Method and system for calculating current efficiency based on water consumption principle

Abstract

The invention relates to a method and a system for calculating current efficiency based on a water consumption principle, and relates to the technical field of electric hydrogen production. The method comprises the following steps: S1, calculating the total water consumption of the hydrogen production device; s2, the current efficiency of the electrolytic cell is calculated based on the total water consumption of the hydrogen production device, and in the formula # imgabs0, mw is the total water consumption of the hydrogen production device, I is the current passing through the electrolytic cell, N is the number of electrolysis cells of the electrolytic cell, t is the reaction time, eta is the current efficiency of the electrolytic cell, F is the Faraday constant, # imgabs1 # is the absolute humidity of hydrogen, and # imgabs2 # is the absolute humidity of oxygen. According to the method, the current efficiency is obtained by measuring the water consumption of a hydrogen production system within a period of time through electrolysis gas production according to the relation between the water consumption and the hydrogen yield in the process of producing hydrogen through water electrolysis and then converting through a series of formulas.

Description

Technical Field

[0001] The present application relates to the technical field of electric hydrogen production, and in particular to a method and system for calculating current efficiency based on the water consumption principle. Background Art

[0002] In today's context of energy transformation and environmental protection, the development and utilization of clean energy has become a global focus. Among them, hydrogen production by water electrolysis, as an efficient and clean method of hydrogen production, has received widespread attention because it can utilize renewable energy for production and its products are pure and pollution-free.

[0003] For the water electrolysis hydrogen production system, current efficiency is an important indicator that can reflect the performance of the hydrogen production system to a certain extent. At present, the current efficiency is mainly obtained by measuring the actual hydrogen production and then calculating it. In order to obtain the actual hydrogen production, it is necessary to use actual testing methods with the help of measuring equipment or instruments. The commonly used testing methods currently include the volumetric method and the flowmeter method. The volumetric method sets a gas storage tank at the gas outlet, and after a period of inflation and deflation, records the temperature and pressure changes before and after, and then converts the gas state equation to obtain the actual hydrogen production; while the flowmeter method is to install a hydrogen flowmeter on the hydrogen output pipeline, and calculate the actual hydrogen production by measuring the cumulative flow before and after a period of testing time. The above two methods each have limitations and shortcomings. The measurement accuracy of the volumetric method is easily affected by the manufacturing accuracy of the container, measurement errors, and temperature and pressure changes, and the measurement range is limited. For large-scale hydrogen production, very large containers are required for measurement, which is not realistic in practical applications. However, the cost of flow meter is relatively high, and some high-precision hydrogen sensors and flow metering equipment are expensive. For large-scale water electrolysis hydrogen production projects, equipment procurement and maintenance costs have become a significant economic burden. Summary of the invention

[0004] The purpose of this application is to provide a method and system for calculating current efficiency based on the water consumption principle. The method utilizes the relationship between water consumption and hydrogen production during the electrolysis of water to produce hydrogen. The method measures the water consumption of the hydrogen production system during electrolysis and gas production over a period of time, and then converts it through a series of formulas to obtain the current efficiency.

[0005] In order to achieve the above object, in a first aspect, the present invention provides a method for calculating current efficiency based on the water consumption principle, the method comprising:

[0006] S1: Calculate the total water consumption of the hydrogen production unit;

[0007] S2: Based on the total water consumption of the hydrogen production device, the current efficiency of the electrolyzer is calculated as follows:

[0008]

[0009] Where M w is the total water consumption of the hydrogen production device, I is the current passing through the electrolyzer, N is the number of electrolytic chambers in the electrolyzer, t is the reaction time, η is the current efficiency of the electrolyzer, F is the Faraday constant, is the absolute humidity of hydrogen, is the absolute humidity of oxygen.

[0010] In an optional embodiment, S1 includes:

[0011] The total water consumption of the hydrogen production device is calculated based on the electrolysis water consumption and the amount of water carried away by the gas. The calculation formula is as follows:

[0012] m w =m we +m wg

[0013] In the formula, m we is the electrolysis water consumption; m wg The amount of water carried away by the gas.

[0014] In an optional embodiment, S1 includes:

[0015] Based on the amount of water consumed in the electrolysis process, the electrolysis water consumption is calculated using the following formula:

[0016]

[0017] In the formula, m we is the electrolysis water consumption, The amount of water consumed in the electrolysis process, is the molar mass of water, I is the current passing through the electrolytic cell, N is the number of electrolytic cells in the electrolytic cell, t is the reaction time, η is the current efficiency of the electrolytic cell, and F is the Faraday constant.

[0018] In an optional embodiment, S1 includes:

[0019] Based on the absolute humidity, the amount of water carried away by the gas is calculated using the following formula:

[0020]

[0021] In the formula, m wg is the amount of water carried away by the gas, is the total volume of hydrogen generated during the electrolysis process; The total volume of oxygen generated by the electrolysis process; is the absolute humidity of hydrogen; is the absolute humidity of oxygen.

[0022] In an optional embodiment, in S1, the calculation formula of absolute humidity is as follows:

[0023]

[0024] Where AH is absolute humidity; T a is the current temperature of the gas, e t is the actual water vapor pressure.

[0025] In an optional embodiment, S1 includes:

[0026] The total water consumption of the hydrogen production device is obtained by the liquid level difference method, and the calculation formula is as follows:

[0027] m w =(V 11 ×ρ1-V 12 ×ρ2)+(V 21 ×ρ1-V 22 ×ρ2)

[0028] Where V 11 is the volume of alkali solution in the hydrogen side gas-liquid separator or buffer tank at the beginning of the test; ρ1 is the density of alkali solution in the system measured at the beginning of the test; V 12 is the volume of alkali solution in the hydrogen side gas-liquid separator or buffer tank at the end of the test; ρ2 is the density of alkali solution in the system measured at the end of the test; V 21 V is the volume of alkali solution in the oxygen side gas-liquid separator or buffer tank at the beginning of the test; 22 It is the volume of alkaline solution in the oxygen side gas-liquid separator / buffer tank at the end of the test.

[0029] In an optional embodiment, S1 includes:

[0030] The total water consumption of the hydrogen production device is obtained by the flow meter method, and the calculation formula is as follows:

[0031]

[0032] In the formula, Q e Q is the flow meter reading at the end of water replenishment; s It is the flow meter reading at the beginning of water replenishment; is the density of pure water.

[0033] In a second aspect, the present invention provides a system for calculating current efficiency based on the water consumption principle, the system comprising:

[0034] Data acquisition and processing module, used to collect and process water flow and gas parameter data in real time;

[0035] A calculation module, used to execute the method of the aforementioned embodiment to calculate the current efficiency;

[0036] The result output and display module is used to output and display the calculated current efficiency.

[0037] In an optional embodiment, the system includes a liquid level and flow monitoring module. When the liquid level difference method is adopted, the liquid level and flow monitoring module includes a real-time liquid level monitoring device for the liquid level at the beginning and end of the test.

[0038] In an optional embodiment, when the flow meter method is adopted, the system includes a flow meter for real-time monitoring and cumulative measurement of the water flow entering the electrolytic cell.

[0039] The method and system utilize the relationship between water consumption and hydrogen production in the process of producing hydrogen by electrolysis of water. The water consumption during a period of electrolysis and gas production in the hydrogen production system is measured, and then the current efficiency is obtained by converting it through a series of formulas. The method and system have high accuracy without measurement and low equipment cost.

[0040] Other features and advantages of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0042] Figure 1 A flow chart of a method for calculating current efficiency based on the water consumption principle provided in an embodiment of the present application;

[0043] Figure 2 A block diagram of the system for calculating current efficiency based on the water consumption principle provided in an embodiment of the present application.

[0044] Icon: 1-Liquid level and flow monitoring module; 2-Gas monitoring module; 3-Data acquisition and processing module; 4-Calculation module; 5-Result output and display module. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0046] In the description of this application, it should be noted that the terms "inside", "outside", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the application is usually placed when in use, which is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0047] In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "disposed" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0048] Please refer to Figure 1 This embodiment provides a method for calculating current efficiency based on the water consumption principle (hereinafter referred to as: method), which includes the following steps:

[0049] S1: Calculate the total water consumption of the hydrogen production unit.

[0050] In the actual process of water electrolysis to produce hydrogen, the pure water consumed is not completely used to produce hydrogen. Part of the pure water is carried away by hydrogen and oxygen in the form of water vapor. The higher the gas outlet temperature and the greater the saturated vapor pressure, the greater the amount of water vapor carried away. The greater the gas outlet pressure and the greater the electrolyte concentration, the smaller the amount of water vapor carried away.

[0051] In the case of no additional water replenishment and water recovery during the electrolysis process of the hydrogen production system, the total water consumption of the hydrogen production device is calculated based on the electrolysis water consumption and the amount of water carried away by the gas. The calculation formula is as follows:

[0052] m w =m we +m wg (1)

[0053] Where:

[0054] m w is the total water consumption (g);

[0055] m we is the electrolysis water consumption (g);

[0056] m wg is the amount of water carried away by the gas (g).

[0057] The following describes how to obtain mw 、m we 、m wg Three parameters:

[0058] About getting the total water consumption m w This embodiment provides two methods for obtaining the total water consumption m according to the existing mainstream hydrogen production system process. w Methods: liquid level difference method and flow meter method.

[0059] Liquid level difference method: During the test, the water replenishment device is closed and pure water is not added to the hydrogen production device. The density of the alkali solution in the system at the beginning and end of the test is measured by a density measuring instrument such as a densitometer, and the test time and the liquid level of the hydrogen-oxygen liquid-gas separator or buffer tank (for hydrogen production systems with buffer tanks) at the beginning and end of the test are recorded. This method is only applicable when the size of the gas-liquid separator or buffer tank is known and the volume can be calculated.

[0060] The total water consumption during this period can be obtained according to the following formula m w :

[0061] m w =(V 11 ×ρ1-V 12 ×ρ2)+(V 21 ×ρ1-V 22 ×ρ2) (2)

[0062] Where:

[0063] V 11 The volume of alkali solution in the hydrogen-side gas-liquid separator or buffer tank at the beginning of the test (ml);

[0064] ρ1 is the density of the alkali solution in the system measured at the beginning of the test (g / ml)

[0065] V 12 The volume of alkali solution in the hydrogen-side gas-liquid separator or buffer tank at the end of the test (ml);

[0066] ρ2 is the density of the alkali solution in the system measured at the end of the test (g / ml)

[0067] V 21 The volume of alkali solution in the oxygen-side gas-liquid separator or buffer tank at the beginning of the test (ml);

[0068] V 22 The volume of alkali solution in the oxygen-side gas-liquid separator / buffer tank at the end of the test (ml);

[0069] Flow meter method: This method requires the installation of a water flow meter between the water replenishment device and the gas-liquid separator or buffer tank. During the test, first record the initial liquid level of the gas-liquid separator or buffer tank, then perform electrolysis for a period of time until the liquid level in the gas-liquid separator or buffer tank drops significantly before replenishing water. When the liquid level in the gas-liquid separator or buffer tank returns to the initial level, turn off the water replenishment. Read the water flow meter readings at the beginning and end of the test respectively. Multiply the difference between the two by the density of pure water to get the cumulative water replenishment during this period, that is, the total water consumption of the hydrogen production device during this period m w , as shown below:

[0070]

[0071] Where:

[0072] Q e It is the flow meter reading at the end of water replenishment (ml);

[0073] Q s is the flow meter reading at the beginning of water replenishment (ml);

[0074] is the density of pure water (g / ml).

[0075] About obtaining electrolysis water consumption m we Based on the amount of water consumed in the electrolysis process, the electrolysis water consumption is calculated. Specifically, the electrolysis water consumption m we It can be calculated by Faraday's law. According to the water electrolysis reaction formula, 2 mol of electrons need to be transferred for every 1 mol of hydrogen produced. It can be obtained that after the electrolyzer has been electrolyzing water for a period of time, the amount of water consumed and the amount of hydrogen and oxygen generated is:

[0076]

[0077] Where:

[0078] The amount of water consumed in the electrolysis process (mol);

[0079] is the amount of hydrogen produced (mol);

[0080] is the amount of oxygen generated (mol);

[0081] η is the current efficiency of the electrolytic cell (%);

[0082] I is the current passing through the electrolytic cell (A);

[0083] t is the reaction time (s);

[0084] N is the number of electrolytic cells in the electrolytic cell;

[0085] F is the Faraday constant, which is approximately 96485C / mol.

[0086] Therefore, the electrolysis water consumption m during this period can be obtained we :

[0087]

[0088] Where:

[0089] is the molar mass of water, 18 g / mol.

[0090] The amount of water m carried away by the gas wg , based on the absolute humidity, calculate the amount of water m carried away by the gas wg Specifically, if you want to know the mass of water carried away by the gas, you need to know the absolute humidity of the gas (in g / m 3 ).

[0091] Dew point and temperature sensors are installed in the pipelines before the gas-water separation devices on both sides of the hydrogen and oxygen in the hydrogen production system by water electrolysis, which can transmit gas dew point and temperature data in real time.

[0092] The absolute humidity is calculated by the following method:

[0093] 1) Calculate the actual water vapor pressure of the gas, that is, the partial pressure (partial pressure) generated by water vapor in the gas:

[0094] e t =f(T d ) (6)

[0095] Where:

[0096] e t is the actual water vapor pressure (hPa);

[0097] T d is the dew point temperature (℃);

[0098] Note: There are multiple fitting formulas for calculating the actual water vapor pressure of gas, which are not listed here.

[0099] 2) After obtaining the actual water vapor pressure of the gas, the absolute humidity is calculated by the following formula:

[0100]

[0101] Where:

[0102] AH is absolute humidity (g / m 3 );

[0103] Ta is the current temperature of the gas (°C).

[0104] Referring to Appendix A of GB32311-2015, it can be obtained that the total volumes of hydrogen and oxygen generated within the reaction time t are:

[0105]

[0106] Where:

[0107] is the total volume of hydrogen generated during the electrolysis process (m 3 );

[0108] is the total volume of oxygen generated during the electrolysis process (m 3 );

[0109] The total mass of water contained in the gas, that is, the amount of water carried away by the gas, is m wg for:

[0110]

[0111] Where:

[0112] is the absolute humidity of hydrogen (g / m 3 );

[0113] is the absolute humidity of oxygen (g / m 3 );

[0114] S2: Calculate the current efficiency of the electrolyzer based on the total water consumption of the hydrogen production device.

[0115] According to formula (1), the following relationship can be obtained:

[0116]

[0117] In the formula, except for the current efficiency η of the electrolytic cell, the other parameters are known or can be measured by corresponding instruments. Therefore, the current efficiency can be calculated by this formula.

[0118] Please refer to Figure 2 The present embodiment also provides a system for calculating current efficiency based on the water consumption principle (hereinafter referred to as: system), the system includes a liquid level and flow monitoring module 1, a gas monitoring module 2, a data acquisition and processing module 3, a calculation module 4, and a result output and display module 5.

[0119] Specifically, when the liquid level difference method is used, the liquid level and flow monitoring module 1 includes a liquid level real-time monitoring device. The liquid level real-time monitoring device is set on the separator or scrubber of the hydrogen production system, and the liquid level at the beginning and end of the test is used to obtain the total water consumption m w .

[0120] When the flow meter method is used, the liquid level and flow monitoring module 1 includes a flow meter, and a high-precision flow meter needs to be installed on the water supply pipeline. The flow meter can be an electromagnetic flow meter or an ultrasonic flow meter to monitor and cumulatively measure the water flow entering the electrolyzer in real time to obtain the total water consumption m w To ensure measurement accuracy, the flow meter should be calibrated regularly and installed in a location with smooth water flow and no eddies or disturbances.

[0121] The gas monitoring module 2 includes a temperature sensor, a pressure sensor and a dew point sensor, which are used to monitor the temperature, pressure and dew point of hydrogen and oxygen before the gas-water separation device in real time. Each sensor probe should be inserted into the gas pipeline to ensure the accuracy of the measurement.

[0122] The data acquisition and processing module 3 is used to collect water flow and gas parameter data in real time, that is, the parameter data collected by the liquid level and flow monitoring module 1 and the gas monitoring module 2, and perform pre-processing operations such as filtering and noise reduction to remove abnormal values ​​and interference signals, and time-mark and store the collected data for subsequent analysis and calculation.

[0123] The calculation module 4 is used to establish a mathematical relationship model between the current efficiency and each parameter data based on equations (1) to (12). Taking into account various errors, a correction coefficient is introduced to optimize the model. The errors mainly come from: the liquid level measurement deviation of the separator or scrubber, the measurement error of the flow meter, the measurement error of each sensor of the gas monitoring module 2, and the error caused by the simplification of the formula.

[0124] The correction coefficients are calibrated and verified through a large amount of experimental data to improve the accuracy of the calculation model.

[0125] The result output and display module 5 is used to output and display the calculated current efficiency in the form of numbers, charts, etc. It provides real-time data update and historical data query functions, which facilitates users to monitor and analyze the hydrogen production process and hydrogen production system performance.

[0126] The method and system utilize the relationship between water consumption and hydrogen production in the process of producing hydrogen by electrolysis of water. The water consumption during a period of electrolysis and gas production in the hydrogen production system is measured, and then the current efficiency is obtained by converting it through a series of formulas. The method and system have high accuracy without measurement and low equipment cost.

[0127] It should be noted that, in the absence of conflict, the features in the embodiments of this application may be combined with each other.

[0128] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for calculating current efficiency based on the water consumption principle, characterized in that: The method comprises: S1: Calculate the total water consumption of the hydrogen production unit; S2: Based on the total water consumption of the hydrogen production device, the current efficiency of the electrolyzer is calculated as follows: In the formula, m w is the total water consumption of the hydrogen production device, I is the current passing through the electrolyzer, N is the number of electrolytic chambers in the electrolyzer, t is the reaction time, η is the current efficiency of the electrolyzer, F is the Faraday constant, is the absolute humidity of hydrogen, is the absolute humidity of oxygen.

2. The method for calculating current efficiency based on the water consumption principle according to claim 1, characterized in that: S1 includes: The total water consumption of the hydrogen production device is obtained based on the electrolysis water consumption and the amount of water carried away by the gas. The calculation formula is as follows: m w =m we +m wg In the formula, m we is the electrolysis water consumption; m wg The amount of water carried away by the gas.

3. The method for calculating current efficiency based on the water consumption principle according to claim 2, characterized in that: S1 includes: Based on the amount of water consumed in the electrolysis process, the electrolysis water consumption is calculated using the following formula: In the formula, m we is the electrolysis water consumption, The amount of water consumed in the electrolysis process, is the molar mass of water, I is the current passing through the electrolytic cell, N is the number of electrolytic cells in the electrolytic cell, t is the reaction time, η is the current efficiency of the electrolytic cell, and F is the Faraday constant.

4. The method for calculating current efficiency based on the water consumption principle according to claim 2, characterized in that: S1 includes: Based on the absolute humidity, the amount of water carried away by the gas is calculated using the following formula: Where n wg is the amount of water carried away by the gas, is the total volume of hydrogen generated during the electrolysis process; The total volume of oxygen generated by the electrolysis process; is the absolute humidity of hydrogen; is the absolute humidity of oxygen.

5. The method for calculating current efficiency based on the water consumption principle according to claim 4, characterized in that: In S1, the absolute humidity is calculated as follows: Where AH is absolute humidity; T a is the current temperature of the gas, e y is the actual water vapor pressure.

6. The method for calculating current efficiency based on the water consumption principle according to claim 1, characterized in that: S1 includes: The total water consumption of the hydrogen production device is obtained by the liquid level difference method, and the calculation formula is as follows: m w =(V 11 ×ρ1-V 12 ×ρ2)+(V 21 ×ρ1-V 22 ×ρ2) Where V 11 is the volume of alkali solution in the hydrogen side gas-liquid separator or buffer tank at the beginning of the test; ρ1 is the density of alkali solution in the system measured at the beginning of the test; V 12 is the volume of alkali solution in the hydrogen side gas-liquid separator or buffer tank at the end of the test; ρ2 is the density of alkali solution in the system measured at the end of the test; V 21 V is the volume of alkali solution in the oxygen side gas-liquid separator or buffer tank at the beginning of the test; 22 It is the volume of alkaline solution in the oxygen side gas-liquid separator / buffer tank at the end of the test.

7. The method for calculating current efficiency based on the water consumption principle according to claim 1, characterized in that: S1 includes: The total water consumption of the hydrogen production device is obtained by the flow meter method, and the calculation formula is as follows: In the formula, Q e Q is the flow meter reading at the end of water replenishment; s It is the flow meter reading at the beginning of water replenishment; is the density of pure water.

8. A system for calculating current efficiency based on the water consumption principle, characterized in that: The system comprises: A data acquisition and processing module (3) is used to acquire and process water flow and gas parameter data in real time; A calculation module (4), configured to execute the method according to claim 1 and calculate the current efficiency; The result output and display module (5) is used to output and display the calculated current efficiency.

9. The system for calculating current efficiency based on the water consumption principle according to claim 8, characterized in that: The system comprises a liquid level and flow monitoring module (1). When the liquid level difference method is adopted, the liquid level and flow monitoring module (1) comprises a real-time liquid level monitoring device for the liquid level at the beginning and end of the test.

10. The system for calculating current efficiency based on the water consumption principle according to claim 8, characterized in that: When the flow meter method is adopted, the system includes a flow meter for real-time monitoring and cumulative measurement of the water flow entering the electrolytic cell.

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