Chlor-alkali ion membrane electrolysis test method

Abstract

The invention belongs to the field of fluorine-containing materials, and relates to a chlor-alkali ion membrane electrolysis test method. The invention aims to provide a test method suitable for scientific research and teaching environments, and accurate control of the chlor-alkali electrolysis process is realized. The method comprises the test steps of pretreatment of the chlor-alkali ionic membrane, assembly of the chlor-alkali ionic membrane, liquid filling of a cathode system and an anode system, heating and electrolysis evaluation. The method has the characteristics of convenience in operation, low energy consumption, high adaptability and the like, and is particularly suitable for research of a chlor-alkali electrolysis process, performance evaluation of a novel membrane material and exploration of an electrochemical reaction mechanism.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of fluorine-containing materials, and relates to a chlor-alkali ion membrane electrolysis test method. BACKGROUND

[0002] The chlor-alkali electrolysis process refers to a process of producing chlorine (Cl2), hydrogen (H2) and sodium hydroxide (NaOH) by electrolysis. This process has a wide range of applications in chemical industry, metallurgy, light industry, food industry, pharmaceutical industry and the like. The basic principle of the chlor-alkali electrolysis process is to use the electrode reactions of the positive and negative electrodes in the electrolytic cell to electrolyze brine (sodium chloride, NaCl).

[0003] The chlor-alkali electrolysis process currently mainly uses membrane electrolysis. The membrane electrolysis is to install an ion exchange membrane between the anode and the cathode, so that the products between the anode and the cathode are separated, and problems such as NaCl entrainment in the production of NaOH are prevented, so that the three products of Cl2, H2 and NaOH are collected separately. In the development process of the chlor-alkali industry, the ion exchange membrane has become the core component of the chlor-alkali electrolysis. In order to promote the technological progress of the ion exchange membrane and realize the stable and accurate test of the performance of the ion membrane electrolysis, it has become more and more important to more efficiently and accurately complete the experimental electrolysis test of the membrane. Various problems existing in the traditional electrolysis method are gradually exposed in the updating of the technology, such as high energy consumption, complex operation, fast membrane material loss and the like. SUMMARY

[0004] The chlor-alkali ion membrane electrolysis test method has the advantages of convenient operation, low energy consumption, good repeatability, high test efficiency, accurate test results and the like, can quickly and accurately test the electrochemical performance of the chlor-alkali ion membrane, and is especially suitable for the research of the chlor-alkali electrolysis process, the performance evaluation of new membrane materials and the exploration of the electrochemical reaction mechanism.

[0005] In order to achieve the above-mentioned purpose, the following technical scheme is adopted in the application: A chlor-alkali ion membrane electrolysis test method comprises the following steps: (1) soaking the chlor-alkali ion membrane to be tested in a NaOH solution to pretreat the chlor-alkali ion membrane; (2) loading the ion membrane into an electrolytic cell unit; (3) charging the liquid to the anode and cathode system: adding a NaOH solution with a concentration of 31-33 wt% to the cathode side of the electrolytic cell, and adding a NaCl solution with a concentration of 290-310 g / L to the anode side; (4) opening the chlorine gas absorption device to ensure the hydrogen gas water seal level; (5) When the temperature of the cathode and anode is raised to 70 °C and the current is raised to the test current, a NaCl solution with a concentration of 290-310 g / L is added to the anode side of the electrolytic cell, and pure water is added to the cathode side; the electrolytic cell runs smoothly, the temperature of the cathode and anode is raised to the test temperature, and when the concentration of the NaOH solution at the outlet is in the range of 32-33 wt% and the concentration of the NaCl solution at the outlet is in the range of 200-210 g / L, the single-cell voltage, chlorine purity and current efficiency are determined.

[0006] Preferably, the pretreatment conditions of the test sample in step (1) are as follows: the sample is immersed in a NaOH solution with a concentration of 0.2-2 wt% for 8-16 h. The length of the sample is 240-270 mm, and the width is 200-230 mm.

[0007] Preferably, the number of electrolytic cell units in step (2) is 5. The assembly method of the chlor-alkali ion exchange membrane is as follows: the sulfonic acid layer faces the anode of the electrolytic cell, the torque wrench is set to a torque value of 6-8 N·m when tightening the bolts, and the tightening force values of the four bolts are ensured to be uniform.

[0008] Preferably, the method of filling liquid in step (3) is as follows: the cathode liquid and anode liquid sampling valves are closed, the cathode and anode gas-liquid separators below the liquid discharge valves are closed, the cathode and anode diaphragm metering pumps are opened, the frequency and stroke are adjusted to 360 Hz and 100%, respectively, a NaOH solution with a concentration of 31-33 wt% is added to the cathode side of the electrolytic cell, and a NaCl solution with a concentration of 290-310 g / L is added to the anode. When the visible liquid level appears at the upper outlet of the electrolytic cell, the cathode and anode magnetic circulation pumps are opened, and the diaphragm metering pumps are stopped when overflow appears at both sides of the cathode and anode gas-liquid separators.

[0009] Preferably, step (4) is the preparatory work before the electrolysis experiment. First, the chlorine gas absorption device is opened, and whether the operation is smooth is checked. Then, the hydrogen gas water seal level (about 50-70 cmH2O) is confirmed.

[0010] Preferably, in step (5), the test temperature is 85 °C, and the test current is 10 A-50 A.

[0011] Further preferably, the method of raising the temperature in step (5) is as follows: when the temperature of the cathode and anode is raised to more than 70 °C, the current is raised, and the rectifier cabinet raises the current to the target value at a speed of 1 A / min.

[0012] The temperature raising operation steps are as follows: open the steam switch to make the steam pressure reach 0.35-0.4 MPa (the steam pressure can also be appropriately reduced according to the site conditions); open the electrolytic cell site steam pipeline drain valve switch, and close the switch when white steam appears. After the steam hand valve at the upper part of the electrolytic cell is closed tightly, it is opened by half for later use. Open the PID regulator, and set the temperature of the cathode and anode to 85 °C to start raising the temperature.

[0013] The calculation formula of current density is as follows: (1) Wherein, J is the current density, unit is kA·m 2 ; I is the current value, unit is kA; S is the electrolytic effective area of ion exchange membrane, that is, the area in contact with the cathode mesh, unit is m 2 .

[0014] In the present test method, the effective electrolysis area of electrolytic cell is 0.01 m 2 , the current value is 0.01~0.05 kA, and the electrochemical performance of chlor-alkali ion exchange membrane under different current densities can be tested according to the requirements. While increasing the current, the anode and cathode diaphragm metering pumps are opened respectively, and it is noted that the concentration of NaCl solution added to the anode side of the electrolytic cell is still 290-310 g / L, and pure water is added to the cathode side. Set the anode metering pump stroke to 100%, the frequency to 230 Hz; the cathode metering pump stroke to 50%, the frequency to 15 Hz. After the electrolytic cell runs stably for 10 minutes, the anode and cathode liquid are sampled from the alkali liquid sampling port and the dilute brine sampling port respectively to test the concentration, and the sampling liquid speed is adjusted according to the test value. When the outlet NaOH solution concentration is in the range of 32~33wt%, and the outlet NaCl solution concentration is in the range of 200~210 g / L, set the anode metering pump stroke to 100%, the frequency to 230 Hz; the cathode metering pump stroke to 50%, the frequency to 35 Hz, and adjust the anode and cathode bath temperature to be stable at 85℃, and then measure the single cell voltage, chlorine purity and current efficiency.

[0015] Measuring single cell voltage, characterized in that the single cell voltage of the electrolytic cell is tested by a multimeter and recorded.

[0016] Measuring chlorine purity: connect the gas measuring tube to the chlorine outlet, close the chlorine absorption valve and dilute brine overflow valve, and open the chlorine sampling valve. Replace the air in the gas measuring tube with chlorine, and perform twice, then absorb the chlorine in the gas measuring tube with a 32% mass fraction sodium hydroxide solution, make the water level bottle and the gas measuring tube liquid level flat, and read the reading at the concave liquid surface of the gas measuring tube, which is the chlorine purity value.

[0017] Measuring current efficiency: after the electrolytic cell runs stably, the cathode liquid is collected at the cathode liquid overflow port by a beaker for t hours, weighed and tested for its concentration (at least twice, taking the average value), and the current efficiency is calculated according to the following formula: (2) Wherein, η is the current efficiency, unit is %; m 实际 is the actual alkali production, unit is gram (g). m 理论 The theoretical alkali production is in grams (g) ; l is the current value, in amperes (A) ; t is the electrolysis time, in hours (h), in the present test method, the catholyte liquid contact time is 3 h; k is the electrochemical equivalent, in grams per amperes hour g / (A·h), in the present test method, the value is 1.492 g / (A·h) ; n is the number of unit cells, i.e. the number of diaphragms.

[0018] The present application has the following beneficial effects: The method for testing the chlor-alkali ion exchange membrane tank voltage, chlorine purity and current efficiency is simple and convenient, and can quickly and accurately detect the electrochemical performance of the chlor-alkali ion exchange membrane, greatly saving the test time and test cost. DETAILED DESCRIPTION

[0019] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments consistent with the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and "comprising", when used in this specification, specify the presence of stated features, integers, steps, or components, but do not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof.

[0020] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be further described below through embodiments, but is not limited to the present embodiments.

[0021] Embodiment 1 The chlor-alkali ion exchange membrane is cut into 5 rectangular samples, each with a length of 250 mm and a width of 220 mm. The ion exchange membrane is soaked in a 2% by mass sodium hydroxide solution at room temperature for 8 h. The ion exchange membrane is installed in a tank (the number of unit cells is 5), and the effective electrolysis area of the electrolysis tank is 0.01 m 2 The anode and cathode chambers are filled with liquid (the anode side is filled with a 300 g / L NaCl solution, and the cathode side is filled with a 32% NaOH solution), and the circulation is started. When the temperature is raised to 70 ℃, the rectifier cabinet is used to increase the current to 10 A at a speed of 1 A / min, and the temperature is continuously raised to 85 ℃. At the same time, the anode and cathode diaphragm pumps are turned on, and the concentration of the NaCl solution added to the anode side is still 300 g / L, and pure water is added to the cathode side.

[0022] The anode metering pump stroke was set to 100%, and the frequency was 230 Hz; the cathode metering pump stroke was set to 50%, and the frequency was 15 Hz. When the cathode and anode tank temperatures were both stable at 85°C, the outlet NaOH solution concentration was measured to be 32.15%, and the outlet NaCl solution concentration was measured to be 205 g / L. At this time, the cell voltages of the five membranes were recorded to be 2.516 V, 2.513 V, 2.512 V, 2.517 V, and 2.516 V, respectively, and the chlorine purity was measured to be 94.55%. After the electrolysis cell was operated stably, the cathode liquid was collected at the overflow port for 3 hours, weighed, and its concentration was measured (two measurements were taken, and the average value was taken), and the current efficiency was calculated to be 94.32%.

[0023] Example 2 With reference to Example 1, the other conditions were unchanged, and the current was increased to 20 A at a speed of 1 A / min. When the cathode and anode tank temperatures were both stable at 85°C, the outlet NaOH solution concentration was measured to be 32.27%, and the outlet NaCl solution concentration was measured to be 203 g / L. At this time, the cell voltages of the five membranes were recorded to be 2.653 V, 2.655 V, 2.651 V, 2.651 V, and 2.653 V, respectively, the chlorine purity was measured to be 95.60%, and the current efficiency was calculated to be 96.35%.

[0024] Example 3 With reference to Example 1, the other conditions were unchanged, and the current was increased to 30 A at a speed of 1 A / min. When the cathode and anode tank temperatures were both stable at 85°C, the outlet NaOH solution concentration was measured to be 32.55%, and the outlet NaCl solution concentration was measured to be 210 g / L. At this time, the cell voltages of the five membranes were recorded to be 2.770 V, 2.775 V, 2.779 V, 2.775 V, and 2.773 V, respectively, the chlorine purity was measured to be 96.80%, and the current efficiency was calculated to be 96.26%.

[0025] Example 4 With reference to Example 1, the other conditions were unchanged, and the current was increased to 40 A at a speed of 1 A / min. When the cathode and anode tank temperatures were both stable at 85°C, the outlet NaOH solution concentration was measured to be 32.61%, and the outlet NaCl solution concentration was measured to be 209 g / L. At this time, the cell voltages of the five membranes were recorded to be 2.878 V, 2.876 V, 2.876 V, 2.879 V, and 2.879 V, respectively, the chlorine purity was measured to be 97.50%, and the current efficiency was calculated to be 96.21%.

[0026] Example 5 Referring to Example 1, other conditions remain unchanged, the rectifier cabinet is raised to 50 A at a speed of 1 A / min. When the cathode and anode tank temperatures are both stable at 85℃, the concentration of the outlet NaOH solution is 32.55%, and the concentration of the outlet NaCl solution is 200 g / L. At this time, the cell voltage of the five membranes is recorded as 2.979 V, 2.973 V, 2.977 V, 2.975 V, and 2.976 V, respectively, the chlorine gas purity is 98.45%, and the current efficiency is 96.33%.

[0027] Comparative Example 1 The chlor-alkali ion exchange membrane was cut into five rectangular samples, each with a length of 250 mm and a width of 220 mm. The ion exchange membrane was soaked in a 2% by mass sodium hydroxide solution at room temperature for 8 hours. The ion exchange membrane was installed in the electrolysis tank (5 units per cell), and the effective electrolysis area of the electrolysis tank was 0.01 m 2 When the temperature was raised to 70℃, the current of the rectifier cabinet was directly adjusted to 10 A, and the temperature was continued to be raised to 85℃. The anode and cathode diaphragm metering pumps were opened, and the anode metering pump was set to 100% stroke and 230 Hz frequency, and the cathode metering pump was set to 50% stroke and 15 Hz frequency. Note that the concentration of the NaCl solution added to the anode side was still 300 g / L, and the cathode side was changed to pure water.

[0028] When the cathode and anode tank temperatures were maintained at 84~89℃, the outlet NaOH solution concentration was measured to be 32.35% after 1 hour of electrolysis, and the outlet NaCl solution concentration was measured to be 207 g / L. At this time, the cell voltage of the five membranes was recorded as 2.517 V, 2.523 V, 2.504 V, 2.512 V, and 2.506 V, respectively, the chlorine gas purity was 94.30%, and the current efficiency was 94.05% after the electrolysis tank was run smoothly for 3 hours, the cathode liquid was collected at the overflow port of the cathode liquid, weighed, tested for concentration (two times, average value), and calculated.

[0029] Comparative Example 2 Referring to Comparative Example 1, other conditions remain unchanged, the current of the rectifier cabinet was directly adjusted to 10 A, and after running for one hour, it was directly adjusted to 20 A. When the cathode and anode tank temperatures were maintained at 84~89℃, the outlet NaOH solution concentration was measured to be 31.85% after 1 hour of electrolysis, and the outlet NaCl solution concentration was measured to be 193 g / L. At this time, the cell voltage of the five membranes was recorded as 2.662 V, 2.653 V, 2.647 V, 2.657 V, and 2.679 V, respectively, the chlorine gas purity was 95.35%, and the current efficiency was 94.29%.

[0030] Comparative Example 3 Referring to Comparative Example 1, other conditions remain unchanged, the current of the rectifier cabinet is directly adjusted to 10 A, after running for one hour, it is directly adjusted to 20 A, and after running for one hour, the direct adjustment current is adjusted to 30 A. When the cathode and anode tank temperatures are maintained at 84-89 ℃, the outlet NaOH solution concentration value is measured to be 32.45% after electrolysis for 1 hour, and the outlet NaCl solution concentration value is 213 g / L. At this time, the membrane tank voltages of the 5 pieces of membrane are recorded as 2.762 V, 2.773 V, 2.787 V, 2.767 V, and 2.779 V, respectively, the chlorine gas purity value is tested to be 96.45%, and the current efficiency is calculated to be 95.33%.

[0031] Comparative Example 4 Referring to Comparative Example 1, other conditions remain unchanged, the current of the rectifier cabinet is directly adjusted to 10 A, and then the current is adjusted to 40 A by increasing 10 A every hour. When the cathode and anode tank temperatures are maintained at 84-89 ℃, the outlet NaOH solution concentration value is measured to be 31.94% after electrolysis for 1 hour, and the outlet NaCl solution concentration value is 206 g / L. At this time, the membrane tank voltages of the 5 pieces of membrane are recorded as 2.862 V, 2.873 V, 2.857 V, 2.864 V, and 2.875 V, respectively, the chlorine gas purity value is tested to be 97.45%, and the current efficiency is calculated to be 95.25%.

[0032] Comparative Example 5 Referring to Comparative Example 1, other conditions remain unchanged, the current of the rectifier cabinet is directly adjusted to 10 A, and then the current is adjusted to 50 A by increasing 10 A every hour. When the cathode and anode tank temperatures are maintained at 84-89 ℃, the outlet NaOH solution concentration value is measured to be 32.07% after electrolysis for 1 hour, and the outlet NaCl solution concentration value is 196 g / L. At this time, the membrane tank voltages of the 5 pieces of membrane are recorded as 2.968 V, 2.974 V, 2.983 V, 2.962 V, and 2.965 V, respectively, the chlorine gas purity value is tested to be 98.55%, and the current efficiency is calculated to be 95.47%.

[0033] The test results of the examples and the comparative examples are shown in the following table; the chlor-alkali ion membrane electrolysis test method of the present application is obviously more efficient than the traditional electrolysis test method, and because the test time is short, the amount of NaCl solution, pure water and electric energy consumption into the tank is less. Compared with the traditional electrolysis test method, the test result recording condition of the present method is that the tank temperature is stable at 85℃, the outlet NaOH solution and NaCl solution concentration is stable at 32~33%, 200~210g / L, while the traditional electrolysis test method records the test result condition as the tank temperature is maintained at 84~89℃, the outlet NaOH solution and NaCl solution concentration is maintained at 32±0.5%, 190~220g / L, the conditions required by the present method are more accurate, so the data fluctuation is small and more accurate.

[0034] Table 1 Chlor-alkali ion membrane electrochemical performance test results

[0035] In summary, the chlor-alkali ion membrane experimental electrolysis test method of the present application has the advantages of convenient operation, low energy consumption, good repeatability, high test efficiency, accurate test results and the like, and has obvious advantages compared with the traditional electrolysis test method.

[0036] The above is only a preferred embodiment of the present application, and is not intended to limit the present application in other forms. Any person skilled in the art can modify or change the above disclosed technical content to obtain equivalent embodiments. However, any simple modification, equivalent change and modification made on the basis of the technical essence of the present application to the above embodiments, which does not deviate from the technical solution content of the present application, still belongs to the protection scope of the present application technical solution.

Claims

1. A method for testing chlor-alkali ion-exchange membrane electrolysis, characterized in that, Includes the following steps: (1) The chlor-alkali ion membrane to be tested is pretreated by soaking it in NaOH solution; (2) Load the ion exchange membrane into the electrolytic cell unit; (3) Filling the cathode and anode systems with liquid: Add a NaOH solution with a concentration of 31-33wt% to the cathode side of the electrolytic cell and a NaCl solution with a concentration of 290-310 g / L to the anode side; (4) Turn on the chlorine absorption device and ensure the hydrogen water seal level; (5) Raise the cathode and anode temperatures to 70 °C and the current to the test current. At the same time, add a NaCl solution with a concentration of 290-310 g / L to the anode side of the electrolytic cell and add pure water to the cathode side. The electrolytic cell runs smoothly. When the cathode and anode temperatures rise to the test temperature, and the outlet NaOH solution concentration is in the range of 32-33 wt% and the outlet NaCl solution concentration is in the range of 200-210 g / L, measure the cell voltage, chlorine purity and current efficiency.

2. The chlor-alkali ion-exchange membrane electrolysis test method according to claim 1, characterized in that, The pretreatment conditions for the test samples in step (1) are: soaking in a 0.2-2 wt% NaOH solution for 8-16 h.

3. The chlor-alkali ion-exchange membrane electrolysis test method according to claim 1, characterized in that, In step (1), the length of the test sample is 240-270 mm and the width is 200-230 mm.

4. The chlor-alkali ion-exchange membrane electrolysis test method according to claim 1, characterized in that, In step (2), there are 5 electrolytic cell units.

5. The chlor-alkali ion-exchange membrane electrolysis test method according to claim 1, characterized in that, In step (5), the test temperature is 85 ℃ and the test current is 10 A-50 A.

6. The chlor-alkali ion-exchange membrane electrolysis test method according to claim 1, characterized in that, The heating method in step (5) is as follows: when the temperature of both the cathode and anode tanks rises to above 70 ℃, the current is increased, and the rectifier cabinet increases the current to the target value at a rate of 1 A / min.

7. The chlor-alkali ion-exchange membrane electrolysis test method according to claim 1, characterized in that, The method for determining the current efficiency in step (5) is as follows: After the electrolytic cell has been running smoothly, the cathode liquid is connected for t hours, weighed, and its concentration is tested. The current efficiency is calculated using formula (2): （2） Where η is the current efficiency, in percentage terms. m 实际 The actual alkali production is expressed in grams (g). m 理论 The theoretical alkali yield is expressed in grams (g). l represents the current value, measured in amperes (A). t represents the electrolysis time, in hours (h). k is the electrochemical equivalent, expressed in grams per ampere-hour (g / (A·h)), and its value is 1.492 g / (A·h). n represents the number of unit slots, i.e., the number of diaphragms.

8. The current efficiency measurement method according to claim 7, characterized in that, The contact time t for the cathode liquid is 3 hours.

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