System and method for detecting anions in chemical cleaning agent of steam generator

Abstract

The invention relates to the field of ion chromatography detection, in particular to a system and a method for detecting anions in a chemical cleaning agent of a steam generator. The method comprises the following steps: carrying out oxygenolysis on an EDTA cleaning agent by using excessive hydrogen peroxide to obtain a primary product; performing ultraviolet photolysis on the first-stage product to remove hydrogen peroxide and hydrazine in the first-stage product to obtain a second-stage product; removing sodium salt in the second-stage product to obtain a third-stage product; degassing the third-stage product by using a high-purity argon purging and membrane separation method to obtain a treated substance of the EDTA cleaning agent; and carrying out ion chromatography detection by using anions contained in the treated object of the EDTA cleaning agent. According to the invention, accurate measurement of trace chloride ions, sulfate ions and other anions in the steam generator cleaning fluid can be completed.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of ion chromatography detection, in particular to a detection system and method for anions in a steam generator chemical cleaning agent. BACKGROUND

[0002] With the longer operation time of nuclear power plants, deposits will be generated on the inner wall of the steam generator and the U-shaped pipe, mainly including Fe3O4, Fe2O3 and FeO and other iron compounds. In addition, a small amount of sodium, copper, calcium and magnesium compounds may also be contained, and anions mainly exist in the form of chloride ions and sulfate ions.

[0003] EDTA chemical cleaning is one of the cleaning methods for the deposits of the steam generator of the power plant, and EDTA sodium salt or ammonium salt is usually selected as the cleaning agent to dissolve the surface deposits of the metal by complexation. After the steam generator is soaked with the cleaning agent, it is emptied and then rinsed with desalted water. The EDTA-2Na complex metal ions remove the dirt and deposits in the steam generator, such as scale, rust, corrosion products, etc., improve the thermal efficiency, prevent the corrosion and damage of the equipment caused by the dirt, and prolong the service life of the equipment. The hydrazine is a strong reducing agent, which can be used to prevent or reduce the generation of iron hydroxide, thereby preventing its conversion into iron hydroxide precipitate, helping to maintain the dissolved state of iron in water, preventing the scaling of the pipes and equipment in the system, and the two agents are complementary to each other.

[0004] Since the EDTA cleaning agent has a complex matrix, there is no effective analysis method to measure the anion content in the cleaning agent before and after the cleaning of the steam generator. The existence of too high chloride ions, sulfate ions and other anions in the cleaning agent can cause various forms of corrosion, such as pitting corrosion, electrochemical corrosion, acid corrosion, etc. The synergistic effect can damage the protective film on the metal surface, significantly accelerate the corrosion rate, and cause more serious corrosion. After the cleaning of the steam generator, the impurity content in the cleaning agent needs to be accurately measured to evaluate the deposition of hidden salt in the steam generator. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a detection system and method for anions in a steam generator chemical cleaning agent, which can accurately measure trace amounts of chloride ions, sulfate ions and other anions in the cleaning liquid of the steam generator.

[0006] The present application provides a detection method for anions in a steam generator chemical cleaning agent, comprising the following steps:

[0007] Step 1: The EDTA cleaning agent is oxidized and decomposed by an excess amount of hydrogen peroxide to obtain a primary product;

[0008] Step 2: The primary product is subjected to ultraviolet photolysis to remove hydrogen peroxide and hydrazine therein, thereby obtaining a secondary product;

[0009] Step three: removing the sodium salt in the secondary product to obtain a tertiary product;

[0010] Step four: degassing the tertiary product by purging with high-purity argon and membrane separation to obtain a processed product of the EDTA cleaning agent;

[0011] Step five: detecting the anions contained in the processed product of the EDTA cleaning agent by ion chromatography.

[0012] In one embodiment of the present application, the mass concentration of the hydrogen peroxide in step one is 20% to 25%.

[0013] In one embodiment of the present application, the volume ratio of the hydrogen peroxide to EDTA-2Na is 3:1 to 4:1.

[0014] In one embodiment of the present application, in step four, the carbon dioxide, nitrogen and oxygen dissolved in the tertiary product diffuse to the surface of the hydrophobic microporous membrane through the concentration gradient, diffuse to the gas phase on the other side through the micropores on the membrane, and the high-purity argon gas is used as a carrier gas to dilute and carry the carbon dioxide, nitrogen and oxygen away, thereby completing the removal of the carbon dioxide, nitrogen and oxygen.

[0015] In one embodiment of the present application, in step two, the primary product is irradiated with ultraviolet light of 254 nanometers to remove the hydrogen peroxide and hydrazine therein.

[0016] In one embodiment of the present application, in step three, the sodium salt in the secondary product is removed by using a hydrogen-type ion exchange column.

[0017] The present application provides a device for detecting anions in a steam generator chemical cleaning agent, comprising:

[0018] The liquid outlet of the decomposition tank is connected to a sample pump, an ultraviolet photolyzer, a hydrogen-type ion exchange, a degassing box and a six-way valve in sequence.

[0019] The liquid inlet of the decomposition tank is connected to a cleaning agent sample bottle and a hydrogen peroxide reagent bottle respectively.

[0020] The six-way valve is further connected to a waste liquid bottle, a KOH eluent generator and a guard column respectively.

[0021] The KOH eluent generator is further connected to an eluent pump and a high-purity water bottle in sequence.

[0022] The guard column is further connected to an analytical column, a suppressor, a conductivity cell and a data acquisition and control computer 18 in sequence.

[0023] In one embodiment of the present application, the liquid inlet of the decomposition tank is connected to a cleaning agent sample bottle and a hydrogen peroxide reagent bottle through a sample multi-position valve respectively.

[0024] In one embodiment of the present application, the quantitative volume of the six-way valve is 10 μL.

[0025] Compared with the prior art, the system and method for detecting anions in a steam generator chemical cleaning agent has the following beneficial effects:

[0026] (1) In the present application, by setting the sample injection multi-position valve, sample bottle, sample injection pump, eluent pump and eluent generator in cooperation, automatic injection of the cleaning agent sample and automatic injection of the processed cleaning agent sample into the ion chromatograph for detection can be realized, and the processes of sample injection, filtration, sample discharge and cleaning are fully automatic, which is convenient to operate. The device of the present application can effectively reduce the interference of the cleaning agent on the detection of anions, has high measurement accuracy and can complete accurate measurement of trace-level chloride ions, sulfate ions and other anions in the steam generator cleaning agent.

[0027] (2) In the present application, based on the oxidation-reduction method, by adding excessive hydrogen peroxide to decompose the EDTA cleaning agent, complete decomposition of the EDTA cleaning agent can be ensured, and the problem that EDTA cannot be completely separated due to retention on the chromatograph during direct measurement is solved.

[0028] (3) The method of ultraviolet photolysis is used to remove excessive hydrogen peroxide, which can effectively remove the excess hydrogen peroxide remaining during the decomposition of the EDTA cleaning agent, and at the same time, no other chemical reagent is introduced, which ensures the purity of the detection of anions in the chemical cleaning agent.

[0029] (4) The synergistic effect of hydrogen peroxide oxidation decomposition and ultraviolet photolysis removes the hydrazine in the steam generator cleaning agent, decomposes the hydrazine into nitrogen and water, and eliminates the interference of hydrazine on the detection of anions.

[0030] (5) The present application can meet the measurement of anion content in cleaning agents of other nuclear power plants, thermal power plants and chemical plants, and has good popularization. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The figure shows the structure of a system for detecting anions in a steam generator chemical cleaning agent.

[0032] In the figure: 1 - cleaning agent sample bottle; 2 - hydrogen peroxide reagent bottle; 3 - sample injection multi-position valve; 4 - decomposition tank; 5 - sample injection pump; 6 - ultraviolet photolysis device; 7 - hydrogen type ion exchange column; 8 - degassing box; 9 - six-way valve; 10 - waste liquid bottle; 11 - high-purity water bottle; 12 - eluent pump; 13 - KOH eluent generator; 14 - guard column; 15 - analysis column; 16 - suppressor; 17 - conductivity cell; 18 - data acquisition and control computer. DETAILED DESCRIPTION

[0033] For a further understanding of the present application, the embodiments thereof will be described in conjunction with examples, it being understood, however, that this description is made only by way of further illustration and not as a limitation on the present application.

[0034] The embodiments of the present application disclose a method for detecting anions in a steam generator chemical cleaning agent, comprising the following steps:

[0035] Step one: using excess hydrogen peroxide to oxidize and decompose the EDTA cleaning agent to obtain a primary product;

[0036] The concentration of EDTA-2Na in the EDTA cleaning agent is 100 g / L, and the concentration of hydrazine is 5.20 g / L;

[0037] The mass concentration of the hydrogen peroxide is 20% to 25%, preferably 20%;

[0038] The volume ratio of the hydrogen peroxide to EDTA-2Na is 3:1 to 4:1, preferably 3:1;

[0039] After the oxidation and decomposition, the EDTA-2Na is decomposed into carbon dioxide and water, and the hydrazine is partially decomposed to produce nitrogen and water.

[0040] Step two: performing ultraviolet photolysis on the primary product to remove hydrogen peroxide and hydrazine therein, to obtain a secondary product;

[0041] The reaction is performed in an ultraviolet photolysis device, and the hydrogen peroxide is decomposed into water and oxygen after irradiation by 254 nm ultraviolet light, so that the residual hydrogen peroxide in the primary product is removed; meanwhile, the hydrazine is decomposed;

[0042] In the first two steps, through the synergistic effect of excess hydrogen peroxide and photolysis, the hydrazine in the EDTA cleaning agent is completely removed, and the hydrazine is decomposed into nitrogen and water, so that the interference of the hydrazine on the detection of anions is eliminated;

[0043] Step three: removing sodium salt in the secondary product by using a hydrogen type ion exchange column to obtain a tertiary product;

[0044] The secondary product contains a large amount of sodium salt, and the sodium salt is removed by the ion exchange method, so that the excessive sodium salt can be prevented from causing the overload of the suppressor and the increase of the background conductance, thereby reducing the signal-to-noise ratio;

[0045] Step four: degassing the tertiary product by using high-purity argon blowing and membrane separation to obtain a processed product of the EDTA cleaning agent;

[0046] Carbon dioxide, nitrogen and oxygen dissolved in the tertiary product diffuse to the surface of the hydrophobic microporous membrane through the concentration gradient, diffuse to the gas phase on the other side of the microporous membrane through the micropores on the membrane, and high-purity argon gas is used as a carrier gas to dilute and carry carbon dioxide, nitrogen and oxygen away, so that the removal of carbon dioxide, nitrogen and oxygen is completed, and baseline fluctuation of the chromatogram is avoided.

[0047] Step five: the anions contained in the treatment product of the EDTA cleaning agent are detected by ion chromatography, and whether control measures are taken on the water quality indicators of the steam generator is judged according to the content values of various anions.

[0048] Specifically, according to the ion chromatography method, the standard concentration curves of various anions are drawn by using anion standard solutions of 3 μg / L, 6 μg / L, 10 μg / L, 20 μg / L and 50 μg / L, and then the content of anions such as chloride ions and sulfate ions in the treatment product of the EDTA cleaning agent obtained in step four is detected by using an ion chromatography detection device, so as to obtain the content values of the anions such as chloride ions and sulfate ions, and then whether control measures are taken on the water quality indicators of the steam generator is judged according to the content values of the anions.

[0049] Through the detection and monitoring of the content of anions in the steam generator cleaning agent, the corrosion of the steam generator system and the pipeline can be effectively avoided, the control and supervision of the water chemistry can be optimized, the equipment corrosion can be avoided, and the safe and reliable operation of the nuclear power plant unit can be ensured.

[0050] Embodiments of the present application disclose a detection system for anions in a steam generator chemical cleaning agent, as shown in the accompanying drawings, comprising: Figure 1

[0051] The liquid outlet end of the decomposition tank 4 is connected to a sample pump 5, an ultraviolet photolyzer 6, a hydrogen ion exchange column 7, a degassing box 8 and a six-way valve 9 in sequence.

[0052] The liquid inlet end of the decomposition tank 4 is connected to a cleaning agent sample bottle 1 and a hydrogen peroxide reagent bottle 2.

[0053] Specifically, the liquid inlet end of the decomposition tank 4 is connected to the cleaning agent sample bottle 1 and the hydrogen peroxide reagent bottle 2 through the sample multi-position valve 3, so as to realize automatic sampling.

[0054] The six-way valve 9 is also connected to a waste liquid bottle 9, a KOH eluent generator 13 and a guard column 14.

[0055] The KOH eluent generator 13 is also connected to an eluent pump 12 and a high-purity water bottle 11 in sequence.

[0056] The guard column 14 is also connected to an analysis column 15, a suppressor 16, a conductivity cell 17 and a data acquisition and control computer 18 in sequence.

[0057] ​The quantitative volume of the six-way valve is 10 μL.

[0058] The automatic injection of cleaning agent and 20% hydrogen peroxide is achieved through the cooperation of the injection multi-position valve 3, the cleaning agent sample bottle 1, and the hydrogen peroxide reagent bottle 2. In the decomposition cell 4, the 20% hydrogen peroxide decomposes the EDTA cleaning agent at 50°C. Under the continuous oxidation of the hydrogen peroxide, the EDTA cleaning agent is ultimately decomposed into carbon dioxide and water. The decomposed EDTA cleaning agent is automatically injected through the injection pump 5. The sample first passes through the 254nm UV photolyzer 6 to remove hydrazine and excess hydrogen peroxide from the sample without introducing other chemical reagents, preventing hydrogen peroxide from damaging the analytical column 15 and affecting the anion concentration measurement. The sample is then sent to the hydrogen-form ion exchange column 7 to remove high sodium salt content in the decomposed cleaning agent, preventing it from overloading the suppressor 16 and affecting the background conductivity. The sample is then sent to the degassing box 8 for degassing. The degassing box 8 uses high-purity argon gas purging and membrane separation to remove carbon dioxide and oxygen from the sample to prevent carbon dioxide and oxygen from causing fluctuations in the chromatographic baseline. Finally, the sample is quantified through the six-way valve 9, and the excess sample is discharged into the waste liquid bottle 10. After the quantification is completed, the six-way valve 9 is switched, and the eluent pump 12 extracts high-purity water from the high-purity water bottle 11 and sends it to the KOH eluent generator 13. The eluent generator modulates the eluent molar concentration by adjusting the current. The eluent pump 12 sends the sample and KOH eluent to the detection unit at a flow rate of 1.0 mL / min. The measurement of the anion concentration in the steam generator chemical cleaning agent is completed through the guard column 14, analytical column 15, suppressor 16, conductivity cell 17, and data acquisition and control computer 18.

[0059] The above embodiments are only intended to help understand the method and core concept of the present invention. It should be noted that, without departing from the principles of the present invention, a number of improvements and modifications may be made to the present invention by those skilled in the art, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0060] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for detecting anions in a steam generator chemical cleaning agent, characterized in that: The following steps are involved: Step 1: oxidatively decompose the EDTA detergent using excess hydrogen peroxide to obtain a primary product; Step 2: subjecting the primary product to ultraviolet photolysis to remove hydrogen peroxide and hydrazine therein to obtain a secondary product; Step 3: removing the sodium salt in the secondary product to obtain a tertiary product; Step 4: Degas the tertiary product by purging with high-purity argon and membrane separation to obtain a product treated with EDTA detergent; Step 5: Perform ion chromatography detection on the anions contained in the product treated with EDTA detergent.

2. The method for detecting anions in a steam generator chemical cleaning agent according to claim 1, characterized in that: In the step 1, the mass concentration of the hydrogen peroxide is 20% to 25%.

3. The method for detecting anions in a steam generator chemical cleaning agent according to claim 1, wherein: The volume ratio of the oxygenated water to the EDTA-2Na is 3:1 to 4:

1.

4. The method for detecting anions in a steam generator chemical cleaning agent according to claim 1, wherein: In step 4, the carbon dioxide, nitrogen, and oxygen dissolved in the tertiary product diffuse to the surface of the hydrophobic microporous membrane through a concentration gradient, and diffuse to the gas phase on the other side through the micropores on the membrane. High-purity argon acts as a carrier gas to dilute and carry the carbon dioxide, nitrogen, and oxygen away, thereby completing the removal of carbon dioxide, nitrogen, and oxygen.

5. The method for detecting anions in a steam generator chemical cleaning agent according to claim 1, characterized in that: In the step 2, the primary product is irradiated with 254 nm ultraviolet light to remove hydrogen peroxide and hydrazine therein.

6. The method for detecting anions in a steam generator chemical cleaning agent according to claim 1, characterized in that: In the step three, a hydrogen-type ion exchange column is used to remove the sodium salt in the secondary product.

7. A device for detecting anions in a steam generator chemical cleaning agent, characterized in that: include: The liquid outlet of the decomposition pool is connected to the sample injection pump, ultraviolet photolyzer, hydrogen ion exchange, degassing box and six-way valve in sequence; The liquid inlet end of the decomposition tank is connected to the cleaning agent sample bottle and the hydrogen peroxide reagent bottle respectively; The six-way valve is also connected to the waste liquid bottle, KOH eluent generator, and guard column respectively; The KOH eluent generator is also connected to the eluent pump and the high-purity water bottle in sequence; The guard column is also connected to the analytical column, suppressor, conductivity cell, and data acquisition and control computer 18 in sequence.

8. The device for detecting anions in a steam generator chemical cleaning agent according to claim 7, characterized in that: The liquid inlet end of the decomposition pool is connected to a cleaning agent sample bottle and a hydrogen peroxide reagent bottle respectively through a sampling multi-position valve.

9. The device for detecting anions in a steam generator chemical cleaning agent according to claim 7, characterized in that: The quantitative volume of the six-way valve is 10 μL.

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