JPH1128474A - Method for evaluating slime generation condition of paper pulp production process and slime control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to promptly change the injection rate of a slime control agent and to execute slime control by passing the white water or pulp slurry of a paper pulp production process to a slime monitor apparatus and evaluating a slime generation from the interelectrode potential difference between an instruction electrode and reference electrode. SOLUTION: The stainless steel electrode 2 of the slime monitor apparatus is formed of SUS 304. The spacing between the front end thereof and the front end of a silver electrode 4 and the spacing between the front end of this silver electrode 4 and the front end of a platinum electrode 6 are respectively specified to 5 mm and 5 mm and the distance between the instruction electrode and the reference electrode is set at 7 cm. The slime control agent is added to an under-wire white water pit and machine chest in a production line for wood pulp paper and part of the white water is branched from the white water circulation line of a neutral paper machine subjected to the slime control and is passed to the slime monitor apparatus. Significant relations are admitted between the potential difference and the number of bacteria in the white water, the number of the specks formed at the produced paper, the number of defects thereof as a result of the transition of the potential difference and the number of bacteria of this time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating the occurrence of slime in white water or pulp slurry in a paper pulp manufacturing process, and performing slime control based on the result.

[0002]

2. Description of the Related Art In a paper pulp production process, a large amount of water and a wide variety of organic chemicals are used, and the temperature is moderate, so that the environment is extremely favorable for the propagation of microorganisms. Some of these microorganisms secrete viscous substances which, together with the solids in the system, form so-called slimes in the form of clumps or sludge. Slime is often
It is generated and adheres to the surface of white water pits, chests, stock inlets, pipes, etc., peels off at this point and mixes with white water or pulp slurry, and when it is taken into paper, paper breaks or spots on paper or pulp It has caused a number of adverse effects such as significantly lowering product quality.

[0003] In order to prevent the generation of slime, various slime control agents have been used. In general, a method for evaluating the state of slime generation during a process or a method for evaluating the effect of a slime control agent is to collect process water, measure the number of bacteria therein, and infer from the results. However, the measurement of the number of bacteria uses a medium,
After the microorganisms are grown for a certain period of time, the number is counted, and the measurement usually takes several days. Therefore, it is not possible to measure and evaluate the situation at the site immediately,
There is a drawback that quick response cannot be taken. Furthermore, in the measurement of the number of bacteria, since the medium to be used differs depending on the target bacteria,
The microflora after cultivation has disadvantages different from those before culturing.

In addition, a suitable test piece is suspended in the process water, and slime is attached to the test piece surface.
A method of measuring and evaluating the amount, a method of measuring the oxidation-reduction potential, and the like have been proposed. Although both methods are simple methods, the method of suspending test pieces is a convenient and convenient method for examining the state of slime adhesion for a certain period, but a large number of test pieces are required for continuous monitoring of the process. Must be immersed, which is not practical. On the other hand, the method of measuring the oxidation-reduction potential can continuously measure the state of generation and adhesion of slime, but it varies greatly depending on the chemical used in the paper pulp manufacturing process more than the change in the amount of slime generated, and it is not accurate. There are missing shortcomings.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to continuously evaluate the state of slime generation in white water or pulp slurry in the paper pulp manufacturing process, and to immediately adjust the injection amount of the slime control agent. It is to provide a method of changing the slime control.

[0006]

The present inventors have found that when slime is formed on the surface of stainless steel, the growth of microorganisms in the slime produces organic acids, resulting in corrosion of the surface of the stainless steel and a small amount of corrosion current flowing through this portion. Attention was paid to the finding that the trace current or the slime generation status can be known, and the present invention has been completed based on this finding.

[0007] That is, the invention of claim 1 includes a stainless steel wire in the form of a net or a coil so as to easily attach slime, or a plate, a pipe or a rod having a large number of grooves or irregularities on the stainless steel surface. A slime monitor device in which stainless steel in a specific form is used as one electrode, which is combined with a silver electrode as an indicator electrode, while a platinum electrode and a silver electrode are combined as a reference electrode, and both electrodes are installed in the same pipe Then, white water or a pulp slurry in the paper pulp manufacturing process is passed through, and the slime generation state in the paper pulp manufacturing process is evaluated from the potential difference between the indicator electrode and the reference electrode.

[0010] According to a second aspect of the present invention, white water or pulp slurry is filled in a pipe in which an indicator electrode and a reference electrode are installed.
2. The liquid is circulated at a linear velocity of 2 to 10 cm / s.
This is a method for evaluating the described slime generation status.

A third aspect of the present invention is characterized in that the potential difference between the indicator electrode and the reference electrode is connected to an injection device for the slime control agent, and the injection amount of the slime control agent is controlled by the potential difference between the electrodes. This is a slime control method in the paper pulp manufacturing process.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

According to the present invention, when process water such as white water or pulp slurry is continuously brought into contact with a metal surface, microorganisms adhere to the metal surface, the attached metal surface becomes an anaerobic atmosphere, and Utilizing the fact that anaerobic microorganisms proliferate and secrete organic acids, so that corrosion progresses on the metal surface and a corrosion current flows. That is, the state of slime adhesion is determined based on the magnitude of the corrosion current.

The slime monitoring apparatus of the present invention divides white water or pulp slurry from a paper pulp manufacturing process, flows the pulp slurry through a pipe provided with an indicator electrode and a reference electrode, and monitors the slime generation status in the process based on the potential difference between the electrodes. So that you can know.

The indicator electrode in the present invention comprises a stainless steel electrode and a silver electrode. The stainless steel electrode is, for example, a stainless wire formed into a net shape, a coil shape, or a plate shape having a large number of grooves or irregularities on the stainless steel surface, a pipe shape, a rod shape, or the like so as to easily attach the slime. . The size of the mesh, the shape of the grooves or irregularities on the surface of the coil or the surface, the degree of the irregularities is not particularly limited,
For example, as the mesh-like thing, a stainless steel mesh is formed into a cylindrical shape or a plate-like shape, and preferably has a fineness of 20 mesh or more, more preferably 40 to 200 mesh, more preferably 60 to 150 mesh.
Examples of the coil-shaped coil include a coil in which a stainless steel wire having a diameter of 0.1 to 1 mm is densely wound around any rod, pipe, or cylinder such as stainless steel, glass, or acrylic. In the case of a plate, pipe, or rod, the surface is roughly processed. In the case of a rod, the surface is preferably about 0.1 to 5.0 mm, more preferably 0.5 to 2.
There is a method in which fine threads are cut at a pitch of 0 mm to form irregularities. It is not necessary that the surface of the stainless steel electrode is roughened so that the slime can be easily attached to the entire surface of the stainless steel electrode, and a part of the stainless steel electrode is sufficient.

The size of the stainless steel electrode in the present invention is not particularly limited as long as the stainless steel electrode in the pipe does not cause a non-uniform flow in the pipe. For example, in the case of rod-shaped, the length in diameter 3 to 10 cm 5
In the case of a net, it is preferable that a net having a size of 5 to 15 cm × 5 to 15 cm is rounded into a cylindrical shape.

The material of stainless steel used in the present invention is S
US-201, SUS-302, SUS-304, SU
S-316, SUS-317, etc., from the viewpoint of price, processability, and availability, SUS-304, SUS-3
16 is preferred.

As the silver electrode in the indicator electrode of the present invention, a commercially available silver electrode can be used. For example, "TYP" manufactured by Toa Denpa Kogyo KK
E HA-101 ".

The reference electrode in the present invention is a combination of a silver electrode and a platinum electrode. The silver electrode and the platinum electrode can each be a commercially available one, the silver electrode may be the same as that used for the indicator electrode, and the platinum electrode is, for example, Toa Denpa Kogyo Co., Ltd.
Manufactured by TYPE HP-105.

As the electrode used as the reference electrode, a silver / silver chloride electrode, a hydrogen electrode, a sweet kou electrode, a mercuric sulfate electrode, a mercury oxide electrode, and the like can be used. The combination of silver electrodes is most suitable.

FIG. 1 is a schematic view illustrating a slime monitoring device, in which an indicator electrode combining a stainless steel electrode (2) and a silver electrode (4) and a reference electrode combining a silver electrode (5) and a platinum electrode (6). The electrode is an acrylic inverted L in the same pipe.
It is set in a cylindrical pipe (7). The ends of the liquid inlet (1) and the outlet (8) of the liquid to be measured of the pipe (7) form a flange (9).

The stainless steel electrode (2) is installed by removing white water or pulp slurry in a cylindrical pipe (7) (outer diameter: 50 mm, wall thickness: 3 mm, length: 400 mm) from the liquid inlet (1) to be measured. It is preferable to mount the pipe in parallel with the pipe axis along the flow, and there is no particular limitation as long as care is taken not to cause non-uniformity in the flow in the pipe. The silver electrode (4) constituting the indicator electrode is inserted perpendicular to the pipe, and the interval between the surface of the stainless electrode slime attachment portion (3) and the tip of the silver electrode (4) is set to about 2 to 5 mm.

As shown in FIG. 1, the silver electrode (5) and the platinum electrode (6) as the reference electrodes are installed so that both of them are pierced vertically from the surface of the pipe by the pipe axis method. They are installed such that their tips are separated from each other by about 2 to 10 mm.

The distance between the indicator electrode and the reference electrode is not particularly limited as long as the distance is within the same water system.
cm or less, preferably 15 to 2 cm. If the distance is larger than this, the sensitivity becomes dull, which is not preferable for practical use. If it is 1 cm or less, clogging of the pulp slurry increases, which is not practical.

The diameter of the pipe used in the slime monitoring device of the present invention is not particularly limited. However, in order to avoid stagnation in the pipe and generation and accumulation of sediment, the diameter is 3 to 10 c.
m is preferred. It is preferable to use a transparent pipe so that the electrodes can be observed from the outside of the pipe. However, when an opaque pipe is used, an observation window is provided in the electrode section so that the situation inside can be observed. If solid matter such as pulp adheres to the electrode part, remove it with a small brush or the like. For this cleaning, it is preferable to provide a screw-in window ((10) in FIG. 1) for cleaning around the electrode portion. The material of the pipe to be used is not particularly limited, such as stainless steel, glass, vinyl chloride, and acrylic.
Acrylic is preferably used because of its strength and easy observation from the outside.

The flow rate of the white water or the pulp slurry flowing into the pipe of the slime monitor of the present invention is 0.05 to 15 cm / sec in linear velocity, preferably 0.2 to 15 cm / sec.
It is 10 cm / sec, more preferably 0.5 to 5 cm / sec. At a linear velocity of 5 cm / sec or less, white water or solid matter in the pulp slurry adheres to the electrode, and an accurate measured value cannot be obtained. On the other hand, if the linear velocity is 15 cm / sec or more, the slime adhered to the stainless steel electrode may be peeled off by the inflow water, so that long-term monitoring cannot be performed, which is not preferable.

The pulp slurry flowing into the slime monitor has a pulp concentration of 1.0% by weight or less, preferably 0.1% by weight or less.
It is preferably at most 5% by weight. If it exceeds 1.0% by weight, the electrode will be clogged with pulp, making accurate measurement impossible.

In the slime monitor of the present invention,
The direction of the flow of the white water or pulp slurry may be either the horizontal direction or the vertical direction, but in order to avoid accumulation of air that has entered, the installation portion of the electrode is inclined at 5 to 45 degrees with respect to the vertical direction. May be preferred.
If air accumulates in the electrode portion, the potential will not be stable, and the slime monitor will lack reliability.

In the present invention, the reading of the potential difference between the reference electrode and the indicator electrode may be performed by using an electrometer corresponding to the potential difference, and is not particularly limited. In a normal case, the potential difference is +500 mV to -500 mV. is there.

In another embodiment of the present invention, the injection amount of the slime control agent is reduced by connecting the potential difference between the indicator electrode and the reference electrode in the slime monitor device and the injection amount of the slime control agent. It is to control.

The potential difference between the indicator electrode and the reference electrode in the slime monitor of the present invention is that slime is generated in the system, and when slime adheres to the stainless steel electrode, a current flows and the potential difference increases. Therefore, injection of the slime control agent is performed when the potential difference becomes greater than or equal to a preset value, and injection control of the slime control agent by stopping the injection of the slime control agent when the potential difference becomes less than or equal to the set value. The injection amount of the slime control agent can be controlled in proportion to the value. The injection amount of the slime control agent is empirically determined in consideration of the type of the slime control agent used, the state of the process, and the like.

The white water or pulp slurry introduced into the slime monitoring device is white water or pulp slurry at a location where slime trouble occurs, such as machine white water, wire pit white water, or stock inlet slurry. These are made into a bypass and introduced into a monitoring device, and the change over time in the potential difference between the indicator electrode and the reference electrode is recorded on a recorder. The potential difference when no slime adheres depends on the individual paper machine, white water, and pulp slurry, and cannot be unconditionally determined. However, the potential difference when the slime monitoring device is operated: V
When o = (indicating electrode potential)-(reference electrode potential) is used as a reference, slime adheres to the stainless steel electrode by flowing white water and pulp slurry, and a corrosive current is generated by the growth of microorganisms. The electrode potential V1 starts to gradually increase. V1 is about 50 to 10 more than Vo
It becomes 0 mV or more. At this time, it is determined that there is a high risk of slime trouble, and it is necessary to add a slime control agent or switch to a more effective slime control agent. Here, when the slam control agent is added or changed to a more effective agent, V
1 indicates that the value rapidly decreased to a value close to Vo and slime was suppressed. When the decrease in V1 is small, it indicates that the growth of the slime, which tends to proliferate, could not be suppressed or sterilization could not be performed even when the drug was added.

[0031]

The present invention will be described in detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.

In the slime monitoring device used in the examples, the stainless steel electrode (2) in FIG. 1 was 1.3 cm in diameter, 18 cm in length, and was threaded at a pitch of 1 mm up to 5 cm from the tip. SU in form
S-304, the silver electrode (4) and the platinum electrode (6) were respectively “TYPE HA-101” manufactured by Toa Denpa Kogyo Co., Ltd.
"TYPE HP-105" was used. Spacing between tip of stainless steel electrode (2) and tip of silver electrode (4) and silver electrode
The distance between the tip of (4) and the tip of the platinum electrode (6) was 5 mm and 5 mm, respectively, and the distance between the indicator electrode and the reference electrode was 7 cm.

Example 1 In a medium paper production line with a production volume of 300 tons / day, a slime control agent was added to a white water pit and a machine test under a wire to control slime control in a neutral paper machine. Part of the white water was branched off from the circulation line and flowed at a linear velocity of 5 cm / sec into the slime monitor described above. At this time, the potential difference (m
v) and changes in the number of bacteria (cells / ml) are shown in FIG.
FIG. 3 shows changes in v) and the number of spots on paper and the number of defects (pieces / day).

As a result, a large correlation was found between the potential difference of the slime monitor of the present invention, the number of bacteria in the white water, and the number of formed spots and defects on the manufactured paper. It was shown that the situation could be fully understood.

[0035]

As described above, according to the present invention, it is possible to continuously evaluate the occurrence of slime in white water or pulp slurry in the paper pulp manufacturing process.
In addition, by connecting the instruction of the slime monitoring device and the device for controlling the injection amount of the slime control agent, the slime control in this step becomes extremely easy and reliable.

[Brief description of the drawings]

FIG. 1 is a drawing illustrating a slime monitor device.

FIG. 2 is a drawing showing changes in the potential difference of the slime monitor device and the number of bacteria in white water.

FIG. 3 is a drawing showing changes in the potential difference of the slime monitor device and the number of spots on paper and the number of defects.

[Explanation of symbols]

(1) Inflow port of liquid to be measured (2) Stainless steel electrode constituting indicator electrode (3) Stainless steel electrode slime attachment part constituting indicator electrode (4) Silver electrode constituting indicator electrode (5) Silver constituting reference electrode Electrode (6) Platinum electrode constituting reference electrode (7) Acrylic cylinder (outer diameter: 50 mm, wall thickness: 3 m)
(8) Measuring liquid outlet (9) Flange (10) Window for cleaning

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Hideki Takahashi 1727-1 Nakasone-cho, Iyo-Mishima-shi, Ehime Prefecture Hakuto Shikoku Sales Office

Claims (3)

[Claims] 1. A stainless steel wire having a mesh shape or a coil shape so as to easily attach slime, or a stainless steel wire having a suitable shape including a plate shape, a pipe shape, and a rod shape having a large number of grooves and irregularities on the surface of the stainless steel. One electrode,
This is combined with a silver electrode to form an indicator electrode, while a platinum electrode and a silver electrode are combined to form a reference electrode, and a slime monitor device in which these two electrodes are installed in the same pipe is used for white water or pulp slurry in the paper pulp manufacturing process. And evaluating the slime generation status in the paper pulp manufacturing process from the potential difference between the indicator electrode and the reference electrode. 2. The inside of a pipe in which an indicator electrode and a reference electrode are installed is filled with white water or pulp slurry at a rate of 0.2 to 10 cm / s.
The method for evaluating a slime generation state according to claim 1, wherein the slime is distributed at a linear velocity of: 3. The method according to claim 1 or 2, wherein the potential difference between the indicator electrode and the reference electrode is connected to a slime control agent injection device so that the injection amount of the slime control agent is controlled by the potential difference between the electrodes. A slime control method for the paper pulp manufacturing process, which is a feature.