Method for increasing current efficiency of an electrolytic cell

Abstract

The application discloses a method for improving current efficiency of an electrolytic cell, and relates to the technical field of electrolytic aluminum, which guarantees stable thermal balance of the electrolytic cell and improves current efficiency. The main technical scheme of the application is as follows: the method for improving current efficiency of the electrolytic cell comprises the following steps: S1, parameter acquisition and configuration; S2, target parameter determination and configuration; S3, current state parameter setting; S4, voltage additional amount calculation; S5, aluminum fluoride addition amount calculation; S6, voltage regulation execution; and S7, aluminum fluoride feeding control.

Description

Technical Field

[0001] This invention relates to the field of electrolytic aluminum production technology, and in particular to a method for improving the current efficiency of an electrolytic cell. Background Technology

[0002] The production efficiency of an electrolytic cell is a key indicator of its performance. The main factors determining this efficiency are current intensity and current efficiency. Current intensity, the magnitude of the direct current flowing through the electrolytic cell, is set on the cell and remains constant throughout its operating cycle. It affects not only the quality of the produced aluminum but also the cell's thermal balance, i.e., its operating state. Current efficiency is the percentage of electricity actually consumed compared to the theoretically required electricity. The current efficiency of an electrolytic cell depends on several factors, such as the current distribution between the anode and cathode, the electrolyte temperature, the alumina content, the molecular weight ratio (CR), and other interrelated parameters.

[0003] As the electrolyte temperature increases, dissolved metals migrate more quickly to the anode space and oxidize there due to increased metal solubility, accelerated ion diffusion, and enhanced mass transfer within the electrolyte. Therefore, the melt temperature should not exceed the optimal range (950–960°C), as this reduces current efficiency and consequently energy efficiency. Experiments show that for every 10°C increase in cryolite-alumina melt temperature, current efficiency decreases by 2–3%. However, excessively low temperatures are also undesirable, as they significantly increase electrolyte viscosity, causing metal droplets to become trapped within the electrolyte and resulting in metal loss. Electrolyte temperature variations are influenced by various factors, such as excess aluminum fluoride (AlF3), changes in electrolytic cell voltage, and variations in alumina concentration.

[0004] Increasing the inter-electrode distance improves current efficiency. However, it also increases the voltage drop across the electrolyte, leading to increased energy consumption. Ideally, the inter-electrode distance should be as small as possible, but it's crucial not to exceed a critical value, as exceeding this value can cause negative problems such as frequent anodic effects and alumina precipitation.

[0005] The molecular ratio (CR) also has a significant impact on current efficiency, as it characterizes the chemical composition of the electrolyte. The target CR is typically determined empirically depending on the specific technology used, but within the target range, it requires individual calculation and control.

[0006] Considering that the production efficiency of an electrolytic cell is affected by a variety of parameters, which affect its operation in different ways, it is important to keep the parameters of the electrolytic cell within the range specified in the technical specifications and minimize their fluctuations in order to achieve long-term stable operation of the electrolysis process.

[0007] None of the existing electrolyzer control methods can fully and comprehensively control the thermal balance within the electrolyzer, and therefore cannot correct it more effectively. Summary of the Invention

[0008] In view of this, the present invention provides a method for improving the current efficiency of an electrolytic cell. The main purpose is to calculate and adjust the relationship between voltage change and aluminum fluoride addition in steps to ensure the thermal balance of the electrolytic cell is stable and improve the current efficiency.

[0009] To achieve the above objectives, the present invention mainly provides the following technical solutions:

[0010] This invention provides a method for improving the current efficiency of an electrolyzer, the method comprising the following steps:

[0011] S1. Parameter Acquisition and Configuration: Acquire the minimum voltage change ΔU during the aluminum electrolysis cell production process at a preset frequency. min and the maximum voltage change ΔU max The minimum voltage change ΔU min and the maximum voltage change ΔU max It is configured into the control system as a limiting condition for voltage regulation;

[0012] S2. Target parameter determination and configuration: Based on the thermal balance principle of aluminum electrolysis cell, the target electrolyte temperature T, target molecular ratio CR and target voltage U required to maintain the optimal thermal balance state of the electrolysis cell are calculated, and the target electrolyte temperature T, target molecular ratio CR and target voltage U are configured into the control system.

[0013] S3. Current state parameter setting: Extract the current three sets of continuous electrolyte temperature values ​​T1, T2, T3 and the CR value obtained from the current measurement, and input the above parameters as the basic parameters for the current thermal state assessment into the control system.

[0014] S4. Voltage Additional Calculation: Based on the current thermal balance deviation, calculate the voltage additional ΔU required to correct the current thermal balance deviation using formula (1):

[0015] (1);

[0016] In equation (1), a0 to a7 are regression coefficients obtained based on the thermodynamic state modeling of aluminum electrolysis cells; CR is the electrolyte molecular ratio, which is a key parameter for controlling the composition of aluminum electrolyte; T = (T1 + T2 + T3) / 3;

[0017] S5. Calculation of aluminum fluoride addition: Based on the current electrolyte composition parameters, the control system calculates the excess percentage of AlF3 in the electrolyte relative to pure cryolite, xsAlF3, through formula (2), and then determines the required amount of aluminum fluoride to be added. Reasonable addition of aluminum fluoride can reduce the initial crystallization temperature, reduce heat consumption, reduce the solubility of aluminum in the electrolyte and the loss of secondary reaction. Combined with low voltage operation, it can reduce the power consumption per ton of aluminum.

[0018] (2)

[0019] In formula (2): xsAlF3 is the excess percentage of AlF3, that is, the excess percentage of the actual cryolite content relative to the theoretical ratio content; %CaF2, %MgF2, %LiF, and %Al2O3 are the mass percentages of calcium fluoride, magnesium fluoride, lithium fluoride additives, and alumina in the electrolyte, respectively.

[0020] S6. Voltage Regulation Execution: Based on the voltage adjustment ΔU calculated in step S4 and the current voltage U... 现 Determine the new set voltage U 新 U 新 =U 现 +ΔU; the new set voltage U 新 The voltage is controlled by adjusting the electrode spacing of the electrolytic cell;

[0021] S7. Aluminum fluoride feeding control: The amount of aluminum fluoride added calculated in step S5 is converted into the activation trigger time of the aluminum fluoride feeder, and the trigger time command is sent to the aluminum fluoride feeder to control the feeder to perform precise feeding.

[0022] The objectives of this invention and the technical problems it addresses can be further achieved by the following technical measures.

[0023] Optionally, in step S3, the time interval for monitoring the three sets of continuous electrolyte temperature values ​​T1, T2, and T3 is 10 seconds.

[0024] Optionally, in step S4, a0=0.85, a1=0.12, a2=0.65, a3=1.20, a4=0.45, a5=0.90, a6=0.30, and a7=0.60.

[0025] Optionally, in steps S4 and S5, the control system correlates the current thermal state of the electrolytic cell and the heat change ΔQ required for the thermal state transition in real time, ensuring that the voltage boost and aluminum fluoride addition can adapt to the thermal state change requirements of the electrolytic cell, thereby improving the accuracy of the electrolytic cell's thermal balance control.

[0026] By employing the above technical solution, the present invention has at least the following advantages:

[0027] 1. This invention innovatively incorporates the current thermal state of the electrolytic cell and the heat change ΔQ required for the transition of the thermal state into the control considerations. By establishing a synergistic relationship between voltage change and aluminum fluoride addition through step-by-step calculation, it solves the problems of poor synergy and control lag caused by independent control of the two in the prior art.

[0028] 2. By accurately calculating the voltage boost and aluminum fluoride excess value, the electrolyte temperature and AlF3 excess value are stably maintained within the optimal range, effectively reducing the fluctuation range of thermal balance parameters and significantly improving the operational stability of the electrolyzer.

[0029] 3. Relying on the collaborative processing of multi-module data and the coordinated operation of core algorithms, precise linkage control of voltage regulation and aluminum fluoride feeding is achieved. It can quickly correct thermal balance deviations, improve current efficiency, and reduce production energy consumption, which has significant economic value and application prospects. Attached Figure Description

[0030] Figure 1 A flowchart of a method for improving the current efficiency of an electrolyzer, provided as an embodiment of the present invention. Detailed Implementation

[0031] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the specific implementation methods, structures, features, and effects according to the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. In the following description, different "an embodiment" or "an embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0032] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0033] like Figure 1 As shown, an embodiment of the present invention provides a method for improving the current efficiency of an electrolyzer, which includes the following steps:

[0034] S1. Parameter Acquisition and Configuration: Acquire the minimum voltage change ΔU during the aluminum electrolysis cell production process at a preset frequency. min and the maximum voltage change ΔU max The minimum voltage change ΔU min and the maximum voltage change ΔU max It is configured into the control system as a limiting condition for voltage regulation;

[0035] S2. Target parameter determination and configuration: Based on the thermal balance principle of aluminum electrolysis cell, the target electrolyte temperature T, target molecular ratio CR and target voltage U required to maintain the optimal thermal balance state of the electrolysis cell are calculated, and the target electrolyte temperature T, target molecular ratio CR and target voltage U are configured into the control system.

[0036] S3. Current state parameter setting: Extract the current three sets of continuous electrolyte temperature values ​​T1, T2, T3 and the CR value obtained from the current measurement. The time interval for monitoring the electrolyte temperature value is 10 seconds. Input the above parameters into the control system as the basic parameters for the current thermal state assessment.

[0037] S4. Voltage Additional Calculation: Based on the current thermal balance deviation, calculate the voltage additional ΔU required to correct the current thermal balance deviation using formula (1):

[0038] (1);

[0039] In equation (1), a0 to a7 are regression coefficients obtained based on the thermodynamic state modeling of aluminum electrolytic cells, a0=0.85, a1=0.12, a2=0.65, a3=1.20, a4=0.45, a5=0.90, a6=0.30, a7=0.60; CR is the electrolyte molecular ratio, which is a key parameter for controlling the composition of aluminum electrolyte; T=(T1+T2+T3) / 3;

[0040] S5. Calculation of aluminum fluoride addition: Based on the current electrolyte composition parameters, the control system calculates the excess percentage of AlF3 in the electrolyte relative to pure cryolite using formula (2), xsAlF3, and then determines the required amount of aluminum fluoride to be added. The conversion between the excess percentage of cryolite and the amount of aluminum fluoride (AlF3) added is based on the change in the electrolyte molecular ratio (CR = n(NaF) / n(AlF3), molar ratio). Excess cryolite (%) = (3 - CR) ÷ (3+CR) × 100%. Reasonable addition of aluminum fluoride can reduce the initial crystallization temperature, reduce heat consumption, reduce the solubility of aluminum in the electrolyte and the loss of secondary reactions, and reduce the power consumption per ton of aluminum when combined with low voltage operation.

[0041] (2)

[0042] In formula (2): xsAlF3 is the excess percentage of AlF3, that is, the excess percentage of the actual cryolite content relative to the theoretical ratio content; %CaF2, %MgF2, %LiF, and %Al2O3 are the mass percentages of calcium fluoride, magnesium fluoride, lithium fluoride additives, and alumina in the electrolyte, respectively.

[0043] S6. Voltage Regulation Execution: Based on the voltage adjustment ΔU calculated in step S4 and the current voltage U... 现 Determine the new set voltage U 新 U 新 =U 现 +ΔU; the new set voltage U 新 The voltage is controlled by adjusting the electrode spacing of the electrolytic cell;

[0044] S7. Aluminum fluoride feeding control: The amount of aluminum fluoride added calculated in step S5 is converted into the activation trigger time of the aluminum fluoride feeder, and the trigger time command is sent to the aluminum fluoride feeder to control the feeder to perform precise feeding.

[0045] Specifically, the implementation of the control method described in this invention relies on the coordinated processing of multi-module input data by the control system. The control system receives three types of input data: Module 1 is the parameter constraint conditions in the configuration file, namely the minimum voltage change ΔU and the maximum voltage change ΔU in step S1; Module 2 is the target parameter set, namely the target electrolyte temperature T, the target CR value CR, and the target voltage U in step S2; Module 3 is the current process parameters, namely the current three temperature measurements of the electrolyte and the current CR value measurement in step S3.

[0046] Example 1: Standard Steady-State Operating Conditions of a 400KA Electrolyzer

[0047] 1. Basic Operating Conditions Description

[0048] This embodiment is for an aluminum electrolytic cell in normal production with process parameters within the optimal range, and a rated current of 400KA. The target process range is: electrolyte temperature 950~960℃, electrolyte molecular weight ratio CR = 2.20~2.25, and target set voltage U. 目 =4.05V. There is no anodic effect or alumina precipitation on site, and the thermal balance of the electrolytic cell is in an ideal state.

[0049] 2. Step Execution Process

[0050] S1 Parameter Acquisition and Configuration

[0051] The voltage change is collected at a frequency of 1 minute / time, and the voltage regulation limits are set: ΔUmin=-0.02V, ΔUmax=+0.02V. The parameters are then entered into the control system.

[0052] S2 target parameter configuration

[0053] Based on the thermal balance model of a 400kA electrolyzer, the target parameters are configured as follows: target electrolyte temperature T. 目 =955℃, target molecule ratio CR 目=2.22, target voltage U 目 =4.05V.

[0054] S3 Current State Parameter Extraction

[0055] The current temperatures of the three continuous electrolytes are: T1 = 954.8℃, T2 = 955.1℃, and T3 = 954.9℃, with an average temperature of T≈954.93℃.

[0056] The current measured electrolyte molecular ratio is CR = 2.22.

[0057] S4 Voltage Additional Calculation

[0058] The control system substitutes T and CR (2.22) into formula (1). The regression coefficients a0 to a7 in the formula have been obtained in advance through thermodynamic modeling and experimental data fitting, and are fixed in the system. The calculation yields: ΔU≈-0.005V.

[0059] S5 Aluminum Fluoride Addition Calculation

[0060] Electrolyte composition tested on-site: %CaF2=4.2%, %MgF2=2.1%, %LiF=1.5%, %Al2O3=2.0%. The excess percentage of AlF3, xsAlF3, was calculated to be 8.6% using formula (2). Based on the molecular ratio conversion, the theoretical addition amount of aluminum fluoride per tank per batch was determined to be 12.5 kg.

[0061] Excess percentage of cryolite (%) = (3-CR)÷(3+CR)×100%;

[0062] Substituting xsAlF3=8.6% into the above formula, we get CR=2.525. Taking 1 mol AlF3 as the baseline, and converting it using the molecular ratio CR= n(NaF) / n(AlF3), the mass fraction of AlF3 in the cryolite system is 44.23%.

[0063] Considering the influence of impurities such as CaF2, MgF2, and LiF, the effective AlF3 mass fraction is calculated to be 36.8%. Combined with the total electrolyte volume of approximately 34 kg per tank, the theoretical amount of aluminum fluoride added per tank per batch is:

[0064] M(AlF3)=34×0.368=12.5kg.

[0065] S6 Voltage Regulation Execution

[0066] The new voltage setting is: U = 4.05V + (-0.005V) = 4.045V. The control system issues a command to fine-tune the distance between the electrodes, thus completing the precise voltage adjustment.

[0067] S7 Aluminum Fluoride Feeding Control

[0068] The addition of 12.5 kg of aluminum fluoride was converted into a feeder trigger time of 18 seconds, and a command was issued to control the feeder to quantitatively add material. (The trigger time was determined based on the feeder's feeding capacity under calibrated operating conditions.)

[0069] 3. Implementation Results

[0070] After adjustment, continuous monitoring for 24 hours showed that the electrolyte temperature remained stable at 954.7~955.3℃, the molecular ratio remained in the range of 2.21~2.23, the current efficiency remained stable at 94.2%, the power consumption per ton of aluminum did not fluctuate significantly, and the thermal balance of the electrolytic cell remained stable for a long time.

[0071] Example 2: 400KA Electrolyte Temperature Too High Operating Condition Example

[0072] 1. Basic Operating Conditions Description

[0073] The 400KA prebaked aluminum electrolytic cell was affected by excessively high voltage and fluctuating alumina feeding rhythm in the early stage, resulting in an excessive electrolyte temperature with an average temperature of 964℃, exceeding the optimal process range of 950~960℃, accompanied by a slight decrease in current efficiency; the electrolyte molecular ratio CR=2.23, which is within the acceptable range. There was no bottom sedimentation or anodic effect on site. The control target is to reduce the electrolytic cell temperature back to the optimal process range while maintaining a stable molecular ratio.

[0074] 2. Step Execution Process

[0075] S1 Parameter Acquisition and Configuration

[0076] The voltage change is collected at a frequency of 1 minute / time, and the voltage regulation limits are used: ΔUmin=-0.02V, ΔUmax=+0.02V. The parameters are entered into the control system.

[0077] S2 target parameter configuration

[0078] Based on the thermal balance model of a 400kA electrolyzer, the target parameters are configured as follows: target electrolyte temperature T. 目 =955℃, target molecule ratio CR 目 =2.22, target voltage U 目 =4.05V.

[0079] S3 Current State Parameter Extraction

[0080] The current temperatures of the three continuous electrolytes are: T1 = 963.8℃, T2 = 964.2℃, and T3 = 963.9℃, with an average temperature of T≈964℃.

[0081] The current measured electrolyte molecule ratio is CR = 2.23.

[0082] S4 Voltage Additional Calculation

[0083] The control system substitutes T and CR(2.20) into formula (1) for calculation. The regression coefficients a0 to a7 in the formula have been obtained in advance through thermodynamic modeling and experimental data fitting, and are fixed in the system. The calculation yields: ΔU≈-0.045V.

[0084] Results analysis: The voltage increment is a large negative value (-45mV). The formula quantifies the need to reduce heat input. Since the single adjustment limit is ±20mV, the system will execute the adjustment in steps.

[0085] S5 Aluminum Fluoride Addition Calculation

[0086] On-site testing of the electrolyte composition revealed the following: %CaF2 = 4.1%, %MgF2 = 2.0%, %LiF = 1.4%, and %Al2O3 = 1.9%. Calculations showed an AlF3 excess percentage of xsAlF3 = 9.1%. Based on molecular ratio conversion, the theoretical single-time aluminum fluoride addition for a single cell was determined to be 14.2 kg. Adding aluminum fluoride can lower the initial crystallization temperature of the electrolyte and assist in cooling the electrolytic cell.

[0087] S6 Voltage Regulation Execution

[0088] Step 1 adjustment: U = 4.050V + (-0.020V) = 4.030V. The system reduces the voltage to 4.030V. After a 15-minute interval, it recalculates: if the temperature is still too high, the system will recalculate and execute step 2, a -20mV adjustment, until the cumulative correction requirement of -45mV is reached.

[0089] S7 Aluminum Fluoride Feeding Control

[0090] The addition of 14.2 kg of aluminum fluoride is converted into a feeder trigger time of 20 seconds (the feeder is activated for 5 seconds every 10 minutes) to perform precise quantitative feeding.

[0091] 3. Implementation Results

[0092] Six hours after adjustment, the bath temperature dropped to 957.2℃. After 24 hours of continuous operation, the electrolyte temperature stabilized at 955~957℃, and the molecular ratio remained in the range of 2.22~2.24. In this embodiment, the system detected that the temperature was too high. First, it directly reduced the Joule heat input by significantly reducing the voltage (ΔU = -45mV), which is the fastest way to correct the thermal balance. At the same time, the amount of AlF3 added was increased to lower the primary crystallization temperature of the electrolyte from a compositional perspective, providing long-term support for the thermal balance level. The synergistic effect of the two measures effectively and quickly suppressed the temperature rise trend and avoided a decrease in current efficiency.

[0093] Example 3: 400KA Electrolyzer with High Molecular Ratio and Low Temperature

[0094] 1. Basic Operating Conditions Description

[0095] This 400kA prebaked aluminum electrolytic cell is experiencing two abnormal operating conditions due to insufficient long-term aluminum fluoride replenishment: the electrolyte molecular ratio CR = 2.31, higher than the target range; and the average electrolyte temperature of 946℃, lower than the lower limit of the process optimum. Increased electrolyte viscosity easily leads to aluminum entrainment losses, while the cell voltage fluctuation amplitude significantly increases. The control objectives are: to simultaneously correct the excessively high molecular ratio, increase the cell temperature, and fully restore the thermal balance of the electrolytic cell.

[0096] 2. Step Execution Process

[0097] S1 Parameter Acquisition and Configuration

[0098] The voltage change is collected at a frequency of 1 minute / time, and the voltage regulation limits are set: ΔUmin=-0.02V, ΔUmax=+0.02V. The parameters are then entered into the control system.

[0099] S2 target parameter configuration

[0100] Based on the thermal balance model of a 400kA electrolyzer, the target parameters are configured as follows: target electrolyte temperature T. 目 =955℃, target molecule ratio CR 目 =2.22, target voltage U 目 =4.05V.

[0101] S3 Current State Parameter Extraction

[0102] Extract the current three consecutive electrolyte temperatures: T1=945.7℃, T2=946.1℃, T3=945.9℃, with an average temperature T≈946℃;

[0103] The current measured electrolyte molecule ratio is CR = 2.31.

[0104] S4 Voltage Additional Calculation

[0105] The control system substitutes T and CR(2.31) into formula (1) for calculation. The regression coefficients a0 to a7 in the formula have been obtained in advance through thermodynamic modeling and experimental data fitting, and are fixed in the system. The calculation yields: ΔU≈ +0.025V.

[0106] S5 Aluminum Fluoride Addition Calculation

[0107] Electrolyte composition measured on-site: %CaF2=4.3%, %MgF2=2.2%, %LiF=1.6%, %Al2O3=2.1%. The calculated excess AlF3 content (xsAlF3) was 7.8%. Considering the relatively high molecular weight ratio, the single-time aluminum fluoride addition amount per tank was determined to be 16.8 kg to enhance the molecular weight ratio correction effect.

[0108] S6 Voltage Regulation Execution

[0109] The system determined that +25mV exceeded the single-pass limit of +20mV, therefore it executed the operation in two steps:

[0110] Step 1: U = 4.050V + 0.020V = 4.070V.

[0111] The second step was to monitor for any abnormalities and then proceed to +0.025V, eventually stabilizing the voltage at 4.075V.

[0112] S7 Aluminum Fluoride Feeding Control

[0113] The addition of 16.8 kg of aluminum fluoride is converted into a feeder trigger time of 24 seconds (the feeder is activated for 5 seconds every 10 minutes) to complete the quantitative feeding.

[0114] 3. Implementation Results

[0115] After 12 hours of adjustment, the electrolyte temperature rose to 951.5℃, and the molecular ratio decreased to 2.27. After 48 hours of continuous operation, the temperature stabilized at 953~955℃, and the molecular ratio stabilized within the standard range of 2.21~2.23. The electrolyte fluidity returned to normal, the aluminum liquid entrainment loss was significantly reduced, the current efficiency increased to 94.1%, and the electrolytic cell achieved long-term thermal equilibrium and stable operation.

[0116] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for improving the current efficiency of an electrolytic cell, characterized in that, Includes the following steps: S1. Parameter Acquisition and Configuration: Acquire the minimum voltage change ΔU during the aluminum electrolysis cell production process at a preset frequency. min and the maximum voltage change ΔU max The minimum voltage change ΔU min and the maximum voltage change ΔU max It is configured into the control system as a limiting condition for voltage regulation; S2. Target parameter determination and configuration: Based on the thermal balance principle of aluminum electrolysis cell, the target electrolyte temperature T, target molecular ratio CR and target voltage U required to maintain the optimal thermal balance state of the electrolysis cell are calculated, and the target electrolyte temperature T, target molecular ratio CR and target voltage U are configured into the control system. S3. Current state parameter setting: Extract the current three sets of continuous electrolyte temperature values ​​T1, T2, T3 and the CR value obtained from the current measurement, and input the above parameters as the basic parameters for the current thermal state assessment into the control system. S4. Voltage Additional Calculation: Based on the current thermal balance deviation, calculate the voltage additional ΔU required to correct the current thermal balance deviation using formula (1): （1） In equation (1), a0 to a7 are regression coefficients obtained based on the thermodynamic state modeling of aluminum electrolytic cells; CR is the electrolyte molecular ratio, which is a key parameter for controlling the composition of aluminum electrolyte; T = (T1 + T2 + T3) / 3; S5. Calculation of aluminum fluoride addition: Based on the current electrolyte composition parameters, the control system calculates the excess percentage of AlF3 in the electrolyte relative to pure cryolite, xsAlF3, through formula (2), and then determines the required amount of aluminum fluoride to be added. （2） In formula (2): xsAlF3 is the excess percentage of AlF3, that is, the excess percentage of the actual cryolite content relative to the theoretical ratio content; %CaF2, %MgF2, %LiF, and %Al2O3 are the mass percentages of calcium fluoride, magnesium fluoride, lithium fluoride additives, and alumina in the electrolyte, respectively. S6. Voltage Regulation Execution: Based on the voltage adjustment ΔU calculated in step S4 and the current voltage U... 现 Determine the new set voltage U 新 U 新 =U 现 +ΔU; the new set voltage U 新 The voltage is controlled by adjusting the electrode spacing of the electrolytic cell; S7. Aluminum fluoride feeding control: The amount of aluminum fluoride added calculated in step S5 is converted into the activation trigger time of the aluminum fluoride feeder, and the trigger time command is sent to the aluminum fluoride feeder to control the feeder to perform precise feeding.

2. The method for improving the current efficiency of an electrolytic cell according to claim 1, characterized in that, In step S3, the time interval for monitoring the three sets of continuous electrolyte temperature values ​​T1, T2, and T3 is 10 seconds.

3. The method for improving the current efficiency of an electrolytic cell according to claim 1, characterized in that, In step S4, a0=0.85, a1=0.12, a2=0.65, a3=1.20, a4=0.45, a5=0.90, a6=0.30, a7=0.

60.

4. The method for improving the current efficiency of an electrolytic cell according to claim 1, characterized in that, In steps S4 and S5, the control system correlates the current thermal state of the electrolytic cell with the heat change ΔQ required for the transition of the thermal state in real time.

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