JPS604316B2 - Method for monitoring stock behavior on paper machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention detects fluctuations in the amount of light transmitted through the stock suspension on a wire on a paper machine as an electrical signal and processes the signal to grasp the paper layer formation status. This paper concerns a method for monitoring paper stock behavior.

Most papers currently on the market are dehydrated by spraying a stock suspension in which paper stocks (usually mainly pulp fibers) are dispersed in water as uniformly as possible onto the wire from the slice entrance of the head box. It is said that the quality of the paper layer formation is determined by the wire bar, especially the front half of the wire bar near the head box. However, although the wire part region is an important region where paper layers are formed, it remains unclear how paper stock behaves in this region to form paper layers. , and there is no method for monitoring the behavior of the paper stock that is suitable for taking prompt action in the case of poor paper layer formation. The reality is that the plant was operating while speculating about the turbid conditions. In particular, as paper machines operate at higher speeds year by year, it is becoming increasingly difficult to understand the behavior of paper stocks in the area of wire parts. As a related method, a photographic strobe is used as a light source to examine the state of paper layer formation on a wire part, and an optical camera receives the light transmitted through the paper layer to print an image on film, which is then developed to produce a negative or positive image. It is known to print on film or, in some cases, on photographic paper. However, although this method provides a clear image, it is not suitable for continuously understanding paper stock behavior, and there is a time lag between image capture and image observation, so it cannot be used as a monitoring method. . Another known method is to photograph the surface condition of a paper layer using reflected light rather than transmitted light through the paper layer. However, it is difficult to know the internal stock behavior. Recently, as a method for monitoring paper webs that move at high speed, a light source is installed on one side of the paper web, etc., and a television camera is installed on the other side, and a special method is used to reproduce the green image by horizontal scanning of the television camera. A method has been proposed in which a shake-free still image is obtained and observed by applying an operation (trigger signal). However, when video is recorded using a TV camera or an image pickup tube camera, the signal range that can be detected from the key image is relatively wide in the case of continuous images, but in the case of still images, the recording and playback system Since the noise in the image pickup tube camera can no longer be ignored, an image is created only at one tone with a width of about 6% (100% ÷ 16) of the entire signal area, which corresponds to the amount of light that can be received by the image pickup tube camera, and A drawback of currently used industrial measurement television cameras is that the signal is disturbed by noise and does not appear as an accurate grayscale image in a still image. Incidentally, in the present invention, the fluctuation rate of the amount of transmitted light with respect to the average amount of transmitted light of the fluid stock that is monitored is, for example, 20% for tissue paper and 10% for newsprint.
%, at most 20%, as is ±6% for high-quality paper.

Therefore, for example, the amount of transmitted light is 60% of the amount of light that can be received by the image tube camera.
%, even if the variation rate is 20%, which is the maximum among the above, the gradation level of the average transmittance is the gradation level of the first false flea from the bottom (the 1st gradation is approximately 6%). However, since the variation in the amount of transmitted light can only be expressed within the range of ±2 gradations, that is, 4 gradations, it is not possible to create a clear image by detecting the difference in the variation in the amount of light. Therefore, with the method of using a television camera, it is not possible to sufficiently monitor the flowing paper stock depending on the still image, and there is no point in analyzing the detection signal obtained. The present inventors researched a method that could monitor the paper stock behavior in the wire part region by increasing the gradation level, and found that even if the transmitted light of the paper stock suspension on the wire part was received by a solid-state imaging camera, the plastic wire -Alternatively, the presence of the bronze wire 1 or the presence of fillers that may be added to the paper stock does not interfere with the light reception result, and even if the light source is placed below the wire 1, the light emission may be affected by water splashing. The present invention was completed by discovering that the object of the present invention can be achieved by quickly processing the electrical signals received and converted without affecting the result of light reception.

That is, the present invention projects light onto the paper stock suspension on the wire of a paper machine from below the wire, receives the transmitted light at a light receiving section above the wire, detects fluctuations in the amount of received light, and detects the paper stock suspension. To monitor the behavior, a flash of light is emitted once or intermittently several times in a short period of time using a strobe flash light source, and the amount of light transmitted through the stock suspension is received by a body imaging camera. The present invention relates to a method for monitoring stock behavior on a paper machine, which is characterized by rapidly processing a large number of electrical signals.

Hereinafter, the method for monitoring stock behavior on a paper machine according to the present invention will be explained in more detail.

FIG. 1 is an explanatory diagram of an example of a paper machine used for carrying out the present invention;
Figures 2 to 4 show data obtained by signal processing the electrical signals obtained by detecting the transmitted light of the stock suspension in the example.
FIG. 2 is a graph showing the power spectrum in Example 1, FIG. 3 is a graph showing a change in the coefficient of variation due to a change in wire frequency in Example 2, and FIG. 4 is a graph showing the light reception in Example 3. It is a probability density distribution curve of quantity fluctuation. A paper making process using a foil fourdrinier paper machine shown as an example of a paper machine in FIG. 1 will be briefly explained.

The stock 1 is sent in suspension to the headbox 2 from below and is ejected from the slicing opening 3 onto the wire 4. The wire 14 is endless and moves horizontally through the breast roll 5 installed directly below the slice entrance 3, reaches the couch roll 6, changes direction downward, and passes through the negative pressure of the suction pick-up roll 7 of the presto part. After touching , it changes direction and returns to the prestrol 5 again. The suspension of paper stock 1 spouted from the slice entrance 3 falls onto the wire 4 and is dehydrated to a considerable extent, but the dehydration of the paper stock 1 is delayed by the forming board 8 under the wire 4, causing the suspension to drop onto the wire 4. The ratio is equalized. In this case, the position of the landing point where the suspension of the stock 1 falls onto the wire 4, the outflow velocity Vi of the suspension of the stock 1, and the moving speed Vw of the wire 4.
The ratio Vi/Vw and the shaking conditions of the wire 4 (transverse frequency, amplitude) influence the quality of the paper layer formation state. Suspension of stock 1 on wire-4
After passing the forming port 8 and taking a shower from the water shower device 9 as necessary, while moving, a plurality of hydro oils 10 installed in contact with the back side of the wire 4 (by the paper machine The water is further dehydrated by using a tape roll. Further progressing, water and air are strongly suctioned by the vacuum of a plurality of suction poxes 11 (usually 20 to 30 Hg columns) installed in contact with the back surface of the wire 14, and the solid content is reduced to 10 to 2.
The web becomes a 0% wet web, and if necessary, a dandy roll 12 may be used to improve the texture or a watermark may be added. The wet web thus formed on the wire part is separated from the wire 4 by the suction pick-up roll 7 of the press part and moves to the press part and further to the dryer part.
As mentioned above, paper waste is formed throughout the wire part, but the behavior of the paper stock up to the draining line of the wire part, which is suspended in water, has an important influence on the quality of the paper layer formation. affect The wire up to the draining line usually includes the first half of the wire part or most of the end of the table roll group. A monitoring method according to the present invention for monitoring paper stock behavior in areas important for paper layer formation is carried out as follows. First, the light source 13 is installed at a suitable position and illuminates the stock suspension on the wire 4 from below the wire 4.

The installation position of the light source 13 does not necessarily have to be directly under the wire-4, but the light from the light source 13 at another installation position is reflected or refracted using a mirror or lens, and the light source 13 is installed from below the wire-4. It is also possible to project light onto the suspension. For the sake of convenience, the present invention will be described below with reference to the case where light is directly emitted from the light source 13 as shown in FIG. This also includes cases in which light is projected by A commonly used strobe flash device can be used as the strobe flash light source used as the light source 13 in the present invention. Light is projected onto the target. A flash of light emitted from the light source 13 and transmitted through the stock suspension is received by a light receiving section 14 installed above the wire 4 facing the light source 13.

In the present invention, a solid-state imaging camera is used for the light receiving section 14. A solid-state imaging camera is equipped with a light-receiving lens section for receiving light inside the camera, as well as a large number of light-receiving elements (the current maximum is 2048) such as CCD (
A charge coupled device), a PDA (photo diode array), etc. are provided in a planar manner. The transmitted light that has passed through a certain area of the stock suspension that is being monitored passes through the light-receiving lens section, forms an image, and reaches the light-receiving element surface. A corresponding electric density is generated. In other words, each light-receiving element detects the transmission of the paper stock suspension in a small area corresponding to the image formation area on each light-receiving element within the area of the paper stock suspension through which the light received by the solid-state imaging camera has passed. Electric density occurs depending on the intensity of light. In this way, each electrical density generated by a large number of light-receiving elements is stored for a short period of time, then scanned and extracted as an electrical signal, which is immediately processed, but is stored in another storage device as necessary. The collected data is a predetermined amount of data (signal processing is performed immediately after collection). The above steps are repeated each time a flash is emitted or received.

・If you use this kind of body imaging camera, by emitting and receiving a single flash of light, each of the transmitted light of the paper stock suspension to be monitored can be measured for each transmission of the same number of small areas as the number of light receiving elements. Separately, each light receiving element of the solid-state imaging camera receives the light simultaneously, and it is possible to detect the intensity unevenness of the transmitted light between each micro area.

Therefore, even by emitting and receiving a single flash of light, it is possible to detect irregularities in the intensity of light transmitted through the paper stock suspension between minute areas, and monitoring is therefore possible. However, by emitting and receiving multiple flashes of light, By moving the location of the paper stock suspension through which the light passes, the number of small areas, ie, the number of measurement points, can be increased to further improve monitoring accuracy. In addition, the noise of the garden image camera is 4, and the S/N ratio is 1 or more (noise width is 0.1% or less).
It is suitable for the present invention, which requires detection of even weak transmitted light. As described above, the solid-state imaging camera detects the intensity of the light transmitted through the paper stock suspension between many small areas by emitting and receiving a single flash of light, and converts it into an electrical signal.

The detection area is small enough to sufficiently detect local non-uniformity in the dispersion state of the paper stock suspension, and varies depending on the type of paper to be monitored and its use, but there are many preferred detection areas. In this case, it is in the range of 0.2 ribs 2 to 7 sides 2. The appropriate flash duration for one flash varies depending on the speed per second, and the product of the distance and the flash duration is 1. Just adjust it so that it is below the ship's side. If the flash duration is longer than the above range, resolution will be poor. Although there is no lower limit for the flash duration, in practice there are insufficient light quantities and problems with the equipment, so the product of the distance and the flash duration is usually 0.05 or more. When emitting a flash of light multiple times, it is preferable that the light emission cycle is determined so that the same part of the stock suspension will not be converted into an electrical signal redundantly due to two subsequent light emitting and light receptions. . For example, if you use a Sonobody imaging camera in which 31 light-receiving elements are arranged vertically (in the flow direction of the paper stock suspension when receiving light), each light-receiving element has a detection area of 7 legs (2.65 ribs x 2). ．．
When monitoring a stock suspension at a speed of 100/min with a light emitting period of 5 hsec, what is the distance that the stock suspension flows during that time and the length of the entire surface of the permeation in the flow direction? Almost the same. Therefore, by setting the emission period to 5 hsec or more, it is possible to avoid redundant photoelectric conversion at the same location in the stock suspension.

In addition, when emitting and receiving light multiple times, the time from the start to the end of the emitting/receiving operation (hereinafter sometimes referred to as light reception time) is a time period in which the partially non-uniform state of paper stock dispersion is diluted. It is not preferable to use too long a time so as not to be unable to grip the paper due to non-uniformity, and although it varies depending on the machine speed, the time is preferably within 1 piece, preferably within 5 minutes. As the light receiving section 14, a solid-state imaging camera is installed directly at that position as described above, or only a light receiving lens section is installed at the position of the light receiving section 14 and the received light is transmitted to a solid-state imaging camera installed at another location. It can also be guided to the main body using optical fibers.

In addition, since a single group bran image camera can detect the dispersion state of the stock suspension at many locations, one set of light source I3 and light receiving section 14 can be positioned at a specific position in the width direction on the wire. Although it is sufficient to monitor the behavior of the paper stock on the wire by fixing only the wire and detecting the transmitted light, emitting and receiving light at multiple positions in the width direction on the wire makes it difficult to detect the paper stock suspension. This is preferable because the amount of information is increased over the entire flow width, and unevenness in the width direction can be known, further enhancing the monitoring effect. Furthermore, when light is projected and received at a plurality of positions in the flow direction of the stock suspension, it is possible to know the normal and abnormal behavior of the paper stock during the process of forming paper layers. It is preferable to separately provide the light source 13 and the light receiving section 14 at a plurality of positions in the width direction and the flow direction.
The light source 13 and the light receiving section 14 in a set or a small number of sets may be moved in the width direction or the flow direction. In the present invention, monitoring is performed to judge the quality of the paper layer formation state, so the behavior of the paper stock in the paper stock suspension, which has an important influence on the quality of the paper layer formation, is to be monitored. As shown in the above location, as described above, the monitoring range is up to the drainage line that includes most of the ends of the 10 groups of foils or the group of table rolls.

Figure 1 shows two examples of the position of a straight line when a pair of light sources and light receiving unit 14 are positioned on a straight line perpendicular to the wire 4 and monitored within the area of 10 groups of hydrofoils. -A and straight line B-B. In this way, the electrical signal obtained by photoelectric conversion by detecting the intensity fluctuations of the transmitted light transmitted through the paper stock suspension by one flash or multiple flashes in a short period of time can be converted into electrical signals for each light reception as necessary. After this data is once stored in a storage device, it is immediately subjected to signal processing to obtain characteristic values or graphs based on statistical methods, and the quality of the paper layer formation state is determined.

As such characteristic values or graphs, coefficient of variation, frequency analysis (power spectrum analysis), probability density distribution, interval time distribution, etc. are used. It is not necessary to implement all of these items, and it is good to implement one or more items as necessary. Among the above-mentioned items, frequency analysis is a particularly preferred method because it does not require empirically setting criteria for determination, and it is possible to immediately determine the quality of the paper layer formation even for suspensions of paper stocks with which there is no experience.

To immediately process the electrical signals obtained by photoelectric conversion using a solid-state imaging camera in order to obtain such characteristic values or graphs, a commercially available ready-made signal processing device can be used, an example of which will be described later. This will be shown in examples. Thus the wire
By monitoring the behavior of the paper stock above, if it is determined that the state of paper layer formation is poor, the following measures can be taken as appropriate depending on the situation.

The ratio Vi/Vw between the outflow velocity Vj of the suspension of the paper stock 1 jetted out from the slice opening 3 of the head box 2 and the moving velocity Vw of the wire 4 is changed.

0} Change the shaking conditions of wire-4. Shiichi
Changes in the method of using dewatering equipment such as Hydrofoil 10 or Teflon Roll (for example, strengthening turbulence in the front stage of the wire part where there is a lot of water). Mortar: Water shower provided in front of wire bart.

■ Smoothing of wet web using Dandy Roll 12. N Various measures taken before the head box to improve the stock suspension state of the stock 1 ejected onto the wire 4, i.e. ta - Increase or decrease in the stock concentration in the stock suspension; [b] Paper stock Increase or decrease in the flow rate of the suspension in the head box, {c- increase or decrease in the amount of chemical solution (mainly surfactant) added to the paper stock suspension, 'd} fiber length in the paper stock suspension Adjustment of,【
e-Increase/decrease the relative friction surface inside the head box, etc.

The method for monitoring the behavior of paper stock on a paper machine according to the present invention is a method that can sufficiently judge the quality of the paper layer formation state of the wire part, and it is also possible to quickly make a quality judgment and take measures using the monitor, so it is suitable for the paper manufacturing industry. There is a lot of profit to be made.

Example 1 A fourdrinier paper machine (using 60 mesh plastic wire) with a wire part of 118 mm was used, and a hardwood pulp stock suspension with a furnace water level of 35 ratio C and a pulp concentration of 0.7% was used. A paper stock suspension was spread onto the wire at a flow rate of 100 per minute, and a high-quality paper with a basis weight of 53 kg was produced at a flow rate of 400 per minute, which was monitored as follows. .

That is, a strobe flash device is used as the light source 13, and a solid-state imaging camera (manufactured by RETICON, L
CIO stop elements (1024, PDA) were installed at positions 50 arcs below the wire and 100 arcs above the wire on the straight line A-A in Figure 1, and the strobe flash device was fired 50 times (flash time 30 rsec). , luminescence cycle 5 skin se
c) While detecting the intensity of light transmitted through approximately 50,000 points of paper stock suspension (light transmission detection area is 0.4 mm2 per point),
The obtained electric signal is processed by a signal processing device (Sanei Juku9ki KK,
After storing it in the signal processor type 07A),
When the power spectrum was analyzed using the same device, the curve shown in Figure 2A was obtained. From this curve, it was recognized that the amount of variation in the amount of transmitted light was large and the dispersion of the stock was poor, so the flow rate in the headbox was increased to 120 kites/min and then to 200 kites/min, respectively. The dispersion improves as the curve C increases, and in particular curve C shows that the variation in light intensity is low and stable, indicating that the dispersion state is uniform and the paper layer formation state is very good. Example 2 A fourdrinier paper machine with 16 wire parts (using 60 mesh plastic wire) was used with a hardwood pulp stock suspension having a furnace water density ratio of c and a valve concentration of 0.8%, at a speed of 150 per second. The dispersion state of the paper stock was examined as follows while producing high-quality paper with a basis weight of 8M by changing the number of wire shaking per minute.

That is, the same strobe flash device and solid-state imaging camera as in Example 1 were placed at a distance of 3 skins from the slice entrance 3 in FIG. The strobe flash device was installed and fired 30 times (flash time 100 seconds, light emission cycle 10 seconds) to transmit light through the paper stock suspension from approximately 3 points (0.3 cells per point of light transmission detection area). The electrical signals obtained while detecting the strength of 2) were stored in the same signal processing device as in Example 1, and the signals were processed to show the paper stock dispersibility with respect to shaking per minute as shown in Fig. 3. The coefficient of variation curve was obtained. As is clear from Figure 3, as the number of shakers increases, the dispersion improves, and therefore, when the monitor determines that the dispersion state is poor, it is possible to improve the dispersion state by increasing the number of shakes. I understand. Example 3 A hardwood pulp stock suspension with a furnace water temperature of 32 ratio C and a pulp concentration of 0.9% was subjected to a 2% loss on a paper machine with a wire part of 25 mesh (using 60 mesh bronze wire). The following was monitored while adding and mixing and producing high-quality paper with a basis weight of 64 m/min at a papermaking speed of 700/min.

That is, the same strobe flash device and solid-state imaging camera as in Example 1 were installed at a distance just before the draining line on the wire, and the strobe flash device was made to emit light 100 times (flash time 10 seconds, light emission period 2 h seconds). About 100
After storing the electrical signals obtained while detecting the strength of the light transmitted through the paper stock suspension at 10,000 points (the light transmission detection area is 0.2 side 2 per point) in the same signal processing device as in Example 1. The probability density distribution of fluctuations in the amount of received light was investigated by signal processing. That is, the distribution curve obtained by taking the percentage of the average transmittance as the light amount fluctuation level as the axis and the frequency of each light amount level as the vertical axis is shown by A in FIG. It was observed that the distribution curve A was relatively wide and distributed over a wide range of light quantity variation levels, indicating that the paper stock dispersion state was not good. Therefore, when we added 0.3% sodium polyacrylate (surfactant) based on the amount of pulp to the stock inlet stock suspension, the distribution curve as shown in Figure 4 was obtained, and the paper stock dispersion state improved. It turned out that it was done.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an example of a paper machine used for carrying out the present invention;
Figures 2 to 4 show data obtained by signal processing the electrical signals obtained by detecting the transmitted light of the stock suspension in the example.
FIG. 2 is a graph showing the power spectrum in Example 1, FIG. 3 is a graph showing changes in wire frequency in Example 2, and FIG. 4 is a probability density of fluctuations in the amount of received light in Example 3. It is a distribution curve. 1: Paper stock, 2: Head box, 3: Slice Sekiguchi part,
4: Wire 1, 5: Prestrol, 6: Couch roll, 7: Suction pick-up roll, 8: Forming board, 9: Water shower device, 10: Hydrofoil, 11: Suction pox, 12: Dandy roll,
13: light source, 14: light receiving section. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1 Light is projected onto the stock suspension on the wire of a paper machine from below the wire, and the transmitted light is detected by a light receiving section above the wire to detect fluctuations in the amount of received light to monitor paper stock behavior. In doing so,
A strobe flash light source emits a flash of light once or intermittently several times in a short period of time, and a solid-state imaging camera receives the amount of transmitted light that has passed through the paper stock suspension.The resulting large number of electrical signals are then quickly captured. A method for monitoring paper stock behavior on a paper machine, characterized by signal processing. 2. Monitoring of paper stock behavior on a paper machine according to claim 1, wherein a large number of electrical signals obtained by receiving light are once stored in a storage device each time light is received, and then the signals are promptly processed all at once. Law. 3. A method for monitoring paper stock behavior on a paper machine according to claim 1 or 2, which uses a solid-state imaging camera having a CCD (charge couplet device) as a light receiving element. 4 As a solid-state imaging camera, a PDA (photo sensor) is used as a light receiving element.
A method for monitoring stock behavior on a paper machine according to claim 1 or 2, using a diode array). 5 The product of the machine speed and the flash time for one flash is 1.0 m.
A method for monitoring paper stock behavior on a paper machine according to any one of claims 1 to 4, which adjusts the behavior of stock to be less than or equal to m.