A pH electrode dynamic measurement simulation experimental device

Abstract

This invention relates to a dynamic pH electrode measurement simulation experimental device, belonging to the category of water quality chemical analysis instruments for power plants. It includes a back pressure overflow cup, a pH meter, a pH electrode, a metal electrode cup for a standard pH electrode, a metal electrode cup for the pH electrode under test, a non-metallic electrode cup for the pH electrode under test, a needle valve, a three-way discharge valve, a device control unit, an ammonia-adding peristaltic pump, an electronic flow meter, a three-way valve, a variable-speed circulating pump, a cation exchange column, a diluted ammonia storage bottle, a test solution circulating water tank, a vacuum degassing module, a 5µm filter, a heat exchanger, a vacuum pump, a low-temperature water bath, and a level gauge. Its advantages include simulating the working conditions of pH measurement in power plants, rapidly detecting the performance of the pH electrode under test, providing a basis for judging the condition of power plant maintenance, reducing maintenance costs, and allowing the detected temperature compensation curve to be directly used to correct online meters. It is a fundamental guarantee for the safe and stable operation of power plant units and can bring direct economic benefits.

Description

Technical Field

[0001] This invention pertains to chemical analysis instruments for water quality in power plants, and particularly relates to a dynamic measurement simulation experimental device for pH electrodes. Background Technology

[0002] In the power industry, thermal power plants use water as a medium for energy conversion. To prevent scaling, phosphates, sodium hydroxide, ammonia, etc. are added to demineralized water to adjust the pH value and keep it within the standard operating range. If the pH value is exceeded, acidic or alkaline corrosion will occur. The accuracy of the pH value directly determines the quality of the water, and it is necessary to know the performance of the electrodes at different stages of use.

[0003] Water samples with a conductivity of less than 5 μS / cm are close to insulators. The friction between the flowing water and the electrode surface is similar to the friction between insulators, which can generate static charge. Due to the high resistance of pure water and the high input impedance of the instrument, the static charge cannot flow away in time and accumulates on the surface of the glass electrode. pH electrode cups are currently available in two types: acrylic glass and stainless steel. Different materials of electrode cups have different effects on the measured values ​​under different water samples, which requires testing and verification.

[0004] The instrument's temperature compensation only compensates for the coefficient F / (2.3026RT), and cannot compensate for changes in the reference electrode and the pH of the water sample itself with temperature. The pH control index for water vapor is the pH value at 25ºC; the pH value changes when deviating from 25ºC. Therefore, it is necessary to detect the temperature curves of water samples with different pH values ​​for compensation when the water sample temperature deviates from 25ºC. Thus, a water circulation experimental system needs to be established to test the performance of the pH electrode being measured. This device can simulate the temperature changes that affect the pH value when the ion concentration is constant, and detect the temperature curves of the electrode under different pH values ​​(which can serve as the temperature compensation curves of the electrode), as well as the influence of different electrode cup materials on the pH detection results. Summary of the Invention

[0005] This invention provides a dynamic measurement simulation experimental device for pH electrodes to meet the needs of detecting the performance of the pH electrode being tested.

[0006] The technical solution adopted in this invention includes a back pressure overflow cup, a pH meter, a pH electrode, a metal electrode cup for a standard pH electrode, a metal electrode cup for the pH electrode under test, a non-metal electrode cup for the pH electrode under test, a needle valve, a three-way discharge valve, a device control unit, an ammonia peristaltic pump, an electronic flow meter, a three-way valve, a variable speed circulating pump, a cation exchange column, a diluted ammonia storage bottle, a test solution circulating water tank, a vacuum degassing module, a 5µm filter, a heat exchanger, a vacuum pump, a low-temperature water bath, and a level gauge. The pH meter is connected to the pH electrode and placed in the center of the metal electrode cups for the standard pH electrode, the metal electrode cup for the pH electrode under test, and the non-metal electrode cup for the pH electrode under test, respectively. The vacuum degassing module is connected to the metal electrode cups for the standard pH electrode and the non-metal electrode cup for the pH electrode under test via the needle valve. The inlet of the electrode cup and the pH electrode under test is connected to the non-metallic electrode cup. The outlets of the standard pH electrode (metallic electrode cup), the pH electrode under test (metallic electrode cup), and the pH electrode under test (non-metallic electrode cup) are respectively connected to the back pressure overflow cup. The back pressure overflow cup is connected to the test liquid circulation tank via a pipeline through a discharge three-way valve. The level gauge is located in the test liquid circulation tank. The test liquid circulation tank is connected to the cation exchange column via a pipeline through a variable speed circulation pump. The diluted ammonia storage bottle is connected to the three-way valve via a pipeline through an ammonia addition peristaltic pump. The cation exchange column is connected to the three-way valve. The three-way valve is connected to the 5µm filter via an electronic flow meter and a heat exchanger. The filter is connected to the vacuum degassing module. The vacuum pump is connected to the vacuum degassing module. The low-temperature water bath is connected to the heat exchanger. The device control unit is connected to the component to be controlled.

[0007] The back pressure overflow cup provides a slight positive pressure to the detection liquid inside the electrode cup during the experiment, preventing air from entering the electrode cup.

[0008] The three-way discharge valve is used to discharge when the liquid level in the circulating water tank reaches the high limit.

[0009] The ammonia-adding peristaltic pump is used to adjust the pH of water samples at different values ​​during the experiment.

[0010] The electronic flow meter is used to detect the flow rate of the solution.

[0011] The variable speed circulating pump is used to provide circulating power to the circulating system.

[0012] The cation exchange column is used to remove ammonia ions from the detection solution.

[0013] The 5µm filter is used to remove particulate contaminants from the water sample.

[0014] The heat exchanger is used to regulate the temperature of the experimental water sample, with a temperature range of 15℃ to 45℃, and is used to detect changes in electrode performance at this temperature.

[0015] The low-temperature water bath provides a heat source and cold source for the heat exchanger.

[0016] How to use

[0017] 1) Start the variable speed circulating pump 13 to establish water sample circulation, turn on the constant temperature system and degassing system, and adjust the water sample to a constant temperature of 25℃ to confirm that all components of the system are working normally;

[0018] 2) Adjust the pH of the test solution to 8 using the ammonia addition system, and then slowly change the water sample temperature from 15℃ to 45℃ while maintaining a stable pH.

[0019] 3) Record the pH measurement value after the temperature change, and obtain the temperature compensation curve of the tested pH electrode at a liquid pH of 8.

[0020] 4) Repeat steps 2 and 3 to measure the temperature compensation curve of the pH electrode under test in the test solution at pH 9 and pH 10;

[0021] 5) Experiments were conducted using different metal and non-metal electrode cups to obtain the influence compensation curves of different electrode cups. Steps 2, 3, and 4 were repeated after changing the electrode cup.

[0022] The advantages of this invention are:

[0023] 1) This device can simulate the working conditions of pH measurement in a power plant.

[0024] 2) It can quickly detect the performance of the pH electrode under test, especially when the electrode is nearing the end of its service life. It can be used as a basis for judging the condition of power plants and reduce maintenance costs.

[0025] 3) Tracking and testing of working electrodes at power plants can provide a basis for optimizing the selection of electrode models, and high-performance, long-life electrodes can reduce operation and maintenance costs.

[0026] 4) The detected temperature compensation curve can be directly used to correct the online meter. Accurate pH measurement and control is the basic guarantee for the safe and stable operation of power plant units, which can bring direct economic benefits. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the present invention;

[0028] Figure 2 This is a schematic diagram of the principle of the present invention. Detailed Implementation

[0029] The main factors affecting pH measurement results are temperature, bubbles, and the content of anions and cations. These factors are all addressed in this device, and non-metallic and metallic electrode cups are used to simulate the effects of electrostatic charge.

[0030] Currently, the main generating units in power plants basically use the method of adding ammonia water to adjust the pH value. This device is also designed to adjust and change the pH value by adding diluted ammonia water.

[0031] like Figure 1 , 2 As shown, the device includes a back pressure overflow cup 1, a pH meter 2, a pH electrode 3, a metal electrode cup for a standard pH electrode 4, a metal electrode cup for the pH electrode under test 5, a non-metal electrode cup for the pH electrode under test 6, a needle valve 7, a three-way discharge valve 8, a device control unit 9, an ammonia peristaltic pump 10, an electronic flow meter 11, a three-way valve 12, a variable speed circulation pump 13, a cation exchange column 14, a dilute ammonia storage bottle 15, a test solution circulating water tank 16, a vacuum degassing module 17, a 5µm filter 18, a heat exchanger 19, a vacuum pump 20, a low-temperature water bath 21, and a level gauge 22. The pH meter 2 is connected to the pH electrode 3 and is placed in the center of the metal electrode cups 4, 5, and 6 respectively. The vacuum degassing module 17 is connected to the metal electrode cups 4, 5, and 6 respectively via the needle valve 7. The H electrode is connected to the inlet of the non-metallic electrode cup 6. The outlets of the standard pH electrode (metallic electrode cup 4), the tested pH electrode (metallic electrode cup 5), and the tested pH electrode (non-metallic electrode cup 6) are respectively connected to the back pressure overflow cup 1. The back pressure overflow cup 1 is connected to the test liquid circulation tank 16 via a pipeline through the discharge three-way valve 8. The level gauge 22 is located in the test liquid circulation tank 16. The test liquid circulation tank 16 is connected to the cation exchange column 14 via a pipeline through the variable speed circulation pump 13. The diluted ammonia storage bottle 15 is connected to the three-way valve 12 via a pipeline through the ammonia addition peristaltic pump 10. The cation exchange column 14 is connected to the three-way valve 12. The three-way valve 12 is connected to the 5µm filter 18 via the electronic flow meter 11, the heat exchanger 19, and the vacuum degassing module 17. The vacuum pump 20 is connected to the vacuum degassing module 17. The low temperature water bath 21 is connected to the heat exchanger 19. The device control unit 9 is connected to the components to be controlled.

[0032] The back pressure overflow cup 1 provides a slight positive pressure to the detection liquid in the electrode cup during the experiment, preventing air from entering the electrode cup.

[0033] The three-way discharge valve 8 is a discharge valve used when the liquid level in the detection liquid circulation tank reaches the high limit.

[0034] The ammonia-adding peristaltic pump 10 is used to adjust the pH value of water samples during the experiment.

[0035] The electronic flow meter 11 is used to detect the flow rate of the solution.

[0036] The variable speed circulating pump 13 is used to provide circulating power to the circulating system.

[0037] The cation exchange column 14 is used to remove ammonia ions from the detection solution.

[0038] The 5µm filter 18 is used to remove particulate contaminants from the water sample.

[0039] The heat exchanger 19 is used to adjust the temperature of the experimental water sample, with a temperature range of 15℃ to 45℃, and is used to detect changes in electrode performance at this temperature.

[0040] The low-temperature water bath 21 provides a heat source and cold source for the heat exchanger.

[0041] Working principle:

[0042] The test solution is recycled. By changing the pH value and temperature of the recycled test solution, the changes in water quality in the power plant are simulated. The performance of the pH electrode is dynamically detected by using an online comparison measurement method of pH.

[0043] When using the test solution circulating water tank 16 for the first time, ultrapure water is added to the lower limit of the working liquid level. When the test experiment is carried out, the flow rate is first adjusted to the required level by the variable speed circulating pump 13 and pumped to the cation exchange column 14 to remove the ammonia ions added during the pH adjustment process. After passing through the exchange column, the pH value of the test solution is at a neutral value, which prepares for the next step of increasing the pH value.

[0044] During the experiment, the pH value of the test solution changes by adding diluted ammonia water from the ammonia storage bottle 15 to the test solution via the ammonia peristaltic pump 10 through the three-way valve 12. The amount added is controlled to the required value by the instrument equipped with the standard pH electrode 4.

[0045] The total flow rate is measured by the electronic flow meter 11 and supplied to the device control unit 9.

[0046] After ammonia is added, the test solution passes through heat exchanger 19, and the temperature is adjusted to the required temperature change (15℃~45℃) during the experiment. The heat source required for heat exchange is provided by low-temperature water tank 21.

[0047] Particulate matter is removed by a 5µm filter to prevent contaminants from affecting the measuring electrode.

[0048] The vacuum degassing module 17 removes the gas from the measuring liquid and eliminates the influence of gases such as carbon dioxide in the air on the electrodes. The vacuum power source required for the vacuum degassing module to work is provided by the vacuum pump 20.

[0049] The test solution processed by the above steps is sent to the metal electrode cup 4 for pH electrode, the metal electrode cup 5 for pH electrode under test, and the non-metal electrode cup 6 for pH electrode under test via needle valve 7 according to experimental needs for pH electrode 3 measurement. The test solution in the electrode cup is provided with a slight positive pressure by the back pressure overflow cup 1, which is slightly higher than the measuring electrode cup, in order to prevent air from entering the electrode cup.

[0050] The liquid level in the circulating water tank 16 is measured by the level gauge 22, and when the upper limit of the working liquid level is reached, it is discharged by the drain three-way valve 8.

[0051] How to use

[0052] 1) Start the variable speed circulating pump 13 to establish water sample circulation, turn on the constant temperature system and degassing system, and adjust the water sample to a constant temperature of 25℃ to confirm that all components of the system are working normally;

[0053] 2) Adjust the pH of the test solution to 8 using the ammonia addition system, and then slowly change the water sample temperature from 15℃ to 45℃ while maintaining a stable pH.

[0054] 3) Record the pH measurement value after the temperature change, and obtain the temperature compensation curve of the tested pH electrode at a liquid pH of 8.

[0055] 4) Repeat steps 2 and 3 to measure the temperature compensation curve of the pH electrode under test in the test solution at pH 9 and pH 10;

[0056] 5) Experiments were conducted using different metal and non-metal electrode cups to obtain the influence compensation curves of different electrode cups. Steps 2, 3, and 4 were repeated after changing the electrode cup.

Claims

1. A dynamic pH electrode measurement simulation experimental device, characterized in that: The system includes a back pressure overflow cup, pH meter, pH electrode, metal electrode cup for the standard pH electrode, metal electrode cup for the pH electrode under test, non-metal electrode cup for the pH electrode under test, needle valve, drain three-way valve, device control unit, ammonia addition peristaltic pump, electronic flow meter, three-way valve, variable speed circulation pump, cation exchange column, diluted ammonia storage bottle, test solution circulating water tank, vacuum degassing module, 5µm filter, heat exchanger, vacuum pump, low temperature water bath, and level gauge. The pH meter is connected to the pH electrode and placed in the center of the metal electrode cups for the standard pH electrode, the metal electrode cup for the pH electrode under test, and the non-metal electrode cup for the pH electrode under test, respectively. The vacuum degassing module is connected to the metal electrode cups for the standard pH electrode, the metal electrode cup for the pH electrode under test, and the non-metal electrode cup for the pH electrode under test via the needle valve. The pH electrode is connected to the inlet of a non-metallic electrode cup. The outlets of the standard pH electrode (metallic electrode cup), the pH electrode under test (metallic electrode cup), and the pH electrode under test (non-metallic electrode cup) are respectively connected to a back pressure overflow cup. The back pressure overflow cup is connected to the test liquid circulation tank via a pipeline through a discharge three-way valve. The level gauge is located in the test liquid circulation tank. The test liquid circulation tank is connected to the cation exchange column via a pipeline through a variable speed circulation pump. The diluted ammonia storage bottle is connected to the three-way valve via a pipeline through an ammonia-adding peristaltic pump. The cation exchange column is connected to the three-way valve. The three-way valve is connected to a 5µm filter via an electronic flow meter, a heat exchanger, and a vacuum degassing module. The vacuum pump is connected to the vacuum degassing module. The low-temperature water bath is connected to the heat exchanger. The device control unit is connected to the components to be controlled.

2. The pH electrode dynamic measurement simulation experimental device according to claim 1, characterized in that: The back pressure overflow cup provides a slight positive pressure to the detection liquid inside the electrode cup during the experiment, preventing air from entering the electrode cup.

3. The pH electrode dynamic measurement simulation experimental device according to claim 1, characterized in that: The three-way discharge valve is used to discharge when the liquid level in the circulating water tank reaches the high limit.

4. The pH electrode dynamic measurement simulation experimental device according to claim 1, characterized in that: The ammonia-adding peristaltic pump is used to adjust the pH of water samples at different values ​​during the experiment.

5. The pH electrode dynamic measurement simulation experimental device according to claim 1, characterized in that: The electronic flow meter is used to detect the flow rate of the solution.

6. The pH electrode dynamic measurement simulation experimental device according to claim 1, characterized in that: The variable speed circulating pump is used to provide circulating power to the circulating system.

7. The pH electrode dynamic measurement simulation experimental device according to claim 1, characterized in that: The cation exchange column is used to remove ammonia ions from the detection solution.

8. The pH electrode dynamic measurement simulation experimental device according to claim 1, characterized in that: The 5µm filter is used to remove particulate contaminants from the water sample.

9. The pH electrode dynamic measurement simulation experimental device according to claim 1, characterized in that: The heat exchanger is used to regulate the temperature of the experimental water sample, with a temperature range of 15℃ to 45℃, and is used to detect changes in electrode performance at this temperature.

10. The pH electrode dynamic measurement simulation experimental device according to claim 1, characterized in that: The low-temperature water bath provides a heat source and cold source for the heat exchanger.

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