Sampling device and method for dissolved carbon dioxide in circulating cooling water and measuring method

Abstract

The invention provides a sampling device and method for dissolved carbon dioxide in circulating cooling water and a measuring method. The sampling device for dissolved carbon dioxide in circulating cooling water comprises a sampling pipeline stop valve, a sampling hose, a drain valve, a sample discharging hose and a soft sampling bag. And a sampling pipeline stop valve is arranged on the sampling hose. One end of the sampling hose is connected to the top end of the soft sampling bag. And the other end of the sampling hose is connected with a process system sampling valve pipeline. And the bottom end of the soft sampling bag is connected with a sample discharging hose. And a drain valve is arranged on the sample discharging hose. And the top end of the soft sampling bag is also provided with a sample inlet containing a rubber plug. The sample inlet containing the rubber plug is used for being connected with a total organic carbon tester. According to the sampling device, the soft sampling bag is arranged in the sampling device for sampling from the process system pipeline, so that the problem of low measurement accuracy of dissolved carbon dioxide in the prior art is solved.

Description

Technical Field

[0001] The present application belongs to the technical field of dissolved carbon dioxide measurement, and specifically relates to a sampling device and method, and a measurement method for dissolved carbon dioxide in circulating cooling water. Background Art

[0002] The nuclear energy heating project uses the secondary circuit steam produced by the nuclear power plant to heat the industrial feed water through a heat conversion device to produce industrial steam. The water body of the heating steam and industrial steam of this project is the circulating water (cooling water) in the closed system, and the water source is treated by a demineralization resin bed. During the water quality supervision of the nuclear energy heating project, it was found that when the process system has a vacuum defect in the secondary circuit condenser or the water replenishment is too high, and the desalting water tank is not covered with inert gas for deoxidation and decarbonization, carbon dioxide in the air will leak into the system. When carbon dioxide gas dissolves in cooling water, carbonic acid is generated, and carbonic acid hydrolyzes to generate hydrogen ions, bicarbonate ions, and carbonate ions, which will affect water quality indicators such as cationic conductivity and pH. In the nuclear energy heating project, the heating steam and industrial steam are required to have a cationic conductivity of ≤0.2μs / cm, the industrial feed water has a cationic conductivity of ≤0.5μs / cm, and the pH 25 The requirement is 9.0-9.6, which is relatively strict. When these water quality indicators are abnormal, accurate measurement of dissolved carbon dioxide in water can confirm the abnormal air tightness in the process system and correct the chemical monitoring indicators, which is extremely important for the supervision of water quality in nuclear energy heating projects.

[0003] There are two difficulties in measuring the concentration of carbon dioxide in circulating cooling water: 1. During the sampling and measurement process, carbon dioxide in the air is easily soluble in water, which has a great impact on the measurement of dissolved carbon dioxide; 2. There is no standard sample to verify the accuracy of the measurement of dissolved carbon dioxide in water. Summary of the invention

[0004] In view of this, the embodiments of the present application are committed to providing a sampling device, method and measurement method for dissolved carbon dioxide in circulating cooling water. A soft sampling bag is set in the sampling device to take samples from the process system pipeline to solve the problem of low accuracy of existing measurements of dissolved carbon dioxide.

[0005] The first aspect of the present application provides a sampling device for dissolved carbon dioxide in circulating cooling water, which comprises a sampling pipeline stop valve, a sampling hose, a drain valve, a drain hose and a soft sampling bag. The sampling hose is provided with a sampling pipeline stop valve. One end of the sampling hose is connected to the top of the soft sampling bag. The other end of the sampling hose is used to connect to the sampling valve pipeline of the process system. The bottom end of the soft sampling bag is connected to a drain hose. The drain hose is provided with a drain valve. The top of the soft sampling bag is also provided with a rubber plugged sampling port. The rubber plugged sampling port is used to connect to a total organic carbon analyzer.

[0006] A second aspect of the present application provides a method for sampling dissolved carbon dioxide in circulating cooling water, which comprises a cleaning process, an exhaust process and a sampling process.

[0007] Cleaning process: connect the sampling hose of the sampling device for dissolving carbon dioxide in circulating cooling water provided by the first aspect of the present application to the sampling valve pipeline of the process system, open the stop valve of the sampling pipeline, fill the soft sampling bag, and then drain the air and excess water through the drain valve. Repeat the cleaning of the soft sampling bag for multiple times, and finally fill the soft sampling bag, and close the stop valve and drain valve of the sampling pipeline.

[0008] Exhaust process: point the drain port of the soft sampling bag vertically downward, open the drain valve to drain the water in the soft sampling bag, close the drain valve, and finally make the soft sampling bag in a vacuum compressed state.

[0009] Sampling process: Open the stop valve of the sampling pipeline, fill the soft sampling bag and close the stop valve of the sampling pipeline. Disconnect the sampling hose from the sampling pipeline of the process system to obtain the circulating cooling water sample and store it in a cool place.

[0010] The third aspect of the present application provides a method for measuring dissolved carbon dioxide in circulating cooling water, which comprises: inserting a metal injection needle connected to an injection tube in a total organic carbon analyzer into a soft sampling bag from a rubber stopper-containing injection port of a sampling device for dissolved carbon dioxide in circulating cooling water in an embodiment of the present application for sampling; clicking on the measurement of the total organic carbon analyzer, and using the total organic carbon analyzer to measure the inorganic carbon concentration.

[0011] In a specific embodiment of the present application, before measuring the inorganic carbon concentration using the total organic carbon analyzer, the method for measuring dissolved carbon dioxide in the circulating cooling water further includes: obtaining a standard measurement curve.

[0012] In a specific embodiment of the present application, after the inorganic carbon concentration is measured using the total organic carbon meter as mentioned above, the method for measuring dissolved carbon dioxide in the circulating cooling water also includes: using a syringe to take an appropriate amount of high-purity carbon dioxide gas and inject it into a soft sampling bag, and after the gas is completely dissolved, measuring the inorganic carbon concentration before and after the injection, and calculating the spike recovery rate.

[0013] The beneficial effects of the technical solution of the present application are: by using a soft sampling bag to take samples from the process system pipeline, a cleaning process is performed before the sampling process to ensure the representativeness of the sample; after the cleaning process, an exhaust process is performed, and after the soft sampling bag is discharged through the water body, the sampling bag presents a vacuum form, which ensures that all carbon dioxide in the air is discharged; in addition, after sampling, the inlet valve and the drain valve of the soft sampling bag are closed and stored in a cool place to prevent air from entering the soft sampling bag and causing pollution. The embodiment of the present application proposes for the first time the use of an offline soft sampling tool, a sampling method that achieves a vacuum effect by flushing and discharging samples, isolating the interference of carbon dioxide in the air on the sample during the sampling process, so that the offline sample has the advantages of online portable sampling. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Shown is a schematic diagram of the structure of a sampling device for dissolved carbon dioxide in circulating cooling water provided in one embodiment of the present application.

[0015] Figure 2 Shown Figure 1 The schematic diagram of the structure of the sampling device for dissolved carbon dioxide in circulating cooling water when used for measurement is shown. DETAILED DESCRIPTION

[0016] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0017] At least one embodiment of the present application provides a sampling device for dissolved carbon dioxide in circulating cooling water, referring to Figure 1 The sampling device for dissolved carbon dioxide in the circulating cooling water comprises a sampling pipeline stop valve 1, a sampling hose 2, a drain valve 3, a drain hose 4, and a soft sampling bag 5. The sampling hose 2 is provided with a sampling pipeline stop valve 1. One end of the sampling hose 2 is connected to the top of the soft sampling bag 5. The other end of the sampling hose 2 is used to connect to the sampling valve pipeline of the process system. The bottom end of the soft sampling bag 5 is connected to the drain hose 4. The drain valve 3 is provided on the drain hose 4. The top of the soft sampling bag 5 is also provided with a rubber plug sampling port 6. The rubber plug sampling port 6 is used to connect to a total organic carbon analyzer.

[0018] At least one embodiment of the present application further provides a method for sampling dissolved carbon dioxide in circulating cooling water, which uses the sampling device for sampling dissolved carbon dioxide in circulating cooling water in the above embodiment of the present application to perform sampling. The method for sampling dissolved carbon dioxide in circulating cooling water includes the following steps.

[0019] Cleaning process: connect the sampling hose 2 of the sampling device for dissolving carbon dioxide in circulating cooling water of the embodiment of the present application to the sampling valve pipeline of the process system, open the stop valve 1 of the sampling pipeline, fill the soft sampling bag 5, and then drain the air and excess water through the drain valve 3. Repeat the cleaning of the soft sampling bag 5 for several times, and finally fill the soft sampling bag 5, and close the stop valve 1 and drain valve 3 of the sampling pipeline.

[0020] Exhaust process: point the drain port of the soft sampling bag 5 vertically downward, open the drain valve 3 to drain the water in the soft sampling bag 5, close the drain valve 3, and finally make the soft sampling bag 5 in a vacuum compressed state.

[0021] Sampling process: Open the sampling pipeline stop valve 1, fill the soft sampling bag 5 and then close the sampling pipeline stop valve 1. Disconnect the sampling hose 2 from the process system sampling pipeline to obtain the circulating cooling water sample and store it in a cool place.

[0022] It should be noted that in order to prevent the infiltration of carbon dioxide from the air, the circulating cooling water sample should be measured as soon as possible.

[0023] According to the technical solution provided in the embodiment of the present application, a soft sampling bag is used to take samples from the process system pipeline. A cleaning process is performed before the sampling process to ensure the representativeness of the sample; an exhaust process is performed after the cleaning process. After the soft sampling bag is discharged through the water body, the sampling bag presents a vacuum form, which ensures that all carbon dioxide in the air is discharged; in addition, after sampling, the inlet valve and the drain valve of the soft sampling bag 5 are closed and stored in a cool place to prevent air from entering the soft sampling bag 5 and causing contamination. The embodiment of the present application proposes for the first time the use of an offline soft sampling tool, a sampling method that achieves a vacuum effect by flushing and discharging the sample, isolating the interference of carbon dioxide in the air on the sample during the sampling process, so that the offline sample has the advantages of online portable sampling.

[0024] At least one embodiment of the present application further provides a method for measuring dissolved carbon dioxide in circulating cooling water, and the method for measuring dissolved carbon dioxide in circulating cooling water is used to measure the above-mentioned circulating cooling water sample. Figure 2 The method for measuring dissolved carbon dioxide in circulating cooling water includes the following steps.

[0025] S1: insert the metal injection needle 8 connected to the injection line 7 in the total organic carbon analyzer 9 into the soft sampling bag 5 from the rubber plug injection port 6 of the sampling device for dissolving carbon dioxide in the circulating cooling water of the embodiment of the present application to take samples.

[0026] The total organic carbon analyzer may be referred to as a TOC analyzer. For example, the total organic carbon analyzer may be an M9 TOC analyzer produced by Suez Company of the United States.

[0027] It should be noted that, before measurement, the ICR (carbon removal function) in the total organic carbon analyzer 9 can be turned off to save the measurement mode.

[0028] S2: Click on the measurement of the total organic carbon analyzer 9 to measure the inorganic carbon concentration using the total organic carbon analyzer 9.

[0029] According to the technical solution provided in the embodiment of the present application, the total organic carbon analyzer 9 is used to directly insert the soft sampling bag 5 from the sampling port 6 containing the rubber stopper to take samples, thereby ensuring that air interference is prevented during the measurement of inorganic carbon, thereby improving the accuracy of the measurement. In addition, it is proposed that after the inorganic carbon in the circulating cooling water after the desalination bed has been completely absorbed by the bed, the carbon dioxide content dissolved in the water again can be measured by measuring the inorganic carbon, and the content of dissolved carbon dioxide can be obtained through the conversion relationship between carbon and carbon dioxide. In addition, because the measurement method has a good isolation effect on carbon dioxide in the air, it has great advantages for measuring low concentrations (0.015mg / L-0.1mg / L) of dissolved carbon dioxide in circulating cooling water in a closed system, and can reflect the low concentration of carbon dioxide content in the water body.

[0030] The following is an example of the measurement principle used in the method for measuring dissolved carbon dioxide in circulating cooling water.

[0031] After the closed water body passes through the desalination bed, the carbon dioxide, carbonate, bicarbonate and other inorganic carbon-containing substances in the water have been completely absorbed. In the subsequent process system flow, if carbon dioxide in the air is inhaled due to defects or design reasons, carbonate and bicarbonate ions will be regenerated, which can be measured by the inorganic carbon measurement in the TOC instrument. Finally, combined with the following formula 1, the carbon dioxide content is obtained by converting the molar mass of inorganic carbon (abbreviated as IC) and carbon dioxide.

[0032] IC / CO2=12 / 44Formula 1

[0033] The measurement principle of inorganic carbon in the TOC instrument is as follows: the sample is sucked into the instrument through the sampling pump and then acidified to generate carbon dioxide gas. The carbon dioxide gas passes through a breathable membrane and then dissolves in the deionized water circuit. Finally, the content is quantitatively detected through a conductivity detection cell.

[0034] In at least one embodiment of the present application, before the inorganic carbon concentration is measured by the total organic carbon analyzer 9, the method for measuring dissolved carbon dioxide in the circulating cooling water further includes S01.

[0035] S01: Obtain a standard measurement curve.

[0036] For example, accurately weigh 0.0221g and 0.0442g (accurate to 0.1mg) of standard sodium carbonate solution and dissolve them in 1 liter of carbon dioxide-free water. This solution is used as IC standard 2.5mg / L and 5mg / L to draw the standard measurement curve. You can also directly use the manufacturer's IC standard solution 5mg / L and dilute it with carbon dioxide-free water to draw the standard curve.

[0037] Preparation method of carbon dioxide-free water is prepared according to national standard GB8538-2022: Boil water for 15 minutes, then cool to room temperature without contact with atmospheric carbon dioxide. The pH of this water should be greater than 6.0, otherwise the boiling time should be extended. Prepare it when needed.

[0038] Using high-purity water as the background, the dissolved carbon dioxide concentration was calculated according to the following formula 2.

[0039]

[0040] In formula 2, C (CO2) : Carbon dioxide concentration, mg / L; Conversion measurement efficiency, %;

[0041] IC 测量值 : Sample inorganic carbon concentration, mg / L; IC 本底 : Background inorganic carbon concentration, mg / L.

[0042] In at least one embodiment of the present application, after the above S2, the method for measuring dissolved carbon dioxide in circulating cooling water further includes the following steps.

[0043] S3: Use a syringe to take an appropriate amount of high-purity carbon dioxide gas and inject it into the soft sampling bag 5. After the gas is completely dissolved, measure the inorganic carbon concentration before and after the injection and calculate the spike recovery rate.

[0044] Specifically, under standard atmospheric pressure, use a syringe to draw an appropriate volume of high-purity carbon dioxide (e.g., 1 mL) from a high-purity carbon dioxide standard gas cylinder, then inject it into the sample from the rubber stoppered injection port 6, shake it slowly until the gas is completely dissolved, and then measure the IC. After the measurement, pour out the water in the soft sampling bag 5 to measure the volume of the water sample.

[0045] In the above embodiment, a standard sample of dissolved carbon dioxide is obtained by injecting high-purity carbon dioxide into a soft sampling bag 5, and the recovery rate of the spiked sample is calculated by a spiked method to verify the accuracy of the measurement method.

[0046] For example, the theoretical added carbon dioxide concentration is calculated by the following formula 3.

[0047] C CO2加标 =V CO2 / Vm ×44 / V H2O Formula 3

[0048] In formula 3, C CO2加标 : added carbon dioxide concentration, mg / L; V CO2 : Added carbon dioxide standard gas, mL; V H2O : Volume of water sample in sampling bag, L; V m : The molar volume of gas at 25°C and 101 kPa is 24.5, L / mol.

[0049] The spike recovery rate was calculated using the following formula 4.

[0050] Spiked recovery rate = (spiked test value - test measurement value) ÷ spiked amount × 100% Formula 4

[0051] For example, using a high-purity water meter to make water (conductivity at 25°C: 0.056μs / cm), the IC value measured by the above sampling and measurement method is 0.003mg / L, and the carbon dioxide concentration is converted as the background value measured by this method. The spike recovery rate is calculated by injecting high-purity carbon dioxide gas into high-purity water, and the test results are shown in Table 1 below.

[0052] Table 1 Test results

[0053]

[0054] The spiked recoveries of the method for measuring the concentration of dissolved carbon dioxide in circulating cooling water were all within 110%, indicating that the measurement method had a small error and could be used to measure the content of dissolved carbon dioxide in circulating cooling water.

[0055] The above-mentioned embodiments of the present application aim to solve the problem that the sampling and measurement of dissolved carbon dioxide in existing circulating cooling water is easily affected by carbon dioxide in the air. A method for improving the measurement accuracy of dissolved carbon dioxide concentration in water samples is provided, so that the circulating cooling water samples can maintain the original dissolved carbon dioxide content in the process system during the sampling and measurement process, reduce the disturbance influence of external factors, and verify the measurement accuracy of dissolved gas concentration by means of spiking method.

[0056] It should be noted that the combination of the various technical features in the embodiments of the present application is not limited to the combination described in the embodiments of the present application or the combination described in the specific embodiments, and all technical features described in the present application can be freely combined or combined in any way unless there is a contradiction between them.

[0057] As shown in this application and claims, unless the context clearly indicates an exception, the words "a", "an" and / or "the" do not refer to the singular and may also include the plural. Generally speaking, the term "comprising" only indicates that the steps and elements that have been clearly identified are included, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0058] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A sampling device for dissolved carbon dioxide in circulating cooling water, characterized in that: Including sampling pipeline stop valve, sampling hose, drain valve, drain hose and soft sampling bag, The sampling hose is provided with the sampling pipeline stop valve, one end of the sampling hose is connected to the top of the soft sampling bag, the other end of the sampling hose is used to be connected to the sampling valve pipeline of the process system, the bottom end of the soft sampling bag is connected to the sampling hose, the sampling hose is provided with the drain valve, and the top of the soft sampling bag is also provided with a rubber stopper sampling port, and the rubber stopper sampling port is used to connect to the total organic carbon analyzer.

2. A method for sampling dissolved carbon dioxide in circulating cooling water, characterized in that: include: Cleaning process: connect the sampling hose of the sampling device for dissolving carbon dioxide in circulating cooling water as claimed in claim 1 to the sampling valve pipeline of the process system, open the stop valve of the sampling pipeline, fill the soft sampling bag, drain the air and excess water through the drain valve, repeat the cleaning of the soft sampling bag for many times, finally fill the soft sampling bag, and close the stop valve and drain valve of the sampling pipeline; Exhaust process: point the drain port of the soft sampling bag vertically downward, open the drain valve to drain the water in the soft sampling bag, close the drain valve, and finally make the soft sampling bag in a vacuum compressed state; Sampling process: Open the stop valve of the sampling pipeline, fill the soft sampling bag and then close the stop valve of the sampling pipeline, disconnect the sampling hose from the sampling pipeline of the process system to obtain the circulating cooling water sample and store it in a cool place.

3. A method for measuring dissolved carbon dioxide in circulating cooling water, characterized in that: include: Insert the metal injection needle connected to the injection tube in the total organic carbon analyzer Insert the rubber plug inlet of the sampling device for dissolving carbon dioxide in circulating cooling water as claimed in claim 1 into a soft sampling bag for sampling; Click on the measurement of the total organic carbon meter to measure the inorganic carbon concentration using the total organic carbon meter.

4. The measuring method according to claim 3, characterized in that: Before using the total organic carbon analyzer to measure the inorganic carbon concentration, it also includes: Obtain a standard measurement curve.

5. The measuring method according to claim 3, characterized in that: After measuring the inorganic carbon concentration using the total organic carbon analyzer, it also includes: Use a syringe to take an appropriate amount of high-purity carbon dioxide gas and inject it into the soft sampling bag. After the gas is completely dissolved, measure the inorganic carbon concentration before and after injection and calculate the spike recovery rate.

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