JPH0465334B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for measuring the degree of beating of suspended pulp in the pulp and paper industry.

(Conventional technology) Pulp, the raw material for paper, usually has a width of 10 to 50 μm.
It is a wood fiber with a length of 0.5 to 3 mm, and the pulp is subjected to various treatments before being made into sheets in the papermaking process. The typical process is a mechanical process called beating, in which the fibers are crushed, cut, swollen, etc. by a beating machine, and the fibers are cleaved, which is called external fibrillation. .

Beating is a process in which fibers are subjected to such treatment, and the properties of the resulting paper vary dramatically depending on the degree of beating. In other words, the important factor that determines the properties of paper is the beating process, and depending on the extent to which this process is applied, paper with different properties can be produced even from pulp made from the same raw material, and more than 80% of the paper is due to the beating process. It is said that it will be determined by

Conventionally, the Canadian Standard Freeness Test Method has been used as a method to express the degree of beating, which is an important factor, and is commonly used and quantified as the CSF value, but this is difficult to measure due to the complex fibers mentioned above. It merely shows the changes in values as a single numerical value, and that value alone does not necessarily reflect the properties of the paper obtained. Thus, there has been a desire for a method that can separate and measure the degree of external fibrillation among the changes in fibers caused by beating.

For the purpose of separating and measuring the degree of external fibrillation, for example, Japanese Patent Laid-Open No. 53
An optical measurement method as disclosed in Japanese Patent No. -41506 has been proposed.

In this measurement method, a light beam irradiated from a light source and transmitted through a pulp suspension sample is separated into a straight light component and a scattered light component by a separating section composed of an integrating sphere, and the intensity of these components is measured. The degree of external fibrillation and internal fibrillation of pulp fibers is derived from the scattering ratio derived from the respective intensities and the respective intensities when the sample is only water.

(Problems to be Solved by the Invention) In the conventional measuring method described above, only the scattered light component at the front position of the suspension in the direction of irradiation of the light beam is used as the scattered light component. Even if there is a noticeable difference in the measurement light intensity corresponding to the difference in , it is not possible to perform high-sensitivity measurement due to this difference.

Furthermore, in the above-mentioned conventional technology, the relationship between the scattering ratio and the degree of beating is derived using the pulp concentration as a parameter, but how can the degree of beating of a pulp suspension in which the pulp concentration is unknown or fluctuate be measured? Or, the technical means for deriving it are not disclosed at all.

The present invention has been made in view of the above points, that is, the degree of external fibrillation of a pulp suspension whose concentration is unknown or fluctuates is separated from other parts, and the degree of external fibrillation, together with the concentration, is transferred in a non-contact manner. The purpose of this invention is to provide a measurement method that can perform measurements with high sensitivity and accuracy using the following formulas.

(Means for Solving the Problems) To explain the means for solving the above-mentioned problems, the measurement method of the present invention includes an optical measurement section and an acoustic measurement section in the transfer path of the pulp suspension to be measured. The optical measurement unit includes a measurement light irradiation device that irradiates the pulp suspension with measurement light, and a measurement light that can measure the measurement light that has passed through the pulp suspension at the front and rear positions. The acoustic measuring section includes an ultrasonic transmitter/receiver that transmits ultrasonic waves through the pulp suspension and measures the amount of attenuation thereof. The amount of attenuation of the ultrasonic waves due to the pulp suspension is measured, and the pulp concentration is calculated based on the correspondence between the amount of attenuation and the pulp concentration. The gist is to calculate the beating degree based on the correspondence between the measuring light intensity corresponding to the concentration of the pulp suspension calculated in the acoustic measuring section and the beating degree. It is something to do.

(Function) When a measuring light is irradiated onto a pulp suspension having a constant pulp concentration and the intensity of the measuring light passing through the pulp suspension is measured and the relationship with the degree of beating is investigated, it is found that The measurement light intensity changes in accordance with the degree of refining, and the direction of change is the opposite.The side where the change in the measurement light intensity appears conspicuously in response to the change in the degree of refining is the above-mentioned front position or rear position. It can be seen that it appears on either side of the position. Therefore, if the correspondence between the above-mentioned measurement light intensity and the degree of beating is determined in advance in accordance with the pulp concentration, by measuring the pulp concentration together with the above-mentioned optical measurement, it is possible to determine the value of the pulp suspension to be measured. The degree of beating can be calculated from the measured light intensity at the front or rear position where the corresponding change is noticeable.

On the other hand, when ultrasonic waves are transmitted through a pulp suspension, the attenuation amount is measured, and the relationship between the ultrasonic wave attenuation amount and the pulp concentration is examined, it is found that the pulp concentration and the ultrasonic attenuation amount are approximately the same regardless of the degree of beating. It can be seen that there is a linear correspondence relationship. Therefore, if the correspondence between the pulp concentration and the ultrasonic attenuation amount is measured in advance according to the type of pulp, etc., the pulp concentration of the pulp suspension can be calculated from the ultrasonic attenuation amount.

Based on the above, an optical measuring section that measures the former and an acoustic measuring section that measures the latter are installed in the transport path of the pulp suspension, and the latter measurement in the acoustic measuring section measures the pulp concentration. The degree of beating of the pulp suspension flowing through the transfer path can be calculated by measuring the former and feeding it back to measure the former in the optical measuring section.

(Example) Next, embodiments of the present invention will be described with reference to the drawings.

Reference numeral 1 is a measurement light irradiation device that irradiates measurement light such as a laser beam onto the pulp suspension L to be measured, and 2 is a measurement light intensity measurement device that measures the intensity of the measurement light that has been irradiated and passed through the suspension L. It is. These devices 1, 2
The optical measurement section A is constructed from the following. The measuring device 2
is configured to be able to measure at the front position a and the rear position b of the suspension L with respect to the irradiation direction of the measurement light. To explain a specific example of this measuring device 2,
In the device shown in FIG. 1, light intensity sensors 3 are arranged at a plurality of positions on the circumference at appropriate distances from the suspension L, from the front position a to the rear position b of the suspension L. The measurement light intensity at a plurality of positions a and b is measured by each light intensity sensor 3. As another example of measuring light intensity at multiple positions as in this specific example, although not shown, a single light intensity sensor is moved continuously from the front position a to the rear position b. Measurements can also be made at one or more locations. Note that the minimum measurement position for the measurement light intensity is one point for each front position a or rear position b, but it may be configured so that measurements can be made at more points than that, as described below. The degree of freedom in measurement can be increased. Reference numeral 4 denotes a transparent storage section that stores the suspension to be measured, and this storage section 4 may be configured as an independent container, or as shown in FIGS. 2 and 8, It can also be constructed in part or for measuring a flowing suspension.

However, in the configuration shown in Fig. 1, first, as a model of pulp fiber, the distribution of the measurement light intensity from the front position a to the rear position b is measured for rayon fibers with different fiber diameters and lengths. The result is as shown in FIGS. 3a and 3b. ``a'' is the case when the light intensity of the measurement light incident on the sample is increased, and ``b'' is the case when the light intensity is decreased.Characteristics appear at the rear and front positions b and a, respectively, and from these results, it is possible to determine the effect on the measurement light intensity. It can be seen that the influence of fiber morphology is dominated by the size of the diameter rather than the length of the fiber. From this,
It can be seen that such optical measurements can measure changes in the fiber's radial direction.

Next, the hardwood bleached kraft pulp is beaten and CSF
When the distribution of the above-mentioned measurement light intensity is measured for pulp suspensions with pulp concentrations of 2, 1, and 0.5 (%) for 340, 412, and 580 (ml), respectively, the results are as follows in Figure 4 a, b, It becomes as shown in c. These measurement results show that at a constant pulp concentration, a difference occurs in the measurement light intensity due to a change in CSF. For example, as CSF decreases, that is, as beating progresses, the measurement light intensity increases at rear position b. , it can be seen that, on the contrary, it becomes smaller at the front position a. Therefore, paper was made using the above-mentioned CSF pulps as raw materials, and the specific rupture degree, which is one of the physical properties of paper, was measured.The results are shown in the table in the figure. It can be seen that the intensity is changing. Therefore, at a certain pulp concentration, by measuring and finding the correspondence between the degree of beating corresponding to the pulp concentration and the measured light intensity in advance, the degree of beating can be calculated from the measured light intensity. I know what I'm getting.

Next, it will be considered which factor of the above-mentioned cutting, crushing, swelling, or splitting of the fibers represents the degree of beating of the pulp calculated in this way. First of all, as mentioned above, in measurements using rayon fibers, the change in the measurement light intensity due to changes in fiber length is slight, so even in pulp, the degree of fiber cutting is smaller than the degree of beating in the present invention. It can be inferred that it is not included. Figure 5 shows the pulp density at the time of beating of 10% and 30%.
%, the measured light intensity for pulp suspensions is shown to change with respect to CSF, and it can be seen that the measured light intensity differs between pulp concentrations of 10% and 30%. By the way, pulp that has been beaten at a pulp concentration of about 30% is called high-concentration beaten pulp, and this shows properties that are clearly different from pulp that has been beaten at a pulp concentration of about 10%. The cleavage is severe and significant external fibrillation has occurred, and although they show the same value in conventional CSF, which indicates the degree of beating, they can be clearly identified in optical measurements.

From these facts, in the present invention, it can be considered that the degree of beating can be measured mainly based on the degree of external fibrillation.

As described above, the present invention calculates the degree of beating by using the correspondence between the degree of beating determined by previous measurements and the measured light intensity based on the change in the measured light intensity after passing through the pulp suspension. Therefore, when calculating the degree of beating, it is necessary to find a change in the measurement light intensity by some method. A method for determining this change is, for example, at an appropriate position on either side of the front position a or the rear position b (for example, in the case of the measurement conditions shown in the figure, at an angle of 150° where the difference in measurement light intensity is most significant). The front position a or the rear position b is determined from the integral value by integrating the measured light intensity distribution on either side of the front position a or the rear position b, which is determined from the value of the measured light intensity at the position of It can be determined by any appropriate method such as a method of determining from the value of the ratio of the measured light intensities at two appropriate positions on either side.
That is, in these methods, the correspondence between the measured light intensity, integral value, ratio value, and degree of beating is measured in advance and prepared as data in a memory element in a microcomputer or the like.
The degree of beating can be easily calculated from these values at the time of measurement. Incidentally, in the embodiment shown in FIG. 4, the difference in the measurement light intensity due to the difference in the degree of beating is noticeable at the rear position at an angle of 140° to 150°, where the measurement light intensity peaks. Similar to the measurement results for the rayon fibers described above, by adjusting the light intensity of the measurement light or the gain of the light intensity sensor 3, the position where the difference in measurement light intensity is noticeable is determined as the front position a. Alternatively, it can be on either side of the rear position b.Also, even when the light amount and gain are constant, there is a position where the difference in measurement light intensity appears significantly depending on the concentration of the pulp suspension to be measured. Front position a
The degree of beating can be calculated with high sensitivity and accuracy by using the measured light intensity at an appropriate position of front position a or rear position b depending on each of these conditions. can do. For example, if the concentration of the pulp suspension to be measured is known through prior measurement and does not change, the position where the difference in measurement light intensity will be noticeable can be known in advance, so in such a case, The measurement light intensity measuring device 2 can be configured to be able to measure the measurement light intensity only at such a position. However, in the present invention, the measurement light intensity can be measured at a plurality of positions such as the front position a and the rear position b, so the measurement position can be appropriately selected depending on the properties of the pulp suspension. It is possible to increase the degree of freedom of the measurement, and therefore, it is possible to perform measurements with higher accuracy.

Next, reference numeral B in FIG. 8 indicates an acoustic measuring section which is provided in the transport path C of the pulp suspension, one after another to the optical measuring section A, and this acoustic measuring section B is The structure includes ultrasonic transmitting/receiving devices 5 and 6 that transmit ultrasonic waves through the pulp suspension being transferred and measure the amount of attenuation of the ultrasonic waves.

FIG. 6 shows the results of measuring the amount of attenuation corresponding to the change in pulp density of the bleached hardwood pulp against ultrasonic waves at a frequency of 2 MHz in the acoustic measuring section B. From these measurement results, it can be seen that in a pulp concentration range of about 0 to 2.5%, the pulp concentration and the ultrasonic attenuation amount have a substantially linear correspondence regardless of the degree of beating. Therefore, it can be seen that by measuring and finding the correspondence between the pulp concentration and the ultrasonic attenuation in advance according to the type of pulp, etc., it is possible to calculate the pulp concentration from the measured ultrasonic attenuation. . In this way, the pulp concentration is calculated in the acoustic measurement unit B installed in the transport path C of the pulp suspension, and at the same time, in the optical measurement unit A, the degree of beating corresponding to the pulp concentration is determined as described above. The degree of beating can be calculated from the correspondence with the measured light intensity.

Next, the above operation will be explained in more detail. 7th
Figures a, b, and c are pulp concentration 0.5 to 2.5%, CSF600 to
This diagram schematically shows the measurement results for 200 (ml) of pulp suspension, and the difference in measured light intensity due to the difference in degree of beating is most noticeable at rear position b at an angle of 150°. be. In all of these figures, the solid line indicates the distribution at a predetermined pulp concentration and degree of beating, that is, the measured light intensity distribution in the standard state. The broken line in a shows the measured light intensity distribution when only the pulp concentration changes from the reference state, that is, when the pulp concentration increases;
The measured light intensities at rear positions a and b change significantly in opposite directions. As mentioned above, such changes in pulp concentration can be measured in the acoustic measuring section B, so by determining the correspondence between pulp concentration and measurement light intensity through prior measurement, changes in pulp concentration can be measured. It is possible to calculate the change in the measured light intensity caused by the change in the measured light intensity. Next, the broken line b shows the measured light intensity distribution when only the degree of beating changes from the steady state, that is, when the degree of beating progresses, and only the measured light intensity at the rear position b increases. When the pulp concentration is constant, the degree of beating can be calculated based on the change in the measured light intensity using the correspondence between the degree of beating measured in advance and the measured light intensity as described above. Furthermore, c
From the reference state shown by the curve and the curve, respectively, cases in which the concentration did not change and only the degree of beating progressed, cases in which the degree of beating did not change and only the concentration increased, and cases in which the degree of beating progressed as the concentration increased. This shows the measured light intensity distribution in the case of When the pulp state shifts from a curved state to a curved state in this way, the measured light intensities at the front and rear positions a and b both change in opposite directions. However, in the curved state, the change in the measured light intensity at the rear position b includes both the pulp concentration and the change due to the degree of beating, so these must be separated. As described above, by measuring the pulp concentration in the acoustic measuring section B, it is possible to calculate the change in the measurement light intensity due to the change in the pulp concentration, so that these can be easily separated. Thus, the present invention can also measure the degree of beating of pulp suspensions of unknown concentration.

(Effects of the Invention) As described above, the present invention feeds back the pulp concentration measured in the acoustic measurement section to the measurement of the degree of beating in the optical measurement section, thereby controlling the pulp suspension flowing through the transfer path. It is possible to calculate the degree of beating of pulp even if the pulp concentration is unknown or fluctuates, and in this way, the degree of beating mainly due to external fibrillation can be measured in a non-contact manner with high sensitivity and precision in the transfer route. Therefore, there is an effect that control and quality management in various processing steps of the paper manufacturing process can be performed well.

[Brief explanation of the drawing]

Figures 1 and 2 are explanatory diagrams showing the measurement system of the method of the present invention, Figures 3a and b are actual measurement diagrams of optical properties of a model fiber (rayon) using the measurement system of the method of the present invention, and Figure 4a , b, c are actual measurement diagrams of the optical characteristics of LBKP using the measurement system of the method of the present invention, Figure 5 is a diagram of optical characteristics when the pulp concentration is changed, and Figure 6 is a diagram of ultrasonic attenuation characteristics with respect to pulp concentration. , Figure 7a,
b and c are explanatory diagrams of a model showing changes in the state of optical properties when the degree of beating and pulp concentration are changed, and FIG. 8 is an explanatory diagram of another configuration of the present invention. Symbols A...Optical measurement section, B...Acoustic measurement section, C...Transfer route, L...Pulp suspension, 1...
...Measurement light irradiation device, 2...Measurement light intensity measurement device,
3...Light intensity sensor, 4...Accommodating section, 5...Ultrasonic transmitter, 6...Ultrasonic receiver.

Claims (1)

[Claims] 1. A measurement light irradiation device that irradiates measurement light onto a pulp suspension to be measured, and a measurement light intensity that can measure the measurement light intensity that has passed through the suspension at positions in front and behind the measurement light irradiation device. A measurement device constitutes an optical measurement section, and the optical measurement section measures the measurement light intensity at the front or rear position, and measures the measurement light intensity corresponding to the concentration of the suspension and the beating. A method for measuring the degree of beating of suspended pulp, characterized in that the degree of beating is calculated based on a correspondence relationship with the degree of beating. 2. A measurement light irradiation device that irradiates measurement light onto the pulp suspension to be measured, and a measurement light irradiation device that irradiates the measurement light onto the pulp suspension to be measured, and is capable of measuring the intensity of the measurement light that has passed through the suspension at positions in front and behind the measurement light irradiation device. an optical measuring section equipped with a measuring light intensity measuring device; and an acoustic measuring section equipped with an ultrasonic transmitting and receiving device that transmits ultrasonic waves through the suspension and measures the attenuation amount thereof, The attenuation of the ultrasonic waves due to the suspension is measured in the acoustic measuring section, and the pulp concentration is calculated based on the correspondence between the attenuation and the pulp concentration, and the optical measuring section Measure the measured light intensity at the front or rear position, and calculate the degree of beating based on the correspondence between the measured light intensity corresponding to the concentration of the suspension calculated in the acoustic measuring section and the degree of beating. A method for measuring the degree of beating of suspended pulp.