JP5556838B2 - Slime control method in pulp and paper manufacturing process - Google Patents

Description

  The present invention relates to a slime control method in a paper pulp manufacturing process, and in particular, in a paper pulp manufacturing process using waste paper as a raw material, in applying an inorganic disinfectant, an effective sterilization is performed by combining appropriate oxidizing agents. It relates to a method for slime control.

  Organic fungicides have been used for many years as slime control agents in paper pulp production. However, since the pulp and paper manufacturing process contains a large amount of various organic substances and reducing substances, the organic bactericides cannot provide an effective bactericidal effect due to redox decomposition with them. , You may not have enough slime control. This is a major problem in the paper pulp manufacturing process using waste paper as a raw material, which is particularly rich in organic matter and may contain reducing substances.

  Examples of organic substances included in the paper pulp manufacturing process include fibers, starch, fatty acids, and various polymers. Examples of reducing substances include sulfides, sulfurous acid, and hyposulfite. Therefore, in order to decompose reducing substances and dissolved organic substances that easily react with organic fungicides, by adding an oxidizing agent such as hypochlorite or chlorite prior to the addition of organic fungicides, There have been proposed methods for preventing decomposition of an organic disinfectant and maintaining a slime control effect in a paper pulp manufacturing process (for example, Patent Documents 1 and 2).

  On the other hand, in recent years, an inorganic fungicide having a higher bactericidal effect than an organic fungicide has been used in the paper pulp manufacturing process. For example, a product compound obtained by diluting and mixing sodium hypochlorite and ammonium bromide and a product compound obtained by diluting and mixing sodium hypochlorite and ammonium sulfate are used as inorganic fungicides. It is coming. However, these inorganic disinfectants, like organic disinfectants, are less effective due to degradation by reaction with reducing substances and dissolved organic matter in the pulp and paper manufacturing process, and are more effective than organic disinfectants. It has become a bigger challenge.

  Then, the method of preventing decomposition | disassembly of an inorganic type germicide is proposed by adding the hypochlorite which is an oxidizing agent prior to addition of such an inorganic type germicide (patent document 3). .

Japanese Patent No. 3216273 Japanese Patent No. 4071959 JP 2009-244108 A

  However, due to the high reactivity of inorganic fungicides, decomposition may be accelerated on the contrary if not combined with an appropriate oxidizing agent. Hypochlorite proposed in Patent Document 3 is sufficient. The inventor's research revealed that no effect was obtained.

  In the pulp and paper manufacturing process using waste paper containing a large amount of reducing substances and dissolved organic substances as a raw material, the present invention prevents the decomposition of inorganic chlorine-based disinfectants by adding an optimum oxidizing agent, and has fewer inorganic disinfectants. It is an object of the present invention to provide a method for slime control by exerting a high bactericidal effect with an added amount of.

  As a result of intensive studies to solve the above problems, the present inventor has obtained hypochlorous acid and / or a salt thereof and an ammonium salt in a paper pulp manufacturing process using waste paper containing a large amount of reducing substances and dissolved organic substances as a raw material. By using chlorous acid and / or its salt as an oxidizing agent for inhibiting decomposition of inorganic fungicides when slime is controlled using inorganic fungicides produced from It discovered that it could suppress effectively.

  The present invention has been achieved on the basis of such findings, and the gist thereof is as follows.

[1] Adding an inorganic disinfectant produced from hypochlorous acid and / or a salt thereof and an ammonium salt and chlorous acid and / or a salt thereof to an aqueous system in a paper pulp manufacturing process using waste paper as a raw material A slime control method in a paper pulp manufacturing process characterized by the above.

[2] The paper pulp according to [1], wherein after adding chlorous acid and / or a salt thereof, an inorganic disinfectant produced from hypochlorous acid and / or a salt thereof and an ammonium salt is added. Slime control method in the manufacturing process.

[3] In [1], the chlorous acid and / or salt thereof is added upstream of the point of addition of the inorganic disinfectant produced from hypochlorous acid and / or salt thereof and ammonium salt in the upstream side of the paper pulp production process. The slime control method in the paper pulp manufacturing process characterized by adding.

  According to the present invention, in a pulp and paper manufacturing process using waste paper containing a large amount of dissolved organic substances and reducing substances as a raw material, an inorganic disinfectant produced from hypochlorous acid and / or a salt thereof and an ammonium salt is added to slime. When controlling, the use of chlorous acid and / or its salt effectively suppresses the decomposition of this inorganic fungicide, and a high bactericidal effect can be obtained with a small amount of inorganic fungicide added. It becomes.

It is a systematic diagram which shows an example of the paper pulp manufacturing process to which this invention is applied. 10 is a graph showing the results of Experimental Example 3.

  The embodiment of the slime control method in the paper pulp manufacturing process of the present invention will be described in detail below.

  In the present invention, it is produced from hypochlorous acid and / or a salt thereof (hereinafter sometimes referred to as “hypochlorous acid (salt)”) and an ammonium salt in a paper pulp manufacturing process using waste paper as a raw material. When slime control is performed by adding an inorganic fungicide, chlorous acid and / or a salt thereof (hereinafter sometimes referred to as “chlorous acid (salt)”) is added in combination, and an inorganic fungicide is added. Suppresses decomposition.

<Inorganic germicide>
Hypochlorous acid (salt) for generating the inorganic disinfectant used in the present invention includes alkali metal salts of hypochlorous acid such as sodium hypochlorite and potassium hypochlorite, calcium hypochlorite, etc. And alkaline earth metal salts of hypochlorous acid. These may be used alone or in combination of two or more.

  On the other hand, examples of ammonium salts include ammonium bromide, ammonium sulfate, and ammonium nitrate. These ammonium salts may also be used individually by 1 type, and may use 2 or more types together.

  In the present invention, these hypochlorous acid (salt) and ammonium salt are mixed to produce an inorganic compound such as chloramine and bromamine, and this is added as an inorganic fungicide to the water system in the paper pulp manufacturing process.

The concentration of each chemical added to the water system in the pulp and paper manufacturing process is not particularly limited because the appropriate amount of addition depends on the amount of organic substances, reducing substance concentration, and number of bacteria contained in the pulp and paper manufacturing process. The amount of residual chlorine in the aqueous system immediately after the addition of chloric acid (salt) and ammonium salt is 0.1 to 10 mg / L asCl ₂ as a measured value of the total chlorine concentration by the DPD method. Is appropriate.

  Hypochlorous acid (salt) and ammonium salt are usually used in a mixture of hypochlorous acid (salt): ammonium salt = 1: 1 to 3 (Molar ratio of Cl and N).

<Chlorous acid (salt)>
Examples of chlorite as an oxidant added to suppress the decomposition of such inorganic disinfectants include alkali metal salts of chlorite such as sodium chlorite and potassium chlorite, and calcium chlorite. Alkaline earth metal salts of chlorous acid such as can be used. These chlorous acid (salts) may be used alone or in combination of two or more.

If the amount of chlorous acid (salt) added is too small, the effect of inhibiting the decomposition of the inorganic fungicide cannot be obtained sufficiently, and if it is too large, no further effect can be obtained, resulting in high drug costs. The amount of chlorous acid (salt) added varies depending on the concentration of dissolved organic substances and reducing substances, but it may be added so that the measured value by the iodine titration method based on JISK0101 is about 0.1 to 50 mg / L asCl _2. preferable.

<Addition method>
In the present invention, the inorganic fungicide and chlorous acid (salt) can be added at the same place in the paper pulp production process, but the desired effect can be obtained. It is preferable to add chlorous acid (salt) prior to the addition of the agent, and in the paper pulp manufacturing process, chlorous acid (salt) may be added upstream of the addition position of the inorganic fungicide. It is preferable because the effect of inhibiting the decomposition of the inorganic fungicide by chlorous acid (salt) is further enhanced.

Below, with reference to drawings, the addition method of these chemical | medical agents is demonstrated.
FIG. 1 is a system diagram showing a high-quality papermaking water system using wastepaper as a raw material. In this papermaking water system, broke, DIP (deinked wastepaper pulp), LBKP (coniferous bleached kraft pulp) and recovered raw materials are used as raw materials. The concentration of each raw material in the broke tank 3, DIP tank 2, and LBKP tank 1 is adjusted by charging water and concentrated water from the recovered water tank 16, and then introduced into the mixing chest 4 and mixed uniformly to form a slurry. And This slurry is sent to the wire part 11 through the machine chest 5, the seed box 6, and the white water from the white water silo 13 through the pump 7, the dust remover 8, the screen 9, and the inlet 10. It dehydrates through the press process in the press part 12, and the dry process in a dry part (not shown). White water obtained by dehydration is received by the white water silo 13. In the wire process and the press process, clean hot water and recovered water from the water tank 18 are sprinkled from a shower nozzle (not shown) in order to keep the wire and felt clean. The water in the water tank 18 is a filtrate obtained by separating the white water that has passed through the wire through the white water silo 13 and the seal pit 14 and collected in the recovery device 15. After being stored in the recovery water tank 16 from the recovery device 15, Some water was sent. The remainder of the recovered water is discharged out of the system through the secondary water tank 17.

For the purpose of slime control of the white water primary circulation system in such a paper manufacturing process, chlorous acid (salt) is added from each pulp raw material between white water silos, hypochlorous acid (salt) and ammonium. The inorganic disinfectant produced from the salt is preferably added between the seed box and the white water silo. More specifically, as shown in FIG. 1, the inorganic germicide from the inorganic water disinfectant generation and addition device 30 is added to the inlet 10 of the white water primary circulation system (between the pump 7 and the white water silo 13) or white water. The chlorous acid (salt) from the chlorous acid (salt) adding device 20 is added to the silo 13, and the upstream DIP tank 2, mixing chest 4 , or machine chest 5 .

As other addition forms, for the purpose of slime control of recovered water, chlorous acid (salt) is added to the white water primary circulation system (between the pump 7 and the white water silo 13), and the inorganic disinfectant is added from the seal pit 14. It may be added between the recovered water tanks 16.
The addition of these drugs may be intermittent or continuous. In the case of intermittent addition, it is preferable to control so that chlorous acid (salt) is added first or simultaneously.

  Hereinafter, the present invention will be described more specifically with reference to experimental examples corresponding to the present invention examples or comparative examples.

The chemicals used in the following experimental examples are sodium chlorite (NaClO ₂ ), sodium hypochlorite (NaClO), and an inorganic disinfectant (mixed product of NaClO and ammonium bromide, NaClO: NH ₄ Br = 1: 1 (molar ratio of Cl to N)).

The residual chlorine concentration was measured by the DPD method (total chlorine), DPD method (free chlorine), and iodine titration method (JIS K0101).
In the DPD method (total chlorine), NaClO and (NaClO + NH ₄ Br) are measured, but NaClO ₂ is not measured.
In the DPD method (free chlorine), only NaClO is measured, and inorganic fungicides (NaClO + NH ₄ Br) and NaClO ₂ are not measured.
In the iodine titration method (JISK0101), all of NaClO, an inorganic fungicide (NaClO + NH ₄ Br), and NaClO ₂ can be measured.
From the above, calculation of each drug concentration in the sample water was performed as follows.
NaClO concentration = Residual chlorine concentration measured by DPD method (free chlorine) Inorganic disinfectant (NaClO + NH ₄ Br) concentration = Residual chlorine concentration measured by DPD method (total chlorine)
-Residual chlorine concentration measured by DPD method (free chlorine) NaClO ₂ concentration = Residual chlorine concentration measured by iodine titration method (JISK0101)
-Residual chlorine concentration measured by DPD method (total chlorine)

[Experiment 1 (Invention)]
An equal amount of each of NaClO ₂ and inorganic fungicide (NaClO + NH ₄ Br) diluted to about 50 mg / LasCl ₂ was mixed. After mixing, the residual chlorine concentration after 15 minutes was measured, and the results are shown in Table 1.

[Experimental example 2 (comparative example)]
The residual chlorine concentration was measured by mixing in the same manner as in Experimental Example 1 except that NaClO was used instead of NaClO ₂ . The results are shown in Table 2.

As is apparent from the results of Experimental Examples 1 and 2, in Experimental Example 2 in which NaClO and an inorganic fungicide (NaOCl + NH ₄ Br) were mixed, both drugs were clearly decomposed, whereas NaClO ₂ In Experimental Example 1 in which an inorganic disinfectant (NaOCl + NH ₄ Br) was mixed, the decomposition of both chemicals was not observed, and chlorous acid (salt) was added instead of hypochlorite to the water system of the paper pulp manufacturing process. By doing so, it can be seen that the decomposition of the paper pulp manufacturing process using waste paper as a raw material can be suppressed.

[Experiment 3]
The bactericidal effect on pulp slurry containing waste paper raw materials was evaluated by the following method.
The concentration of the chemicals shown in Table 3 is as shown in Table 3 with respect to the pulp slurry having a pulp concentration of 3% by weight containing 15% by weight of the deinked waste paper raw material, 75% by weight of LBKP, and 10% by weight of the waste paper raw material. Then, the mixture was allowed to stand at 30 ° C. for 30 minutes. In addition, when using together an oxidizing agent and an inorganic type germicide, these were added simultaneously. The slurry after standing for 30 minutes was mixed with 1/10 pY agar medium, and after standing still at 30 ° C. for 2 days, the number of colonies was counted. The results are shown in Table 3.
FIG. 2 is a graph showing the relationship between the concentration of the inorganic fungicide (NaClO + NH ₄ Br) and the number of bacteria for each oxidizing agent addition concentration.

From Table 3 and FIG. 2, NaClO ₂ and the inorganic germicide (NaClO + NH) are more effective than the case where the inorganic germicide (NaClO + NH ₄ Br) is added alone, or NaClO and the inorganic germicide (NaClO + NH ₄ Br) are used in combination. _In the case of using ₄ Br) in combination, a high bactericidal effect is obtained particularly in a region where the amount of inorganic bactericides added is low, and the effect of inhibiting the decomposition of inorganic bactericides by chlorous acid (salt) is as follows. It turns out that it is superior to chlorite.

DESCRIPTION OF SYMBOLS 1 LBKP tank 2 DIP tank 3 Broke tank 4 Mixing chest 5 Machine chest 6 Type box 7 Pump 8 Dust remover 9 Screen 10 Inlet 11 Wire part 12 Press part 13 White water silo 14 Seal pit 15 Recovery device 16 Recovery water tank 17 Secondary water Tank 18 Water tank 20 Chlorite addition device 30 Production / addition device of inorganic disinfectant by mixing hypochlorite and ammonium salt

Claims (3)

  A feature is that an inorganic disinfectant produced from hypochlorous acid and / or a salt thereof and an ammonium salt, and chlorous acid and / or a salt thereof are added to an aqueous system in a paper pulp manufacturing process using waste paper as a raw material. The slime control method in the paper pulp manufacturing process.   In the paper pulp manufacturing process according to claim 1, wherein after adding chlorous acid and / or a salt thereof, an inorganic disinfectant produced from hypochlorous acid and / or a salt thereof and an ammonium salt is added. Slime control method.   In Claim 1, chlorous acid and / or its salt are added in the upstream of a paper pulp manufacturing process rather than the addition point of the inorganic disinfectant produced | generated from hypochlorous acid and / or its salt, and ammonium salt. A slime control method in a paper pulp manufacturing process characterized by the above.

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