A method for optimizing and regulating a potassium extraction process from salt lake brine based on digital twinning

Abstract

This invention discloses an optimization and control method for potassium extraction from salt lake brine based on digital twins, comprising: deploying online sensors to collect process physical parameters in real time, and obtaining the real-time concentration of key ions based on the correlation inversion of the physical properties of the mixed electrolyte solution; establishing a digital twin virtual mirror model, and outputting the ion activity under the current operating conditions according to the real-time concentration and process physical parameters; calculating diagnostic indicators to characterize the current process operation status based on the comparison between ion activity and thermodynamic equilibrium state; obtaining the control quantity through closed-loop solution of material conservation, and distributing the control quantity to the DCS system for execution; this invention aims to overcome the problems of decreased conversion rate, pipeline salt blockage, and low potassium resource recovery rate caused by the lack of real-time process sensing and quantitative control methods in the potassium mixed salt conversion process and flotation scavenging process.

Description

Technical Field

[0001] This invention relates to the field of digital processing technology, and in particular to an optimized control method for potassium extraction from salt lake brine based on digital twins. Background Technology

[0002] Potassium sulfate is an indispensable potassium fertilizer in my country's agricultural production and plays a vital strategic role in ensuring food security. The mainstream process for extracting potassium sulfate from magnesium sulfate subtype salt lake brine is as follows: after the raw brine is graded, evaporated, and crystallized by sun-drying in salt fields, the potassium mixed salt undergoes a "first-stage conversion" to obtain soft potassium magnesium alum, which is then processed through flotation separation, washing, second-stage conversion, crystallization, and drying to obtain the potassium sulfate product. In recent years, with the deep integration of new-generation information technology and the salt lake chemical industry, salt lake enterprises have begun to explore technological paths for transforming from manual experience-based control to data-driven intelligent regulation. However, in the above-mentioned production process, the following two key processes have long been constrained by bottlenecks such as a lack of process sensing methods and reliance on manual experience for regulation: The first step is the potassium mixed salt conversion process. The core control objective of this process is to precisely maintain the liquid phase composition at Mg. 2+ -SO4 2- -The cosaturation point of potassium magnesium sulfate and esperidium salt in the H2O ternary aqueous salt system phase diagram is used to obtain the highest conversion rate of potassium magnesium sulfate. Traditional production methods rely entirely on manual sampling and testing at regular intervals to determine the Mg content. 2+ Concentration detection cycles can be as long as 2-4 hours. During this detection blind zone, operators cannot accurately determine the current operating conditions' position on the phase diagram and can only adjust the amount of mother liquor added based on experience, leading to inaccurate actual Mg concentrations. 2+ When the concentration frequently deviates significantly from the optimal value, the conversion rate of soft potassium magnesium sulfate decreases significantly. Secondly, the flotation scavenging process aims to recover effective potassium resources entrained in the tailings of the main flotation. However, in the feed pipeline of the scavenger in this process, the slurry is prone to crystallization of Erie salt due to supersaturation, which leads to frequent pipeline blockage. Traditional processes lack any online supersaturation monitoring methods and cannot predict the salt formation trend in the scavenging pipeline. Once the scavenger is started, it is quickly forced to stop due to salt formation, resulting in a large loss of effective potassium resources. Therefore, due to the lack of real-time process sensing and quantitative control methods in the two key processes mentioned above, it is difficult to improve the comprehensive recovery and utilization rate of potassium resources. There is an urgent need in this field for an optimized control method that can achieve real-time sensing, real-time diagnosis, and real-time control. Summary of the Invention

[0003] The present invention aims to solve the problems of decreased conversion rate, pipeline salt blockage, and low potassium resource recovery rate in the potassium mixed salt conversion process and flotation scavenging process in the prior art due to the lack of real-time process sensing and quantitative control methods.

[0004] To achieve the above objectives, this invention provides an optimization and control method for potassium extraction from salt lake brine based on digital twins, comprising the following steps: Step S1: Deploy online sensors at key process monitoring points in the potassium extraction process from salt lake brine to collect process physical parameters in real time, and obtain the real-time concentration of key ions based on the physical property correlation inversion of mixed electrolyte solution. Step S2: Establish a digital twin virtual mirror model of the key process. The digital twin virtual mirror model outputs the ion activity under the current operating conditions based on the real-time concentration and the process physical parameters. Step S3: In the digital twin virtual mirror model, based on the comparison between the ion activity and the thermodynamic equilibrium state, calculate the diagnostic indicators used to characterize the current process operation status. Step S4: Based on the values ​​of the diagnostic indicators, the control quantity is obtained through a closed-loop solution of material conservation, and the control quantity is sent to the DCS system for execution.

[0005] Compared with existing designs, the present invention has the following advantages: This invention utilizes three conventional industrial sensors—a density meter, a thermometer, and a conductivity meter—deployed in the outlet pipes of the conversion cell and the inlet pipes of the scavenger. Combined with an ion concentration inversion algorithm based on the correlation of physical properties of mixed electrolyte solutions, it enables the determination of Mg... 2+ and SO4 2- The second-level online monitoring of concentration eliminates the detection blind spot of 2-4 hours in traditional manual testing.

[0006] This invention transforms the traditional fuzzy operation, which relies on human experience for judgment, into a phase deviation index and a salt deposition risk index for the sweep pipeline by establishing a digital twin virtual mirror. This enables operators to grasp the position of the current operating condition in the phase diagram and the salt deposition risk level in real time and accurately.

[0007] This invention directly obtains the control quantity based on the values ​​of diagnostic indicators through a closed-loop solution of material conservation and sends it to the DCS system for execution. This achieves fully automated control with real-time sensing, real-time diagnosis, and real-time regulation, solving the problem of Mg conversion in the process. 2+ Significant concentration fluctuations leading to decreased conversion rates and frequent salt buildup and blockage in scavenging pipelines causing long-term shutdowns of scavenging machines have improved the overall recovery and utilization rate of potassium resources. Attached Figure Description

[0008] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same parts.

[0009] Figure 1This is a flowchart illustrating the optimized control method for potassium extraction from salt lake brine provided in this embodiment. Detailed Implementation

[0010] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0011] Example 1: The conventional potassium extraction process from salt lake brine is as follows: the raw brine is sun-dried on the salt flats, and then successively evaporated and crystallized in NaCl ponds, espresso ponds, potassium mixed salt ponds, and carnallite ponds. It is then mined by a water-dredging vessel. Carnallite is cold-decomposed to obtain KCl, and potassium mixed salt is converted to obtain soft potassium magnesium alum. KCl and soft potassium magnesium alum are then separated by flotation. Finally, potassium sulfate product is obtained by washing, two-stage conversion, crystallization, and centrifugal drying.

[0012] However, the potassium mixed salt conversion process relies entirely on manual sampling and testing at regular intervals to determine the Mg content due to traditional production methods. 2+ Concentration and detection cycles can be as long as 2 to 4 hours, making it impossible for operators to accurately grasp the current operating conditions on the phase diagram in real time. They can only adjust the amount of mother liquor added based on experience, leading to inaccurate actual Mg concentrations. 2+ The concentration often fluctuates significantly between 3.8% and 5.2%, frequently deviating from the optimal C point (the optimal C point refers to...). In the ternary aqueous salt system phase diagram, soft potassium magnesium alum With Laxative Salt (At the same time, the specific liquid phase composition point that reaches solid-liquid equilibrium is reached), the conversion rate of soft potassium magnesium alum decreases; Because traditional flotation scavenging processes lack any online supersaturation monitoring methods, it is impossible to predict the salt deposition trend in the scavenging pipeline. Once the scavenger is turned on, salt deposition and blockage frequently occur in the return pipeline, which seriously affects normal production and can only be stopped for a long time, resulting in the loss of effective potassium resources.

[0013] Therefore, this embodiment provides an optimization and control method for potassium extraction from salt lake brine based on digital twins. Please refer to [link to relevant documentation]. Figure 1 This method is applicable to real-time optimization and control scenarios in the potassium mixed salt conversion process and flotation scavenging process during the extraction of potassium sulfate from magnesium sulfate subtype salt lake brine. The method includes the following steps: Step S1: Deploy online sensors at key process monitoring points in the potassium extraction process from salt lake brine to collect process physical parameters in real time, and obtain the real-time concentration of key ions based on the physical property correlation inversion of mixed electrolyte solution. The key processes include the potassium mixed salt conversion process and the flotation scavenging process; The online sensors include: a first online sensor group deployed at the outlet of the conversion cell in the potassium mixed salt conversion process, and a second online sensor group deployed at the inlet pipeline of the scavenger in the flotation scavenging process; The first online sensor group includes a first density meter, a first thermometer, and a first conductivity meter, which are used to collect the density, temperature, and conductivity at the outlet of the conversion cell in real time, respectively. The second online sensor group includes a second density meter, a second thermometer, and a second conductivity meter, which are used to collect density, temperature, and conductivity at the inlet pipe of the scavenger in real time, respectively.

[0014] Due to Mg 2+ and SO4 2- It is a core ionic component in the transformation reaction process and in judging the risk of salt formation during scavenging. Its concentration directly determines the position of the current operating condition on the phase diagram and the degree of supersaturation of the solution relative to the target solid phase. Therefore, the real-time concentration of key ions, including Mg, is obtained. 2+ and SO4 2- The molality of is obtained by inversion using the following formula:

[0015]

[0016] in, Real-time conductivity data collected by either the first or second conductivity meter. The real-time temperature collected by the first or second thermometer. The real-time density is collected by the first or second density meter, and =1 or =2, when =1 corresponds to the potassium mixed salt conversion process, when When =2, it corresponds to the flotation sweeping process; The background conductivity of NaCl at the current temperature is obtained by multiplying the limiting molar conductivity of NaCl by the saturated molar concentration of NaCl at the current temperature. The limiting molar conductivity of NaCl refers to the conductivity per unit concentration of NaCl under infinite dilution conditions; it is a physical constant that depends only on temperature and can be found in physical chemistry handbooks or electrochemical data tables. A typical value at 25°C is 126.45 S·cm. 2 / mol; background conductivity of NaCl The reaction showed that Mg2+ and SO42- were removed from the brine system. 2- In addition, the contribution of the background electrolyte, mainly NaCl, to the total conductivity; Mg 2+ The limiting molar conductivity refers to the Mg 2+ The conductivity per unit concentration under infinite dilution conditions is a physical constant that depends only on temperature. According to a physical chemistry handbook, its typical value at 25°C is 106.12 S·cm. 2 / mol; The molar mass of MgSO4 The density of pure water at the current temperature can be found in the pure water property data table; and These are fixed combination coefficients derived from the partial molar volumes of each ion in the solution, used to convert density measurements into ion concentrations. Related Mg 2+ density contribution, Related SO4 2- The density contribution was obtained by linearly combining the partial molar volume data of each ion under infinite dilution conditions, reflecting the Mg content per unit mass molar concentration. 2+ or SO4 2- The increase in solution density.

[0017] The calculation principle of this inversion formula lies in decomposing the total conductivity of the solution into the sum of the independent contributions of each ion. After subtracting the background conductivity of NaCl, the remaining conductivity is mainly attributed to Mg. 2+ The contribution of Mg can be inferred from the conductivity. 2+ Concentration; simultaneously, utilizing the principle of volume addition of mixed electrolyte solutions, the solution density is decomposed into the superposition of the density of pure water and the partial molar volume contribution of each ion, given the known Mg... 2+ After concentration, subtract water and Mg from the total density. 2+ The remaining part is SO4. 2- The contribution of SO4, thus inferring its contribution. 2- Concentration; calculated Mg represents the Mg at the outlet of the conversion tank or the inlet pipe of the scavenger. 2+ molar concentration, SO4 at the outlet of the conversion tank or the inlet pipe of the scavenger 2- The molar concentration provides real-time ion concentration input for subsequent digital twin models, enabling online quantitative assessment of the primary conversion reaction process and the risk of scavenging and salt formation.

[0018] Step S2: Establish a digital twin virtual mirror model of the key process. The digital twin virtual mirror model outputs the ion activity under the current operating conditions based on the real-time concentration and process physical parameters. The process of establishing a digital twin virtual mirror model of key processes includes: Virtual mirror modules were constructed for the potassium mixed salt conversion process and the flotation scavenging process, respectively. The virtual mirror modules include an activity calculation submodule and a solid phase solubility submodule. The activity calculation submodule is based on the Pitzer electrolyte thermodynamic model, and the solid phase solubility submodule incorporates the solubility product constant of soft potassium magnesium alum. The solubility product constant of esperidone salt Each solubility product constant is provided by a preset database; the digital twin virtual mirror model is updated synchronously with the physical production line at a preset cycle; It should be noted that the construction of this digital twin virtual image model can be implemented using existing C / S architecture or OPC UA communication technology industrial software platforms, and this embodiment does not limit it. This digital twin virtual image model is used to construct a virtual mapping equivalent to the physical production line within a computer system, making the originally invisible ion concentration and activity data visible in real time, thereby solving the core blind spot problems of "the accurate position of the current operating condition on the phase diagram is unknown" and "whether the current supersaturation has reached the critical value for salt formation is unknown" in traditional methods.

[0019] The activity calculation submodule uses the Pitzer electrolyte thermodynamic model, which utilizes Mg 2+ molar concentration SO4 2- molar concentration Real-time temperature collected by the first or second thermometer Calculate Mg 2+ Real-time ion activity and SO4 2- Real-time ion activity :

[0020] in, Representative ion species: Mg 2+ or SO4 2- , Ionic strength, , ions The number of charges (Mg) 2+ Take +2, SO4 2- Take -2). The activity coefficient is calculated explicitly based on the current temperature and ionic strength, i.e., based on the Pitzer electrolyte thermodynamic model, using the current temperature. and ionic strength Substituting these terms into the Pitzer activity coefficient equation (including the Debye-Hückel long-range electrostatic term, the second virial coefficient term, and the third virial coefficient term), the Mg values ​​are obtained. 2+ and SO42- The activity coefficient value is a matter of existing technology and will not be described in detail in this embodiment.

[0021] Furthermore, in the solid-phase solubility submodule, the solubility product constant of soft potassium magnesium alum... This refers to the product of the activities of the constituent ions of potassium magnesia (K₂SO₄·MgSO₄·6H₂O) at a given temperature when it reaches dissolution equilibrium. Obtained from a thermodynamic database, it reflects the solubility limit of potassium magnesia at that temperature; the solubility product constant of esperidone. This refers to the dissolution equilibrium of esperidone (MgSO4·7H2O) at a given temperature, where Mg... 2+ Activity and SO4 2- The product of activities, obtained from a thermodynamic database, reflects the solubility limit of esperidone at that temperature.

[0022] In a preferred embodiment, the solubility product constant is corrected by the following formula:

[0023] in, To be at a known reference temperature (Usually, the standard solubility product constant of potassium magnesium sulfate or esperidone salt at 25°C is used.) The standard solubility product constant of the corrected potassium magnesium alum or esperidone salt is the temperature measured by the online thermometer, which is obtained by the formula. Standard enthalpy of solution represents the enthalpy change of a solid salt when dissolved in water under standard conditions. It reflects the thermal effect accompanying the dissolution process. A positive value indicates endothermic reaction, and a negative value indicates exothermic reaction. It can be found in a thermodynamic database. is the ideal gas constant.

[0024] It should be noted that the uncorrected standard solubility product constant is usually accurate only at a reference temperature (e.g., 25°C). However, the significant diurnal temperature variation at the salt lake site causes substantial changes in solubility due to temperature fluctuations. Therefore, correction is necessary. This correction formula establishes a linear relationship between the logarithm of the solubility product constant and the reciprocal of the absolute temperature, assuming that the standard enthalpy of solution remains approximately constant within the tested temperature range. Thus, only a known temperature is required for this correction. By combining the standard enthalpy of solution, the accurate solubility product value at any temperature can be calculated.

[0025] Step S3: Calculate diagnostic indicators to characterize the current process operation status based on the comparison between ion activity and thermodynamic equilibrium state in the digital twin virtual mirror model. When the digital twin virtual mirror model corresponds to the potassium mixed salt conversion process, the diagnostic indicators in step S3 include a phase inversion zone deviation index. :

[0026] in, and The activity values ​​of fixed ions corresponding to the cosaturation point of the phase diagram of soft potassium magnesium alum and esperidone salt in the potassium mixed salt conversion process; when When =1, it indicates that the current operating condition is at a common saturation point. >1 indicates Mg 2+ and SO4 2- The ion activity product is higher than that of the cosaturation point, and the system shifts towards the potassium mixed salt region; <1 indicates Mg 2+ and SO4 2- The ion activity product is lower than that of the cosaturation point, indicating incomplete conversion.

[0027] It should be noted that the co-saturation point of the phase diagram for potassium ferrous sulfate and esperidone salt refers to the liquid phase composition point at which both potassium ferrous sulfate and esperidone salt simultaneously reach solid-liquid equilibrium at the current operating temperature. Specifically, it is the intersection point of the boundaries between the potassium ferrous sulfate phase region and the esperidone salt phase region on the phase diagram at that temperature, directly determined from the phase diagram and expressed as a mass fraction or percentage. To fix the physical constants, they can be obtained by consulting the phase diagram handbook for this quaternary aqueous salt system. It should be noted that the phase diagram is a current technique, and usually only one experiment is needed within one cycle to determine the intersection point, and this cycle can be used continuously.

[0028] The ratio of the current actual ion activity product to the target cosaturation point activity product is calculated. When the ratio is exactly 1, it indicates that the operating conditions precisely fall at the thermodynamic critical point most favorable for the formation of soft potassium magnesium alum. A ratio greater than 1 indicates that the system has crossed the cosaturation line and entered the impurity precipitation region. A ratio less than 1 indicates that the system has not yet reached the optimal crystallization driving force. The final obtained phase inversion deviation index is... It reflects the direction and degree of deviation of the current operating condition from the optimal conversion point, providing a quantitative error signal for subsequent control.

[0029] When the digital twin virtual mirror model corresponds to the flotation sweeping process, the diagnostic indicators in step S3 include the salt accumulation risk index of the sweeping pipeline. :

[0030] in, Let be the solubility product constant of esperidone at the current temperature, when At that time, it was determined that they had entered a high-risk salt deposit area.

[0031] It should be noted that the supersaturation ratio of the solution is obtained by comparing the real-time ion activity product with the solubility product constant of Epsom salt. Subtracting 1 from this ratio yields the dimensionless supersaturation index. The reason for subtracting 1 in the formula is to ensure that the index has a critical threshold of 0. That is, when the solution is just saturated, the activity product equals the solubility product, the ratio is 1, and the index is 0, facilitating threshold judgment by the DCS system. The final obtained index is the salt deposition risk index for the scavenging pipeline. This reflects the degree of supersaturation of Epsom salt in the current scavenging slurry. The higher the value, the stronger the driving force for precipitation and crystallization, and the higher the risk of salt formation. Furthermore, crystals can only grow when the supersaturation ratio of the solution exceeds a critical value (i.e., the critical supersaturation ratio). For salt crystallization, the critical supersaturation ratio is usually between 1.15 and 1.20. In this embodiment, 1.15 is used as the safety threshold. When the index exceeds this threshold, it means that there is a significant spontaneous nucleation driving force, and salt formation is very likely to occur in the pipeline in a short time. Dilution intervention must be initiated immediately.

[0032] Step S4: Based on the values ​​of the diagnostic indicators, the control quantity is obtained through a closed-loop solution of material conservation, and the control quantity is sent to the DCS system for execution.

[0033] Among them, the control quantity obtained through the closed-loop solution of material conservation includes the flow rate of the mixed mother liquor added to the potassium mixed salt conversion process. Calculate using the following formula:

[0034] in, The flow rate of the potassium mixed salt slurry entering the conversion tank is measured by the first online flow meter. Mg for potassium mixed salt conversion process 2+ molar concentration, To fix ion activity values Mg obtained from conversion 2 + Molar concentration (i.e., through) (conversion) The mixed mother liquor Mg obtained through property correlation inversion 2+ Molar concentration; When a phase-shifting region deviates from the index When >1, the solution obtained If the value is positive, the flow rate of the mixed mother liquor will be automatically increased; if a phase inversion zone deviates from the index... When <1, the solution obtained If the value is negative, the flow rate of the mixed mother liquor will be automatically reduced.

[0035] It should be noted that in this embodiment, the conversion tank is considered as a steady-state mixer. After the two materials entering the tank (potassium mixed salt slurry and mixed mother liquor) are fully mixed, Mg2+ Total moles are conserved; let the target outlet concentration be... By listing the Mg in the material 2+ The instantaneous equilibrium equation is obtained and the required mother liquor flow rate is solved in closed form. ; The denominator of the formula Constantly positive (mother liquor Mg) 2+ (The concentration is always lower than the target value), therefore the molecules The sign directly determines The direction is indicated by a positive sign, which means that the mother liquor needs to be increased for dilution, and a negative sign, which means that the mother liquor needs to be reduced to allow the system to concentrate on its own.

[0036] Among them, the control quantity obtained through the closed-loop solution of material conservation includes the wash water flow rate added to the front end of the scavenging machine in the flotation scavenging process. :

[0037] Among them, the wash water flow rate added to the front end of the scavenging machine in the flotation scavenging process The trigger condition is >0.15; The flow rate of the slurry entering the scavenger is measured by a second online flow meter. Real-time density collected by the second density meter; when Stop adding wash water when the water level drops below 0.05.

[0038] It should be noted that, based on Mg before and after dilution 2+ and SO4 2- The principles of conservation of total moles and summation of solution volumes apply. Let the current supersaturation ratio be... Reduce it to a safe threshold (corresponding to an oversaturation ratio of 1.05, i.e.) The required amount of pure water to be added (below 0.05) is derived from the definition of supersaturation ratio and material balance; in the formula... The density ratio represents the dilution ratio corresponding to the relative solute mass that needs to be removed to eliminate supersaturation. The density ratio term is used to convert the flow rate from a mass basis to a volume basis, so that it can be directly used to control positive displacement pumps or regulating valves. The final mixed mother liquor flow rate and wash water flow The data is sent to the control terminal of the DCS system to complete the execution operation, thereby realizing real-time closed-loop optimization and control of the primary conversion process (potassium mixed salt conversion process) and the flotation scavenging process.

[0039] The method for optimizing and controlling the potassium extraction process from salt lake brine provided in this embodiment utilizes three conventional industrial sensors—a density meter, a thermometer, and a conductivity meter—deployed in the outlet of the conversion tank and the inlet pipeline of the scavenger. Combined with an ion concentration inversion algorithm based on the physical property correlation of mixed electrolyte solutions, this method achieves potassium extraction at extremely low hardware costs. 2+ and SO4 2- Online concentration monitoring completely eliminates the blind spot of traditional manual testing (2-4 hours). Simultaneously, by establishing a digital twin virtual image, the true ion activity in the concentrated salt system is determined. Furthermore, the operator's experience-based judgment is transformed into precise numerical diagnosis using two indicators: the first-phase-transformation zone deviation index and the salt deposition risk index in the sweep pipeline. Finally, commands are directly sent to the DCS system for execution via an interface, achieving real-time sensing, real-time diagnosis, and real-time control, thus solving the problem of Mg conversion in traditional processes. 2+ The problems of large concentration fluctuations leading to a decrease in conversion rate, and frequent salt buildup and blockage in the scavenging pipelines leading to long-term shutdown of the scavenging machine, have improved the overall recovery and utilization rate of potassium resources.

[0040] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for optimizing and controlling the potassium extraction process from salt lake brine based on digital twins, characterized in that, Includes the following steps: Step S1: Deploy online sensors at key process monitoring points in the potassium extraction process from salt lake brine to collect process physical parameters in real time, and obtain the real-time concentration of key ions based on the physical property correlation inversion of mixed electrolyte solution. Step S2: Establish a digital twin virtual mirror model of the key process. The digital twin virtual mirror model outputs the ion activity under the current operating conditions based on the real-time concentration and the process physical parameters. Step S3: In the digital twin virtual mirror model, based on the comparison between the ion activity and the thermodynamic equilibrium state, calculate the diagnostic indicators used to characterize the current process operation status. Step S4: Based on the values ​​of the diagnostic indicators, the control quantity is obtained through a closed-loop solution of material conservation, and the control quantity is sent to the DCS system for execution.

2. The method according to claim 1, characterized in that, The key processes include a potassium mixed salt conversion process and a flotation scavenging process; the online sensors include: a first online sensor group deployed at the outlet of the conversion cell in the potassium mixed salt conversion process, and a second online sensor group deployed at the inlet pipeline of the scavenging machine in the flotation scavenging process; The first online sensor group includes a first density meter, a first thermometer, and a first conductivity meter, which are used to collect the density, temperature, and conductivity at the outlet of the conversion cell in real time, respectively. The second online sensor group includes a second density meter, a second thermometer, and a second conductivity meter, which are used to collect the density, temperature, and conductivity at the inlet pipe of the scavenger in real time.

3. The method according to claim 2, characterized in that, The real-time concentration of the key ions obtained includes Mg 2+ and SO4 2- The molality of is obtained by inversion using the following formula: in, Real-time conductivity data collected by either the first or second conductivity meter. The real-time temperature collected by the first or second thermometer. The real-time density is collected by the first or second density meter, and =1 or =2, when =1 corresponds to the potassium mixed salt conversion process, when When =2, it corresponds to the flotation and sweeping process; The background conductivity of NaCl at the current temperature is obtained by multiplying the limiting molar conductivity of NaCl by the saturated molar concentration of NaCl at the current temperature. Mg 2+ The limiting molar conductivity, The molar mass of MgSO4 The density of pure water at the current temperature. and These are fixed combination coefficients derived from the partial molar volumes of each ion in the solution, used to convert density measurements into ion concentrations. Related Mg 2+ density contribution, Related SO4 2- Density contribution; Mg represents the Mg at the outlet of the conversion tank or the inlet pipe of the scavenger. 2+ molar concentration, SO4 at the outlet of the conversion tank or the inlet pipe of the scavenger 2- Molar concentration.

4. The method according to claim 3, characterized in that, The process of establishing a digital twin virtual mirror model of the key process includes: Virtual mirror modules are constructed for the potassium mixed salt conversion process and the flotation scavenging process, respectively. Each virtual mirror module includes an activity calculation submodule and a solid-phase solubility submodule. The activity calculation submodule is based on the Pitzer electrolyte thermodynamic model, and the solid-phase solubility submodule incorporates the solubility product constant of soft potassium magnesium alum. The solubility product constant of esperidone salt Each solubility product constant is provided by a preset database; the digital twin virtual mirror model is updated synchronously with the physical production line at a preset cycle; The process of outputting the ion activity under the current operating conditions includes: utilizing the Mg... 2+ molar concentration SO4 2- molar concentration and the real-time temperature collected by the first or second thermometer Calculate Mg 2+ Real-time ion activity and SO4 2- Real-time ion activity : in, Representative ion species: Mg 2+ or SO4 2- , Ionic strength, , ions The number of charges, The activity coefficient is calculated explicitly based on the current temperature and ionic strength.

5. The method according to claim 4, characterized in that, In the solid-phase solubility submodule, the solubility product constant of the soft potassium magnesium alum is... and the solubility product constant of the purpuric salt The correction is performed using the following formula: in, To be at a known reference temperature The standard solubility product constant of potassium magnesium alum or espresso salt. The corrected standard solubility product constant of potassium magnesium alum or espresso salt; For standard enthalpy of solution, is the ideal gas constant.

6. The method according to claim 4, characterized in that, When the digital twin virtual mirror model corresponds to the potassium mixed salt conversion process, the diagnostic indicators in step S3 include a phase inversion zone deviation index. : in, and The activity value of the fixed ion corresponding to the cosaturation point of the phase diagram of soft potassium magnesium alum and esperidone salt in the potassium mixed salt conversion process; when When =1, it indicates that the current operating condition is at the common saturation point. >1 indicates Mg 2+ and SO4 2- The ion activity product is higher than the cosaturation point, and the system shifts towards the potassium mixed salt region; <1 indicates Mg 2+ and SO4 2- The ion activity product is lower than the cosaturation point, indicating incomplete conversion.

7. The method according to claim 4, characterized in that, When the digital twin virtual mirror model corresponds to the flotation scavenging process, the diagnostic indicators in step S3 include the salt accumulation risk index of the scavenging pipeline. : in, Let be the solubility product constant of esperidone at the current temperature, when At that time, it was determined that they had entered a high-risk salt deposit area.

8. The method according to claim 6, characterized in that, The control quantity obtained through closed-loop solution of material conservation includes the flow rate of mixed mother liquor added to the potassium mixed salt conversion process. Calculate using the following formula: in, The flow rate of the potassium mixed salt slurry entering the conversion tank is measured by the first online flow meter. Mg for the potassium mixed salt conversion process 2+ molar concentration, The fixed ion activity value Mg obtained from conversion 2+ molar concentration, The mixed mother liquor Mg obtained through the aforementioned property correlation inversion 2+ Molar concentration; When the phase inversion zone deviates from the index When >1, the solution obtained If the value is positive, the flow rate of the mixed mother liquor will be automatically increased; if the first phase inversion zone deviates from the index... When <1, the solution obtained If the value is negative, the flow rate of the mixed mother liquor will be automatically reduced.

9. The method according to claim 7, characterized in that, In step S4, the control quantity obtained by solving the material conservation closed-loop equation includes the wash water flow rate added to the front end of the scavenger in the flotation scavenging process. : The wash water flow rate added to the front end of the scavenging machine in the flotation scavenging process is described above. The trigger condition is >0.15; The flow rate of the slurry entering the scavenger is measured by a second online flow meter. The real-time density collected by the second density meter; when Stop adding wash water when the water level drops below 0.

05.

10. The method according to claim 6, characterized in that, The cosaturation point of the phase diagram of potassium magnesium alum and esperidone salt is: the liquid phase composition point corresponding to the simultaneous solid-liquid equilibrium of potassium magnesium alum and esperidone salt at the current operating temperature.

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