JP2009195823A - Method of controlling concentration of aqueous treating agent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of controlling the concentration of an aqueous treating agent by which a combined chlorine agent used as an aqueous treating agent can effectively be used. <P>SOLUTION: In the method of controlling the concentration of the aqueous treating agent, the amount of the combined chloride of a water system is controlled by producing free chloride in the water system. The free chloride is produced in the water system and, thereby, can react again with a chlorine stabilizing agent remaining in the water system by itself to form the combined chlorine agent. As the result, the combined chlorine agent can be effectively utilized as the aqueous treating agent. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for controlling the concentration of an aqueous treatment agent. More specifically, the present invention relates to a technique for controlling the concentration of an aqueous treatment agent for performing aqueous sterilization.

  In plant cooling water systems, wastewater treatment water systems, steel water systems, paper pulp water systems, cutting oil water systems, etc. in various factories, slime and the like are generated in the water systems due to bacteria, filamentous fungi, algae, and the like. This slime or the like causes troubles such as a decrease in thermal efficiency, blockage of water passage pipes, corrosion of pipe metal materials, and the like.

  In order to prevent such an obstacle, a combined chlorine agent (stabilized chlorine agent) is used as a slime control agent or the like in a cooling water system or the like. The bound chlorine agent remains as a chlorine stabilizer when consumed in the aqueous system. However, the consumption rate of the combined chlorine agent in the water system varies depending on the cooling water load and the surrounding environment. For this reason, it may be difficult to maintain a stable concentration even if the injection amount of the combined chlorinating agent is controlled by a batch timer or the proportion of makeup water.

  For example, in Patent Document 1, hydrazine is contained in cooling water in the first stage, and (a) hypochlorous acid or a salt thereof, (b) hypobromite or the like, as related to a cooling water-based slime peeling treatment. A technique for containing a salt or the like in cooling water is disclosed.

  In addition, so-called multi-drugs that are used in combination with scale inhibitors, anticorrosives, slime control agents, and the like are also used as water treatment agents. If control is performed to maintain the concentration of the slime control agent component, excessive injection of other components may occur.

JP2004-012042A.

  As described above, in a system where the consumption amount of bound chlorine is large, the detected concentration in the aqueous system tends to be lower than the actual addition amount. Therefore, in order to ensure an effective detection concentration, the amount of the drug added is increased. However, this increases costs, and the bound chlorine agent consumed in the aqueous system remains in a large amount as a chlorine stabilizer. .

  Therefore, the main object of the present invention is to provide a method for controlling the concentration of an aqueous treatment agent that can effectively use a combined chlorine agent.

First, the present invention provides a method for controlling the concentration of an aqueous treatment agent that generates free chlorine in an aqueous system and controls the amount of bound chlorine in the aqueous system. By generating free chlorine in the aqueous system, it can be combined with a chlorine stabilizer remaining in the aqueous system to form combined chlorine. As a result, the combined chlorine agent can be effectively used.
And it is desirable to control the combined chlorine concentration by controlling the free chlorine concentration in the aqueous system. By controlling the free chlorine concentration in the aqueous system within a certain range, the combined chlorine concentration can be controlled more accurately. The free chlorine concentration in the aqueous system is desirably 0.05 mg-Cl / L or more.
Free chlorine can be generated by adding at least one of hypochlorous acid, chlorous acid, chlorine dioxide, and chlorine gas to the aqueous system.

  According to the method for controlling the concentration of an aqueous treatment agent according to the present invention, a combined chlorine agent can be used effectively.

  The present invention will be described below. In addition, the following description shows the representative example concerning this invention, and the range of this invention is not interpreted narrowly by this.

  The method for controlling the concentration of an aqueous treatment agent according to the present invention at least performs the control of the amount of combined chlorine in the aqueous system by generating free chlorine in the aqueous system. By generating free chlorine in the aqueous system, it can be combined with the chlorine stabilizer remaining in the aqueous system. Thereby, combined chlorine can be regenerated. In the present invention, it is only necessary to generate free chlorine in the water to be treated, and at least free chlorine remains in the aqueous system at a predetermined concentration or more, so that it can be efficiently regenerated as bound chlorine. Hereinafter, these will be described in more detail.

First, bound chlorine will be described.
Although the kind of combined chlorine which can be used in the present invention is not limited, for example, chloramine-T (a sodium salt of N-chloro-4-methylbenzenesulfonamide), chloramine-B (sodium of N-chloro-benzenesulfonamide) Salt), sodium salt of N-chloro-paranitrobenzenesulfonamide, trichloromelamine, sodium salt or potassium salt of mono- or di-chloromelamine, sodium salt of trichloro-isocyanurate, mono- or di-chloroisocyanuric acid or Examples include potassium salt, sodium salt or potassium salt of mono- or di-chlorosulfamic acid, monochlorohydantoin, 1,3-dichlorohydantoin, or a 5,5-alkyl derivative thereof.

  Bound chlorine can be generated by combining a chlorine stabilizer and free chlorine. The chlorine stabilizer is not particularly limited as long as it has an effect of stabilizing the chlorine. Examples thereof include sulfamic acid and hydantoin. In particular, sulfamic acid compounds are highly safe because they are not toxic like hydrazine.

  Examples of such a sulfamic acid compound include N-methylsulfamic acid, N, N-dimethylsulfamic acid, N-phenylsulfamic acid and the like. Among the sulfamic acid compounds used in the present invention, examples of the salt of the compound include alkali metal salts such as sodium salt and potassium salt, alkaline earth metal salts such as calcium salt, strontium salt and barium salt, manganese salt and copper Other metal salts such as salts, zinc salts, iron salts, cobalt salts, nickel salts, ammonium salts, guanidine salts, etc., specifically, sodium sulfamate, potassium sulfamate, calcium sulfamate, sulfamine Examples include strontium acid, barium sulfamate, iron sulfamate, and zinc sulfamate. The sulfamic acid and these sulfamic acid salts can be used alone or in combination of two or more.

  For example, when free chlorine and sulfamic acid coexist in an aqueous system, they can be combined in the aqueous system to become a chlorosulfamic acid compound and regenerated as bound chlorine. For example, when a chlorinated oxidant and a sulfamic acid compound, or a chlorosulfamic acid-based combined chlorinating agent composed of a chlorinated oxidant and a sulfamic acid compound is coexisted in the water to be treated, a wide pH range covering an acidic range to an alkaline range. Even so, there is a feature that the free chlorine concentration in the water to be treated does not change greatly.

  It does not limit as a method of producing | generating free chlorine in an aqueous system, What is necessary is just to be able to produce | generate free chlorine in an aqueous system. For example, a method of injecting a drug into an aqueous system, a method of generating hypochlorite ions using an electrolytic reaction such as a saline solution or an aqueous potassium chloride solution, and the like can be mentioned.

  Examples of drugs that can be used when generating free chlorine by chemical injection include hypochlorous acid or its salt, chlorous acid or its salt, chloric acid or its salt, perchloric acid or its salt, chlorinated isocyanuric An acid or its salt, chlorine gas, chlorine dioxide, etc. are mentioned. More specific salts include alkali metal hypochlorites such as sodium hypochlorite and potassium hypochlorite, and alkaline earth metal hypochlorites such as calcium hypochlorite and barium hypochlorite. Salts, alkali metal chlorites such as sodium chlorite and potassium chlorite, alkaline earth metal chlorites such as calcium chlorite and barium chlorite, and other chlorites such as nickel chlorite Examples include acid metal salts, alkali metal chlorates such as ammonium chlorate, sodium chlorate and potassium chlorate, and alkaline earth metal chlorates such as calcium chlorate and barium chlorate.

  These chlorine-based oxidizing agents may be used alone or in combination of two or more. Of these, hypochlorite can be preferably used because it is easy to handle.

  When producing free chlorine, it is desirable to produce it according to the concentration of the chlorine stabilizer remaining in the aqueous system. The remaining chlorine stabilizer and free chlorine are combined to form combined chlorine, but the surplus can be detected as free chlorine. By controlling the concentration of this free chlorine within a certain range, it is possible to efficiently realize regeneration of bound chlorine.

  Preferably, the amount of bound chlorine is controlled based on the free chlorine concentration in the aqueous system. Excess free chlorine can be detected in real time by generating free chlorine from the outside in an aqueous system in which the chlorine stabilizer can remain, and by continuously monitoring the free chlorine concentration. Thereby, the amount of combined chlorine can be controlled in real time, and excessive injection of combined chlorine can be effectively prevented.

  Further, if necessary, a control means for measuring the concentration of free chlorine in the aqueous system and adjusting the amount of free chlorine in the aqueous system based on this measured value may be additionally provided. Thereby, water quality management of a water system can be performed continuously. The control means is not particularly limited, and the amount of free chlorine can be controlled by, for example, performing chemical injection based on the measured chlorine concentration.

  In this case, the method for measuring the concentration of free chlorine in the aqueous system is not limited. For example, a method for measuring the chlorine concentration by polarography, absorptiometry, DPD (N, N-diethylphenylenediamine) method, Examples include a method of measuring an oxidation-reduction potential (ORP) in an aqueous system and estimating a free chlorine concentration based on this oxidation-reduction potential. Based on the free chlorine concentration value thus obtained, the amount of free chlorine can be adjusted so as to obtain a target free chlorine concentration value.

  A preferable lower limit of the free chlorine concentration in the aqueous system is 0.05 mg-Cl / L or more, more preferably 0.1 mg-Cl / L or more, still more preferably 0.4 mg-Cl / L or more according to the ORP method. It is desirable that By setting it as this free chlorine density | concentration, it can be combined more efficiently with the chlorine stabilizer remaining in the aqueous system. As a result, bound chlorine can be regenerated more efficiently. On the other hand, the upper limit of the free chlorine concentration is preferably 1 mg-Cl / L or less from the viewpoint of preventing corrosion of metals in the aqueous system.

  Furthermore, when it is desired to control the above-mentioned combined chlorine concentration in the aqueous system, the combined chlorine concentration in the aqueous system is also measured, and the amount of combined chlorine in the aqueous system is adjusted based on both the measured free chlorine concentration and the combined chlorine concentration. Also good. By monitoring not only the free chlorine concentration but also the combined chlorine concentration, the amount of combined chlorine to be regenerated can be grasped more accurately, and the water quality can be managed with high accuracy and continuously.

  As a suitable bound chlorine concentration in the aqueous system, the lower limit value is preferably 0.1 mg-Cl / L or more, and the upper limit value is preferably 50 mg-Cl / L or less. The bound chlorine concentration in this case is measured by the DPD method.

A chlorine stabilizer can be generated by depleting bound chlorine in an aqueous system, but in the present invention, free chlorine can be regenerated as bound chlorine by reacting with a chlorine stabilizer. This makes it possible to effectively use the chlorine stabilizer and prevent the chlorine stabilizer and the like from accumulating in the aqueous system.
Further, since the combined chlorine can be regenerated from the chlorine stabilizer, it is not necessary to be affected by the consumption rate of the combined chlorine in the aqueous system. For this reason, the detection concentration of the combined chlorine can be stabilized and the detection concentration can be improved. As a result, a stable water treatment effect can be obtained.
And since the detection density | concentration of a combined chlorine can be improved, the addition amount of a chemical injection can also be reduced. In particular, when a multi-drug is used as an aqueous treatment agent, it is possible to prevent excessive injection or excessive residual of other components due to an increase in the amount of drug added.

  The treatment target to which the concentration control method of the water-based treatment agent according to the present invention can be applied is not particularly limited. For example, plant cooling water systems, scrubbers, waste water treatment water systems, waste water treatment water systems, steel water systems, cutting oil water systems, etc. The slime composition adhering to these devices, water pipes and the like can be peeled off.

  As an aqueous system, it can use suitably for a circulating water system. When the circulating water system is operated for a long period of time, a large amount of chlorine stabilizer tends to remain in the water system. However, according to the present invention, it is preferable because combined chlorine can be regenerated from the chlorine stabilizer. Furthermore, an open circulating cooling water system or the like is suitable. For example, bacteria such as Legionella bacteria are liable to be generated in an aqueous system under such conditions because the water temperature of an open circulation cooling tower or the like, particularly an environment surrounded by algae generated in the cooling tower, is preferred. The present invention can effectively control the concentration of the water-based disinfectant particularly for an open circulation cooling water system and the like over a long period of time.

  Hereinafter, the present invention will be described more specifically with reference to examples, and effects of the present invention will be verified.

[Example]
Verification was performed using the apparatus shown in FIG. FIG. 1 is an example of a system diagram of an open circulating cooling water system used for explaining the concentration control method for an aqueous treatment agent of the present invention. In this open circulation cooling water system, the cooling tower 1 is supplied to the heat exchanger 3 via the cooling water pipe forward path 2 and the pump P, and the return water is returned to the cooling tower 1 via the cooling water pipe return path 4. The cooling tower 1 was operated at a refrigeration scale of 400 RT, a retained water amount of 30 m ³ , and a concentration factor of 5 times. The cooling tower 1 includes a fan F, and air-conditioning cooling water W is stored. The free chlorine concentration of the cooling water W for air conditioning is measured by the sensor S and controlled by the free chlorine agent control unit 5 and the combined chlorine agent control unit 6. The free chlorine agent control unit 5 includes a chemical injection tank 51 and a chemical injection port 52. The combined chlorine agent control unit 6 includes a chemical injection tank 61 and a chemical injection port 62. Based on the free chlorine concentration measured by the sensor S, the chemical injection of the free chlorine agent and the combined chlorine agent is controlled.

Control of free chlorine was performed by injecting hypochlorite. This was performed using chlorosulfamic acid as a combined chlorine agent (stabilized chlorine agent).
The combined chlorine agent (chlorosulfamic acid) in the aqueous system was added so as to have a ratio of 15 mg-Cl / L with respect to the cooling water blow water amount. The amount of chemical administration was controlled using an ORP electrode so that free chlorine in the aqueous system was always 0.5 mg-Cl / L. In addition, the density | concentration of the combined chlorine agent was measured by DPD method.
The exfoliated slime was naturally discharged by blowing depending on concentration, and no special removal such as cleaning was performed. Thus, it was made to operate continuously and the change over time of the combined chlorine agent concentration and free chlorine concentration in the aqueous system was measured. The results are shown in Table 1.

[Comparative example]
The combined chlorine agent (chlorosulfamic acid) in the aqueous system was only added so as to have a ratio of 15 mg-Cl / L with respect to the cooling water blow water amount, and the free chlorine concentration was not controlled. The other points were continuously operated under the same conditions as in the example. The results are shown in Table 1.

[Discussion]
The example was able to maintain a higher combined chlorine concentration than the comparative example. In particular, the combined chlorine concentration increased as the operating days increased, and the transition of the combined chlorine concentration suggested that the combined chlorine was regenerated in the water system. As a result, it was shown that the detected concentration close to the added concentration of the combined chlorine agent can be maintained in the examples.
On the other hand, the comparative example had a low combined chlorine concentration throughout the operation period. In the comparative example, free chlorine was not generated in the aqueous system, so it seems that the combined chlorine was not regenerated.
From the above, according to the present invention, it has been shown that the concentration control of the combined chlorine agent and the regeneration of the exhausted combined chlorine are possible, and a stable water treatment effect can be exhibited.

It is an example of the systematic diagram of the open circulation cooling water system with which it uses for description of the density | concentration control method of the aqueous processing agent of this invention.

Explanation of symbols

1 Cooling Tower 2 Cooling Water Pipe Outbound 3 Heat Exchanger 4 Cooling Water Pipe Return 5 Free Chlorine Control Unit 6 Combined Chlorine Control Unit P Pump F Fan

Claims (4)

  A method for controlling the concentration of an aqueous treatment agent that generates free chlorine in an aqueous system and controls the amount of bound chlorine in the aqueous system.   The method for controlling the concentration of an aqueous treatment agent according to claim 1, wherein the amount of the combined chlorine is controlled by controlling the concentration of free chlorine in the aqueous system.   The method for controlling the concentration of an aqueous treatment agent according to claim 1 or 2, wherein the free chlorine concentration in the aqueous system is 0.05 mg-Cl / L or more.   The said free chlorine is produced | generated by adding at least any one of hypochlorous acid, chlorous acid, chlorine dioxide, and chlorine gas to the said water system. 4. A method for controlling the concentration of the aqueous treatment agent according to 1.