Temperature compensation method for measuring conductivity of ultrapure water and measurement control system

Abstract

The invention discloses a temperature compensation method for ultrapure water conductivity measurement and a measurement control system, belongs to the technical field of water quality monitoring and control, and solves the problem of inaccurate measurement of the ultrapure water conductivity under a high-temperature condition. A theoretical model and actual test data are creatively fused, and a compensation coefficient which more accurately reflects the change of the ultrapure water conductivity along with the temperature is obtained through fitting; compared with a traditional temperature compensation method, the method provided by the invention considers the special property of ultrapure water, that is, the influence of the self-ionization phenomenon of water at high temperature on the conductivity is obviously enhanced, so that the conductivity measurement deviation caused by temperature rise can be more accurately corrected; even under the condition of slight fluctuation of water quality components, the compensation accuracy can be ensured, and the reliability of a measurement result is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of water quality monitoring and control, and relates to a precise measurement and management of ultrapure water conductivity, especially a key technical breakthrough in the application of proton exchange membrane (PEM) electrolyzer, specifically a temperature compensation method for ultrapure water conductivity measurement and a measurement control system. Background Art

[0002] Water quality monitoring technology is one of the key means to ensure that water quality in the fields of industrial production, environmental protection, drinking water safety, etc. meets standards. It includes the determination and analysis of various physical, chemical, biological and other indicators in water bodies. Conductivity is one of the basic and important indicators, which directly reflects the total amount of dissolved ions in water. With the development of science and technology, water quality monitoring technology continues to improve, and automation, intelligence, and high precision have become development trends to meet the growing needs of water quality management and environmental protection.

[0003] Ultrapure water refers to water that contains almost no impurities and is widely used in high-tech fields such as semiconductor manufacturing, biopharmaceuticals, and electric energy (such as PEM electrolyzers). In these applications, even trace amounts of impurities may seriously affect product quality or equipment performance, so there are extremely strict requirements for the preparation, storage, transportation and online monitoring of ultrapure water. Conductivity is the main indicator for measuring the purity of ultrapure water, and its accurate measurement is crucial to ensure the stability of the process and the product qualification rate.

[0004] The proton exchange membrane (PEM) electrolyzer is a highly efficient energy conversion device that produces hydrogen and oxygen by electrolyzing water. It is an important component of hydrogen production, energy storage and fuel cell technology. The working conditions of the PEM electrolyzer are harsh, requiring the use of ultrapure water as the electrolyte to avoid impurities that damage the electrolysis efficiency and electrode materials. Conductivity is an important parameter that reflects the state of the electrolyte. Its accurate monitoring directly affects the electrolysis efficiency, energy consumption control and system maintenance.

[0005] In applications such as PEM electrolyzers, the conductivity measurement of ultrapure water faces great challenges due to the high working environment temperature and the requirement to maintain measurement accuracy and stability over a wide temperature range (e.g., 25°C to 95°C). High temperature not only exacerbates the autoionization of water, resulting in a significant increase in conductivity, but also makes it difficult for traditional temperature compensation control methods to accurately predict changes in conductivity. In addition, the low ion concentration of ultrapure water makes small changes in conductivity more sensitive, placing higher demands on measurement accuracy.

[0006] In the measurement of ultrapure water conductivity, due to the strong correlation between conductivity and temperature, the traditional temperature compensation method under high temperature conditions often cannot meet the high-precision requirements. Therefore, it is urgent to improve the traditional temperature compensation control method of ultrapure water in the high temperature range. Summary of the invention

[0007] The technical solution of the present invention is used to solve the problem of inaccurate measurement of ultrapure water conductivity under high temperature conditions.

[0008] The present invention solves the above technical problems through the following technical solutions:

[0009] A temperature compensation method for measuring the conductivity of ultrapure water comprises the following steps:

[0010] S1. Calculate the theoretical conductivity of ultrapure water. The specific method is as follows:

[0011] The calculation formula of ultrapure water theoretical conductivity σ is as follows:

[0012] σ=zC(u H+ +u OH- ) (1)

[0013] Where z is the charge of the ion; C is the concentration of the ion; u H+ 、u OH- are the mobility of hydrogen ions and hydroxide ions, respectively;

[0014] At 25℃, H + and OH - The migration rates are 360m 2 / (V·s) and 198m 2 / (V·s), and substituting it into formula (1) we get:

[0015] σ=1×10 -7 mol / L×1m 2 / (V·s)×(360+198)m 2 / (V·s) (2)

[0016] The theoretical conductivity σ of ultrapure water at 25°C is calculated to be approximately 0.055 μS / cm;

[0017] S2. Fitting the effect of temperature on conductivity. The specific method is as follows:

[0018] The temperature coefficient α is used to characterize the effect of temperature on conductivity. The formula is defined as follows:

[0019]

[0020] In the formula, is the uncompensated conductivity of pure water at temperature T, is the conductivity of pure water at 25℃; T is the operating set temperature value;

[0021] The fitting formula of pure water conductivity temperature compensation coefficient is as follows:

[0022] α=0.0318*e 0.00196T (4)

[0023] Substituting formula (4) into formula (3), we get:

[0024]

[0025] S3. Calculation of temperature compensation for the electrolytic cell. The specific method is as follows:

[0026] The uncompensated conductivity of the test water sample is set to be the sum of the conductivity of the self-ionized hydrogen ions and hydroxide ions of the water and the conductivity of the dissolved ions, that is:

[0027]

[0028] Select 2% / ℃ as the impurity ion temperature compensation coefficient, that is:

[0029]

[0030] Among them, x 表观 To test the uncompensated conductivity of the water sample, x 溶质 is the conductivity of dissolved ions.

[0031] A PEM electrolysis water ultrapure water conductivity measurement and control system comprises: a main valve (1), a branch valve (2), an ion purification device (3), a temperature sensor (4), a conductivity sensor (5), and a control unit (6); the input ends of the main valve (1) and the branch valve (2) are both sealedly connected to an electrolyte inlet pipeline, the output end of the main valve (1) is sealedly connected to the input end of the ion purification device (3), the output end of the branch valve (2) is sealedly connected to the output end of the ion purification device (3), the temperature sensor (4) and the conductivity sensor (5) are installed on the pipeline between the ion purification device (3) and the electrolyte inlet, the temperature sensor (4) and the conductivity sensor (5) input the measured data to the control unit (6), the control unit (6) is integrated with the above-mentioned ultrapure water conductivity measurement temperature compensation method, and the control unit (6) outputs a control instruction for controlling the opening of the main valve (1) and the branch valve (2) according to the above-mentioned ultrapure water conductivity measurement temperature compensation method.

[0032] Furthermore, the control instructions are specifically as follows: when the system conductivity increases, the opening of the main valve (1) increases, the opening of the branch valve (2) decreases, the purification amount of the ion purification device (3) is increased, and the system is maintained to operate at a low conductivity; when the system conductivity decreases, the opening of the branch valve (2) increases, the opening of the main valve (1) decreases, and the purification amount of the ion purification device (3) is reduced.

[0033] Preferably, the ion purification device (3) uses a high-temperature mixed bed resin.

[0034] Preferably, the temperature sensor (4) is a high-precision PT1000 temperature sensor.

[0035] An electronic device includes a memory and a processor, wherein the memory is used to store a program that supports the processor to execute the temperature compensation method for measuring the conductivity of ultrapure water, and the processor is configured to execute the program stored in the memory.

[0036] A storage medium stores a computer program, which, when executed by a processor, executes the steps of the temperature compensation method for measuring the conductivity of ultrapure water.

[0037] The advantages of the present invention are:

[0038] The method of this embodiment innovatively integrates the theoretical model and the actual test data, and obtains a compensation coefficient that more accurately reflects the change of ultrapure water conductivity with temperature through fitting; compared with the traditional temperature compensation method, the method of the present invention takes into account the special properties of ultrapure water, that is, the significant enhancement of the effect of water autoionization on conductivity at high temperature, so that the conductivity measurement deviation caused by temperature rise can be corrected more accurately; even in the case of slight fluctuations in water quality components, the accuracy of compensation can be guaranteed, which greatly improves the reliability of the measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a flow chart of a temperature compensation method for ultrapure water conductivity measurement according to a first embodiment of the present invention;

[0040] Figure 2 It is a comparison curve of conductivity test of different schemes;

[0041] Figure 3 It is a structural diagram of a PEM electrolyzed water ultrapure water conductivity measurement and control system according to the second embodiment of the present invention. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments:

[0044] Embodiment 1

[0045] like Figure 1 As shown, the temperature compensation method for measuring the conductivity of ultrapure water according to an embodiment of the present invention comprises the following steps:

[0046] 1. Calculate the theoretical conductivity of ultrapure water

[0047] Conductivity measurement is mainly used to detect the purity of water. It is an effective, simple and reliable method to detect ionic impurities in water. Conductivity measuring instruments are divided into several types, such as on-site measurement, laboratory measurement, and online measurement. However, not every instrument is suitable for ultrapure water / high-purity water conductivity measurement.

[0048] Theoretically, the conductivity of pure water can be estimated by calculating the concentration of ions in it. At 25°C, the concentration of hydrogen ions (H+) and hydroxide ions (OH-) in pure water is equal, about 1×10 -7 mol / L.

[0049] The calculation formula of ultrapure water theoretical conductivity σ is as follows:

[0050] σ=zC(u H+ +u OH- ) (1)

[0051] Where z is the charge of the ion, for H + and OH - For example, the charge number of an ion is 1; C is the concentration of the ion; u H+ 、u OH- They are the mobility of hydrogen ions and hydroxide ions, respectively, and are related to the speed at which ions move.

[0052] At 25℃, H + and OH - The mobility is about 360m 2 / (V·s) and 198m 2 / (V·s), and substituting it into formula (1) we can get:

[0053] σ=1×10 -7 mol / L×1m 2 / (V·s)×(360+198)m 2 / (V·s) (2)

[0054] The theoretical conductivity σ of ultrapure water at 25°C is calculated to be approximately 0.055μS / cm.

[0055] 2. Effect of fitting temperature on conductivity

[0056] Conductivity is greatly affected by the temperature of the water sample. The higher the water sample temperature, the higher the ion activity and the higher the conductivity. According to the temperature compensation coefficient in GB T11007-2008 "Conductivity Meter Test Method", the temperature coefficient α is usually used to characterize the influence of temperature on conductivity. The formula is defined as follows:

[0057]

[0058] In the formula, is the uncompensated conductivity of pure water at temperature T, is the conductivity of pure water at 25℃, which is 0.055μS / cm; T is the operating temperature value, in degrees Celsius (℃).

[0059] According to ASTM D1125-23 "Standard Test Method for Electrical Conductivity and Resistivity of Water" and test data, the temperature compensation coefficient of pure water conductivity is fitted. The fitting formula of the temperature compensation coefficient of pure water conductivity is as follows:

[0060] α=0.0318*e 0.00196T (4)

[0061] Substituting formula (4) into formula (3), we get:

[0062]

[0063] 3. Temperature compensation calculation for electrolytic cell

[0064] The electrolytic cell is used with a low concentration of impurity ions, which can be understood as an infinitely diluted aqueous solution. The conductivity is mainly caused by the conductivity of hydrogen ions and hydroxide ions from water ionization and the conductivity of dissolved ions. The temperature coefficient of water varies greatly, mainly because the self-ionization of water molecules depends more on temperature than the conductivity caused by other ions. Given that there are almost no contaminant ions in pure water samples, the temperature coefficient α value is mainly affected by the self-ionization of water. In other samples, the concentration of contaminant ions is many times higher than the concentration of ions produced by the self-ionization of water. Therefore, the high temperature dependence is suppressed and the temperature coefficient α value becomes more linear. It is challenging to perform accurate temperature compensation in pure water, so we set the uncompensated conductivity of the test water sample to be the sum of the conductivity of hydrogen ions and hydroxide ions from water self-ionization and the conductivity of dissolved ions, that is:

[0065]

[0066] Since the temperature compensation coefficients of different ion conductivities are different, there are more metal ions in natural water or general pure water. The conductivity temperature coefficient of impurities in water is relatively stable. Generally, 2% / ℃ is selected as the impurity ion temperature compensation coefficient, that is:

[0067]

[0068] Among them, x 表观 To test the uncompensated conductivity of the water sample, x 溶质 is the conductivity of dissolved ions.

[0069] like Figure 2 As shown, it is a conductivity test comparison curve of different schemes. Figure 2 The curve marked by the middle triangle is the conductivity value after theoretical calculation and compensation. Figure 2 The circle-marked curve is the conductivity measurement value of the traditional fixed 2% temperature compensation solution. Figure 2 The curve marked with a square in the middle is the actual conductivity value after conductivity compensation of the solution of the present invention. It can be seen from the figure that the actual conductivity value of the solution of the present invention is basically consistent with the conductivity value after theoretical calculation compensation.

[0070] Embodiment 2

[0071] like Figure 3 As shown, a PEM electrolyzed water ultrapure water conductivity measurement and control system of this embodiment comprises: a main valve (1), a branch valve (2), an ion purification device (3), a temperature sensor (4), a conductivity sensor (5), and a control unit (6); the input ends of the main valve (1) and the branch valve (2) are both sealedly connected to the electrolyte inlet pipeline, the output end of the main valve (1) is sealedly connected to the input end of the ion purification device (3), the output end of the branch valve (2) is sealedly connected to the output end of the ion purification device (3), the temperature sensor (4) and the conductivity sensor (5) are installed on the pipeline between the ion purification device (3) and the electrolyte inlet, the temperature sensor (4) and the conductivity sensor (5) input the measured data to the control unit (6), and the control unit (6) is used to control the system. The unit (6) is integrated with the temperature compensation method for measuring the conductivity of ultrapure water described in the first embodiment. The control unit (6) outputs a control instruction according to the temperature compensation method for measuring the conductivity of ultrapure water, which is used to control the opening of the main valve (1) and the branch valve (2); when the conductivity of the system increases, the opening of the main valve (1) increases, and the opening of the branch valve (2) decreases, thereby increasing the purification amount of the ion purification device (3) and maintaining the system to process low conductivity operation; when the conductivity of the system decreases, the opening of the branch valve (2) increases, and the opening of the main valve (1) decreases, thereby reducing the purification amount of the ion purification device (3); the ion purification device (3) uses a high-temperature mixed bed resin to adsorb impurity ions in the circulating electrolyte; the temperature sensor (4) uses a high-precision PT1000 temperature sensor.

[0072] Embodiment 3

[0073] An electronic device includes a memory and a processor, wherein the memory is used to store a program that supports the processor to execute the temperature compensation method for ultrapure water conductivity measurement described in Example 1, and the processor is configured to execute the program stored in the memory.

[0074] Embodiment 4

[0075] A storage medium stores a computer program, which, when executed by a processor, executes the steps of the temperature compensation method for measuring the conductivity of ultrapure water described in Embodiment 1.

[0076] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A temperature compensation method for ultrapure water conductivity measurement, characterized in that: The following steps are involved: S1. Calculate the theoretical conductivity of ultrapure water. The specific method is as follows: The calculation formula of ultrapure water theoretical conductivity σ is as follows: σ=zC(u H+ +in OH- ) (1) Where z is the charge of the ion; C is the concentration of the ion; u H+ 、u OH- are the mobility of hydrogen ions and hydroxide ions, respectively; At 25℃, H + and OH - The migration rates are 360m 2 / (V·s) and 198m 2 / (V·s), and substituting it into formula (1) we get: σ=1×10 -7 mol / L×1m 2 / (V·s)×(360+198)m 2 / (V·s) (2) The theoretical conductivity σ of ultrapure water at 25°C is calculated to be approximately 0.055 μS / cm; S2. Fitting the effect of temperature on conductivity. The specific method is as follows: The temperature coefficient α is used to characterize the effect of temperature on conductivity. The formula is defined as follows: In the formula, is the uncompensated conductivity of pure water at temperature T, is the conductivity of pure water at 25℃; T is the operating set temperature value; The fitting formula of pure water conductivity temperature compensation coefficient is as follows: α＝0.0318*e 0.00196T (4) Substituting formula (4) into formula (3), we get: S3. Calculation of temperature compensation for the electrolytic cell. The specific method is as follows: The uncompensated conductivity of the test water sample is set to be the sum of the conductivity of the self-ionized hydrogen ions and hydroxide ions of the water and the conductivity of the dissolved ions, that is: Select 2% / ℃ as the impurity ion temperature compensation coefficient, that is: Among them, x 表观 To test the uncompensated conductivity of the water sample, x 溶质 is the conductivity of dissolved ions.

2. A PEM electrolyzed water ultrapure water conductivity measurement and control system, comprising: A main valve (1), a branch valve (2), an ion purification device (3), a temperature sensor (4), a conductivity sensor (5), and a control unit (6); the input ends of the main valve (1) and the branch valve (2) are both sealedly connected to the electrolyte inlet pipeline, the output end of the main valve (1) is sealedly connected to the input end of the ion purification device (3), the output end of the branch valve (2) is sealedly connected to the output end of the ion purification device (3), the temperature sensor (4) and the conductivity sensor (5) are installed on the pipeline between the ion purification device (3) and the electrolyte inlet, and the temperature sensor (4) and the conductivity sensor (5) input the measured data to the control unit (6), characterized in that the temperature compensation method for measuring the conductivity of ultrapure water as claimed in claim 1 is integrated in the control unit (6), and the control unit (6) outputs a control instruction for controlling the opening of the main valve (1) and the branch valve (2) according to the temperature compensation method for measuring the conductivity of ultrapure water.

3. The PEM electrolyzed water ultrapure water conductivity measurement and control system according to claim 2, characterized in that: The control instructions are specifically as follows: when the system conductivity increases, the opening of the main valve (1) increases, the opening of the branch valve (2) decreases, the purification amount of the ion purification device (3) is increased, and the system is maintained to operate at a low conductivity; when the system conductivity decreases, the opening of the branch valve (2) increases, the opening of the main valve (1) decreases, and the purification amount of the ion purification device (3) is reduced.

4. The PEM electrolyzed water ultrapure water conductivity measurement and control system according to claim 2, characterized in that: The ion purification device (3) uses high-temperature mixed bed resin.

5. The PEM electrolyzed water ultrapure water conductivity measurement and control system according to claim 2, characterized in that: The temperature sensor (4) is a high-precision PT1000 temperature sensor.

6. An electronic device, comprising a memory and a processor, characterized in that: The memory is used to store a program for supporting the processor to execute the temperature compensation method for measuring the conductivity of ultrapure water as claimed in claim 1, and the processor is configured to execute the program stored in the memory.

7. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the temperature compensation method for measuring the conductivity of ultrapure water as claimed in claim 1 are executed.

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