JPH0461301B2 - - Google Patents

Description

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

(Prior art and object of the invention) Pulp, which is 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 subjected to crushing, cutting, swelling, etc. processes by a beating machine, and the fibers are split, 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

Another important factor that changes the properties of paper is the pulp concentration in the treatment process or papermaking process. Conventional methods for measuring pulp concentration include methods that use the principle that the fluid resistance of a suspension depends on its concentration, and methods that use the principle that there is a correlation between the concentration of a suspension and its light transmission characteristics. However, these methods tend to measure various disturbance factors at the same time, making it difficult to obtain the true pulp density. In the past, there was no suitable measuring method for monitoring pulp density, so it was difficult to obtain treated pulp of a certain quality in the treatment process or to make paper of a certain quality in the papermaking process. It was difficult.

An object of the present invention is to provide a measuring method that can optically and non-contactly measure the pulp density.

(Structure and operation of the invention) In order to achieve the above-mentioned object, the present invention includes a measurement light irradiation device that irradiates measurement light onto a pulp suspension to be measured, and a measurement light irradiation device that irradiates measurement light to a pulp suspension to be measured. and a scattered light intensity measurement device that measures at the rear position, and the optical measurement unit calculates the ratio of the scattered light intensity at the front and rear positions, and calculates this ratio. The gist of this method is to calculate the pulp density based on the correspondence between and the density.
A detailed explanation will be given below based on an example.

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 and 2 constitute an optical measurement section A. The measuring device 2 is configured to be able to measure the suspension L at a front position a and a rear position b with respect to the irradiation direction of the measurement light. To explain a specific example of this measuring device 2, the one shown in FIG. 1 is a device that extends from the front position a of the suspension L to the rear position b on the circumference at an appropriate distance from the suspension L. Light intensity sensors 3 are arranged at a plurality of positions, and each light intensity sensor 3 detects the position a,
The measurement light intensity is measured at a plurality of positions in b. 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. The minimum measurement position for the measurement light intensity is one point each at the front position a and the rear position b, but by configuring it so that it can be measured at many points, the measurement described later can be carried out. The degree of freedom can be increased. Reference numeral 4 designates a transparent storage section that accommodates the suspension to be measured, but this storage section 4 may be configured as an independent container, or it may be configured as a part of the piping system as shown in Fig. 2. Alternatively, a flowing suspension may be measured.

However, by beating the bleached hardwood kraft pulp,
When the above-mentioned distribution of measurement light intensity is measured for pulp suspensions with pulp concentrations of 2, 1, and 0.5 (%) for CSF of 340, 412, and 580 (ml), respectively, the third
As shown in Figures a, b, and 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. , on the contrary, it becomes small at the front position a. It is also noteworthy that as the pulp concentration changes, the measured light intensity at the front position a and the measured light intensity at the rear position b significantly change in opposite directions.
That is, as the pulp density decreases, the measured light intensity at the front position a increases, and conversely, it decreases at the rear position b. Now, based on the above measurement results, we calculate the ratio γ of the measured light intensity at the front position a and the rear position b, and find the relationship between this and the pulp density. The result will be as shown below. γ is expressed as follows: γ=Measurement light intensity at an appropriate rear position/Measurement light intensity at an appropriate front position... (1) In Figure 4 a, b, and c, the front position a is 150°. , 100°, and 100°, and 10°, 60°, and 80° are used as the rear position b, respectively. In this way, the front position a and the rear position b may be selected as appropriate.
For example, a is selected as a position where both the front position a and the rear position b have high measurement light intensity.

As shown in FIGS. 4a, b, and c, there is a substantially linear correspondence between γ and pulp density, and it can be seen that pulp density can be determined from γ. Then, when determining the difference in pulp density due to the difference in degree of beating corresponding to the same γ value, the maximum is about 0.15% in the range of CSF 340 to 580 (ml) (for example, γ value 2 in Figure 4 a).
The difference in pulp density corresponding to the difference in pulp concentration (difference in pulp concentration) becomes smaller as the γ value becomes smaller, and becomes smaller as the range of beating degree becomes narrower. Based on these facts, by determining the correspondence between γ and pulp concentration in advance by measuring various pulp suspensions, it is possible to calculate pulp concentration from γ determined by measurement with a high degree of accuracy. I know what I'm getting. The above calculations can be easily performed by storing the correspondence relationship as a data table or the like in a storage device in a microcomputer or the like.

By the way, when measuring the measurement light intensity in the optical measurement section A, for example, the light amount of the measurement light changes,
Alternatively, when the sensitivity of the light intensity sensor 3 changes, the measured light intensity changes in the same direction overall from the front position a to the rear position b. However, as described above, the present invention calculates the ratio γ of the measured light intensity at the front position a and the rear position b, and uses the correspondence between this γ and the pulp concentration, so the above-mentioned change is caused by γ are added to the denominator and numerator respectively when calculating , and therefore the influence of such changes is small.

(Effects of the Invention) As described above, the present invention includes a measurement light irradiation device that irradiates measurement light onto a pulp suspension to be measured, and a measurement light irradiation device that measures the measurement light intensity that has passed through the suspension at the front and rear positions thereof. an optical measuring section equipped with a measuring light intensity measuring device, and a correspondence relationship between the ratio of the measuring light intensities at the front position and the rear position measured by the optical measuring section and the pulp concentration. Since the pulp density can be calculated in a non-contact manner, it is possible to measure the pulp density in a non-contact manner, and therefore, a batch method can also be used as a continuous method instead of a solid method, which can be used to control various processing steps in the papermaking process. It also has the advantage that it can be used for quality control, etc. In particular, as described above, in the present invention, the ratio of the measurement light intensity at the front position and the rear position corresponds to the pulp concentration, so that, for example, the light intensity of the measurement light may change or the light intensity sensor may This has the advantage that it is less affected by disturbances that cause the measurement light intensity to change in the same direction as a whole from the front position to the rear position, such as a change in sensitivity.

[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, b, and c are actual measurement diagrams of the optical characteristics of LBKP using the measurement system of the present invention, and Figures 4a, b,
FIG. 3c is an explanatory diagram of the relationship between the γ value and the pulp density based on FIGS. 3a, b, and c. Symbol A: Optical measurement unit, B: Acoustic measurement unit, L: Pulp suspension, 1: Measurement light irradiation device, 2: Scattered light intensity measurement device, 3: Light intensity sensor, 4 ...Containment department.

Claims (1)

[Claims] 1 Optical measurement using a measurement light irradiation device that irradiates measurement light onto the pulp suspension to be measured, and a measurement light intensity measurement device that measures the measurement light intensity that has passed through the suspension at positions in front and rear of the measurement light irradiation device. The apparatus comprises a part, and calculates a ratio of measured light intensities at the front and rear positions in the optical measuring part, and calculates the pulp density based on the correspondence between this ratio and the density. Method for measuring the concentration of turbid pulp.