JPH07159583A - Water quality analyzing method and device therefor - Google Patents

Abstract

PURPOSE:To analyze sodium ions in the feed water of a power plant with high accuracy. CONSTITUTION:Oxygen is fed to the sample water collected from the feed water of a power plant by an oxygen feeding device 1, and ultraviolet rays are radiated to decompose ammonia in the sample water. Cations in the sample water are concentrated by a concentrating device 3, and sodium ions in the sample water are analyzed by a cation ion chromatograph 4. Since the sample water is oxidation-treated, the ammonia concentration in the sample water is reduced, the peak of ammonia ions and the peak of sodium ions are separated, and the sodium ions can be analyzed with high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for analyzing water quality of sample water, and more particularly to a method and apparatus for analyzing water quality suitable for analyzing sample water whose water quality is adjusted by a volatile treatment method.

[0002]

2. Description of the Related Art In a power plant operated under high-temperature and high-pressure steam conditions, most of the system equipment and piping are made of steel. Therefore, it is necessary to prevent corrosion of steel materials,
High-purity water with dissolved oxygen and pH adjusted to remove impurities is used as water supply. In particular, in a supercritical pressure power generation plant using a once-through boiler, when impurities are contained in the feed water, the impurities are transferred to steam, are precipitated in the steam turbine, and are attached as scale. If the scale adheres to the moving blades or nozzles in the steam turbine, the performance will be degraded and the components will be corroded. Therefore, in a supercritical pressure power plant using a once-through boiler, a volatile treatment method of injecting volatile reagents such as hydrazine and ammonia is adopted as a method for adjusting dissolved oxygen and pH of feed water, and condensate desalination is also performed. A device is provided to remove corrosive components.

In a power plant, it is necessary to understand that the water quality adjustment of the feed water is sufficiently functioning, and it is constantly monitored whether the concentration of corrosive components in the feed water is below a target value. The corrosive components in the feedwater-steam in the power plant are sodium ions, chlorine ions and sulfate ions, and the target value of the ionic component in the feedwater-steam in the power plant equipped with the supercritical pressure once-through boiler is 3 ppb. At present, there is an ion chromatograph as an analyzer capable of measuring such a low concentration ion component with high sensitivity. Ion chromatograph has a lower limit of analysis of 0.1 pp
Since it is about b, the operation is easy, and continuous operation is possible, it is used for analysis of anions such as chlorine ions and sulfate ions in water supply of power plants.

As a conventional technique for monitoring water quality using an ion chromatograph, there is one disclosed in Japanese Patent Laid-Open No. 366796/1992. In this conventional technique, the condensate of a boiling water reactor is sampled and irradiated with ultraviolet rays to decompose organic matter in the condensate into anions, and the anions are analyzed using an anion column. .

[0005]

In the above-mentioned prior art, no consideration is given to the analysis of sodium ions which are cations in feed water. This is because in the conventional boiling water reactor, a volatile reagent such as ammonia was not injected, and it was not necessary to consider the influence of ammonia or the like in the analysis of low-concentration sodium ions.
On the other hand, in a supercritical pressure power plant equipped with a once-through boiler, it is necessary to analyze low-concentration sodium ions in a solution containing high-concentration ammonia. Therefore, even if the above-mentioned conventional technique is simply applied, it is not possible to detect low-concentration sodium ions with high accuracy. This is because the feedwater of the power plant equipped with the once-through boiler contains approximately 1 ppm of ammonia used for water quality adjustment, and is present at a high concentration relative to the sodium ion concentration of 3 ppb. When sample water containing a high concentration of ammonia is analyzed by ion chromatography, as shown in FIG. 4 (b),
Separation of sodium ions and ammonia ions is poor,
There is a problem that the analytical sensitivity of sodium ions is reduced.

An object of the present invention is to provide a water quality analysis method and an apparatus therefor capable of highly accurately detecting an extremely low concentration of cations contained in sample water.

[0007]

[Means for Solving the Problems] The above object is to analyze the water quality of sample water by supplying oxygen to the sample water and then subjecting the sample water to oxidation treatment by ultraviolet irradiation, and then measuring the cations in the sample water by cation ion chromatography. It is achieved by analyzing.

[0008]

[Operation] When ammonia is contained in the sample water,
By oxidizing this, ammonia is decomposed into anions, and the concentration of ammonia in the sample water is reduced. Since it is difficult to oxidize sample water containing a small amount of dissolved oxygen, the oxidation process is promoted by supplying oxygen into the sample water before the oxidation process. Since the ions produced by the oxidation treatment are anions, they do not affect the analysis by cation ion chromatography. As a result, the ammonia ion peak and the sodium ion peak are separated, and the sodium ion can be analyzed with high accuracy.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a water quality analyzer according to an embodiment of the present invention. This water quality analyzer is an oxygen supply device 1.
And an ultraviolet oxidation device 2, a concentrating device 3, and a cation ion chromatograph 4.

As shown in FIG. 2, the oxygen supply device 1 has a hydrophobic porous hollow fiber membrane 5 inside. The material of the hollow fiber membrane 5 is polytetrafluoroethylene, polypropylene, polyethylene or the like. The sample water supplied to the oxygen supply device 1 flows out from the oxygen supply device 1 through the inside of the hollow fiber membrane 5, and the high-purity oxygen gas supplied to the oxygen supply device 1 is stored in the hollow fiber membrane 5. The oxygen gas is discharged from the oxygen supply device 1 through the outside, and the sample water and the oxygen gas come into contact with each other in the oxygen supply device 1 so that the oxygen gas is dissolved in the sample water.

The ultraviolet oxidation device 2 includes an ultraviolet lamp 6 and
It is composed of a sample water channel 7. The ultraviolet lamp 6 is preferably a low-pressure mercury lamp having main wavelengths of 185 nm and 254 nm. The sample water flow path 7 has a structure in which a thin transparent pipe is spirally wound around the ultraviolet lamp 6. The sample water introduced into the ultraviolet oxidizer 2 is irradiated with ultraviolet rays from the lamp 6 while passing through the sample water flow path 7,
Then, it flows out from the ultraviolet oxidation device 2. Since such a thin pipe is used as the flow path 7 and the sample water is pushed out toward the cation ion chromatograph 4 side, the sample water at the time of the previous analysis does not remain at the time of this analysis, and the measurement accuracy is improved. .

The cation ion chromatograph 4 is shown in FIG.
As shown in, a separation column 8, a removal column 9, and a detector 10 are provided.

In the water quality analyzer having the above-described structure, sample water containing, for example, ammonia enters the oxygen supply device 1 and comes into contact with high-purity oxygen gas through the hollow fiber membrane 5 to dissolve oxygen in the sample water. . The sample water supplied with oxygen then enters the ultraviolet oxidation device 2 and is exposed to ultraviolet rays while flowing through the flow path 7 to be oxidized. By this oxidation treatment, ammonia in the sample water is decomposed and removed. Oxygen is supplied to the sample water with a small amount of dissolved oxygen in the step before this oxidation treatment step, so that decomposition and removal of ammonia in the oxidation treatment step are promoted. The sample water subjected to the oxidation treatment is then
After entering the concentrating device 3, the cations remaining in the sample water are concentrated to a predetermined amount, and then supplied to the cation ion chromatograph 4. In the cation ion chromatograph 4, the eluent is passed through the concentration column to analyze the cations of interest.

For example, sample water collected from feed water used in a supercritical pressure power plant is sodium ion 0.1.
It contains ppb and 1 ppm of ammonia ion. After oxygen is supplied to the sample water by the oxygen supply device 1, the low-pressure mercury lamp 6 irradiates the sample with ultraviolet rays to oxidize it, and the sample is analyzed by the cation chromatograph 4. The analysis result is shown in FIG. As shown in this figure, the concentration of ammonia ion in the sample water is significantly reduced by performing the UV oxidation treatment after supplying oxygen, and the peaks of sodium ion and ammonia ion are separated, and the analysis of low concentration sodium ion is performed. You can see that is possible. On the other hand, FIG.
As shown in (b), even if the sample water which is supplied with oxygen and is not subjected to the ultraviolet oxidation treatment is analyzed by a cation ion chromatograph, the peak of sodium ion is hidden by the peak of ammonia ion. It is not possible to analyze low concentrations of sodium ions with high precision.

As described above, in this embodiment, the sample water from the feed water of the power plant is supplied with oxygen, subjected to the ultraviolet oxidation treatment, and analyzed by the cation chromatograph. Therefore, the ammonia ions contained in the sample water are analyzed. It is possible to analyze low-concentration sodium ions with high accuracy by eliminating the interference caused by.

The present inventors have made various studies on water quality analysis methods in a feedwater-steam system of a power plant in order to improve the performance of the power plant and prevent corrosion of constituent equipment. Ion chromatograph is suitable as a method that can analyze corrosive components such as sodium ions, chloride ions, and sulfate ions contained in the feed water at low concentrations and is easy to operate and capable of continuous operation. However, as described above, with respect to sodium ions, it is impossible to analyze low-concentration sodium ions due to the interference of a large amount of ammonia ions contained in the feed water. The cation ion chromatograph is shown in Fig. 5.
As shown in, column 8 with cation exchange resin as stationary phase
Each cation is separated using an aqueous solution of various salts (for example, hydrochloric acid) as a mobile phase, passed through a remover 9, and detected by an electric conductivity detector 10. Since the affinity of ammonia ion for cation exchange resin is larger and closer to that of sodium ion, when analyzing sample water containing high concentration ammonia ion and low concentration sodium ion by cation ion chromatogram, the peak of sodium ion is This makes it difficult to quantitatively analyze low-concentration sodium ions because it is hidden by the peak of.

Therefore, in the present embodiment, attention was paid to the fact that sodium ions can be analyzed by an ion chromatograph by removing interfering ammonia ions, and a method for removing ammonia ions was examined. As a result, it was found that if the sample water is supplied with oxygen and then subjected to an ultraviolet oxidation treatment and analyzed by an ion chromatograph, interference of ammonia ions in the sample water is eliminated and low-concentration sodium ions can be analyzed. This is because the ammonia ions are oxidized and converted to anions such as nitrite ions and nitrate ions, and the ammonia ion concentration decreases. Since the nitrite ion and nitrate ion in the sample water generated by the UV oxidation treatment are anions, they do not affect the analysis of cations, and the residual ammonia ion also has a low concentration and does not interfere. Enables analysis of low concentration sodium ions. In the examination result, the ammonia ion concentration was changed to the sodium ion concentration of 2
If it is lowered to a high level, sodium ions and ammonia ions can be separated and analyzed during the analysis by ion chromatography. That is, 0.1 ppb
When analyzing a level of sodium ions, it can be analyzed by reducing the concentration of contained ammonia ions from 1000 ppb to about 10 ppb.

For the ultraviolet oxidation treatment, the presence of dissolved oxygen in the sample water is more effective. Usually, the dissolved oxygen concentration of the sample water of the feedwater-steam system in the power plant is low. Therefore, after supplying oxygen to the sample water from the feed water-steam system in the power plant, the water quality of the sample water is analyzed by the method of the present invention. As a method of supplying oxygen to the sample water, in this example, a gas-liquid contactor provided with a hydrophobic porous hollow fiber membrane was used, high-purity oxygen was used, and gas-liquid contact was performed through the membrane to the sample water. Although oxygen is supplied, it goes without saying that it is not limited to this.

FIG. 6 is a system diagram of a thermal power plant to which the water quality analyzer according to the above-mentioned embodiment is applied. In FIG. 6, 101 is a condenser, 102 is a condensate pump, and 103.
Is a condensate demineralizer, 104 is a low pressure feed water heater, 105 is a deaerator, 106 is a feed water pump, 107 is a high pressure feed water heater,
Reference numeral 108 is a boiler, and 109 to 111 are high pressure, medium pressure and low pressure turbines. The point s in the figure is the sampling point of the sample water in the water supply-steam system of the thermal power plant.

FIG. 7 is a block diagram of a sample water analyzer for analyzing sample water collected from each sampling point s shown in FIG. Reference numeral 120 denotes a sampling rack that collects the sampling tubes respectively taken out from the respective sampling points s and adjusts the pressure and temperature of the sample water. Reference numeral 121 denotes a switching device that selects and switches the sample water sampled from the sampling point s to be measured from the sampling rack 120. 122
Is a water quality analyzer for analyzing the sample water selected by the switch 122. The water quality analyzer according to this embodiment includes an anion analysis system 123 and a cation analysis system 124. The anion analysis system 123 is composed of a concentrator and an anion ion chromatograph, and the cation analysis system is
The water quality analyzer having the configuration of FIG. 1 is incorporated. By analyzing the type and concentration of cations and the type and concentration of anions at each sampling point s, it is possible to monitor what kind of substance in which part of the system shown in Fig. 6 is mixed in the sample water. Becomes

[0021]

According to the present invention, it is possible to analyze a low concentration of cations with high accuracy. In addition, by applying it to the analysis of the water supply of the power plant, it is possible to grasp the behavior of a slight amount of seawater leak and to easily deal with it. Further, since it becomes easy to control the water quality of the sodium ion concentration in the feed water, it is possible to reduce the impurity concentration in the steam transferred into the steam turbine. As a result, it is possible to reduce the problems of performance deterioration due to scale adhesion to the steam turbine and corrosion of component equipment,
The effect of improving the performance of the power generation plant and prolonging the life of the equipment can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a water quality analyzer according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of the oxygen supply device shown in FIG.

FIG. 3 is a configuration diagram of the ultraviolet oxidation device shown in FIG.

FIG. 4 is a diagram showing an analysis example (1) by the water quality analyzer shown in FIG. 1 and an analysis example (2) by a conventional example.

FIG. 5 is a configuration diagram of a cation ion chromatograph.

[Fig. 6] Water supply of a power plant to which a water quality analyzer is applied-
It is a block diagram which shows a steam system.

7 is a block diagram of a water quality analyzer for analyzing sample water collected from each sampling point s in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Oxygen supply apparatus, 2 ... UV oxidation apparatus, 3 ... Concentration apparatus, 4 ... Cation ion chromatograph, 5 ... Hollow fiber membrane, 6 ... UV lamp, 100 ... Power generation plant.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Kazuo Ikeuchi 3-1-1, Saiwaicho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi factory (72) Inventor Yusaku Nishimura 3--2, Saiwaicho, Hitachi-shi, Ibaraki No. 2 inside Hitachi Engineering Service Co., Ltd.

Claims (16)

[Claims] 1. A method for analyzing water quality of sample water, which comprises oxidizing the sample water and then analyzing cations in the sample water by a cation ion chromatograph. 2. A water quality analysis method for sample water, comprising irradiating the sample water with ultraviolet rays and then analyzing cations in the sample water by a cation ion chromatograph. 3. A water quality analysis method for sample water, wherein while irradiating the sample water with ultraviolet rays while flowing the sample water in a pipe wound around an ultraviolet lamp, the cations in the sample water are converted into cations. A water quality analysis method characterized by analysis by ion chromatography. 4. A method for analyzing water quality of sample water, which comprises supplying oxygen to the sample water and then oxidizing the sample water, and analyzing cations in the sample water by a cation ion chromatograph. 5. The water quality analysis method according to claim 4, wherein the oxidation treatment is performed by ultraviolet irradiation. 6. The water quality analysis method according to claim 5, wherein the irradiation of ultraviolet rays is performed while flowing the sample water into the pipe wound around the ultraviolet lamp. 7. The water quality analysis method according to claim 1, wherein the sample water is water quality adjusted by volatile treatment. 8. The water quality analysis method according to claim 1, wherein a sample of the feed water of a supercritical pressure power plant using a once-through boiler is used as sample water. 9. A water quality analyzer for sample water, comprising an oxidizing means for oxidizing the sample water and a cation ion chromatograph for analyzing cations in the oxidized sample water. 10. A water quality analyzer for sample water, comprising: an ultraviolet irradiation means for irradiating the sample water with ultraviolet rays; and a cation ion chromatograph for analyzing cations in the sample water irradiated with ultraviolet rays. Water quality analyzer. 11. A water quality analyzer for sample water, wherein the sample water is irradiated with ultraviolet rays by the ultraviolet lamp while flowing the sample water in a pipe wound around the ultraviolet lamp, A cation ion chromatograph for analyzing cations in sample water. 12. A water quality analyzer for sample water, wherein oxygen supplying means for supplying oxygen to the sample water, oxidizing means for oxidizing the sample water supplied with oxygen, and cations in the oxidized sample water are analyzed. A water quality analyzer comprising a cation ion chromatograph. 13. The water quality analyzer according to claim 12, wherein the oxidizing means is irradiation with ultraviolet rays. 14. The ultraviolet irradiation according to claim 13,
A water quality analyzer characterized in that it is carried out while flowing sample water into a pipe wound around an ultraviolet lamp. 15. A means for collecting sample water from each of a plurality of sampling points of a feed water-steam system of a power plant, and a switching means for selecting a sample water at a sampling point to be analyzed from each sample water sampled. And a water quality analyzer according to any one of claims 9 to 14 for analyzing cations in selected sample water, a water quality analyzer for a power plant. 16. The water quality analyzer for a power plant according to claim 15, wherein the power plant is a supercritical pressure power plant using a once-through boiler.