JPH05302284A - Method for cleaning unbleached kraft pulp - Google Patents

Abstract

PURPOSE:To improve degree of cleaning of pulp without excessively increasing the amount of washing water by cleaning unbleached kraft pulp under a specific condition. CONSTITUTION:A pulp slurry is mixed with 10-1,000ppm, preferably 50-800ppm based on oven-dry weight of pulp of a surfactant of the formula (n1 is 8-12; n2 is 6-12) and cleaned. Polyoxyethylene octylphenyl ether, polyoxyethylene nonylphenyl ether or polyoxyethylene dodecylphenyl ether is preferable as the surfactant.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for washing unbleached kraft pulp. More specifically, the present invention relates to a method for washing unbleached kraft pulp that can be efficiently washed without impairing the quality of pulp.

[0002]

2. Description of the Related Art Wood chips are cooked with a kraft cooking liquor to efficiently remove water-soluble substances from cooked pulp and to recover them. It is extremely important in reducing the emission of pollutant load on the system.

If the unbleached pulp is not sufficiently washed,
In addition to the above, it causes foaming troubles and pitch troubles in the multi-stage bleaching process, the selection process, and the papermaking process, which causes unstable operation, and the pitch itself exhibits brown or black color, and is mixed in the final product paper as foreign matter. It significantly reduces the quality of the paper.

In order to sufficiently wash the unbleached pulp, a multi-stage countercurrent washing system has been conventionally used, which includes washing in a kettle of a continuous digester, continuous diffuser washing, drum washing and the like.

The pulp obtained after cooking wood chips with a continuous digester is subjected to high-heat countercurrent washing in a kettle, or to a digester having no high-heat washing zone, pressure type and / or normal type without undergoing in-kettle washing. In a pressure-type diffusion washer, replacement washing is performed under a closed pulp concentration of 10%, and then plastic pieces, metal pieces, coarse foreign matters such as stones, undigested knots, binding fibers, sand and coarse pitch mixed in the pulp are removed. It is sent to a selective process consisting of a knotter for removing fine foreign substances, a flat screen, a centrifugal screen, an overflow screen, and various dehydrators for processing. The selected pulp is dehydrated to a pulp concentration of 10% by a drum filter, and delignified by a known oxygen bleaching process using oxygen and alkali with or without passing through a pulp storage tank,
Finally, it is again deliquored by a drum filter to a pulp concentration of about 10%, stored in a high concentration tank, and sent from there to a multi-stage bleaching process as required.

In some plants, after passing through a knotter, pulp is deliquored by a drum filter, immediately subjected to oxygen bleaching treatment using oxygen and alkali, washed again by a drum filter and deliquored, and then passed through a pulp storage tank. Alternatively, it is sent to the selective process without treatment, treated, then deliquored and sent to a high-concentration tank, and from there, if necessary, sent to a multi-stage bleaching process for use.

Thus, even if there is a difference that the pulp is carefully selected before or after the oxygen bleaching, or even if the oxygen bleaching is not performed, the good or bad of the cleaning of the pulp (the index of the cleaning degree) Is represented by the degree of fouling that accompanies the pulp introduced into the multistage bleaching process, which is the final stage of washing, that is, the diffusion washer or the outlet pulp and its filtrate of the additional dewatering stage, oxygen. When bleaching is performed, it is necessary to monitor the degree of soiling of the pulp and its filtrate at the outlet of the one-stage deliquoring process performed after oxygen bleaching.

[0008] Thus, one of the indicators of the quality of cleaning the pulp is that a substance generally called a solid substance composed of an organic substance and an inorganic substance which flows into the washing system together with the unbleached pulp is
It is represented by a numerical value indicating how much is adhered to the pulp without being separated, and such a numerical value is measured by deliquoring the pulp and specifically analyzing the separated liquid. or,
Although it is indirect, since the filtrate also has a tendency similar to that of the liquid contained in the pulp, the numerical value can be measured even by specifically analyzing the filtrate at various places. It is said that the smaller these values are, the more sufficient the cleaning is performed.However, if the values are large, the amount of warm water used as the cleaning water in the final stage is increased to perform the cleaning. It is being strengthened.

[0009]

However, as the amount of hot water used increases, the amount of liquid to be treated in the chemical recovery process increases, which exceeds the evaporation capacity of a multi-effect vacuum evaporator or the like, resulting in a reduction in production of unbleached kraft pulp. In addition, the amount of steam used for evaporation increases, resulting in an increase in cost. It is not preferable to excessively increase the amount of hot water used for strengthening the washing of the pulp, because it causes adverse effects in other aspects.

For this reason, conventionally, a multistage washing method has been adopted in which a limited amount of warm water is used as washing water and a plural-stage washing device for efficiently washing pulp is introduced. It is difficult to say that it is a very preferable method because it is expensive and has a large installation area.

Therefore, an object of the present invention is to provide a new and improved method for cleaning unbleached kraft pulp which can improve the cleaning degree of pulp without excessively increasing the amount of cleaning water used. Especially.

[0012]

Means for Solving the Problems As a result of intensive studies on the cleaning device and the amount of cleaning water, chemicals having an effect on the cleaning degree of pulp and cleaning degree of pulp, and addition place,
The following chemical formula (1) The surfactant represented by has an effect on washing pulp,
The present invention has been completed based on the finding that the washing degree of pulp can be improved and the amount of washing water can be reduced by adding the surfactant to the pulp slurry to wash the pulp.

That is, according to the present invention, the surfactant of the chemical formula (1) is added to the pulp slurry in an amount of 10 to 1 per 100 wt.
It is a method for washing unbleached kraft pulp, which comprises adding 000 ppm and washing.

[0014] As the surfactant of the formula used in the present invention (1), such as polyoxyethylene octylphenyl ether n ₁ is 8, n ₂ is 10, n ₁ is 9, n ₂
Is 10 polyoxyethylene nonyl phenyl ether,
Polyoxyethylene dodecyl phenyl ether in which n ₁ is 12 and n ₂ is 12 is preferably used. Where n ₁
If it is less than 8, the performance as a surfactant is significantly reduced, and if it exceeds 12 and the lipophilic group is large, the solubility in water is reduced and the viscosity of the aqueous solution when dissolved in water is increased. Deficiency occurs. On the other hand, when n ₂ is less than 6, the solubility in water decreases, and when it exceeds 12, the detergency decreases.

The amount of these surfactants added to the pulp slurry is 10 to 1000 ppm based on the weight of absolutely dry pulp,
Preferably, the added amount is 50 to 800 ppm. 10
If it is less than ppm, no clear addition effect is observed, and 1000 p
Even if added in excess of pm, the effect is not different and the chemicals are wasted.

When carrying out the method of the present invention, the place to add the chemicals should be before the treatment with the washing machine due to the nature of the chemicals, and at the place where the chemicals can be uniformly mixed with the pulp slurry. If it is added, it does not matter where it is added. For example, a suction port of a pump for sending the pulp slurry to the washing machine is suitable.

The washing machine used for washing includes a drum type filter, a diffuser, a pressure type diffuser, a pressure type drum filter and the like, and any type conventionally used as a washing machine for pulp slurry is used. it can. Further, the effect of the present invention is not different whether the shower used in the washing machine is hot water or a liquid containing a waste liquid obtained by the alkaline digestion method. Furthermore, the effect of the present invention does not change depending on the amount of organic and inorganic components contained in the pulp slurry.

[0018]

EXAMPLES The present invention will be described more specifically below with reference to examples and comparative examples, but the present invention is not limited to the examples. The cleaning test method and the cleaning degree measuring method used in Examples and Comparative Examples are as follows.

Washing test method : Using a drum type filter (hereinafter referred to as a filter) having a cylinder wound with 40 mesh stainless wire having a diameter of 3500 mm and a length of 6000 mm (hereinafter referred to as a filter), unbleached kraft pulp of hardwood and unbleached kraft pulp of hardwood Processing amount 370 air dry tons /
Washing was performed on a fixed day. The cleanliness of the filter inlet during treatment of unbleached softwood kraft pulp is 6 to 7, and the cleanliness of the filter inlet during treatment of unbleached hardwood kraft pulp is 5.
It was ~ 6. Further, the pulp sheet concentration after dewatering was 12 to 12.2% for the unbleached kraft pulp of softwood and 15 to 15.2% for the unbleached kraft pulp of hardwood. The surfactant was added at the inlet of the filter feed pump to thoroughly mix the pulp slurry and the surfactant. Warm water is used as the wash water, and the wash water amount is 8.9 tons per ton of pulp for unbleached softwood kraft pulp and 7.2 per ton of dry pulp for unbleached hardwood kraft pulp.
Used tons.

Washing degree measuring method : The washing degree of unbleached kraft pulp is 30% by hand squeezing the pulp-associated liquid after washing.
ml, and add 670 ml of pure water adjusted to 25 ° C,
Furthermore, 25 ml of 1/10 normal KMnO ₄ and 4 normal H ₂
Add 25 ml of SO ₄ and react for 5 minutes with stirring,
After 10 ml of 1N KI was added to stop the reaction, the consumption amount of potassium permanganate was titrated with 1 / 10N Na ₂ S ₂ O ₃ using a starch indicator. In this example,
Based on the drop constant ml of 1 / 10N Na ₂ S ₂ O ₃ , the unreacted potassium permanganate remaining in the liquid was known, and conversely, the consumed potassium permanganate (ie The reacted organic matter) was measured, and the consumption amount of potassium permanganate (ml) was defined as the degree of cleaning (ml). The higher the number of ml of potassium permanganate, that is, the higher the number of ml of cleaning degree,
The degree of cleaning is poor. It should be noted that both the example and the comparative example were 4 for 2 days.
The cleaning degree was indicated by an average value of 12 points performed every hour.

Example 1 A cleaning test was conducted by using a surfactant of the chemical formula (1) in which n ₁ = 8 and n ₂ = 6, and adding 70 ppm to the unbleached kraft pulp of softwood based on the weight of absolutely dry pulp. I went.

Example 2 The same surfactant as that used in Example 1 was used, and this was added to unbleached kraft pulp of broad-leaved tree at 700 p / wt of dry pulp.
A cleaning test was performed by adding pm.

Example 3 A cleaning test was conducted in the same manner as in Example 1 except that the surfactant of the chemical formula (1) in which n ₁ = 8 and n ₂ = 10 was used.

Example 4 A washing test was conducted in the same manner as in Example 2 except that the surfactant of the chemical formula (1) in which n ₁ = 8 and n ₂ = 10 was used.

Example 5 A surfactant of the chemical formula (1) in which n ₁ = 9 and n ₂ = 6 was used, and this was added to the unbleached softwood kraft pulp in an amount of 700 ppm based on the weight of the absolutely dried pulp to perform a washing test. I went.

Example 6 The same surfactant as that used in Example 5 was used, and this was added to unhardened kraft pulp of hardwood 700 p / p of dry dry pulp.
A cleaning test was performed by adding pm.

Example 7 A washing test was conducted in the same manner as in Example 5 except that the surfactant of the chemical formula (1) in which n ₁ = 12 and n ₂ = 10 was used.

Example 8 A washing test was conducted in the same manner as in Example 6 except that the surfactant of the chemical formula (1) in which n ₁ = 12 and n ₂ = 12 was used.

Comparative Example 1 A detergent of the chemical formula (1) in which n ₁ = 8 and n ₂ = 10 was used, and this was added to unbleached softwood kraft pulp at a concentration of 5 ppm based on the weight of absolutely dry pulp to perform a cleaning test. I went.

Comparative Example 2 A surfactant of the chemical formula (1) in which n ₁ = 9 and n ₂ = 5 was used, and 700 ppm was added to unbleached kraft pulp of softwood per 100 wt.% Of dry pulp. Due to poor solubility of the surfactant, the washing test was stopped due to a decrease in dehydration of the filter.

Comparative Example 3 A detergent of the chemical formula (1) in which n ₁ = 8 and n ₂ = 15 was used, and 700 ppm was added to unbleached kraft pulp of softwood per 100 wt. I went.

Comparative Example 4 The same surfactant as in Comparative Example 1 was used, and this was used in an amount of 1300 per 100% by weight of absolutely dry pulp to unbleached softwood kraft pulp.
A cleaning test was conducted by adding ppm.

Comparative Example 5 Polyoxyethylene higher fatty acid ester, which is a nonionic surfactant different from the surfactant used in the present invention, was used, and this was added to unbleached softwood kraft pulp at 700 ppm per absolute dry pulp weight. A cleaning test was conducted by adding the additives.

Comparative Example 6 Sodium alkylbenzene sulfonate, which is an anionic surfactant different from the surfactant used in the present invention, was used, and 700 ppm of this was added to unbleached kraft pulp of hardwood per 100 wt.% Of dry pulp. And a cleaning test was performed.

Comparative Example 7 An alkyl quaternary ammonium salt, which is a cationic surfactant different from the surfactant used in the present invention, was used, and this was added to the unbleached softwood kraft pulp in an amount of 700 ppm per absolute dry pulp weight. Then, a cleaning test was performed.

Comparative Example 8 Softwood unbleached kraft pulp was washed without adding a surfactant.

Comparative Example 9 Hardwood unbleached kraft pulp was washed without adding a surfactant.

Table 1 shows the results of measuring the degree of cleaning of the pulp-associated liquid obtained in Examples 1 to 8 and Comparative Examples 1 to 9.

[0039]

As can be seen from Table 1, the effect of the addition of the surfactant was clearly recognized in the types and the amounts of the surfactants according to the method of the present invention shown in Examples 1 to 8.

On the other hand, even when the surfactant used in the present invention is added in an amount less than the range of the present invention (Comparative Example 1), the cleaning index is high (the higher the cleaning index, the higher the cleaning index). When the n ₂ is smaller than the range of the surfactant used in the present invention (Comparative Example 2), the solubility in water is poor and the cleaning degree cannot be measured, and n ₂ is the interface used in the present invention. 70 if greater than the active agent range (Comparative Example 3)
Despite the large addition amount of 0 ppm, the index of the cleaning degree does not decrease, and the surfactant used in the present invention is 1300 pp.
Even if added in a large amount as m (Comparative Example 4), no improvement in the cleaning effect was observed. Furthermore, even if another type of surfactant having a structure different from that of the surfactant used in the present invention is used (Comparative Examples 5 to 7), the index of cleanliness does not decrease.

[0042]

As described above, according to the present invention, by adding a specific type of surfactant to a pulp slurry in an addition amount within a specific range and washing it, it is possible to further improve the efficiency of unbleached kraft pulp. Good cleaning can be applied.

Front page continuation (72) Inventor Ryuji Ouchi 1 Ojimachi, Kasugai City, Aichi Prefecture Kasugai Mill, Oji Paper Co., Ltd. Inside Nagoya Branch Co., Ltd. (72) Inventor Goro Wada 21-2 Tsubakicho, Nakamura-ku, Aichi Prefecture Nagoya City Taiho Industry Co., Ltd. Nagoya Branch

Claims (1)

[Claims] 1. The following chemical formula (1) 10. A method for cleaning unbleached kraft pulp, which comprises adding 10 to 1000 ppm of the surfactant of claim 1 to a pulp slurry based on the weight of absolutely dry pulp and cleaning.