ES2716891T3 - Slime control method - Google Patents

Description

DESCRIPTION

Slime control method

[Technical field]

The present invention relates to a method of controlling silt in a white water circulation line in a papermaking process.

[Antecedent technique]

Currently, paper is made by making paper from a suspension of material prepared by dispersing a paste material in water. In this process, a large amount of white water containing fine fibers and a load of papermaking machinery and the like are discharged. Although white water has been used through circulation in the papermaking process in view of the efficient use and recycling of water resources, white water contains organic substances, such as starch, sizing agents, latex and casein in a large quantity; therefore, a suitable condition for the propagation of microorganisms, such as bacteria and fungi, can be provided. Therefore, it is likely that slime derived from microorganisms will be generated in a circulating water line, as well as on the surface of the pipes and the surface of the equipment. Through the contamination in the product, the silt leads to the deterioration of the quality of the product and the efficiency of the production. Since the fine fibers, starch and the like mentioned above are concentrated in the white water circulation line during the operation, a part of the white water is discarded while fresh water is introduced into it. However, it is impossible to cope satisfactorily with the disadvantageous aspects described above by means of such an exchange of white water.

In order to solve the problems described above, an antimicrobial method was developed, in which a slime control agent, such as an organic antimicrobial agent, is added to the white water circulation line (see the application publication of Unexamined Japanese Patent No. 2003-164882). However, after the decomposition of organic substances, the number of microorganism cells increases and reducing substances, such as hydrogen sulfide and mercaptan, are generated in a large amount. On the other hand, since many of the slime control agents are oxidizing agents, they can react with the sulfite ions derived from reducing substances before reacting with the microorganisms, which leads, in this way, to the consumption of a large amount. quantity of them before achieving the desired antimicrobial effect. Therefore, in order to sufficiently control the generation of silt, the addition of a large amount of the slime control agent is required, including the amount of the slime control agent consumed by the reaction with the ions. of sulfite. In addition, the slime control agent is also comparatively expensive and, therefore, the provision of a more effective slime control method and a reduction in the amount used thereof has been desired.

[Prior art documents]

[Patent documents]

Patent Document 1: Japanese Unexamined Patent Application Publication No. 2003-164882

[Summary of the invention]

[PROBLEMS TO BE RESOLVED WITH THE INVENTION]

The present invention was made in view of the above disadvantages and an object of the invention is to provide an effective slime control method in a white water circulation line in a papermaking process.

[MEANS TO RESOLVE THE PROBLEMS]

In order to solve the above problems, the present inventors have thoroughly investigated and, consequently, found that silt generation can be effectively controlled by: aeration of a white water circulation line or a feed line of water for supplying water to the white water circulation line (hereinafter, may also be referred to as "water supply line" or simply "water line") with a gas containing oxygen; and then the addition of a slime control agent to the white water circulation line or the aerated water feed line with the oxygen-containing gas. Accordingly, the present invention was developed.

According to one aspect of the invention that is made to solve the above-mentioned problems, a slime control method in a white water circulation line in a papermaking process includes the steps of: aerating with a gas containing oxygen either one or both of the white water circulation line and the water feed line for the water supply to the white water circulation line; and add a slime control agent to at least one line of the white water circulation line and the aerated water feed line to the oxygen containing gas in the aeration stage.

Through aeration with a gas containing oxygen from either or both of a white water circulation line and a water feed line for the water supply to the white water circulation line in the aeration stage , the slime control method allows a significant decrease in the amount of the slime control agent added to the line aerated with the oxygen-containing gas to be achieved. It is assumed that the basis of the advantage results from a reduction of the concentration of sulfite ions in the white water circulation line and the like, through the oxidation of the reducing substances by oxygen in the oxygen-containing gas, and a decrease in the solubility of the reducing substances, such as hydrogen sulfide, which would result from the dissolution of a large amount of the oxygen-containing gas in the white water circulation line.

It is preferred that the slime control method includes, in addition, the measurement step of at least one selected from the group of measurement elements consisting of the oxidation-reduction potential, the concentration of sulfite ions and the amount of dissolved oxygen in the white water circulation line and that the rate of aeration in the aeration step and / or the amount of the slime control agent added in the addition step of the slime control agent are regulated, based on the measurement results obtained in the measurement stage. By regulating the rate of aeration and / or the amount of the added slime control agent, the generation of the slime can be controlled in a more secure and more accurate manner.

It is preferred that the aeration rate in the aeration step and / or the amount of the slime control agent added in the addition step of the slime control agent be regulated in such a way that, in the circulation line white water: the oxidation-reduction potential is not less than -150 mV; the concentration of sulphite ions is not greater than 2.0 mg SO3- / l; and / or the amount of dissolved oxygen is not less than 1 mg / l. Slime generation can be controlled more effectively by such adjustment.

It is preferred that an aeration tank having a diffuser tube is used on the lower part thereof for aeration in the aeration stage and that the aeration velocity by the diffuser tube with respect to 1 m2 of the lower unit area of the tank of aeration is not less than 0.5 m3 / hour and is not greater than 10 m3 / hour. By thus adjusting the aeration rate, the decrease in the amount of the slime control agent can also be facilitated.

[Effects of the invention]

According to the present invention, an effective slime control method can be provided in a white water circulation line in a papermaking process. In addition, a decrease in the amount of the used slime control agent is also allowed.

[Brief description of the drawings]

FIG. 1 shows a view illustrating an embodiment of the papermaking process according to the present invention.

[Description of the realizations]

Slime control method

The slime control method is a method of slime control in a white water circulation line in a papermaking process, including the method of: aerating with an oxygen-containing gas either one or both of the white water circulation line and water supply line for water supply to the white water circulation line; and adding a slime control agent to at least one line of the white water from the circulation line and the aerated water supply line with the oxygen-containing gas in the aeration stage.

Furthermore, it is preferred that the slime control method includes, in addition, the measurement step of at least one selected from the group of measurement elements consisting of the oxidation-reduction potential, the concentration of sulfite ions and the amount of dissolved oxygen in the white water circulation line.

Hereinafter, the slime control method will be described in detail.

White water circulation line

The slime control method is used in the white water circulation line in the papermaking process. As referred to herein, the term "white water" means an aqueous solution discharged into a large amount of papermaking machinery and the like in a papermaking process for papermaking. White water contains: fine fibers derived from a paste of raw material used, in general, in the manufacture of paper; another agent for the manufacture of paper; and similar. The term "white water circulation line", as referenced, means the stream line of the white water used through circulation in a papermaking process. The expression "water feed line for water supply to the white water circulation line", as referenced, means a water line for use in adjusting the concentration and the like of the pulp suspension. and / or the white water in the white water circulation line. Although the water line is not particularly limited, for example, soft water, hard water and the like may be involved for use in papermaking and a small amount of any papermaking agent may also be contained within the production line. a range that does not lead to a deterioration of the effects of the present invention. In addition, the white water circulation line can pass through a solid-liquid separator and the separated solid content can be discharged off-line or recovered in the material system.

The pulp of raw material used for papermaking is not particularly limited and is exemplified by chemical pulps, such as a bleached kraft pulp of hardwood (hardwood) (LBKP), a bleached kraft pulp of softwood (from coniferous) (NBKP in English), an unbleached kraft pulp of hardwoods (LUKP in English) and an unbleached Kraft pulp of coniferous (NUKP in English), mechanical wood pulps, such as a crushed paste (GP in English), a thermomechanical wood pulp (TMP), a quimicotermomechanical wood pulp (CTMP) and a mechanical refining wood pulp (RMP), waste paper pulps recycled from scrap cardboard paper, scrap coating paper, waste magazine paper, scrap newspaper, scrap chi-ken-shi paper, etc., high-quality scrap white paper pulp, de-inked pulp and the like.

Also, the papermaking agent is not particularly limited and is exemplified by a surfactant, a wax, a sizing agent, a filler, an anti-corrosive agent, a conductive agent, a defoaming agent, a dispersant, an adjusting agent. of the viscosity, a flocculant, a coagulant, a paper strength enhancer, a process performance enhancer, a thin powder release agent, a bulking agent and the like.

Aeration stage

At this stage, either one or both of the white water circulation line and the water line is aerated with a gas containing oxygen. By increasing the amount of oxygen in the white water circulation line or maintaining the amount to exceed a certain level, a decrease in the amount of the slime control agent added in the papermaking process can be envisaged. , as well as an effective control of slime generation, compared to the absence of the aeration stage. Additionally, when the water line is aerated with the oxygen-containing gas in this stage, the generation of the silt in the entire white water circulation line can be easily controlled, compared to a large amount of the white water in the water. White water circulation line, through the efficient aeration of a comparatively small amount of the water line.

Although the reason for achieving the effects described above through the aeration of either or both of the white water circulation line and the water line is not necessarily clarified, the reason can be assumed, for example, that is indicated below. Specifically, since many of the slime control agents serve as an oxidizing agent, these could react with sulfite ions derived from reducing substances, such as microorganism hydrogen sulfide and mercaptan, before reacting with microorganisms, could a large amount of the slime control agent is consumed before achieving the desired antimicrobial effect. However, oxidation of sulphite ions to harmless sulfate ions, etc., is allowed by the oxidation of sulfite ions with oxygen in the oxygen-containing gas. In addition, the dissolution of a large amount of the oxygen-containing gas in the white water circulation line allows the partial pressure of the reducing substances, such as hydrogen sulfide, to be reduced, so that the solubility of the substances can be lowered. reducers. As a result, the amount of the added slime control agent can be decreased while the concentration of sulfite ions in the white water circulation line is reduced. In addition, it is assumed that slime generation can be controlled effectively without the need for an excess amount of the slime control agent.

In addition, by decreasing the amount of the added slime control agent, it is also possible to control the change in the color tone of the paper resulting from the use of a large amount of the slime control agent and the negative influences on the quality of the slime control agent. paper that imply, for example, the deterioration of the dye. Additionally, the entire area in the white water circulation line can be kept clean during a period of continuous operation time, thus allowing the operating time period to be prolonged.

Aeration is carried out with the oxygen-containing gas. The oxygen-containing gas is not particularly limited and is exemplified by an oxygen gas alone, a mixture of oxygen-containing gas, such as air and the like. Of these, in view of the availability, the gas mixture is preferred and air is more preferred. A gas other than oxygen in the gas mixture can be exemplified by a well-known gas, such as nitrogen and carbon dioxide. The oxygen-containing gas can be used alone or two or more types thereof can be used in combination.

The aeration procedure is not particularly limited, as long as either or both of the white water circulation line and the water line can be supplied with the oxygen-containing gas, and the use of a diffuser tube, a stirrer, may be involved. or similar. Of these, since the aeration can be carried out in a stable and continuous manner, the use of a diffuser tube is preferred. Specifically, fine bubbling up from the bottom to increase the contact efficiency between white water or water with oxygen-containing gas allows aeration to run more efficiently. The diffuser tube is not particularly limited and is exemplified by those provided with openings having a diameter of not less than 1 mm and not more than 5 mm, with a range of each not less than 5 cm and not more than 50 cm and the like. Either one or a plurality of diffuser tubes may be used.

The place where the aeration is executed in the white water circulation line or in the water line is not particularly limited and, for example, the place may be in the pipe, in the water channel, in the water tank. aeration 0 similar. Of these, since aeration can be executed more efficiently on a large scale, the use of the aeration tank is preferred and the use of an aeration tank having a diffuser tube on the lower part thereof is more preferred. The shape of the aeration tank is not particularly limited and the shape may be, for example, a box shape, a cylindrical shape, an elliptical cylindrical shape, a cone shape or the like. Also, either one or a plurality of aeration tanks can be provided.

The rate of aeration by the diffuser tube is not particularly limited and the aeration rate with respect to 1 m2 of the lower unit area of the aeration tank is preferably not less than 0.5 m3 / hour and not more than 10 m3 / hour , more preferably not less than 0.5 m3 / hour and not more than 8 m3 / hour. When the aeration rate is within the above range, the white water circulation line or the aerated water line with the oxygen containing gas tend to be sufficiently supplied with oxygen. When the aeration rate is higher than the upper limit, a larger scale equipment may be necessary. When the aeration rate is lower than the lower limit, aeration may be insufficient.

Also, the period of aeration time with the oxygen-containing gas is not particularly limited and is typically not less than 3 min and is not more than 30 days and preferably is not less than 4 min and is not more than 20 days. When the aeration time period is within the above limit, the white water circulation line or aerated water line with the oxygen containing gas tends to be sufficiently supplied with oxygen. When the aeration time period is greater than the upper limit, the manufacturing cost can increase. When the aeration rate is lower than the lower limit, aeration may be insufficient. In addition, the aeration can be carried out either continuously or several times intermittently.

In an exemplary aeration process, an aeration tank having a diffuser tube is used on the lower part thereof in the aeration in the aeration stage, the aeration rate being by the diffuser tube with respect to 1 m2 of the aeration area. lower unit of the aeration tank not less than 0.5 m3 / hour and not more than 10 m3 / hour.

Addition stage of slime control agent

In this step, the slime control agent is added to at least one line of the white water circulation line and the aerated water line to the oxygen-containing gas in the aeration step. By adding the slime control agent to at least one line of the white water circulation line and the aerated water line with the oxygen-containing gas in the aeration step, the number of bacteria can also be decreased in the white water circulation line, compared to the case in which aeration is not carried out, and, as a result, the generation of the slime can also be controlled. In addition, the slime control agent also allows the degradation of organic substances, such as starch, contained in the white water to be inhibited, whereby the generation of the slime can be controlled.

The silt control agent is not particularly limited and is exemplified by an organic antimicrobial agent, an inorganic antimicrobial agent, and the like.

The organic antimicrobial agent is not particularly limited and examples of the organic antimicrobial agent include methylene bisthiocyanate, 5-chloro-2-methyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, 4, 5-dichloro-2-n-nylisothiazolin-3-one, 1,2-benzisothiazolin-3-one, 2-n-octylisothiazolin-3-one, sodium dimethyldithiocarbamate, 2,2-dibromo-3-nitrilopropionamide, 2-bromo- 2-bromomethylglutaronitrile, 2-bromo-2-nitropropane-1,3-diol, 2,2-dibromo-2-nitroethanol, 1,1-dibromo-1-nitro-2-propanol, 1,1-dibromo-1- Nitro-2-acetoxyethane, 1,1-dibromo-1-nitro-2-acetoxypropane, 2-bromo-2-nitro-1,3-diacetoxypropane, tribromonitromethane, p-bromo-p-nitrostyrene, 5-bromo-5- nitro-1,3-dioxane, 5-bromo-2-methyl-5-nitro-1,3-dioxane, 1,2-bis (bromoacetoxy) ethane, 1,2-bis (bromoacetoxy) propane, 1,4- bis (bromoacetoxy) -2-butene, methylene bisbromoacetate, benzyl bromoacetate, N-bromoacetamide, 2-bromoacetamide, dichloroglyoxime, a-chlorobenzaldoxime, a-chlorobenzaldoxime acetate, 2- (phidroxife nil) glyoxyloxyhydroxychloride, triiodoalyl alcohol, 5-chloro-2,4,6-trifluoroisophthalonitrile, 2,4,5,6-tetrachloroisophthalonitrile, 3,3,4,4-tetrachlorotetrahydrothiophene-1,1-dioxide, 4,5- dichloro-1,2-dithiol-3-one, sulfone hexabromodimethyl, glutaraldehyde, orthophthalaldehyde, dichlorophen, a quaternary ammonium salt represented by the general Formula (1) and the like.

In Formula (1) above, R1 represents a linear or branched alkyl group having from 1 to 18 carbon atoms and three R1 may be the same or different; and R2 represents a linear or branched alkyl group having from 8 to 18 carbon atoms, a benzyl group or a hydroxyethyl group.

Of these, 2,2-dibromo-3-nitrilopropionamide and 2,2-dibromo-2-nitroethanol are preferred, since a superior antimicrobial effect is expected.

The inorganic antimicrobial agent is not particularly limited and examples of the inorganic antimicrobial agent include hypochlorites, such as sodium hypochlorite, potassium hypochlorite, calcium hypochlorite and barium hypochlorite, chlorine dioxide, chlorinated isocyanuric acid, a chlorine-bonded compound and Similar.

Of these, sodium hypochlorite and the chlorine-linked compound are preferred because they have an adequate oxidation capacity and low reactivity with the dissolved organic substances.

The chlorine-linked compound can typically be produced by the reaction of a chlorine donor releasing free chlorine with any one of ammonia, an ammonium salt and an organic nitrogen compound in a suitable condition. The chlorine donor is not particularly limited and, for example, sodium hypochlorite can be used. Examples of the ammonium salt include ammonium halides, such as ammonium chloride and ammonium bromide, ammonium sulfate, ammonium nitrate, and the like. As the organic amine, for example, sulfamic acid, urea or the like can also be used. Alternatively, a compound that generates hypochlorous acid and / or hypobromous acid in water may also be acceptable and examples of the compound include chlorine, chlorine dioxide, highly bleaching powder, hypochlorous acid, sodium hypochlorite, potassium hypochlorite, calcium hypochlorite. , ammonium hypochlorite, magnesium hypochlorite, hypobromous acid, sodium hypobromite, potassium hypobromite, calcium hypobromite, ammonium hypobromite, magnesium hypobromite, chlorinated and / or brominated hydantoins, chlorinated and / or brominated isocyanuric acid and sodium salts and potassium salts thereof and the like.

Although the chlorine-bound compound can be produced according to a well-known process, "Fuzzicide (trade name)" (manufactured by Kurita Water Industries Ltd.) can be commercially available. "Fuzzicide" is a reaction product of 1: 1 (molar ratio) of ammonium bromide and sodium hypochlorite.

The silt control agent can be used alone or two or more types thereof can be used in combination. Also, the slime control agent can be added once or divided into aliquots and added several times.

The procedure of adding the slime control agent to the white water circulation line or the water line is not particularly limited and the slime control agent can be added directly or the slime control agent can be dissolved or dispersed in a solvent for use as a solution or dispersion. The solvent is not particularly limited and is exemplified by water, an organic solvent, a mixed solvent thereof and the like.

The organic solvent is not particularly limited and examples of the organic solvent include:

amides, such as dimethylformamide and dimethylacetamide;

glycols, such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol and polyethylene glycol;

glycol ethers, such as methyl cellosolve, phenyl cellosolve, diethylene glycol monomethyl ether and dipropylene glycol monomethyl ether;

glycol esters, such as diethylene glycol monomethyl ether acetate, ethylene glycol diacetate and 2,2,4-trimethyl-1,3-pentanediol diisobutyrate;

alcohols having 8 or less carbon atoms;

esters, such as methyl acetate, ethyl acetate, butyl acetate, dimethyl maleate, diethyl adipate, ethyl lactate, methyl glutarate, dimethyl succinate, dimethyl phthalate, 1,2-dibutoxyethane, 3-acetate methoxybutyl, 2-ethoxyethyl acetate and propylene carbonate;

ketones, such as acetone, methyl ethyl ketone, methyl isobutyl ketone and isophorone;

aromatic solvents, such as toluene, xylene and 1,2-dimethyl-4-ethylbenzene;

dimethyl sulfoxide, dioxane, N-methylpyrrolidone; and similar.

Of these, water and diethylene glycol monomethyl ether are preferred, since greater dispersibility and / or solubility can be guaranteed.

The concentration of the slime control agent in the solution is not particularly limited and is typically not less than 1% by mass and not more than 40% by mass and preferably not less than 2% by mass and not more than 30% by mass . When the concentration is within this range, the slime control agent tends to disperse or dissolve sufficiently in the solvent. When the concentration is higher than the upper limit, the slime control agent can not disperse or dissolve sufficiently. When the concentration is lower than the lower limit, the solvent may be required in a large quantity.

The amount of the slime control agent added to the white water circulation line or the water line (the amount added to one of the white water circulation line and the water line when the slime control agent is added. to both lines) is not particularly limited and, in terms of equivalent solid content, the amount is typically not less than 0.1 mg / l and is not greater than 1,000 mg / l and preferably is not less than 1 mg / l and is not greater of 100 mg / l. When the quantity is within this range, the generation of the slime tends to be able to be sufficiently controlled. When the quantity is greater than the upper limit, it can increase the manufacturing cost. When the amount is less than the lower limit, control of slime generation may fail.

The period of time from the start of the aeration treatment to the addition of the slime control agent is not particularly limited and this period of time is preferably not less than 0 min and is not more than 30 min. When the period of time from the start of the aeration treatment to the addition of the slime control agent is greater than 30 min, the bacteria and the like are activated and propagated again, whereby the reducing substances can increase.

FIG. 1 shows a view illustrating an embodiment of the papermaking process according to the present invention. Next, aeration procedures will be described with the oxygen-containing gas from either or both of the white water circulation line and the water line and, in addition, addition of the slime control agent to at least one line of the white water circulation line and aerated water line with the oxygen-containing gas in the aeration stage with references to specific examples. It should be noted that, below, a case is described in which the white water circulation line is aerated with the oxygen-containing gas and the slime control agent is added to this white water circulation line (first method) and a case in which the water line is aerated with the oxygen-containing gas and the slime control agent is added to this water line (second method).

First method

First, in the case where the circulation line 22 of white water is aerated with the oxygen-containing gas and the slime control agent is added to this circulation line 22 of white water, the white water is aerated 10 with the oxygen-containing gas in an aeration tank 17 and / or the like. Next, a slurry of raw material paste in a machine tank 2 is mixed with the white water 10 in the aeration tank 17. Subsequently, a slime control agent 18 and the like are added to the white water 10 and transferred to the slurry. an inlet 5 through a screen 4 by means of a fan pump 3. The raw material paste slurry transferred to inlet 5 is fed to a portion of wire 6 and dehydrated. The dried dehydrated sheet 7 is transferred from a press part 8 to a dryer part 9. The white water 10 separated in the wire part 6 is reserved in a silo 11 of white water and a part of it is charged again in the aeration tank 17 and the like, followed by aeration in a manner similar to that described above.

Alternatively, in a case where the circulation line 22 of white water is aerated with the oxygen-containing gas and the slime control agent is added to this circulation line 22 of white water, a water line 19 for the feed to the white water circulation line 22 can be provided with an aeration tank 20 to carry out the aeration and the slime control agent 21 can be added to the water line 19 (second aeration stage and second addition step of the slime control agent).

The procedures of aeration and addition in the water line 19 are not particularly limited and aeration and addition can be carried out in a manner similar to, for example, the aeration process and the addition procedure in the line of circulation 22 of white water.

Second method

On the other hand, in the case where the water line 19 is aerated with the oxygen-containing gas and the slime control agent is added to this water line 19, the water line 19 for supply to the line of circulation 22 of white water is aerated with the oxygen-containing gas in an aeration tank 20 having a diffuser tube on the bottom thereof. After the mixing of the water line 19 and the white water 10 of the white water silo 11, the mixture is combined with the slurry of raw material paste in the machine tank 2. Next, the control agent 21 is added. of slime to the aeration tank 20 and transferred to the inlet 5 through the screen 4 by means of the fan pump 3. The raw material paste slurry transferred to the inlet 5 is fed to the wire part 6 and dehydrated. The dried dehydrated sheet 7 is transferred from the press part 8 to the dryer part 9. The white water 10 separated in the wire part 6 is reserved in the silo 11 of white water to allow the circulation of the white water 10.

Alternatively, in a case where the water line 19 is aerated with the oxygen-containing gas and the slime control agent is added to this water line 19, aeration with the oxygen-containing gas is preferred. and / or the addition of the slime control agent 18, etc., to the aeration tank 17 and the like.

In other words, it is preferred that the aeration step of the circulation line 22 of white water is also included with the oxygen-containing gas (second aeration stage). Also, by aerating the circulation line 22 of white water with the oxygen-containing gas, the generation of the slime can be controlled in a synergistic manner.

Furthermore, it is preferred that the step of adding a slime control agent to the white water circulation line 22 (second step of addition of the slime control agent) is also included. Therefore, by aeration also of the circulation line 22 of white water with the oxygen-containing gas, the generation of the slime can be controlled even more synergistically.

The procedures of aeration and addition in the circulation line 22 of white water are not particularly limited and aeration and addition can be carried out in a manner similar to, for example, the aeration process and the addition process. on the water line 19.

Measurement stage

It is preferred that the slime control method includes, in addition, the measurement step of at least one selected from the group of measurement elements consisting of the oxidation-reduction potential, the concentration of sulfite ions and the amount of dissolved oxygen in the white water circulation line. By controlling the aeration rate in the aeration step and / or the amount of the slime control agent added in the addition step of the slime control agent, based on the measurement results obtained in the measurement step, The slime generation can be controlled more safely and more accurately.

Specifically, it is preferred that the rate of aeration in the aeration step and / or the amount of the slime control agent added in the addition step of the slime control agent be adjusted in such a way that, in the line of white water circulation: the oxidation-reduction potential is not less than -150 mV; the concentration of sulphite ions is not greater than 2.0 mg SO3- / l; and / or the amount of dissolved oxygen is not less than 1 mg / l. Slime generation can be controlled more effectively by such adjustment.

The oxidation-reduction potential is adjusted to be preferably not less than -150 mV and more preferably not less than -100 mV and not more than 500 mV. When the line is consumed together with increasing contamination with microorganisms, the oxidation-reduction potential is likely to be reduced; However, when the oxidation-reduction potential is within the above range, the amount of oxygen in the white water circulation line could be sufficient, so the generation of the slime tends to be controlled effectively. When the oxidation-reduction potential is greater than the upper limit, the amount of oxygen in the white water circulation line can be unnecessarily excessive. When the oxidation-reduction potential is less than the lower limit, the control of slime generation may fail.

The method of measuring the oxidation-reduction potential is not particularly limited and is exemplified by potentiometry, potentiometric titration and the like.

The concentration of sulphite ions is adjusted to be preferably not higher than 2.0 mg SO3 '/ and more preferably not greater than 1.5 mg SO3' / l. When the concentration of sulphite ions is within the above range, the concentration of sulfite ions in the white water circulation line tends to be reduced sufficiently. When the concentration of sulfite ions is higher than the upper limit, the reducing substances may not be sufficiently reduced.

The concentration of sulfite ions can be measured according to JIS K 0102: 2008.

The amount of dissolved oxygen is adjusted to be preferably not less than 1 mg / l and most preferably not less than 5 mg / l and not greater than 100 mg / l. When the amount of dissolved oxygen is within the range above, the amount of oxygen in the white water circulation line could be sufficient, so the generation of the slime tends to be controlled effectively. When the amount of dissolved oxygen is greater than the upper limit, the amount of oxygen in the white water circulation line can be unnecessarily excessive. When the amount of dissolved oxygen is less than the lower limit, control of silt generation may fail. The amount of dissolved oxygen can be measured by the use of a dissolved oxygen meter.

Additionally, the number of viable cells is not particularly limited and typically is not greater than 1 x 10 7 CFU / ml and preferably is not greater than 1 x 10 6 CFU / ml. When the number of viable cells is greater than the upper limit, the control of slime generation may fail.

The number of viable cells is measured by a colony counting method in which water from a cooling water line is used that should be prevented from decomposing as a source of microorganism and determines the number of colonies formed from a certain amount of water to designate the number of viable cells. Alternatively, the number of viable cells can also be determined according to an absorption / turbidity measurement method, a weight measurement method or the like.

The method of colony counting is not particularly limited and is exemplified by a plate culture method, a capillary method, a membrane filter method and the like.

The sterilization rate is not particularly limited and is typically not less than 99.5% and preferably not less than 99.9%. When the sterilization rate is lower than the lower limit, control of slime generation may fail.

The measurement step can also be carried out by measuring another parameter. The other parameter is not particularly limited and is exemplified by markers, such as the amount of calcium ions, electrical conductivity, glucose concentration, starch concentration, pH and turbidity.

Others

Other conditions of the intervening steps, for example, temperature, pressure, time period and equipment, at each stage are not particularly limited and can be appropriately predetermined according to the material and the like used. The number of subjects in each stage is not particularly limited and can be carried out either one sub-step or multiple sub-steps. The quantitative determination or the qualitative determination of the material and the product can be carried out according to a well-known method, such as NMR, IR, an element analysis or mass spectrometry. In addition, the material used can be a single one or a plurality of types of materials can be used in combination.

In accordance with the present invention, the generation of silt in a white water circulation line in a papermaking process can be controlled in a sufficient and convenient manner. Therefore, the slime control method can be used suitably in a papermaking process in papermaking. In addition, in a papermaking process, recycling or a decrease in the amount of used slime control agent, a decrease in the amount of fresh water used, a reduction in wastewater treatment and the like may also be contemplated.

Examples

Hereinafter, the embodiment of the present invention will be explained in detail by way of Examples, but the present invention is by no means limited to these Examples. It should be noted that, in the Examples and Comparative Examples, measurements were made according to the following methods.

Oxidation-reduction potential (ORP in English)

The oxidation-reduction potential (mV) was measured by the use of an oxidation-reduction potential meter (manufactured by Toko Kagaku Co., LTD.) Through the use of potentiometry.

Sulfite ion concentration

The concentration of sulfite ions (mg SO3- / l) was measured according to JIS K 0102: 2008. Specifically, an appropriate amount of a sample was charged into a volumetric flask and a pararosaniline solution, a formaldehyde solution and a mercury chloride solution were added thereto to allow color development. After allowing it to stand for 20 min, a colorimetry was performed at 572 nm using a blank test solution prepared separately in a manner similar to a control one. Therefore, the concentration of sulfite ions was determined.

Amount of dissolved oxygen

The amount of dissolved oxygen (mg / l) was measured using a diaphragm electrode type dissolved oxygen meter (manufactured by Orbisphere, Inc.).

Number of viable cells

The number of viable cells (CFU / ml) was measured by: the dilution of a test water; thoroughly mixing a certain amount of it with an agar medium containing nutrients; plating the mixture for 1 day; and, later, the count of the number of colonies produced.

Sterilization rate

The sterilization rate (%) was calculated by using the following Formula:

sterilization rate (%) = (((number of viable cells before treatment) - (number of viable cells after treatment)) / (number of viable cells before treatment) x 100.

Sterilization effect

The sterilization effect was determined according to the following evaluation criteria.

A: the sterilization rate being not less than 99.9%

B: the sterilization rate being not less than 99.5% and less than 99.9%

C: the sterilization rate being not less than 90% and less than 99.5%

D: the sterilization rate being less than 90%

Slime control effect

The slime control effect was determined according to the following evaluation criteria.

A: no slime adhesion was found

B: the thickness of the silt being less than 0.1 mm

C: the thickness of the slime being not less than 0.1 mm and less than 0.5 mm

D: the thickness of the slime being not less than 0.5 mm

Preparation A

A 12% sodium hypochlorite was prepared to provide Preparation A.

Preparation B

Ammonium bromide was reacted with sodium hypochlorite in a molar ratio of 1: 1 to provide Preparation B.

Preparation C

2,2-Dibromo-3-nitrilopropionamide (DBNPA) was mixed in an amount of 20 parts by mass with 80 parts by mass of diethylene glycol monomethyl ether to provide a Preparation C.

Preparation D

2,2-Dibromo-2-nitroethanol (DBNE) was mixed in an amount of 20 parts by mass with 80 parts by mass of diethylene glycol monomethyl ether to provide a Preparation D.

Example 1 and Comparative Example 13

By using a white water collected from the papermaking machinery, the oxidation-reduction potential, the concentration of sulfite ions, the amount of dissolved oxygen and the number of viable cells were measured. Before treatment, the oxidation-reduction potential of white water was -388 mV; the concentration of sulphite ions was 8.8 mg SO3- / l; the amount of dissolved oxygen was less than 0.1 mg / l; and the number of viable cells was 3.8 x 108 CFU / ml. The white water collected from the papermaking machinery was taken in a volume of 2 l and aerated with air at a flow rate of 300 ml / min (corresponding to 1 m3 / hour with respect to a unit area of less than 1 m2) for 5 min by using a diffuser tube. Subsequently, a slime control agent was added thereto in such a way that a concentration was reached in terms of the concentration of active principle and, 10 min later, the oxidation-reduction potential, the concentration of sulphite ions were measured. , the amount of dissolved oxygen and the number of viable cells (Example 1). Additionally, similar to Example 1, except that the slime control agent (preparation) was not added, the oxidation-reduction potential, the sulfite ion concentration, the amount of dissolved oxygen and the number of viable cells (Comparative Example 13). The sterilization rate of Example 1 was calculated from the number of viable cells before treatment and the number of viable cells in Example 1. In addition, the sterilization effect was evaluated.

Examples 2 to 12

The oxidation-reduction potential, the concentration of sulfite ions, the amount of dissolved oxygen, the number of viable cells and the sterilization rate were measured in a manner similar to Example 1, except that the type and concentration of the control agent of slime (preparation) added were as shown in Table 1.

Comparative example 1

The oxidation-reduction potential, the concentration of sulfite ions, the amount of dissolved oxygen, the number of viable cells and the sterilization rate were measured in a manner similar to Example 1, except that the aeration treatment was not carried out. and that the type and concentration of the slime control agent (preparation) added were as shown in Table 1 (Comparative Example 1). The sterilization rate of Comparative Example 1 was calculated from the number of viable cells before treatment and the number of viable cells in Comparative Example 1. In addition, the sterilization effect was evaluated.

Comparative examples 2 to 12

In a manner similar to Comparative Example 1, except that the type and concentration of the slime control agent (preparation) added were as shown in Table 1, the oxidation-reduction potential, the concentration of sulphite ions were measured. , the amount of dissolved oxygen, the number of viable cells and the sterilization rate. In addition, the sterilization effect was evaluated.

Example 13 and Comparative Example 18

By using a white water collected from a papermaking machinery, the oxidation-reduction potential, the concentration of sulfite ions, the amount of dissolved oxygen and the number of viable cells were measured (measurement step). Before treatment, the oxidation-reduction potential of white water was -361 mV; the concentration of sulphite ions was 8.8 mg SO3 '/ l; the amount of dissolved oxygen was less than 0.1 mg / l; and the number of viable cells was 4.0 x 108 CFU / ml. By using a white water collected from a papermaking machine, in an aeration tank that had a diffuser tube on the bottom of the same, the white water was aerated with air by using the diffuser tube provided with openings having a diameter of 2 mm, with an interval each of 10 cm, at an aeration rate of 5 m3 / hour with respect to the unit area of 1 m2 (aeration stage). A slurry of raw material pulp from a machine tank, which had been prepared using a bleached Kraft pulp of hardwood and a de-inked pulp as raw material pulps, was mixed with the white water from the aeration tank. Preparation A was added to the white water at a rate of 100 mg / l (addition step of the slime control agent) and the slurry of raw material paste was transferred to an inlet through a screen by means of a pump of fan. The raw material paste slurry transferred to the inlet was fed to a wire part and dehydrated. The dehydrated wet sheet was transferred from a press part to a dryer part. The white water separated in the wire part was reserved in a white water silo and a part of it was charged back into the aeration tank, followed by aeration in a manner similar to that described above (water circulation line white). Fourteen days later, the oxidation-reduction potential, the concentration of sulfite ions, the amount of dissolved oxygen and the number of viable cells of the white water were measured (Example 13). In addition, the amount of silt adhering to the white water circulation line was visually observed. On the other hand, the oxidation-reduction potential, the concentration of sulfite ions, the amount of dissolved oxygen and the number of viable cells were measured in a manner similar to Example 13, except that the slime control agent was not added ( Preparation) (Comparative Example 18). The sterilization rate of Example 13 was calculated from the number of viable cells before treatment and the number of viable cells in Example 13.

Examples 14 to 16

The oxidation-reduction potential, the concentration of sulfite ions, the amount of dissolved oxygen, the number of viable cells and the sterilization rate were measured in a manner similar to Example 13, except that the type and concentration of the control agent The addition of slime (preparation) were as shown in Tile 2. In addition, the amount of silt adhered to the white water circulation line was visually observed.

Comparative examples 14 to 17

The oxidation-reduction potential, the concentration of sulfite ions, the amount of dissolved oxygen and the number of viable cells were measured in a manner similar to Example 13, except that the aeration treatment was not carried out and that the type and the concentration of the slime control agent (preparation) added were as shown in Table 2 (Comparative Examples 14 to 17). The amount of the silt adhering to the pipe of the white water circulation line was visually observed. The sterilization rates of Comparative Examples 14 to 17, respectively, were calculated from the number of viable cells before treatment and the numbers of viable cells in Comparative Examples 14 to 17.

Table 2 Example 17 and Comparative Example 23

By using a white water collected from a papermaking machinery, the oxidation-reduction potential, the concentration of sulfite ions, the amount of dissolved oxygen and the number of viable cells were measured (measurement step). Before treatment, the oxidation-reduction potential of white water was -387 mV; the sulphite ion concentration was 9.0 mg SO3- / l; the amount of dissolved oxygen was less than 0.1 mg / l; and the number of viable cells was 4.1 x 108 CFU / ml. In an aeration tank that had a diffuser tube on the bottom of it, a water supply line was aerated to feed water to the white water circulation line with the air by using a diffuser tube provided with water. openings having a diameter of 2 mm, with an interval each of 10 cm, at an aeration rate of 2 m3 / hour with respect to the unit area of 1 m2 (aeration stage). After the mixing of the water line and the white water of the white water silo, a slurry of raw material pulp from a machine tank, which had been prepared using a bleached kraft pulp of hardwood and a de-inked pulp as pulp raw material, mixed with the resulting white water. Preparation A was added to the aeration tank at a rate of 100 mg / l (addition step of the slime control agent) and the slurry of raw material paste was transferred to an inlet through a screen by means of a fan pump. The raw material paste slurry transferred to the inlet was fed to a wire part and dehydrated. The dehydrated wet sheet was transferred from a press part to a dryer part. The white water separated in the wire part was reserved in a white water silo and the white water was circulated (white water circulation line). Fourteen days later, the oxidation-reduction potential, the concentration of sulfite ions, the amount of dissolved oxygen and the number of viable cells of the white water were measured. In addition, the amount of the silt adhering to the pipe of the white water circulation line was visually observed (Example 17). On the other hand, the oxidation-reduction potential, the concentration of sulfite ions, the amount of dissolved oxygen and the number of viable cells were measured in a manner similar to Example 17, except that the slime control agent was not added ( Preparation) (Comparative Example 23). The sterilization rate of Example 17 was calculated from the number of viable cells before treatment and the number of viable cells in Example 17.

Examples 18 to 24, Comparative Example 24

The oxidation-reduction potential, the concentration of sulfite ions, the amount of dissolved oxygen, the number of viable cells and the sterilization rate were measured in a manner similar to Example 17, except that the aeration rate and the type and The concentration of the added slime control agent (preparation) was as shown in Table 3. In addition, the amount of the silt adhering to the line of the white water circulation line was visually observed.

Comparative examples 19 to 22

The oxidation-reduction potential, the concentration of sulfite ions, the amount of dissolved oxygen and the number of viable cells were measured in a manner similar to Example 17, except that the aeration treatment was not carried out and that the type and the concentration of the slime control agent (preparation) added were as shown in Table 3. In addition, the amount of the silt adhering to the line of the white water circulation line was visually observed. Without carrying out the aeration treatment, the sterilization rates of Comparative Examples 19 to 22, respectively, were calculated from the number of viable cells before treatment and the numbers of viable cells in Comparative Examples 19 to 22.

From Tables 1 to 3, it is shown that the sterilization effect and the slime control effect were improved in the Examples, as compared to the Comparative Examples. It should be noted that, in Tables 1 to 3, the expression "a E + b" in relation to the number of viable cells means "a x 10b".

[Industrial applicability]

In accordance with the present invention, the generation of silt in a white water circulation line in a papermaking process can be controlled in a sufficient and convenient manner. Therefore, the slime control method can be used suitably in a papermaking process in papermaking.

[EXPLANATION OF THE REFERENCE NUMBERS]

1 stage of material production

2 machine tank

3 fan pump

4 screen

5 entry

6 wire part

7 wet sheet

8 press section

9 part of dryer

10 white water

11 white water silo

12 slime agent control

13 aeration tank

14 slime agent control

15 solid-liquid separator

16 solid content that is downloaded or recovered in the material system

17 aeration tank

18 slime agent control

19 water line for water supply to the white water circulation line

20 aeration tank

21 slime agent control

22 white water circulation line

23 fan pump

24 fan pump

25 fan pump

26 fan pump

Claims (4)

1. A method of slime control in a white water circulation line in a papermaking process, the method comprising: aerating with a gas containing oxygen either one or both of the white water circulation line and the water feed line for the water supply to the white water circulation line; Y add a slime control agent to at least one line of the white water circulation line and the aerated water feed line with the oxygen-containing gas in the aeration. 2. The slime control method according to claim 1, further comprising measuring at least one selected from the group of measuring elements consisting of an oxidation-reduction potential, a concentration of sulfite ions and an amount of dissolved oxygen in the white water circulation line, in which a rate of aeration in the aeration and / or an amount of the slime control agent added is regulated, based on the measurement results obtained in the measurement. 3. The slime control method according to claim 2, wherein the rate of aeration in the aeration and / or the amount of the slime control agent added is regulated in such a way that, in the line of white water circulation: the oxidation-reduction potential is not less than -150 mV; the concentration of sulphite ions is not greater than 2.0 mg SO3- / l; and / or the amount of dissolved oxygen is not less than 1 mg / l. The slime control according to any one of claims 1 to 3, wherein an aeration tank having a diffuser tube on a lower part thereof is used for aeration and a rate of aeration by the diffuser tube with respect to 1 m2 of a lower unit area of the aeration tank is not less than 0.5 m3 / hour and is not greater than 10 m3 / hour.