JP2019214807A - Dirt accumulation amount estimation of wire and/or felt in papermaking process - Google Patents

Abstract

To provide a method for quantization of a dirt attached to a wire of a wire part of a paper machine or a felt of a press process without measuring a water content of the felt, thereby making usage of a cleaning agent be efficient.SOLUTION: In the method disclosed herein, based on a stationary turbidity included in a white water, amounts of calcium carbonate and pitches included in the white water used in a papermaking process are measured (step S9). Then, based on this measurement result, a dirt accumulation amount attached to a wire in a wire part 55 in a papermaking process and/or a felt in a press part 56 is calculated; based on this calculation result, an injection amount of an agent to the wire and the felt are obtained (step S12).SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method for estimating the amount of accumulated soil on wires and / or felt in a papermaking process.

  At present, papermaking is performed by making a raw material slurry in which a pulp raw material is dispersed in water quality. At the time of papermaking, the pulp is finally prepared into a pulp slurry through processes such as bleaching, beating, mixing, and dilution, and then sent to a wire part of a papermaking machine to be dewatered. As the pulp slurry is dewatered on the wire, the water filtered down the wire is commonly referred to as white water.

  From the viewpoint of effective utilization and reuse of water resources, white water is circulated through a papermaking system and a raw material system, and is reused as a recovered raw material or as diluted water. However, since white water contains dirt caused by calcium carbonate, starch, sizing agent, latex, casein, etc., by circulating white water through the papermaking system and the raw material system, the dirt components are concentrated, and the dirt components are reduced in the papermaking process. The effect on the pressing process is increased. The dirt component adheres to the wire in the papermaking process and the felt in the press process, and is mixed into the paper product, leading to deterioration in the quality of the paper product.

  When the yield of the raw material in the wire part of the paper machine decreases, the turbidity of the white water in the white water pit for collecting the white water that has passed without being captured by the wire increases. When the turbidity of the white water increases, the fluidity of the pipe through which the white water flows decreases, and slime cake is easily generated. When this grows and adheres to the inside of the white water silo or pipe and peels off, it causes a product defect or a cake hole defect.

  In addition, when the dirt component adheres to the felt in the pressing process, the water squeezing property is deteriorated, and it takes time to dry with a dryer at a subsequent stage, so that it is impossible to increase the papermaking speed, and the peeling property with the center roll is deteriorated. However, the production efficiency may be reduced, for example, a sheet break may occur.

  In order to suppress the turbidity of the white water, a part of the filtered water that has been filtered under the wire is discharged from the system and fresh water is introduced, but this alone does not provide a fundamental solution.

  For the purpose of preventing fouling, a fouling inhibitor composition containing (A) a nonionic surfactant and (B) a hydroxycarboxylic acid or a salt thereof is added to a shower water system in a papermaking process and a dewatering process in a papermaking process. (For example, see Patent Document 1).

JP 2010-163700 A

  However, up to now, it is not easy to continuously and quantitatively indicate the amount of dirt adhering to the wire in the wire part of the paper machine and the felt in the pressing step, and the antifouling agent composition has a constant amount of continuous. It is common to add them. Therefore, a large amount of cleaning agents such as a wire cleaning agent and a felt conditioner are required. These cleaning agents are relatively expensive, and it is required to provide a mechanism for reducing the amount of the cleaning agent used.

  In addition, in order to grasp the operating state of the felt, the moisture content of the felt may be measured, but this measurement is manually performed during the operation of the paper machine, and involves a risk.

  The present invention has been made in view of the above-described circumstances, and quantifies dirt adhering to a wire in a wire part of a paper machine and felt in a pressing process without measuring the moisture content of the felt, and using a cleaning agent. The purpose is to make the usage amount safe and efficient.

  The present inventors measure the amounts of calcium carbonate and pitch contained in the white water used in the papermaking process, and calculate the amount of accumulated dirt adhering to the wire and / or felt from the result of this measurement, so that dirt accumulation can be achieved. The inventors have found that the amount can be more accurately quantified and the amount of the detergent used can be minimized, thereby completing the present invention. Specifically, the present invention provides the following.

  (1) The present invention relates to a step of measuring the amounts of calcium carbonate and pitch contained in white water used in the paper making step, and the measurement of the amounts of calcium carbonate and pitch to determine the amount of the wire and / or the wire in the wire part of the paper making step. Or a step of calculating the amount of accumulated dirt adhering to the felt in the press part, and a method of estimating the amount of accumulated dirt on the wire and / or felt in the papermaking process.

  (2) The present invention further includes a step of measuring the amount of insoluble suspension contained in the white water used in the papermaking step, wherein the amount of accumulated dirt is a measurement result of the amount of the calcium carbonate and the pitch, The method according to (1), wherein the method is calculated from the measurement result of the amount of the insoluble suspension.

  ADVANTAGE OF THE INVENTION According to this invention, during operation | movement of a papermaking apparatus, since the amount of dirt accumulation of a wire and / or a felt in a papermaking process can be quantified more correctly, the usage of the cleaning agent provided to a wire and a felt is minimized. be able to. In addition, since quantification of the amount of accumulated soil does not require manual measurement of the moisture content of the felt during the operation of the paper machine, it is necessary to safely quantify the amount of accumulated soil and eventually reduce the amount of detergent used. Can be.

It is a mimetic diagram showing an example of the papermaking process to which the dirt accumulation amount estimation method concerning an embodiment of the present invention is applied. FIG. 2 is a schematic diagram showing an outline of a chemical injection system incorporated in the papermaking process shown in FIG. 1. FIG. 2 is a schematic diagram showing water balance in a papermaking system incorporated in the papermaking process shown in FIG. 1. It is a figure showing a rough processing procedure of a dirt accumulation amount estimation method concerning an embodiment of the present invention. It is a figure which shows the correlation between the calcium carbonate pitch density | concentration in white water and the calcium carbonate pitch density | concentration contained in felt squeeze by the dirt accumulation amount estimation method which concerns on embodiment of this invention. It is a figure which shows the correlation between the total organic carbon concentration in white water and the total organic carbon concentration contained in felt squeezed water by the dirt accumulation amount estimation method which concerns on embodiment of this invention. It is a figure which shows the relationship between a felt vacuum pressure and a felt dirt index when a felt cleaning agent is not used. It is a figure which shows the relationship between the felt vacuum pressure at the time of using a felt cleaning agent, and a felt dirt index.

  Hereinafter, embodiments of the present invention will be described, but the present invention is not particularly limited thereto.

<Paper making process 10>
The method according to the invention is used in a papermaking process. Therefore, before describing the method according to the present invention, the papermaking process will be described. FIG. 1 is a schematic diagram of a papermaking process 10 according to an example in which the method according to the present invention is performed. The papermaking process 10 includes a raw material system 40, a preparation / papermaking system 50, a collection system 60, and a chemical injection system 20.

[Raw material system 40]
The raw material system 40 includes tanks 41, 42, 43 and 44 for storing papermaking raw materials, a mixing chest 47, a machine chest 48, and a seed box 49. On the other hand, the preparation / papermaking system 50 includes a fan pump 51 that sends out the pulp slurry supplied from the raw material system 40, a cleaner 52, a screen 53, an inlet 54, a wire part 55, and a press part 56. It is comprised including. Further, the preparation / papermaking system 50 is provided with a white water silo 58 for storing white water, which will be described later. The recovery system 60 includes a seal pit 61, a recovery device 62, a recovered water tank 63, a disintegration water pump 64, and a concentrated water pump 65.

  The chemical injection system 20 includes a turbidity measuring unit 30 for measuring the turbidity of white water, an arithmetic processing unit 21 for controlling the amount of chemical added to each shower water, chemical tanks 22a and 22b, and a chemical injection pump. 23a and 23b.

  In the present embodiment, “white water” refers to an aqueous solution discharged from a paper machine in a large amount in a paper making process when making paper. The white water contains not only fine fibers derived from the raw pulp, but also other papermaking chemicals and the like.

  The raw material system 40 has a chemical pulp tank 41, a recycled pulp tank 42, a broke tank 43, and a recovered raw material tank 44. The chemical pulp tank 41 includes softwood bleached kraft pulp (LBKP), hardwood bleached kraft pulp (NBKP), and the like. In the chemical pulp and the recycled pulp tank 42, the recycled pulp in which the waste paper such as the deinked pulp (DIP) transferred from the deinking system and the corrugated cardboard waste paper is slurried by the waste paper pulp 45, The recovered pulp and the recovered raw material tank 44 contain pulp obtained by solid-liquid separation of white water by the recovery device 62 as a paper raw material.

  An apparatus for producing and supplying a paper raw material may be provided upstream of the chemical pulp tank 41. That is, upstream of the chemical pulp tank 41, a digester for digesting wood chips, a device for bleaching pulp, a screen for removing foreign matter, and the like may be provided. The broke tank 43 is supplied with the broke pulp generated after the press part 56.

  Disintegration water for disintegrating waste paper and broke is supplied from a disintegration water pump 64 to the waste paper pulper 45 and the broke pulper 46. The regenerated pulp, the broke pulp, the chemical pulp and the recovered raw material after being disintegrated by the pulpers 45 and 46 are combined with the concentrated water for adjusting the concentration from the concentrated water pump 65 and stored in each tank. In this embodiment, as the disintegration water and the concentrated water, recovered water of filtered white water is used. However, untreated filtered white water, fresh water, filtrate and dewatered water obtained by dewatering the slurry of the raw material system 40, and surplus water in other processes are used. Water may be used.

  The pulp contained in the chemical pulp tank 41, the recycled pulp tank 42, the broke tank 43, and the recovered material tank 44 is supplied to a mixing chest 47 at an appropriate ratio according to a brand to be manufactured. Mixed. The mixed pulp is transferred to a seed box 49 after papermaking chemicals are added in a machine chest 48.

[Formulation / papermaking system 50]
The pulp contained in the seed box 49 is sequentially supplied to the cleaner 52 and the screen 53 by the fan pump 51 of the preparation / papermaking system 50 together with the filtered white water from the later-described white water silo 58, where foreign substances are removed. Thereafter, it is supplied to the inlet 54. The inlet 54 supplies the pulp to the wire of the wire part 55 at an appropriate concentration, speed, and angle. The supplied pulp is dewatered by the wire part 55 and the press part 56, and is manufactured into paper via a reel winder (not shown).

  The water dewatered from the pulp in the wire part 55 and the press part 56 is received as white water in a white water pit 57 arranged below the wire part 55 and the press part 56. The white water received by the white water pit 57 is introduced into the white water silo 58 via the conduit 59 and stored therein.

[Recovery system 60]
Part of the white water stored in the white water silo 58 is supplied to the fan pump 51, and the rest is supplied to the seal pit 61. The white water supplied to the fan pump 51 dilutes the pulp slurry in the preparation / papermaking system 50. The white water supplied to the seal pit 61 is transferred to a collecting device 62, filtered and solid-liquid separated by the collecting device 62, and the filtrate is collected in a collected water tank 63.

  Here, the pulp slurry supplied from the inlet 54 to the wire part 55 includes, as a suspending substance, an insoluble suspension (SS), that is, pulp fiber having a length of 20 μm or more, and calcium carbonate added as a filler. Contains fine ash (suspendable material with a length of less than 20 μm) such as talc and talc. These insoluble suspensions (SS) and ash are respectively captured by the wire part 55, and the remainder is respectively filtered down the wire and dispersed in the white water. Therefore, white water is used as a suspending substance as an insoluble suspension (SS), that is, pulp fibers having a length of 20 μm or more, and fine ash (such as a length of less than 20 μm) such as calcium carbonate and talc added as a filler. Suspending substances).

[Drug injection system 20]
Hereinafter, the chemical injection system 20 will be described.

  A medicine tank 22a containing the medicine A is connected to a wire shower line and a felt shower line via a medicine injection pump 23a, and a medicine tank 22b containing the medicine B is connected via a medicine injection pump 23b. The chemical injection pumps 23a and 23b are electrically connected to an output side of an arithmetic processing unit 21 which forms a control unit described later, and a turbidity measurement unit 30 is electrically connected to an input side of the arithmetic processing unit 21. ing.

  The turbidity measuring unit 30 collects white water from a conduit 59 connected to the white water pit 57, measures the turbidity of the white water, and transmits the measurement result to the arithmetic processing unit 21. The arithmetic processing unit 21 operates the chemical injection pumps 23a and 23b in accordance with the transmitted measurement result, thereby injecting the amount of the chemical A in the chemical tank 22a into the shower water and the chemical B in the chemical tank 22b. Are respectively controlled.

  In the present embodiment, a papermaking chemical containing a wire cleaning agent is stored as the chemical A inside the chemical tank 22a. The supply position of the chemical A is not particularly limited, and preferably, the chemical A is supplied to the wire shower water of the wire part 55 from the chemical tank 22a.

  Further, a papermaking chemical containing a felt conditioner is stored as the internal chemical B in the internal chemical tank 22b. The supply position of the internal additive B is not particularly limited. Preferably, the internal additive B is supplied to the felt shower water of the press part 56 from the internal additive tank 22b.

  The wire cleaning agent and the felt conditioner are commercially available, for example, under the product name “Press Shot” (Kurita Kogyo Co., Ltd.). The wire cleaning agent and the felt conditioner may be used alone or in combination of two or more. Further, the addition of the wire cleaning agent and the felt conditioner may be performed continuously, may be performed once, or may be performed a plurality of times.

  The amounts of the wire cleaning agent and the felt conditioner are not particularly limited. The lower limit of the addition amount is preferably 0.1 mg / L or more, and more preferably 1 mg / L or more with respect to the amount of shower water. Further, the upper limit of the amount of addition is preferably 10,000 mg / L or less, and more preferably 2,000 mg / L or less, based on the amount of shower water.

  The type of the paper-making agent different from the wire cleaning agent and the felt conditioner is not particularly limited. Other papermaking agents include, for example, surfactants, waxes, sizing agents, fillers, rust inhibitors, conductive agents, defoamers, dispersants, viscosity modifiers, flocculants, coagulants, paper strength agents, Examples include a retention improver, a paper powder drop-preventing agent, a bulking agent, and a slime control agent.

<Method of estimating the amount of accumulated soil on wires and / or felt in the papermaking process>
Hereinafter, the dirt accumulation amount estimation method according to the present invention will be described. The method comprises: (A) measuring the amounts of calcium carbonate and pitch contained in the white water used in the papermaking process; and (B) measuring the amounts of calcium carbonate and pitch from the wire and / or wire in the wire part 55. Calculating the amount of accumulated dirt adhering to the felt in the press part 56.

[(A) Measurement of amount of calcium carbonate and pitch]
FIG. 2 is a schematic diagram showing an outline of the chemical injection system 20 incorporated in the paper making process 10 shown in FIG. In the present embodiment, the amounts of calcium carbonate and pitch contained in the white water used in the papermaking process are measured using the turbidity measurement unit 30. The amounts of calcium carbonate and pitch are measured by measuring "turbidity at rest" described later.

  The turbidity measurement unit 30 is configured to collect white water from the conduit 59 by a predetermined procedure, store the collected white water in the measurement container 31, and measure the turbidity. Specifically, the turbidity measurement unit 30 includes a supply system 37 having a sampling pump 33 for pumping white water flowing through the conduit 59 and supplying the white water to the measurement container 31, and a white water having a capacity equal to or larger than the measurement container 31. A circulation system 38 which flows out from the outlet 31 and returns to the conduit 59. The supply system 37 and the circulation system 38 are provided with a supply valve 34 and a circulation valve 35 that are selectively opened and closed by the arithmetic processing unit 21, respectively. By performing the open / close control of the circulation valve 35 and the operation control of the sampling pump 33, the white water flowing through the conduit 59 can be collected in the measurement container 31.

  If the sampling pump 33 is of a positive displacement type, the supply valve 34 is unnecessary, and if the measuring container 31 is of an open type and has a structure in which the collected liquid overflows, the circulation valve 35 is also unnecessary. . Although white water is collected from the conduit 59 here, white water may be collected directly from the white water pit 57.

  The number of turbidity measurement units is preferably one as in the present embodiment in terms of simplification of the system configuration, but may be plural. When a plurality of turbidity measurement units are employed, the turbidity during stirring and the turbidity at rest are measured in separate containers, so that both turbidities can be measured in parallel without waiting for the time until rest. Can be measured.

  The measuring vessel 31 has a depth of, for example, about 0.3 to 1.5 m and a capacity of storing about 20 to 1000 L, preferably about 30 to 50 L, of white water, and a drain valve that forms a drain system at the bottom thereof. 36. A turbidity sensor 32 that measures the turbidity of the white water stored in the measurement container 31 is provided at an upper portion of the inner wall surface of the measurement container 31, for example, at a position 50 to 200 mm below the water surface. As the turbidity sensor 32, for example, an absorbance sensor, a reflected light sensor, a transmitted light sensor, or the like can be used. Further, a water level sensor (not shown) for detecting that the water level of the white water has reached the water full position may be provided at the water full position on the inner wall surface of the measurement container 31.

  In the vicinity of the turbidity sensor 32, a cleaning mechanism 39 including a water jet nozzle, a wiper (not shown), and the like for cleaning the periphery of the turbidity sensor 32 and its sensor surface is provided. The washing mechanism 39 measures the turbidity of the white water collected in the measurement container 31 by the turbidity sensor 32, and then selectively operates after the drain valve 36 is opened to drain the white water, and the turbidity sensor 32 It plays the role of cleaning the sensor surface and its surroundings and keeping the inside of the measurement container 31 clean.

  Here, the supply speed of the supply system 37 (and the discharge speed of the circulation system 38) [L / sec] and the capacity [L] of the measurement container 31 are determined by the flow of the white water flowing into the measurement container 31 from the supply system 37. Is set to be sufficiently stirred.

[(B) Calculation of dirt accumulation amount]
Subsequently, in the present method, the amount of accumulated dirt attached to the wire in the wire part 55 and / or the felt in the press part 56 is calculated from the measurement results of the amounts of calcium carbonate and pitch.

  This method efficiently and reliably quantifies the amount of dirt accumulated on wires and felt by measuring fine components such as calcium carbonate and pitch in the white water circulation system, and optimizes wire cleaners and felt conditioners. By carrying out, it is possible to suppress wire and felt contamination failures. In addition, by optimizing the wire cleaning agent and felt conditioner that are usually added in a fixed amount, it is possible to reduce and optimize the amount of wire cleaning agent and felt conditioner used compared to the case where optimization is not performed. .

  The principle is that from the amount of dirt such as calcium carbonate and pitch concentrated in the white water circulation system, the amount of dirt transferred to paper and the amount of dirt transferred from paper to wire and felt can be calculated based on the water balance. The amount of wire and felt conditioner to be added can be optimized with respect to the calculated amount of wire and felt soiling.

  As described above, the arithmetic processing unit 21 obtains the injection amounts of the chemicals A and B based on the turbidity of the white water which is collected in the measurement container 31 and measured by the turbidity sensor 32. Then, the arithmetic processing unit 21 optimizes and controls the injection amount of the medicine A in the medicine tank 22a and the injection amount of the medicine B in the medicine tank 22b.

FIG. 3 is a schematic diagram for explaining the above water balance. Assuming that the water content at the inlet of the wire part 55 is 100, gravity dehydration is performed by the wire, and the water content at the inlet of the press part 56 becomes 80. Further, the amount of water contained in the wet paper web is 50 when the felt is squeezed in the pressing step. That is, when the amount of calcium carbonate pitch in the white water is measured, the amount of calcium carbonate pitch adhering to the wire and felt is estimated by the following equations (1) and (2).
[Equation (1)]
(Calcium carbonate pitch in white water) x (80/20) = amount of dirt adhering to wire due to calcium carbonate pitch [Equation (2)]
(Calcium carbonate pitch in white water) x (80/20) x (30/80) = amount of dirt on felt due to calcium carbonate pitch

  The amount of dirt deposited on the wire can be calculated by accumulating the amount of dirt deposited on the wire every day, and the amount of dirt deposited on the felt can be calculated by accumulating the amount of dirt deposited on the felt every day. The amount (felt stain index) can be calculated.

  The technical significance of the present invention is that the “dirt accumulation amount” adhering to the wire and / or felt is calculated, not the “dirt amount” adhering to the wire and / or felt. By accumulating the amount of soiling on a daily basis and calculating the "accumulated amount of soiling", the correlation with the felt vacuum pressure is increased, and the amount of cleaning agent used can be reduced.

  The amount of insoluble suspension contained in the white water used in the papermaking process was measured, and the amount of dirt accumulation was measured using both the measurement results of the amounts of calcium carbonate and pitch and the measurement results of the amount of insoluble suspension. Is more preferably calculated. Depending on the type of paper machine, the case where calcium carbonate and pitch are the main cause of soiling is different from the case where both calcium carbonate and pitch and the insoluble suspension (SS) are the main cause of soiling. Therefore, by calculating the “soil accumulation amount” using both the measurement results of the amounts of calcium carbonate and pitch and the measurement results of the amount of the insoluble suspension, the correlation with the felt vacuum pressure is further increased. In addition, the use amount of the cleaning agent can be further reduced.

The amount of the insoluble suspension is measured by measuring the “turbidity during stirring” described later, and the amount of the insoluble suspension adhering to the wire and felt is estimated by the following equations (3) and (4). .
[Equation (3)]
(Amount of insoluble suspension in white water) × (80/20) = Amount of dirt on wire due to insoluble suspension [Equation (4)]
(Amount of insoluble suspension in white water) × (80/20) × (30/80) = Amount of soil attached to felt by insoluble suspension

[Flowchart of this method]
FIG. 4 is a diagram showing a schematic processing procedure of the method according to the embodiment of the present invention.

  Initially, when the measurement container 31, the supply valve 34, the circulation valve 35, and the drain valve 36 are "measurement container 31: empty, drain valve 36: open, supply valve 34 and circulation valve 35: closed", The drain valve 36 is closed, the supply valve 34 and the circulation valve 35 are opened [Step S1], the sampling pump 33 is operated [Step S2], and the white water is pumped up from the conduit 59 via the supply system 37 and supplied to the measurement container 31. It is started from that. At the same time, when the supply of white water to the measurement container 31 is started, a timer (not shown) provided in the arithmetic processing unit 21 is started to measure the supply time.

  By supplying the white water, the storage amount of the white water in the measurement container 31 increases, and when the white water stored in the measurement container 31 reaches the full level, the white water of the capacity of the measurement container 31 or more is supplied to the conduit 59 via the circulation system 38. Leaked to In this state, the supply amount of the white water supplied to the measurement container 31 and the outflow amount of the white water flowing out of the measurement container 31 become equal, and the water surface position in the measurement container 31 is maintained at the full water position. At this time, the white water stored in the measurement container 31 is in a stirring state by supplying the white water to the measurement container 31 continuously.

  When the supply time reaches a predetermined time t1, that is, when white water is supplied over the time t1 and the white water in the measurement container 31 is full [Step S3], the turbidity sensor 32 is turned off. Then, the turbidity of white water (preferably, the absorbance of white water) is measured [Step S4].

  As described above, since the white water stored in the measurement container 31 at this time is in a stirring state by continuous supply of the white water, the measured turbidity is “turbidity during stirring” of the white water, and will be described later. Has a correlation with the insoluble suspension (SS) concentration of white water as the turbidity equivalent to the insoluble suspension (SS).

  Here, the predetermined time t1 is set in advance to a time required until the water surface position of the white water in the measurement container 31 reaches a predetermined full water level based on the volume of the measurement container 31 and the supply speed of the white water. Here, the timer is started at the same time as the start of the supply of the white water, and it is detected that the water surface position of the white water has reached the full water level when the predetermined time t1 has elapsed. However, the timer is used instead of or in combination with the timer. Then, the fact that the water surface position of the white water reaches the full water level may be detected by a water surface sensor (not shown) provided at the full water position of the measurement container 31.

  When the measurement of the “turbidity during stirring” of the white water is completed, the sampling pump 33 is stopped [Step S5], and the supply valve 34 and the circulation valve 35 are closed with the drain valve 36 closed [Step S6]. Thus, the supply of white water to the measurement container 31 and the outflow from the measurement container 31 are stopped. Then, by stopping the supply and outflow of the white water, the white water stored in the measurement container 31 is allowed to stand still.

  Simultaneously with the start of the standing of the white water stored in the measurement container 31, the white water is measured using the turbidity sensor 32 disposed at the position where the turbidity is measured above the white water stored in the measurement container 31 as described above. Continuous measurement of turbidity (preferably, absorbance of white water) is started [Step S7]. The continuous measurement of the turbidity of the white water may be performed by sampling the measurement value of the turbidity sensor 32 at a predetermined sampling frequency (for example, sampling frequency = 0.1 to 5 Hz).

  Then, when sufficient time has elapsed after the start of the measurement and the continuous measurement value of the turbidity of the white water has stabilized (for example, when the rate of change of the continuous measurement value has become a predetermined value or less), the end point is determined. [Step S8], the stable measurement value is defined as “turbidity at rest” of the white water [Step S9]. The “turbidity at rest” of the white water is the turbidity equivalent to calcium carbonate pitch.

  Here, the difference between “turbidity at the time of stirring” and “turbidity at the time of rest” will be described. When the white water is sufficiently stirred in the measurement container 31, the insoluble suspension (SS), calcium carbonate and pitch are dispersed in the white water without sedimentation. Since the particle size of the insoluble suspension (SS) is larger than the particle size of calcium carbonate and pitch, when the turbidity of white water is measured with stirring, the insoluble suspension (SS) is in proportion to the measured turbidity. Is dominant, and the effect of calcium carbonate pitch is small. Therefore, since the “turbidity during stirring” of white water has a correlation with the concentration of the insoluble suspension (SS), the concentration of the insoluble suspension (SS) of the white water measured using the turbidity sensor 32 is determined. Information.

  On the other hand, when the white water is allowed to stand, the relatively insoluble suspended matter (SS) having a relatively large particle size dispersed in the white water sediments rapidly, but calcium carbonate pitch having a relatively small particle size hardly sediments. Therefore, the “turbidity at rest” measured at this time is information for grasping the calcium carbonate / pitch concentration.

  Thereafter, the drain valve 36 is opened to drain all of the white water stored in the measuring container 31 [Step S10], and the cleaning mechanism 39 is operated to wash the sensor surface of the turbidity sensor 32 and its surroundings. By cleaning the inside of [1] [Step S11], the initial state can be returned.

  Thereafter, by repeating the above-described steps continuously in batches, control for continuously measuring “turbidity at stirring” and “turbidity at rest” of white water may be performed. That is, the chemical injection system 20 can continuously measure the “turbidity at the time of stirring” and the “turbidity at the time of rest” of the white water generated by the wire part 55 and the press part 56 in real time.

  Subsequently, the arithmetic processing unit 21 reads the turbidity of white water (at least “turbidity at rest”, preferably “turbidity at rest” and “turbidity at stirring”) which is collected in the measurement container 31 and measured by the turbidity sensor 32. ) Is calculated from the amount of dirt accumulated on the wire in the wire part 55 and / or the felt in the press part 56 in the paper making process. Then, based on the result of the calculation, the injection amount of the chemical into the wire and felt is obtained [Step S12]. In this process, the arithmetic processing unit 21 optimizes and controls the injection amount of the medicine in the medicine tank 22a and the injection amount of the medicine in the medicine tank 22b. The medicine may be of one type or a plurality of types depending on the required effect.

  Then, by controlling the chemical injection pumps 23a and 23b in accordance with the optimum injection amount, the injection amount of the medicine A into the wire part 55 and the injection amount of the medicine B into the press part 56 are adjusted. S13].

  Hereinafter, the present invention will be described more specifically with reference to examples.

<Test 1> Index at rest turbidity In order to confirm that the turbidity at rest detected by the turbidity sensor 32 is an index for grasping the concentration of calcium carbonate and pitch contained in the white water, a Stokes equation was used. Then, the particle diameter of the substance detected by the turbidity sensor 32 was estimated, and it was confirmed that the particle diameter was substantially the same as the particle diameter that would actually cause damage to the system.

Equation (5) is the Stokes equation.
[Equation (5)]

In the apparatus shown in FIG. 1, the terminal velocity _{v s} is 1/900 (m / s), the particle density of the calcium carbonate is 2.8 (kg / ^{m 3),} particle density pitch 1 (kg / m ³ ), the fluid density was 995.67 (kg / m ³ ), and the viscosity was 0.81 × 10 ⁻³ (Pa · s. The fluid was water at 30 ° C.). When each parameter is input to the Stokes equation, calcium carbonate (filler) of about 3 μm and a pitch of about 60 μm are measured, and it is confirmed that the particle diameters are substantially the same as the respective particle diameters that actually cause obstacles. Was.

<Test 2> Correlation between the concentration of calcium carbonate / pitch in white water and the concentration of calcium carbonate / pitch contained in felt squeezed water Using a turbidity measurement unit 30 based on the present embodiment, the concentration of white water is continuously measured in batches. Then, the "turbidity at rest" of the white water was measured, and at the same time, the calcium carbonate pitch concentration of the white water was measured using an analytical instrument. In addition, using the turbidity measuring unit 30, the concentration of felt squeezed water is continuously measured in batches, and the “turbidity at rest” of felt squeezed water is measured. Was measured for calcium carbonate pitch concentration.

  FIG. 5 shows a graph in which the concentration of calcium carbonate / pitch in the white water is plotted on the horizontal axis, and the concentration of calcium carbonate / pitch contained in the felt water is plotted on the vertical axis.

  From FIG. 5, it was confirmed that there was a positive correlation between the concentration of calcium carbonate / pitch contained in the white water and the concentration of calcium carbonate / pitch contained in the felt squeezed water. From this, it can be determined that it is possible to estimate the amount of calcium carbonate and pitch adhering to the felt from the concentration of calcium carbonate and pitch contained in the white water.

<Test 3> Correlation between the concentration of the insoluble suspension (SS) in the white water and the concentration of the insoluble suspension (SS) contained in the felt squeezed water The concentration of the white water was measured using the turbidity measurement unit 30 according to the present embodiment. Was continuously measured to determine the "turbidity during stirring" of the white water, and at the same time, the concentration of the insoluble suspension (SS) in the white water was measured using an analytical instrument. In addition, using the turbidity measurement unit 30, the felt squeezed water concentration is continuously measured in batches, and the “turbidity during stirring” of the felt squeezed water is measured. Was measured for insoluble suspension (SS) concentration.

  FIG. 6 shows a graph in which the concentration of the insoluble suspension (SS) in the white water is plotted on the horizontal axis and the concentration of the insoluble suspension (SS) contained in the felt squeezed water is plotted on the vertical axis.

  From FIG. 6, it was confirmed that there was a positive correlation between the concentration of the insoluble suspension (SS) contained in the white water and the concentration of the insoluble suspension (SS) contained in the felt squeezed water. From this, it can be determined that it is possible to estimate the amount of the insoluble suspension (SS) attached to the felt from the concentration of the insoluble suspension (SS) contained in the white water.

<Test 4> Relationship between Felt Vacuum Pressure and Felt Soil Index When No Felt Cleaning Agent is Used The apparatus shown in FIG. 1 was operated for 5 days. During that time, no felt cleaner was used.

  During operation, the static turbidity of white water was measured in the same manner as in Test 2, and the amount of calcium carbonate and pitch in the white water was determined from the measured value. Then, the above equation (2) was applied to the obtained value, and the amount of dirt adhering to the felt due to the calcium carbonate pitch was obtained. Then, the obtained values were accumulated for each day, and the accumulated values were used as a felt stain index.

  FIG. 7A shows a time change showing the relationship between the felt vacuum pressure and the felt stain index. In general, the vacuum pressure increases as the felt begins to contaminate.

  Felt vacuum pressure gradually increases from the end of SD, and felt stains are accumulated. Then, as the daily felt dirt index is accumulated, the value gradually increases from the beginning of the SD similarly to the felt vacuum pressure, and follows a correlated transition. FIG. 7B shows a correlation between the gradient of the felt vacuum pressure and the gradient of the felt dirt index for each operation. From these, it was confirmed that the accumulation of the felt index indicates the amount of dirt attached to the felt.

<Test 5> Relationship between Felt Vacuum Pressure and Felt Soil Index when Using Felt Cleaning Agent Except for using felt cleaning agent, the apparatus shown in FIG. It worked. The drug concentration was set to 400 mg / L with respect to the amount of felt shower water, and was continuously supplied during operation of the apparatus.

  FIG. 8 shows a time change showing the relationship between the felt vacuum pressure and the felt stain index. Unlike the case where the felt conditioner is not used, the relationship between the felt vacuum pressure and the felt vacuum index when the felt conditioner is used is smaller than the felt vacuum index when the felt vacuum index is changed. The felt soil index is an estimate of the amount of calcium carbonate and pitch soil brought into the pressing process.

  Therefore, it is considered that the change of the felt vacuum pressure below the change of the felt soil index indicates the cleaning effect by the felt cleaning agent. In the actual operation, it was confirmed that the paper breakage in the press part was reduced during the period in which the transition of the felt vacuum pressure was lower than the transition of the felt dirt index.

10 Papermaking process 30 Turbidity measurement unit 55 Wire part

Claims (2)

A step of measuring the amount of calcium carbonate and pitch contained in the white water used in the papermaking process,
Calculating the amount of dirt accumulated on the wire and / or the press part in the wire part in the paper making step from the measurement results of the amounts of the calcium carbonate and the pitch. Dirt accumulation amount estimation method. Further comprising a step of measuring the amount of insoluble suspension contained in white water used in the papermaking process,
The method according to claim 1, wherein the soil accumulation amount is calculated from a measurement result of the amount of the calcium carbonate and the pitch and a measurement result of the amount of the insoluble suspension.

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