JP2006346640A - Determination method of slime control effect and slime control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely prevent slime trouble even in an aqueous system with variation in conditions when conducting slime control by adding an oxidizing bactericide to the sterilizing object aqueous system, by quickly and correctly determining whether or not slime control is correctly conducted without requiring manpower, further by specifying a portion in the system with a slime generation tendency, conducting correct slime control to the required portion in an early stage. <P>SOLUTION: By measuring continuously or intermittently an oxidation-reduction potential at least at one place of the aqueous system conducting slime control by adding the oxidizing bactericide, transition of the oxidation-reduction potential with time is determined. When the transition of the oxidation-reduction potential with time is in a lowering tendency, slime is determined in a formation environment from insufficient slime control effect. When the generation of slime is determined, the addition amount of the oxidizing bactericide is increased. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for determining whether or not slime control is properly performed when adding an oxidizing disinfectant to an aqueous system to be sterilized and performing slime control, and based on the determination result, an oxidizing disinfectant It is related with the method of performing precise slime control by controlling the addition amount of.

  In water systems that contain high concentrations of organic substances, such as papermaking and pulp conditioning, and that have warm environmental conditions, slime (biofilm) is produced by bacteria, reducing the productivity of paper breakage, It causes troubles such as deteriorating quality such as spots and defects, and in the event of a serious case, it causes deterioration of the working environment and local environment due to the generation of hydrogen sulfide.

  Conventionally, an oxidizing disinfectant such as sodium hypochlorite has been used to prevent such slime damage. Usually, slime control is performed by periodically injecting an oxidizing disinfectant (for example, about 3 times a day) (for example, JP-A-5-146785). In this case, excessive injection of the oxidizing disinfectant is not preferable in terms of environmental protection and drug cost. Therefore, the oxidizing disinfectant is quantitatively injected in the minimum necessary amount.

  However, in such regular quantitative injection of an oxidizing disinfectant, the added chemicals are consumed quickly due to water quality fluctuations and the amount of dirt in the treated water system due to fluctuations in conditions, etc., and a sufficient residual concentration can be maintained. In some cases, the desired treatment effect could not be obtained.

  Conventionally, in order to cope with the excess and deficiency of drugs due to water quality fluctuations, etc., by manual work, confirmation of residual drug concentration by titration method using a reducing substance, colorimetric analysis by DPD method, etc., bacterial count measurement, It is performed to check the state of contamination in the system and control the injection amount of the drug based on the result. However, such measurement or confirmation requires a lot of time and effort, so it is difficult to carry out it frequently, it can be applied only to a limited number of places, and it can be handled immediately. Because it is difficult to do so, many cases of slime failure due to poor drug injection have been observed.

In particular, recently, in the papermaking process and pulp adjustment process, the low oxygen concentration in the system, the trapping of organic matter in the dead space or mesh generated due to the equipment characteristics, etc., and the residence time in the system by improving the circulation rate of raw materials and water Factors that promote the decay of organic matter, such as an increase in the amount of organic matter, and, in the papermaking process, conditions such as irregular fluctuations in the retention time in the system of recovered raw materials and recovered treated water due to operational troubles such as increased paper breakage In a situation where the cause of slime damage due to fluctuations tends to increase, it is necessary to accurately grasp the occurrence of slime in the system and perform appropriate injection control of oxidizing disinfectants, and further to the tendency to slime damage However, it is currently impossible to respond to such a request.
JP-A-5-146785

  The present invention, when adding an oxidizing disinfectant to the water system to be sterilized to perform slime control, quickly and accurately determine whether or not the slime control is properly performed, further, the system Slime control to identify the place where slime is likely to occur in the early stage and to perform appropriate slime control treatment at the necessary place at an early stage to reliably prevent slime damage even in water systems with variable conditions It is an object of the present invention to provide a determination method and a slime control method.

  As a result of intensive studies to solve the above problems, the present inventors can judge the decay of organic matter in an aqueous system using the oxidation-reduction potential (ORP) as an index, and a decrease in ORP indicates the progress of decay; When the ORP of the water system changes from the plus range to the minus range, the system becomes anoxic and further anaerobic, and the decay of organic matter by anaerobic bacteria progresses. It was found that growth is promoted; generation of hydrogen sulfide begins when ORP decreases further and reaches around -260 mV. And, by adding an oxidizing disinfectant, these bacteria can be sterilized and ORP in the system can be added to make the environment difficult for these bacteria to grow. For example, it is determined that the slime is likely to be generated when the temporal transition of the ORP tends to decrease, so that the ORP does not tend to decrease, and the ORP does not become negative. As described above, the present inventors have found that slime failure can be reliably prevented by performing chemical injection control of an oxidizing disinfectant, and the present invention has been completed.

That is, the gist of the present invention is as follows.
[1] A method for determining a slime control effect in an aqueous system in which slime control is performed by adding an oxidizing disinfectant, wherein the oxidation-reduction potential in at least one location of the aqueous system is measured continuously or intermittently. Determining the time-dependent transition of the oxidation-reduction potential, and determining, when the time-dependent transition of the oxidation-reduction potential is declining, that the slime control effect is insufficient and thus determining that the environment is in a slime formation environment; A method for judging a slime control effect, comprising:
[2] The determination method according to [1], wherein the redox potential is measured at a plurality of locations in the aqueous system.
[3] In the method of performing slime control by adding an oxidizing bactericidal agent to an aqueous system, when the determination method according to [1] or [2] The slime control method characterized by increasing the addition amount of a disinfectant.

  According to the determination method of the slime control effect of the present invention, the occurrence state of slime is surely grasped from the ORP in the system, and whether or not the slime control process is appropriate and sufficient effect is achieved is accurately determined. be able to. In particular, by measuring the ORP at a plurality of locations, it is possible to identify a location that tends to be a source of slime failure. Therefore, according to the slime control method of the present invention, when the slime control effect is insufficient due to this slime control effect judgment method, and it is judged that the slime formation environment exists, the addition amount of the oxidizing bactericide is increased. For example, optimal chemical injection control of the oxidizing disinfectant can be performed to reliably prevent water-based slime failure.

According to such a determination method and slime control method of the slime control effect of the present invention, for example, the following effects are exhibited.
1. In the paper-making process, the occurrence of defects due to slime, paper breakage, and the like are almost eliminated, so that productivity and quality can be improved.
2. It is possible to visually confirm that slime control is normally performed as daily inspection management.
3. Since the slime control processing specification can be improved at an early stage using ORP as an index, slime failure can be prevented in advance.
4). Slime is prone to occur, it is possible to quickly identify the places that need to be strengthened slime control processing, can improve the slime control processing specifications directly and individually, and effective Excessive chemical injection can be prevented by adjusting the chemical injection amount.
5). Optimal slime control processing is possible at all times without any manual labor by automatic measurement and automatic chemical injection.

  Embodiments of a method for determining a slime control effect and a slime control method of the present invention will be described in detail below.

  In the present invention, ORP is measured in an aqueous system to which slime control is performed by adding an oxidizing disinfectant, and the temporal transition of ORP is examined, and the slime control effect is determined based on this result. And when the slime control effect is inadequate and it determines with it being in the formation environment of a slime, the addition amount of an oxidizing disinfectant is increased.

  The determination method of the slime control effect and the slime control method are specifically carried out in the following procedure.

(1) Install an ORP measurement point in the slime control target water system. The ORP measurement point may be one point or a plurality of two or more points. When two or more points are provided, it is possible to identify the location where slime tends to occur by examining the temporal transition of the ORP for each side fixed point, individually and optimally for each measurement point Slime control process.

(2) The ORP measurement is performed at the ORP measurement point to examine the temporal transition of the ORP. It is preferable that the measurement result is taken into a control unit capable of accumulating data, and the temporal transition of the ORP is automatically recorded and output.

(3) Pay attention to the line that is the basis of the transition of ORP over time (measurement value line when no oxidizing disinfectant is added; for example, line A in FIG. It is examined whether or not there is a downward trend compared with the original ORP. In addition, ORP is changing as shown in FIGS. 2 and 3 to be described later, and the decreasing tendency indicates, for example, a state in which the ORP value before the addition of the drug shows a gradually or rapidly decreasing tendency. .

(4) When the time course of ORP tends to decrease, the amount of the oxidizing bactericide added is increased.
For example, in a system in which an oxidizing disinfectant is regularly added at a certain frequency, the increase in the amount of addition of the oxidizing disinfectant is an extension of the injection time or unit when periodically adding the oxidizing disinfectant. It can be easily carried out by increasing the injection amount per hour. Moreover, it can also carry out by raising the addition frequency of the oxidizing disinfectant within a fixed period.
When ORP is measured at multiple points, it is only necessary to increase the amount of oxidizing bactericides added to the measuring points where ORP tends to decrease, and the oxidizing bactericides should be applied efficiently. Can do.

(5) If the decreasing trend of the ORP over time is resolved by increasing the amount of addition of the oxidizing bactericide and the temporal transition of the ORP changes to an increasing trend, or if the ORP level is restored to the original level Then, the addition amount of the oxidizing disinfectant is returned to the initial addition amount (set addition amount). The set addition amount of the oxidizing disinfectant is set in advance by a preliminary test using the water-based water.

  The increase in the addition amount of the oxidizing disinfectant or the return to the set addition amount can be performed manually, but automatic control based on the output signal from the control unit eliminates the need for manual operation. Control can be performed.

  In the present invention, the oxidizing disinfectant added to the aqueous system is not particularly limited, but a compound that generates hypochlorous acid and / or hypobromite in water is preferable. For example, chlorine, chlorine dioxide, highly bleached powder, Hypochlorous acid, sodium hypochlorite, potassium hypochlorite, calcium hypochlorite, ammonium hypochlorite, magnesium hypochlorite, hypobromous acid, sodium hypobromite, hypobromite Examples include potassium, calcium hypobromite, ammonium hypobromite, magnesium hypobromite, chlorinated and / or brominated hydantoins, chlorinated and / or brominated isocyanuric acid, and sodium and potassium salts thereof. . Further, hypobromite may be generated by simultaneously reacting an inorganic bromide such as sodium bromide, potassium bromide, ammonium bromide or calcium bromide and an oxidizing compound such as chlorine, chlorine dioxide or ozone. . In addition to the inorganic oxidizing fungicide as described above, an organic oxidizing fungicide may be used. Examples of organic oxidizing bactericides include 2-bromo-2-nitropropane-1,3-diol, 2,2-dibromo-2-nitro-1-ethanol, 2,2-dibromo-3-nitrilopropionamide. 1,4-bis (bromoacetoxy) -2-butene and the like. These oxidizing bactericides may be used individually by 1 type, and may use 2 or more types together.

  Although there is no restriction | limiting in particular in the addition form of these oxidizing disinfectants, Generally, it is preferable to use as about 1-35 weight% aqueous solution.

  Such a slime control effect determination method and slime control method of the present invention are useful for slime control of various water systems such as a papermaking process, a pulp adjustment process, an open circulating cooling water, and a closed circulating cooling water.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Example 1
A slime control treatment based on ORP was performed for the fine paper-making paper aqueous system shown in FIG.

  In this high quality papermaking water system, broke, NBKP (hardwood bleached kraft pulp), LBKP (softwood bleached kraft pulp) and recovered raw materials are used as raw materials, and the raw materials in the broke tank 1, NBKP tank 2, and LBKP tank 3 are used. After adjusting the concentration by using charged water and concentrated water from the primary treated water tank 16, it is introduced into the mixing chest 4 together with the recovered raw material from the recovered raw material tank 17 and mixed uniformly to form a slurry. This slurry passes through the machine chest 5 and the seed box 6, together with white water from the white water silo 13, through the pump 7, the screen 8 and the inlet 9, and is sent to the wire part 10, in the wire process in the wire part 10, in the press part 11. It dehydrates through a press process and a 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 12 are sprinkled from the shower nozzle 12A in order to keep the wire and felt clean. The water in the water tank 12 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 primary treatment water tank 16 from the recovery device 15. The water has been sent. White water (recovered raw material) collected and concentrated by the recovery device 15 is stored in a recovered raw material tank 17.

  In this embodiment, ORP meters 21, 22, and 23 are provided in the white water silo 13, the primary treated water tank 16, and the recovered raw material tank 17, respectively. 20 is a control unit, and 30 is a chemical injection facility for oxidizing sterilizers. The measured values of the ORP meters 21, 22, and 23 are input to the control unit 20. Based on these measured values, the control unit 20 A chemical injection signal is output to the injection facility 30, and the amount of chemical injection from the chemical injection facility 30 to the white water silo 13, the primary treated water tank 16, and the recovered raw material tank 17 is controlled.

Specific implementation conditions and implementation methods are as follows:
[Conditions]
Target water: White paper of fine paper making water system White water temperature: 25-40 ° C
White water pH: 7.0-8.0
Chemical addition point: 3 points (white water silo 13, primary treated water tank 16, recovery raw material tank 17)
ORP measurement points: 3 points (white water silo 13, primary treated water tank 16, recovered raw material tank
17)
Oxidizing disinfectant: 90 parts by weight of 2.5% by weight ammonium bromide aqueous solution and 1% by weight hypochlorous acid
Mixed solution in which 170 parts by weight of aqueous sodium acid solution was mixed immediately before addition
The method for adding an oxidizing disinfectant to each addition point was determined automatically at each addition point at each addition point by the following procedure. In addition, before starting the papermaking, each system is free of dirt and other deposits, and the raw material NBKP, LBKP, the recovered raw material in the recovered raw material tank 17 and the ORP value of the stored water in the primary treated water tank are positive. Was confirmed in advance. The temporal transition of the ORP in this example is as shown in FIGS.

  The ORP value at each ORP measurement point at the start of paper making (before the addition of the oxidizing disinfectant) is determined as a reference value, and the standard addition time (15 minutes) at this time is set in the control unit. This standard addition time is set based on the results of a sterilization test conducted using samples sampled in advance to the same ORP value.

  The addition of the oxidizing disinfectant was performed 4 times per day (about every 6 hours) (FIG. 2 (a)). Two days after the start of papermaking, a trend toward a decrease in the baseline of the ORP value began to be observed. Since the decreasing tendency became more remarkable from the latter half of the fourth day, the drug addition time was extended to 20 minutes. The extension of the addition time was carried out until the seventh day when the baseline was restored. Thereafter, the addition time was again returned to 15 minutes (FIG. 2 (b)).

  As described above, in the treatment to which the present invention was applied, it was possible to operate stably without causing defects or paper breaks until the 15th day (FIGS. 2C and 2D).

  The time course of the ORP was measured with a white water silo in the fine paper making water system, but the same control was performed at the other two locations.

Comparative Example 1
The slime control treatment was performed in the same manner as in Example 1 except that the addition of the oxidizing bactericidal agent was performed four times per day from the start of papermaking to the 15th day without extending the drug addition time as in Example 1. As a result, as shown in FIGS. 3 (a) to 3 (d), a decreasing tendency of the ORP baseline was observed from the seventh day, and the decreasing tendency became more remarkable from the ninth day. From the 10th day, the slime-derived defects frequently occur in the products.

  As is apparent from the above results, the process of applying the present invention avoids a decrease in the ORP standard value that was observed during the conventional process, and as a result, there are no defects or paper breaks in the operation status, resulting in productivity and The effect of quality improvement was obtained.

It is a systematic diagram which shows the quality paper papermaking aqueous system which performed the slime control process in Example 1 and Comparative Example 1. 3 is a graph showing a temporal transition of ORP in Example 1. 6 is a graph showing a temporal transition of ORP in Comparative Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Broke tank 2 NBKP (hardwood bleached kraft pulp) tank 3 LBKP (softwood bleached kraft pulp) tank 4 Mixing chest 5 Machine chest 6 Seed box 9 Inlet 10 Wire part 11 Press part 12 Water tank 13 White water silo 14 Seal pit 15 Collection device 16 Primary treated water tank 17 Recovered material tank 20 Control unit 21, 22, 23 ORP meter 30 Chemical injection equipment

Claims (3)

In an aqueous system where slime control is performed by adding an oxidizing disinfectant, a method for determining the slime control effect,
Determining the redox potential over time by continuously or intermittently measuring the redox potential at at least one location of the aqueous system; and
When the time course of the oxidation-reduction potential tends to decrease, the step of determining that the slime formation effect is present due to insufficient slime control effect;
A method for determining a slime control effect, comprising:   The determination method according to claim 1, wherein a redox potential is measured at a plurality of locations in the water system.   In the method of performing slime control by adding an oxidizing disinfectant to an aqueous system, the amount of the oxidizing disinfectant added when it is determined by the determination method according to claim 1 or 2 that there is a slime forming environment. The slime control method characterized by increasing the amount.

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