JPS6257758B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for simply and reliably preventing pit damage that occurs during pulp or paper manufacturing processes. Specifically, in the pulp or paper manufacturing process, process water is collected from the process before the process where pitch failure occurs, and the treated water obtained by removing suspended matter such as pulp and paper stock contained in the process water. Provided is a method for preventing pit damage in a pulp or paper manufacturing process, which comprises measuring the absorbance of the material by irradiating it with visible light having a wavelength of about 420 nm, and performing pitch damage prevention treatment based on the measured value. It is something.

Pitch is used in the pulp or paper manufacturing process (however, pitch is usually small spherical particles made mainly of organic matter derived from natural resin or gummy pitch or other additives liberated from wood cells during the paper and pulp manufacturing process). (meaning sticky aggregates), and such pitches aggregate and adhere to various parts of the papermaking machinery and equipment such as cheeseboards, beaters, and wires in the above manufacturing process, reducing work efficiency or causing damage to the product. This can lead to various pitch defects such as causing stains or holes in pulp sheets or paper.

Conventionally, various methods have been adopted as measures to prevent such pit damage, but the most effective and common methods include the use of polyphosphates, various surfactants, emulsifiers, fine talc, etc. Adsorbents such as kaolin are used. By adding these to process water at appropriate locations in the pulp and paper manufacturing process, pitches precipitate in the liquid, aggregate into particles of a certain size, adhere to machinery and equipment, and are released. It can have a remarkable effect of suppressing adhesion to paper. However, this method only adds inhibitors after encountering disturbance phenomena that occur during the operation of the manufacturing process, or
Based on experience from past operations, the necessity of adding an inhibitor is understood and used, and pit damage is not predicted and prevented from the characteristics of the process water in advance.

Generally speaking, it is said that the major cause of pitch failure is differences in the types of manufacturing raw materials.
Differences in manufacturing equipment, processes, or manufacturing conditions also have a subtle effect on the occurrence of pitch failures, and in pulp and paper manufacturing processes that involve multiple steps and long periods of time, for example, pitches may precipitate and damage equipment or products. The phenomenon of occurrence of this disorder is extremely diverse, with the location and amount of deposition not being constant. Therefore, although the methods described above are effective in themselves, it is often difficult to take appropriate suppression measures, and the addition of inhibitors is always based on estimation, so it is sometimes unnecessary. Even if there are cases where people are consuming a large amount of it, they tend to ignore it.

In addition to the above, as a conventional measure to prevent pit damage, there is a method of washing the process water with clean water after the cooking or bleaching process, and at this time, increasing the number of times and/or the amount of water Furthermore, increasing the amount of blowing of contaminated process water is considered to be an effective preventive measure, and has been partially implemented. However, this method is not only inferior to the method of adding pitch suppressant in terms of saving fresh water, making equipment investment, and complicating the work, but also has practical disadvantages because it does not predict failures and deal with them in advance. Don't criticize.

In view of these facts, the present inventors have come up with the idea that if the occurrence of pitch injury can be known in advance, it may be possible to take effective and appropriate preventive measures. However, for many years, the present inventors have
As a result of collecting process water from each pulp and paper manufacturing process and the pitch produced therein, we observed and analyzed the water and found that the color and turbidity of the process water were dissolved and/or undissolved in the water. We found that this is a factor that suggests the amount of pitch component present in the dissolved state, and found that when the color and turbidity reach a certain value or higher, troubles due to pitch tend to occur frequently in the actual process. By confirming that this is the case and measuring the absorbance of the process water, we came to the conclusion that it is possible to predict pitch failures that occur during the process.

The present invention is characterized by measuring the absorbance of process water in a pulp or paper manufacturing process, predicting the occurrence of pitch damage based on the value of the absorbance, and implementing means for suppressing pitch damage. It is a method of preventing disorders.

In the pulp or paper manufacturing process, the processes in which pitch damage occurs are often the bleaching process, pulping process, and papermaking process. The sample is collected from the previous process, and its absorbance is measured. Based on this absorbance value, it is predicted that pitch failure will occur after a certain period of time in the previous process, and various types of problems such as those described below are Take measures to prevent pitch injury.

Therefore, the location where the process water for absorbance measurement is collected is preferably a location that allows sufficient time to take measures to prevent pit damage after measuring absorbance and prevent the occurrence of such damage. . for example,
Even if it is possible to predict the occurrence of pitch failure in a subsequent process based on the absorbance of excess water in a certain process,
If there is not enough time, there is a high risk that treatment will be delayed. Therefore, it is preferable that the place where the process water for absorbance measurement is collected has a margin of at least 1 hour from the time when pitch trouble is predicted based on the absorbance until the pitch trouble actually occurs. Furthermore, the earlier the occurrence of a failure is predicted, the easier it will be to take measures. In other words, suitable process water collection points include processes before the bleaching process, pulping process, and papermaking process where pitch failure often occurs in the pulp or paper manufacturing process, such as the finishing tower after the washing process. These include the entrance section and the adjustment process. Moreover, there may be two or more sampling locations as necessary.

The collected process water is subjected to treatment to remove suspended matter. Here, the removal treatment of suspended matter refers to the removal treatment performed to the extent that colored substances, dissolved substances, and fine suspended matter (for example, those that give a colloidal solution) remain in the process water after removal. means. This removal process can be carried out using a suitable sieve. If the size of the mesh on the surface that meets the purpose of the present invention is expressed in paper, Toyo Paper's Nos. 1 to 3 are suitable.

The treated water thus obtained is subjected to absorbance measurement. Absorbance can be easily measured by irradiating visible light and using a photoelectric colorimeter. For example, a photoelectric colorimeter such as Elma Photoelectric Colorimeter Model AE-11 manufactured by Elma Optical Co., Ltd. may be used. As a result of various studies conducted by the present inventors, it has been found that irradiation with visible light having a wavelength of, for example, around 420 nm is preferable.

It was found that there was a certain correlation between the measured absorbance and pitch damage. In the field studied by the present inventors, pitch failure occurred, for example, when the absorbance showed a value of 0.15 or more. However, differences in raw materials for pulp and paper,
Depending on the additives to the process and the equipment used, there may be some variation between the magnitude of absorbance and the occurrence of pitch failure. Such fluctuations can be easily standardized in each factory by keeping the conditions for removing suspended matter constant and referring to the above absorbance value.

The absorbance is then measured and if a risk of pitch injury is detected, preventive measures are taken. In the pulp or paper manufacturing process, steps to take preventive measures include steps before the step where pitch failure occurs, for example, at the outlet of the finished column after the washing step and at the chest of the conditioning step.

Prophylactic treatment can be carried out by the addition of anti- or inhibitory agents for pitch injury, such as polyphosphates, various surfactants, emulsifiers, talc, kaolin, silica sulfate, etc. Alternatively, a method of washing the process water with clear water or a method of partially blowing the process water may be used. Although any preventive treatment method may be used, an appropriate treatment may be selected depending on the degree of occurrence of pitch injury, that is, the magnitude of absorbance.

On the other hand, by measuring the absorbance, it can be determined that there is no or a low possibility that pitch injury will occur, and unnecessary preventive measures can be omitted. This can be said to be a great advantage brought about by the present invention in terms of resource saving and economy.

Next, the present invention will be explained with reference to examples.

Example 1 Paper factory: Unbleached kraft paper using N wood (softwood) and L wood (hardwood) as raw materials Paper manufacturing process Absorbance measurement location: Chest entrance process of adjustment process Type of paper used for water filtration: Toyo Paper No. .1 When measuring absorbance, wavelength of incident light: 420nm Pitch failure location: No. 1 blanket suction box situation: If absorbance (-logT) ^* is less than 0.12,
There is almost no dust adhesion, cleaning about once a week is sufficient, and the absorbance is 0.12 or more.
When it was less than 0.18, cleaning about once every three days was sufficient. However, when the absorbance reaches 0.18 or higher, cleaning is required once every 2 to 3 hours.
This became a major operational problem. A variation of 0.18±0.02 is observed depending on summer and winter, but 0.18
Above 90% of problems will occur.
It could be predicted with a probability of over %.

*Absorbance = -logT (T: /I ₀ , ₀ : incident light,
: Transmitted light) Measured with Elma AE-11 photoelectric colorimeter manufactured by Elma Optical Co., Ltd. Example 2 Paper mill: GP (ground pulp), KP (kraft pulp), medium-quality paper manufacturing process using waste paper as raw materials Absorbance measurement location: Mixing chest outlet in the adjustment process Type of paper used for process water filtration : Toyo Paper No.
3 Wavelength of incident light when measuring absorbance: 420nm Pitch failure: Dust on the product Condition: When the absorbance is less than 0.30, there is almost no dust on the product and it is good, and the absorbance is 0.30.
When the value was less than 0.45, the number of dust particles on the product with a diameter of 2 mm or more was 0.2 pieces/m ² , and there were no quality problems. However, when the absorbance is 0.45 or more, the average dust on products with a diameter of 2 mm or more is 0.7
pcs/ ^m2 , which caused a quality problem.

The dust on the product includes things other than pepper, but if the absorbance is 0.45 or higher, 80% of the dust
The above is due to Pituchi, and we were able to almost certainly predict Pituchi failure.

Example 3 At Company A's unbleached kraft paper manufacturing factory, in order to predict and prevent pitch failures, the absorbance of the process water at various points in the papermaking process and the pitch failures occurring in No. 2 press dots in the press process of the paper machine were continuously measured. We conducted extensive analysis and observations. As a result, it was found that as the absorbance increased, the pitch failure of No. 2 Press Doctor occurred more frequently, and when the absorbance was low, the frequency of failure was extremely low.

Next, after this absorbance increased and pitch trouble was recognized on No. 2 press doctor, this No. 2 press doctor was cleaned and an appropriate amount of pitch control agent was added to the appropriate place as shown below. The pitch problem was resolved and good operating conditions were achieved thereafter.

A schematic process diagram of Company A's unbleached kraft paper manufacturing factory is shown in Figure 1. In other words, the wood raw material first undergoes the cooking process.
(1), then washed in the washing step (2), and then retained in the finishing column (3) for about 9 hours, followed by
(4)→Refiner (5)→Chiest (6)→Refuriner
It is manufactured through the process of (7) → Chiest (8) → Paper machine (9).

In the above process, take the pulp slurry at the inlet of the finished tower (10) and pass it through Toyo Paper No. 3. The absorbance of this liquid was measured over time using incident light that had passed through a filter with a wavelength of 420 nm, and the progress was shown in Figure 2.

As a result, when the absorbance is less than 0.15, approximately 10
It was found that pitch failure did not occur at all in the No. 2 press doctor section even after the passage of time. Also
It has been found that between 0.15 and 0.20, pitch failure occurs although the frequency is very low, and when it exceeds 0.20, pitch is almost always attached to the No. 2 press doctor, causing trouble.

At the point of broken line A in Figure 2, the absorbance exceeds 0.20,
Approximately 10 hours later, a pitch failure occurred in the No. 2 press doctor. Clean this and complete the tower outlet section 1.
1. Surfactant type pitch control agent [Miracle Piticon, manufactured by Katayama Chemical Industry Research Institute Co., Ltd.]
500 (polyoxyethylene ether type surfactant)] was added to the pulp at 300 ppm, the pitch problem in the No. 2 press doctor part was resolved one hour after the addition started, and from then on, the pitch problem in the No.
Even though process water with an absorbance exceeding 0.20 was being sent to the machine, the operating conditions were very good. From the results of the above analysis and observation, A
As a method for preventing pit damage, the company has adopted a method in which when the absorbance of process water at the inlet 10 of the finished tower shows a value of 0.20 or more, the pitch control agent is added to the outlet 11 of the finished tower 8 hours later. are doing.

As is clear from the above explanation, the method for preventing pit damage in the pulp or paper manufacturing process of the present invention is capable of preventing the occurrence of pit damage by using a value that can be extremely easily measured, such as the absorbance of passing process water. This is a method of predicting and accurately preventing pitch failures, and can be said to be an extremely effective method in terms of resource conservation and cost reduction.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the unbleached kraft paper manufacturing process of Company A, and FIG. 2 is a graph showing the time course of the absorbance of superwater at the inlet of the completed column in the unbleached kraft paper manufacturing process. 1... Cooking process, 2... Washing process, 3... Finished tower,
4, 6 and 8...Chiest, 5 and 7...Refiner, 9...Paper machine, 10...Completed column inlet section (process water collection point for absorbance measurement), and 11...Pitch control agent addition point.

Claims (1)

[Scope of Claims] 1. In the pulp or paper manufacturing process after the post-cooking washing process, process water is collected from the process before the process where pitch failure occurs, and the pulp, paper stock, etc. contained in the process water are collected. The absorbance of the resulting treated water is measured by irradiating it with visible light with a wavelength of about 420 nm, and based on the measured value, pulp or the like is treated to prevent pitch damage. Method for preventing pitch injury in paper manufacturing process. 2. The method according to claim 1, wherein the pitch injury preventing treatment is carried out by adding a pitch injury preventing agent.