Method for calculating abnormal post-starting period large alkali addition amount of aluminum electrolytic cell

Abstract

The present application relates to the field of aluminum electrolysis, and provides a method for calculating the abnormal post-starting period large alkali addition amount of an aluminum electrolysis cell; the method is characterized in that: by collecting the structure parameters, operation data and material composition of the electrolysis cell, the electrolyte inventory, the daily input fluorine-carrying aluminum oxide amount and the furnace side solidification consumption amount are accurately calculated, and a dynamic material balance system is constructed. The actual production data of multiple newly started cells are used to dynamically calibrate two key parameters of the fluorine-carrying aluminum oxide conversion rate and the sodium carbonate reaction efficiency, so that the theoretical model is fitted to the actual production. Based on the calibrated model, the natural downward trend of the molecular ratio can be accurately predicted, and by solving the material balance equation, the theoretical weight of the sodium carbonate required to be added daily to maintain the target molecular ratio can be quantitatively calculated, and finally converted into the industrial large alkali physical addition amount. The method can effectively stabilize the electrolyte molecular ratio, significantly reduce the analysis frequency, and avoid the waste of additives, and provides a reliable technical means for the smooth and economic transition of the electrolysis cell to the normal period.

Description

Technical Field

[0001] This invention relates to the field of aluminum electrolysis technology, and more specifically, to a method for calculating the amount of alkali added during the abnormal period after startup of an aluminum electrolysis cell. Background Technology

[0002] In aluminum electrolysis production, cell lifespan and production stability are key performance indicators. To form a dense and stable high-molecular-weight (NaF-AlF3-Al2O3) eutectic layer on the surface of the side carbon blocks during the abnormal period after cell startup, effectively isolating the electrolyte from the molten aluminum, the molecular ratio of the electrolyte (i.e., the molar ratio of NaF to AlF3) must be controlled and maintained at a high level, typically greater than 3. Maintaining this high molecular ratio is crucial for ensuring the safe and stable operation of the electrolytic cell and extending its service life. However, during abnormal periods, the formation process of the lining solidifies and consumes sodium ions in the electrolyte, while the cell lining material also absorbs sodium ions. Furthermore, the continuous addition of fluorinated alumina introduces additional aluminum fluoride. These factors collectively lead to acidification of the electrolyte system, i.e., a continuous and rapid decrease in the molecular ratio.

[0003] Currently, the industry commonly uses an empirical method to determine the amount of industrial sodium carbonate (sodium carbonate) to be added based on periodic electrolyte molecular ratio analysis results. This method has significant drawbacks: First, frequent sampling and analysis of the electrolyte are required to track changes in a timely manner, increasing operational complexity and cost. Second, due to the lag in analysis and the lack of forward-looking quantitative calculations, fluctuations deviating from the target range (e.g., 3.0~3.5) are prone to occur, affecting the stable formation of the furnace lining. Finally, relying on empirical judgment can easily lead to inappropriate additive addition, either insufficient addition affecting process objectives or excessive addition causing material waste. Furthermore, during the subsequent transition to normal operation, a large amount of aluminum fluoride is needed to neutralize the excess sodium, further increasing costs and production control difficulties. Therefore, developing a quantitative calculation method that can pre-calculate and accurately guide the addition of sodium carbonate, thereby achieving stable molecular ratios, reducing analysis frequency, and avoiding material waste, has become an urgent technical need in this field. Summary of the Invention

[0004] In view of the above-mentioned shortcomings in the prior art, the core objective of the present invention is to provide a method for calculating the amount of alkali added during the abnormal period after startup of an aluminum electrolytic cell, which can prevent the molecular ratio from deviating from the standard range, reduce the number of molecular ratio analyses, and reduce additive waste.

[0005] This invention is achieved through the following technical solution: The present invention provides a method for calculating the amount of alkali added during the abnormal period after startup of an aluminum electrolysis cell, comprising the following steps: S1. Based on the structural parameters, operating parameters, and electrolyte composition analysis after startup of the electrolytic cell, the weight of the liquid electrolyte in the electrolytic cell, the initial weight of sodium fluoride in the electrolytic cell, and the initial weight of aluminum fluoride in the electrolytic cell are obtained. S2. Based on the actual aluminum production of the electrolytic cell, the series of material consumption data, and the composition analysis of the fluorinated alumina, the daily weight of the fluorinated alumina entering the electrolytic cell, the daily weight of sodium fluoride, and the daily weight of aluminum fluoride are obtained. S3. Based on the parameters and composition analysis of the furnace lining, obtain the daily weight of electrolyte consumed due to the solidification of the furnace lining, the daily weight of sodium fluoride and aluminum fluoride consumed as a result. S4. Based on the measured molecular ratio data of multiple newly started electrolytic cells without added alkali during the initial abnormal period, the conversion ratio of relevant components in fluorinated alumina to aluminum fluoride was obtained. S5. Based on the measured molecular ratio data of multiple newly started electrolytic cells after quantitative addition of sodium carbonate, the proportion of sodium carbonate actually participating in the chemical reaction is obtained. S6. Based on the weights of each material obtained in steps S1 to S3 and the conversion ratio obtained in step S4, establish a material balance model to calculate the dynamic change trend of the electrolyte molecular ratio with the number of production days without adding alkali. S7. Set the target molecular ratio standard value for the abnormal period, and determine the starting date for adding the large base based on the trend of the molecular ratio change; S8. Based on the reaction ratio obtained in step S5, calculate the theoretical weight of sodium carbonate required to be added daily from the start date to maintain the target molecular ratio, according to the target molecular ratio standard value, the start date and the material balance model. S9. Based on the purity of sodium carbonate in the alkali and the theoretical weight of sodium carbonate, the actual daily weight of alkali to be added is obtained.

[0006] Further, in step S1, the weight m of the liquid electrolyte in the electrolytic cell is calculated using the following formula:

[0007] In the formula, ρ is the density of the liquid electrolyte, and a 炉 b is the length of the electrolytic cell furnace. 炉 d is the width of the electrolytic cell furnace, c is the average thickness of the furnace side walls on the main surface, d is the average thickness of the furnace side walls at the ends, h is the electrolyte height, and a is the average thickness of the end furnace side walls. 阳 b is the anode length. 阳 h is the anode width. 极 The distance is the electrode spacing, and n is the number of anodes in a single cell.

[0008] Further, in step S2, the daily weight m of fluorinated alumina entering the electrolytic cell... 氧化铝It is calculated using the following formula:

[0009] In the formula, Q 实 Q represents the actual aluminum output from the electrolytic cell. 系列载氟氧化铝 Q represents the consumption of fluorinated alumina in a series of electrolytic cells. 系列实 This represents the actual aluminum output of the series of electrolytic cells; The daily intake of sodium fluoride weight m 2NaF and aluminum fluoride weight m 2AlF3 The results are obtained using the following formulas:

[0010] In the formula, w% (Na2O) The weight percentage (w%) of Na₂O in fluorinated alumina. (F) This represents the weight percentage of F in fluorinated alumina.

[0011] Further, in step S3, the daily electrolyte consumption mconsumption during curing is calculated using the following formula:

[0012] In the formula, m 炉 The weight of the furnace wall in the electrolytic cell after one month is calculated using the formula m. 炉 =ρ 炉 ×(2×a 炉 ×c×h+2×b 炉 ρ is calculated as (×d×h). 炉 This refers to the density of the furnace side.

[0013] Further, in step S4, the conversion ratio α is the average value calculated based on multi-day data from multiple electrolytic cells, where the conversion ratio α on day n is... n It is calculated using the following formula:

[0014] In the formula, m 1NaF and m 1AlF3 The initial weights of sodium fluoride and aluminum fluoride obtained in step S1 are m, respectively. 2NaF and m 2AlF3 The daily intake of sodium fluoride and aluminum fluoride, respectively, is obtained in step S2, m 消NaF and m 消AlF3 The daily consumption of sodium fluoride and aluminum fluoride, respectively, is obtained in step S3. (C) n实 The measured molecular weight ratio of the electrolyte on day n.

[0015] Furthermore, in step S5, the proportion α of sodium carbonate actually participating in the chemical reaction is... 反This is an average value calculated based on multiple days of data after adding sodium carbonate to multiple electrolytic cells, where the proportion α after x days of continuous addition is... 反x It is calculated using the following formula:

[0016] In the formula, C 加x m represents the measured molecular weight on day x after the initial addition of sodium carbonate. Na2CO3加 The fixed daily weight of sodium carbonate is given, n is the number of days before the addition begins, and α is the conversion ratio obtained in step S4.

[0017] Furthermore, in step S6, the material balance model is used to calculate the electrolyte molecule ratio C on day n. n The formula is:

[0018] In the formula, K n The ratio of NaF to AlF3 on day n is given.

[0019] Further, in step S7, the starting date is day n+1, determined by the molecular ratio C on day n calculated in step S6. n Greater than the target molecule ratio standard value C 标 And the molecule ratio on day n+1 is C n+1 Less than C 标 .

[0020] Furthermore, in step S8, the theoretical weight m of sodium carbonate to be added on the starting date, i.e., the (n+1)th day. Na2CO3加1 It is calculated using the following formula:

[0021] Where, α 反 This represents the proportion of sodium carbonate obtained in step S5 that actually participated in the chemical reaction.

[0022] Furthermore, after 75-85 days of operation of the electrolytic cell, the addition of alkali is stopped to allow the molecular ratio to decrease naturally. After 85-95 days of operation, aluminum fluoride is added to reduce the molecular ratio to the standard range for normal operation.

[0023] The method for calculating the amount of alkali added during the abnormal period after startup of an aluminum electrolytic cell, provided by this invention, establishes a systematic, quantitative control system that includes dynamic feedback steps. This method fundamentally changes the traditional, extensive control model that relies on delayed testing and experience-based judgment. It effectively solves three core technical problems: preventing molecular ratios from deviating from the standard range, reducing the number of molecular ratio analyses, and minimizing additive waste. Its problem-solving approach forms a complete logical closed loop: starting with establishing a precise data foundation, then dynamically calibrating key parameters, and ultimately achieving forward-looking prediction and precise quantitative execution.

[0024] This method first establishes a precise real-time material data foundation, overcoming the shortcomings of traditional methods that lack clear understanding of the material state within the electrolytic cell. Specifically, based on the electrolytic cell's design drawings and real-time operating parameters, it calculates the accurate weight of the liquid electrolyte and determines the initial stock of sodium fluoride and aluminum fluoride through sampling analysis, thus clarifying the basic inventory of reactants. Simultaneously, by statistically analyzing the actual aluminum production and series of average consumption data from the electrolytic cell, it extrapolates the daily amount of fluorinated alumina added and, combined with compositional analysis of the raw material, quantitatively calculates the daily increase in sodium fluoride and aluminum fluoride, accurately characterizing the input sources affecting changes in the molecular ratio. Furthermore, by actually measuring the dimensions of the furnace lining and analyzing its composition, this method quantifies the daily solidification and consumption of electrolyte due to furnace lining formation, as well as the corresponding consumption of sodium fluoride and aluminum fluoride, clarifying the main consumption pathways leading to a decrease in the molecular ratio. Through these steps, a dynamic and quantifiable input-inventory-consumption material balance system is established, laying a solid and accurate data foundation for all subsequent calculations.

[0025] Secondly, to address the discrepancy between theoretical chemical calculations and complex actual production environments, this method innovatively introduces a dynamic parameter calibration step based on actual production data. This step elevates the control model from an ideal state to a level closely resembling actual production conditions. Its core lies in tracking the actual molecular ratio decrease data of multiple electrolyzers initially without added alkali, and using reverse fitting to calculate the average conversion ratio (α) of fluoride actually converted to aluminum fluoride in fluorinated alumina, thereby correcting the difference between theoretical chemical reactions and actual complex operating conditions. Simultaneously, by conducting quantitative sodium carbonate addition experiments on multiple electrolyzers and tracking changes in its molecular ratio, reverse fitting is used to calculate the average proportion (α) of the added sodium carbonate participating in the chemical reaction in actual production. 反 This corrects for the loss of additive efficiency caused by incomplete reaction and uneven mixing. Dynamic calibration of these two key parameters significantly improves the accuracy of subsequent prediction and control, and is a core element in achieving precise control and preventing the molecular ratio from deviating from the target.

[0026] Finally, with a solid foundation of accurate data and a calibrated model, this method represents a leap from passive, reactive remediation to proactive, pre-emptive prediction and precise execution. Using the calibrated model, the trend curve of the electrolyte molecular ratio naturally decreasing with increasing production days can be dynamically calculated without the addition of alkali. By comparing this predicted curve with a preset target molecular ratio standard value, the precise start date for adding alkali can be scientifically determined—that is, when the predicted value is about to fall below the target value. This mechanism significantly reduces the frequent molecular ratio analyses previously performed simply to determine the timing of addition. On the determined start date, based on the set target molecular ratio, current material inventory, and calibrated reaction efficiency parameters, the theoretical weight of sodium carbonate required to stabilize the molecular ratio at the target value can be directly calculated using a constructed mathematical equation. This weight is then converted into the actual amount of alkali to be added based on the purity of industrial sodium carbonate. Each subsequent day, the required addition amount can be recalculated based on the latest material balance. This ensures that each addition is a quantitative supplement to achieve precise control targets, fundamentally avoiding insufficient or excessive additions due to reliance on experience-based judgment, greatly reducing unnecessary waste of additives, and stably maintaining the electrolyte molecular ratio within the preset range.

[0027] In summary, this method achieves precise control by accurately measuring material dynamics, calibrating the model to align with actual production through data calibration, and ultimately using model prediction and quantitative calculation. It replaces the traditional detection-reaction passive control mode with a calculable and predictable planned addition system, thus systematically achieving multiple objectives such as stabilizing molecular ratios, reducing analysis frequency, and saving material costs, forming a complete and efficient solution to the technical problem.

[0028] The technical solutions of the embodiments of the present invention have at least the following advantages and beneficial effects: (1) Achieve precise and stable control of molecular ratio: By adding large amount of alkali according to the calculated amount, the molecular ratio of electrolyte can be effectively stabilized and strictly controlled within the preset standard range (such as 3.0~3.5), avoiding large fluctuations and laying the foundation for the formation of high-quality furnace walls.

[0029] (2) Improved production stability: It avoids drastic fluctuations in electrolyte composition caused by empirical addition of additives. The stability of the composition directly reduces process fluctuations during production and improves the overall stability and controllability of the electrolyzer operation.

[0030] (3) Optimize raw material costs and avoid waste: Precise addition prevents the excessive use of alkali from the source. This not only directly saves the consumption of sodium carbonate, but also avoids the secondary material waste caused by the need to add a large amount of aluminum fluoride for neutralization in the later adjustment period due to the high molecular weight ratio in the early stage, thus significantly reducing the overall raw material cost.

[0031] (4) Shorten the adjustment period and improve production efficiency: Precise control makes the molecular ratio at the end of the abnormal period closer to the target upper limit, creating favorable conditions for the subsequent transition to the normal period. This avoids the need to prolong the adjustment period due to the high molecular ratio, which is conducive to the electrolytic cell entering the high-efficiency and low-consumption normal production stage more quickly, and improves current efficiency and aluminum liquid output. Detailed Implementation

[0032] This invention provides a method for calculating the amount of alkali added during the abnormal period after startup of an aluminum electrolysis cell. The specific calculation details are as follows: (1) Calculate the weight of electrolyte in the electrolytic cell after startup based on the furnace size, electrolyte control standard (electrolyte height), electrode distance and anode size in the electrolytic cell design drawings.

[0033]

[0034] Note: Furnace lining 19.62×4.34m; anode bottom surface 1.78×0.76m; after startup, electrolyte height in the electrolytic cell is 27cm, electrode distance is 6cm, and there is no furnace side.

[0035] (2) Electrolyte composition analysis: Based on the results of the electrolyte composition analysis, calculate the weights of NaF and AlF3 in the electrolyte.

[0036]

[0037]

[0038] (3) Calculate the aluminum production of the electrolytic cell during abnormal periods, and estimate the weight of fluorinated alumina entering the electrolytic cell daily based on the series average consumption of fluorinated alumina per ton of aluminum.

[0039]

[0040] (4) Analyze the composition of the fluorinated alumina entering the electrolytic cell and calculate the weight of NaF and AlF3 brought in by the fluorinated alumina each day.

[0041]

[0042]

[0043] (5) During the abnormal period, a dense and stable polymer ratio (NaF-AlF3-Al2O3 eutectic layer) furnace wall will be formed, and a portion of the electrolyte will be solidified every day.

[0044]

[0045] Note: One month after startup, the average thickness of the furnace lining on the main surface of the electrolytic cell was 12cm, the average thickness of the furnace lining at the ends was 14cm, and the furnace lining density was 2.5m³. 3 / t.

[0046] (6) Analysis of the composition of the furnace side of the electrolytic cell. Based on the analysis results, the weights of NaF and AlF3 in the furnace side are calculated.

[0047]

[0048]

[0049] (7) Based on the actual production situation, analyze the changes in the molecular ratio of a certain tank and calculate the conversion ratio of fluorinated alumina to aluminum fluoride.

[0050]

[0051]

[0052]

[0053] (8) Adding Na2CO3 causes a chemical reaction: 3Na2CO3 + 2AlF3 → 6NaF + Al2O3 + 3CO2↑ The reaction equation shows that adding 1 ton of Na2CO3 consumes 168 / 318 tons of AlF3 and produces 84 / 106 tons of NaF.

[0054] In actual production, Na₂CO₃ will not completely react with AlF₃. The proportion of Na₂CO₃ added to the electrolyte that completes the chemical reaction needs to be calculated. Alternatively, a newly started electrolytic cell can be selected, and starting from day 7 (6+1), the amount of Na₂CO₃ added is fixed at 100 kg. The proportion of Na₂CO₃ that completes the chemical reaction is calculated based on the actual changes in molecular ratio analysis results.

[0055]

[0056]

[0057] After startup, the electrolyte height in the electrolytic cell is 27cm, the electrode spacing is 6cm, and there is no furnace side.

[0058]

[0059]

[0060] (9) The only material added during the abnormal period was fluorinated alumina. Based on the electrolyte composition, electrolyte weight, and the amount of fluorinated alumina entering the electrolytic cell, the change in the electrolyte molecular ratio was calculated.

[0061] Taking electrolytic cell 1 as an example:

[0062]

[0063]

[0064] (10) Determine the standard value for controlling the molecular ratio during the abnormal period, for example, the standard value is 3.1, and calculate the time for adding Na2CO3.

[0065] C7>C 标 =3.1>C8 Na₂CO₃ is added starting on day 8. Based on step 9, calculate the amount of Na₂CO₃ to be added on day 8 of the newly started aluminum electrolysis cell:

[0066] (11) Then, based on the amount of Na2CO3 in the purchased alkali, calculate the daily required amount of alkali.

[0067]

[0068] First addition of alkali:

[0069] Subsequent addition of alkali:

[0070] To verify the effectiveness of this invention, three tanks were selected for testing and tracking, and the results are as follows:

[0071]

[0072] The results show that the molecular ratio of the aluminum electrolytic cell with the addition of large amount of alkali is more stable and the relative electrolyte composition fluctuates less. Before the addition of large amount of alkali is stopped, the molecular ratio is close to the standard requirement, which avoids the need for large amounts of aluminum fluoride to be added later and reduces material waste.

[0073] In summary, the advantages of this invention are: it helps stabilize the molecular ratio of the electrolyte, allowing it to fluctuate slightly within a standard range; it avoids large fluctuations in electrolyte composition, reducing production fluctuations caused by composition changes and improving production stability; adding the calculated amount avoids excessive use of alkali, preventing the need for repeated addition of aluminum fluoride later, thus avoiding material waste and optimizing raw material costs; it avoids excessive use of alkali and a high molecular ratio, which leads to a prolonged adjustment period and affects current efficiency; and it avoids insufficient alkali and a low molecular ratio, which results in an insufficiently dense and stable furnace wall, affecting later production and tank life. Using the calculation method of this invention, while ensuring stable production, it can significantly optimize raw material costs, shorten the adjustment period, quickly enter the normal operating period, and increase aluminum liquid production.

Claims

1. A method for calculating the amount of alkali added during the abnormal period after startup of an aluminum electrolytic cell, characterized in that, Includes the following steps: S1. Based on the structural parameters, operating parameters, and electrolyte composition analysis after startup of the electrolytic cell, the weight of the liquid electrolyte in the electrolytic cell, the initial weight of sodium fluoride in the electrolytic cell, and the initial weight of aluminum fluoride in the electrolytic cell are obtained. S2. Based on the actual aluminum production of the electrolytic cell, the series of material consumption data, and the composition analysis of the fluorinated alumina, the daily weight of the fluorinated alumina entering the electrolytic cell, the daily weight of sodium fluoride, and the daily weight of aluminum fluoride are obtained. S3. Based on the parameters and composition analysis of the furnace lining, obtain the daily weight of electrolyte consumed due to the solidification of the furnace lining, the daily weight of sodium fluoride and aluminum fluoride consumed as a result. S4. Based on the measured molecular ratio data of multiple newly started electrolytic cells without added alkali during the initial abnormal period, the conversion ratio of relevant components in fluorinated alumina to aluminum fluoride was obtained. S5. Based on the measured molecular ratio data of multiple newly started electrolytic cells after quantitative addition of sodium carbonate, the proportion of sodium carbonate actually participating in the chemical reaction is obtained. S6. Based on the weights of each material obtained in steps S1 to S3 and the conversion ratio obtained in step S4, establish a material balance model to calculate the dynamic change trend of the electrolyte molecular ratio with the number of production days without adding alkali. S7. Set the target molecular ratio standard value for the abnormal period, and determine the starting date for adding the large base based on the trend of the molecular ratio change; S8. Based on the reaction ratio obtained in step S5, calculate the theoretical weight of sodium carbonate required to be added daily from the start date to maintain the target molecular ratio, according to the target molecular ratio standard value, the start date and the material balance model. S9. Based on the purity of sodium carbonate in the alkali and the theoretical weight of sodium carbonate, the actual daily weight of alkali to be added is obtained.

2. The method for calculating the amount of alkali added during the abnormal period after startup in an aluminum electrolytic cell according to claim 1, characterized in that, In step S1, the weight m of the liquid electrolyte in the electrolytic cell is calculated using the following formula: In the formula, ρ is the density of the liquid electrolyte, and a 炉 b is the length of the electrolytic cell furnace. 炉 d is the width of the electrolytic cell furnace, c is the average thickness of the furnace side walls on the main surface, d is the average thickness of the furnace side walls at the ends, h is the electrolyte height, and a is the average thickness of the end furnace side walls. 阳 b is the anode length. 阳 h is the anode width. 极 The distance is the electrode spacing, and n is the number of anodes in a single cell.

3. The method for calculating the amount of alkali added during the abnormal period after startup in an aluminum electrolytic cell according to claim 1, characterized in that, In step S2, the daily weight m of fluorinated alumina entering the electrolytic cell is... 氧化铝 It is calculated using the following formula: In the formula, Q 实 Q represents the actual aluminum output from the electrolytic cell. 系列载氟氧化铝 Q represents the consumption of fluorinated alumina in a series of electrolytic cells. 系列实 This represents the actual aluminum output of the series of electrolytic cells; The daily intake of sodium fluoride weight m 2NaF and aluminum fluoride weight m 2AlF3 The results are obtained using the following formulas: In the formula, w% (Na2O) The weight percentage (w%) of Na₂O in fluorinated alumina. (F) This represents the weight percentage of F in fluorinated alumina.

4. The method for calculating the amount of alkali added during the abnormal period after startup in an aluminum electrolytic cell according to claim 1, characterized in that, In step S3, the daily electrolyte consumption mdiscarded during curing is calculated using the following formula: In the formula, m 炉 The weight of the furnace wall in the electrolytic cell after one month is calculated using the formula m. 炉 =ρ 炉 ×(2×a 炉 ×c×h+2×b 炉 ρ is calculated as (×d×h). 炉 This refers to the density of the furnace side.

5. The method for calculating the amount of alkali added during the abnormal period after startup in an aluminum electrolytic cell according to claim 1, characterized in that, In step S4, the conversion ratio α is the average value calculated based on multi-day data from multiple electrolytic cells, where the conversion ratio α on day n is... n It is calculated using the following formula: In the formula, m 1NaF and m 1AlF3 The initial weights of sodium fluoride and aluminum fluoride obtained in step S1 are m, respectively. 2NaF and m 2AlF3 The daily intake of sodium fluoride and aluminum fluoride, respectively, is obtained in step S2, m 消NaF and m 消AlF3 The daily consumption of sodium fluoride and aluminum fluoride, respectively, is obtained in step S3. (C) n实 The measured molecular weight ratio of the electrolyte on day n.

6. The method for calculating the amount of alkali added during the abnormal period after startup in an aluminum electrolytic cell according to claim 1, characterized in that, In step S5, the proportion α of sodium carbonate actually participating in the chemical reaction is... 反 This is an average value calculated based on multiple days of data after adding sodium carbonate to multiple electrolytic cells, where the proportion α after x days of continuous addition is... 反x It is calculated using the following formula: In the formula, C 加x m represents the measured molecular weight on day x after the initial addition of sodium carbonate. Na2CO3加 The fixed daily weight of sodium carbonate is given, n is the number of days before the addition begins, and α is the conversion ratio obtained in step S4.

7. The method for calculating the amount of alkali added during the abnormal period after startup in an aluminum electrolytic cell according to claim 1, characterized in that, In step S6, the material balance model is used to calculate the electrolyte molecule ratio C on day n. n The formula is: In the formula, K n The ratio of NaF to AlF3 on day n is given.

8. The method for calculating the amount of alkali added during the abnormal period after startup in an aluminum electrolytic cell according to claim 1, characterized in that, In step S7, the starting date is day n+1, determined by the molecular ratio C on day n calculated in step S6. n Greater than the target molecule ratio standard value C 标 And the molecule on day n+1 is C n+1 Less than C 标 .

9. The method for calculating the amount of alkali added during the abnormal period after startup in an aluminum electrolytic cell according to claim 1, characterized in that, In step S8, the theoretical weight m of sodium carbonate to be added on the starting date, i.e., the (n+1)th day. Na2CO3加1 It is calculated using the following formula: Where, α 反 This represents the proportion of sodium carbonate obtained in step S5 that actually participated in the chemical reaction.

10. The method for calculating the amount of alkali added during the abnormal period after startup in an aluminum electrolytic cell according to claim 1, characterized in that, Stop adding alkali 75-85 days after starting the electrolytic cell to allow the molecular ratio to decrease naturally, and start adding aluminum fluoride 85-95 days after starting the cell to reduce the molecular ratio to the standard range of the normal period.

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