An ion migration type trace chloride ion measurement system and method

Abstract

The invention discloses an electric ion migration type trace chloride ion measurement system and method. A test solution chamber, a positive electrode support plate, a positive electrode anion exchange membrane, an anion exchange resin chamber, a negative electrode anion exchange membrane, a negative electrode plate and an enriched stock solution chamber are sequentially arranged in a shell from top to bottom, wherein the anion exchange resin chamber is filled with anion exchange resin; a chloride ion selective electrode is inserted into the test solution chamber, and the chloride ion selective electrode is connected to a chloride ion display instrument; a sample water inlet pipeline is connected to the inlet of the test solution chamber and the inlet of the enriched stock solution chamber through a sample injection pump; the outlet of the test solution chamber and the outlet of the enriched stock solution chamber are connected to the sample water outlet pipeline through a discharge pump; the positive electrode of a constant current power supply is connected to the positive electrode plate, and the negative electrode of the constant current power supply is connected to the negative electrode plate. The system and method can reduce the lower limit of chloride ion detection by a traditional electrode method to 0.5 μg / L.

Description

Technical Field

[0001] The invention belongs to the technical field of analysis and detection, and relates to an electric ion migration type trace chloride ion measurement system and method. Background Art

[0002] With the rapid development of the power industry, large-capacity and high-parameter supercritical and ultra-supercritical units continue to emerge, and power plants have put forward higher requirements for water vapor quality. Chloride ions are the most harmful active anions in the water vapor system. Trace amounts of chloride ions in the water vapor system are enough to destroy the integrity of the oxide protective film on the metal surface. Therefore, the online measurement of trace chloride ions is critical to timely detect changes in water vapor quality, adjust operating conditions, and ensure the safe operation of thermal systems. The GB / T12145-2016 "Water Steam Quality for Thermal Power Generators and Steam Power Equipment" standard requires that the chloride ion mass concentration of the outlet water of the unit fine treatment system with a drum pressure greater than 15.8MPa be less than 1μg / L. With the promotion and implementation of GB / T 12145-2016, chloride ions have become an important control indicator for water vapor supervision in power plants. The online measurement of trace chloride ions in the water vapor system is of great significance for real-time monitoring of chloride ion mass concentration in power plants.

[0003] At present, the main methods for determining chloride ions include titration, spectrophotometry, ion chromatography, electrode method, etc. The measurement range of chloride ions detected by titration is 5-150 mg / L, which is not suitable for the analysis and detection of trace chloride ions. The spectrophotometry method requires the sample to be treated with a colorimetric agent before measurement. Since the agent contains mercury, a highly toxic heavy metal, this measurement method has not been fully promoted. The only method recognized at home and abroad to detect trace chloride ions is ion chromatography. However, ion chromatographs are expensive, have high maintenance costs, require a large maintenance workload, and are not easy to achieve online measurement.

[0004] The electrode method is to use a chloride ion selective electrode to directly measure the chloride ions in water. This electrode only responds to the chloride ions in water, but the current detection limit of the chloride ion selective electrode is only 5μg / L due to the manufacturing process. The power industry specification requires that some chloride ion measurement points be controlled within 1μg / L, so the detection limit of the measurement method that meets this measurement requirement should reach 0.5μg / L. The current traditional electrode method used to measure trace chloride ions cannot meet this measurement requirement. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and to provide an ion migration type trace chloride ion measurement system and method, which can reduce the lower limit of chloride ion detection by traditional electrode method to 0.5 μg / L to meet the requirements of trace chloride ion detection in the current power industry.

[0006] To achieve the above object, the trace chloride ion measurement system of the electric ion migration type of the present invention comprises a housing, a chloride ion selective electrode, a chloride ion display instrument, a sample water inlet pipe, a sample injection pump, a discharge pump, a sample water outlet pipe and a constant current power supply;

[0007] The shell is provided with a test solution chamber, a positive electrode support plate, a positive electrode anion exchange membrane, an anion exchange resin chamber, a negative electrode anion exchange membrane, a negative electrode plate and an enriched stock solution chamber from top to bottom, wherein the anion exchange resin chamber is filled with anion exchange resin;

[0008] The chloride ion selective electrode is inserted into the chamber of the solution to be tested, and the chloride ion selective electrode is connected to the chloride ion display instrument; the sample water inlet pipeline is connected to the inlet of the chamber of the solution to be tested and the inlet of the enriched stock solution chamber through the injection pump; the outlet of the chamber of the solution to be tested and the outlet of the enriched stock solution chamber are connected to the sample water outlet pipeline through the discharge pump; the positive electrode of the constant current power supply is connected to the positive electrode plate, and the negative electrode of the constant current power supply is connected to the negative electrode plate.

[0009] It also includes a three-way injection valve, wherein the sample water inlet pipeline is connected to the first opening of the three-way injection valve via the injection pump, the second opening of the three-way injection valve is connected to the inlet of the chamber for the solution to be tested, and the third opening of the three-way injection valve is connected to the inlet of the enriched stock solution chamber;

[0010] It also includes a discharge three-way valve, the outlet of the test solution chamber is connected to the first opening of the discharge three-way valve, the outlet of the enriched stock solution chamber is connected to the second opening of the discharge three-way valve, and the third opening of the discharge three-way valve is connected to the sample water outlet pipeline through a discharge pump.

[0011] The shell is provided with a test solution chamber, a positive electrode support plate, a positive electrode plate, a positive electrode anion exchange membrane, an anion exchange resin chamber, a negative electrode anion exchange membrane, a negative electrode plate, a negative electrode support plate and an enriched stock solution chamber from top to bottom, wherein the anion exchange resin chamber is filled with anion exchange resin.

[0012] It also includes an overflow valve and an overflow water outlet pipe. The overflow port on the top side of the enriched raw liquid chamber is connected to the overflow water outlet pipe through the overflow valve.

[0013] The shell is an inverted T-shaped structure.

[0014] The outlet of the enriched stock solution chamber is arranged on the side of the bottom of the enriched stock solution chamber, and the outlet of the test solution chamber is arranged on the side of the bottom of the test solution chamber.

[0015] The positive electrode plate, the negative electrode plate, the positive support plate and the negative support plate are all provided with circular holes for distributing water.

[0016] The sample injection pump uses a peristaltic pump;

[0017] The discharge pump uses a vacuum pump.

[0018] The method for measuring trace chloride ions by electric ion migration of the present invention comprises the following steps:

[0019] The sample water sample enters the test solution chamber and the enrichment stock solution chamber through the injection pump, and the overflow valve is opened at the same time;

[0020] Start the constant current power supply, and provide a constant current to the positive electrode plate and the negative electrode plate through the constant current power supply. Under the action of the electric field, the chloride ions in the enriched stock solution migrate to the solution to be tested to complete the work of enriching the chloride ions;

[0021] When all the chloride ions in the enriched stock solution migrate to the solution to be tested, the chloride ion content in the solution to be tested is measured by the chloride ion selective electrode, and the detection signal is transmitted to the chloride ion display instrument. The ratio of the chloride ion content in the solution to be tested to the chloride ion content in the original sample water is calculated according to the volume ratio of the solution to be tested and the enriched stock solution. The detection value of the chloride ion selective electrode obtained by the chloride ion display instrument is divided by the ratio to obtain the chloride ion content of the sample water.

[0022] The present invention has the following beneficial effects:

[0023] The ion migration type trace chloride ion measurement system and method described in the present invention, during specific operation, utilizes the principle of ion migration to enrich chloride ions into a sample to be tested, thereby doubling the concentration of chloride ions in the sample to be tested, effectively improving the detection sensitivity of a traditional chloride ion electrode method, and raising the lower limit of chloride ion detection by the traditional electrode method to 0.5 μg / L, so that the electrode method can be used for water quality measurement points that originally could not meet the detection requirements. In addition, the present invention does not require consumption of any reagents, and only consumes a small amount of electric energy to achieve the purpose. The waste liquid after the measurement is completed can be directly discharged, which meets the waste liquid discharge requirements of the power industry, is green, environmentally friendly, simple to operate, and easy to maintain, further reducing the test cost of chloride ion detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the structure of the present invention.

[0025] Among them, 1 is a sample injection pump, 2 is a sample injection three-way valve, 3 is a test solution chamber, 4 is an enriched stock solution chamber, 5 is a chloride ion selective electrode, 6 is a chloride ion display instrument, 7 is an anion exchange resin chamber, 8 is a positive electrode support plate, 9 is a positive electrode plate, 10 is a positive anion exchange membrane, 11 is a negative anion exchange membrane, 12 is a negative electrode plate, 13 is a negative electrode support plate, 14 is a constant current power supply, 15 is an overflow valve, 16 is a discharge three-way valve, and 17 is a discharge pump. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only an embodiment of a part of the present invention, not all embodiments, and is not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concepts disclosed in the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention.

[0027] The accompanying drawings show schematic diagrams of structures according to embodiments disclosed in the present invention. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0028] refer to Figure 1 The trace chloride ion measurement system of the electric ion migration type of the present invention comprises a housing, a chloride ion selective electrode 5, a chloride ion display instrument 6, a sample water inlet pipe, a sample injection pump 1, a discharge pump 17, a sample water outlet pipe and a constant current power supply 14;

[0029] The shell is provided with a test solution chamber 3, a positive electrode support plate 8, a positive electrode plate 9, a positive electrode anion exchange membrane 10, an anion exchange resin chamber 7, a negative electrode anion exchange membrane 11, a negative electrode plate 12, a negative electrode support plate 13 and an enriched stock solution chamber 4 from top to bottom, wherein the anion exchange resin chamber 7 is filled with anion exchange resin.

[0030] The chloride ion selective electrode 5 is inserted into the solution chamber 3 to be tested, and the chloride ion selective electrode 5 is connected to a chloride ion display meter 6 .

[0031] The sample water inlet pipeline is connected to the first opening of the injection three-way valve 2 through the injection pump 1, the second opening of the injection three-way valve 2 is connected to the inlet of the test solution chamber 3, and the third opening of the injection three-way valve 2 is connected to the inlet of the enriched stock solution chamber 4.

[0032] The outlet of the test solution chamber 3 is connected to the first opening of the discharge three-way valve 16, the outlet of the enriched stock solution chamber 4 is connected to the second opening of the discharge three-way valve 16, and the third opening of the discharge three-way valve 16 is connected to the sample water outlet pipe through the discharge pump 17.

[0033] The positive pole of the constant current power supply 14 is connected to the positive electrode plate 9, and the negative pole of the constant current power supply 14 is connected to the negative electrode plate 12; the overflow port on the top side of the enriched raw liquid chamber 4 is connected to the overflow water outlet pipe through the overflow valve 15; the shell is an inverted T-shaped structure.

[0034] It should be noted that the positive electrode support plate 8, the positive electrode plate 9, and the positive electrode anion exchange membrane 10 together constitute the positive electrode for ion migration; the negative electrode support plate 13, the negative electrode plate 12, and the negative electrode anion exchange membrane 11 together constitute the negative electrode for ion migration. The anion exchange resin is placed between the positive electrode for ion migration and the negative electrode for ion migration as the anion exchange resin chamber 7. The constant current power supply 14 is connected to the positive electrode plate 9 and the negative electrode plate 12 to provide a constant current as a power source for the ion migration process.

[0035] Specifically, the injection pump 1 uses a peristaltic pump, the flow rate requirement is 100 mL / min, and the flow rate error is within 1%.

[0036] The discharge pump 17 uses a vacuum pump, and the flow rate is required to be 250 mL / min.

[0037] The injection three-way valve 2, the relief valve 15 and the discharge three-way valve 16 can be electrically controlled, and the power supply voltage is DC 24V. After power is turned on, the three-way valve can switch between the two flow paths, and the relief valve 15 can control the flow path to open and close. The outlet of the enriched stock solution chamber 4 is set on the side of the bottom of the enriched stock solution chamber 4, and the outlet of the test solution chamber 3 is set on the side of the bottom of the test solution chamber 3, ensuring that the test solution chamber 3 and the enriched stock solution chamber 4 can completely discharge the residual solution.

[0038] The test solution chamber 3 and the enriched stock solution chamber 4 are made of organic glass material. The volume of the test solution chamber 3 is 100 mL. When the inflow volume of the test solution reaches 50 mL, it occupies 2 / 3 of the height of the test solution chamber 3; the volume of the enriched stock solution chamber 4 is 450 mL.

[0039] The positive support plate 8 and the negative support plate 13 are made of polytetrafluoroethylene material with a thickness of 5 mm. Water distribution circular holes with a diameter of 1 mm are evenly distributed on the positive support plate 8 and the negative support plate 13 to evenly distribute the solution on the positive electrode plate 9 and the negative electrode plate 12 so that the solution can fully contact the positive electrode plate 9 and the negative electrode plate 12.

[0040] The positive electrode plate 9 and the negative electrode plate 12 are made of platinum material with a thickness of 0.2 mm. Water distribution circular holes with a diameter of 1 mm are evenly distributed on the positive electrode plate 9 and the negative electrode plate 12 so that the solution can fully contact the anion exchange resin 7 membrane.

[0041] The positive electrode anion exchange membrane 10 and the negative electrode anion exchange membrane 11 are anion selective permeable membranes, which do not allow aqueous solution to pass through but only allow anions to pass through. The model of the membrane is: EDI-3364.

[0042] The model of the anion exchange resin is 201×7, and the resin state is the hydroxyl type. The resin is kept in a wet state and filled into the anion exchange resin cavity 7, and the filling volume is 50 mL.

[0043] The constant current power supply 14 can provide 24V DC voltage and 200mA constant current.

[0044] The model of the chloride ion selective electrode 5 is: CL-100025, the detection limit is 5 μg / L, and the measurement range is (5-10000) μg / L.

[0045] The method for measuring trace chloride ions by electric ion migration of the present invention comprises the following steps:

[0046] The sample water sample flows through the injection pump 1 to the injection three-way valve 2, and then enters the test solution chamber 3 through the injection three-way valve 2. The volume of the test solution is controlled to be 50 mL according to the running time and the flow rate of the injection pump 1. Then the injection three-way valve 2 is switched to allow the sample water sample to enter the enriched stock solution chamber 4, and the overflow valve 15 is opened at the same time. According to the running time and the flow rate control of the injection pump 1, the injection pump 1 is started, and the enriched stock solution chamber 4 is filled with the enriched stock solution and overflowed, and then the injection pump 1 and the overflow valve 15 are closed, and the sample injection step is completed.

[0047] The volume of the test solution is 50 mL, the volume of the enriched stock solution is 450 mL, and the chloride ion contents in the test solution and the enriched stock solution are the same when the sample injection step is completed.

[0048] The constant current power supply 14 is started, and a constant current of 200 mA is provided to the positive electrode plate 9 and the negative electrode plate 12 through the constant current power supply 14 for 5 minutes. Under the action of the electric field, the chloride ions in the enriched stock solution migrate to the solution to be tested to complete the work of enriching chloride ions. According to the volume ratio of the solution to be tested and the enriched stock solution, the chloride ion content in the solution to be tested is calculated to be 10 times the content before enrichment, wherein the migration principle of chloride ions under the action of the electric field is:

[0049] According to the basic principle of ion migration, direct current is applied to the two electrode plates in the water, and the anions in the water will migrate to the positive electrode plate 9, and the cations in the water will migrate to the negative electrode plate 12. Chloride ions are anions, so chloride ions migrate to the positive electrode plate 9 under the action of the electric field. The electrode plate on the enriched stock solution side is the negative electrode plate 12, and the electrode plate on the tested stock solution side is the positive electrode plate 9. When powered on, chloride ions will migrate from the enriched stock solution side to the tested solution side. The chloride ions on the enriched stock solution side first migrate to one side of the negative anion exchange membrane 11 through the negative support plate 13 and the negative electrode plate 12, wherein the negative support plate 13 and the negative electrode plate 12 have uniform water distribution circular holes, and the aqueous solution containing chloride ions can flow on the negative support plate 13 and the negative electrode plate 12. When the chloride ions reach the negative anion exchange membrane 11, they pass through one side of the negative anion exchange membrane 11 to the other side of the negative anion exchange membrane 11, wherein the aqueous solution is blocked by the negative anion exchange membrane 11 and cannot penetrate, and at the same time, the following electrode reactions will occur on the surface of the positive electrode plate 9 and the negative electrode plate 12 when the power is on:

[0050] 2H2O+2e - →2OH - +H2 (negative electrode plate 12)

[0051] H2O→2H + +1 / 2O2+2e - (Positive electrode plate 9)

[0052] According to the above electrode reaction, hydroxide ions are simultaneously generated on the negative electrode plate 12. The hydroxide ions carry a negative charge and have the same properties as chloride ions. The hydroxide ions and chloride ions migrate to the positive electrode plate 9 together under the action of the electric field. Anion exchange resin is a resin carrying hydroxide ion groups. Chloride ions can replace the hydroxide groups on the anion exchange resin. Then, the hydroxide ions that arrive at the surface of the anion exchange resin 7 together with the chloride ions replace the chloride ions on the anion exchange resin. The process of repeated replacement of chloride ions and hydroxide ions is actually the process of chloride ion migration. Under the action of the electric field, the chloride ions continue to move toward the positive electrode plate 9. When the chloride ions reach the positive anion exchange membrane 10, they enter the other side of the positive anion exchange membrane 10 from one side of the positive anion exchange membrane 10 and finally dissolve in the solution to be tested.

[0053] For ease of understanding, it should be noted that, in fact, the negative electrode plate 12, the negative anion exchange membrane 11, the anion exchange resin 7, the positive anion exchange membrane 10 and the positive electrode plate 9 constitute a small resistance element. When direct current is applied to both sides of the resistance element, the negatively charged chloride ions will migrate from the negative electrode plate 12 to the positive electrode plate 9, that is, the positive electrode plate 9 and the negative electrode plate 12 provide a power source for the chloride ion migration, and the anion exchange resin 7, the positive anion exchange membrane 10 and the negative anion exchange membrane 11 realize the role of the chloride ion migration transmission channel.

[0054] When all the chloride ions in the enriched stock solution migrate to the test solution, the chloride ion content in the test solution is measured by the chloride ion selective electrode 5, and the detection signal is transmitted to the chloride ion display instrument 6. According to the volume ratio of the test solution and the enriched stock solution, the chloride ion content in the test solution at this time is calculated to be 10 times the chloride ion content in the original sample water. Therefore, the chloride ion display instrument 6 finally divides the electrode detection signal by 10 to obtain the chloride ion content of the sample water. The detection lower limit of the chloride ion selective electrode 5 is 5 μg / L. After dividing by 10, the detection lower limit can reach 0.5 μg / L, and the detection lower limit is reduced by 10 times.

[0055] After the measurement is completed, first turn off the constant current power supply 14, then switch the discharge three-way valve 16 to drain the test solution in the test solution chamber 3, and then switch the discharge three-way valve 16 to drain the enriched stock solution in the enriched stock solution chamber 4 to complete the entire solution discharge process.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. An ion migration type trace chloride ion measurement system, characterized in that: It comprises a housing, a chloride ion selective electrode (5), a chloride ion display instrument (6), a sample water inlet pipe, a sample injection pump (1), a discharge pump (17), a sample water outlet pipe and a constant current power supply (14); The chloride ion selective electrode (5) is inserted into the test solution chamber (3), and the chloride ion selective electrode (5) is connected to the chloride ion display instrument (6); the sample water inlet pipeline is connected to the inlet of the test solution chamber (3) and the inlet of the enriched stock solution chamber (4) through the sample injection pump (1); the outlet of the test solution chamber (3) and the outlet of the enriched stock solution chamber (4) are connected to the sample water outlet pipeline through the discharge pump (17); the positive electrode of the constant current power supply (14) is connected to the positive electrode plate (9), and the negative electrode of the constant current power supply (14) is connected to the negative electrode plate (12); The housing is provided with a test solution chamber (3), a positive electrode support plate (8), a positive electrode plate (9), a positive electrode anion exchange membrane (10), an anion exchange resin chamber (7), a negative electrode anion exchange membrane (11), a negative electrode plate (12), a negative electrode support plate (13) and an enriched stock solution chamber (4) in order from top to bottom, wherein the anion exchange resin chamber (7) is filled with an anion exchange resin; The positive electrode plate (9), the negative electrode plate (12), the positive electrode support plate (8) and the negative electrode support plate (13) are all provided with circular water distribution holes; It also includes a three-way injection valve (2), wherein a sample water inlet pipeline is connected to a first opening of the three-way injection valve (2) via an injection pump (1), a second opening of the three-way injection valve (2) is connected to an inlet of a test solution chamber (3), and a third opening of the three-way injection valve (2) is connected to an inlet of an enriched stock solution chamber (4); It also includes a discharge three-way valve (16), the outlet of the test solution chamber (3) is connected to the first opening of the discharge three-way valve (16), the outlet of the enriched stock solution chamber (4) is connected to the second opening of the discharge three-way valve (16), and the third opening of the discharge three-way valve (16) is connected to the sample water outlet pipeline via a discharge pump (17); It also includes an overflow valve (15) and an overflow water outlet pipe, wherein the overflow port on the top side of the enriched raw liquid chamber (4) is connected to the overflow water outlet pipe through the overflow valve (15); The housing is an inverted T-shaped structure; The outlet of the enriched stock solution chamber (4) is arranged on the side of the bottom of the enriched stock solution chamber (4), and the outlet of the test solution chamber (3) is arranged on the side of the bottom of the test solution chamber (3).

2. The trace chloride ion measurement system of the electric ion migration type according to claim 1, characterized in that: The sample injection pump (1) uses a peristaltic pump; A vacuum pump is used as the discharge pump (17).

3. An ion migration method for measuring trace chloride ions, characterized in that: The trace chloride ion measurement system based on the electric ion migration type according to claim 2 comprises the following steps: The sample water sample enters the test solution chamber (3) and the enriched stock solution chamber (4) through the sample injection pump (1), and the overflow valve (15) is opened at the same time; Starting the constant current power supply (14), providing a constant current to the positive electrode plate (9) and the negative electrode plate (12) through the constant current power supply (14), and under the action of the electric field, the chloride ions in the enriched stock solution migrate to the solution to be tested to complete the work of enriching the chloride ions; When all the chloride ions in the enriched stock solution migrate to the solution to be tested, the chloride ion content in the solution to be tested is measured by the chloride ion selective electrode (5), and the detection signal is transmitted to the chloride ion display instrument (6). The ratio of the chloride ion content in the solution to be tested to the chloride ion content in the original sample water is calculated according to the volume ratio of the solution to be tested and the enriched stock solution. The detection value of the chloride ion selective electrode (5) obtained by the chloride ion display instrument (6) is then divided by the ratio to obtain the chloride ion content of the sample water.

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