JPH05277491A - Water system treatment method - Google Patents

Abstract

PURPOSE:To ensure that a water treatment agent for inhibition of metal corrosion or scale generation is maintained at an optimal water treatment density for inhibition of metal corrosion or scale generation by measuring the density directly and rapidly with ease and accuracy. CONSTITUTION:The density of a water treatment agent is controlled by adding a water treatment agent which is itself a fluorescent molecule to a held water and measuring an intensity of fluorescence in a water system treatment method for inhibiting metal corrosion or scale generation in the water system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water treatment method for preventing metal corrosion or scale in a water system such as a cooling water system, a boiler system, a hot water system, a brine system and a dust collection water system.

[0002]

2. Description of the Related Art Various corrosion inhibitors, scale inhibitors and dispersants are used to prevent metal corrosion or scale in an aqueous system. These water treatment agents cannot exert sufficient effects unless the concentration in water is maintained within a certain range. In practice, the concentrations of these water treatment agents in water are measured, and operation is performed while confirming that the water treatment agents are maintained at appropriate concentrations. At this time, as a method for measuring the concentration of the water treatment agent, it is general to focus on a specific atom or a specific functional group in the water treatment agent and measure the concentration. For example, in a water treatment agent containing a heavy metal, the objective can be achieved by measuring the concentration of the heavy metal, and in a phosphoric acid-based water treatment agent such as organic phosphoric acid or polymerized phosphoric acid, sample water is used as an oxidizing agent and an oxidizing agent. After boiling in the coexistence of an acid to convert the contained phosphorus atoms into phosphate ions,
A method for colorimetric analysis by the molybdenum blue method (for example, Japanese Industrial Standard JIS K0101) is implemented. But,
All of these methods are complicated in operation and require time. In industrial water systems, the measured value of the water treatment agent concentration is an important operating guideline, and therefore a particularly quick response is desired.

As a remedy for this, a method of adding a fixed proportion of a lithium salt as a tracer to a water treatment agent (Japanese Patent Publication Sho
55-3668), a method of adding a fixed ratio of a fluorescent substance to a water treatment agent as a tracer (Japanese Patent Laid-Open No. 2-115093). However, in the method using such a tracer, since the tracer and the water treatment agent are only mixed, the behavior in the water system is not the same, and for example, only the water treatment agent is consumed in the system due to precipitation, adsorption, etc. In that case, the true water treatment agent concentration will not be obtained even if the water treatment concentration is calculated from the tracer concentration.

[0004]

The object of the present invention is to measure the concentration of a water treatment agent directly, quickly, simply and accurately,
An object of the present invention is to provide a water treatment method capable of maintaining an optimum water treatment agent concentration that prevents metal corrosion or scale.

[0005]

Means for Solving the Problems The present inventor directly and quickly, simply and accurately measures the concentration of such a water treatment agent,
As a result of intensive studies to develop a water treatment method for maintaining an optimum water treatment concentration, it was found that the purpose can be achieved by using a water treatment agent which is itself a fluorescent molecule. The present invention has been completed based on the findings.

That is, the present invention relates to an aqueous treatment method for preventing metal corrosion or scale in an aqueous system,
It is possible to control the concentration of the water treatment agent by injecting a water treatment agent which is itself a fluorescent molecule (hereinafter referred to as “fluorescent water treatment agent”) into the water held and measuring the fluorescence intensity. The present invention relates to a characteristic water treatment method.

The fluorescent water treatment agent used in the present invention is itself a fluorescent molecule and has an action of preventing metal corrosion or scale. Here, the fluorescent molecule is a molecule that absorbs light and emits fluorescence, and examples thereof include an organic compound containing a structural unit in which two or more rings are conjugated with π electrons.

The π-electron conjugated system may form a conjugated system by, for example, condensing two or more rings, or 2
One or more rings may form a conjugated system via a conjugated bond (for example, a conjugated double bond) or a lone electron pair. When the organic compound has such a structural unit, the organic compound can emit fluorescence.

The method for producing a fluorescent water treatment agent of the present invention can be achieved by introducing the above structural unit into a compound known as a water treatment agent. For example, acrylic acid, maleic acid, unsaturated carboxylic acids such as itaconic acid and 2-acrylamido-2-methylpropanesulfonic acid, styrenesulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid,
A polymer containing an unsaturated sulfonic acid such as a conjugated diene sulfone compound is known as a water treatment agent, but it is preferable to copolymerize these unsaturated carboxylic acid and / or unsaturated sulfonic acid with a fluorescent vinyl monomer. Thus, a fluorescent water treatment agent can be manufactured. Examples of the fluorescent vinyl monomer in this case include vinylcarbazole, vinylnaphthalene, vinylanthracene, vinylacridine, acenaphthylene, and the like. Further, a fluorescent compound having a hydroxyl group and / or an amino group, which will be described later, may be reacted with a reactive monomer such as glycidyl methacrylate, allyl glycidyl ether and acrylic acid chloride to give a fluorescent vinyl monomer.

Examples of the polymerization initiator include radical polymerization initiators (specifically, peroxy compounds and the like). In addition, at the time of copolymerization, a polymer chain end blocking agent (specifically, thioglycolic acid ester or the like) may be added as an additive. Although the polymerization conditions are appropriately selected, for example, the polymerization temperature is 50 to 150 ° C. and the polymerization time is 1 to 10 hours. In the copolymer composition, 100 parts by weight of the total amount of unsaturated carboxylic acid and unsaturated sulfonic acid, fluorescent vinyl monomer 0.1 ~ 30
The amount of the polymerization initiator may be 0.05 to 10 parts by weight. The copolymer obtained as described above may be block or random. Weight average molecular weight in the physical properties of the copolymer
500 to 50,000 is preferable.

The fluorescent water treatment agent used in the present invention can also be produced by directly reacting a compound known as a water treatment agent with a fluorescent compound to modify the water treatment agent. That is, a functional group (eg, an acid anhydride group, a carboxylic acid group, a sulfonic acid group, a free ester group, a hydroxyl group, an isocyanate group, an amino group, etc.) capable of binding to an appropriate functional group in a molecule of a known water treatment agent ( For example, with a fluorescent compound having a hydroxyl group, an amino group, an isocyanate group, an epoxy group, etc.), a fluorescent compound is introduced into the molecule by modifying the above-mentioned known water treatment agent, and thus the known water treatment agent is fluorescent. It can be used as a water treatment agent. As an example of this, a maleic anhydride polymer (including a copolymer) is reacted with a fluorescent compound having a hydroxyl group or an amino group in a non-aqueous solvent, and at least a part of the acid anhydride group in the polymer is reacted. A fluorescent water treatment agent can be obtained by introducing a fluorescent compound by esterification, amidation and / or imidation. Here, as a preferred example of the fluorescent compound having a hydroxyl group and / or an amino group, at least one hydroxyl group and / or
Or, an organic compound having an amino group and having two or more rings forming a π-electron conjugated system can be given. Examples of such a compound include derivatives such as fluorescein, carbazole, acridine, and acridone, or a hydroxyl group and / or Examples include derivatives of naphthalene, anthracene, perylene, fluorein, stilbene, coumarin and the like, which have an amino group as a substituent. When these sulfonic acid derivatives are used as the fluorescent compound here, the sulfonic acid group is introduced into the polymer, so that the scale dispersion effect is improved. When introducing a fluorescent molecule into a compound known as a water treatment agent,
The mixing ratio of the fluorescent molecule is not particularly limited, but it is important not to impair the original function of the water treatment agent, and for that purpose, it is about 0.1 to 40% by weight.

In the physical properties of the modified polymer obtained as described above, a weight average molecular weight of 500 to 50,000 is preferable.

Further, after a compound having a condensed ring such as naphthalene and anthracene is sulfonated in the presence of sulfuric acid,
Since the condensation polymer obtained by reacting with formalin, methylal, chloral, etc. has a scale-dispersing action and exhibits a strong fluorescence intensity, it can be used as it is as a fluorescent water treatment agent in the present invention.

The condensation polymer obtained as described above preferably has a weight average molecular weight of 500 to 50,000.

The fluorescent water treatment agent according to the present invention is continuously or intermittently added in order to maintain a sufficient concentration at which corrosion or scale inhibition can be achieved. The amount of the fluorescent water treatment agent according to the present invention is usually 0.1 to 1000 ppm,
Particularly, 0.5 to 500 ppm is preferable.

The fluorescent water treatment agent according to the present invention can be used in combination with other known water treatment agents. Examples of water treatment agents include phosphonic acid, acrylic acid and / or polymers of maleic acid and hypophosphorous acid, inorganic phosphates, zinc salts,
Examples thereof include molybdate, acrylic acid-based polymers and copolymers, maleic acid-based polymers and copolymers, and azoles. These water treatment agents may be used in advance by mixing with the water treatment agent of the present invention. In addition, in the treatment method of the present invention, compounds known as slime control agents may be added as additives.

The fluorescence intensity of the treated water containing the fluorescent water treatment agent can be measured by using a commercially available fluorescence photometer or a spectrofluorometer. Specifically, a filter or spectroscope is installed in the direction perpendicular to the excitation light by irradiating the glass cell containing the treated water with the excitation light and causing the emitted light to emit light, and a wavelength of a certain region is extracted to obtain a photodetector. To measure the fluorescence intensity. The measurement wavelength of the fluorescence intensity is usually the wavelength at which the fluorescence intensity is maximum by the measurement of the fluorescence spectrum, for example 250 to 850 nm
Is preferably selected. The excitation side wavelength is, for example, 200 to 4
It is preferable to select a wavelength of 00 nm at which the scatter wavelength of the excitation light and the fluorescence measurement wavelength do not overlap. Further, by selecting the excitation wavelength, it is possible to adjust the fluorescence intensity or remove the influence of the interfering component without diluting the treated water. For the water to which a known concentration of the fluorescent water treatment agent has been added, the relationship between the concentration and the fluorescence intensity (that is, the concentration-fluorescence intensity calibration curve) is obtained in advance, so that the fluorescence intensity of the treated water is included in the treated water. The concentration of the fluorescent water treatment agent present can be easily converted. Batch the fluorescent water treatment agent so that the concentration of the fluorescent water treatment agent can be maintained at a concentration sufficient to achieve corrosion inhibition or scale inhibition, or
Alternatively, the stroke of the fluorescent water treatment agent infusion pump is adjusted. By continuously passing the treated water through the cell for measuring fluorescence, the concentration of the fluorescent water treatment agent can be continuously monitored. Also, the concentration of the fluorescent water treatment agent is automatically controlled by sending the output signal from the fluorescence photometer or the fluorescence spectrophotometer to the controller and operating the water treatment agent injection pump by the operation output from the controller. You can

[0018]

[Function] A water treatment agent which is a fluorescent molecule itself and has an action of preventing metal corrosion or scale. The fluorescent molecule and the water treatment agent are not mixed but are combined and combined, Even when the agent is consumed in the system due to precipitation, adsorption, etc., the consumption and the decrease in fluorescence intensity always match,
Therefore, the true concentration of the water treatment agent can always be obtained only from the fluorescence intensity.

[0019]

EXAMPLES The present invention will be specifically described below, but the present invention is not limited to these examples.

(1) Production of water treatment agent Polymer A: 18 g of acrylic acid and N- in a 500 ml five-necked flask.
2 g of vinylcarbazole and 80 ml of isopropanol were added, and a cooling pipe, a stirrer, a thermometer, a nitrogen introducing pipe and a dropping funnel were attached. After heating the solution to 60 ° C while flowing nitrogen, a solution of 0.25 g of 2-ethylhexyl thioglycolate dissolved in 10 ml of isopropanol, and then a solution of 1.0 g of t-butylperoxypivalate dissolved in 10 ml of isopropanol were added dropwise. It was dripped from the funnel. The mixture was heated at reflux at 80 ° C for 5 hours. After distilling off isopropanol, 50 g of water and 20.0 g of 50% sodium hydroxide were added to obtain an aqueous solution. After filtering the insoluble matter, an aqueous solution of a reactant having a solid content of 34.9%, a pH of 5.7, and a Brookfield viscosity of 154 cp at 20 ° C. was obtained. The reactant aqueous solution was added to methanol to precipitate a polymer, which was dried to obtain a polymer A. The weight average molecular weight of the polymer A is about
It was 5,000. The fluorescence spectrum of polymer A is shown in FIG. The excitation wavelength at this time was 264 nm. FIG. 2 shows the relationship between the concentration of polymer A and the fluorescence intensity. The maximum fluorescence wavelength at the excitation wavelength of 264 nm was 363 nm.

Polymer B: Maleic anhydride-styrene copolymer (copolymerization ratio 1: 1 mol, in a 500 ml three-necked flask,
A molecular weight of 1600) 10.1 g, potassium 2-naphthol-6,8-disulfonate 4.76 g, dioxane 110 ml, and acetic acid 1.5 g were added. The flask was equipped with a condenser, a stirrer, and a thermometer.
The mixture was heated at 100 ° C. under reflux for 3.5 hours. After distilling off dioxane, 70 g of water and 11.3 g of 50% sodium hydroxide were added,
The unreacted maleic anhydride unit in the copolymer was hydrolyzed to give an aqueous solution. After the insoluble matter in the reaction aqueous solution was removed by filtration, the mixture was added to methanol to precipitate a polymer, which was dried to obtain a polymer B. FIG. 3 shows the fluorescence spectrum of a 100 ppm aqueous solution of polymer B. The excitation wavelength at this time is 259n
It was m. FIG. 4 shows the relationship between the concentration of the polymer B and the fluorescence intensity. At this time, the excitation wavelength was 259 nm and the fluorescence wavelength was 460 nm.

(2) Evaluation of corrosion prevention effect Rolled steel for general structure with a thickness of 1 mm (Japanese Industrial Standard JIS
From SPCC), cut into a disc with an outer diameter of 50 mm, and 8 mm at the center
The test piece was provided with a hole for fixing and fixing. After removing stains on the surface of the test piece, the entire surface was polished with No. 400 polishing paper, washed and degreased with acetone, dried, and accurately weighed to 0.1 mg. Using test water of Yokkaichi City, polymer A was added to 500 ml of the test water, and the test piece was immersed and kept at 40 ° C. for 18 hours while rotating at 100 rpm. After the test, it was weighed accurately to 0.1 mg. The corrosion weight loss was determined by comparing the weights of the test pieces before and after the test. The results are shown in Table 1.

[0023]

[Table 1]

From these results, it was confirmed that the polymer A achieves significant corrosion inhibition.

(3) Evaluation of scale preventive effect on calcium carbonate Calcium hardness 370 ppm, H ₂ CO ₃ 360 ppm by dissolving calcium chloride and sodium hydrogen carbonate in deionized water.
Test water (as CaCO ₃ ) was prepared. The water treatment agents shown below were added to the test water, and the pH of the test water was adjusted to 8.6 with sodium hydroxide. Put the test water in a closed container and leave it in a constant temperature bath at 50 ° C for 18 hours, then filter the test water with a quantitative filter paper No. 6 to determine the calcium hardness in the filtrate by ED.
It was measured by the TA titration method (Japanese Industrial Standard JIS-K0101). The scale inhibition rate was calculated by the following formula.

Scale inhibition rate (%) = 100 × (CI-C
B) / (CS-CB) where CS: calcium concentration before heating and holding CB: calcium concentration after heating and holding without addition of water treatment agent CI: calcium concentration after heating and holding when water treatment agent is added

At the same time, the fluorescence intensity of the filtrate was measured, and the treatment agent concentration was determined from the relationship between the concentration and the fluorescence intensity prepared in advance. The results are shown in Table 2.

[0028]

[Table 2]

From Table 2, from the measurement of the fluorescence intensity, the polymer A
It was observed that the residual concentration in water decreased due to adsorption to crystalline particles, and the maximum scale prevention effect was obtained by controlling the residual concentration of Polymer A within the range of 6.1 to 12.9 ppm as an operating condition of the water system. It turned out to be obtained. On the other hand, in the comparative example, the concentration of the treating agent measured by the fluorescence intensity shows the concentration added, and the true residual concentration of the polymer could not be known.

(4) Evaluation of Scale Preventing and Dispersing Effect on Calcium Phosphate A water treatment agent was added to deionized water, and calcium chloride and trisodium phosphate were further dissolved to obtain pH 11.6 and Ca hardness 1000 pp.
Test water of m, PO ₄ 900 ppm was prepared. The test water was placed in a closed container and allowed to stand in a constant temperature bath at 70 ° C. for 24 hours, and then the test water was thoroughly stirred to measure the transmitted light turbidity (Japanese Industrial Standard JIS-K0101). The scale inhibition rate was calculated by the following formula.

Scale inhibition rate (%) = 100 × (TB−TI) / TB where TB: Turbidity when no water treatment agent is added TI: Turbidity when water treatment agent is added

Then, after allowing the test water to stand for 2 hours, the transmitted light turbidity of the supernatant was measured in the same manner. The scale dispersion rate was calculated by the following formula.

Scale dispersion rate (%) = 100 × TD / TI where TD: turbidity of supernatant after standing for 2 hours

Further, the fluorescence intensity of the filtrate obtained by filtering the test solution was measured, and the concentration of the fluorescent substance was determined from the relationship between the concentration prepared in advance and the fluorescence intensity. The results are shown in Table 3.

[0035]

[Table 3]

Polymer B is a reaction product of a maleic anhydride-styrene copolymer and 2-naphthol-6,8-disulfonic acid, and has a large scale-inhibiting effect, and the residual concentration in water is traced by fluorescence intensity. I knew I could do it. In the comparative example, the polymer and 2-naphthol-6,8-disulfonic acid were used as a simple mixture, but the scale preventing effect and the scale dispersing effect are not sufficient. The fluorescence intensity decreased, which indicates that the fluorescent substance 2-naphthol-6,8-disulfonic acid was adsorbed and the residual concentration in the system decreased. Therefore, the measurement of the fluorescence intensity has nothing to do with the polymer concentration and has no meaning.

[0037]

Industrial Applicability The water treatment method of the present invention is capable of directly, quickly, simply and accurately measuring the concentration of a water treatment agent for preventing corrosion or scale of a water system containing cooling water or the like, and corroding metal or scale. It is possible to maintain the optimum concentration of the water treatment agent for preventing the above, and it is effective in prolonging the life of the equipment material and stabilizing the operation.

[Brief description of drawings]

FIG. 1 is a fluorescence spectrum diagram of a polymer A in an example.

FIG. 2 is a correlation diagram between the concentration of polymer A and the fluorescence intensity in Examples.

FIG. 3 is a fluorescence spectrum diagram of a polymer B in an example.

FIG. 4 is a correlation diagram between the concentration of polymer B and the fluorescence intensity in Examples.

Claims (2)

[Claims] 1. In a water treatment method for preventing metal corrosion or scale in a water treatment system, a water treatment agent which itself is a fluorescent molecule is injected into retained water and the fluorescence intensity is measured to measure the water treatment agent. Water treatment method characterized by controlling concentration 2. The water-based treatment method according to claim 1, wherein an organic compound containing a structural unit in which two or more rings are conjugated with π electrons is used as a fluorescent molecule.