge, ranging from hundreds to thousands of cubic meters. The nominal pulp residence time in such towers may be only a few hours. However, the consistency of the fibrous suspension in such towers can be quite high, such as 3 - 12% or up to 20%. A bottom mixer may be provided to circulate the contents of the tower. However, the influence of the bottom mixer may only reach the very bottom of the tower volume, for example, one-tenth or one-fifth of the tower volume.

[0004] These storage towers are usually filled from the top. In some cases, additional fiber suspension is pumped through a pipeline by a powerful pump up to the top of the storage tower, which is 10 meters or even 30 meters higher than the bottom of the tower. At the top of the storage tower, the flow of this additional fiber suspension is jetted downward with great force. This can cause a channeling effect. That is, near the surface of the tower, the fiber suspension flowing in at the entry point will move downward much faster than the fiber suspension at the end of the same tower. It can be imagined that such a tower may contain a zone of pulp that moves very slowly, in contrast to the main flow passing through the tower, regardless of the total volume. It can be understood that such a slowly moving zone may contain materials that have stayed for several days. Such substances provide a specific microbiological habitat. Such zones include habitats suitable for the growth of anaerobic bacteria and may have extremely high fermentation activity. Furthermore, the content of anaerobic cellulose-decomposing bacteria may also increase. The larger these low-flow zones become and the higher the microbial activity, the more they affect the main flow passing through the tower. This is because some of the substances in these zones are mixed into the main flow, and the anaerobic core of the low-flow zone also causes the fermentation and decay of the fiber suspension to progress.

[0005] The adverse effects caused by the growth of microorganisms may appear in papermaking when the surface height of the tower decreases and the pulp begins to flow out of such slow-moving zones, bringing a large amount of rotten raw materials to the papermaking process.

[0006] Unfortunately, once such low-flow zones are formed, the microbiological habitat hardly changes with the addition of biocides to the storage tower inlet or direct addition to the storage tower. Once the low-flow zones are formed, the biocides can no longer reach these zones, leaving an impact on the main flow and posing a risk that the main flow will be overly chemicalized. Abstract

[0007] The appended claims define the scope of protection. Matters not covered by the claims among the examples of devices, products and / or methods and technical descriptions in the description and / or drawings of this specification are presented as background art or examples useful for understanding the present invention, rather than as embodiments of the present invention.

[0008] In this document, papermaking refers to making any one of paper, liner, flute, tissue paper, cardboard, and thick paper.

[0009] According to a first exemplary aspect, a method for controlling papermaking is provided. This method includes monitoring the liquid level (height of the liquid surface) of the fibrous suspension in the reservoir; identifying that the liquid level has dropped to meet at least one empty criterion, and then identifying that the liquid level has risen to meet at least one replenishment criterion; initiating the administration of a biocide to the fibrous suspension entering the reservoir in response to identifying that the liquid level has risen to meet the at least one replenishment criterion; and includes.

[0010] The at least one empty criterion refers to the reservoir becoming partially empty. The at least one empty criterion may be defined such that when satisfied, the reservoir still contains at least a minimum amount of fibrous suspension. The minimum amount may be at least 15%, or 20%, or 30%, or 40% of the capacity of the reservoir. The minimum amount is large enough so that biocide administration is carried out before the liquid level drops significantly near the bottom of the reservoir. On the other hand, if at least one empty criterion can be triggered at a high liquid level where the additionally administered biocide does not effectively reach the low flow rate zone, there is a risk of unnecessary administration. For this reason, 30%, 35%, 40% are considered particularly suitable values for the minimum amount.

[0011] The capacity of the reservoir is at least 200m 3, more preferably at least 500 m 3 , still more preferably at least 800 m 3 .

[0012] The at least one empty criterion may include that the liquid level has dropped to a predetermined lower threshold, such as the minimum amount. The lower threshold may be defined as a predetermined height. Alternatively, the lower threshold may be dynamically defined as a decrease in the liquid level. The lower threshold may correspond to, for example, preferably at least 10%, more preferably at least 20%, still more preferably at least 30% of the capacity of the reservoir. The at least one empty criterion may further include a reduction period that defines a maximum time (such as 1 hour or 2 hours) during which a reduction must occur.

[0013] The lower threshold may be adaptively defined based on past measurements of the microbial activity in the reservoir. The microbial activity in the reservoir may be measured continuously, periodically, aperiodically, or repeatedly. The microbial activity may be measured when an increase in microbial activity is suspected. The microbial activity may be measured when an increase in microbial activity risk is detected. The lower threshold may be adaptively defined based on microbial activity measurements performed during a microbial activity measurement period. The microbial activity measurement period may include at least the previous 10 minutes, 30 minutes, 1 hour, 6 hours, 12 hours, 24 hours, or 72 hours. The microbial activity measurement period may include at most 30 minutes before, 1 hour before, 6 hours before, 12 hours before, 24 hours before, 72 hours before, or 1 week before. The microbial activity measurement results may be compared to a predetermined baseline indicating a desired and / or acceptable amount of microbial activity.

[0014] If it is detected in the reservoir that the microbial activity is high and / or increasing, the lower threshold value may be increased. By doing so, the empty criterion is more easily satisfied, and early biocide administration is promoted. If it is detected that the microbial activity in the reservoir is low and / or decreasing, the lower threshold value may be decreased. In this way, the empty criterion is not so easily satisfied, and unnecessary biocide administration is more easily avoided.

[0015] The at least one replenishment criterion refers to partial replenishment of the reservoir. The at least one replenishment criterion may include that the liquid level has risen to an upper threshold value. The upper threshold value may be defined as a predetermined height. Alternatively, the upper threshold value may be defined as an increment in the liquid level from the cycle bottom liquid level, which is defined as the minimum liquid level between satisfying the at least one empty criterion and satisfying the at least one replenishment criterion after satisfying the at least one empty criterion. This increment may correspond to 0.1% to 5% of the storage capacity of the reservoir.

[0016] The at least one empty criterion may include that a predetermined update period has elapsed since the liquid level in the reservoir last satisfied the at least one empty criterion. The update period is preferably at least 24 hours, more preferably at least 36 hours, and even more preferably 48 hours.

[0017] The at least one replenishment criterion may include that the liquid level has risen at a predetermined rate during the rising period. The rising rate of the liquid level during the rising period corresponds to at least 20% to at least 50% of the storage capacity per hour. The rising period may be at least 30 seconds, 60 seconds, 180 seconds, or 300 seconds. A period of at least 30 seconds can be advantageous as it can provide a quick indication of the start of filling if the rising rate over that period is sufficiently large. The rising period of at least 60 seconds better takes into account fluctuations in the measured values and is still relatively fast. The rising period of 180 seconds further reduces the risk of premature start of the biocide administration. In the rising period of 300 seconds, the possibility of a premature start is still low. Although a layer of a certain height may be formed during that period, still, if the increase has any meaning, the next inflow is also likely to come at a rate that causes a turbulent flow that mixes the incoming biocide into the lower fibrous suspension. Thus, the administration can be sufficiently extended deep into the slow-moving zones or pockets within the reservoir.

[0018] The administration of the biocide may end when the liquid level meets a predetermined end level threshold. The end level threshold may correspond to at least 80% or 90% of the capacity of the reservoir. Alternatively, it may correspond to, for example, up to 1% or 5% of the reservoir capacity below the replenishment height (at which the reservoir is replenished).

[0019] The administration of the biocide may end when the rise in the liquid level meets a predetermined end rise threshold. The predetermined end rise threshold may correspond to at least 20 percentage points or 40 percentage points of the storage capacity of the reservoir.

[0020] The administration of the biocide may continue during the continuous period. The continuous period may be at least 2 hours, or 3 hours, or 5 hours. The continuous time may be at most 3 hours, or 4 hours, or 10 hours.

[0021] The administration may be performed in proportion to the inflow rate of the fibrous suspension flowing into the reservoir. The administration may be targeted at a range between 5 mg / l and 300 mg / l. The administration may be between 10 mg / l and 50 mg / l for bronopol, or CMIT, or MIT. In the case of glutaraldehyde, the administration may be in the range from 50 mg / l to 200 mg / l.

[0022] The administration may be targeted at the additional fibrous suspension flowing into the reservoir within the reservoir. The administration may be targeted at the fibrous suspension flowing in through the supply line. Alternatively, or additionally in part, the administration may be targeted at the fibrous suspension flowing into the reservoir after flowing into the reservoir.

[0023] The administration may be targeted at the fibrous suspension within the reservoir.

[0024] The fibrous suspension may flow into the reservoir through the first end of the reservoir. The fibrous suspension may be discharged from the reservoir through the second end of the reservoir, which may be opposite to the first end of the reservoir.

[0025] The reservoir may be a storage tower. The reservoir may have a calculated residence time exceeding 2 hours.

[0026] The residence time of the fibrous suspension in the reservoir may be monitored. When the residence time meets a first time threshold (such as 4 days, 5 days, 6 days, 7 days, 8 days or 9 days, etc.), a first signal may be output. The first signal may indicate a cause of signal such as an aging event. The first signal may be output to a user interface. The first signal may also be output to a process control loop for relaxation measures. The relaxation measures may include at least partially emptying the reservoir. When the residence time meets a second time threshold (such as 48 hours, etc.), or when the pH or rH changes and meets the pH change threshold or rH change threshold respectively, a second signal may be output. The second signal may indicate a cause of signal such as an intermediate degradation risk event. The second signal may be output to a user interface. The second signal may also be output to a process control loop for relaxation measures. The relaxation measures may include at least partially emptying the reservoir.

[0027] The reservoir may be cylindrical. In some embodiments, the reservoir has a height that is at least 1 times, or 2 times, or 5 times, or 10 times the diameter.

[0028] The fibrous suspension may contain cellulose and hemicellulose. Also, the dry matter content in its aqueous suspension is at most 1 wt%, or 2 wt%, or 10 wt%, or 20 wt%.

[0029] The fibrous suspension may contain cellulose and hemicellulose. Also, the dry matter content in its aqueous suspension is at least 0.5 wt%, or 1 wt%, or 2 wt%, or 10 wt%, or 20 wt%.

[0030] The method may include quantifying anaerobic bacteria in the reservoir. The quantification may be performed continuously. The quantification may be performed periodically, for example, once a week or once a month. The quantification may be performed aperiodically, for example, within 1 to 100 days. The quantification may be repeated. The quantification may be performed using one or more laboratory tests. The quantification may be performed using a DNA detection method. The quantification may include detecting the total amount of bacteria. The quantification may include detecting the relative amount or relative number of a predetermined bacterium.

[0031] The method may further include adjusting the administration mode according to the quantification of anaerobic bacteria in the reservoir. The method may further include adjusting the administration mode according to an administration schedule. The method may further include adjusting the administration mode according to the current liquid level (height of the liquid surface). The method may further include adjusting the administration mode according to the current filling rate of the reservoir during filling.

[0032] The adjustment may include increasing or decreasing the dosage of the biocide. The administration mode may be adjusted by changing the composition and / or concentration of the biocide. The biocide may be produced by mixing two or more biocide components. The biocide components may be independently suitable for the use of the biocide.

[0033] The biocide may include a non-oxidizing biocide. The biocide may include an oxidizing biocide. The biocide may include a non-oxidizing biocide and a non-oxidizing biocide.

[0034] The oxidizing biocide may be selected from monochloramine (MCA); sodium hypochlorite; active chlorine generated from sodium chloride by electrolysis; chlorine dioxide or a stabilized chlorine compound. The stabilized chlorine compound includes a reaction product between active chlorine and a nitrogenous reactant. The nitrogenous reactant is selected from ammonium salts; urea; ammonium carbamate or dimethylhydantoin; performic acid; preferably monochloramine; ammonium salts reacted with hypochlorite; urea reacted with hypochlorite; dimethylhydantoin reacted with hypochlorite; performic acid; monohalodimethylhydantoin; dihalodimethylhydantoin; any combination thereof.

[0035] The non-oxidizing biocide may be selected from glutaraldehyde; bronopol; 2,2-dibromo-3-nitrilopropionamide (DBNPA); 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT); 2-methyl-4-isothiazolin-3-one (MIT); 2-n-octyl-4-isothiazolin-3-one (OIT); 4,5-dichloro-2-(n-octyl)-4-isothiazolin-3-one (DCOIT); 1,2-benzisothiazolin-3-one (BIT); 2-(thio-cyano-methylthio) benzothiazole (TCMTB); methylene dithiocyanate (MBT); tetrakis (hydroxymethyl) phosphonium sulfate (THPS); sodium dimethyldithiocarbamate; didecyldimethylammonium chloride (DDAC); alkyldimethylbenzylammonium chloride (ADBAC), preferably glutaraldehyde; bronopol; 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT); 2-methyl-4-isothiazolin-3-one (MIT); any combination thereof.

[0036] The method may include administering a biocide to mitigate problems in slow-moving zones in response to meeting the at least one empty criterion and the at least one replenishment criterion. The method may further include administering the same or a different biocide, such as an oxidizing biocide, a non-oxidizing biocide, or both an oxidizing biocide and a non-oxidizing biocide, to reduce overall microbial activity. These may be administered either continuously or as frequent shocks. In such cases, the method includes a first biocide treatment and a second biocide treatment. The second biocide treatment is carried out in response to identifying that the liquid level of the fibrous suspension in the reservoir meets the at least one empty criterion and the at least one replenishment criterion. The first biocide treatment may be carried out repeatedly, and / or continuously, and / or periodically, and / or aperiodically. The first biocide treatment may be emphasized to increase its impact on the formation of low-flow zones when the second biocide treatment is carried out. When the method includes additionally administering the same or a different biocide in response to identifying that the at least one empty criterion and the at least one replenishment criterion are met, the start of the administration may mean the start of the administration conditional on these criteria. Further, when the method includes additionally administering the same or a different biocide in response to identifying that the at least one discharge criterion and the at least one replenishment criterion are met, the stop of the administration may mean the stop of the administration conditional on these criteria.

[0037] The first biocide treatment may be performed using a non-oxidizing biocide, and the second biocide treatment may also be performed using a non-oxidizing biocide. The first biocide treatment may be performed using an oxidizing biocide, and the second biocide treatment may be performed using a non-oxidizing biocide. The first biocide treatment may be performed using an oxidizing biocide and a non-oxidizing biocide, and the second biocide treatment may be performed using a non-oxidizing biocide. The first biocide treatment may be performed using an oxidizing biocide and a non-oxidizing biocide, and the second biocide treatment may be performed using an oxidizing biocide and a non-oxidizing biocide. The first biocide treatment may be performed using a non-oxidizing biocide, and the second biocide treatment may be performed using an oxidizing biocide. The first biocide treatment may be performed using an oxidizing biocide, and the second biocide treatment may be performed using an oxidizing biocide. The first biocide treatment may be performed using an oxidizing biocide and a non-oxidizing biocide, and the second biocide treatment may be performed using an oxidizing biocide.

[0038] In the first biocide treatment with the biocide, the oxidizing biocide may be selected from active chlorine released from sodium hypochlorite; active chlorine generated from sodium chloride by electrolysis; chlorine dioxide or a stabilized chlorine compound. Here, the stabilized chlorine compound includes a reaction product between active chlorine and a nitrogenous reactant. The nitrogenous reactant is selected from ammonium salts, urea, ammonium carbamate or dimethylhydantoin. A preferred first biocide is monochloramine (MCA), which is a reaction product of active chlorine and an ammonium salt.

[0039] The inventor has noticed that the biocide has a sufficient impact on the low flow rate zones only for a relatively short time. This is when these low flow rate zones are formed. At this time, the reservoir begins to fill up, and the bulk pressure in the reservoir begins to affect the flow of the pulp in the reservoir, which gives rise to the possibility of forming a low flow rate zone different from the through-flow. At this time, the flow flowing into the reservoir should be treated with a biocide chemical suitable for affecting the low flow rate zone while the low flow rate zone is being formed. When administered in such a way, the concentration of the biocide needs to be kept appropriate in these low flow rate zones in order to suppress the activity of microorganisms. In particular, it needs to be kept appropriate until the procedure of lowering the liquid level and replenishing with the biocide is repeated. Increasing the dosage within the time window when these slow moving zones are formed can avoid excessive consumption of the biocide and is even more advantageous.

[0040] By lowering the liquid level of the storage tower, treating the increased low flow rate zones with an increased biocide while replenishing the reservoir, and repeating this procedure before the control of the low flow rate zones is lost, a more stable papermaking process can be achieved.

[0041] By performing such a booster treatment when at least one empty criterion and then at least one replenishment criterion are met, the booster treatment can be executed on demand at any time when the appropriate opportunity arrives, which is even more advantageous.

[0042] According to a second exemplary aspect, an apparatus for controlling the production of pulp or paper is provided. This apparatus comprises at least one processor and a memory containing program code, and the processor and the memory, as a whole, monitor the liquid level of the fibrous suspension in the reservoir; identify that the liquid level has dropped to meet at least one empty criterion, and then identify that the liquid level has risen to meet at least one replenishment criterion; In response to identifying that the liquid level has risen so as to meet the at least one replenishment criterion, start administering a biocide to the fibrous suspension entering the reservoir; is configured as such.

[0043] According to a third exemplary aspect, a computer program having computer-executable program code is provided. When this program code is executed by at least one processor, for the control of paper manufacturing, the apparatus is caused to, monitor the liquid level of the fibrous suspension in the reservoir; identify that the liquid level has dropped so as to meet at least one empty criterion, and then identify that the liquid level has risen so as to meet at least one replenishment criterion; in response to identifying that the liquid level has risen so as to meet the at least one replenishment criterion, start administering a biocide to the fibrous suspension entering the reservoir; is configured to perform.

[0044] According to a fourth exemplary aspect, a computer program product having a non-volatile computer-readable medium storing the computer program of the third exemplary aspect is provided.

[0045] According to a fifth exemplary aspect, an apparatus is provided that comprises means for performing the method of any of the preceding aspects.

[0046] The aforementioned computer-readable medium may be composed of a digital data storage device such as a data disk or a floppy disk, an optical storage device, a magnetic storage device, a holographic storage device, a magneto-optical storage device, a phase change memory, a resistive random access memory, a magnetic random access memory, a solid electrolyte memory, a ferroelectric random access memory, an organic memory, or a polymer memory. These storage media may be mounted on a vice without having functions substantially other than the storage function. Further, the storage media may be formed as a part of a device having other functions, and as a non-limiting example, may be a memory of a device such as a computer, a chipset, or a sub-assembly of an electronic device.

[0047] Although various aspects and embodiments have been presented, these are not presented for the purpose of limiting the scope of the invention. These embodiments have merely been used to explain specific aspects and steps that can be used in various implementations. Depending on the embodiment, it may be presented only with reference to specific exemplary aspects. It should be understood that the corresponding embodiments are also applicable to other aspects.

Brief Description of the Drawings

[0048] Some embodiments will be described with reference to the following attached drawings.

Figure 1

Figure 2

Figure 3a

Figure 3b

Figure 3c

Figure 3d

[0049] In the following description, like reference numerals denote like elements or steps.

[0050] FIG. 1 schematically shows a system 100 according to an exemplary embodiment. Four different filling states a) to d) of the fibrous suspension are shown. The system includes an injection line 110, a doser 120 for administering a biocide to the inflowing fibrous suspension into the injection line, a controller 130 for controlling the doser 120, a storage tower 140, and a bottom mixer 150 for mixing the fibrous suspension in the storage tower 140. In some embodiments, the system 100 further includes a pre-dosing device (not shown). The pre-dosing device performs a basic dosing of the biocide independently of the operation of the doser 120. In contrast, the doser 120 can perform a time-concentrated dosing to alleviate the problem of the slow-moving zone 160.

[0051] As the storage tower becomes full with additional fiber suspension and the bulk pressure in the storage tower begins to affect the flow of the stored pulp, a low-velocity flow zone begins to form. The low-flow velocity zone creates an environment inhabited by highly active anaerobic microorganisms that is different from the main flow passing through the storage tower.

[0052] FIG. 2 is a block diagram of an apparatus 200 according to an exemplary embodiment. The apparatus 200 includes a communication interface 210, a processor 220, a user interface 230, and a memory 240.

[0053] In an embodiment, the communication interface 210 includes wired and / or wireless communication circuits such as Ethernet, Wi-Fi, Bluetooth, GSM, CDMA, WCDMA, LTE, and / or 5G circuits. The communication interface can be integrated into the apparatus 200 or mounted as part of an adapter, card, etc. attachable to the apparatus 200. The communication interface 210 may support one or more different communication technologies. Also, the apparatus 200 may include one or more communication interfaces 210.

[0054] As used herein, the term "processor" may represent a central processing unit (CPU), a microprocessor, a digital signal processor (DSP), a graphics processing unit (GPU), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a microcontroller, or a combination of these elements.

[0055] The user interface may include a circuit for receiving input from a user of the device 200, for example, via a keyboard, a graphical user interface displayed on the display of the device 200, a voice recognition circuit, or an accessory such as a headset. Further, it may include a circuit for providing output to the user, for example, via a graphical user interface or a speaker.

[0056] The memory 240 includes a working memory 242 and a non-volatile memory 244 configured to store computer program code 246 and data 248. The memory 240 may include 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 device, a magnetic storage device, a smart card, a solid state drive (SSD), etc. The device 200 may include a plurality of memories 240. The memory 240 may be configured as part of the device 200, or as an attachment that is inserted into a slot or port of the device 200 by a user, another person, or a robot. The memory 240 may be intended only for storing data in some cases, or may constitute a part of the device 200 that serves another purpose such as data processing.

[0057] One skilled in the art would understand that, in addition to the elements shown in FIG. 2, the apparatus 200 may include other elements such as a microphone, a display, input / output (I / O) circuits, memory chips, application-specific integrated circuits (ASICs), source encoding / decoding circuits, channel encoding / decoding circuits, encryption / decryption circuits, and other application-specific processing circuits. Further, the apparatus 200 may include a disposable battery or a rechargeable battery (not shown) for supplying power to the apparatus 200 when an external power source is not available.

[0058] Next, various exemplary embodiments will be described with reference to FIGS. 3a to 3d showing flowcharts according to the exemplary embodiments. FIGS. 3a to 3d show various steps and some optional steps. Some embodiments may include additional steps and / or some of the steps may be executed multiple times.

[0059] 301: Supply the fibrous suspension to the reservoir through the injection line 110. In some embodiments, a basic biocide dosage is also administered. The basic biocide dosage is independent of fluctuations in the liquid level in the reservoir.

[0060] 302: Monitor the liquid level of the fibrous suspension in the reservoir. For example, monitor according to the measurement of the pressure and / or surface height of the storage tower by the control device 130.

[0061] 303: Identify that the liquid level has dropped to meet at least one empty criterion, and then identify that the liquid level has risen to meet at least one replenishment criterion. Then, in response to identifying that the liquid level has risen to meet at least one replenishment criterion, initiate the administration of a biocide to the fibrous suspension flowing into the reservoir. Depending on the embodiment, such administration may occur before the fibrous suspension enters the reservoir, simultaneously with its entry, or after it has entered. In some embodiments, the initiation of biocide administration starts an adaptive or conditional administration. The biocide for adaptive or conditional administration may, in some embodiments, be the same as or different from the biocide of an ongoing administration. In some embodiments, the ongoing administration can be continuous, periodic, or aperiodic.

[0062] 304: Define that the reservoir becomes partially empty according to the at least one empty criterion. At this time, even when the at least one empty criterion is met, define that the reservoir becomes partially empty such that the reservoir still contains at least a minimum amount of fibrous suspension. The minimum amount is, for example, at least 15%, or 20%, or 30%, or 40% of the reservoir's capacity.

[0063] 305: Use the fact that the liquid level has dropped to a predetermined lower threshold as one empty criterion. The lower threshold may be defined as a predetermined height, as an amount of drop in the liquid level, or may be dynamically defined based on past measurements of microbial activity.

[0064] 306: Define a partial replenishment of the reservoir according to at least one replenishment criterion. For example, define it such that the liquid level rises to an upper threshold. The upper threshold may be defined as a predetermined height. Alternatively, it may be defined as the amount of rise in the liquid level starting from the lowest liquid level reached before the liquid level starts to rise.

[0065] 307: Use whether the update period has elapsed since the liquid level in the reservoir dropped below the lower threshold as one empty criterion. The update period is, for example, at least 48 hours, or 60 hours, or 72 hours.

[0066] 308: Use the fact that the liquid level has risen at a predetermined rate during the rising period as one replenishment criterion. The predetermined rate may be, for example, a rise of at least 20% to at least 50% of the storage capacity per hour. The rising period may be, for example, at least 30 seconds, 60 seconds, 180 seconds, or 300 seconds.

[0067] 309: End the administration of the biocide when the liquid level reaches a predetermined end level threshold. The end level threshold may correspond to at least 80% or 90% of the reservoir capacity. Alternatively, it may correspond to, for example, a maximum of 1% or 5% of the reservoir capacity below the height to be replenished.

[0068] 310: End the administration of the biocide when the rise in the liquid level meets a predetermined end rise threshold. The end rise threshold may correspond to, for example, at least 20% points or 40% points of the storage capacity of the reservoir.

[0069] 311: Continue the administration of the biocide during the continuous period. The continuous period is at least 2 hours, or 3 hours, or 5 hours. And / or the continuous time is at most 3 hours, or 4 hours, or 10 hours.

[0070] 312: Administer in proportion to the inflow rate of the fibrous suspension flowing into the reservoir. For example, administer at several tens or several hundreds of mg / l to the fibrous suspension.

[0071] 313: Administer to the liquid flow in the injection line supplying the fibrous suspension to the reservoir.

[0072] 314: Perform all or part of the administration on the fibrous suspension in the reservoir.

[0073] 315: Receive the fibrous suspension into the reservoir through the first end of the reservoir.

[0074] 316: Discharge the fibrous suspension from the reservoir through the second end of the reservoir. This second end is on the side opposite to the first end.

[0075] 317: Use a storage tower as the reservoir. For example, use a storage tower such that the calculated residence time in the storage tower exceeds 2 hours.

[0076] 318: Monitor the residence time of the fibrous suspension. And for example, a first signal may be output when the residence time meets a first time threshold (such as 4 days, 5 days, 6 days, 7 days, 8 days or 9 days, etc.), and / or a second signal may be output when the residence time meets a second time threshold (such as 48 hours, etc.) and the pH or rH changes respectively meeting the pH change threshold or rH change threshold.

[0077] 319: As the fibrous suspension, use an aqueous suspension containing cellulose and hemicellulose and having a dry matter content of at most 1 wt%, or 2 wt%, or 10 wt%, or 20 wt%.

[0078] 320: As the fibrous suspension, use an aqueous suspension containing cellulose and hemicellulose and having a dry matter content of at least 0.5 wt%, or 1 wt%, or 2 wt%, or 10 wt%, or 20 wt%.

[0079] 321: Quantify the anaerobic bacteria in the reservoir and adjust the dosing according to the result. According to the embodiment, the quantification of anaerobic bacteria is performed continuously, or periodically, or irregularly, or repeatedly.

[0080] 322: In adjusting the dosing, increase or decrease the dosing amount of the biocide. This is done, for example, by changing the composition and / or concentration of the biocide.

[0081] 323: Use a biocide containing a non-oxidizing biocide.

[0082] 324: As the biocide, use any one or more of glutaraldehyde, bronopol, 2,2-dibromo-3-nitrilopropionamide (DBNPA), methylchloroisothiazolinone (CMIT), and methylisothiazolinone (MIT).

[0083] 325: When the liquid level is low or below a predetermined compliance threshold level, dynamically adapt the composition and / or concentration of the biocide. For example, use a more effective composition or a higher concentration, such as a concentration increased by 20% or 50%, for adaptation.

[0084] 326: In dosing control, adjust how much of a predetermined chemical is dosed into the fibrous solution.

[0085] 327: In dosing control, change the composition and concentration of the chemical.

[0086] 328: Administer an oxidizing biocide to reduce overall microbial activity or frequent shock.

[0087] 329: In response to meeting at least one empty criterion and at least one replenishment criterion, administer a biocide to mitigate problems in the low-flow zone, and in addition, administer an oxidizing biocide as a continuous dose or as a frequent shock to reduce overall microbial activity.

[0088] As will be understood by those skilled in the art, rH is the redox potential (ORP) adjusted by pH and temperature. As an example, rH can be calculated using the following formula. rH = 2·pH + 2·Eh·F / (2.3026·R·T) Here, Eh is the redox potential (V) measured using the standard hydrogen electrode, F is the Faraday constant (96485 C·mol-1 ) and R is the gas constant 8.314 J·K -1 ·mol -1 and T is the temperature in Kelvin (K) units.

[0089] Tests were conducted to verify the effectiveness of nine biocides against the microbiota in the RCF processes of four different mills. The bronopol-containing biocide products A (active ingredients DBNPA, bronopol, CMIT, MIT), B (active ingredients bronopol, CMIT, MIT), and C (bronopol) were the most efficient preservatives. They were able to prevent the growth of anaerobic bacteria and the decrease in pH for several days. When products A and B were used in combination with oxidizing agents (monochloramine, MCA), the growth of bacteria could be prevented at dosages from 10 mg / l to 30 mg / l for at least 7 days. This indicates that recycled fiber pulp can be stored for several days even under mill conditions. From these results, it is speculated that mixing in the recycled fiber pulp tower is insufficient to prevent the formation of a low-flow zone of old pulp. Based on the experiments, it seems sufficient to lower the fibrous suspension in the tower to a low liquid level once a week if booster dosing of the biocide (biocide administered in addition to the basic biocide treatment) is carried out at an appropriate time period (the time period when tower replenishment starts and it is possible to affect the low-flow zone). For example, the basic biocide treatment consists of regular dosing (continuous dosing or several times a day) of an oxidizing biocide such as MCA, and the booster dosing is automatically carried out at an appropriate time to reach the low-flow zone. This may be done only 5 to 10 times a month.

[0090] In further comparative tests, dosing according to the exemplary embodiments was found to result in improved quality in the recycled board while reducing the total consumption of biocide. The average bacterial content in the dry board decreased by 3.31 times, and the median bacterial content decreased by 1.18 times. These values are derived from the analysis of a total of 40 final products (boards) representing a 40-day period after dosing according to the exemplary embodiments, compared to the analysis of 40 examples of a similar period according to the old dosing strategy immediately prior to switching to the use of dosing according to this exemplary embodiment. The total consumption of the biocide product during the period when the method of use was changed was 3% lower than the comparative period, demonstrating that the bacterial control was improved by time-focused dosing rather than by increasing the amount of biocide used. In this experiment, the bacterial content in the dry board was quantified according to ISO standard 8784-1:2014 Pulp, paper and board - Microbiological examination, Part 1: Enumeration of bacteria and bacterial spores based on disintegration.

[0091] Various embodiments have been presented. Terms such as "having", "comprising", and "including" should be construed in an open-ended manner and do not exclude the presence of other elements.

[0092] The above description has provided a complete and useful explanation of the best mode contemplated by the inventors for practicing the present invention, using specific implementations and non-limiting examples of embodiments. However, as will be apparent to those skilled in the art, the details of the above embodiments do not limit the present invention, and other embodiments may be implemented using equivalent means or combinations of various embodiments without departing from the features of the present invention.

[0093] Furthermore, the features of the exemplary embodiments disclosed above may be used without using corresponding other features. However, the above description should be regarded as merely an example for explaining the principles of the present invention and not as limiting it. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for controlling papermaking, To monitor the liquid level of the fibrous suspension in the storage facility; Identifying that the liquid level has fallen to satisfy at least one empty criterion, and then identifying that the liquid level has risen to satisfy at least one replenishment criterion; In response to determining that the liquid level has risen to satisfy at least one of the replenishment criteria, the administration of a biocide to the fibrous suspension entering the storage is initiated; Methods that include...

2. The method according to claim 1, wherein the at least one empty criterion includes the liquid level falling to a lower threshold, the lower threshold preferably corresponds to at least 10%, more preferably at least 20%, and even more preferably at least 30% of the storage capacity.

3. The method according to claim 2, wherein the lower threshold is dynamically defined as a decrease in the liquid level, and the lower threshold preferably corresponds to at least 10%, more preferably at least 20%, and even more preferably at least 30% of the capacity of the storage.

4. The method according to claim 3, wherein the lower threshold is adaptively defined based on past measurements of microbial activity in the storage facility.

5. The method according to claim 4, wherein the aforementioned past measurements are based on one or more effects of the decomposition of the stored fibrous suspension, the effects being, for example, a decrease in pH and / or an increase in electrical conductivity.

6. The method according to Claim 1, The at least one replenishment criterion includes the liquid level rising by a predetermined amount from the cycle bottom liquid level, The cycle bottom liquid level is the lowest liquid level after the at least one empty criterion is met. The aforementioned predetermined increment corresponds to 0.1 to 5% of the storage capacity of the storage facility. method.

7. The method according to claim 6, wherein the at least one replenishment criterion includes an increase in the liquid level by a predetermined rate during the rising period, the rate of increase in the liquid level during the rising period being at least 20% to at least 50% of the storage capacity per hour.

8. The method according to claim 1, wherein the fibrous suspension contains regenerated fibers.

9. The method according to claim 1, further comprising terminating the administration of the biocide when the liquid level satisfies a predetermined termination height threshold, wherein the termination height threshold corresponds to at least 60%, more preferably 70%, even more preferably 80%, and most preferably 90% of the storage capacity of the storage, or to at most 1% or 5% of the storage capacity below the replenishment height at which the storage is replenished.

10. The method according to claim 1, further comprising terminating the administration of the biocide when the rise in the liquid level satisfies a predetermined termination rise threshold, wherein the termination rise threshold corresponds to at least 20%, 30%, or 40% of the storage capacity of the storage facility.

11. The method according to claim 1, wherein the dose is proportional to the amount of fibrous suspension that enters the reservoir.

12. The method according to claim 1, further comprising quantifying anaerobic bacteria and adjusting the dosage accordingly.

13. The method according to Claim 1, wherein the biocide is selected from the group consisting of oxidizing biocides and non-oxidizing biocides, However, the oxidizing biocide comprises monochloramine (MCA), sodium hypochlorite, activated chlorine produced from sodium chloride by electrolysis, chlorine dioxide, or a stabilized chlorine compound, the stabilized chlorine compound comprises a reaction product between activated chlorine and a nitrogenous reactant, the nitrogenous reactant is selected from ammonium salts, urea, ammonium carbamate or dimethylhydantoin, performic acid, preferably monochloramine (MCA), ammonium salts reacted with hypochlorite, urea reacted with hypochlorite, dimethylhydantoin, performic acid, or any combination thereof. The aforementioned non-oxidizing biocides include glutaraldehyde, bronopol, 2,2-dibromo-3-nitrilopropionamide (DBNPA), 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT), 2-methyl-4-isothiazolin-3-one (MIT), 2-n-octyl-4-isothiazolin-3-one (OIT), 4,5-dichloro-2-(n-octyl)-4-isothiazolin-3-one (DCOIT), 1,2-benzisothiazolin-3-one (BIT), 2-(thiocyanomethylthio)-benzothiazole (TCMTB), methylenedithiocyanate (MBT), This comprises tetrakis(hydroxymethyl)phosphonium sulfate (THPS), sodium dimethyldithiocarbamate, didecyldimethylammonium chloride (DDAC), alkyldimethylbenzylammonium chloride (ADBAC) (preferably glutaraldehyde), bronopol, 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT), 2-methyl-4-isothiazolin-3-one (MIT), or any combination thereof. Alternatively, the biocide is selected from a combination of the oxidizing biocide and the non-oxidizing biocide. method.

14. An apparatus comprising means for performing the method described in any one of claims 1 to 13.

15. A computer program comprising computer executable program code, which, when executed by the processing means of the device, causes the device to perform the method according to any one of claims 1 to 13.

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