Accurate measurement method for current efficiency of electrolytic cell and actual hydrogen production calibration method

Abstract

The invention relates to the technical field of alkaline water hydrogen production electrolytic cells, in particular to an electrolytic cell current efficiency accurate measurement method and an actual hydrogen production capacity calibration method.The electrolytic cell current efficiency accurate measurement method comprises the steps that a gas drainage device is arranged, and hydrogen produced by an electrolytic cell is introduced into a water tank of the gas drainage device for a hydrogen drainage experiment; the method comprises the following steps: obtaining a drainage volume through a hydrogen drainage experiment to obtain a corresponding volume of hydrogen introduced into a gas drainage device, and correcting the volume of hydrogen introduced into the gas drainage device into an actual hydrogen production amount in a standard pressure and temperature state by measuring pressure data and temperature data of hydrogen in the gas drainage device. And the ratio of the actual hydrogen production to the theoretical hydrogen production is calculated, and the current efficiency of the electrolytic cell under the set current density working condition is obtained. The current efficiency of the electrolytic cell can be accurately measured, and the actual hydrogen production of the electrolytic cell can be accurately calibrated.

Description

Technical Field

[0001] The present invention relates to the technical field of alkaline water electrolysis cells for hydrogen production, and particularly relates to a method for accurately measuring the current efficiency of an electrolysis cell and a method for calibrating the actual hydrogen production amount. Background Art

[0002] The current efficiency of an alkaline water electrolysis cell for hydrogen production is the ratio of the actual hydrogen production amount to the theoretical hydrogen production amount, usually expressed as a percentage, which reflects the effective utilization rate of current during the electrolysis process. The influencing factors may include electrolyte composition, temperature, current density, electrode material, etc.

[0003] The alkaline water electrolysis cell circulates direct current in water, decomposes the molecules in water into oxygen and hydrogen, and the current passes through a series of electrolysis compartments. Each electrolytic cell consists of two electrodes and a diaphragm for separating gases. To improve ionic conductivity, its electrolyte uses potassium hydroxide or sodium hydroxide solution. Since the electrolyte flow channel and the double-electrode electrolysis system share the power supply system, parallel shunting occurs, and the current directly passes through the electrolyte flow channel to generate a closed circuit, consuming electrical energy in the form of heat generation. Therefore, during actual operation, due to the existence of scattered current, its actual hydrogen production amount is lower than the theoretical hydrogen production amount.

[0004] Hydrogen is the gas with the smallest molecular weight and the lightest density in nature. In addition, its properties of easy leakage and easy diffusion lead to being affected by various factors during the measurement of hydrogen flow rate with a mass flowmeter, especially inaccurate measurement often occurs under low hydrogen flow rate conditions.

[0005] In addition, due to incomplete gas-liquid separation, hydrogen often carries part of water vapor, and after pressure maintaining and nitrogen filling, incomplete removal of nitrogen, etc., will further increase the measurement error of the hydrogen mass flowmeter. Summary of the Invention

[0006] In order to solve the above problems, the present invention proposes a method for accurately measuring the current efficiency of an electrolysis cell and a method for calibrating the actual hydrogen production amount, aiming to accurately measure the current efficiency of the electrolysis cell and accurately calibrate the actual hydrogen production amount of the electrolysis cell. The specific technical solutions are as follows: A method for accurately measuring the current efficiency of an electrolysis cell, which sets up a gas drainage device, passes the hydrogen generated by the electrolysis cell into the water tank of the gas drainage device for a hydrogen drainage experiment, obtains the drainage volume through the hydrogen drainage experiment, gets the corresponding hydrogen gas volume introduced into the gas drainage device, and measures the pressure data and temperature data of the hydrogen gas in the gas drainage device, corrects the hydrogen gas volume introduced into the gas drainage device to the actual hydrogen production amount under standard pressure and temperature conditions, and calculates the ratio of the actual hydrogen production amount to the theoretical hydrogen production amount to obtain the current efficiency of the electrolysis cell under the set current density condition.

[0007] Among them, the gas drainage device includes a closed water tank, a hydrogen inlet N1, a drainage outlet N2, a high-level liquid level observation window N3, a low-level liquid level observation window N4, a pressure gauge N5, and a thermometer N6, which are respectively arranged on the closed water tank.

[0008] Specifically, the method for accurately measuring the current efficiency of the electrolytic cell includes the following steps: (1) Electrolytic cell setting: The electrolytic cell operates, and the current density of the electrolytic cell is adjusted to the set current density, and the electrolytic cell operates stably at the set current density for a period of time; (2) Drainage: The hydrogen gas generated by the electrolytic cell is led out from the hydrogen outlet of the electrolytic cell and connected to the hydrogen inlet N1 of the gas drainage device for drainage and stable operation for a period of time to maintain the liquid level balance, and to form a stable air pressure inside the gas drainage device, and the temperatures at various places tend to be balanced and consistent; (3) Measurement: Start timing, record the mass of the water discharged from the drainage outlet N2 within the set drainage time, and obtain the data of temperature T and pressure P; (4) Data processing: Calculate the theoretical hydrogen production Q1, Q1 = I×n / 2390; Calculate the actual hydrogen production Q2, Q2 = (1 / t)×(m / ρ)×(273 / T)×(P / 101.325); Calculate the current efficiency η, η = Q2 / Q1; Among them, I is the current applied to the electrolytic cell by the power supply, and the unit is A; Among them, n is the number of compartments of the electrolytic cell; Among them, t is the set drainage time, and the unit is hour; Among them, m is the mass of the discharged water, and the unit is kg; Among them, ρ is the density of water at this temperature, and the unit is kg / m3; Among them, T is the temperature of hydrogen gas in the gas drainage device, and the unit is K; Among them, P is the pressure of hydrogen gas in the gas drainage device, and the unit is kPa.

[0009] Preferably, in the electrolytic cell setting in step (1), the electrolytic cell operates stably at the set current density for not less than 15 minutes.

[0010] Preferably, in the measurement in step (3), the set drainage time is half an hour.

[0011] Preferably, the operating temperature range of the alkaline water electrolysis in the electrolytic cell is 85 to 95 degrees Celsius, the concentration range of the potassium hydroxide electrolyte in the electrolytic cell is 25-35% by weight percentage, and the current density range of the electrolytic cell is 900-9000 A / m2.

[0012] Obtain the data of temperature T and pressure P through a pressure gauge and a thermometer sealed and installed on the drainage device. The pressure range of the pressure gauge is 1 - 16 Bar, and the temperature measurement range of the thermometer is 0 - 100 °C.

[0013] The above method for accurately measuring the current efficiency of an electrolytic cell using a gas drainage device can be further applied to the accurate calibration of the actual hydrogen production of the electrolytic cell.

[0014] A method for effectively calibrating the actual hydrogen production of an electrolytic cell includes the following steps: (1) Obtain the current, electrolysis area, current density, and theoretical hydrogen production of the target electrolytic cell; (2) Through the hydrogen drainage experiment steps and pressure and temperature numerical correction, obtain the corresponding relationship between the electrolysis efficiency and the current density under different current density conditions; (3) Based on the corresponding relationship between the electrolysis efficiency and the current density, correspondingly obtain the corresponding relationship table between the dispersed current ratio and the current density, and establish a functional relationship between the dispersed current ratio and the current density; (4) According to the functional relationship, calibrate the current efficiency and actual hydrogen production of the large electrolytic cell.

[0015] The method for obtaining the theoretical hydrogen production is obtained through the Faraday's law calculation formula based on the applied current and the number of cells of the target electrolytic cell; the corresponding relationship between the electrolysis efficiency and the current density in the hydrogen drainage experiment is the relationship table or relationship graph data of the electrolysis efficiency and the current density determined based on the corresponding relationship between the electrolysis efficiency and the current density after the electrolytic cell operates stably at each current density.

[0016] In steps (2) to (3) of the present invention, the hydrogen generated by the electrolytic cell is introduced into the gas drainage device for a drainage experiment to obtain the original data of multiple current densities x and the original data of the corresponding current efficiency η; then, based on the original data of the multiple current densities x and the corresponding current efficiency η, obtain the corresponding dispersed current ratio y = 1 - η, and then obtain the functional relationship between the dispersed current ratio y and the current density x through data fitting.

[0017] The functional relationship between the dispersed current ratio y and the current density x of the present invention is an exponential function relationship, and its exponential function formula is ; where a, b, and c are regression coefficients, which are obtained by the nonlinear least squares method.

[0018] Through the obtained exponential function formula , and according to the actual current density x of the target electrolytic cell, substitute it into the exponential function relationship to obtain the dispersion current ratio y of the target electrolytic cell, and then determine the actual hydrogen production Q2 of the target electrolytic cell based on the theoretical hydrogen production Q1 of the target electrolytic cell: Q2 = Q1 × (1 - y).

[0019] The beneficial effects of the present invention are as follows: By accurately measuring the actual hydrogen production of the electrolytic cell at each current density through the gas drainage experiment method, the functional relationship between the current density and the current efficiency is obtained; and based on this functional relationship, the theoretical hydrogen production of the target electrolytic cell under each operating load is calibrated and revised, thus making up for the problem of low measurement accuracy of the hydrogen flowmeter at low flow rates and further improving the calculation accuracy of the actual hydrogen production. Thereby, the accurate measurement of the current efficiency of the electrolytic cell and the accurate calibration of the actual hydrogen production of the electrolytic cell are realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic diagram of the relationship between the dispersion current ratio and the current density obtained through the hydrogen drainage experiment in the present invention; Figure 2 is a schematic structural diagram of the gas drainage device. DETAILED DESCRIPTION OF THE INVENTION

[0021] The following further describes the specific embodiments of the present invention in conjunction with the drawings and embodiments. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and cannot be used to limit the protection scope of the present invention. Embodiment 1

[0022] As Figures 1 to 2 shown is an embodiment of a method for accurately measuring the current efficiency of an electrolytic cell according to the present invention. A gas drainage device is set up, and the hydrogen generated by the electrolytic cell is introduced into the water tank of the gas drainage device for a hydrogen drainage experiment. The drainage volume is obtained through the hydrogen drainage experiment to obtain the corresponding hydrogen volume introduced into the gas drainage device, and by measuring the pressure data and temperature data of the hydrogen in the gas drainage device, the hydrogen volume introduced into the gas drainage device is corrected to the actual hydrogen production under standard pressure and temperature conditions, and the ratio of the actual hydrogen production to the theoretical hydrogen production is calculated to obtain the current efficiency of the electrolytic cell under the set current density condition.

[0023] Among them, the gas drainage device includes a closed water tank, a hydrogen inlet N1, a drainage port N2, a high-level liquid level observation window N3, a low-level liquid level observation window N4, a pressure gauge N5, and a thermometer N6 respectively arranged on the closed water tank.

[0024] Specifically, the method for accurately measuring the current efficiency of the electrolytic cell includes the following steps: (1)Electrolyzer setup: The electrolyzer operates, and the current density of the electrolyzer is adjusted to the set current density. The electrolyzer operates stably at the set current density for a period of time; (2)Drainage: The hydrogen gas generated by the electrolyzer is led out from the hydrogen outlet of the electrolyzer and connected to the hydrogen inlet N1 of the gas drainage device for drainage and stable operation for a period of time to maintain liquid level balance, and to form a stable air pressure inside the gas drainage device, and the temperatures at various places tend to be evenly consistent; (3)Measurement: Start timing, record the mass of the water discharged from the drain outlet N2 within the set drainage time, and obtain the data of temperature T and pressure P; (4)Data processing: Calculate the theoretical hydrogen production Q1, Q1 = I × n / 2390; Calculate the actual hydrogen production Q2, Q2 = (1 / t) × (m / ρ) × (273 / T) × (P / 101.325); Calculate the current efficiency η, η = Q2 / Q1; Wherein, I is the current applied to the electrolyzer by the power supply, with the unit of A; Wherein, n is the number of compartments of the electrolyzer; Wherein, t is the set drainage time, with the unit of hour; Wherein, m is the mass of the discharged water, with the unit of kg; Wherein, ρ is the density of water at this temperature, with the unit of kg / m3; Wherein, T is the temperature of hydrogen gas inside the gas drainage device, with the unit of K; Wherein, P is the pressure of hydrogen gas inside the gas drainage device, with the unit of kPa.

[0025] Preferably, the operating temperature range of the alkaline water electrolysis in the electrolyzer is 85 to 95 degrees Celsius, the concentration range of the potassium hydroxide electrolyte solution in the electrolyzer is 25 - 35% by weight percentage, and the current density range of the electrolyzer is 900 - 9000 A / m2.

[0026] The data of temperature T and pressure P are obtained through a pressure gauge and a thermometer sealed and installed on the drainage device. The pressure range of the pressure gauge is 1 - 16 Bar, and the temperature measurement range of the thermometer is 0 - 100 °C.

[0027] The above method for accurately measuring the current efficiency of an electrolyzer using a gas drainage device can be further applied to the accurate calibration of the actual hydrogen production of the electrolyzer. Example 2

[0028] A method for effectively calibrating the actual hydrogen production of an electrolyzer includes the following steps: (1) Obtain the current, electrolysis area, current density, and theoretical hydrogen production of the target electrolytic cell; (2) Through the hydrogen drainage experiment steps and the correction of pressure and temperature values, obtain the corresponding relationship between the electrolysis efficiency and the current density under different current density conditions; (3) Based on the corresponding relationship between the electrolysis efficiency and the current density, correspondingly obtain the corresponding relationship table between the dispersed current ratio and the current density, and establish the functional relationship between the dispersed current ratio and the current density; (4) According to the functional relationship, calibrate the current efficiency and the actual hydrogen production of the large electrolytic cell.

[0029] The method for obtaining the theoretical hydrogen production is obtained through the Faraday's law calculation formula based on the applied current and the number of small chambers of the target electrolytic cell; the corresponding relationship between the electrolysis efficiency and the current density in the hydrogen drainage experiment is the relationship table or relationship graph data of the electrolysis efficiency and the current density determined based on the corresponding relationship between the electrolysis efficiency and the current density after the electrolytic cell operates stably at each current density.

[0030] In steps (2) to (3) of this embodiment, the hydrogen generated by the electrolytic cell is introduced into the gas drainage device for the drainage experiment to obtain the original data of multiple current densities x and the original data of the corresponding current efficiency η; then based on the original data of the multiple current densities x and the corresponding current efficiency η, obtain the corresponding dispersed current ratio y = 1 - η, and then obtain the functional relationship between the dispersed current ratio y and the current density x through data fitting.

[0031] The functional relationship between the dispersed current ratio y and the current density x in this embodiment is an exponential function relationship, and its exponential function formula is ; where a, b, and c are regression coefficients, which are obtained by the nonlinear least squares method.

[0032] Through the obtained exponential function formula , and according to the actual current density x of the target electrolytic cell, substitute it into the exponential function formula to obtain the dispersed current ratio y of the target electrolytic cell, and then according to the theoretical hydrogen production Q1 of the target electrolytic cell, determine the actual hydrogen production Q2 = Q1 × (1 - y) of the target electrolytic cell. Example 3

[0033] Table 1 is the relationship table between the dispersed current ratio and the current density of a certain electrolytic cell obtained by the drainage experiment method. Multiple current density data and the original data of the corresponding dispersed current ratio are obtained through the gas drainage experiment.

[0034]

[0035] Based on the original data of multiple current density data and the corresponding discrete current ratios in Table 1, necessary data processing can be performed to determine the functional relationship between the discrete current ratio and the current density, and the discrete current ratio of the current current density can be calibrated based on the functional relationship to determine the target discrete current ratio corresponding to the current current density.

[0036] Figure 1 is a relationship graph of the discrete current ratio and the current density drawn using the data in the relationship table of the discrete current ratio and the current density in Table 1. In the graph, the horizontal axis represents the current density x (A / m 2 ), the vertical axis represents the discrete current ratio. This curve is composed of multiple current density data and the corresponding discrete current ratio data. Data processing can be performed based on multiple said current density data and multiple said discrete current ratio data to obtain the corresponding relationship between the electrolysis efficiency and the current density, that is, to obtain the fitting curve of this corresponding relationship. The fitting curve of this corresponding relationship can also be discretized and presented in the form of a table data as shown in Table 1 to facilitate the calculation of the actual hydrogen production after correction.

[0037] From Figure 1 it can be seen that in the current density range of 900~9000 A / m 2 , the discrete current ratio and the current density show an exponential relationship: , where y is the discrete current ratio, a, b, and c are regression coefficients, and x is the current density.

[0038] Example 1, with a working current density of 3000 A / m 2 , the electrolysis efficiency η = 100% according to the national standard method, and the designed theoretical hydrogen production of a single electrolyzer (5 MW) is 1000 Nm 3 / h. Using the electrolysis efficiency calculation method proposed in the present invention, by referring to Table 1, the discrete current ratio is 0.03016. Then the actual hydrogen production after correction is 1000*(1 - 0.03016) = 969.84 Nm 3 / h.

[0039] Example 2, with a working current density of 6000 A / m 2 , the electrolysis efficiency η = 100% according to the national standard method, and the designed theoretical hydrogen production of a single electrolyzer (10 MW) is 2000 Nm 3 / h. Using the electrolysis efficiency calculation method proposed in the present invention, by referring to Table 1, the discrete current ratio is 0.01246. Then the actual hydrogen production after correction is 2000*(1 - 0.01246) = 1975.08 Nm 3 / h.

[0040] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for accurately measuring the current efficiency of an electrolytic cell, characterized in that: A gas drainage device is provided, and the hydrogen produced by the electrolyzer is passed into a water tank of the gas drainage device to carry out a hydrogen drainage experiment. The drainage volume is obtained through the hydrogen drainage experiment, and the corresponding volume of hydrogen passed into the gas drainage device is obtained. By measuring the pressure data and temperature data of the hydrogen in the gas drainage device, the volume of hydrogen passed into the gas drainage device is corrected to the actual hydrogen production under standard pressure and temperature conditions, and the ratio of the actual hydrogen production to the theoretical hydrogen production is calculated to obtain the current efficiency of the electrolyzer under the set current density working condition.

2. The method for accurately measuring the current efficiency of an electrolytic cell according to claim 1, characterized in that: The gas drainage device includes a closed water tank, a hydrogen inlet N1, a drainage port N2, a high liquid level observation window N3, a low liquid level observation window N4, a pressure gauge N5 and a thermometer N6 which are respectively arranged on the closed water tank.

3. The method for accurately measuring the current efficiency of an electrolytic cell according to claim 2, characterized in that: The steps include: (1) Electrolytic cell setting: The electrolytic cell is operated, and the current density of the electrolytic cell is adjusted to the set current density. The electrolytic cell operates stably at the set current density for a period of time; (2) Drainage: The hydrogen produced by the electrolyzer is led out from the hydrogen outlet of the electrolyzer and connected to the hydrogen inlet N1 of the gas drainage device for drainage and stable operation for a period of time to maintain liquid level balance, form a stable gas pressure inside the gas drainage device, and make the temperature at various locations tend to be balanced; (3) Measurement: Start timing, record the mass of water discharged from the drain outlet N2 within the set drainage time, and obtain the data of temperature T and pressure P; (4) Data processing: Calculate the theoretical hydrogen production Q1, Q1=I×n / 2390; Calculate the actual hydrogen production Q2, Q2 = (1 / t) × (m / ρ) × (273 / T) × (P / 101.325); Calculate the current efficiency η, η=Q2 / Q1; Where, I is the current applied to the electrolytic cell by the power supply, in A; Where n is the number of chambers in the electrolytic cell; Among them, t is the set drainage time, in hours; Where, m is the mass of discharged water, in kg; Where ρ is the density of water at that temperature, in kg / m3; Where, T is the temperature of hydrogen in the gas drainage device, in K; Where P is the pressure of hydrogen in the gas drainage device, in kPa.

4. The method for accurately measuring the current efficiency of an electrolytic cell according to claim 1, characterized in that: The alkaline water electrolysis operation temperature range of the electrolytic cell is 85 to 95 degrees Celsius, the potassium hydroxide electrolyte concentration range of the electrolytic cell is 25 to 35% by weight, and the current density range of the electrolytic cell is 900 to 9000 A / m2.

5. The method for accurately measuring the current efficiency of an electrolytic cell according to claim 3, characterized in that: The data of temperature T and pressure P are obtained by sealing the pressure gauge and thermometer installed on the drainage device. The pressure range of the pressure gauge is 1~16Bar, and the temperature measurement range of the thermometer is 0~100℃.

6. A method for effectively calibrating the actual hydrogen production of an electrolyzer, characterized in that: The steps include: (1) Obtain the current, electrolysis area, current density and theoretical hydrogen production of the target electrolyzer; (2) Through the hydrogen drainage experimental steps and pressure and temperature numerical correction, the corresponding relationship between electrolysis efficiency and current density under different current density conditions is obtained; (3) Based on the correspondence between the electrolysis efficiency and the current density, a correspondence table between the dispersion current ratio and the current density is obtained, and a functional relationship between the dispersion current ratio and the current density is established; (4) Based on the functional relationship, the current efficiency and actual hydrogen production of the large electrolyzer are calibrated.

7. A method for effectively calibrating the actual hydrogen production of an electrolyzer according to claim 6, characterized in that: The method for obtaining the theoretical hydrogen production is based on the applied current of the target electrolytic cell and the number of chambers, and is obtained by calculating the Faraday's law; the correspondence between the electrolysis efficiency and the current density in the hydrogen drainage experiment is a relationship table or relationship diagram data between the electrolysis efficiency and the current density determined based on the correspondence between the electrolysis efficiency and the current density after the electrolytic cell is stably operated at various current densities.

8. A method for effectively calibrating the actual hydrogen production of an electrolyzer according to claim 6, characterized in that: In the steps (2) to (3), the hydrogen generated by the electrolyzer is passed into a gas drainage device to perform a drainage experiment, and a plurality of original data of current density x and the corresponding original data of current efficiency η are obtained; then, based on the plurality of original data of current density x and the corresponding original data of current efficiency η, the corresponding dispersion current ratio y=1-η is obtained, and then the functional relationship between the dispersion current ratio y and the current density x is obtained by data fitting.

9. A method for effectively calibrating the actual hydrogen production of an electrolyzer according to claim 8, characterized in that: The functional relationship between the dispersion current ratio y and the current density x is an exponential function relationship, and the exponential function relationship is: ; Where a, b, c are regression coefficients, which are obtained by nonlinear least squares method.

10. A method for effectively calibrating the actual hydrogen production of an electrolyzer according to claim 9, characterized in that: The exponential function relationship obtained by , and according to the actual current density x of the target electrolyzer, substitute it into the exponential function relationship to obtain the dispersed current ratio y of the target electrolyzer, and then according to the theoretical hydrogen production Q1 of the target electrolyzer, determine the actual hydrogen production Q2 = Q1 × (1-y) of the target electrolyzer.

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