JPS6257759B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for simply and reliably preventing pitch damage that occurs during the pulp or paper manufacturing process. Specifically, in the pulp or paper manufacturing process, process water is collected from the process before the process where pitch failure occurs, and suspended matter such as pulp and paper stock contained in the process water is removed and the resulting treated water is The present invention provides a method for preventing pit damage in a pulp or paper manufacturing process, which comprises measuring chemical oxygen demand and performing pitch damage prevention treatment based on the measured value.

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. can cause various pitch defects such as causing stains or holes in the pulp sheet or paper.

Conventionally, various methods have been adopted 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. When these are added to process water at appropriate points in the pulp and paper manufacturing process, pitches precipitate in the liquid, aggregate into particles of a certain size, and adhere to machinery and equipment, and then detach and form paper. However, this method requires adding the inhibitor only after encountering a disturbance phenomenon that occurs during the operation of the manufacturing process, or The necessity of adding an inhibitor is understood and used based on experience in the process, and pitch damage is not predicted and prevented from the characteristics of the process water in advance.

It is generally said that the major cause of pitch failure is differences in the types of manufacturing raw materials, but differences in manufacturing equipment, processes, or manufacturing conditions may also have a subtle effect on the occurrence of pitch failure. Furthermore, in pulp and paper manufacturing processes that involve multiple steps and take a long time, the phenomenon of occurrence of this disorder is extremely diverse, for example, the location and amount of pitch deposited on equipment and products are not constant. Therefore, although the methods described above are effective in themselves, it is often difficult to take appropriate control measures, and the addition of inhibitors is always based on estimation, so they are sometimes ineffective. Even if there were times when people were consuming large amounts of food when necessary, the current situation was that they ignored 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. Increasing the amount of blowing of contaminated process water is considered 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 work, but also has practical disadvantages because it does not predict failures and deal with them in advance. Don't criticize what is there.

In view of these facts, the present inventors realized that if the occurrence of pitch injury could be known in advance, it would be possible to take effective and appropriate preventive measures. As a result of collecting, inspecting, and analyzing the process water from various pulp and paper manufacturing processes and the pitts generated therein, we found that the color and turbidity of the process water were determined by dissolution and/or We discovered that this is a factor that indicates the amount of pitch component present in an undissolved state, and found that when the color and turbidity reached a certain value or higher, troubles due to pitch were frequent in the actual process. In addition to confirming that there is a tendency toward As a result, the present invention was completed.

The present invention is characterized in that the process water of the pulp or paper manufacturing process is passed through and the COD is measured, and based on the COD value, the occurrence of pitch damage is predicted, and measures for suppressing pitch damage are implemented. This is a method of preventing pitch disorder.

In the pulp or paper manufacturing process, pitch failures often occur in the bleaching process, pulping process, and papermaking process, so the present invention
The process water for COD measurement is collected from the process before the process where the above-mentioned pitch failure occurs, and the COD is measured after passing through this water. After that, it is predicted that a pitch fault will occur, and various pitch fault prevention measures as described below are implemented.

Therefore, the location where the process water for COD measurement is collected is preferably a location that allows sufficient time to take measures to prevent pit damage after measuring COD and prevent such damage from occurring. . for example,
Even if it is possible to predict the occurrence of pitch failure in a subsequent process based on overwatering COD in one 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 COD measurement is collected has at least one hour from when a pitch failure is predicted based on the COD to when the pitch failure 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 chest. Further, 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 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 to do. 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 COD measurement. JIS K-0101 is the method for measuring COD.
Examples include the potassium permanganate method or the potassium dichromate method.

It was found that there was a certain correlation between the COD measured there and pitch disorder. In the field studied by the inventors, for example,
Pitch failure occurred when COD (potassium dichromate method) showed a value of 600 ppm or more. However, differences in pulp and paper raw materials, additives to the process,
Depending on the equipment used, there may be some variation between the magnitude of COD and the occurrence of pitch failure. Such fluctuations can be easily standardized at each factory by keeping the conditions for removing suspended matter constant and referring to the above COD value.

The COD 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 adjustment step.

Preventive treatment can be carried out by the addition of anti- or inhibitory agents for pitch injury (eg, polyphosphates, various surfactants, emulsifiers, talc, kaolin, aluminum sulfate, etc.). Alternatively, a method of washing the process water with clean water or a method of partially blowing the process water may be used. The method of preventive treatment itself may be any method, but depending on the degree of occurrence of pitch injury, i.e.
Appropriate treatment may be selected depending on the size of COD.

On the other hand, by measuring COD, 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 In company B's newspaper manufacturing process, process water was
We conducted long-term analysis and observation of COD, papermaking process, pitch failure occurring in the suction section under the wire and on the blanket. As a result, it was found that as COD increased, pitch injury occurred more frequently, and when COD was lower, the frequency of injury was lower.

Next, when the COD increased and pitch failure was expected, when we added the appropriate amount of Pitch Controlled to the appropriate location in advance as shown below, pitch failure did not occur and good operating conditions continued. did it.

A schematic diagram of Company B's newspaper manufacturing process is shown in Figure 1. Pulp slurry from received Chest 1 is taken and passed through Toyo Paper No. 1. The COD of this liquid was measured using the potassium dichromate method. the result,
When the COD is below 250ppm, pitch failure does not occur, but between 250 and 500ppm, pitch failure occurs although it is rare, and when it exceeds 600ppm, the amount of pitch adhesion on the lower wire suction increases rapidly. In addition, it was found that the blanket became soiled to the extent that it could be visually observed. Figure 2 shows the time course of COD (potassium dichromate method) in receiving chest section 1 of Company B's newspaper manufacturing process. When the COD of the received CHEST 1 exceeded 500 ppm and frequent pitch failures were expected, a surfactant-type pitch control agent [Pichicon-1000, manufactured by Katayama Chemical Industry Research Institute Co., Ltd.] was added to the machine CHEST section 7.
When 1% of the material was added to the pulp, there was no pitch sticking on the lower suction part of the wire 9 and no stains on the blanket.
Since then, the plant has been in good operating condition.

As is clear from the above explanation, the method for preventing pit damage in the pulp or paper manufacturing process of the present invention predicts the occurrence of the problem by using an easily measurable value called COD of the process water that has passed through. However, it is a method that accurately prevents pitch failure without too much or too little, and can be said to be an extremely effective method in terms of saving resources and reducing costs.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of Company B's newspaper manufacturing process, and FIG. 2 is a graph showing the time course of COD (potassium dichromate method) of perhydration in the receiving chest section 1 of the newspaper manufacturing process. 1... Acceptance Chest, 2, 4 and 6... Refineer, 3, 5... Chest, 7... Machine Chest,
8...Head box and 9...Wire.

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. A method for preventing pit damage in a pulp or paper manufacturing process, which comprises removing suspended matter from the water, measuring the chemical oxygen demand of the resulting treated water, and performing pitch damage prevention treatment based on the measured value. . 2. The method according to claim 1, wherein the pitch injury preventing treatment is carried out by adding a pitch injury preventing agent.