JPS628148B2 - - Google Patents

Description

Detailed Description of the Invention The present invention relates to a method for measuring the potassium permanganate value (hereinafter abbreviated as K value) of unbleached pulp, and in particular to a method for measuring the permanganate potassium value (hereinafter abbreviated as K value) of unbleached pulp. This relates to a method for automatically performing operations up to the calculation of measured values.

The K number of pulp is measured as an index of the degree of delignification, and bleaching conditions are not only set based on the K number, but also various changes in the cooking process, such as the amount of cooking chemicals added, the cooking temperature, and the wood chips. This value is also useful as a means of understanding changes in factors that affect the degree of digestion, such as accompanying moisture. The K value is calculated from the amount of potassium permanganate consumed by the test sample under certain conditions of sulfuric acid acidity, and the measurement method is as specified in JIS P8206.
Generally, measurements are carried out by manual analysis based on this standard method, but automatic measuring devices have been developed to save labor. However, the current situation is that this automatic measuring device requires a considerable amount of manpower and is not very quick, since it is necessary to precisely weigh the pulp sample before using it for measurement.

In view of the above circumstances, the inventors of the present invention investigated various methods for measuring the K number, and as a result, they decided to automatically collect pulp slurry samples from the pulp manufacturing process and automatically perform all measurement operations and calculate the measured values. We have completed a fully automated rapid K value measurement method that can be carried out on a daily basis.

This method will be explained in detail below.

Unbleached pulp at the stage where K value measurement is required is usually made up of cooking waste and undigested material (so-called knot lees,
It is a flocculent lees (hereinafter referred to as "lees"), and it is necessary to separate it from the sample for K value measurement. Industrially, various screens or water cyclones are usually used to separate and wash the cooking waste. However, in the case of samples for K value measurement, the amount of sample may be small, and it is desirable to quickly separate the cooking waste and lees, and various research studies have been conducted on ways to automatically perform this operation. As a result, it was determined that the following method or apparatus was appropriate.

First, a sample collected from the pulping process after cooking is guided onto a mesh or slit with openings that do not allow pulp fibers to pass through, and is washed with water using a washing water shower while removing the cooking liquid. In order to automatically carry out this operation, it is best to use a rotating body that is a horizontally placed cylinder or truncated cone whose circumferential surface is formed of a net or slits. Next, in order to remove the lees, it is better to use a mesh or slits with openings that allow only pulp fibers to pass through, but it is better to use a rotating body with a cylindrical or truncated conical surface formed of a mesh or slits, and It is most effective to rotate the rotating body horizontally. Furthermore, it goes without saying that it is better to connect and rotate the cooking waste liquid separation and washing device and the lees removing device.

That is, FIG. 1 is an example of this, and is a side sectional view showing the outline of a rotary washing and dregs removing device, in which a cylindrical or truncated conical device is installed horizontally. A net or slit with a small opening of about 40 meshes is provided on the front stage 1 of the peripheral surface, and a net or slit with a large opening of about 15 to 20 meshes is arranged on the rear stage 2 of the peripheral surface, and an inlet 3 is provided. An unbleached pulp sample is introduced from the washing water line 4, the washing water is showered from the washing water line 4, the rotation center 5 is rotated at 20 to 40 rpm, and the washing liquid is discharged from the front stage discharge port 6 and the second stage discharge port 7. It is preferable to use a device that is capable of taking out the pulp slurry for K value measurement from the outlet 8 at the same time as discharging the lees.

Next, the method for collecting pulp samples of a certain weight will be described.

During the manufacturing process, pulp is usually 20 to 0.1
It exists in the form of a slurry with a concentration within the range of 1.5%, but in order to collect a certain weight of pulp sample from the pulp slurry, an appropriate amount of pulp slurry must be collected, dried, and weighed to a predetermined amount. There are possible ways. However, it is quite difficult to carry out drying and weighing operations quickly and automatically, and depending on the drying method, the pulp fibers may become keratinized, resulting in poor disintegration into single fibers during the K value measurement described below. As a result, the reaction with potassium permanganate may become insufficient and accurate measurement results may not be obtained, and there may be cases where different measurement values are obtained due to deterioration of the pulp fibers.

In addition, in order to collect a pulp sample of a constant weight, it is possible to know the concentration of the pulp slurry and then calculate backwards to collect a constant volume. Conventional methods for measuring the concentration of pulp slurry include (i) the relationship between pressure loss and pulp concentration when the pulp slurry passes through a pipe, and (ii) the torque required to rotate a rotor at a constant speed in the pulp slurry. Relationship with Pulp Concentration (iii) A method is known that utilizes the relationship between pulp concentration and the rotational speed of a disk or cone rotating at a constant torque in pulp slurry.

Among these methods, methods (ii) and (iii) have been put into practical use, but since both methods utilize the mechanical properties of the slurry, the measurement accuracy is not good, and It is inevitable that there will be an error of about 10 to 30%, depending on the situation.

For the purpose of the above, the present inventors have conducted various studies and research on methods for measuring the concentration of pulp slurry with high accuracy. As a result, as shown in the example of the relationship between pulp slurry concentration and absorbance shown in Figure 2, the present inventors have It has been found that there is a close relationship between the amount of transmitted light and pulp density. In other words, when light is incident from one side of a pulp slurry layer of a constant thickness, the incident light (Ii), transmitted light (It), and pulp density (C)
It was found that the following relationship holds true between .

C=k(-logIt/Ii) where k: constant In the above equation, -log(It/Ii) is what is called absorbance, and the pulp concentration can be accurately determined from the measured absorbance of the pulp slurry. We found out that it is possible.

Although the light that can be used in the ink may have any spectrum, it goes without saying that the less scattering of light within the pulp slurry layer, the better. The data in FIG. 2 shows the relationship between the concentration of LUKP slurry and the absorbance of monochromatic light at 600 nm.

Although it is necessary to detect the transmitted light and convert it into an electrical signal for the purpose described later, any detector such as a phototube, photomultiplier tube, or photodetection diode can be selected and used.

The pulp slurry concentration was measured as described above,
It is sufficient to collect a predetermined volume of pulp slurry calculated backward from the required weight of pulp fibers, and for this purpose, it is appropriate to adopt one of the following two methods.

The first method is to collect an arbitrary amount of selected unbleached pulp slurry from which cooking waste and lees have been separated using the apparatus shown in FIG. That is, an arbitrary amount of selected unbleached pulp slurry is put into the dilution tank 9, and while circulating through the piping system 11 with the pump 10, light from the light source 13 is irradiated into the flow cell 12 installed in the piping system 11 for detection. While the transmitted light is continuously measured by the detector 14, dilution water is injected from another fresh water line, and when a predetermined pulp concentration, that is, a predetermined absorbance is reached, an electric signal from the detector 14 triggers the electromagnetic valve of the fresh water line. 1
5 and then measure a certain volume of pulp slurry in the dilution tank. If the collection volume at this time is set to a certain constant value, the amount of pulp sample for K value measurement is determined, so the pulp concentration of the collected slurry is inevitably determined, and the absorbance of the slurry corresponding to this is determined. The operations described above can be carried out extremely easily if is determined experimentally in advance.

In the second method, as in the case of the first method, the apparatus shown schematically in FIG. , prepare a slurry by diluting it with an arbitrary amount of water, extract this slurry with a pump 10, send it to a flow cell 12, irradiate it with light from a light source 13, and measure the transmitted light with a detector 14, which has been determined in advance by experiment. The amount of slurry liquid corresponding to a certain weight may be automatically calculated from the relationship between the absorbance and the slurry concentration.

To actually perform the above operations, the detector 14
The electrical signal from the microcomputer 17
The amount of pulp slurry to be collected may be calculated based on preset conditions and measured using the measuring device 18.

Next, the operation for measuring the amount of potassium permanganate consumed will be explained.

According to the regulations of JIS P8206, a pulp sample is accurately weighed, put into a beaker, added with distilled water, thoroughly disintegrated with a stirrer, then 4N sulfuric acid is added and kept at a constant temperature. Next, a predetermined amount of 0.1N potassium permanganate was instantly added, and the reaction was allowed to proceed for 5 minutes with sufficient stirring.The reaction was stopped by adding 1N potassium iodide solution, and the fibers in the beaker were released without separating them. The iodine obtained is titrated with 0.1N sodium thiosulfate.
A starch indicator is used at the end point of this titration.

The method of the invention basically follows this operating procedure, but will be explained using the block diaphragm of the measuring device shown in FIG.

The equipment used includes a reaction beaker 19, an automatic brewet 20, a distilled water tank 21, a 4N sulfuric acid tank 22, a 0.1N potassium permanganate tank 23, and a 1N potassium permanganate tank.
It is equipped with a potassium iodide tank 24, a 0.1N sodium thiosulfate tank 25, and a starch indicator tank 26. First, the selected unbleached pulp sample collected in the above-mentioned manner is fed into the reaction beaker 19, and then each of the above reagents is poured into the respective tanks. Namely, distilled water tank 21, 4N sulfuric acid tank 22, 0.1N potassium permanganate tank 23,
A predetermined amount is added according to a predetermined procedure from the 1N potassium iodide tank 24, titrated with sodium thiosulfate sent from the 0.1N sodium thiosulfate tank 25 to the automatic brewet 20, and then added to the starch indicator tank 26.
Add the indicator from. The end point of this titration can be determined by optically detecting the disappearance of the coloration of iodinated starch, but it can also be determined by electrochemically following the redox reaction between iodine and sodium thiosulfate. Automatic addition of each reagent can be easily done by installing a metering tank directly connected to each storage tank and using a water head for each predetermined volume, or by using a pump and setting the time intervals using a timer. It is possible to implement.

It is also possible to directly feed the liquid for a predetermined period of time using a metering pump from the storage tank without providing a metering tank, and it is preferable to use a timer to turn on and off the pump.

In addition, the automatic brewet 20 is equipped with an automatic titration amount mechanism, which allows the microcomputer 17 to read the titration value for each titration and calculate the K number according to a formula input in advance. It is. It is also possible to feed this electrical signal relating to the K number to a control device of another system, for example a pulp cooking system or a bleaching system.

It goes without saying that the method of the present invention is applicable to measuring the K number of any pulp such as kraft pulp and sulfite pulp, and is not limited to the method shown in the drawings attached to the specification.

As explained above, the present invention enables the pulp slurry concentration to be measured by light transmittance, the required sample weight to be measured by volume, and the K number to be automatically measured. This is an extremely valuable invention, as it has made it easy to quickly and accurately manage the system.

[Brief explanation of the drawing]

Fig. 1 is a side cross-sectional view schematically showing a rotary washing/lees removal device, Fig. 2 is an example of the relationship between pulp slurry concentration and absorbance, and Fig. 3 is a schematic diagram of an example of a pulp slurry sampling device. , FIG. 4 is a schematic diagram of another example, and FIG. 5 is a block diagram of an automatic potassium permanganate consumption measuring device. In the figure, 1... front stage of circumferential surface, 2... rear stage of circumferential surface, 3... inlet, 4... washing water line, 5... rotation center, 6... front stage discharge port, 7... rear stage discharge port, 8... outlet, 9... Dilution tank, 10... Pump, 11... Piping system, 12... Flow cell, 13... Light source, 14... Detector, 15... Solenoid valve, 16... Container, 17... Microcomputer, 18... Meter, 19... Reaction beaker, 20 …
Automatic brewer, 21... Distilled water tank, 22...
4N sulfuric acid tank, 23...0.1N potassium permanganate tank, 24...1N potassium iodide tank, 25...0.1N
Sodium thiosulfate tank, 26... Starch indicator tank.

Claims (1)

[Claims] 1. In measuring permanganate potassium value of unbleached pulp, a part of the unselected pulp flowing during the pulp manufacturing process is continuously separated, and the accompanying cooking effluent is collected. After removing and washing and removing undigested materials, the concentration of the pulp slurry is determined by measuring the light transmittance of the pulp slurry, and based on the concentration, the volume corresponding to the predetermined pulp weight for the sample is determined. The potassium permanganate value of pulp is characterized in that a pulp slurry sample is taken, a corresponding amount of reagent is added to the sample, a titration operation is performed, and the potassium permanganate value is automatically calculated from the measured value. Automatic measurement method. 2. The device used for removing and cleaning cooking waste liquid is a horizontally cylindrical or truncated cone-shaped rotating body that is equipped with a mesh or slits on its circumferential surface that are so open that pulp fibers cannot pass through. A method for automatically measuring the potassium permanganate value of pulp according to claim 1. 3. The device used for removing undigested materials is horizontally placed in the shape of a cylinder or truncated cone, and has a mesh on its circumferential surface with openings that allow pulp fibers to pass through but not allow undigested materials to pass through; The method for automatically measuring the potassium permanganate value of pulp according to claim 1, which comprises a rotating body provided with slits. 4. The method for automatically measuring permanganate potassium value of pulp according to claim 1, wherein the washing device and the undigested material removal device rotate coaxially. 5. A flow cell is installed in the piping system that introduces the pulp slurry into a dilution tank, sucks the slurry in the dilution tank with a pump, and circulates it back to the dilution tank, and continuously measures the light transmittance of the slurry. By adding water and collecting a predetermined volume of slurry when a predetermined light transmittance is reached, a pulp sample corresponding to a predetermined weight is collected based on the relationship between the pre-measured light transmittance and slurry concentration. A method for automatically measuring the potassium permanganate value of pulp according to any one of claims 1 to 4, using the method.