JPS604315B2 - How to monitor stock behavior on a paper machine - Google Patents

Description

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

Most papers currently on the market are dehydrated by spraying a stock suspension, which is made by dispersing paper stock (usually mainly pulp fibers) in water as evenly as possible, onto a wire from the slice entrance of the head box. It is said that the quality of the paper layer is determined by the wire part, especially the front half of the paper layer 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. In addition, there is no way to monitor the behavior of the paper stock in order to take prompt action in the case of poor paper layer formation, and to observe the true state of ripples on the surface of the first half of the wire part, it is possible to monitor the behavior of the paper stock. 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, the behavior of paper stocks in the area of wire parts is becoming increasingly difficult to understand. Conventionally, the method of investigating the state of paper layer formation on a wire part is to use a photographic strobe as a light source, receive the transmitted light of the paper layer with an optical camera, and print an image onto film, which is then processed to create a negative or positive film. In some cases, methods of printing on photographic paper are known. 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 photographing and image observation, so it cannot be used as a monitoring method. . Also,
A method is also known in which the surface condition of the paper layer is photographed using reflected light rather than transmitted light from the paper layer, but this method
Although it is possible to examine surface conditions such as ripples and jumping of the stock suspension above, it is difficult to know the internal behavior of the stock. Recently, as a method for monitoring paper webs that move at high speed, a light source is placed on one side of the paper web, a television camera is installed on the other side, and a special operation ( A method has been proposed in which a shake-free still image is obtained and observed by adding a trigger signal. However, when a video camera is used to capture a video image, the signal range that can be detected from the image is relatively wide in the case of a moving image, but in the case of a still image, recording and
The noise of the reproduction system can no longer be ignored, and the amount of light that can be received by the image pickup tube camera is approximately 6% (
The currently used method is that an image is created only in one gradation with a width of 100% ÷ 16), and the signal within each gradation is disturbed by noise and does not appear as an accurate gradation image in a still image. This is a drawback of industrial measurement television cameras. 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 paper stock that is the subject of monitoring is at most ±20% for tissue paper, 10% for newsprint, and 6% for high-quality paper. It is 20%. Therefore, for example, if the amount of transmitted light is 60% of the amount of light that can be received by the image pickup tube camera,
Even if the variation rate is 20%, which is the maximum among the above, the gradation level of the average transmitted amount is the first gradation level from the bottom (1, the gradation is approximately 6%), and the amount of transmitted light is Since the fluctuations can only be expressed in the range of two tones, or four tones, it is not possible to create a clear image by detecting the difference in light intensity fluctuations. 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 was received by a photoelectric converter, 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 inventors completed the present invention by discovering that the object 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 behavior, light is emitted from a stable DC lighting light source or strobe flash light source, and the amount of transmitted light transmitted through the stock suspension is received over time by a photoelectric converter and promptly processed as a signal. The present invention provides a method for monitoring paper stock behavior on a paper machine, which is characterized by:

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;
FIG. 2 to FIG. 5 are diagrams showing data obtained by signal processing the electrical signals obtained by detecting the transmitted light of the stock suspension in Examples, and FIG. Figures 3 and 4 are graphs showing changes in the coefficient of variation due to changes in the light transmission position and wire frequency in Example 2, respectively, and Figure 5 is the probability density of fluctuations in the amount of received light in Example 3. It is a distribution curve. A paper making process using a foil final paper machine shown as an example of a paper machine in FIG. 1 will be briefly explained.

Stock 1, head box 2 from below in a suspension state
and is ejected from the slice opening 3 onto the wire 4. The wire 4 is endless and moves horizontally through a pre-stroll 5 placed just below the slice entrance 3, reaches a couch roll 6, changes its direction downward, and passes through the negative side of the suction pickup roll 7 of the press part. After coming into contact with the pressure, it further changes direction and returns to the press roll 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 below 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 paper stock 1 falls onto the wire-4, the outflow velocity Vi of the suspension of paper stock 1, and the moving speed Vw of the wire-4
The ratio Vi/Vw and the shaking condition of wire 4 (
The frequency and amplitude of vibrations in the lateral direction affect the quality of the paper layer formation. The suspension of the stock 1 on the wire 4 rides on the wire 4, passes the forming board 8, receives a shower from the water shower device 9 as necessary, and then passes through the back surface of the wire 14 while moving. The paper is further dehydrated by a plurality of hydro-oils 10 (some paper machines use table rolls) placed in contact with the paper. Further progressing, water and air are strongly suctioned by the vacuum of multiple suction boxes 11 (usually 20 to 30 Hg columns) installed in contact with the back side of the wire 4, reducing the solid content to 10 to 20%.
It becomes a wet web, and if necessary, the texture may be improved by Dandy Rozell 12 or watermarks may be added. The wet web thus formed in the wire part is peeled off from the wire 4 by the suction pick-up roll 7 of the press part and transferred to the press part and further to the dryer part. As mentioned above, a paper layer is formed over the entire area of 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 stock formation. Astonish.

The portion up to the draining line usually includes the first half of the wire part, that is, most of the end of the 10 foil groups or the tapered roll group. The monitoring method according to the present invention for monitoring the behavior of paper stock in areas important for paper layer formation is carried out as follows. First, light source 13
Place the wire at an appropriate position and insert the wire from below wire-4.
Light is projected onto the stock suspension of step 4.

The installation position of the light source 13 does not necessarily need 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 is applied to the paper from below the wire 4. It is also possible to project light onto the material 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 In the present invention, a stable DC lighting light source is preferable as the light source 13, and a laser beam light source is especially preferable.

In addition, a stropflash light source can also be used. The 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 photoelectric converter is used for the light receiving section 14. By using a photoelectric converter, it is possible to detect a wide range of light from weak light to strong light and obtain analog electrical signals continuously or intermittently according to the continuous or intermittent transmitted light, and the noise is so small that it does not cause any problem at all. Since an N ratio of 1 pi or more (noise width of 0.1% or less) can be ensured, it is very suitable for the present invention, which requires detection of weak light in transmitted light. Photomultiplier tubes, phototubes, photodiodes, photoexposure cells (PbSe cells, lnSb cells, lnmatsu cells, etc.) are used as photoelectric converters, but photomultipliers A tube is most preferably used because it is highly sensitive and can detect even extremely weak light. As the light receiving section 14, a photoelectric converter and a light receiving lens system as described above are installed directly at that position, or only a light receiving device such as a light receiving lens system is installed at the position of the light receiving section 14 and the received light is transmitted to another location. It is also possible to guide the optical fiber to the main body of the installed photoelectric converter. A photoelectric converter converts the strength of the received light into an electrical signal.

Therefore, the detection area of the paper stock suspension through which the transmitted light received by the light receiving section 14 is small enough to detect partial non-uniformity of the paper stock dispersion state as a change in the electrical signal. The minuteness of this detection area varies depending on the type of paper to be monitored, its purpose, etc., but the preferred detection area is in the range of 0.2 squares to 7 sides in most cases. The light received by the light receiving section 14 at a certain position is the light that has passed through the paper stock suspension flowing on the wire at the certain position, and if the light source is a DC lighting light source, the transmitted light will flow through the projecting light beam. The converted electric signal is a continuous transmitted light of the stock suspension moving in the direction, and the converted electrical signal is a continuous analog signal, but the signal processed is time-divided and divided into parts that are considered to be instantaneous. It is a group of discrete signals captured by Furthermore, if the light source is a strobe flash light source, the transmitted light is transmitted light that is transmitted for a time that can be regarded as instantaneous at multiple positions in the flow direction of the stock suspension, and the converted electrical signal is an intermittent signal. be. As mentioned above, the time-divided time in the case of continuous transmitted light or the transmission time in the case of intermittent transmitted light is the time required to detect spots, so it is preferable to use a time that can be regarded as instantaneous. The product of the instantaneous penetration time and the instantaneous penetration time is 0.05 to 1.
Just adjust it so that it becomes 0 ribs. The light reception time (the time from the start of receiving continuous or intermittent transmitted light until the end of the light reception operation) is the time when the partially non-uniform state of paper stock dispersion is diluted or averaged and cannot be grasped as non-uniform. Although it varies depending on the speed of the stock suspension per second, the light reception time is within 1 minute, preferably in the range of 1 minute to 5 minutes. Incidentally, even if one set of light source 13 and light receiving section 14 is fixed only at a specific position in the width direction on the wire and the transmitted light is detected, it is still possible to monitor the behavior of the paper stock on the wire. However, projecting and receiving light at multiple positions in the width direction on the wire increases the amount of information over the entire flow of the paper stock suspension, and makes it possible to see irregularities in the width direction, further improving the monitoring effect. It is preferable because it increases

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. Although it is preferable to provide separate sets of light sources 13 and light receiving sections 14 at such multiple positions in the width direction or flow direction, one set or a small number of sets of light sources 13 and light receiving sections 14 are provided in the width direction or flow direction. You can also move it to In the present invention, since monitoring is performed to judge the quality of the paper layer formation state, the behavior of the paper stock in the stock suspension, which has an important influence on the quality, is to be monitored. ↓ As indicated by the location on the part, the monitoring range is the drainage line that includes most of the end of the foil 10 sheep or tape roll group as described above.

FIG. 1 shows two positions of a straight line when a pair of light sources 13 and light receiving parts 14 are positioned on a straight line perpendicular to the wire 4 and monitored within the area of 10 hydrooils.
Examples are shown by lines AA and BB. In this way, the electrical signal obtained by photoelectrically converting the intensity fluctuations of the transmitted light that has passed through the paper stock suspension for a short period of time is stored in a storage device as necessary, and then promptly processed. The quality of the paper layer formation is determined by obtaining characteristic values or graphs using statistical methods.

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 signal-process the electrical signals obtained by photoelectric conversion 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 in the example. show. In this way, when the behavior of the paper stock on the wire is monitored and it is determined that the state of the paper layer formation is poor, the following treatments can be taken as appropriate depending on the situation.

The ratio Vi/Vw of the outflow speed Vi of the suspension of the stock 1 jetted out from the slice entrance 3 of the head box 2 and the moving speed Vw of the wire 4 is changed.

{01 Change of shaking conditions for wire-4. Shiichi
Change in the method of using a dewatering device such as Hydro Oil 10 or a teflon roll (for example, strengthening turbulence in the front stage of a wire part with a lot of water). A water shower is carried out in front of the mortar wire part.

'Mura: Smoothing wet web using Dandy Roll 12. M Various measures taken before the headbox to improve the stock suspension state of the stock 1 ejected onto the wire-4, i.e. {a} Increase or decrease of the stock concentration in the stock suspension, other paper stock concerns. c) 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 stock suspension, 'd - Change in the fiber length in the stock suspension. adjustment, {e
- Increase or 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. This is where you can make a profit.

Example 1 A fourdrinier paper machine with a 20-mesh wire part (using one 60-mesh plastic wire) was heated to a furnace water level of 43 C.
Using a stock suspension of hardwood pulp with a pulp concentration of 0.6%, the stock suspension was jetted onto the wire at a flow rate of 130/min in the headbox, and the basis weight was 60 at a paper milling distance of 450/min. While producing high-quality paper in the evening, it was monitored as follows.

That is, as the light source 13, a He-Ne laser light source (NEO-IM type manufactured by Nihon Kagaku Engineering KK, one wavelength 63
28A, output 0.5hW), and a lens system and a photomultiplier tube (Model 931A manufactured by Hamamatsu Television KK) as the light receiving section 14, respectively, are connected to the lower part of the wire 30 on the straight line A-A in FIG. A signal processing device is installed at each of the 30 skin positions above the wire, and time-divides the 2-minute electrical signal of the paper stock transmitted light (light transmission detection area 3 ribs 2) obtained by the photomultiplier tube every 100 fsec. When the power spectrum was analyzed using a Sanei Saiki KK Signal Processor Model 07A, the curve A in the semi-logarithmic graph of Figure 2 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 adjusted to 250.
M/min and further increased to 360/min to obtain curves 2 and 3, respectively. Further, the dispersion is better as shown in curve C, 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 a 15-thick wire part (using 70 mesh plastic wire) was heated to a furnace water level of 35 C.
Using a hardwood pulp stock suspension with a pulp concentration of 0.7%,
While sanding high-quality paper with a basis weight of 120 m/min at 200 rpm and wire shaking at 260 times/min, the state of paper stock dispersion was examined as follows.

That is, the light source 13 is a stable DC lighting light source (100V,
100W) and a lens system and a photomultiplier tube (the same as in Example 1) as the light receiving section 14 were installed at predetermined positions on the wire at a predetermined distance from the slice entrance section 3, and The electric signal obtained by receiving the transmitted light of the material suspension for 3 minutes was processed at 300 French se by the same signal processing device as in Example 1.
Fig. 3 was obtained by time-division signal processing every c to obtain the coefficient of variation and to examine changes in the paper stock dispersion state in the machine direction.

It can be seen from FIG. 3 that the dispersion state of the paper stock on the wire becomes approximately constant when the distance from the slice entrance 3 is about 3 mm or more. Therefore, this time, we placed the same pair of light sources and light receiving units as above at positions 45 degrees above and 35 degrees below, respectively, from the wire on the straight line B-B, which is at a distance of 3 degrees from the slice opening 3 in Fig. 1. The paper was made under the same conditions as above except that the number of shaking times per minute was changed, signal processing was performed, and as shown in Figure 4, the coefficient of variation showing the paper stock dispersibility with respect to the number of shaking times per minute was determined. I got a curve. As is clear from Figure 4, the dispersion improves as the number of shakes increases, and therefore, when the dispersion condition is determined to be poor by the monitor, it can be seen that the dispersion condition can be improved by increasing the number of shakes. . Example 3 3% filler was added to a hardwood pulp stock suspension with a pulp density of 0.7% at a furnace water level of 36 C on a remesh paper machine with a 20 m wire pad (using one 60 mesh bronze wire). The following monitoring was carried out while producing high-quality paper with a basis weight of 80 m/min at a paper speed of 600 m/min.

In other words, the light source is a strobe flash (flash time: 20 seconds)
ec) and the same lens system and photomultiplier tube as in Example 1 were installed at a position just before the draining line on the wire, and the light transmitted through the stock suspension was received every 40 seconds for 5 minutes to obtain the obtained light. The electrical signals received were processed by the same signal processing device as in Example 1, and the probability density distribution of fluctuations in the amount of received light was investigated. That is, the distribution curve obtained by taking the percentage of the average transmittance as the light amount fluctuation level on the horizontal axis and the frequency of each light amount level on the vertical axis is shown by A in FIG. It was found that the distribution curve A was relatively wide and distributed over a wide range of light intensity fluctuation levels, indicating that the paper stock dispersion state was not good. Therefore, when we added 0.5% sodium polyacrylate (surfactant) based on the amount of pulp to the paper stock suspension of Stockinlet, the distribution curve as shown in Figure 5 was obtained, and the paper stock dispersion state was changed. It turns out that it has improved.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is an explanatory diagram of an example of a paper machine used for carrying out the present invention;
FIG. 2 to FIG. 5 are diagrams showing data obtained by signal processing the electrical signals obtained by detecting the transmitted light of the stock suspension in Examples, and FIG. 3 and 4 are graphs showing the changes in the light transmission position and wire frequency in Example 2, respectively,
FIG. 5 is a probability density distribution curve of fluctuations in the amount of received light in Example 3. DESCRIPTION OF SYMBOLS 1... Paper stock, 2... Head box, 3... Slice opening □, 4... Wire, 5... Prestrol, 6... Couch roll, 7... Suction pick-up roll, 8... Forming board, 9... Water shower device, 10...Hydrof oil, 11...Suction pox, 12...Dandy roll, 13...Light source, 14...Light receiving part. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

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 received by a light receiving section above the wire, and fluctuations in the amount of received light are detected to determine the paper stock behavior. In order to monitor this, it is recommended to emit light from a stable DC lighting light source or strobe flash light source, receive the amount of transmitted light that has passed through the paper stock suspension over a short period of time using a photoelectric converter, and promptly process the signal. Features: A method for monitoring paper stock behavior on a paper machine. 2. A method for monitoring stock behavior on a paper machine according to claim 1, which uses a laser beam source as a stable DC lighting source. 3. A method for monitoring stock behavior on a paper machine according to claim 1 or 2, which uses a photomultiplier tube as a photoelectric converter. 4. A method for monitoring stock behavior on a paper machine according to claim 1 or 2, which uses a phototube as a photoelectric converter. 5. A method for monitoring stock behavior on a paper machine according to claim 1 or 2, which uses a photodiode as a photoelectric converter. 6. A method for monitoring paper stock behavior on a paper machine according to claim 1 or 2, which uses a photoelectric cell as a photoelectric converter.